Sorry to go on about this topic. I'll get it out of my system soon!(adsbygoogle = window.adsbygoogle || []).push({});

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?

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# Does time expand along with space?

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