Nov 14 – Galaxies and Hubble's Discoveries

A set of flashcards summarizing key concepts from the lecture on galaxy formation, Olber's Paradox, Hubble’s discoveries, and the expansion of the universe.

What is the most likely process of galaxy formation similar to?

The process of star formation, but on a larger scale.

What is Olber’s Paradox?

The question of 'Why is the night sky dark?' despite an infinite universe.

Who first attributed Olber's Paradox in 1823?

Heinrich Olbers, a German astronomer.

What does infinite space and infinite time equal in Olber's Paradox?

Infinite light.

What was Edgar Allen Poe's contribution to the discussion of Olber's Paradox?

He argued that if stars were endless, the night sky would be uniformly luminous.

What significant discovery did Edwin Hubble make in 1931?

He measured the distances to spiral nebulae and found that most are moving away from us.

What is the relationship that Hubble discovered between distance and recession velocity of galaxies?

More distant galaxies are moving away faster, indicated by Doppler redshift.

What is Hubble's Law?

It describes the expanding universe with a constant H₀, representing the rate of recession of galaxies.

What is Hubble Time based on Hubble’s Constant H₀?

Approximately 13.8 billion years.

How does the expansion of the universe work?

Every galaxy moves away from every other due to the expansion of space itself.

What is the difference between cosmological redshift and Doppler redshift?

Cosmological redshift is due to the expansion of space, stretching the light.

What allows astronomers to estimate the distance to celestial objects using Hubble’s Law?

Determining the redshift of those objects.

What concept explains why the light from distant objects reveals their past state?

Lookback time; light takes time to travel from those objects to us.

What is the conclusion about why the night sky is not fully lit?

The universe is not infinite, particularly in terms of time.

What did Poe's insights suggest about the universe's structure?

The existence of vast voids in the universe that are due to immense distances.