Cosmology theory

[adrianos]

Can someone tell me how are cosmology theories usually tested ?

[ajb]

There is a branch of science called observational cosmology.

 

The usual tests of a cosmology theory include

 

i) Observed ratio of light elements.

ii) The CMBR and its anisotropies.

iii) Hubble's law.

iv) Galactic distributions.

[PhysBang]

Can someone tell me how are cosmology theories usually tested ?

The most common way of testing is to look at how the contents of the universe show signs of the geometry of the universe. Because, through general relativity, gravity works through geometry, looking at the overall geometry of the universe and the change in that geometry over time give us information about the contents of the universe and vice versa.

 

So, for example, looking at the way that light behaves as it reaches us from far away gives us information about the expansion of space.

 

Other ways of testing tend to be more indirect methods of the first. For example, looking at the distribution of light elements in the universe (hydrogen, helium, and lithium) gives us a restriction on the possible history of the universe, including the past geometry and the possible changes of that geometry in the past (since the changes control how much hydrogen would have turned into helium and lithium).

 

Looking at the way structures form in the universe also looks at the overall geometry. The way that clumps of matter break away from the whole to form galaxies and galaxy clusters depends on what the overall amount of matter is and how that influences the overall geometry of the universe.

 

 

I like to recommend Ned Wright's cosmology tutorial on matters like this. http://www.astro.ucla.edu/~wright/cosmolog.htm

[michel123456]

Observing & testing are the same?

[insane_alien]

Observing & testing are the same?

 

they can be.

 

it is impossible to test most cosmological theories in the lab due to scale issues. therefore, we must look for naturally occuring situations that are as close as possible to how you would set up an experiment to test a thoery.

 

for instance, one of the tests for gravitational waves is to accelerate large masses in a regular fashion and try to detect the waves generated(if there are any). so what we do is look for massive objects orbiting each other very close together, blackholes, neutron stars etc.

[FooFiFum]

insane_alien - Re gravitational waves

 

Supernova rapidly convert rather large amounts of mass into energy.

Accordingly, the gravity of said supernova would suddenly reduce accordingly. Are these the sort of gravitational waves you are looking for?

[insane_alien]

insane_alien - Re gravitational waves

 

Supernova rapidly convert rather large amounts of mass into energy.

Accordingly, the gravity of said supernova would suddenly reduce accordingly. Are these the sort of gravitational waves you are looking for?

 

well, it is one potential source but it has a very short window of opportunity. a more reliable source with a larger window is two neutron stars or blackholes orbiting very close to each other. the emission of gravitational waves should cause the orbits to decay.