The Rings of Earth, Part II: Implications

What are a long car trip and hosting boring virtual office hours good for? Thinking about how our science and society would be different if the Earth had rings. Science fiction writers, take note.

As I was writing that earlier post, my officemates and I got into a discussion about some of the implications to (at least Western) science and philosophy of such a ring system. One of them suggested that the rings, which would be mostly aligned with the Earth’s equator but would precess with the Moon, would be quite obviously separate from both the purported “celestial spheres” and the Earth, so maybe the ancient Greeks could have dispensed with that destructive Platonic notion much earlier in the history of Western science.

I got thinking and realized that, in addition to their own dynamics, the rings would have a few other obvious effects on the science of those cultures at high enough latitudes to get a good view of the ring system, without seeing them edge-on.

First, the shadows of the Earth and Moon would be visible on the rings. These shadows would be shaped like portions of circles, and would vary in size and shape with time of day, month, and year. From observations of these shadows, easily possible with the naked eye, the Greeks, Egyptians, and Chinese ought to have been able to show without any doubt that the Earth and Moon are spherical. They may have been able to deduce the position of the Earth’s spin axis and axial tilt by comparing the shape of the rings and the shadows on them to the time to year. (These experiments could be quite simple: make a stiff, lightweight circle or hoop, hold it at arm’s length at night, move the circle in and out and tilt it back and forth until its edges line up with the shadow on the ring. Add a little simple geometry, and BAM: I would have just found the axial tilt of the Earth.) They should also have provided some kind of estimate of the distance to the Moon, as observers could compare the size of the Moon with the size of its shadow. And comparing the Earth’s shadow on the rings to the positions of the background stars would have given the ancients an incredibly accurate nighttime clock.

Second, and perhaps most importantly of all, the rings would vary radially in opacity. This would make them beautiful to behold, yes, but it would also give naked-eye astronomers an absolute scale for photometry. Annuli of the rings would block out the light from some stars, but not others. The thicker rings would block more stars than thinner rings, giving a gradation of occultation scales. By comparing which rings block out which stars, observers would have been able to make statements about the relative brightness of the stars with a degree of precision unknown until Christian Huygens arrived on the scene – even surpassing the precision of that experiment. Still more exciting, if the ring was able to occult the Sun, that same method could have been used to measure the light output of the Sun. Now, coupled with the insight that the Sun is a star and a crude estimate of the Earth-Sun distance, an observer should have been able to deduce from naked-eye observations approximate distances to the stars.

I’ll say that again: If the Earth had rings, the ancient Greeks, Chinese, and Egyptians might have had a sense of the scale of the Cosmos. The Romans and Indians might have known what a parsec is.

Furthermore, this photometry could have been used on the visible planets as well as stars. That would have told the ancient astronomers that Mercury, Venus, Mars, Jupiter, and Saturn were a lot closer to the Earth than the stars. In fact, if the ancient photometers tracked the brightness (and, therefore, distance from the Earth) of each planet over time, they would have noticed something interesting: the planets move in circles about a point that is not located within the body of the Earth, but is rather in the Sun. The heliocentric model for the Solar System would have been adopted in ancient times.

Now, knowing that the planets go around the Sun, and the stars are all rather a long way away from the Sun and from each other, ancient astronomers might have realized that other stars could have planets just like the Sun does. Think about what that idea might have done to Western philosophy and religion in their formative years: other Earths? In the sky?! Going around other Suns?

Here’s a possibility I’m not sure about: if the ring was thick enough, it’s possible that it might dim the Sun enough that an observer could safely look at our star with their naked eyes. If so, then sunspots might have been visible to the ancient civilizations. In that case, they might have known that the Sun is not a perfect glowing sphere, and that it rotates. They might have known about the 11-year solar cycle.

And then, imagine what could have happened once Galileo stormed onto the scene with his telescope. When he looked at Saturn, he would have known exactly what he was looking at. “Ears” indeed! By watching Saturn’s rings wax and wane with each Saturnian year, he would have identified the orientation of Saturn’s ringplane to the ecliptic. Knowing that Saturn has rings would have told scientists that Earth’s features are not unique to our own planet.

Early telescopes might have been powerful enough to identify some of the larger rocky chunks making up the Terrestrial rings. Observing their orbits at different radii within the ring could have lent a lot more data to scientists like Kepler and Newton, who were trying to figure out what forces kept the planets in orbit. Armed with data on the orbits of ring particles and Kepler’s Laws, early scientists might have been able to get a pretty good estimate for the mass of the Earth and fix the Earth-Sun and Earth-Moon distances pretty accurately.

I’m thinking that, given how great a dynamical laboratory the Saturnian ring system is, rings around the Earth would have allowed the progress of science to advance much more rapidly, as the rings would provide a precise tool for measurements of position, time, and distance of celestial bodies. If the laws governing those bodies had been puzzled out, say, before Christianity dominated Europe, imagine what society would have resulted….

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11 Responses to The Rings of Earth, Part II: Implications

  1. Torsional Metric says:

    That was pretty fun!

  2. John Peloquin says:

    Yeah, the Carthagenians or Romans with nukes- perhaps that’s the solution to the Fermi paradox.

  3. Andrew Hookway says:

    A downside, though, is that people might’ve had *less* curiosity about the cosmos. With the rings reflecting light, it’s like natural light pollution. At least half the year, we wouldn’t be *able* to see many of the stars because of all that reflected sunlight.

  4. Joseph says:

    Good point – though I don’t know that that effect would stifle curiosity. It might make it more difficult to observe faint stars, but that doesn’t necessarily say anything about the people making such observations.

    A more likely curiosity-stifling effect would be if the rings became some kind of sacrosanct religious object. 😉

  5. Andvee says:

    The thing I’d be curious about is what sort of effect that would have on the planet itself. Everything is synced to our day night cycle and seasons… What will plants and animals do when one season you receive more evening light and the other you receive less especially if the ring were reflective like the moon. If it were present from the beginning of evolution things could of looked very different to capitalize on the light differences. I’d also wonder what effect it could have on the weather and climate. What happens when you reflect a lil extra light off that ring onto one hemisphere and slightly shade the other. Mmm fun things to think about…

    • Charlotte says:

      Weather and climate probably wouldn’t change that much, speaking as an Atmospheric Science student. While you are getting more energy on the night side of the planet, a lot of the pressure and temperature differences that drive weather aren’t planetary in scale. It’s mostly driven by heat-capacity difference between the land and ocean, and all rings would do is increase the solar constant. As for plants…I can’t say. But you have quite the excellent point. ;P

      There’s one thing, though, that would get kinda depressing if this were the case, especially once we figure out the Heliocentric model and the scale of the cosmos. If you look at a lot of older religions and creation myths, there’s this big “we are a special little snowflake” message going around. Greeks, for example: Prometheus (Titan of foresight and wisdom, no less) specially created humans, while his brother E-something (I’m bad with names…) created everything else. Christianity: God spent a whole day making mankind in his image, and just made the earth, with everything else as an afterthought. What everything this article would do is smother this notion in the crib. And my question is: what would that do to early civilizations, or early man in general, to know with certainty that the earth isn’t the center of the universe, our star system might not be unique at all, and thus there is absolutely nothing that makes us special? Over time, a more enlightened view on the subject might appear, but think of how crushing this realization would be in a time when most people died horrible lives at age thirty. How would this notion change the face of western culture, or just culture in general?

      • josephshoer says:

        I’m not sure exactly that the realization would have been “crushing.” Several Greek philosophers had equally belittling ideas, and their culture seemed to get along fine. You are probably right that cultures would have turned out very differently, though, and I agree wholehearted with that assessment. I, for one, wonder if we might not have turned out more open-minded.

  6. Hi, my name is Charles Choi, and I’m a science reporter who has written for The New York Times, Scientific American, and others.

    I had come across Ron Miller’s work, and then your work, on what Earth might be like if it had rings like Saturn.

    I was curious — how do you think having such rings might affect human space exploration?

    Phil Plait thinks it’d be bad for space exploration (http://blogs.discovermagazine.com/badastronomy/2009/12/21/the-rings-of-earth/). He suggests they’d be major hazards for human spaceflight; that geosynchronous satellites would not be possible; and that even polar orbits would have to cross the rings at least twice each orbit.

    However, I was wondering what you thought. Since the lower bound of the Earth ring would be the upper limit of the exosphere, people could still reach low Earth orbit, right?

    Also, if one wanted to reach the moon, wouldn’t it still be possible, if one chose a trajectory that went over or under the rings?

    Also, might the Earth ring be useful as a source of raw materials? Admittedly, it’d be low in or empty of volatiles, but would the rocky material be worth mining?

    Just curious — Best — C.

    • josephshoer says:

      First of all, Phil Plait’s article on the subject is excellent. I’m a fan of his blog and thought process. I’m glad you enjoyed mine, too.

      I think that a ring system would certainly have had an impact on the development of space technology and missions, but it wouldn’t necessarily end all exploration. Missions would just have to go a little differently. Planetary rings tend to be concentrated in equatorial orbits with very little thickness, for example, so you’re exactly right that a trajectory to the Moon could simply go “over” or “under” the rings. In fact, since the Moon’s orbit is inclined relative to the Earth’s equator – and thus it is inclined relative to the hypothetical rings – the same Apollo lunar trajectories might have simply worked fine at avoiding ring collisions, depending on the time of launch.

      The rings would probably not threaten geostationary satellites with destruction. Under my assumption that the rings extend out to the Earth’s Roche limit, they would go out to a radius of 2.86x Earth’s radius. But a geostationary orbit is way beyond that, at 6.62x Earth’s radius. A better question than whether a geostationary spacecraft would survive, though, is whether it would make any sense – the rings might scatter radio beams in an adverse way. Again, that’s not an insoluble problem, but it could be a problem that we’d have to solve to make geostationary satellites worthwhile over a ringed planet.

      Similarly, I have the rings extending inward to a radius 1.59x Earth’s – that is, to an altitude of about 3760 km above the ground. That’s well above low Earth orbit, around 500 km altitude, where mapping satellites and astronaut activities take place. But my choice for the inner limit of the ring was much more arbitrary than the outer limit. So I don’t want to make too firm an answer on that end!

      As for mining, well, I’m just not sure. I guess it would depend what kind of rock the rings are made of!

  7. Sam Edwards says:

    Great work (I feel the need to call you Mr. Shoer lol)!
    I was wondering if you had any thoughts on what a high density material ring would do for tidal/gravitational forces on Earth? Like, would the rings be able to take on (i.e. replace) the rolls currently administered by the Moon? Specifically I’m thinking of an Iron or Silicate based ring.
    Would a dense material ring system be strong enough to influence our planetary tilt and rotation to its current levels?

    Thanks!

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