Quasars are intense sources of radio energy that appear as almost starlike points. For this reason, when they were first discovered in 1939 they came to be known as quasi-stellar radio sources, or quasars for short. Early on it was not entirely clear what these objects were. They were incredibly energetic, and they also tended to have very large redshifts, which implied that they were very far away. It was also noticed that quasars weren’t randomly scattered across the sky, but instead tended to clump together in groups.
Sword of Damocles
According to legend, when Damocles declared that his king, Dionysius, must have a posh and easy life, Dionysius offered to trade places with Damocles. There was only one catch. Dionysius decreed that a sword be suspended over the throne by a single horse hair, so that Damocles would always know the peril of being king. Since then the Sword of Damocles has come to represent a threat of doom that could strike without warning. While the prospect of living under a hanging sword doesn’t seem pleasant, stories of impending doom are quite popular, particularly within popular science.
Three Peaks at the Big Bang
One of the big points of evidence in support of the big bang is the cosmic microwave background (CMB). It is often described as the afterglow of the primordial fireball, but it is much more than that. As we make better observations of the CMB we not only gather evidence of the origin of the universe, we also get an indication of the specific nature of our universe. One of the ways we see this is through what’s known as the three peaks.
Variables of Nature
Within physics there are certain physical quantities that play a central role. These are things such as the mass of an electron, or the speed of light, or the universal constant of gravity. We aren’t sure why these constants have the values they do, but their values uniquely determine the way our universe works. For example, if the mass of electrons were smaller, atoms would be smaller. If the gravitational constant were larger, you’d need less mass to create a black hole, and neutron stars might not exist.
The Lithium Experiment
One of the big successes of the big bang model is its prediction of elemental abundances. The first elements were produced in the early moments of the universe through a process known as baryogenesis. This process is very complex, and it is highly dependent upon the temperature and density of the universe at that time. Change the temperature a bit one way or the other, and the initial ratio of primordial elements would be different. Knowing the temperature of the early universe, we can predict the amount of hydrogen vs. helium produced by the big bang, and this agrees fairly well with observation.
Anomalous Anomalies
When objects get hot, they give off light. You can notice this with glowing coals, incandescent light bulbs and the like. It turns out the light a hot object gives off follows a specific pattern known as a blackbody spectrum. If you look at the intensity of a blackbody spectrum as a function of its color (or wavelength), you notice shape of the function depends on the temperature of the object giving off light.
CANDELS in the Dark
If you look at different galaxies in the universe, you begin to notice that they seem to fall into some broad types. Edwin Hubble was the first to categorize galaxies into different types, and he divided them into ellipticals, spirals and irregulars. He then further broke these categories into subgroups, and arranged them into what is now known as Hubble’s Tuning Fork diagram.
Flat Stanley
One of the things we often say about the universe is that it is “flat.” Of course this usually raises the question about what that actually means. How can space be flat? Sure, a surface such as a table can be flat, but space?
Like a BOSS
Dark energy is perhaps the least understood aspect of modern cosmology. We first obtained evidence of its existence via the 1998 discovery that the universe is not only expanding (which we’ve long known), but that the rate of expansion is accelerating. This was done by observing the redshifts of distant supernovae, and won the discovers a Nobel prize. Since then observations of the cosmic microwave background have found that dark energy makes up about 70% of the matter-energy in the universe. This is consistent with observations of acceleration.