Transcript: An important test of the big bang model is some sort of verification of the reality of cosmic expansion. It’s possible that redshift may be non-cosmological in origin caused by some other phenomenon or property of light. The best test of the cosmological expansion, the reality of expanding space, is the prediction that the surface brightness of an object goes as one plus the redshift to the fourth power. Surface brightness is defined as the flux per unit area of an extended...

Transcript: The current expansion rate of the universe is given by the Hubble constant. Measurement of the Hubble constant was subject to an enormous effort over the past forty years culminating in the Hubble Space Telescope key project. In this huge collaboration involving hundreds of orbits with that precious facility, a series of measurements of the local universe involving Cepheid variables was used to derive the expansion rate. The answer was seventy kilometers per second per...

Transcript: The most sensitive test of the curvature of space uses the cosmic microwave background radiation. These microwaves were released three hundred thousand years after the big bang. The fluctuations in the microwave background were imprinted with a certain angular size, and depending on the shape of the universe, the fluctuations are either magnified or demagnified as they travel through billions of lightyears of space and billions of years of time to reach us. The universe...

Transcript: General relativity relates the dynamics of the expanding universe to the curvature of space. Thus space curvature is one of the most important things to measure about our universe, but it’s an extremely difficult measurement because the curvature is so subtle. In principle it would be possible to measure space curvature if there were objects of a fixed linear size in space. We could then measure how their apparent size varied with distance or redshift. But galaxies do not have...

Transcript: The big bang model is described by a small number of cosmological parameters. Astronomers talk about a world model, but in fact they’re talking about a description of the entire universe. If these parameters are measured, the entire history of the universe, past, present, and future, can be described although the detailed behavior of objects within the universe is too complex to be described in this way. Cosmological parameters require difficult observations, work at the limit...