What Is Cosmological Redshift?
Why the pop science explanation is wrong
Those who pay attention to such things know that in the first part of the twentieth century our conception of the universe expanded dramatically. Prior to then, we believed our galaxy was the universe and we believed it had always been as it is today. The universe was eternal, unchanging, unmoving. There was no particular reason to believe this, but there was no particular reason to believe anything else either. And so we thought we lived in a fairly modest and predictable universe.
Even Einstein, whose 1915 equations of General Relativity showed that a universe could not be static but instead had to be dynamic, either expanding or contracting, clung to old notions and famously scolded Georges Lemaître when the latter attempted to present his findings (which showed the universe must have begun in a dense single point and then expanded outward) to the Grand Old Man of physics in 1927.
But science is not about theory alone; empirical observations often trigger the abandonment of old ideas and the adoption of theories that better explain what is seen to be happening. Even as Einstein was dismissing Lemaître’s physics as “execrable,” the astronomer Edwin Hubble was making some astonishing observations that would cause Einstein, along with nearly all other physicists and…
