Question tabout the expanding universe - Page 4

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micronesia

United States24799 Posts

April 07 2009 04:15 GMT

#61

On April 07 2009 12:17 travis wrote:

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but how do we know this when we have no way to test the affects of traveling over such a long distance on light?

It's the most likely scenario... certainly could be wrong, but no reason to believe it based on virtually all prior scientific experimentation in this field. Our modern theoretical formulas also support this claim.

also micronesia do you know why red shift led to the theory of expanding space? rather than just galaxies moving at different velocities?

I think it's a bit of a misconception that they measured the light from some stars, saw that it was redshifted, and then concluded acceleration. I'm not sure exactly how they did it as I haven't investigated it and the one documentary I saw years ago when this was first discovered didn't specify. The only thing that makes sense to me is that they observed the time-dependency of the redshift and noticed that it was essentially getting 'redder' although I'm surprised that there would be a detectable difference over the course of a few days/weeks/months.

liger13

United States1060 Posts

April 07 2009 04:48 GMT

#62

just a little note for pondering... since i guess that is what this thread is about...

Space itself can expand at speeds faster than the speed cap, light. (granted speed is the incorrect term). a planet further than this region, therefore, cannot be seen by us, for the light it emits is trapped as it tries to swim through this faster current...

Rekrul

Korea (South)17174 Posts

April 07 2009 06:12 GMT

#63

All men want are holes. Some men find them on earth. Others have to look into outer space.

SpiritoftheTunA

United States20903 Posts

April 07 2009 06:29 GMT

#64

@micronesia

all evidence for an accelerating universe are from distant type Ia supernovae, fitting their magnitudes+doppler shifts to their assumed luminosities. The method works assuming all type Ia supernovae have the same luminosity curves over time (which is a fair assumption due to most of them having similar masses and compositions when they occur). However, recent evidence shows that a carbon-based white dwarf might have a different luminosity curve from, say, a silicon based white-dwarf when it explodes, so this assumption may be false.

Klockan3

Sweden2866 Posts

April 07 2009 08:34 GMT

#65

On April 07 2009 12:12 micronesia wrote:

Show nested quote +

1: light is affected by gravity, but only when the gravity is strong; in most cases light is virtually unaffected. The way Einstein's general relativity was partially confirmed was... they looked along the edge of a large object in space to see if they could see the stars behind it.... according to the geometry, the stars should have been visible along the edge of the large object, but they couldn't see the stars. This was because the light coming from the distant stars which was slated to pass by the large object was pulled towards it like a meteor.

2: Frequency of light (color) very rarely changes aside from a doppler shift.

1: Light is always effected by gravity and as you could have guessed gravity pulls with a force according to the photons mass E=mc^2. This causes gravity doppler shifts and also gravitic lensing and it is very easy to derive this intuitively since otherwise you could destroy or create energy.

What however is only noticeable on very strong gravity fields are the effects described by general relativity's version of gravity.

On April 07 2009 15:12 Rekrul wrote:
All men want are holes. Some men find them on earth. Others have to look into outer space.

Pretty sure that the force of attraction of space holes are stronger than the holes on the earth!

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