Modern science believes that our universe is expanding from nothingness to infinite space. How is there nothing and then space all of a sudden? It’s an incredibly complex question that will give you a sense of wonder and slight fear at the same time. For the past 20 years, scientists believed this expansion of matter into nothingness was a product of what they call “Dark Energy” caused by supernovas and other things in our known universe.
Scientists have “inferred” the existence of Dark Energy based on the constant expansion of the universe.
PBS Space-Time gives a far more detailed description than I can ever hope to summarize for you completely, but this is essentially what has been theorized in a recent study: The universe is not expanding at a constant rate and goes through periods of accelerated expansion and periods of no expansion at all.
So we went from our best guess as to why the universe expands, to possibly back to square one. Matt O’Dowd isn’t completely convinced Dark Energy is no longer a thing, but he does agree it’s important to know about.