Until the 1990s, there were few reliable observations about movement at the scale of the entire universe, which is the only scale dark energy effects. So dark energy could not be seen until we could measure things very, very far away.
Adam RiessIt's everywhere, really. It's between the galaxies. It is in this room. We believe that everywhere that you have space, empty space, that you cannot avoid having some of this dark energy.
Adam RiessYour chemistry high school teacher lied to you when they told you that there was such a thing as a vacuum, that you could take space and move every particle out of it.
Adam Riess