In the 1920s, scientists discovered that the Universe was expandingbased on measurements of the distances to galaxies and how redshifted their light was. In the 1990s, we learned that the Universe wasn’t simply expanding, but that distant galaxies are moving to greater distances at an accelerating rate. The underlying cause has been identified as dark energy, which is causing the Universe to disappear as time goes on.
It’s true: there are some 2 trillion galaxies within the observable Universe, and 97% of them are already beyond our reach, even if we left today at the speed of light. But even though we cannot reach them, we can still see them. Even more puzzling is this: new, never-before-seen galaxies are continuously revealing themselves to us as time goes on. We may not be able to reach the disappearing Universe, but we can still see it. Here’s how.