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If everything in the Universe is made of energy <=> matter, then how is it possible an object could pull another object which is very far away, since there is no contact, nothing link them?

Here we go.. another nuclearsilo thread.

is that a rhetorical question?

What??

You lost me at "If"...

Well can you answer it? I can't. Just because it's silo it doesn't mean it's retarded by default.
I don't know how exactly gravity works. It's something that a bigger object attracts a smaller object, but why? Idk, magnetic fields? You tell me!

http://en.wikipedia.org/wiki/Gravitation

>>

Big thing bend space, make other thing get closer.

Spacetime. Bend it.

I bet you 30+ replies before the end of the hour

At least it's a semi interesting topic.

Not a:

"If apple is red, why then are monkey have fur?"

Maybe we can take it to the next level for Silo and ask why objects with mass bend space?

Yeah, why is that? How can it bend?

I once watched a documentry explaining it in a rather nifty way. since I don't know what video it was I'll try to draw and explain it.

as Azilius mentioned: gravitation more or less exist because objects in space distort the time-space.
you can imagine the time-space to look like a rubber clothe with square patterns when seen from above, just a piece of clothe lying a table from the side. now if you were to grab the center of the clothe and stretch it downwards, form above the pattern wouldn't have changed even the slightest, it will still look exactly the same, however when you look from the side, it's turned into a cliff. now if you would slide a ball over the blanket in both situations, in the 1st the ball would just go over it, in the second it would fall in the cliff/hole. that's basically how you can visualize gravitation.

In a place where there are no objects the space time is normal (A). in a place where objects exist (planets, etc) the time-space is bent around them (B).

I think this is one of the easiest ways to explain gravity. excuse me if I am mistaken somewhere or unclear.

well... if you were to throw a rock in the water. the water has to move aside right? the water wont go through the the rock's molecules. it'll 'bend' around the rock. Wouldn't space-time react the same way?
(not sure about this part though)

Poehalco = best description so far

Good luck explaining Relativity here.

The "bending" is just a good way to explain it..it doesn't actually "bend" in the sense we think and how it is pictured by a flat sheet with a heavy ball on it. Although, that is the best method to visualize it..

Ok bend space. For example this:

How does that make 2 objects pull each other?



If the other one have its own gravity too, how could it escapes its hole to reach other hole?

No, it splashes because you throw it and the environment around the rock changes from air to water. If it's already in water, you throw it, you wouldn't see the same effect. Planets always exist in space.

Lock plox.

Why?

In keeping with the paint theme:



Who cares if the smaller object has a "trough" of it's own, it will still maintain a straight line of momentum through space-time until if falls into the valley of a larger object. It's going to take a path of least resistance to it's inertia/momentum...so it "falls" into the trough of the larger object and usually orbits.

These are basic diagrams to "get the picture". Einstein's relativity involves 4D geometry/topology...it's confusing.

Here are some equations to play with (wiki):

As another example from someone who only kinda thinks they have the right idea.

Put a ball on a couch, sit on the couch near the ball. The bending of the couch from your mass causes the ball to roll towards you.

lol, that works too.

I don't have anything smart to say...

But the question could have been worse indeed.

It's because the ball is too small therefore it's easy to imagine that. So now what if 2 people sit on the couch? If 2 balls same size, same mass put on the couch? Euh, I don't think they are gonna pull each other.

They're not massive enough. We're talking planets here. Check my example. And like I said, this is just a geometric example to "kind of get the idea". It doesn't work exactly like this.. to understand it fully you'll need to understand General Relativity, topology, etc. Good luck with that.

You can, though, calculate the gravitational pull of two objects (your keyboard and your mouse for example). It's just ridiculously small and irrelevant.

I still don't understand. How could the ball moves to the area with higher height

Picture spacetime as being fluid, not so rigid. Picture the 'ripple' around the smaller object the same as the ripple around of water..the momentum of the smaller object pushes through the ripple into the trough of the large object. It pushes it out of the way, down into the larger trough. Momentum carries the ball forward.

Our pictures are actually not the best representation.. the small object wouldn't be attracted to the larger unless it was already in, or moved into, the slope of the larger object. In other words, the outer edge of the large spheres slope is the extent of it's gravitational pull.

What? Maybe you can show me a 3D pic, with space bending force of 2 objects same size; add up the force and see how the sum could bend the space

Go for it. Just because you can't grasp relativity doesn't make it not true.

We're using 2 and 3 dimensional models to explain a process that occurs in 4d+ space. Of course it's not going to be perfect. If you want to have a true understanding you'll need to master mathematics and then general relativity.