Expansion of spacetime.

[dstebbins]

The diameter of the known universe is about 89 billion light years. That's about 44.5 billion light years in radius. However, the universe is only about 13 billion years old.

 

This seems to negate the law that the speed of light can never be reached or exceeded, which means that the universe should be less than 13 billion light years in radius, not 44.5 billion.

 

Scientists (notably, Albert Einstein and his Theory of Relativity) have supposedly solved this dilemna by suggesting that the universe (not the matter and energy inside it, but spacetime itself) is expanding, and the rate at which it expands has no intrinsic limit.

 

This essentially means that the universe is expanding at over twice the rate of which the matter and energy inside it is moving apart from each other.

 

But if this is the case, how come we can't see this with the naked eye? If this is true, then, if I leave my TV and DVD player alone, to gather dust, for a year, the two should be significantly further apart after said year than they were at the beginning, yet they are always in the same location relative to each other unless I actually MOVE one of them! The same goes for my keyboard and monitor, or my car and my garage.

 

Sure, the universe is expanding at an astronomical level, but by scale, this seems to be something we should be able to detect with the naked senses in a manner I just described. So, why isn't it?

Edited October 25, 2009 by dstebbins

[Klaynos]

The local forces are stronger than the expansion force. The local forces being EM and gravity in this case. Even on galactic and cluster scales the gravitational attraction between objects is greater than the expansion. So things stick together.

[dstebbins]

Ok, let me try and get this straight.

 

In Stephen Hawking's "A Brief History of Time," he mentions one theory that the reason the universe is expanding and not collapsing is because, after a while, the force of gravity stops being one of attraction and starts being one of repulsion.

 

So, are you suggesting that, since gravity decreases and increases exponentially with distance, that, after a while, the force of gravity will become so weak that it is overpowered by the expansion forces, which increase linearly with distance?

 

Is that the gist of it?