Question
The CfA’s LEDA (“LEE-duh”) experiment detects the 21-centimeter lines of photons emitted from this cosmological period. For 10 points each:
[10h] Name this period preceded by recombination, in which the universe was transparent, but the only sources of photons were photon decoupling and hydrogen’s spin-flip transition.
ANSWER: cosmic dark ages
[10e] LEDA detects 21-centimeter lines at values of 15-to-30 for this quantity, denoted z. This quantity measures the increase of wavelengths towards a namesake color.
ANSWER: redshift [prompt on Doppler shift]
[10m] The dark ages were followed by this period characterized by the gravitational stripping of electrons from neutral hydrogen. The earliest stars and black holes formed during this period.
ANSWER: reionization [or hydrogen reionization]
<Ganon Evans, Science - Astronomy> ~23877~ <Editor: David Bass>
Data
Summary
| Tournament | Edition | Exact Match? | Heard | PPB | Easy % | Medium % | Hard % |
|---|---|---|---|---|---|---|---|
| 2024 PACE NSC | 06/08/2024 | Y | 36 | 10.00 | 92% | 3% | 6% |