AMA | October 2024

5194.611 - 5214.862 Sean Carroll

You run into the cosmic microwave background. You run into the moment in time when the universe was opaque. And every year, that moment gets to be one year in the past, okay? One year further into the past, and therefore you can see a little bit farther. Because the universe is expanding and changing its size in between now and then, it's not exactly a one-to-one map. years to light years.