The Theory of Fabric of space and free fall.?

Question

The theory of fabric of space means that for instance the solar system is on the fabric, and is not in free fall. So does that mean that the planets and suns don't fall, they are on the fabric of space or are they in constant free fall. Even if there is the fabric of space what holds it up.

Answer 1

Very good awnser stilldeb, and yes that pretty much sums it up, but now imagine that fabric being in 3 dimensions and add a 4th, time just for fun. The math gets hairy but there are all kinds of cool outcomes when objects in " freefall " begin to interact with one another.

Answer 2

Remember, that in space, there is no "up" or "down" in the way you're thinking.

What's "up" on Earth? 'Up' is basically any direction away from the center of the Earth, or even more simply - the opposite direction from Gravity. If you were to look at the Earth from the Moon, you'd notice that when a person points up from the north pole, that they're actually pointing in the exact opposite direction as another person pointing up from the South pole at the exact same time.

Ok - so here, 'up' is away from Earth.

If you zoom out to the level of the Solar System, the same concept holds true, except that it's not the Earth governing everything's movement anymore; it's the Sun. The Sun's gravity is dominant in the Solar System when you're not near other massive objects like planets and moons and such. So if you're a planet, 'up' is away from the Sun, and 'down' is towards it. The planets are constantly free-falling towards the Sun because its gravity has them trapped. The reason they never go 'down' into it is that they're also travelling with some "sideways" speed as well. This tangential velocity (sideways speed) is fast enough so that the rate they "fall" into the Sun pretty much equals the rate at which the Sun's round surface curves away from them. This is exactly the same thing that keeps the space station in orbit as it goes around the Earth.

The 'fabric' of space is more of an abstract concept than it is anything else - it's never been measured directly. The main thing that seems to keep its existence as a concept as far as I know is Einstein's theory of general relativity - that gravity is simply our way of perceiving the curvature of spacetime caused by massive objects. The other area where spacetime fabric as an actual entity comes into play is when cosmologists talk about the expansion of the universe. It's the fabric of spacetime itself that's expanding, and that expansion is causing the galaxies to mostly fly apart from each other.

Inside those galaxies, though, gravity is strong enough to keep the individual stars from flying apart from each other, just as the Sun's gravity is strong enough to keep the planets from flying away from it.

The fabric of space isn't some ultra-thin sheet that the planets are all sitting on, like a trampoline. It's fully three-dimensional, and goes in all directions. If it were a thin sheet, you couldn't go to the South pole, or whatever part of Earth was 'sitting' on it, and you couldn't go that direction in space, because the fabric would be in the way.

We all go through the fabric just as light goes through the fiberoptic lines. It's a fabric, but the light inside finds it transparent and moves freely through it as though it weren't even there.

Answer 3

your misunderstanding...well science in general.

things dont free fall unless somethin pulls them down. there is no need to hold the planets up, because nothing pulls them down. planets are in a constant free fall towards the sun. its what we call "orbit"

so i have to ask, did you just make that up?

Answer 4

As I see it, "fabric" is just an analogy for how things work.  It helps us to think about things to see them as on a piece of stretchy fabric, but this fabric doesn't actually exist.  

For example, when you think about how the Earth orbits the Sun, you can imagine that the Sun is lying on a piece of spandex and causing a dent in it.  The Earth would just keep traveling forward in a straight line, but its path is bent by the dent that the Sun makes in the fabric.  It's like one of those charity coin donation things where the coin spirals down the funnel, except the Earth has enough momentum that it never spirals into the sun.  (link to charity coin spiraling thing:  http://www.youtube.com/watch?v=ad4HEs-i_... )

Anyway, all of this is just a metaphor to help people understand how gravity causes objects to be attracted to each other.  There isn't really a piece of fabric.  In reality, the Earth is constantly in a free fall towards the Sun, but its forward momentum matches the speed of the freefall just exactly so it never spirals inward.  

I hope the way I've put this makes at least a little sense.  

Answer 5

The orbit of the planets cannot be compared to orbit around earth as the planets are traveling and controlled by gravity and centrifugal force. Orbits around the earth are a free fall state. If we were in free fall we would not have gravity.