Have you ever looked up at the moon at night and wondered what would happen if it split in half? You might think we’d be doomed to the end of all life on earth, but you’d be wrong. Under very specific conditions, humanity would be treated to a beautiful view of two baby moons dancing across the sky instead. But what would happen to the tides? What would an eclipse look like? And what would have to go wrong for the Earth to be left with beautiful rings just like Saturn’s? This one’s a good one.
How Many Tsar Bombas to Slice the Moon?
First, let’s set up our hypothetical scenario. Let’s assume that we crack the moon exactly in half, 50% of the mass in each slice. How much energy do you think that would take? Maybe a nuke or two nukes. The Tsar Bomba is the largest nuclear weapon ever detonated, equal to 50 million tons of TNT. And it would take 30 billion Tsar Bombas to crack the moon in half.
Forming the Twin Spheres:
If we just cut it in half and didn’t pull the two sides apart, they would just smash back together really quickly, which doesn’t seem that interesting. So let’s separate the halves by 10,000 kilometers. And finally, let’s form these halves into two spheres instead of these weird half-moon shapes. This would happen naturally, but it would take thousands of years to round out our baby moons using gravity alone, so we can just speed that process up.
Two Moons Dancing:
Okay, let’s talk about what happens. As you know, the moons immediately start heading for each other, but since one of them was ever so slightly closer to the Earth, the pull of Earth’s gravity was just strong enough to make sure they don’t collide.
They enter an orbit with each other. It starts off pretty elliptical, but after the first month, it would settle into a nice, consistent pattern. The Earth is at the center with two baby moons dancing around it in orbit. The moons would take about 25 hours to complete one full orbit around each other, meaning their motion would look pretty slow in our sky. But over the course of the night, it would look something like this to us watching from the Earth.
A Solar View No Other Planet Gets:
One of the first questions I had when researching this scenario was what an eclipse would look like. We live on an insanely lucky planet where the sun and the moon appear to be roughly the same size in the sky, allowing us to view these perfect total solar eclipses. Every other planet in the solar system doesn’t get to enjoy these truly amazing events.
Here’s what a solar eclipse of Mars’s moon Phobos looks like. Each of our new baby moons would be about 20% smaller than the old moon. So what would a solar eclipse look like? Something like this. Their smaller size means we get to see more of the sun as they eclipse it.
Since the pairs circle each other every 25 hours, there would be a new kind of rare eclipse where we get to see our twin moons chasing each other over the face of the sun during the two to three-hour eclipse window. These would be extremely rare, but can you imagine getting to witness such a beautiful event?
During our mini eclipses, about 40% of the sun’s face would still be visible. This would make the dip in brightness typically experienced during a total solar eclipse about 500 times brighter. And while normally temperatures would drop by around 5 degrees Celsius, with our mini moons, we’d be lucky to even get one degree.
Lunar eclipses would be really interesting too. Most of the time, we would see just one of the moons covered by the Earth’s shadow, but occasionally, if the orbits align just right, we would get to watch our planet’s shadow move across the surface of the two moons. A stark reminder that we are just on a ball floating through space.
Brighter Nights and Double Shadows:
Our new twin moons would still go through a monthly cycle, going from new moon to full moon in basically the same way. But a really strange consequence of having two moons instead of one is that the full moons would shine about 30% brighter than our old full moon. This is because the total surface area of these two smaller spheres reflecting light back to the Earth is actually about 30% greater than the surface area of our current moon. Full moon nights would look much brighter, and astronomers wouldn’t be happy. The moon’s brightness is one of the most annoying features of our planet when it comes to making observations of distant stars and galaxies.
Why You’d See Two Distinct Shadows on the Ground:
But look down at the ground and you might notice something strange. Two shadows. The separation of the moon is great enough to have them provide two distinct overlapping shadows on the ground. The further apart they move, the greater these shadows separate from each other.
Solving the Three-Body Problem:
Now I can already see the comments. How are these orbits stable? I thought the three-body problem meant it would be chaotic, and one of the moons would come crashing back down onto the Earth. But that’s one of the biggest misconceptions about the three-body problem.
For any two objects orbiting each other while also orbiting some bigger object in a three-body system, there’s something called the Hill sphere. Think of it like the boundary their orbit has to stay within if the system is going to remain stable. I mean, we have this today with the moon orbiting the Earth while we are both in orbit around the Sun. The Earth’s Hill sphere is about 1.5 million km wide, and since our moon orbits are just under 400,000 km away, well within the Hill sphere, the system is stable. If it travelled outside of this boundary, the Sun’s gravity would start to disturb the fine balance of the orbits, potentially sending the moon flying away into space.
Now for our baby moons, their hill sphere is about 60,000 km wide, and since we set their orbit to be separated by just 10,000 km, they will stay nice and stable in their orbit around the Earth for at least a few thousand years, never separating enough for Earth’s gravity to pull one of the moons away.
The Unchanged Tides:
Okay, now what about the tides? We know the moon and the Sun are responsible for the tides we see here on Earth. The gravitational forces create bulges of water on opposite sides of the Earth, giving us the high tides. Earth’s rotation then moves different locations through these bulges, causing the tide patterns we are familiar with. In our two-moon scenario, you might expect the tides to just go crazy as the moons orbit around each other, creating this weird pattern of tidal bulges. But actually, the tides would be pretty much the same.
Every now and then, you might get a high tide that’s a tiny bit higher, but for the most part, these scenarios are gravitationally identical. Since the two moons still weigh the same as our single moon, the gravitational center of their system is indistinguishable from our current If you were the Earth, the gravitational pull of both scenarios would feel pretty much the same.
Earth Gets Saturn’s Rings:
Now here’s where things get spicy. If the initial conditions of the system weren’t exactly correct, and the orbits of our baby moon started to decay, spiraling in towards the Earth, something pretty magical would happen. There’s a region around the Earth known as the Roche Limit. It’s about 12,000 kilometers above the surface, and any celestial body held together by its own gravity that passed within this limit would be torn apart by Earth’s gravity.
Our baby moons would be destroyed, and we would be left with some truly beautiful Earth rings. A pale system of rings arching across our sky. For people closer to the equator, it would arch high overhead, while those closer to the poles would see it as a thin band towards the horizon. At night, we would be treated to a glorious view of it glowing brighter than the arm of the Milky Way. Again, not great for the astronomers, but amazing to look at nonetheless.
The Practical Impact of Ring Shadows:
Sailors would have a perfect compass in the sky to help them navigate. Our low Earth orbit satellites would have to adjust their orbits to avoid the rings, and ring shadows would be seen moving across the Earth’s surface.
And what’s amazing is, this happened in the past. Geologists around the world found a spike of a very specific kind of meteorite distributed around the Earth’s equator from about 500 million years ago. This tells us a 100km wide asteroid once grazed past the Earth, breaking apart within our Roche limit and forming a dusty ring system. These rings then fell back to the Earth over the next 2-3 million years, creating the deposits that the geologists found just last year. If our baby moons did create this beautiful ring system, they would stick around for about the same amount of time.
Future Mining and Martian Rings:
That is, unless we took the opportunity to mine the rings. Extracting resources already in orbit to make solar arrays and space elevators. Even if this doesn’t happen to the Earth, Mars’ moon Phobos, which I talked to you about earlier, actually will pass within Mars’ Roche limit, being torn apart, giving the red planet a beautiful ring system.
Conclusion:
If the Moon ever split in two, Earth wouldn’t be destroyed, it would just look very different. We’d get brighter nights, double shadows, and incredible twin eclipses lighting up the sky. The tides would stay mostly the same, but over time, gravity could turn those baby moons into glowing rings around our planet. Whether it ends in chaos or beauty, it’s a reminder of how delicate and dynamic our place in the cosmos really is.
FAQs:
1. Could the Moon actually split in half?
Not naturally, it would take unimaginable energy to do so.
2. Would Earth be destroyed if it happened?
No, but the skies and tides would change dramatically.
3. Would we really see two moons?
Yes, two smaller moons would orbit each other while circling Earth.
4. How would tides be affected?
They’d stay mostly the same since the total lunar mass remains equal.
5. Could Earth get rings from this?
Yes, if one moon got too close, it could break apart into a ring system.
6. Has Earth ever had rings before?
Yes, evidence suggests Earth had temporary rings about 500 million years ago.