Space fact: despite Uranus having 14.5x more mass than Earth, you actually weigh 10% less on Uranus than you do on Earth. How? Uranus is spread out into a volume 63x larger than Earth, with 23% Earth's density, so at the cloud tops of Uranus we call a "surface", gravity is weaker
Caveat: you can't stand on Uranus. You'd free-fall until you got crushed by rising atmospheric pressures while being melted by rising temperatures. If you were not crushed & melted (thanks to an amazing space suit) you'd reach some point where you would float
Near the equator of Saturn you would weigh less than you do on Earth (by -8.4%), even though Saturn is almost 600x Earth's mass. Saturn is the least dense planet in our solar system, so it's same reason as before!
Saturn is at a knife-edge though: the fact it spins so rapidly means it has a large outward acceleration at the equator. The rotation causes Saturn to bulge out at the equator too, so you're farther from the mass. If Saturn stopped rotating, you'd weigh +6.5% MORE there vs. Earth
We need a mission to explore the interior structure of Uranus (Austin Powers: I thank you). So far it has only been visited by fly-bys. Planetary scientists do want a dedicated mission to Uranus or Neptune (it's about time right?) and they are even on Twitter: @IcyGiants
You can follow @physicsJ.
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