Serious answers to hypothetical questions; I don’t know why I have such an infatuation with them. But seeing an arbitrary situation analyzed with as much real world data as possible brings me great joy, as if it somehow validates the asking of such unreal questions. Anyways, enough of the preamble, I want to talk about one hypothetical in particular.
The question that caught my eye a week ago was “What would happen if the Earth and the sun switched places?” Now, the question doesn’t say when this is happening, so I’ll pick October 1, at 8:30 a.m., so then I’ll have a decent excuse to sleep in on a Saturday.
This question is bad news for the moon. Unfortunately for the moon, the radius of the sun is much larger than the distance from the Earth to the moon, and so it ceases to be a moon immediately and becomes fuel for the sun.
Mercury does a little better. Normally it would be whipping around the sun at 59 kilometers per second, which is pretty fast, even for a planet. All of the sudden, the sun and its massive gravitational potential well moves pretty far away, and Mercury is simply moving way too fast for the sun’s gravity to reign it back in. It exits the solar system still travelling at 40 km/s.
Venus tries to follow Mercury, but fails and is sent into a 31-year-long elliptical orbit, the close end of which still falls within the orbit of Earth. This is quite possibly bad news for Earth.
Mars, being relatively close to the sun, all of a sudden moves into a 325-day orbit that is a little too elliptical to be comfortable year round. The summers on Mars would be scorching as it passes within a quarter of the Earth’s distance to the sun, while the winters could be nice, only a little outside of the Earth’s orbit. Now we have two planets that cross Earth’s orbit, and a collision seems, well, likely. Things are not looking good for you, unless you’re in the planet recycling business.
Jupiter is thrown only a little bit off its orbit, and none of the other outer planets seem to even take notice of the sun’s sudden move. Remember, our solar system is really big. The effect of the Earth-sun swap on the outer planets’ orbits is like an orange being dropped on the floor. Sure, it’ll bulge a little bit, but it’s essentially the same thing. I mean, the outer planets might have lost their equilibrium during the mix-up and end up flinging around the solar system haphazardly, but that sort of thing takes tens of thousands to millions of years. We don’t have time to wait around for that.
So now that we’ve looked at the rest of the solar system, what would happen to us? First of all, at 8:30 a.m. on Saturday when the swap occurs, it suddenly becomes night again. See? A perfect excuse to stay in bed. The sun would appear on the opposite side of us, and all of a sudden it would get rather dark — especially so because we lost our moon. Interestingly, because our velocity is the same, and the Earth has swapped places with the sun, we would begin rotating in the opposite direction around the sun with basically the same orbit as before. This means the seasons start going backwards. Fall will become summer, leading to spring, and finally winter. This seems great; a double summer is just what I need. It might be worth it, even if could mean the end of the Earth. Unfortunately, the Earth’s tilt and the swap means that the seasons are instantly inverted as well. Just like day becomes night, fall becomes spring. And remember, now that we’re orbiting in reverse, winter follows spring. So basically we’re still stuck in the season leading to winter. At least I got to sleep in.
Okay, so there would be some neat effects with the seasons — but what really happens to Earth? Does it smash into bits as it’s pelted by asteroids? Does it spectacularly crash into Mars or Venus, now that their orbits overlap with the Earth’s?
Well, a collision with something seems likely. The Earth is orbiting clockwise, but the swap didn’t change the rotation of any other planets, so not only do we cross Mars’ path twice a year, but we do so while heading towards each other! Despite that, we wouldn’t collide with Mars or Venus for thousands of years, at least. Mars, Venus, and Earth do not lie on exactly the same plane as they orbit the sun, and the sudden change in Mars’ orbit exaggerates the difference so that even when Earth and Mars are passing right “on top” of each other, they’re still four million kilometers away from each other. Eventually their gravitational pull would lead to a collision, but on an astronomical time scale; too long for us. For a few days, though, about every 20 years, Mars would get close enough to look a quarter of the size of the moon in the night sky. And cause small tides. (We miss you, moon.)
Okay, but we’re doomed by all the scattered asteroids on the asteroid disk, right? Well, still no. The problem (if not having the Earth destroyed really is a problem) is that space is, like, really big. Huge, even. There are about one million asteroids larger than a kilometer across in the asteroid belt, and yet doing the math shows that when these asteroids are scattered, an impact with Earth will still only happen about once every hundred to thousand years. And we could survive several impacts from such an asteroid; the Chicxulub impactor (which is a great band name, by the way) that hit Earth about 66 million years ago had a diameter of greater than 10 kilometers! I mean, it likely triggered a mass extinction, but still, life moved on.
So, surprisingly, life would likely move on as normal. Roughly speaking. Seasons would continue, meteor showers would be great, we’d lose the moon but gain a friend in Mars. At least I can rest soundly, knowing that death will not be immediate.
