載入中... 相關課程 Back (Correction) Radius of Observable Universe 登入觀看 ⇐ Use this menu to view and help create subtitles for this video in many different languages. You'll probably want to hide YouTube's captions if using these subtitles. (Correction) Radius of Observable Universe 上傳學習單 下載學習單 相關課程 0 / 750 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.