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What Was It Like When The Big Bang First Began?
13.8 billion years ago, our Universe as-we-know-it came into existence. Here’s what it was like.
Looking out at our Universe today, we not only see a huge variety of stars and galaxies both nearby and far away, we also see a curious relationship: the farther away a distant galaxy is, the faster it appears to move away from us. In cosmic terms, the Universe is expanding, with all the galaxies and clusters of galaxies getting more distant from one another over time. In the past, therefore, the Universe was hotter, denser, and everything in it was closer together.
If we extrapolate back as far as possible, we’d come to a time before the first galaxies formed; before the first stars ignited; before neutral atoms or atomic nuclei or even stable matter could exist. The earliest moment at which we can describe our Universe at hot, dense, and uniformly full-of-stuff is known as the Big Bang. Here’s how it first began.
Some of you are going to read that last sentence and be confused. You might ask, “isn’t the Big Bang the birth of time and space?” Sure; that’s how it was originally…