There Was No Big Bang Singularity
Starts With A Bang
Ethan Siegel Contributor
Jul 27, 2018, 10:00am
An illustration of our cosmic history, from the Big Bang until the present, within the context of the expanding Universe. The hot Big Bang was preceded by a state of cosmic inflation, but the idea that all of it must be preceded by a singularity is woefully out of date.NASA / WMAP SCIENCE TEAM
Almost everyone has heard the story of the Big Bang. But if you ask anyone, from a layperson to a cosmologist, to finish the following sentence, "In the beginning, there was..." you'll get a slew of different answers. One of the most common ones is "a singularity," which refers to an instant where all the matter and energy in the Universe was concentrated into a single point. The temperatures, densities, and energies of the Universe would be arbitrarily, infinitely large, and could even coincide with the birth of time and space itself.
But this picture isn't just wrong, it's nearly 40 years out of date! We are absolutely certain there was no singularity associated with the hot Big Bang, and there may not have even been a birth to space and time at all. Here's what we know and how we know it.
When we look out at the Universe today, we see that it's full of galaxies in all directions at a wide variety of distances. On average, we also find that the more distant a galaxy is, the faster it appears to be receding from us. This isn't due to the actual motions of the individual galaxies through space, though; it's due to the fact that the fabric of space itself is expanding.
This was a prediction that was first teased out of General Relativity in 1922 by Alexander Friedmann, and was observationally confirmed by the work of Edwin Hubble and others in the 1920s. It means that, as time goes on, the matter within it spreads out and becomes less dense, since the volume of the Universe increases. It also means that, if we look to the past, the Universe was denser, hotter, and more uniform.
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If you were to extrapolate back farther and farther in time, you'd begin to notice a few major changes to the Universe. In particular:
you'd come to an era where gravitation hasn't had enough time to pull matter into large enough clumps to have stars and galaxies,
you'd come to a place where the Universe was so hot you couldn't form neutral atoms,
and then where even atomic nuclei were blasted apart,
where matter-antimatter pairs would spontaneously form,
and where individual protons and neutrons would be dissociated into quarks and gluons.
