But we don’t actually know if the density of dark energy is truly constant. We know that it’s nearly constant, but it could be changing slowly over time. Knowing what is true will have profound consequences on predictions of the future evolution of the universe.
The more distant an object is, the longer it takes for light to get to us. In a very real sense, DESI is a cosmological time machine with the ability to peer into the universe’s distant past.
By taking photographs of galaxies both near and far, astronomers will be able to study not only how the shapes of galaxies have changed over the last 11 billion years, but how individual galaxies have clustered together over time. This will give us clear and inarguable information about how the cosmos grew and evolved. And by measuring the position and velocities of a vast swath of galaxies, astronomers will be able to determine in detail how the expansion of the universe unfolded.
This will result in a clear vision of the future of the universe. Timeless questions of philosophy and theology could be definitively answered. The next five years will be an exciting time for astronomy buffs.