Astrophysics 13 - The Big Bang Theory

What does the cosmological principle say the universe is on a large scale?

Homogeneous (the same everywhere)

Isotropic (has no centre)

What did Hubble realise about galaxies using red shift.

The further away an object is, the more red shift it experiences.

What does Hubble’s law show?

The universe is expanding.

Give the equation for Hubble’s Law.

Recessional velocity (km s^-1) = Hubble Constant (km s^-1 Mpc^-1) x distance (Mpc)

v = Hd

Explain the Big Bang Theory.

The universe started as very hot and very dense, and has been expanding ever since.

Explain how astronomers came up with the Big Bang Theory.

As the universe is expanding and cooling, it must have been much hotter and denser.

How can Hubble’s constant be used to estimate the age of the universe?

Assuming the universe has been expanding at the same rate for all time, the age of the universe can be estimated by one over the Hubble constant.

t = 1 / H

What is the issue with estimating the age of the universe using Hubble’s constant?

The universe’s expanse seems to be changing.W

What concept causes the expansion of the universe to accelerate?

Dark energy.

Explain the cosmic microwave background.

When the Big bang occured, loads of EM radiation should have been emitted, and still exist today.

Due to the expansion of the universe, we detect microwave radiation relatively uniformly from all areas of space.

How does helium abundance link to the big bang?

The large abundance of helium has long puzzled astrophysicists, but the Big bang resolves this as the early universe was very hot - hot enough to fuse hydrogen into helium.