(Correction) Radius of Observable Universe
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- I want to make a quick correction to the last video.
- It doesn't really affect the learning of the last video, but I just want to make sure that you understand
- that I got the math a little bit wrong in the last video.
- I said that, you know, you had this state 300,000 years--so we talk about the Big Bang happening
- 13.7 billion years ago.
- And then I talk about this state of affairs where we're maybe 30 million light years
- away from the edge of the observable universe, the current observable universe.
- And I said that this was about 300,000 years after the Big Bang. That's what I talked about in the last video.
- That was our starting point--when the photon started leaving that point, and obviously the universe kept expanding,
- the photon, it kind of traversed more and more, but it still had more and more to travel as the universe expanded,
- as all of space expanded.
- But this is 300,000 years after the Big Bang. Now, my brain, because I was kind of not thinking hard enough about it,
- I said, "Hey, this was 13.4 billion years ago." That's what I incorrectly said in the last video.
- I said that this is 13.4 billion years ago. That's what I said in the last video, and that is wrong.
- Because if this was 13.4 billion years ago, this would have been 300 million years after the Big Bang.
- We were talking about only 300,000 years after the Big Bang. So it wouldn't have taken that many decimal places
- off of something in the billions. The correct answer is this would have been only a little less than 13.7 billion years.
- It actually wouldn't have even made the significant digit. So this is still approximately 13.7 billion years ago.
- So I wanted to just make that correction. It was a slight error. I shouldn't have viewed this as 0.3 billion years.
- This was only 0.3 million years. It doesn't even basically change the precision on this number right over here.
- So I just wanted to clear that up, but hopefully it doesn't affect your understanding too much.