The universe expands from an unimaginably hot and Houston Astros Blooming Baseballs Shirt speck (perhaps a singularity) with all the known forces unified. In a tiny fraction of a second tremendous changes are unleased. The strong force separates from the electronuclear. The weak force then separates from the electromagnetic. ~1 microsecond into this process Quarks are confined within hadrons. 1 millisecond in hydrogen nuclei are formed. 1 second in neutrinos begin to interact with other particles. At about the 3 minute mark helium nuclei are formed. 379,000 years in, the plasma cools enough for stable atoms to form and photons are released from this veil forming the Cosmic Background Radiation we see today. It’s 100 million years before the first stars can form, many generations of stars are busy creating the heavy elements necessary for life as we know it from the process of fission (both during the life of the star and during nova, supernova, and stellar collisions including those of neutron stars). All of these things almost certainly had to happen before life could form. So that’s somewhere around 1 billion years later before there is likely to be a place that is hospitable to life as we know it. But that’s even before galaxies have formed so that may be way too early, we just don’t know for certain.
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A Scarlet Spider Spider Man 2099 and Spider Woman The Powerpuff Girls Power Elite Spideys cartoon shirt – though somewhat indirect and subtle – method used for stars that do not fit into these categories (which is the majority of them, at least in our own galaxy) is as follows: First deduce the likely temperature and size of the star from its dominant colour and the atomic spectra present in its light (temperature is related to colour, and different chemical elements are produced under different conditions of temperature and pressure, which in turn depend on the mass and age of a star). From these we can work out the likely luminosity. From the luminosity we can deduce the stars absolute magnitude [1] (i.e. how bright it would appear at a standard, fixed distance of 10 parsecs from us). Comparing this with the star’s apparent (i.e observed) magnitude, we can then calculate it’s actual distance from us. To me, this method of deducing a star’s distance from us merely by studying its light, and then doing a few calculations based on thermodynamics, nuclear physics, atomic physics and stellar dynamics, represents one of the most beautiful examples of the power of human ingenuity and careful, deductive reasoning in the history of science.
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