As far as I know there was a period of inflation in the early universe where space expanded faster than the speed of light. 1. Was the speed of light then also 299,792,458.00 m/s? Can one prove that the speed of light has always been constant? 2. Apart from this period of inflation, space is still expanding faster. This extension is measured in kilometers per second per megaparsec. This means that a point in space 1 megaparsec away from us is moving away from us at X km/s. A point 2 megaparsecs from us is moving at 2X km/s away from us. The farther from us a point is, the faster it moves away from us. If we assume that the universe is infinite, then there is a point at an infinite distance from us that is moving away from us at infinite speed. Is this possible? If this is possible, what about objects (planets and the like) moving at this speed? Or do they move (is a displacement of space also a displacement of the object at that point in space?)
Answer
Within space, nothing can move faster than the speed of light.
But here we are talking about an extension of the space itself. It is the space in relation to which our physics takes place that becomes larger, so the reference frame. And an expansion does indeed mean that the speed at which two points in space move away from each other increases in proportion to their distance. And from a certain distance, that removal speed is greater than the speed of light. This is bizarre, but it does not contradict the condition that speeds greater than the speed of light are not possible inside space.
We see this expansion as Hubble-Lemaitre’s law, which states that the removal rate (or rather, the redshift) of distant objects increases proportionally with distance. The light becomes redder, at a lower frequency, in the same way that the tone of an ambulance sounds lower as it moves away from us, the so-called Doppler effect. Hubble-Lemaitre’s law is not, strictly speaking, a Doppler effect: it is not the ambulance moving away from us; no, both the ambulance and ourselves are standing still, but the street is getting longer.
Answered by
Prof. dr. Christopher Waelkens
Astronomy
Old Market 13 3000 Leuven
https://www.kuleuven.be/
.