Hacker News Reader

Comment by dwild | Hacker News Reader

> In the 1st second, the ant moved 10mm. But in the next four seconds you blew up the balloon, so that 10mm of rubber is now 70mm long. The total distance from the ant's starting mark to her end-point can now be well over than 70mm, even though she only walks at less than 10mm/second.

Thus the expansion isn't caused by the movement of the photon but from something else? Then what caused that movement in the first place? And what cause the expansion?

View on HN

You're right; the expansion of the universe is not related to photons. It's caused by the pressure of dark energy. There are some hypotheses but no one knows for sure what dark energy is.

If I understand correctly, the theory is that spacetime itself was created by the big bang. As-in, space, and time itself didn't exist prior to the big bang.

And and expansion is a lengthening of something within a frame of reference. What is the frame of reference?

The visible galaxies.

That is we see red-shifts when we observe distant objects. And comparing that to other distance estimates, we see that far away things are more red-shifted. As if they are moving away from us.

When we build cosmological models to explain this, we could choose reference coordinates for time and space in different ways. But if we choose to define time and distance in the usual way then we get a picture in which the distances between all galaxies is increasing with time.

Reply on news.ycombinator.com