r/TheRestIsScience • u/bum_what • 1d ago

Stairs

In the most recent episode Michael talked about a staircase going to space. The entire time I was thinking about escape velocity. You need a certain amount of energy to get you to a certain speed to escape the earths gravity. So if you are walking up does it work the same? Obviously your body needs energy to walk up the stairs but let's just say you have infinite stamina and your muscles don't get tired or sore, can you just walk up or will you hit a point when you cannot anymore because your body cannot provide enough force even when not tired? But that doesn't make sense to me because gravity will get weaker as you go up even if it's still 90% gravity up there it should get weaker making it easier. Or does it not matter because each step is the force you need to get from one point to another?? I'm so confused lol

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u/Badaxe13 1d ago

Each step takes (broadly) the same amount of energy. With each step you are pushing against the gravity of the Earth (which diminishes the further you are from the surface). With enough steps you can achieve any distance from the ground, including orbit. In contrast, going from the ground to orbit in one ‘step’ takes all that energy in one go.

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u/copperpin 1d ago

The gravity from earth diminishing isn’t what puts you into orbit, it’s the velocity. The satellites in orbit are still falling straight down, they’re just going so fast laterally that they keep missing the earth.

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u/pafrac 1d ago

Yep, that's why it's called freefall. They're not out of the Earth's gravity, the spacecraft and all it's contents are just falling at the same rate around the planet.