A common physics factoid is that Saturn will float in water. This is because Saturn has a density of 687.00 kg/m³ and water has a density of 999.97 kg/m³. As Saturn has a lower density than water, it should float. This works with objects like ice cubes, which also have a lower density than water, so float. It makes sense on the surface, but scaling this up to planetary sizes makes make things behave differently. After spending some time reading about it, I’ve found that despite having a lower density than water, Saturn wouldn’t actually float, and here is why.
First of all, Saturn couldn’t float anywhere on Earth because there isn’t a body of water big enough on Earth for it. If you imagine an iceberg in the ocean, or an ice cube in a glass, a small amount sticks up above the water, and there is a massive amount below. Saturn would behave the same, but Saturn is so big that there isn’t a body of water on Earth big enough to accommodate the bit of Saturn below the water. So, first of all, we would need to find a planet which would hold a body of water deep enough.
Fortunately the guys over a Wired have done this calculation for me (so you can check their maths), but they say you would need a body of water as deep as 6x the Earth (sounds massive, but remember that Saturn is nearly 10 times bigger than the Earth – its huge!).
So if we assume we find a massive planet which can support this much water, we still have another problem. Having a body of water as deep as 6 Earths is going to put the water at the very bottom under an immense amount of pressure -much much more than can be replicated in a lab. What water would do under all this pressure is a mystery. The amount of pressure is massive its hard to comprehend, but I’ll try and give you some sense of scale. The depth of water would be about 7600km, and the deepest part of the ocean on Earth is the Mariana Trench, which is only 11km deep.
Usually under large amounts of pressure liquids would become solid, but water is unique in that its solid state floats on its liquid state, and this is much more pressure than is required to just chance a liquid to a solid. Its unknown what would happen to water under all this pressure, but I have come across a number of theories, some say you would end up with a superheated liquid with a reduced volume and others suggest you would end up with something called electron-degenerate matter, which from what I can tell, will probably result in a star forming – quite dramatic.
Either way, all theories suggest that the conditions created would be extremely unstable, and so unlikely to allow a gaseous giant to float on them. What’s more likely is that the chemicals which make up Saturn (which are largely hydrogen) would also undergo fusion reactions and contribute to the forming star.
Finally, if you manage to overcome the very real problem above, there is one more issue. Like our planet, Saturn has a core which is made up of liquid metal and rock, neither of which would float on water. In fact, most of Saturn is gas, mostly hydrogen, and so if you were to bring it onto a planet which could support a big enough body of water to support Saturn, the gravitational pull would probably disintegrate the gas, and the core would sink to the bottom of water – not float.
It might seem like Saturn would float on water because it has a lower density than water does, however, in practice, it will probably be a very different story.
First of all, the sheer volume of water that is needed would create a very unstable and reactive environment, which potentially could cause a star to form, which would probably destroy Saturn rather than keep it afloat.
Secondly, if you somehow solve the problem of the first point, the core of Saturn would fall to the bottom of the water, and the gas would probably disband – again, not really floating.
It really is a theoretical nightmare, and not something that my Physics A level really equipped me to solve, but it does seem very unlikely that Saturn would float in water.
This Youtube video will give an overview of the information found on the article tab. If you want to know more about the topic, or want to see where the information came from, have a read of the article after you watch the video.
No – the conditions are impossible. There is more to consider than just density.