NO MATTER HOW HIGH YOU STACK THE BOLOGNA IT DOESN'T BECOME STEAK:

Welcome to another installment of our series exploring emerging and potentially serious challenges to the standard model of cosmology -- humanity's best and most expansive scientific understanding of the Universe. In a recent paper, astrophysicist Fulvio Melia articulated a list of problems that, for him, indicate something fundamental is wrong with the standard model. Melia is not alone in wondering whether the standard model's time might be up. The phrase "crisis in cosmology" is finding its way into a growing number of blogs and podcasts. But what is behind this crisis, and how seriously should we take it? 

Today we will take a look at another entry on Melia's list, one that has grabbed a good share of headlines: the problem of galaxies and what is called the age-redshift relation.

The story of cosmology given to us by the standard model says that about 400,000 years after the Big Bang, electrons and protons found each other to create the first hydrogen atoms. Before this, they had been running free along with the photons that would soon become the cosmic microwave background radiation. Once this recombination into hydrogen occurs, the Universe is largely composed of a fairly smooth gas of these atoms -- with some helium around, too -- and the left-over background radiation. 

Now gravity can get to work within perturbations -- small regions of overdensity in the hydrogen gas -- and slowly collapse them to form the first stars. It is inside these first stars, which are formed only of hydrogen and helium, that nuclear fusion begins to forge all the heavy elements we know today. Elements like carbon and nitrogen play an important role in the story of galaxy formation. That is because these are the elements that can absorb heat from surrounding gas and emit photons that cool that gas. This cooling process will be critical in helping gas coalesce into galaxies. 

Eventually these first-generation stars explode, and the resulting supernovae seed the gas that surrounds them with heavy elements. Each supernova, along with black holes which are also forming, pumps ultraviolet radiation into the Universe. This strips electrons from hydrogen atoms, making the Universe more and more transparent to UV radiation. After the Universe has run through a few generations of stars, there are enough heavy elements and UV radiation around to feed the formation of galaxies. Stars and vast quantities of gas collapse into gravitationally bound entities to pull these first galaxies together.

This is a good story, and observations confirm key parts of it. The problem comes when it is placed within the cosmological context of the expanding Universe. 

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