Info on tests done in the past for expanding universe

[scott22]

I am hoping that someone with broad knowledge of the physics literature can tell me when in the past tests were done on light coming from galaxies billions of light years away, tests that over time counted a decreasing number of photons from a single galaxy, or an increase in the wavelength of light from a single galaxy. It seems that an expanding universe would exhibit one or both of these characteristics, and I just assume these tests must have been done long ago. I am having no luck finding anything with the databases available to me and I was hoping someone could let me know where to look. Thanks.

 

[mathman]

The origin of the notion is due to Hubble. He observed that there appeared to be a correlation between red shift of light from galaxies and how far away they were.

http://en.wikipedia.org/wiki/Edwin_Hubble

 

[Bandersnatch]

The kind of evidence you're asking for doesn't exist, as it would require (currently)impossible accuracy to measure.

Consider a galaxy shining with light intensity I₀ that was 7 billion ly away 100 years ago, and is receeding at 0.5c. Over 100 years of observation the intensity of light emitted by the galaxy would fall according to the inverse square law by:
$\frac{I_{100}}{I_0}=\frac{R^2}{(R+ΔR)^2}$

ΔR is 50 ly, so
$\frac{I_{100}}{I_0}=0,999999986$
or 0,0000014% lower intensity. Good luck measuring that, especially for an object already very faint.


Measuring the changing redshift of a single object is a similar problem. The time scale for observation is just not enough.

The evidence for the Big Bang is collected using other methods. Here's a review:
http://www.talkorigins.org/faqs/astronomy/bigbang.html

The closest to what you want is described in the "Tolman tests" section, but it compares standard candles, not the same object at different times.

 

[Jon B]

Using the unshifted indicators in our local galaxy as a reference for the shifted spectrum of light from objects at the most extreme distances does not seem to take into consideration the affect that the gravity of our galaxy has on light. We can only observe what is in our local area and make assumptions based on that observation. Then we assume we are at the center of the universe and somewhere out there is an edge.

 

[pmacias]

There have been numerous tests and observations done in the past that support the idea of an expanding universe. One of the earliest pieces of evidence was the observation of redshift in the spectra of distant galaxies by Edwin Hubble in the 1920s. This redshift is caused by the expansion of the universe, which stretches the wavelengths of light as it travels through space.

In the 1960s, the cosmic microwave background radiation (CMB) was discovered, providing further evidence for an expanding universe. The CMB is a remnant of the Big Bang and its characteristics, such as its uniformity and the presence of small fluctuations, support the idea of an expanding universe.

More recently, observations of Type Ia supernovae in the late 1990s also provided strong evidence for an expanding universe. These supernovae are used as "standard candles" to measure distances in the universe, and their observed brightness was found to be consistent with an accelerating expansion of the universe.

In addition to these observational tests, there have also been theoretical developments, such as the theory of general relativity, that support the idea of an expanding universe.

Overall, the evidence for an expanding universe has been accumulating for decades and continues to be studied and refined by scientists. I recommend looking into the work of Hubble, the discovery of the CMB, and the observations of Type Ia supernovae for more information on the tests and evidence for an expanding universe.