The physics of the large and small has completely transformed in both the last 100 years, and the last ten. We can look, with light and electromagnetic waves, back in time to a point where we receive a regular dose of photons (seeing) to about 300,000 years after the big bang.

We get photons, in steady measure, that have never been interrupted in their path for 13.7 billion years.

At that time (300,000 years after the big bang) the universe started emitting light, and we could see. Before that time the universe was opaque to photons. During a phase called recombination decoupling occurred, hydrogen and helium atoms began to form and the density of the universe falls causing the photons to evolve independently from matter, starting their long journey towards us.

Cosmic microwave background radiation Before that time, we can only infer - mostly from the pattern drawn by the cosmic background radiation. We can measure back to a point very close - (much less than a second) to unobservability.

But, given those initial conditions, (10 ^-43 seconds) we have perfect math that describes conditions as they are today. From multiple independent sources, we have a good idea that baryonic mass (thats us, and the stars) is less than two percent of a lot of other stuff, like dark matter (clumpy, massy, but invisible) and dark energy, which uniformly fills space, and is a property of it.

You heard that right - we are not the centre of the universe. We cannot even see the big guys. The names "dark matter" and "dark energy" serve mainly as expressions of our ignorance, much as the marking of early maps with "terra incognita".

One of these independent sources is the Galaxy rotation curve, where we see that galaxys rotate like a wheel, all together, and not like a plug-hole or the solar system, where planets far out rotate slower than those close in. Another is Gravitational lensing.

General relativity points to a Singularity at the Big Bang. This is generally a sign for a missing piece in the theory. We don't know why we got that set of initial conditions (they seem suspiciously flat) but if we accept them, we have solid mathematics that describes most of what happened since.

Remember when the church had to acknowledge that earth was not the centre of the universe ? The Singularity associated with the Big Bang indicates that our theories are still incomplete, and there are other momentous discoveries still to be made.

Dr. Michael Turner even suggests that cosmology is now more interesting than science fiction.