1
00:00:00,691 --> 00:00:02,811
I want to make a quick correction to the last video.

2
00:00:02,811 --> 00:00:08,383
It doesn't really affect the learning of the last video, but I just want to make sure that you understand

3
00:00:08,383 --> 00:00:11,213
that I got the math a little bit wrong in the last video.

4
00:00:11,213 --> 00:00:18,010
I said that, you know, you had this state 300,000 years--so we talk about the Big Bang happening

5
00:00:18,010 --> 00:00:25,649
13.7 billion years ago.

6
00:00:25,649 --> 00:00:33,913
And then I talk about this state of affairs where we're maybe 30 million light years

7
00:00:33,913 --> 00:00:39,608
away from the edge of the observable universe, the current observable universe.

8
00:00:39,608 --> 00:00:51,287
And I said that this was about 300,000 years after the Big Bang. That's what I talked about in the last video.

9
00:00:51,287 --> 00:00:56,433
That was our starting point--when the photon started leaving that point, and obviously the universe kept expanding,

10
00:00:56,433 --> 00:01:02,332
the photon, it kind of traversed more and more, but it still had more and more to travel as the universe expanded,

11
00:01:02,332 --> 00:01:04,004
as all of space expanded.

12
00:01:04,004 --> 00:01:11,067
But this is 300,000 years after the Big Bang. Now, my brain, because I was kind of not thinking hard enough about it,

13
00:01:11,067 --> 00:01:17,116
I said, "Hey, this was 13.4 billion years ago." That's what I incorrectly said in the last video.

14
00:01:17,116 --> 00:01:27,360
I said that this is 13.4 billion years ago. That's what I said in the last video, and that is wrong.

15
00:01:27,360 --> 00:01:33,108
Because if this was 13.4 billion years ago, this would have been 300 million years after the Big Bang.

16
00:01:33,108 --> 00:01:38,867
We were talking about only 300,000 years after the Big Bang. So it wouldn't have taken that many decimal places

17
00:01:38,867 --> 00:01:47,254
off of something in the billions. The correct answer is this would have been only a little less than 13.7 billion years.

18
00:01:47,254 --> 00:01:56,434
It actually wouldn't have even made the significant digit. So this is still approximately 13.7 billion years ago.

19
00:01:56,434 --> 00:02:01,728
So I wanted to just make that correction. It was a slight error. I shouldn't have viewed this as 0.3 billion years.

20
00:02:01,728 --> 00:02:08,277
This was only 0.3 million years. It doesn't even basically change the precision on this number right over here.

21
00:02:08,277 --> 00:02:13,909
So I just wanted to clear that up, but hopefully it doesn't affect your understanding too much.