3. Distances Flashcards
1
Q
What is the actual distance photons travel?
A
ct
2
Q
What is Dphys?
A
Comoving radial distance photons travel
3
Q
If K=0, what is Dphys equal to?
A
r
4
Q
Integral equation for Dphys?
A
Dphys = (t1 to t0) ∫ cdt/a if K≠0
5
Q
What are the 2 important limits in the redshift-distance relation?
A
z«1: Dphys = cz/H0 and can set Dphys = r
z→infinity: Dphys = R_horizon,0 = 2c/H0Ω0
6
Q
How is comoving photon horizon distance defined?
A
R_horizon = 0 to t ∫c dt/a
7
Q
What is photon horizon?
A
Furthest point of origin of a photon in comoving coordinates
