- #1
jcap
- 170
- 12
Sorry to go on about this topic. I'll get it out of my system soon!
The flat FRW metric is given by:
$$ds^2=-c^2dt^2+a(t)^2dr^2$$
If we take ##dt=0## then we get:
$$ds=a(t)\ dr$$
The proper distance between co-moving points scales with ##a(t)##. Thus we find that space expands.
If we take ##ds=0## to find the null geodesic followed by a light beam we get:
$$c\ dt=a(t)\ dr$$
Surely this implies that cosmological time intervals expand in the same way as space intervals?
The flat FRW metric is given by:
$$ds^2=-c^2dt^2+a(t)^2dr^2$$
If we take ##dt=0## then we get:
$$ds=a(t)\ dr$$
The proper distance between co-moving points scales with ##a(t)##. Thus we find that space expands.
If we take ##ds=0## to find the null geodesic followed by a light beam we get:
$$c\ dt=a(t)\ dr$$
Surely this implies that cosmological time intervals expand in the same way as space intervals?