Physics 12: Astrophysics and Cosmology

Proof required

Link the public repo with the 8.286 problem sets, then the quizzes timed written up (a typeset PDF, LaTeX source or notebook), and show the self-check: which answers matched and how you fixed the ones that did not.

What gets checked

• Scale factor and redshift are related correctly.
• Units are consistent across cosmological distances.
• Quizzes are marked against their solutions.

Common mistakes

• Answers copied from the key with no working.
• Wrong units or missing signs.

Powstik Guide

A public write-up of the 8.286 problem sets, then the quizzes timed, with the self-check shown.

Steps

1. Study the linked course and chapters.
2. Solve the problems on your own first.
3. Check them against the self-check and rework the misses.
4. Typeset the write-up (LaTeX or a notebook) in a public repo.
5. Ask someone who knows physics to check it.

README
Physics 12: Astrophysics and Cosmology, unit 1: The expanding universe
Problems:
Self-check result (matched / reworked):
What I got wrong first and why:

What gets sent back

• No working shown.
• The self-check result is missing.

Resources

What a verifier looks for

• Scale factor and redshift are related correctly.
• Units are consistent across cosmological distances.
• Quizzes are marked against their solutions.
• Is the physics right, not just the final number?

You'll sign in first, then come straight back here.

Proof required

Link the public repo with the analysis notebook and the data's source, the result with its uncertainty, and a README that says what you did and what limits the result.

What gets checked

• The fit gives Ωm with an uncertainty from the published errors.
• A model with no dark energy is fitted too, and the two are compared.
• The result is compared with published values (about 0.3).

Common mistakes

• A result with no uncertainty.
• Code or data that cannot be rerun from the repo.

Powstik Guide

An analysis of the Union2.1 type Ia supernova data that fits flat universe models and estimates the matter density Ωm, in a public repo.

Steps

1. Write down what you expect before you start.
2. Fit distance modulus against redshift for flat models with matter and dark energy, using the published errors, and look at the residuals.
3. Work out the uncertainty from your own data.
4. Compare with the accepted value and explain any gap.
5. Write the README and ask someone who knows physics to check it.

README
Physics 12: Astrophysics and Cosmology — Measure the accelerating expansion from supernovae
What I expected:
Method:
Result (value ± uncertainty):
Accepted value and comparison:
What limits the result:

What gets sent back

• No uncertainty, or one that is guessed.
• Code that does not run.

Resources

What a verifier looks for

• The fit gives Ωm with an uncertainty from the published errors.
• A model with no dark energy is fitted too, and the two are compared.
• The result is compared with published values (about 0.3).
• The uncertainty is worked out from the data or runs (spread of repeats, instrument limits, fit errors or a range of inputs), not guessed, and it is shown on the result.
• Is the physics right, and could someone rerun it from the repo?

You'll sign in first, then come straight back here.