Think about the following questions as you watch the video

1. 00:26 How long ago did the Big Bang happen?
2. 00:46 What made the Big Bang possible? Why did the Big Bang happen? Was there space and time before the Big Bang?
3. 01:15 When did matter and energy form after the Big Bang?
4. 01:20 What forms did energy take after the Big Bang?

00:13: NARRATOR: Our first threshold
00:15: is the Big Bang,
00:16: which happened about 13.7 billion years ago
00:20: and led to the creation of the entire universe.
00:23: We don't know much about the ingredients
00:26: and the Goldilocks conditions
00:27: that led to this first threshold
00:29: because we just don't have much evidence.
00:32: For example, what made the Big Bang possible?
00:35: We don't know.
00:37: Why did the Big Bang happen?
00:39: We can only speculate.
00:41: Was there even space and time before the Big Bang?
00:44: We don't know that either.
00:48: What we do know is that the Big Bang provided
00:51: the raw materials for everything around us today.
00:54: After the Big Bang there was space,
00:56: which was rapidly expanding, and there was time.
01:00: There was also matter and energy.
01:03: At first, the universe was so hot
01:05: that you couldn't tell the difference
01:06: between matter and energy,
01:07: but within the first billionth of a second after the Big Bang,
01:11: matter and energy separated.
01:14: Then energy took different forms,
01:17: including gravity and electromagnetism.
01:20: And matter appeared in the form of electrons and quarks.
01:23: And quarks soon linked up to form protons and neutrons.
01:28: Why is this so important?
01:31: Because nothing had turned into something,
01:35: and that something contained everything needed
01:39: to build an interesting universe,
01:41: one that could eventually include you and me.
01:46: Now let's take a closer look at how our universe