Redshift measurements, among others, and it's not just expanding, it's accelerating. Better question is why... currently we have no f-ing idea. My money is on something like anti-gravity or repulsive gravity.
the uniquely human ability to move to higher and higher levels of abstraction without limit. Animals may have multiple levels of abstraction, but their abstractions must stop at some finite upper limit; this is not so for humans: "
Hi rod, I can't understand the connection between the principle of equivalence and redshift, can you explain a bit more, please.Trying to find out if there is experimental verification of photons red-shifting as 3D space expands other than the interpretation based upon the principle of equivalence from GR, used since the 1930s or so based upon redshifts in galaxies based upon Edwin Hubble et al. Is there measurements showing New Horizons transmissions, redshift on their way to Earth? Is there particle accelerator experiments in labs that show photons redshift as they move along in the lab? Hawkstein said "Redshift measurements, among others..." The redshift interpretation is principle of equivalence, not direct, experimental verification, e.g. *others*.
Hi Cat, in my post above, rather than post 7, I should have used a quote from rod in post 5, as below:Hi David
Whilst waiting for Rod to reappear, you will find a vast amount if you search:
Principle of equivalence red shift.
On another matter, what is your view on objects appearing to remain the same size whilst the Universe is expanding? If everything expanded equally we would notice nothing and so not know the Universe was expanding. If our measuring rods expanded equally with the Universe then they could not measure the expansion. Problem?