What is more?

[Cerpin Taxt]

Originally posted by: tenshodo13

Originally posted by: mariok2006
The universe is finite? How so?

If there was a beginning, its finite.

That doesn't follow. The positive integers have a beginning, and they are infinite.

Also, if the Universe WAS infinite, wouldn't the night sky be filled with a bright light from the infinite stars in the sky?

No, because the lifetime of a star is not infinite, and infinitely many of them would be infinitely far away anyway.

 

[silverpig]

Originally posted by: Cerpin Taxt

Originally posted by: tenshodo13

Originally posted by: mariok2006
The universe is finite? How so?

If there was a beginning, its finite.

That doesn't follow. The positive integers have a beginning, and they are infinite.

Also, if the Universe WAS infinite, wouldn't the night sky be filled with a bright light from the infinite stars in the sky?

No, because the lifetime of a star is not infinite, and infinitely many of them would be infinitely far away anyway.

That's not the correct argument against Olber's Paradox. Along any sight line there should still be an infinite number of stars, regardless of age.

 

[Chaotic42]

Define "universe".

 

[Vic]

Originally posted by: silverpig

Originally posted by: DrPizza

Originally posted by: 911paramedic
Universe is infinite, I'm going stars. (Chemistry is one of my fall classes, so I reserve the right to revise this statement.)

That post is so full of fail.

A. Current understanding & model of universe = universe is not infinite.
B. wtf does chemistry have to do with astronomy?

A. Nuh uh

NASA

Given the assumption that the matter in the universe is homogeneous and isotropic (The Cosmological Principle) it can be shown that the corresponding distortion of space-time (due to the gravitational effects of this matter) can only have one of three forms, as shown schematically in the picture at left. It can be "positively" curved like the surface of a ball and finite in extent; it can be "negatively" curved like a saddle and infinite in extent; or it can be "flat" and infinite in extent - our "ordinary" conception of space.

Current WMAP measurements indicate a flat universe... ie infinite in extent.

I know you're somewhat of an expert in these matters, but IIRC the universe appears flat in 3 dimensions because its curved/spherical aspect is in the 4th (time).
Much like a person on earth thinking in 2 dimensions might think the earth is flat and infinite, so might a person looking at the universe in only 3 dimensions.
However, when one see that the moment of the big bang is the center of the universe, and you visualize time as just another dimension of space, you see that the universe is infinite in time and space, just not right now.

 

[Vic]

Originally posted by: Chaotic42
Define "universe".

The result of the singularity of space-time following the Big Bang.

 

[silverpig]

Originally posted by: Vic

Originally posted by: silverpig

Originally posted by: DrPizza

Originally posted by: 911paramedic
Universe is infinite, I'm going stars. (Chemistry is one of my fall classes, so I reserve the right to revise this statement.)

That post is so full of fail.

A. Current understanding & model of universe = universe is not infinite.
B. wtf does chemistry have to do with astronomy?

A. Nuh uh

NASA

Given the assumption that the matter in the universe is homogeneous and isotropic (The Cosmological Principle) it can be shown that the corresponding distortion of space-time (due to the gravitational effects of this matter) can only have one of three forms, as shown schematically in the picture at left. It can be "positively" curved like the surface of a ball and finite in extent; it can be "negatively" curved like a saddle and infinite in extent; or it can be "flat" and infinite in extent - our "ordinary" conception of space.

Current WMAP measurements indicate a flat universe... ie infinite in extent.

I know you're somewhat of an expert in these matters, but IIRC the universe appears flat in 3 dimensions because its curved/spherical aspect is in the 4th (time).
Much like a person on earth thinking in 2 dimensions might think the earth is flat and infinite, so might a person looking at the universe in only 3 dimensions.
However, when one see that the moment of the big bang is the center of the universe, and you visualize time as just another dimension of space, you see that the universe is infinite in time and space, just not right now.

Nope, it's flat in spacetime (on a large scale that is).

The way you can test is to measure a circle. If you take a flat sheet of rubber and draw a circle on it, an ant will can measure the diameter and circumference of the circle and will come up with a value of 3.14159... for pi. If you pinch the rubber into a saddle shape, the ant will measure a larger value for pi. If you push your finger down near the center of the circle and make it curve that way, the ant will measure a smaller value for pi.

In the same way we can measure the curvature of spacetime, although there are other ways of testing it. Now, while we live on a massive body which orbits another massive body and our point in space most certainly is curved (and can be measured! Gravity Probe B, deflection of starlight around the sun during a solar eclipse etc), on the grand scheme of things C=2*pi*r for very large circles indicating that our universe is, to within the best we can measure, flat. If there was some curvature to space we would be able to see it in the WMAP data.