Reason numero uno is that there is no rational connection between this community center and the terror attacks of 9/11. Protesting its construction is pretty much equivalent to protesting the construction of churches south of the Mason-Dixon line because the KKK used to lynch people down there. The protesters and pundits are committing the logical fallacy of the sweeping generalization: the 9/11 hijackers were Muslim, therefore all Muslims are potentially to be feared. This is an extremely dangerous attitude, and it brings me to…

Reason number two: I was raised Jewish. My temple Hebrew school curriculum devoted a full year to education on the dangers of bigotry, prejudice, and otherwise singling out any ethnic, racial, or religious group. Certainly, that education focused on the experiences of Jewish people, but the lessons we discussed were broadly applicable. I have internalized many of my experiences from growing up and living as a member of a cultural minority, and I respect the needs for other minorities to practice their beliefs and gather as a community. Such things should not be made unpleasant by the actions of the cultural majority. More than that, the cultural diversity of our country should be celebrated – it is what makes us great!

It’s very easy for hate speech to come out of this, as the protesters stir up emotions. After all, their entire argument is based on emotion: even when the pundits backpedal as hard as they can to avoid sounding bigoted, they end up calling the community center’s location things like “tasteless” – forgetting that, in this sense, “taste” varies from person to person and is based on emotional responses. Even such mild-seeming criticism can lead to prejudice and bigotry. Now, I’m certainly not saying that I think the United States is on a slippery slope to an imitation Holocaust. I don’t think that is true at all. But I know that pogroms and bigotry happened well before that, and what some of the protesters are saying while assembled in a mob near the Islamic center makes me nervous. As a Jew, when I say “never again,” I don’t just mean myself.

Reason Number Three is that I am an American. I am patriotic. I believe in the American system of government and American ideals. I also think about those ideals. The founders of this country were products of the Enlightenment and the internecine prejudices of Europe; they were wise enough to know that their new country should be established without a single state religion and with built-in acceptance of all the various faiths in all the original thirteen colonies. (Remember that, in those days, the various strains of Christianity were considered as disparate and irreconcilable as Hinduism and Judaism. The colonists came from a Europe that periodically tore itself to pieces over differences between Catholic and Protestant groups – and that was between faiths that agree on basic things like who’s a god and who isn’t!) If the framers of our Constitution had wanted America to be a Christian nation, I’d think they would want to be much more obvious about it, to make sure that their intentions were clear as time passed: while Judeo-Christian philosophy certainly influenced the Constitution, that document contains exactly zero references to God, Jesus, or Christianity.Nor does it refer to any other religion.

Even a general lack of endorsement of one religion over another wasn’t enough for the newly founded states, though. Think back to high school history classes: the states refused to ratify the Constitution before the inclusion of a Bill of Rights, and the very first amendment that they demanded specifically prohibits the federal government from establishing a state religion. Not only that, but it grants individuals the right to practice any religion they like, and to assemble together for any purpose, including practice of religion. So not only is the community building this Islamic center well within their rights to do so, but we ought to celebrate what they are doing – they are exercising rights that do not exist in many countries but that we, as Americans, gladly extend to our citizens. We ought to give thanks to the founders of our country and the legislatures of the original thirteen colonies for giving us so many rights, rather than protesting the exercise of these Constitutional rights!

As a final note, let me mention that other supporters of the community center include the mayor of New York City and the families of 9/11 victims. You know, the people actually affected by the presence of the community center, and the people most likely to have a negative emotional response to it. The pundits on Fox News are using the Islamic center as a political football to try and drum up support for reactionary candidates, and I think they ought to be ashamed of their actions. Not only do they come across as prejudiced, but they seem very un-American to me. Of course, this is America – so they can keep right on saying what they’re saying. That’s one of the sticky points about any debate like this. At the very least, though, I can hope that with all the information available out there, the general populace will think critically about what’s going on before succumbing to emotional reactions.

Thanks to magnetometer measurements and images from the Galileo mission, it’s pretty much established at this point that Europa has an icy outer shell over a global liquid ocean, with a rocky core on the inside.^* The only question is how thick that ice shell is – I’ve read estimates ranging from 10 meters to 100 kilometers, with a pretty high confidence of ones to tens of kilometers. The ice shell gives rise to a number of interesting surface features. A particularly cool sort of feature, found with global extent across Europa, is the double ridge.

A prominent double-ridge feature on Europa, most likely a crack in the icy shell

Planetary scientists have a number of models for how these double ridges form, and they generally seem to agree that the ridges mark the locations of cracks in the ice crust. One especially well-established model suggests that these cracks occur when Jupiter raises tides in Europa’s ocean – just like how the Moon raises tides in terrestrial oceans, but much stronger, because Jupiter is frakking huge compared to Earth’s moon. Europa’s ice crust bulges out over the ocean’s tidal swell and then cracks under the incredible stress. (I like to take a moment to think about the mindbogglingness of that statement: the whole moon’s surface cracks. I’ve stood on a frozen pond when a crack pings through the foot or so of ice on top of the water – Just imagine standing on Europa when this happens!) Once a crack forms, the tides don’t go away. As Europa rotates, about once every three and a half Earth days, the tides periodically lever these cracks apart and squeeze them back together again. In this model, every time the cracks gape open the subsurface ocean gets exposed to space. The surface water boils and rapidly crusts over with ice, and when the cracks get smushed closed, all this ice gets crushed up and forced to the top and bottom of the crack, forming the ridges. The ridges appear in pairs because the crack opens up again after that. These double-ridge features are mounds of crushed ice flanking passages into Europa’s ocean!^†

Dr. Richard Greenberg is a planetary scientist who thinks that these cracks in the ice shell might be potential sites for life to take hold. Unlike the rest of the subsurface ocean, they get exposed to sunlight, which means that photosynthesis could take place. The periodic in-and-out forcing of the crack would also drive strong currents, which is another energy source Europan life could use. (Those aren’t the only energy sources: other possibilities include thermal gradients in the water, volcanic vents on the ocean floor, or even induction as Europa travels through the Jovian magnetic field.) Of course, that life would also have to adapt to the crack opening and closing once every 3 1/2 Earth days!^‡

Europa's possible ice-fissure biosphere (from New Scientist; click for full article)

We do at least know, from the Galileo mission, that these cracks often have accompanying veneers of organic (e.g. carbon-based) molecules and salts splashed onto the ice surface. This is why the cracks appear as brown stripes in large-scale context images. The crack/veneer combination suggests that there are organic molecules and salts in the Europan ocean, and that those compounds get pumped to the surface through these cracks.

So, let’s take stock: Europa is the only extraterrestrial world with a global liquid water ocean, there is a definite possibility for life in that ocean, and these double-ridged cracks are a possible gateway into the alien biosphere.

Well, then, let’s go diving! Read on for my concept system architecture for an ambitious Europan ocean-exploring mission, which I call the Ice Fracture Explorer.

The Ice Fracture Explorer, or IFE, would be a combination lander/penetrator vehicle that I imagine to be a little smaller than the size of one of the MER rovers. Ideally, several IFEs would accompany an orbiter to Europa. The orbiter component of the mission would contain instruments designed to give the planetary scientists on the mission enough information to select a few double-ridged cracks that are actively being worked open and shut by tides. The flight controllers would then dispatch an IFE to each of those cracks.

Soft landing on a double ridge interior

The IFE includes thrusters and landing pads to make a soft landing on the surface. Europa’s surface gravity is less than half of Mars’, so a soft landing should be easier than the successful Viking or Pheonix missions, even without the benefit of a parachute. The IFE landers would target the inside-facing slopes of the double ridges, as shown above. Each vehicle also includes cameras and instruments, and the IFE will pause on the inside of the double ridges to relay data back to Earth.

The goal of these images are to verify that the crack is opening and closing each tidal cycle, and to establish the timing of the cycle. Once the cycle is known, flight controllers will uplink commands to the IFE to begin the second phase of the mission.

The IFE will wait until the crack is closed, and then separate form the landing legs and inflate some gas-bladder cushions, causing the vehicle to roll down towards the center of the double ridge. Using its thrusters for attitude adjustment, the IFE will right itself, centered over the crack.

Bouncing on air bags

At this point, the gas cushions would deflate. Since the IFE has to operate in the middle of the double ridge, I imagine it will need to run off an RTG power supply instead of solar panels.

After righting itself, the spacecraft deflates the air bags

Next, the IFE would fire projectiles into the crushed-ice ridges on either side of the vehicle. These projectiles could be barbed, contain chemical flash heaters, or anything else design to make them really stick into the ice, because they would be the anchors for twin tether lines that unreel from the spacecraft. The IFE would also deploy a high-gain antenna for communicating with the orbiter overhead, since the mission will have to happen very quickly from this point on.

Anchored to the walls, and antenna deployed

Now, the spacecraft waits. Inside the IFE, the tethers would be mounted so that they unreel in unison. When the ice crack opens up again, the tether cables will support the IFE above the center of the crack.

The mechanism pays out both cables at the same rate

As Jupiter rises overhead wobbles around zenith, its tides will pull apart the two sides of the ice fracture. The IFE will be suspended in the middle as the crack opens, with nothing below it until the ocean 1-10 km down! At this point, the IFE will drop its deflated cushions and begin to deploy a smaller penetrator vehicle from its underside. The penetrator is a small, two-stage vehicle with two instrument packages, a hard-shell body, and a data line connecting it to the IFE’s main bus.

Hanging over the abyss

The IFE would drop the penetrator, letting gravity take it down into the fracture. As it falls, the penetrator will photograph the fracture walls in visible and infrared light. Data will be rapidly carried up the line to the main bus hanging overhead, which will relay the images to the orbiter

Eventually, the penetrator would hit the ocean surface. The water would have iced over, but the weighted penetrator with its reinforced lower body would smash through the ice and reach the liquid water below. At that point, a buoyant surface instrument package would separate from the lower penetrator, which would continue down into the water. The surface instruments would try to identify any interesting chemistry or biology occurring at the water surface, where photosynthesis might take place. The lower body of the penetrator would simply try to go as far down as it can, illuminating the depths and taking pictures.

The IFE drops two instrument packages, one that stops just under the surface and one that goes as far down as possible

The IFE will have perhaps less than one quarter of a Europa day to operate. When the crack closes, it will be crushed inside unless something exceptionally lucky happens or the ice shell turns out to be very, very thin. One possible mission design might call for the IFE main bus to reel in the tethers when the crack closes in an attempt to survive for a second day, but the penetrators will likely be lost.

If the Europan ice shell is indeed hundreds of kilometers thick, then a data line might not be the best solution for penetrator-to-main-bus communication. I don’t think radio or laser communication would work well across the water/vacuum interface, though. In that case, one possible mission profile might be to wait for the crack to start closing, when the water level inside the crack might be squeezed up towards the surface. However, there would likely be much less data available.

Finally, since the IFE would be crushed inside the fracture as it closes, it will have to relay all its data to the orbiter before it loses communications capability. The orbiter would have to be timed to be overhead for the IFE to relay all its data – perhaps in an eccentric orbit that spends the entire quarter-day over the crack, or maybe just coming into communications range of the IFE during its last moments, so the IFE can dump its entire data store and then beam images out as it can before it gets squished.

All this discussion highlights one fact: Europa is a unique challenge. Though it is one of the very few places in the Solar System that we can imagine harboring life, the mission design to explore the Europan biosphere is very difficult and requires many stretches of space technology. The requirements analysis and detailed design of such a mission would take a great deal of innovation and effort. Those are challenges that I would love to see the space program address, though – because the discovery of extraterrestrial life would have a profound impact on our science and society. Diving into the cracks in Europa’s icy shell may be our best bet at making such a discovery!

* See, e.g.: Zimmer, C., Khurana, K. K., and Kivelson, M. G. Subsurface oceans on Europa and Callisto: constraints from Galileo magnetometer observations. Icarus vol. 147, p. 329–347 (2000)

† For more information on cracks in Europa’s icy surface, check out:

• Greenberg, R., and Geissler, P., Europa’s dynamic icy crust. Meteoritics and Planetary Science, vol. 33, p. 1685-1710. 2002.
• Greenberg, R., Hoppa, G., Bart, G., and Hurford, T.,Tidal stress patterns on Europa’s crust. Celestial Mechanics & Dynamical Astronomy, vol. 87, p. 171-188. 2003.
• Greenberg, R., Geissler, P., Hoppa, G., and Tufts, B. Tidal-tectonic processes and their implications for the character of Europa’s icy crust. Reviews of Geophysics, vol. 40, Art. No. 1004. 2002.
• Aydin A. Failure modes of the lineaments on Jupiter’s moon, Europa: Implications for the evolution of its icy crust. Journal of Structural Geology, vol. 28, p. 2222-2236. 2006.

‡ A couple cool articles on potential Europan biospheres are:

• Greenberg, R., Geissler, P., Tufts, B.R., and Hoppa, G.V., Habiltability of Europa’s crust: The role of tidal-tectonic processes. Journal of Geophysical Research, vol. 105, p. 17,551-17,562. 2000.
• Greenberg, R. Tides and the biosphere of Europa. American Scientist, vol. 89, p. 48-55. 2002.
• Chyba, C.F. and Hand, K.P. Life without photosynthesis. Science, vol. 292, p. 2026-2027. 2001.
• Schulze-Makuch, D. and Irwin, L.N. Energy cycling and hypothetical organisms in Europa’s ocean. Astrobiology, vol. 2, p. 105-121. 2002

I spent last week in Toronto at the annual AIAA Guidance, Navigation, and Control Conference. This is a huuuuuuuuuuge conference of engineers from academia, military, and industry all presenting papers about their research. So, I got to see a lot of Powerpoint presentations. (Okay, okay, supernerds, there were some PDFs and Keynotes. But “Powerpoint” is pretty much like “Kleenex” these days.) And an awful lot of the presentation slides I saw looked something like this:

Fine, right? I mean, this is a technical venue, full of super-brainy engineers. We want the facts, ma’am, just the facts, in all their glorious mathematical detail, and style means nothing. Right?

WRONG!

The first rule anyone will ever tell you about giving any kind of presentation is to know your audience. And if I’m in the audience at a conference like this, then I’m spending a full day listening to technical talks and you have only twenty minutes to make me think that your research is as cool, interesting, or relevant as the title made it sound when I picked it out of the lineup that morning. Because I’m still holding the conference program in my hand, and I have a notepad and pen ready to jot down research ideas the last cool presentation made me think of, and I might have my laptop in my bag, so I’m not at a loss for things to do if you’re not very exciting. In other words, not only do you need to convey your technical material, but you also need to keep me interested and/or entertained, at least enough to keep me listening to your technical stuff.

It’s a tall order.

I’ve been told that I do a good presentation, though, so I’m going to share a bit of my philosophy for what a technical presentation should be like. Here are the points that I start from:

1. Nobody wants to see lots of equations. Some are necessary, sure, and they can be a great way to add technical gravitas, but a 20-minute presentation is a much better time to show off results, pictures, movies, hypotheses, conclusions, possibilities, tricks, and excitement. And if the conference is like GNC, requiring a paper with each presentation, then all the equations go in there, anyways. The oral presentation is for highlights, not derivations.
2. These presentations come in the middle of a solid block of otherwise identical presentations that are going to blur together in the audience’s minds. So, they need to be distinctive. In other words, a bit of flash and polish goes a long way. Also, attention-grabby things like pictures and movies are good, but not if they’re just thrown together in a clip-art sort of way. (There’s good attention to grab, and bad attention to grab!)
3. Slides are visual aids. I mean both “visual” and “aids.” Think about both of those terms: slides are supposed to be for showing the audience things. And the slides in a live presentation are not supposed to be completely independent of the presenter: you should refer to them, but you are the one giving the presentation.

As an example of my own style, allow me to go through my recent GNC presentation slides and point out my thoughts on their layout, style, and content. If you want to follow along, most of the presentation itself is here on YouTube:

General Style

I think slides should be spartan. It’s not just that I’ve been lately trending towards minimalism in design – but it also bears thinking about exactly what information you think is important before you put it on a slide. The pictures, equations, and bullet points you select should be put on the slide to draw attention to them, and the slide should not include all sorts of accoutrements and fancy design stuff that distract from the actual content. I like to start all my slides from a “blank” template, and view them as an empty space which I can use to set off the things I want to talk about rather than trying to fill them with content. In general, I like to make slides that don’t include any extraneous information. (For example, everyone in the audience already knows what conference they are attending and what the date is. Not including the standard Powerpoint footer bar could buy you about 10% more slide space to work with.)

There are some things that technical audiences expect to see on each slide, and I’m willing to make some concessions here. For instance, many people expect some indications showing where this slide fits into the presentation, such as slide numbers. This serves two purposes: first, to give the audience a sense of how the “story” is progressing; and second, to give them something to refer to during the Q&A after a presentation. I also think it’s good to include some mark on each slide identifying yourself, such as a university logo or whatnot, because that helps drive home your technical “street cred.”

Finally, for years I have strongly favored dark backgrounds and light text or graphics. I do so for a simple reason: when projected against a wall in a dark room, light colors can look especially bright and sometimes seem to glow a little. Take an example with 100% black and white backgrounds and text, and with the same glow filter applied to the white parts. Clearly, the text in the top half of the image is not 100% black any more:

Which looks clearer? Which text stands out more?

There are two ancillary bonus features for me in going to a white text/black background scheme. One is that I talk about space, and it helps to make my slides more space-y. Two is that not many people go for a black background, so it helps to make my presentations more distinctive, standing out in the audience’s minds. (Three presentations from my research group were the only ones I saw at GNC that had a black background.)

Title Slides

I think of the title slide as my opportunity to anchor my audience with my premise, and my last chance to catch someone wandering from session to session. So I want flashy stuff, and I want that stuff to connect with my title in such a way that it gives the audience some more insight into what my title keywords mean.

So, here, I have my paper title, authors, and affiliations, but I leave off the name of the conference, session title, date, or any other text. The title slide is not the place to make a point, and again, I presume my audience already knows where they are. My graphic, showing a modular spacecraft in various stages of unfolding, hints at what I mean when my title says “multibody spacecraft reconfiguration,” and the view of Saturn is just plain cool – and hints a little that I’m thinking about far-flung applications.

Here’s another thing I don’t do on my title slides: I don’t start my presentation by saying, “Hi, I’m Joseph Shoer, and I will be presenting on Simulation of Multibody Spacecraft Simulation through Sequential Dynamic Equilibria.” Why? Because my session chair just introduced me with exactly those words. I don’t need to repeat, and I don’t need to read off the slide – presumably my audience can do that for themselves. I say, “Thank you for the introduction,” and then I start right in.

Outline Slides

Engage rant mode!

The vast majority of technical presentations I’ve seen include an “outline” or “agenda” slide. In general: I hate them.

I hate outline slides because they either convey no information I didn’t know already, or they convey very specific information that is entirely out of context and so I don’t understand it yet. Either way, they are a waste of time. In a 10-, 15-, or 20-minute presentation, saving thirty seconds to a minute can be quite important.

The outline slides that convey no new information have a bullet list that says something like Introduction, Background, Methods, Data, Results, Conclusions. You know, some variation on the standard lab report headings. If I’m listening to a presentation, I already know that you’re going to have an introduction and conclusion, and I already know that there’s going to be some kind of content in the middle. And if I’m at a technical presentation, then I already know that the middle sections involve explaining some experiment or model, looking at data, and extracting results. On top of the slide itself, one rule of presenting is that the speaker should talk about everything that appears on the slide. I don’t need the presenter to take the time to say things like, “At the end of my talk, I will conclude with some…conclusions.”

The other kind of outline slide, the one that the audience cannot understand, is the kind that tries to circumvent the lab-report headings by substituting in much more study-specific technical terms. This puts the speaker in a dilemma: if they just read the outline points, the audience won’t understand them. On the other hand, if they take the time to explain what each point means, they will end up repeating their presentation. Even if they do this well (and it’s my opinion that a well-done introduction should be solid enough to make such an additional “preview” unnecessary), there’s usually not much later on in the presentation to connect things back to the outline that ostensibly let the audience know the lay of the land. It’s like seeing the map for a road trip only once, before you get in the car, and then never again.

So: either the outline tells the audience that a presentation has the usual sections, or it tells them something that they’ll forget a slide or two later. In both cases, it’s a waste of time.

(Disclaimer: I have seen outline slides done well. In those cases the outline usually substitutes for the introduction. But they are so, so, so incredibly rare that I’m more than happy advocating the complete omission of outline slides.)

Slide Design and Layout

Here’s a typical slide I displayed.

I had four common elements on each slide:

• The Cornell seal and name of my lab, for branding.
• A brief list of the major sections of my presentation, with the current section highlighted. I find that this is very effective at letting the audience know where I am in my presentation and where I plan on going. It’s much more effective than, for example, a total slide count or a leading “outline” slide.
• A slide title. I go back and forth on whether this is necessary, given the moving highlighting in the section list above.
• A slide number.

The rest of the slide – and it’s quite a big area – is for content. And, in this case, I used that whole area for one thing. It’s certainly a spectacular picture, but I used this as a jumping-off point to talk about the Space Station and how it illustrates more than one application of spacecraft reconfiguration, the subject of my talk. It also illustrates the shortcomings of reconfiguration as implemented nowadays, since the Station’s robot arm is restricted to moving incredibly slowly.

You can see with this one how the black background helps with the space motif. It’s well worth the effort of color-inverting all my plots!

Often, I still end up needing to put a list on the screen. But a bullet list is not often the most desirable or effective way to do this. I have heard and read a number of designers who rail against bullet lists, and I agree with their reasoning: putting points in vertical order implies that each bullet is equivalent in some way, giving the points a parallelism that often doesn’t exist. (Check out the made-up example slide I led off with. Each bullet has a different kind of content. The bullet texts are not even the same type of phrase!) A list also implies some kind of order or hierarchy: the audience will read from top to bottom, making the first and last items in the list stand out.

Here’s the way I did it:

I put each list element in a little box, because they are separate concepts. The boxes also help me set off each item from the other items, making their mis-alignment very obvious. The message I was going for: this is a collection of concepts; they have something to do with each other by virtue of appearing on the same slide, but they are not arranged in list order and aren’t necessarily the same “level” of idea. I also went with a graphic, floating in space over the black background, that connects with several of those concepts. Below is another example, but this time I separated out the elements by color to imply some additional grouping.

Technical Content Slides

Of course, this presentation isn’t all for entertainment. (I estimate a good mix might be 1 part entertainment per 2-3 parts science and engineering for a technical conference. Contrast with a general-interest lecture, or what people like Neil deGrasse Tyson, Carl Sagan, Phil Plait, etc do.) But being engaging and understandable and conveying rigorous technical content are not mutually exclusive! Take this example:

I was explaining the Udwadia-Kalaba method for generating equations of constrained motion. One way to represent kinematic constraints, visually, is that a point representing a system has to move along a surface – which gave me a great way to use the slide as a visual aid to explain the concept. I think this would make for much faster understanding by the audience than spamming equations, too, because I get to say “the system has to move in a way consistent with the constraints” without having to explain all the terms in an equation. Still, it’s a complex slide with a lot of parts to explain, so I used the animation features in Powerpoint (simple fade-ins, nothing fancy, as a rule!) to bring them in a few at a time and explain them in sequence. Using the animations is also useful to me, in that it reminds me to explain everything on the slide and reminds me of the presentation order I decided. I knew I’d be presenting on my own laptop, so I didn’t have to worry about the animations porting over – in the past, I’ve used the trick of making each step in the animation a separate slide to make sure things go smoothly.

I do have the equation there, of course. And I took the time to point out all the important terms. But that doesn’t mean that this slide isn’t pretty! I saw many slides at the conference with similar content, but in Powerpoint bullet-list form.

Results Slides

Of course, the reason to give a presentation like this is to highlight some results. Often, this means graphs. Those results should be displayed as big and easy to read as possible. The black background helps for making things stand out, but there are certain necessities: big fonts and axis labels, in particular.

My favorite way to display results, though, is with movies. I mean, I’m talking about spacecraft made of modules that all slide and swing around each other to morph the whole spacecraft. I could make that extremely dry, but a good way to demonstrate that I’ve developed these algorithms and that they handle control of reconfigurable systems is to show it working. But it’s important to spend the time to put a polished movie together, to integrate it with the rest of the presentation, and to be familiar with its technical content so that I can use the movie to demonstrate my technical points. (Once again: visual aid.)

Believe me, engineers are suckers for cool movies. YouTube has a lot of hits for robotics research, for instance.

Miscellania

Contrast

Making the presentation easy to read is especially important, and it’s worthwhile to keep in mind that reading off a screen and from a projection are different. On your monitor, with light beaming out towards your face, it’s sometimes worth it to use low-contrast settings to keep things easy on the eyes. But on a projection in a dim – not dark – room, it’s better to make everything stand out.

I like to stick to a pretty small color palette, with the exception of photos and movies, which look more natural. For high contrast against black, I used a lot of white, light grays for accents, green, yellow, and cyan. (Blue and red – 0,0,1 and 1,0,0 – on black are bad ideas.  They can easily wash out in a dim room.) Color is a way to convey information, and if I don’t need that information, then I try to keep things black and white.

Fonts

As with colors and contrast, the key thing with fonts is to keep them easy to read. The presentation slides I’ve been pasting use a combination of Eras Medium for headings, Candara for the section highlight bar, and Segoe for text. All of those are sans-serif fonts with easily discernible characters. I could simply have used Arial or Calibri, but I chose to break from the defaults as just another way to say, “my presentation is different from all the others you’ve seen!”

Section Breaks

I have come to like placing minor-heading slides between the major sections of my presentation. Again, that’s a way to keep the audience in the loop about where the presentation is going. But I like them for an even more important reason, which is that they help remind me about the transitions!

Slide Counts

I’ve heard a number of heuristics for how many slides should be in a presentation. Ten total, or one per minute, and the like. It’s hard for me to come up with a reasonable heuristic for myself, though, because I tend to simplify my slides a lot, meaning that there are more of them but I go through them faster. I ended up with 33 slides, presented in 20-25 minutes, at GNC, but about five of those were heading slides and there were a few groups of 2-3 slides that expounded the same concept, so “one concept per minute” might work to describe my style.

Other Stuff

I always include an acknowledgment slide, because research is not usually done alone.

I also like to end my presentations with a repeat of my title slide (though I added in my group’s web site address), which lets the audience connect the graphic they first saw with the context of the rest of my presentation and reminds them who I am, where I’m from, and the title of my paper in case they want to look it up later.

In addition, I keep a bunch of backup slides on hand. Since my presentation style focuses on giving highlights, it’s entirely possible that I’ll get questions about the details; so, I make up a bunch of slides (or paste in from previous presentations) about my prior work or specific details, especially if I can anticipate what questions the audience will ask. If I use the backup slides, I get to look especially well-prepared!

Powerpoint contains this neat feature that lets you make slide templates (in Powerpoint 2007, look for “View Master” under the “View” ribbon). I get a lot of leverage out of the master template slides to get a consistent theme for my titles, headings, and content slides. Slide masters are also an easy way to get the section highlighting in the mini-outline in my header to work without lots of headachy monkeying around with tons of colors and styles on each slide individually. I typically base all my masters on the “blank” template, without any automatically-generated text box placeholders, so I can look at each slide as an empty canvas.

That’s All

Okay, I’ll get off my soapbox now. Maybe I will make some of my Powerpoint presentation templates available. My goals are both clarity in conveying content and engagement of the audience. I try not to sacrifice too much for one or the other, and have ended up at a distinctive, minimalist style. From the feedback I’ve received, it’s generally successful.

I have to give a bit of a shout-out here to the Williams College Physics department, which requires its research students to do a lot of presentations. Those prepared me very well for grad school. There’s also an incident that stands out in my mind in which physics profs Daniel Aalberts and Dwight Whitaker did a joint physics colloquium in which they (intentionally) demonstrated everything that a presenter could do wrong. If I ever am in a position to teach students about presentations, I’d love to play with that!

I hand-coded, from scratch, a multibody dynamics simulation package for Matlab.

This was for my research on treating reconfigurable spacecraft as kinematic mechanisms. We’re looking at how a modular spacecraft with joints (hinges, sliding surfaces, etc) between modules could twist itself around to rearrange itself. The idea is that changing the spacecraft’s shape could also change its functionality at a system level. Right now, proposals to do this involve having all the modules split off from one another, dodge around each other, and re-connect. Our thought is that the joints – the system’s kinematics, in engineering parlance – could dictate the motion in a desirable way. When modules come near one another, they can latch up and engage new joints, then twist around yet again. And again, and again, and again…until the whole system reaches the configuration we want.

In order to do numerical studies of the behavior of such a system, we needed a way to simulate multibody dynamics. We also needed the ability to explicitly control the kinematics of the system during simulation. And, since we don’t necessarily know conditions on the positions and orientations of all these modules (that’s what we’d like to discover!), we wanted tools based on a singularity-free representation such as quaternions. With few university licenses fitting that bill to play with, and surprisingly few relevant hits in the Matlab file exchange for multibody dynamics, I decided to write my own.

I call it QuIRK, which ostensibly stands for Quaternion-state Interface for Rigid-body Kinetics, but mostly I just like the name. (I was actually going for “clockwork,” but couldn’t get the “clo” to happen!)

This thing is pretty remarkably capable for a hand-coded multibody dynamics package. Once I had the toolbox functions, for instance, I produced this movie of a crazy lightly damped double-pendulum jouncing around with only twelve function calls. That’s twelve from Matlab startup to having the movie file as you see it.

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Pretty neat, huh?

I wrote up extensive online documentation for my functions and put the whole thing available for download here: www.spacecraftresearch.com/flux/quirk. And, if you’re the sort of person who goes to the AIAA Guidance, Navigation, and Control Conference, I will presenting our research application of this dynamics simulator package there!

Mysterious craters on Mars

I’m shamelessly bouncing all you readers over to the Bad Astronomy blog for this post, which is a great outline of the detective process that is planetary geology. It’s also a great illustration of how much context matters and how leaping to conclusions is…bad. AND it’s a good demonstration that, when there are several hypotheses in consideration, elements of each could be synthesized into the proper conclusion.

All things for us to keep in mind, in science and in everyday life!

(Also, way cool pictures that are reminders of TOTALLY AWESOME events in the past!)

A possible near-future space fighter radiating excess heat between battles

I think that extrapolating or projecting space battle technologies forward in time is a difficult thing to do, even for the cleverest science fiction geeks. I say this for two reasons: first, aside from some general trends, it’s hard to predict exactly where technology will go in the next ten or twenty or fifty years; second, nobody gets to play this game against a live opponent – and that’s really how combat tactics and technology develop. Still, given the trends, it’s fun to speculate! Physics won’t change radically for quite some time, so we have some direction in which to proceed.

I’m going to proceed from the assumption that “spacecraft” are different from launch and reentry vehicles. Let’s take some possible combat spacecraft systems, think about the related problems that spacecraft engineers try to solve, and see what might (!) happen if the aliens wait till we have some operational space colonies before they invade…

(By no means, of course, is this an exhaustive list, nor have I projected out as far as is possible. That would take about a think tank more than one sci-fi geek spacecraft engineer physicist blogger!)

Propulsion

This is the captain. We have a…little problem with our engine sequence, so we may experience some slight turbulence, and then…explode.

-Captain Malcolm “Mal” Reynolds

One of the challenges in propulsion technology today is that engineers typically face a choice: we can give our spacecraft powerful engines or energy-efficient engines, but not engines that are both at the same time. The powerful engines are things like chemical rockets, which are great for high-thrust things like boosting out of planetary gravity wells or for rapid maneuvers. The efficient engines are ion engines. These engines aren’t good for strong thrusting or rapid maneuvers, but they’re wonderful for speeding up long trajectories like going between planets. So, until the discovery of some new physics, combat spacecraft would probably have both: interplanetary cruise engines and combat maneuvering thrusters. The cruise engines would be of the highly efficient variety, used to break or enter planetary orbits and accelerate the spacecraft along transfer trajectories. The combat thrusters would be high-thrust engines designed to handle rapid maneuvering.

Right now, there’s a lot of research into the propulsion technologies that could be used as interplanetary cruise engines. This research includes solar sails, ion engines, and the VASIMR engine. (VASIMR will soon be flying up to the Space Station for tests and is the engine NASA Administrator Charlie Bolden was talking about when he mentioned proposed NASA tech research programs taking us to Mars in a few months instead of years.) There are also orbital maneuvers a spacecraft can do if it can interact with planets electromagnetically or gravitationally. Those techniques, however, are better at making interplanetary trajectories more energy-efficient than they are at making rapid course corrections or accelerating a spacecraft in a short period of time.

A possible next step could be nuclear rockets, but one of the most transformative propulsion technologies on the horizon would be a matter-antimatter annihilation engine – using the most efficient way possible to convert mass into energy. Physicists – including me, in an undergrad physics lab - have been creating and using antimatter on a particle-by-particle basis for decades. (This is easy: some radioactive decay processes produce positrons.) But if we learn to produce and store large quantities of antimatter, we will have at our disposal the most powerful rocket propellant in the known universe. Antimatter-fueled engines would allow truly relativistic spacecraft. While the stars would still be years away (to planetbound observers), making any interstellar trips substantial endeavors, our Solar System might be only weeks across. In addition, spacecraft with such powerful engines could execute extremely high-thrust maneuvers. Such propulsion systems would also provide plenty of surplus power with which to run other systems and charge batteries. And antimatter rockets would give space fighters an extremely powerful weapon: their own exhaust! This sort of engine, and its weaponization, appears fairly regularly in fiction. For example, the climax of Poul Anderson’s novel Harvest of Stars describes two antimatter-fueled spacecraft dueling – playing chicken with each others’ exhaust tails.

What about technologies even farther afield? Well, I have no idea what the practical applications of a lot of current theoretical physics might be. Maybe, someday, we can find some way to manipulate gravity or spacetime. Some thoughts on how to do this are already out there, and NASA has in the past studied such concepts. As an example of the kind of thing I’m talking about, we know that the reason why light can’t escape from within the event horizon of a black hole is that within the horizon, space itself is getting sucked in towards the singularity faster than light – at least, as measured by an external observer – carrying the light with it. Maybe there’s a way to push space along so that it carries our ships with it in a similar way. (“Warping” spacetime in this way is the usual handwaving explanation for how the USS Enterprise can exceed the speed of light with its – hey, hey! – warp drive.) Of course, this sort of technology is well into the realm of what Sir Arthur C. Clarke called “indistinguishable from magic,” so I hesitate to make claims about its capabilities. And these methods, if they are even possible, would require phenomenal amounts of energy. So now we run into the size problem!

Even for the most exotic propulsion systems, a spacecraft can only store a finite amount of energy and propellant. (The author of one spacecraft engineering textbook used at Cornell even calculated that every time Captain Kirk orders “all stop – full reverse!” at any speed greater than a fraction of Warp 1, the Starship Enterprise must use antimatter reserves with at least as much mass as the entire rest of the ship!) So, even the most farfetched engines cannot be on all the time and the spacecraft must follow the physics of orbits. When not directly engaged in maneuvers, the spacecraft would drift around or between planets and moons according to the laws described by Kepler, Newton, and Einstein. Space combat near planets and moons will involve ships jockeying for the most tactically advantageous orbit.

But fear not, space battle fans! Having to obey orbit mechanics doesn’t mean that you can’t attack your foes from any possible direction. You just come in at an orbit with a different eccentricity or inclination, and you’ll approach your quarry from “above,” “below,” or “sideways.” But orbit mechanics will mean that certain interplanetary trajectories make more sense than others, so you can try to predict your opponent’s moves and sabotage their plans by anticipating those paths. More on tactics later!

Maneuvering

This is a Viper Mark II. It’s as maneuverable as a jackrabbit and can flip end for end in point three five seconds. You have never flown anything remotely like it, so don’t think that you have. Today we will be doing basic launch, approach and landing maneuvers. Anyone not paying attention is liable to end up as a puddle of something to be hosed out of the cockpit by the chief of the deck.

-Lt. Kara “Starbuck” Thrace

Even when limited to Keplerian orbits, an enemy starfighter could attack your own ship from any direction relative to whichever way your ship and its guns are facing. It would be critically important to respond to attacks as quickly as possible – by bringing your own weaponry to bear, bringing defensive lasers and heavily armored areas into line, or perhaps by simply positioning your main engines for a good thrust out of the line of fire. So, your space fighters need agility – the ability to spin in place quickly.

Modern spacecraft typically use off-center thrusters, wheels with variable speed, gyroscopes, or some combination of these to change orientation in space. Of these, gyroscopes are the most efficient at turning stored energy into rotation. One way to think of a gyroscope is as a device that stores angular momentum. Gyroscopes store more momentum when they have more inertia or spin more rapidly. So I would expect the most maneuverable starfighters to have some massive rotors whirling around somewhere within their bodies.

The physics of momentum and inertia are very unlikely to change in the future. For a given amount of momentum, an object with smaller inertia will spin faster. This means that if we want a space fighter that can spin around quickly, we need to give it a small inertia, and the smallest possible inertia for a fixed mass and density is a solid sphere. So the most maneuverable fighters should be as sphere-shaped as possible – or, at least, have their most massive components clustered as close to their center of mass as possible. As with everything written here, this is an engineering tradeoff. Which is more important: having a fighter shaped like a perfect sphere for agility, or having gun turrets protruding out from its surface? Having the sphere, or giving the fighter beefy engines? Spherical shape, or preferentially armoring certain sensitive areas? I suspect that the most maneuverable fighters of any space fleet will be the most sphere-like, but they will not actually be solid spheres.

One possible alternative to building spherical space fighters that can spin rapidly in place would be space fighters that can spin rapidly about certain axes of rotation but not others. Perhaps some craft can exploit the physics and stability of rotations to achieve certain kinds of maneuverability at the expense of others. Or, we could design spacecraft with segmented, articulated arms. Those vehicles could gyrate like gymnasts: while one part of the spacecraft twists out of the line of incoming fire, another part could be swinging in to return shots with its own guns.

The drawback: any mechanisms, including gyroscopes, on a spacecraft are a weak point. Modern spacecraft typically don’t have many mechanisms, because the vibration of launch could shimmy mechanical components just enough out of alignment that they jam when they’re needed. Such issues have been responsible, for example, for the deployment failure of Galileo‘s high-gain antenna. (Engineers figured out another way to have the spacecraft send its amazing data back.) The more mechanisms there are on a spacecraft the more chances there are for something like that to go wrong. Of course, part of the problem nowadays is that we have to pack our spacecraft into cramped launch vehicle fairings to get them into space. If we could build them in orbit in the first place, and had people or robots on hand to fix the glitches…

Spacecraft Structures

Correct! 6,000 hulls.

-Professor Hubert Farnsworth

Right now, our spacecraft are severely limited by both the mass and volume our launch vehicles are capable of lofting into orbit. Even when we build modular structures in space, they have to be very low-mass. On a combat spacecraft, that means small fuel tanks, few weapons, and skimpy armor. Unless something fantastically new comes along to make it cheap and easy to put a lot of mass into space – not impossible, if unlikely in the next decade or so – we won’t be able to build a lot of capability into our space fighters. So the thing that would let us build hefty combat spacecraft structures is the ability to use resources that are already in space.

This is called in-situ resource utilization, and I am thinking specifically of nickel-iron asteroids. These asteroids are made of metals that could, potentially, be processed by robotic factories. The foundry robots could easily push processed materials, or even finished components, out of the asteroids’ shallow gravity wells. It seems funny to think of spacecraft made out of iron or steel, but if the raw material is already up there, then mass becomes less of a concern except as something that reduces the ship’s maximum acceleration. Mass would no longer be prohibitive in assembling and launching spacecraft.

Asteroid foundries and shipyards?

Now you can start to imagine hulking space battlecruisers with thick armor plating; their shapes governed by zero-gravity maneuvering and propulsion requirements rather than by aerodynamics. With asteroid-processing capabilities, there wouldn’t be any reason not to armor combat vessels, particularly if there are humans on board. The standard tradeoff applies: if you’re willing to lose maneuverability and acceleration, you can go ahead and cover your star destroyers with layers of metal plating. (What an image: space ironclads!) In fact, I’d go ahead and build the biggest battle stations by burrowing into the metal asteroids themselves.

Almost every spacecraft we have ever built, from capsules to the Space Shuttle, has some direction that qualifies as “down.” There’s a very simple reason for this trend in design: we built those spacecraft on Earth. But if we build the spacecraft directly in space, then we can build them specifically for zero gravity. There would be no need for a “deck” structure on spacecraft, so you won’t see things with mostly flat shapes. (Includes the USS Enterprise, Star Destroyers, Terran Battlecruisers, the Battlestar Galactica and the like.) I’ll give it to on-screen depictions of space vessels: it’s hard to film in zero-g, so everyone invents artificial gravity. But, even in movies, the outer spacecraft structure need not look like an oceangoing ship – and, in far-future real life, it won’t. If there is any orientation to the interior structure, it would be with “down” pointing toward the engines so that the crew can have a tiny bit of gravity while the ship is under thrust.

Weapons

Okie-dokie, okie-dokie… Let’s fire blue particle cannons, full; red particle cannons, full… Gannet magnets, fire them left and right and let ‘em run, all chutes… While you’re at it, why dontcha toss that at ‘em, killer. That should take care of old lobster-head, shouldn’t it?

-Jason Nesmith

You might be surprised just how much space weapons experience we have from the Cold War – even including Soviet manned space stations with guns on board. Much of that experience is with, in science fiction parlance, kinetic energy weapons.

Even the tiniest bits of matter flying around in orbit are enough to damage and destroy spacecraft. Space debris, or space junk, is a growing problem. (This is one reason why it’s such a big deal that the Chinese sometimes blow up satellites in orbit.) So if we want to destroy an enemy vessel, we should just throw a bunch of junk and shrapnel at it at high speed. Debris clouds would, in addition, make excellent space mines. I’m not the first to think this: A Soviet experiment even went so far as to test a flak-like warhead.

No, not a laser - a hypervelocity projectile simulating a debris impact

I think missiles are unlikely as space weapons until antimatter engines are available. A chemical rocket would start at a disadvantage after a large initial burn to pick up speed, and then would rapidly run through its propellant if it constantly thrusts towards the target. If it’s only making course correction maneuvers, the name of the game would be evading the projectile until it expends all its propellant and can no longer adjust to your ship’s course corrections. With a matter-antimatter engine, though, the missile could easily achieve relativistic velocity (making evading it much, much harder) and it would be able to use its propellant efficiently to match any maneuvers its target makes.

If guns and missiles aren’t science-fictiony enough for you, how about some energy weapons? Lasers could travel for hundreds of kilometers to melt and destroy things. The US Air Force’s megawatt-class Airborne Laser Testbed does exactly that from a Boeing 747. A similar space-based laser might have an even longer range. Such weapons would be devastating to spacecraft. They would easily mangle delicate instruments; even the tiniest hole in the wrong place could be catastrophic. However, these things would take a lot of power to fire, which might be a disadvantage. They also won’t travel forever before the beam disperses or defocuses, so although a laser strike travels at light speed, it won’t expand the theater of space combat beyond a local orbit. (Kinetic weapons, on the other hand, would actually have a near-infinite range, though they would be easier to dodge because fighters could see them coming!) Weaker lasers might still find uses on the smaller starfighters, though, as weapons to blind enemy instruments or destroy incoming ordnance – exactly what the Air Force’s ALTB is intended for.

A more exotic idea might be some other kind of energy burst. We know that solar flares can disrupt satellite operations, and high-energy bursts from all the way across the universe can blind our instruments. Computers and electronics are the guts of spacecraft. Suddenly hitting a spacecraft with an intense electromagnetic field could erase hard drives, scramble data, lock up transistors, and overload sensitive components. This might be the use for nuclear weapons in space – though it would be better to find a way to generate an EMP more efficiently, without all the waste heat and dangerous residual radiation of a nuclear blast.

All this reliance on computers and instrumentation opens up another avenue for attack in space: electronic warfare and information warfare. Decoy drones could broadcast radio and infrared radiation to confuse adversaries. Positioning systems, radar, or other instruments relying on received transmissions could be spoofed, fooling them into giving their operators false data. Space fighters might even try to hack into enemy systems and plant viruses, take control of enemy starfighters, or just scramble enemy computers on a ship-by-ship basis to take them out of the fight. As we’ve learned throughout the history of space travel, even a single misplaced or mis-entered command can disable a spacecraft.

None of these are the most exotic future space weapons I can think of (though they are certainly ones that I might expect to appear in space wars). Remember back when I wrote about propulsion systems, and speculated that at some point we might develop propulsion systems based on direct manipulation of gravity or spacetime? Future space warriors could employ little drones with those propulsion systems, designed to travel faster than light and then ram into enemy spacecraft. They would be impossible to detect before their devastating impact. It gets worse, though: just imagine weapons that operate by stretching or squeezing spacetime in some nefarious way around your foes’ starships. (Perhaps these are the “wormhole weapons” Scorpius was always going on about.) I shudder to think of an advanced enough, evil enough people to deploy spaghettification as a weapon.

Similarly terrible are the weapons that might be deployed from space to planet surfaces. Devastating weapons would be terrifyingly easy to set up.

Sensors and Stealth

They can’t have disappeared. No ship that small has a cloaking device.

-Captain Needa

There are two ways to detect objects in space: we can either detect the radiation that the object emits, or we can bounce some of our own radiation off it and look for the return.

Spacecraft will certainly emit radiation. Heaters that maintain components at working temperature, or crew cabins in comfort, emit thermal radiation. Electrical systems emit low-level radio signals. And spacecraft near planets and stars will reflect light. Managing thermal radiation is a challenge even now, for spacecraft that aren’t trying to hide from detection. For combat spacecraft, the problem becomes one of minimizing the amount of radiation emitted towards the enemy and detecting the emissions from an opposing vessel.

Against the background of a star, planet, or moon, detecting radiation emission and discriminating it from the background – quickly – could be quite difficult. There are even challenges when looking against the background of space: detectors must be kept cooled to cryogenic temperatures so that thermal radiation from the detector optics doesn’t overpower the emissions from the target. (The cryocoolers will also make parts of your space fighter hotter and, therefore, easier to detect.) These technologies may improve in the future – we’re reaping those rewards now, with better and better space telescopes peeling back the layers of the universe. The more reliable way to detect an enemy starfighter is the second option. Technologies like radar and laser rangefinding will find application in locating spacecraft for quite some time to come. Radar would also be the device of choice for identifying and tracking incoming weapons fire. If the alien space imperium has flak-cannon-equipped battlecruisers, then radar would immediately allow your own fleets to track and evade the incoming shrapnel.

How about hiding from enemy sensors? Well, we’ve pretty much got radar-stealthed aircraft figured out. Faceted, uneven surfaces reflect radar pings away in a pattern that leaves little signal power headed back to the receiver. The same principle would apply to stealthing spacecraft from radar detection. Even more exotic devices, however, are on the horizon: cloaking devices made out of metamaterials. These already work in radar wavelengths. One possible sci-fi application works like this: take a space fighter and cover the exterior surfaces with tiny nanostructures that redirect radiation around the craft. Voila! Invisible spacecraft. Another interesting idea: these metamaterials could also channel the thermal radiation signature of your fighter away from the enemy, to keep their best thermal sensors from detecting your ship.

Defenses

Not equipped with shields…then buckle up!

-Terran Battlecruiser Commander

Engines, mechanisms, and sensors would all be weak points on a combat spacecraft. In the face of all these flak bursts and energy discharges, how could a space cruiser defend itself? Well, heavy armor would be one way to handle impacts. But that requires either that the ships be built in space, since launching heavy things gets very expensive very quickly; or developing armors that are extremely low-mass for the protection they offer. The latter possibility is not out of the question, if we can come up with some type of exotic composite or extreme non-Newtonian fluids. Those armors are too thin to protect electronics from energy bursts, however.

Another possibility: Scientists and engineers on Earth today are looking into magnetic deflector shields to protect humans from radiation on a journey to Mars or beyond. These shields work just like the Earth’s magnetosphere, protecting a spacecraft from charged particles and plasma. Such devices could help defend spacecraft against radiation-based weapons. Strong enough electromagnetic fields might even help deflect shrapnel clouds, though that would take more effort to design and implement.

My thought is that starfighter defenses will be largely the same as starfighter weapons: guns and lasers. Those weapons could shoot down missiles or knock bullets off course if your ship can track incoming weapons fire accurately enough and swivel its point-defense guns around precisely enough. That’s another reason why I think missiles would have limited application in space battles, and why flak would be a terribly effective weapon – your enemy is not likely to be able to deflect every piece of shrapnel. Nor are you, for that matter!

Communications and Control

What matters is we built the ansible. The official name is Philotic Parallax Instantaneous Communicator, but somebody dredged the name ansible out of an old book somewhere and it caught on.

-Colonel Graff

Communications will likely be by lightspeed means for a long, long time to come – radio and laser devices. The thought of developing something like Orson Scott Card’s “ansible,” from the Ender’s Game universe, has kept many science fiction fans intrigued (myself included). Often, the ideas of quantum teleportation or quantum entanglement get called upon to explain those devices. Unfortunately, though you could use quantum entanglement to embed a message, part of the communicating device must operate by other means – limited by the speed of light. It seems like instantaneous communication may have to wait until we figure out how to use wormholes and can send couriers or light beams through those.

In my first article, I assumed a near-current level of technology and concluded that communication lag would make on-site humans necessary to coordinate our defense against the alien invaders. But perhaps the first aspect of technology to advance beyond the level I described earlier will be robotics and computer control. Even now, we’re making advances in autonomous rendezvous and docking between spacecraft. And on the ground, we have robots and computers capable of driving themselves, flying themselves, coordinating their actions…all sorts of autonomous operations!

With the right advances, we could go right ahead and build squadrons of autonomous drone fighters. Human operators would control overall strategy, but not the maneuvers of each drone. With powerful enough engines, the drones could even execute maneuvers much faster than a human could react, making direct human-in-the-loop control of the drones (like the US Air Force does today with UAV’s) impossible. (Readers of Haldeman’s The Forever War and Hamilton’s Night’s Dawn Trilogy will be familiar with this concept. In fact, I quite like Hamilton’s description of the “combat wasps,” where overall strategy is dictated by a human being but the drones go out on their own to execute 50-gee thrusts, laser and antimatter barrages, and virus transmissions. Too bad the books’ deus ex machina ending was terrible.)

I can’t see us trusting everything to the machines, though, which means we need a place to put the brave human starfighter pilots and battle station crews. Since humans are squishy, the best place to put the crew cabin of a fighter or the command bridge of a space destroyer would be in the very center, where the rest of the spacecraft protects the humans within from harm. So we won’t be getting any giant glass windows on our bridge or bubble cockpits on our fighters – but a projection of the view outside. In fact, the virtual and augmented reality technologies appearing on Earth today would be perfect inside the cabins of space fighters.

Tactics

He’s intelligent, but not experienced. His pattern indicates…two-dimensional thinking.

-Spock

What might the disposition of forces in a typical admiral’s space fleet look like? Well, I think it likely that, with the advent of in-space construction, that fleet could include a wide variety of ships. Since interstellar and interplanetary distances are so vast, the heart of the fleet would no doubt be some very large craft to act as staging areas, transports, repair yards, and supply ships for the smaller vessels. I can also imagine several classes of smaller warships, from gunships to one-man fighters to robot drones.

The largest battlecruisers, which would already have huge masses and inertias, could take a wide variety of shapes – all heavily armored. As I wrote above, perhaps the easiest way to build such ships would be to hollow out asteroids. During combat, they would hang back and coordinate fleet actions while the smaller, more maneuverable ships jockey for position with the enemy. Those ships would be more agile, tending towards the spherical shapes I referred to before. Given that resources are limited, it makes sense for there to be only two main engines per craft (cruise and combat engines), only one or two forward-facing weapon systems on the smallest fighters, and a few turrets on the mid-size vessels. The gyrating ships would be more exotic, and probably would be either of the robotic or mid-sized variety.

Having a mothership/smaller ship architecture to interplanetary battle fleets makes sense for a number of reasons. The smaller fighters and gunships could dock to the mothership while in transit, allowing the mothership to charge their batteries, replenish their consumables, and give their systems a chance to power down for maintenance and to avoid fatigue. The hulking asteroid dreadnoughts will need to include vast life-support systems (CO₂-to-O₂ converting algae tanks, perhaps?); huge solar panels, nuclear reactors, or other generators or energy stores; supplies for combat, maintenance, repair, and perhaps even planetary occupations after the battle is done; all the landing pods and troops needed to secure a planet; plus the tremendously powerful cruise engines necessary to move all this stuff. All that might leave little space for guns and hefty enough maneuvering systems, so the smaller ships would do most of the fighting.

I’ve stressed, in my first article and again, now, how even the most advanced combat spacecraft will have to obey the physics of orbits for most of their combat flight time. This isn’t necessarily a limiting condition! All this fact means is that orbital dynamics will be the “terrain” on which spacecraft maneuver. Whether a more tactically advantageous orbit is at higher or lower altitude, greater or lesser eccentricity, or at a different inclination than the target spaceship’s orbit will dictate the tactical decisions a commander makes. It’s all about relative motion: lower orbits go around planets faster; inclined or eccentric orbits seem to oscillate around a circular orbit of the same radius. Different points in an orbit around a planet are better or worse for firing engines to escape; likewise, when coming in towards a planet on a transfer trajectory, some timings are better or worse for firing the orbital injection burn that makes a craft stay around the target planet. This slow dance would be choreographed by strategists and computers trying to estimate and predict enemy motions, but it would be punctuated by brief instances of faster-than-the-eye-can-see action. As technology advances more and more, the information warfare aspect will become more important during the slow periods and the fast encounters will happen more and more rapidly.

Doesn't this suggest orbit trajectories to you?

Moreover, the planets and moons are in orbits around their central bodies. So, depending on the relative configuration of all the planets and the technological capabilities of each side (any ion engines? antimatter engines? pokey solar sails?), one faction could try to predict the trajectories an invading force would take. Fleet admirals would have their choice of higher- or lower-risk launch windows: some might be easier for the adversary to predict, while others would leave their fleet with more fuel remaining for maneuvers once they have reached the destination. Commanders might elect to send decoy forces out along some trajectories, or just put piles of junk in orbit to screw with the enemy’s sensors and navigation.

As one fleet comes in towards their quarry’s homeworld, or as opposing fleets close in interplanetary space, the first thing any veteran interstellar patrol admiral would do is to depressurize his or her entire fleet, ordering the crews into spacesuits, to keep this from happening. While closing, each side might throw huge clouds of debris, shrapnel, and flak at each other. This would confuse sensors and be a huge hazard for the approaching ships. Each side would have to start up active radar scans to identify and evade the shrapnel clouds; perhaps tracking the radar pings that filter through the flak would allow the opposing forces to track each other, as well. The energy weapons would come into play next: because these weapons would require a huge energy discharge, they will need large batteries and capacitors to operate. Carrying a fully charged capacitor into battle would be a liability, so ship captains would fire their energy blasts as soon as possible – and probably leave the weapons unused after that. Perhaps the largest, most heavily armored ships could risk holding off on energy fire, or even recharging those weapons over and over again during battle. Finally, at the closest ranges, the guns and missiles would fire. It would certainly be spectacular to see – even without the fiery, gasoline-fueled explosions Hollywood transplants into outer space – and the wreckage afterwards would be a colossal problem to deal with. Hopefully, though, we will have shown the alien invaders who’s boss. If they do come all this way just to get into a fight, they aren’t going to pull any punches.

It’s How You Use It

Make no mistake: a space war would be a terrible thing. Even with all the humans ensconced in their spacecraft, it would be a bloody experience, ravaging lives, infrastructure, and planets. (After all, if you’re out there just to kill your enemies, you can drop asteroids on their planet.) It also wouldn’t bode well for any future contacts with alien species.

The good news, though, is that most of the technologies I’ve written about have civilian applications. These are the technologies that will help us colonize the Solar System, advance scientific knowledge, and defend ourselves against the forces of nature.

In-situ resource utilization will help us build not space warships but space colonies and transports to other worlds. High-powered lasers can give scientists better instrumentation, manufacturers precise machining, the populace better communications, and fusion reactions ignition. We must understand the physics of orbital debris in order to make space safe to travel. Radiation-armored crew cabins are going to be necessary to send humans into space for long periods. Agile spacecraft could observe astronomical phenomena that change on a rapid timescale, like imaging volcanoes on Io, tracking near-Earth objects, or responding to short-lived supernovae. Hypervelocity impacts are important to understand to advance our knowledge of impact cratering on planets. The cloaking devices that shunt thermal radiation around might be used to manage heat loads on a spacecraft to keep sensitive detectors and other components cold. Antimatter – perhaps the most inherently destructive material in the universe – would serve as the best interstellar spaceship fuel, and I certainly want to see interstellar exploration happen. Even the most destructive, overtly weaponized ideas I’ve written about may have applications to deflecting asteroids or other threats away from the Earth. (Some serious ideas include continuously blasting asteroids with intense light to ablate material and planting a factory that turns the asteroid into bullets that get hurled out of a mass driver; both impart a thrust on the asteroid to knock it away from Earth.)

I think that space combat physics packs a good double impact for young minds: with exciting stories, cool effects, and wild ideas, we can engage their interest; then as these ideas transfer over into technology development, we can develop the capabilities to expand human civilization out into the wider Solar System.

Blizzard isn’t alone in this, of course. For all its repetitive gameplay, Assassin’s Creed tried to be as much like playing inside a movie as it could (it’s only a matter of time until someone takes a similar engine to make the Bourne Identity video game, and that will be awesome). The Star Wars universe became an interactive movie with The Force Unleashed, especially on the Wii, which let players wave their hands through the air to control the Force (at least, in a rudimentary way). But besides the gameplay elements, The Force Unleashed is a great example for having production values right up there with movies – that game had some of the best concept art I’ve ever seen, the story was clearly thought out and compelling, and the acting was very well done. Speaking of acting, video games were once the realm of C-list voiceovers, but now we now have the likes of Martin Sheen voicing characters in Mass Effect 2 – which had a tremendous cinematic trailer, enough to make me wish for an XBox.

I really like this trend. It makes video games into – gasp – a reputable medium for storytelling. I don’t think this format will ever replace books or movies, but it can certainly come up right beside them as a way to tell an interesting tale, describe compelling characters, teach us something about human interactions, and make the audience think.

Oh – what prompted this sudden post, you ask? Easy:

Not only is this an insanely high-production-value cinematic trailer, but it is clearly investing the StarCraft II story with a great deal of emotional content. Yeah, sure, it’s emotional content I’ve seen in movies/books/TV before – what is important to my point here is that the last time we saw this stuff, in the original StarCraft, it was from a standard RTS top-down perspective with voiceovers on little moving head-and-shoulders portraits of Kerrigan and Raynor. Now we see it as if it’s got a film director behind it. And now all the gamers get immersed in not only the plot but the characters’ experiences and sensations. Exciting stuff for storytellers!

Gatlinburg

They don’t call them the Smoky Mountains for nothing. It was pretty hazy most of the time I was there, so we got a lot of views of faded ridgelines marching off into the distance, covered by lush deciduous forests. Of course, as this was a family event, we spent most of our time in that cabin and generally had a great time. But my girlfriend and I managed to make two highly successful jaunts into Smoky Mountains NP.

The first was a bike around the 11-mile Cades Cove Loop Road. This loop starts at a visitor center an hour’s drive into the park and circumnavigates a flat expanse of farmland in the middle of the mountains. Even the drive in was fun – it reminded me quite a bit of the drive from my home to Williams on Rt. 2, on the part around the Mohawk Trail. Makes sense – the Berkshires and Appalachians formed in similar orogenies, though the scales were far different. Anyway, a farming community has existed in Cades Cove since the first settlers made it that far west and persists today. The loop road winds along what were – to an Ithaca biker – gentle hills and afforded us a lot of panoramic views as well as some brief visits to historic buildings. (The Park Service calls the Loop Road a “moderately difficult” bike. That was definitely on account of the condition of the rental bikes, and that they tell you not to use the front derailleur – I think the one on my girlfriend’s bike was actually disabled. Fortunately, I had my multitool….)

View from the Cades Cove Loop Road

There were quite a few panoramic views from the road. Cars and cyclists share the road, and despite the many pullouts, traffic was slow as the people in cars paused to take photos. I was happy to be a bit more mobile and flexible!

Cades Cove panorama

At the far end of the loop was another visitor center built near the old farming community’s mill – which looked very picturesque among all the trees! I had a fun time playing with the CDHK high-dynamic-range script on my little Canon point-and-shoot to get a picture of the half-shaded, half-sunlit mill building:

Cades Cove mill

Inside the mill, they sell corn meal ground at the site. Of course, we weren’t going to hump any of that out the remaining 5 miles on our clunker rental bikes! After pausing awhile for lunch – which gave us an opportunity to improve my blood sugar, the water level in our bottles, and the worst of the derailleur problems on our bikes – we set off again. I was most interested in the scenery of Cades Cove, as after seeing one or two of the historic old houses, you’ve pretty much seen ‘em all. However, there were still interesting historical tidbits to be had. Here’s a pretty cool grave we found in the cemetery around the Primitive Baptist Church:

Murdered by Rebs!

Our bike tour finished with a close encounter. On the way back, all the cars on the road suddenly jammed up, with occasional people pointing out of rolled-down windows. I cast a look off to one side and spotted a BEAR. I skidded to a stop, and it turned out to be a mother black bear with two cubs, rooting around in the shrubbery. They had warned us about bears at the visitor center, but I took those warning in the same way I take any warning about animals in parks – yeah, yeah, okay, if I see a bear I’ll be sure to keep that stuff in mind! Little did I know that they give these warning in the Smoky Mountains because you will probably run into bears. I took some grainy movies before they got too close for us to do anything but get back on the bikes and get going. We had no windows to roll up!

After the Cades Cove bike, we collapsed at the lodge. The next day, though, we were feeling intrepid enough to be looking at hikes in the park, and based on the description alone we picked out Chimney Tops trail. This was a big win.

Chimney Tops is a 2-mile trail to the summit of a mountain right next to LeConte Peak, the highest point in the park. The last mile of the two gets steeper and steeper, ending with a bare-rock climb. I, my girlfriend, and her cousin were very excited as we set off.

One of the first things to strike my about this hike was how lush everything was. I’m used to forests that consist large of trees and ground cover, like those in New England. Whenever I see a different forest ecosystem things seem a little funny to me. So far, the weirdest to me has been the ponderosa pine forest around the Grand Canyon, which consists of huge ponderosas and nothing else. Well, Smoky Mountains National Park is at the other extreme: solid green growing things from ground level up to the canopy.

Chimney Tops Trail

(Other great examples here and here.) We even managed to spot a Jordan’s Red-Cheeked Salamander in all that foliage – a salamander species found only in this National Park! Shortly thereafter, we almost had another encounter with a black bear, as we saw some fellow hikers hoof it down the trail to us and tell us that they were doubling back a bit to avoid a bear that had burst out of the undergrowth right in front of them. We didn’t see the bear – only some wet footprints a few minutes later.

Chimney Tops Trail reminded me a little bit of Angel’s Landing in Zion National Park – though the climates, geology, and trails had plenty of differences, of course – in that it ends with hikers climbing out onto a spur of rock that sticks out into a valley. So, as the hike got steeper and steeper, eventually it turned into this!

Scaling the summit

Pausing at a convenient stopping point partway up those rocks, I turned to one side and snapped the following panorama, a preview of what we saw at the very top.

Panorama near the top

Finally, after a bit of exciting scrabbling, we got to wedge ourselves into some crevices at the top and have a good look around. Scenic! (Click to panoramify.)

Chimney Tops summit panorama

Have I mentioned that I love my little Canon SD1000, which fits in my pocket, has a nice panorama mode, and lets me take HDR photos with CHDK? In fact, the HDR tricks I’ve been playing with were wonderful up on Chimney Tops, because they let me combine exposures to get some good shots of the progressively faded mountain ridges staggering off into the distance over the near hills. One such example:

HDR of mountain ridges

And another, capturing the tip of the mountain spur forming the Chimney Tops:

HDR mountain rock spur

Under the shade of the trees it had been nice and cool, but as we came out onto the bare rocks it warmed up. As we snacked, sitting on the mountain, the sun was flirting with the edges of some clouds. Coupled with the haze and humidity, this meant that we got a pretty nice optics show of sunbeams blazing down on the distant mountains. I tried to capture some of that with my camera, too, but found it about as difficult as the one time I was in a position to photograph the aurora borealis. Still, I got a few nice images!

Smoky Mountain sunbeams

I even figured out how to postprocess the living heck out of one panorama to bring out the sunbeams without totally destroying the rest of the image. I quite like the result, below! You’ll want to click on this one.

Smoky Mountains sunbeams

Maybe next time, I’ll have to try and time that hike for sunset or sunrise!

After a good deal of gawking, it was time to head back. Of course, climbing up the rocks and climbing down the rocks are two different problems, and we were a bit slower picking our way down the steep surfaces. This is the best picture I got that gives a real sense of going down. Notice all the deformation in the tilted stratigraphy, with girlfriend and her cousin for scale. (The runner-up is this photo.)

Going down!

I’ve gotta say that the Smoky Mountains were definitely worth a visit, and I’d happily recommend Chimney Tops as a good morning or afternoon hike. I like hiking, and I like our National Parks, so I was happy for the chance to get to see another in an area of the country I haven’t been to.That’s one of the things I like best about the United States: we’ve got so much stuff within our borders, but everyone uses the same money, understands English, and follows the same road signs. And sometimes we even feel like protecting what we have, so we can go into these spectacular places!

Gatlinburg ridges at sunrise

See all my pictures on Picasa - I had fun tweaking them all on the plane back to Ithaca!

At an industry forum today hosted by NASA’s Office of the Chief Technologist, several new research programs, open challenges, and collaborative initiatives got rolled out – and my research group’s projects were, literally, a poster child for NASA!

In this presentation on small spacecraft technologies, you can see a picture of Cornell’s CUSat spacecraft on page 5…concept pictures and graphs that I developed for my flux-pinned spacecraft project on pages 7 and 15…a picture of me in front of the Zero-G aircraft in page 15, along with a picture of my labmates with our equipment in microgravity…and the citation slide lists this post on my blog.

I’m thrilled – as a guy who’s passionate about space exploration and passionate about combining weird physics and radical engineering to make sci-fi technologies into reality, I’m really psyched to see innovative programs like NIAC come back from their funding graves and a new NASA focus on enabling technologies that will help make our space exploration dreams into exciting realities.

Time for space enthusiasts to lobby hard for the new budget on Capitol Hill!

First, let me say that I thought Robinson did a terrible job making her thesis clear. It sounded to me like she was trying to say, basically, that Big Science and Big Religion are at each others’ throats when they don’t have to be. (This is, aside from the implied existence of Big Science and Big Religion, a fine idea – though not a very new one.) However, she would say things like,

people on one side of the argument have claimed the authority of science, but they have not construed an argument that satisfies the standards of science.

As soon as I heard her say that, I thought her statement begged the question: What’s “the argument?” Who, representing capital-S Science, had made an Argument to or about capital-R Religion? So far as I know, the scientific method and body of scientific knowledge is not diametrically opposed in any way to religious belief. Certainly, a scientific theory could contradict a religious tenet, but “science” and “religion” themselves are not the mutually exclusive poles of any spectrum I can think of. Nor can I think of any “argument” that the entire scientific community or body of knowledge have with the very idea of religion. I waited with bated breath to hear Stewart immediately voice my thoughts (“And what argument would that be?”), but sat in frustration as he nodded along with her, letting her define this imagined Science vs Religion debate on her own terms.

This struck me as dangerous.

Perpetuating the idea that Science and Religion are set against one another is dangerous because it implies that they are somehow equivalent, or at least equivalently valid means to accomplish the same thing. That implication is dangerous because it opens up questions like, “Why can’t we teach religion in science classes?” (Or even, “Why can’t we teach science in religious school?” – something that I also do not think is appropriate.) In fact, science and religion are not equivalent ideas or equivalent means. Science is a set of methods by which people can rigorously develop models of aspects of the universe based on observational data, as well as the accumulated collection of such models (which we call “scientific knowledge”). Religion is a belief system, based on faith rather than observation, mostly concerning ethics and morality, but with a good deal of mythology, and sometimes rituals designed around some socioeconomic lines thrown in. I have not heard “religion” collectively offer an alternative to the scientific method for garnering knowledge about the cosmos, nor have I heard the scientific community offer a set of ethical guidelines on how best to treat our fellow human beings.

When Stewart finally asked Robinson to provide an example of an “argument” made by “science” that does not satisfy the standards of science, she said:

I don’t think, frankly, that it’s scientific to proceed from the study of ants to a conclusion about the nature of the cosmos.

Again, given the ludicrous nature of that statement, I was surprised that Stewart didn’t make it an obvious jumping-off point for a joke. (My own would have been, “Oh, you read the last issue of Cosmological Entomology, too?”) Seriously – in what peer-reviewed journal article have any scientists, say, proposed a model explaining the nature of dark matter based on the exoskeletal structure of the ant? Not only does this premise seem completely fabricated, but I take issue with her statement that such a conceptual connection – extremely unlikely though it may be! – is unscientific. On what grounds does she make that claim, and by what authority can she determine what is “scientific” and what isn’t? If a scientist can, through rigorous, repeatable experiments, develop a model that connects ants with quantum gravity, and that model stands to peer review, then it is certainly scientific. (Whether that scenario is possible or probable is another matter.)

Jon Stewart himself provided the most damaging statement of the interview:

I’ve always been fascinated that the more you delve into science the more it appears to rely on faith.

His supporting example?

You know, they start to speak about the universe, and they say, “well, it’s actually, most of the universe is antimatter.” Oh, really, where’s that? “Well, you can’t see it.” Well, well, where is it? “It’s there.” Well, can you measure it? “Eh…we’re working on it.”

His implication being, of course, that scientists take the existence of dark matter (I think he must mean dark matter) on faith, just like religions take the existence of their gods and afterlives and morality on faith. He couldn’t be more wrong – scientists did not suddenly wake up one day, invent the idea of dark matter, and go around preaching to all other scientists the Gospel of Dark Matter. No, they developed the idea of dark matter as a model that fit certain exhaustive observations of the rotation rates of galaxies. They fact that we cannot see dark matter with our eyes is not relevant. Years of observations led to a model including the presence of dark matter, and further observations have been consistent with that model. No scientist asks another to accept the existence of dark matter on faith.

Certainly, if you question a scientist enough, you will get them to the point where they will tell you, “I don’t know the answer to that question.” What’s inside a book? Paper. Inside the paper? Cellulose molecules. In those? Atoms. Those? Protons, neutrons, electrons. Inside the protons? Quarks. Inside those? I don’t know. Or I can’t conceive of that. Science does not have a model that gives a meaningful answer to that question, and in fact, under the Standard Model the question itself may not be meaningful. Some people make the claim – as Stewart made, above – that scientists therefore ask us to take quarks on faith. All the accelerator experiments and mathematical modeling and careful observation that led to the formulation of a model that includes the quark are thus thrown aside in favor of the implication that the existence of the quark is a tenet of some belief system. Certainly it is true that some scientific theories (gravity, relativity, evolution, quantum mechanics, ray optics, thermodynamics, …) are so widely accepted, so consistent with data, and so successful that scientists cite and use them without further proof. But this is not the same as assuming that they are true a priori. This is, in Newton’s words, standing on the shoulders of giants. And it’s an entirely practical step if we are to push the boundaries of scientific achievement. The proofs and supporting data do exist. And whenever a scientist says “I don’t know,” really what he or she means is “I don’t know yet,” for not knowing something at present certainly doesn’t mean that we cannot find out. (I’ll get back to you about the inside of the quark, but it may be a while.)

There is another key difference between science and religion that makes the idea of an Argument between them difficult to imagine. Religious beliefs are an individual choice, while scientific knowledge comes from prescribed processes and observations. For example, I can choose whether to believe in the God of Judaism, the Pantheon of Roman gods, Buddhist nirvana, or none. I can choose which religious philosophy to ascribe to, which morality to accept. However, I don’t get any such choice when it comes to scientific theories. Such theories are models that fit observed data, whether or not I believe that they are true. In fact, some famous scientific theories arose when a scientist came up with an interesting way to fit data, and published the theory simply as that – a novel way to get a good fit. Only later did those models turn out to have further implications for the structure of our universe. (For a very profound example, see Planck’s discovery of the quantization of energy.)

I can think of two principles that scientists take on faith. One: That we can observe the universe around us. Two: That we can derive conclusions from those observations and our previous conclusions. Those are the cornerstones of scientific philosophy. The specific content of accepted scientific models comes from years, decades, and centuries of accumulated data and theory. Scientists do not “believe” in their theories, because such belief is irrelevant to the fact that observational data supports those theories.

Robinson made one statement that resonated with me. She said,

The gladiators for both sides are, I think, inferior representatives of both sides, and that’s where a lot of the conflict comes from.

I think that Robinson perhaps may have been confusing science with atheism throughout this interview – and, perhaps, in her book, as well. But, certainly, I can think of many inferior representatives of religious thought. However, if the most outspoken “scientists” are “inferior representatives” of science, then our scientific community has some serious failings. It is true that scientific communication and outreach can be very difficult, and is often misleading or confusing to the layperson, and that is a problem that I think must be addressed if we want everyone to have a full understanding of scientific thought and be able to think critically about scientific results. Stewart’s thought that scientists take the existence of dark matter on faith is one great example of such a failing in scientific communication. Another prime example is that most students first learn that a “hypothesis” is an “educated guess,” which means that lay people often equate hypotheses with guesswork. These sorts of imprecisions in communication have definitely contributed to and exacerbated things like the debate over whether certain religions’ beliefs can be taught in science classrooms.

I’m going to close this post by wishing that Carl Sagan was still around. Anyone interested in the “debate” between science and religion – or the (more legitimate) debate between atheism and religion – really should read his novel Contact. It contains some wonderful insights into those debates in the scenes where Ellie Arroway and Palmer Joss argue with each other, and demonstrates that Sagan understood those debates – both sides – on a much deeper level than Robinson seems to. Contact also serves as a wonderful window into Sagan’s agnosticism in its climax and denouement. I won’t spoil it for you except to say that Sagan saw value in applying scientific methodology to religion – devising experiments to test religious beliefs – and he was perfectly willing to accept a positive outcome, if that is what the experimental data indicates. I think that is the proper intersection of those two spheres.