We all know that we stay in an increasing universe. Which means the whole universe is getting greater with each passing day. It additionally means that previously our universe was smaller than it’s at the moment.
Rewind that tape far sufficient, and the physics suggests our universe was as soon as an infinitely tiny, infinitely dense level — a singularity.
Most physicists suppose this level expanded out within the Big Bang, however as a result of all recognized physics breaks down within the excessive situations that prevailed in our universe’s infancy, it is exhausting to say with confidence what occurred in these earliest moments of the universe.
Going again in time
For a lot of the historical past of the universe, it was dotted with comparable celestial objects as are current now — they had been simply nearer collectively.
For instance, when our universe was lower than 380,000 years previous, the amount of the universe was about one million occasions smaller than it’s at the moment, and it had a median temperature of round 10,000 Kelvin. It was so scorching and dense that it was a plasma, a state of matter the place atoms are ripped aside into protons, neutrons and electrons. Nevertheless, we encounter plasmas in lots of different conditions in house and on Earth, so we’ve got a reasonably good understanding of how they work.
However the farther again we go, the extra complicated the physics turn into. When the universe was only a dozen minutes previous, it was an intense soup of protons, neutrons, and electrons, nonetheless ruled by the identical physics that we use to know nuclear bombs and nuclear reactors.
If we glance again even sooner than that, nonetheless, issues get actually sketchy.
Once we attempt to make sense of the universe when it was lower than a second previous, we’ve got no idea of physics that may address the insanely excessive temperatures and pressures the universe skilled. All of our theories of physics break down, and we’ve got no understanding of how particles, forces and fields function in these situations.
Birthing the singularity
Physicists can chart the expansion of the cosmos utilizing Einstein’s general theory of relativity, which connects the content material of the cosmos to its historical past of enlargement.
However Einstein’s idea incorporates a deadly flaw. If we comply with common relativity to its final conclusion, then at a finite time prior to now our complete universe was crammed right into a single, infinitely dense level. This is called the Large Bang singularity.
The singularity is commonly framed because the “starting” of the universe: Nevertheless it’s not a starting in any respect.
Mathematically, the singularity on the Large Bang is not telling us that the universe started there. As a substitute, it is telling us that common relativity itself has damaged down, and has misplaced its predictive and explanatory energy.
Physicists have lengthy recognized that common relativity is incomplete. It can not clarify gravity at excessive energy or at small scales, referred to as quantum gravity. In different phrases, to totally perceive the earliest moments of the universe, we’d like new physics.
A query for the ages
Sadly, we at the moment lack such physics. Now we have a number of candidates for quantum gravity, like string idea and loop quantum gravity, however these theories haven’t been totally developed, not to mention examined.
But when both of these theories are appropriate, they will inform us attention-grabbing issues concerning the early universe.
Within the case of loop quantum gravity, the singularity is changed with a finite-size chunk of space-time. In string theory, in the meantime, our universe originates from a “panorama” of potential universes. It is also potential that our Large Bang exists as simply certainly one of an infinite sequence of universes, multiplying with out finish in a multiverse. Solely additional advances in theoretical physics will assist type out the murkiness of those potential concepts.
However there’s one other downside: We might by no means know what precipitated the Large Bang. In its earliest moments, even our very conceptions of time and house break down. At such excessive scales, regular, on a regular basis ideas like “starting” and “earlier than” might not even make sense.
Initially revealed on LiveScience.