How does gravity work?
Discussion
I was pondering on this the other day whilst out cycling...
I understand the notion of gravity pulling us towards the centre of the earth, but what I don't understand is why there is such massive resistance to change, but we're not being squashed flat on the floor?
On a bike, I'd be able to keep going on a flat surface with no headwind relatively indefinitely, but as soon as I start to climb, it gets very hard, very rapidly, to the point where you simply can't turn the pedals any more.
Admittedly, the slope looks steep to us, but even if I rode from sea level to the top of Everest, I'd be less than 0.15% further away from the centre of the earth, which strikes me as essentially nothing. I remember reading that if the earth were reduced to the size of a billiard ball, its surface would be smoother, so how can such a small relative change in altitude cause us so much effort?
I understand the notion of gravity pulling us towards the centre of the earth, but what I don't understand is why there is such massive resistance to change, but we're not being squashed flat on the floor?
On a bike, I'd be able to keep going on a flat surface with no headwind relatively indefinitely, but as soon as I start to climb, it gets very hard, very rapidly, to the point where you simply can't turn the pedals any more.
Admittedly, the slope looks steep to us, but even if I rode from sea level to the top of Everest, I'd be less than 0.15% further away from the centre of the earth, which strikes me as essentially nothing. I remember reading that if the earth were reduced to the size of a billiard ball, its surface would be smoother, so how can such a small relative change in altitude cause us so much effort?
TwigtheWonderkid said:
I get where the op is coming from. It seems odd that gravity is strong enough for the sun to hold Pluto in an orbit, yet at the same time weak enough for me to be able to pick up my mug of tea.
That's pretty much it, but it amazes me at a much closer level than Pluto.I understand the whole notion of potential energy, conservation of energy and so on. I suppose what I struggle with is the difference in the power of gravity on a body at rest relative to its pull (me riding along on the flat) and a body fighting it (me going up the hill).
Look at any given mountain stage of the Tour de France. If I managed to make it up the climb at all (which is extremely unlikely), I'd be half dead by the time I reached the top, thanks to gravity. If I tried to ride back down without using my brakes, I'd be fully dead by about the second bend, again thanks to gravity, yet when I just stand still, whether at the top or the bottom of said mountain, I'd barely notice the effects of said gravity, and whilst a TdF climb might feel like the biggest thing imaginable to ride, it's actually a minute fraction of the distance to the centre of the earth.
Gassing Station | Science! | Top of Page | What's New | My Stuff