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mogila
Metal newbie

Joined: Wed Dec 07, 2011 9:30 am
Posts: 87
Location: Australia
PostPosted: Fri May 05, 2017 11:16 pm 
 

My question relates to areas in superluminal regions of space. It is often stated that some objects are moving away from us faster than light can reach us. However, is it possible that space is expanding quickly enough that light coming from objects in superluminal regions will enter our Hubble sphere and eventually we would be able to detect it?

My other question relates to if the universe is infinite. If the universe is infinite, doesn't that mean it always had to be infinite. So at the moment just before the big bang, the universe was also infinite at this time?

The universe is so large that I find it highly dubious (and a little bit sad) that we will never venture outside of our solar system. On a personal (and possibly slightly nerdy) note, I sometimes enjoy looking up at the night sky and seeing the stars. I wonder what is out there and if there is anyone on another planet orbiting one of the many stars, who sees our sun as just a tiny dot in their sky and thinks the same as I.

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iamntbatman
Chaos Breed

Joined: Sat Feb 21, 2009 5:55 am
Posts: 10701
Location: Tyrn Gorthad
PostPosted: Sat May 06, 2017 1:27 am 
 

I think whether or not all of existence as a singularity counts as "infinite" is more a question of semantics than physics.
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awheio
Metalhead

Joined: Tue Jul 05, 2011 2:00 am
Posts: 482
Location: United States
PostPosted: Sat May 06, 2017 10:16 am 
 

mogila wrote:
My question relates to areas in superluminal regions of space. It is often stated that some objects are moving away from us faster than light can reach us. However, is it possible that space is expanding quickly enough that light coming from objects in superluminal regions will enter our Hubble sphere and eventually we would be able to detect it?

The reason things are moving away from us at an accelerating rate is because space is expanding, because of dark energy. The faster space expands, the more distance light will have to travel, until eventually no photons can reach anything. The expansion of space is the problem, and is the reason the problem with only get worse (according to the accepted models). If space weren't expanding, after all, gravity would eventually drag everything back to a singularity, and those superluminal objects would eventually all touch.

EDIT to add: There's a lot that I don't understand about how light travels between inertial frames and all that. But excluding things like black holes, where "location" gets weird, light would just continue toward us, and would be pulled by gravity, etc. The problem is that space is expanding AROUND the photons. As they travel through space, the amount of space they need to travel increases; when the expansion of space exceeds the speed of light, those photons cannot effectively travel through space any longer. The universe is dead and cold.

Quote:
My other question relates to if the universe is infinite. If the universe is infinite, doesn't that mean it always had to be infinite. So at the moment just before the big bang, the universe was also infinite at this time?

Yes, I think that's right. But it doesn't make much difference. A singularity is by definition of infinite density, because it is crammed in to a point, which has no dimensions. So, whether it is infinite or finite matter crammed into that point makes no difference. You know, like how infinity times infinity is just infinity.

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Goatfangs
Wicker Mantis

Joined: Tue Mar 18, 2008 5:02 pm
Posts: 2361
Location: United States
PostPosted: Sat May 06, 2017 6:24 pm 
 

There aren't regions that are superluminal. If you take a highly red-shifted galaxy that emitted its light 13 billion years ago, that object is moving away faster than the speed of light. Any light emitted today will never reach Earth because the vast amount of space between Earth and the distant galaxy is expanding faster than light. If you could use Instant Transmission just like Goku to travel to that galaxy, you would find that the local space isn't at all different from that around Earth. The galaxy itself may be completely different from what we see from Earth. It's just the further an object is, the more space is between Earth and the object, and so the expansion of space adds up across that vast distance to exceed the speed of light.

I don't think the Universe is infinite. It's fucking big, but not infinite. The full size of the Universe could be much bigger than we can ever see. The age of the Universe is around 13.8 billion years, and factoring in the expansion of space and the finite speed of light the diameter of the observable Universe is 93 billion lightyears. The total size of the Universe could be much bigger than this.

If the Universe is truly infinite, then there would exist different versions of you on different versions of Earth.
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Diamhea
Eats and Spits Corpses

Joined: Wed Feb 14, 2007 7:46 pm
Posts: 8490
Location: At the Heat of Winter
PostPosted: Sun May 07, 2017 10:19 am 
 

Don't we already have a "space" thread?

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Grave_Wyrm
Metal Sloth

Joined: Sun Mar 04, 2012 5:55 pm
Posts: 3683
Location: The Irespan
PostPosted: Sun May 07, 2017 5:42 pm 
 

We sure do.

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