Does your brain hurt right now? Unless you’re an astrophysicist, watching the video below should make your brain hurt if it isn’t already.
The universe is an amazing thing, expanding and shifting in ways that make measuring the distances between stars and galaxies extremely complex. It’s not a one-step process – all of the data from different forms of distances measurement must be combined to form a broader picture of how far objects are from the Earth.
That’s the gist. The video goes into much more detail but not so much detail that you need to (literally) be a rocket scientist to understand it.
The video embed is apparently broken.