PDA

View Full Version : Question that is driving me crazy

woodguard
2005-May-30, 11:48 PM
Because of the red shift I know the universe is expanding away from us, but what proof is there that the universe expanding uniformly.

Ilya
2005-May-31, 12:59 AM
Red shift is extremely uniform in all directions.

Kristophe
2005-May-31, 01:02 AM
Evidence. The word you're looking for is evidence, not proof. Proofs are for mathematicians and lawyers.

We suspect things are moving away from us because they exhibit a red shift. The red shift is proportional to the velocity at which the objects move away from us. So, if we see objects measured to be the same distance away from us showing the same redshifts, we say they're moving away with the same velocity. Doing this farther and farther out, we see that red shift is also proportional to the distance an object is away from us. This can be observed to be spherically symmetric, and so the universe is seen to be expanding at the same rate in all directions.

lti
2005-May-31, 09:24 AM
apart from anomoles like the andromeda galaxy?

Champion_Munch
2005-May-31, 10:04 AM
apart from anomoles like the andromeda galaxy?

Do you mean 'anomalies'? The reason that Andromeda is actually blue-shifted instead of red-shifted is because it's moving towards us.

We suspect things are moving away from us because they exhibit a red shift

What Kristophe stated was accurate.

with regards

TriangleMan
2005-May-31, 11:06 AM
apart from anomoles like the andromeda galaxy?

Many members of the Local Group of galaxies, such as Andromeda, are moving towards us due to gravitational attraction. When (Hubble?) was doing his study of redshift in the 20s he noted that only some galaxies that were close to the Milky Way exhibited blue shift.

Champion_Munch
2005-May-31, 11:13 AM
apart from anomoles like the andromeda galaxy?

Many members of the Local Group of galaxies, such as Andromeda, are moving towards us due to gravitational attraction. When (Hubble?) was doing his study of redshift in the 20s he noted that only some galaxies that were close to the Milky Way exhibited blue shift.

Sure was Hubble. \:D/ Although back then it was thought that galaxies were just nubulae in our own Milky Way. :P

with regards