[PacMan3456]

Um, I think I might have an idea on what gravity is. I'm not very experienced at physics and stuff, as I'm only in 7th grade, so I was looking up my theory and came across this website, so I decided to post it on here and see what everybody says. Okay, so here it is:

If everything in the universe was continuously growing, expanding, and accelerating, could that be the cause of gravity? Like if you had a balloon, and you blew it up at just the right speed and kept blowing it up faster and faster, if you put something on the balloon, wouldn't it stay there, as the balloon would be pushing against it as it, (the balloon,) accelerated? Please let me know it there is anything that would not be possible about this theory. Thanks!

-PacMan3456

[ajb]

PacMan3456, on 29 January 2012 - 08:45 PM, said:

If everything in the universe was continuously growing, expanding, and accelerating, could that be the cause of gravity?

This sounds more like an observable effect of gravity.

[Janus]

To evaluate any idea, we have to check it against what we actually measure and compare what the idea predicts against what we see.

For example, for the gravity that we feel on the surface of the Earth to be due to the Earth expanding, the Earth's surface must be expanding upwards at a rate of 9.8 m/sec/sec. At this rate, in just 1 day, the earth will have grown by some 5735 times.

Now consider the Moon, it has a much lower gravity at its surface, and would only have to expand upwards at 1.6 m/sec/sec, to maintain that surface gravity. At that rate it will only grown by 3987 times in the same day. Thus the moon would be 60% smaller in relation to the Earth than it was before. The Moon getting smaller relative to the Earth is something that we would have noticed

Secondly such a model would not explain how gravity gets weaker with distance or how it is possible for the Moon to be in orbit around the Earth.

Keep on thinking though, even an idea that doesn't pan out is useful if you learn something from it.

[PacMan3456]

Janus, on 29 January 2012 - 09:28 PM, said:

To evaluate any idea, we have to check it against what we actually measure and compare what the idea predicts against what we see.

For example, for the gravity that we feel on the surface of the Earth to be due to the Earth expanding, the Earth's surface must be expanding upwards at a rate of 9.8 m/sec/sec. At this rate, in just 1 day, the earth will have grown by some 5735 times.

Now consider the Moon, it has a much lower gravity at its surface, and would only have to expand upwards at 1.6 m/sec/sec, to maintain that surface gravity. At that rate it will only grown by 3987 times in the same day. Thus the moon would be 60% smaller in relation to the Earth than it was before. The Moon getting smaller relative to the Earth is something that we would have noticed

Secondly such a model would not explain how gravity gets weaker with distance or how it is possible for the Moon to be in orbit around the Earth.

Keep on thinking though, even an idea that doesn't pan out is useful if you learn something from it.

Okay, thanks

[IM Egdall]

Pacman3456: The problem with your idea is it does not agree with what we observe. The expansion of the universe shows itself between clusters of galaxies. The distance between them is expanding. But within galaxies themselves, we do not see this expansion. For example, the distances between stars with our Milky Way galaxy are NOT expanding. Why? Gravity within galaxies overcomes the expansion of space.

To use the balloon analogy, physicists tell us to imagine coins pasted to the surface of a balloon. As you blow up the balloon, the surface expands, the distance between the coins expands, but the coins remain the same size. (The coins here represent galaxy clusters.)

But please keep on thinking!

This post has been edited by IM Egdall: 30 January 2012 - 04:22 PM