Ask Ethan: Will The Cosmic Microwave Background Ever Disappear?
As the Universe ages, will it eventually fade away entirely?
The earliest signal we’ve ever directly detected from the Universe comes to us from shortly after the Big Bang: when the Universe was merely 380,000 years old. Known today as the Cosmic Microwave Background, it’s alternatively been called the “primeval fireball” or the Big Bang’s leftover glow. It was an astonishing prediction dating back to George Gamow all the way in the 1940s, and it shocked the astronomical world when it was directly detected back in the 1960s. Over the past 55 years, we’ve measured its properties exquisitely, learning a tremendous amount about our Universe in the process. But will it always be around? That’s what Jürgen Sörgel wants to know, asking:
“The cosmic microwave background (CMB) was generated 380.000 years after the big bang, when the universe became transparent. The photons we will measure next week were generated a little bit further away from the position we had at that time compared to the photons we measure today. Our future is infinite, but the universe at year 380.000 was finite. Does that mean that the day will come when [the] CMB will disappear?”
It’s a simple question with a complex answer. Let’s dive in to what we know.
