10 Cosmology Free Online FlashCards

What does cosmology study?

Cosmology studies the universe as a whole, including its origin, large-scale structure, evolution, and possible future.

What does expansion mean on cosmic scales?

On very large scales, space expands, increasing the average distance between faraway, unbound galaxies. This is not an outward flight from a central point.

What causes cosmological redshift?

As light travels through expanding space, its wavelength stretches, shifting a galaxy’s spectral lines toward the red end of the spectrum.

Why does looking farther away mean looking further into the past?

Because light takes time to reach us, observing more distant objects means seeing them as they were further in the past.

What early state does the Big Bang model describe?

The Big Bang model describes the observable universe evolving from an extremely hot, dense state about 13.8 billion years ago.

Name three observations explained by the Big Bang model.

The model explains cosmic expansion, the abundance of light elements, and the cosmic microwave background.

What is cosmic inflation, and what may it help explain?

Inflation is a brief early period of extraordinarily rapid expansion. It may explain large-scale uniformity and the small variations that later grew into cosmic structure; its cause is unknown.

When and how was the cosmic microwave background released?

About 380,000 years after the Big Bang, the universe cooled enough for neutral atoms to form. Light then traveled freely; that ancient light is the CMB.

How did tiny CMB variations contribute to cosmic structure?

Tiny CMB temperature differences correspond to slight density differences in the young universe. Gravity amplified these variations, helping matter gather into cosmic structures.

What did nuclear reactions produce in the universe’s first minutes?

During the universe’s first minutes, nuclear reactions produced most primordial hydrogen and helium, plus small amounts of other light elements.

What is dark energy, and what is one leading explanation for it?

Dark energy is the name for whatever drives accelerated cosmic expansion; its nature is unknown. One leading explanation is a constant energy density associated with space itself.

What future does the Big Freeze describe?

If dark energy remains nearly constant, the universe is expected to keep expanding and become colder and more dilute, a projected future called the Big Freeze or heat death.