Oh Gravity.. you so crazy..

A question is asked frequently to me, how far away would I need to get away from Earth before gravity no longer held me? Phrased differently, how far away from Earth would you need to be before it’s gravity had no effect on you? The answer is simple. You’d need to leave the Universe.

Yes, that seems quite a distance, taking into effect that gravity is a pretty weak force when you compare it to others. No matter how far away you get from an object, even if every thing in the universe was removed except for you, and Earth, they would still attract to each other.

Even if you put them at opposite ends of the observable universe, 93 billion light years away from each other, you’d still be attracted to Earth. Now, it may take longer than the universe would theoretically exist for you to come into visual range of Earth, but you’d get there.. eventually..

Wait a tic.. Visual range wouldn’t exist if you and Earth were the only two objects in the universe, right? Wrong! Earth is glowing.. it’s called Earthshine (or Earthglow), and our old friend Leonardo Da Vinci penned this one up to one of his discoveries. Want to see Earthshine from where you’re currently sitting? Wait until it’s a clear night and the Moon is in a crescent shape, and look at it. You’ll see the crescent from the Sun illuminating it, but you can still kind of see the full moon between the crescent tips – that’s Earth’s glow. It’s not land based artificial light from cities or a giant Bat signal, it’s Earth’s natural glow. Now, attribute about 99% of what you’re currently seeing as our Sun being reflected off the oceans and clouds of Earth, but remove the Sun and there’s still some naturally occurring light here!

Let’s get back to talking about Grabity (misspelled on purpose!). Any recent video you’ve seen on Cmdr. Chris Hadfield usually is him doing an interview, and then doing some pretty cool “Zero-G” stuff like spinning his microphone in place.. like so..

Mic Check

Just what’s happening here? If there’s no escape from gravity period, how is the commander and his microphone floating? Well, we have another force in this situation acting on both of them, and everything in the International Space Station, called centripetal force. It just so happens that the commander is falling at a rate of 9.8m/s squared.. but he’s also traveling around the Earth at an equal speed, so he’s falling but being thrown outwards at the same time. It just so happens that this is the exact same situation that the relationship between Earth and Sun have. Earth is orbiting the Sun at a rate that’s equal to it’s gravitational pull. That’s why if everyone on Earth were to jump at the same time, even if we managed to move Earth a bit more inwards and closer to the sun, therefor decaying it’s orbit and beginning it on an inwards spiral of doom, we wouldn’t burn up. Earth would correct itself.. or the sun would.. I’m not entirely sure anymore.. 😛

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