Olbers’ Paradox: Solution

Last time we talked about Olber’s paradox— why the night sky is dark. And then if the universe has infinite number of stars, we argued every line of sight end(s) up with the stars so the night sky should be as bright as the daytime. But, the night sky, as we all know the night sky is dark, so, what is wrong? So today, the, we talk about the answer, the answer is the universe is not infinite. The age of the universe is not forever, but it’s 13.8 giga-years. So, we can see up to the 13.8 light years of giga, light years away, we can see up to the 13.8 light giga-years away, but not any farther. The universe ends there.

So, so there’s a limited number of stars in the universe. That’s why the night sky is dark. And, in addition, nowadays we know that the expansion of the universe, it’s accelerating. This will make distant stars even fainter, so that does not help expansion of the universe, does not help. And then, let’s look at the history a little bit here. Um, in (the) nineteenth century, the famous poet Edgar Allen Poe, the famous poet, and also a writer, suggested, already he associated the finite size of the observable universe resolved the apparent paradox. So, he’s not a scientist, he’s a writer, but he already knew the size of the universe is finite.

And the most surprising is that before that, Johannes Kepler, in 1610 already thought about this paradox, and then he thought this is an argument for a finite observable universe, or at least for an infinite number of stars. I like thinking about this Olber’s paradox because the night sky is dark, this is what everybody knows, we all know, even small children know the night sky is dark. But this darkness of the night sky is already telling us the size of the universe is not infinite. So, the, a lot of people believed the universe is infinite at the time of the Olber’s, but the night sky’s darkness, it’s already telling us the size of the universe is limited.

So there may be for simple observational things there may be a great hint to understand the universe. This is why I like this Olber’s paradox.