How does galactic redshift provide evidence for an expanding universe?

Light from distant galaxies is shifted to longer wavelengths, indicating they are moving away from us, which supports the model of an expanding universe.

What observation about distant galaxies supports the model of a uniformly expanding universe?

More distant galaxies have greater redshifts, indicating that recession velocity increases with distance.

How do you convert the Hubble constant from km s⁻¹ Mpc⁻¹ to s⁻¹?

Divide by the number of kilometres in a megaparsec (1 Mpc ≈ 3.09 × 10¹⁹ km).

What stage in the evolution of the universe involved the creation of quarks, electrons, and other fundamental particles?

The formation of fundamental particles occurred in the earliest moments after the Big Bang.

OCR A-Level Physics A H556

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Astrophysics and Cosmology

The expanding universe and the Big Bang

3 things to know
Papers 1, 2 and 3

Overview

Recall questions on redshift as evidence of expansion, units of the Hubble constant, the Big Bang theory, and the stages of the early universe including nucleosynthesis, recombination and the release of the CMB.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

When was the CMB radiation we observe today released?

Key term

In what two types of units can the Hubble constant be expressed?

Key term

What does the Big Bang theory propose about the origin of the universe?

Questions from this subtopic

Each one with the model answer underneath.

1
How does galactic redshift provide evidence for an expanding universe?
Model answer
Light from distant galaxies is shifted to longer wavelengths, indicating they are moving away from us, which supports the model of an expanding universe.
2
What observation about distant galaxies supports the model of a uniformly expanding universe?
Model answer
More distant galaxies have greater redshifts, indicating that recession velocity increases with distance.
3
In what two types of units can the Hubble constant be expressed?
Model answer
The Hubble constant can be expressed in km s⁻¹ Mpc⁻¹ or equivalently in s⁻¹.
4
How do you convert the Hubble constant from km s⁻¹ Mpc⁻¹ to s⁻¹?
Model answer
Divide by the number of kilometres in a megaparsec (1 Mpc ≈ 3.09 × 10¹⁹ km).
5
What does the Big Bang theory propose about the origin of the universe?
Model answer
The universe began from an extremely hot, dense state and has been expanding and cooling ever since.
6
What stage in the evolution of the universe involved the creation of quarks, electrons, and other fundamental particles?
Model answer
The formation of fundamental particles occurred in the earliest moments after the Big Bang.

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