Saturday, June 25, 2011

Gravitas

So what's up with gravity? Why is it so physically baffling? It seems to me it is just a question of objects' density versus that of the air. Like when I jump, I land back down because I'm more dense than air. However, a balloon filled with helium is less dense thus floats. There you go gravity explained. But then again, my explanation conveniently forgets the orbit part.

Also, Archimedes proved that a sphere has two thirds of the volume and surface area of a surrounding cylinder (including the bases of the latter), and regarded this as the greatest of his mathematical achievements.

5 comments:

Dementor said...

'It seems to me it is just a question of objects' density versus that of the air.'

Really? Density of the air?

Seriously?

Damn....

Dementor said...

You might wanna read about the 4 fundamental interactions and how we humans explain stuff. But seriously, gravitation has nothing to do with air.

Barbarosa said...

Well, I was coming from how objects float in water. And mixing it with air column pressure and shit.

Dementor said...

Any object wholly or partially immersed in shit will be subjected to a force equal to the weight of the shit displaced by itself.

Master of the Craw said...

Basically: you jump in the water and the volume of the container (tub, lake, pool, whatever) remains the same. As a result the water in the container goes up because it's being displaced. This mass of water wants to go back down because it has a mass as well, this produces a force on your body pushing you up. There are also other forces in play, including the relative density of water vs you. These forces push your body up. If you stand up in the water you sink. If you lie down you'll probably float. At some point a balance is reached and you float. Etc...

Gravity is an attribute of mass, anything with mass has gravity. But gravity is really just an attractive force and is no more special than any other force (actually, Einstein showed that Gravity and acceleration were the same).What exactly causes gravity to exist is open to debate and while it's generally true that denser materials have more gravity for the same volume that's because you they also have more mass (density is usually measured in mass/volume). If the sun somehow doubled its volume it would still exert the same gravity because it would still have the same mass (well, in addition to the mass of mercury which it would have swallowed).