Physicists still do not know why the universe contains almost entirely matter and essentially no leftover antimatter, even though the Big Bang should have produced them in equal amounts.

124:51in the universe, which should have made matter and antimatter. We only see matter. Where'd the antimatter go? And the answer is, we don't know. However, there are some ideas, and there's a lot of thinking on it, and in fact, for me, it's doing an experiment right now with neutrinos, trying to better understand what it was that made the matter and antimatter not be the same. Now, we do have a measurement

125:21of how much different it should be, and it's kind of neat. We can do this by counting the number of protons in the universe, just looking at galaxies and so forth, and then we can look at the cosmic microwave background, which is sort of the aftermath of the Big Bang, and we can count the number of photons from the cosmic microwave background. And with a little bit of math, what we can do

125:46is we can then say that somehow in the early universe, something made a very, very tiny asymmetry, so that for every billion, billion with a B, antimatter particles that existed in the universe, there were a billion and one matter particles. The billions canceled, annihilated, destroyed each other, and that extra one that's left over is us. And so what physics mechanism made that ever so slight asymmetry is not understood. There are some thoughts.

126:29One thought is that, well, it's just how it was. When the universe was formed, there was an asymmetry. It was not made by matter and antimatter. Another possibility is there are various numbers of theories all under the word baryogenesis, baryo coming from word baryon, which basically means protons, and genesis meaning the creation of, and we'd say that simply because the protons are the heaviest particles. And so