bangstrom » September 26th, 2019, 9:43 am wrote:Since 1968, the length of a meter has been defined by convention as the distance light travels in 1/299,792,458th of a second and the duration of a second is defined as the time it takes light to travel 299,792,458 meters and c is a constant ratio of 299,792,458 meters per second. The units of time, distance and c are all mutually defined so, if clocks tick faster, the length of a meter must grow shorter if the value of c remains is to remain the same.

Thank you for your comments. I have read your post carefully, and I understand the points about inertial frames and the constancy of c. However, while I can conceptually grasp the idea of expanding (or contracting) space, I have difficulty in understanding what it means for time to quicken (or slow). What does it mean to say that 'time itself' accelerates 'over time' (?) in the same inertial frame? Clocks give more ticks per – what? It cannot be 'per second' if the length of a second is the very thing that changes.

You say elsewhere in your post: "We have no universal reference for either one [space or time] that could tell us which one or both are changing". What would such a reference look like? What would its necessary properties be? What units, formulae etc would apply to it?

Here’s the rub. The WMAP data gave the universe an equivocal cosmic age of 13.766 billion years based on the Hubble rate of growth of 73.5 kilometers per second per megaparsec but the Hubble rate is a cosmological ratio of distance to time as is the constant c so the Hubble rate varies in sync with the expansion of the universe while remaining the same within each individual reference frame. The consequence of this is that the measured 13.766 billion year age of the universe will remain the same 10 billion years from now just as it was 10 billion years in the past.

Is there general agreement about this?