History of the Universe

In the classic 1977 book The First Three Minutes, Nobel Prize-winner Steven Weinberg laid out the physics of what happened just moments after the Big Bang that created our universe. As with most things in physics, that certainly wasn't the end of the story, as attested by the update and reissue of The First Three Minutes in 1993.

Pre-Matter Soup
Until recently, the first hundredth of a second was a bit of a mystery, leaving Weinberg and others unable to describe exactly what the universe would have been like. New experiments at the Relativistic Heavy Ion Collider (i.e. atom smasher) at the Brookhaven National Laboratory on Long Island have provided physicists with a glimpse through this curtain of high energy, so they can directly observe the sorts of behavior that might have been taking place in this time frame.

At these energies, the quarks that comprise protons and neutrons are not yet joined together, and a dense, superhot mix of quarks and gluons, with some electrons thrown in, is all that can exist in the microseconds before it cools (i.e. looses energy) enough to form into the sort of matter particles we observe today.

Pre-Galactic Galaxies
Fast forwarding to after the existence of matter, more information is coming in on the formation of galaxies. It is believed that the earliest galaxies were tiny "dwarf galaxies" that released so much radiation they stripped gas atoms of their electrons. This gas, in turn, heated up and expanded, and thus were able to obtain the mass needed to form the larger galaxies that we know today.

Current telescopes are just now beginning to have the capacity to observe the galaxies from this distant time. Studying the light from quasars, they observe how it passes through the intervening gas clouds. The ionization of these gas clouds is determined by the number of nearby bright galaxies, and if such galaxies are spread around, the ionization level should be constant. It turns out that in galaxies from the period after cosmic reionization there are large fluctuations in this ionization level. The evidence seems to confirm the pre-ionization galaxies were less common and that the post-ionization galaxies have 100 times the mass of the dwarf galaxies. This research is reported in the May 18 issue of Nature.

The next generation of telescopes should be able to see the dwarf galaxies directly, which will help resolve the problem that many astronomical predictions in galaxy formation theory predict more nearby small galaxies than observed.

Related Physics Articles

• Fundamentals of Particles
• Largest Map of the Universe Created
• Not-So-Constant Constants
• Scientific American: "The First Few Microseconds"
• Science: "Emergence of the Galactic Heavyweights"