Among most people who study the early Universe, inflation is accepted as the new consensus theory. We might not know everything there is to know about inflation, but either it — or something so similar to it that we don't have an observation to tell them apart — must have happened. With all that said, what does that mean for our cosmic origins? From a timeline perspective, what comes first: the Big Bang or inflation?
But in an inflationary scenario yellow , we never reach a singularity, where space goes to a singular state; instead, it can only get arbitrarily small in the past, while time continues to go backwards forever. Only the last minuscule fraction of a second, from the end of inflation, imprints itself on our observable Universe today. The Hawking-Hartle no-boundary condition challenges the longevity of this state, as does the Borde-Guth-Vilenkin theorem, but neither one is a sure thing.
Believe it or not, the above graph contains all the information you'd need to know for certain. Two of the curves — red and blue — represent a Universe dominated by either matter or radiation. But if at some early time, the Universe isn't dominated by matter or radiation, but by a form of energy inherent to space itself, you get the yellow curve.
Note how this yellow curve, since it's an exponential curve, never reaches zero in size, but only approaches it, even if you go infinitely far back in time. An inflating Universe doesn't begin in a singularity like a matter-dominated or radiation-dominated Universe does. All we can state with certainty is that the state we call the hot Big Bang only came about after the end of inflation.
It says nothing about inflation's origins. The quantum fluctuations inherent to space, stretched across the Universe during cosmic inflation, This is the best picture we have of how the entire Universe behaves, where inflation precedes and sets up the Big Bang.
In fact, our entire observable Universe contains no signatures at all from almost all of its pre-hot-Big-Bang history; only the final 10 seconds or so of inflation even leave observably imprinted signatures on our Universe. We do not know where the inflationary state came from, however. It might arise from a pre-existing state that does have a singularity, it might have existed in its inflationary form forever, or the Universe itself might even be cyclical in nature.
There are a lot of people who mean "the initial singularity" when they say "the Big Bang," and to those people, I say it's long past due for you to get with the times. The hot Big Bang cannot be extrapolated back to a singularity, but only to the end of an inflationary state that preceded it.
We cannot state with any confidence, because there are no signatures of it even in principle , what preceded the very end-stages of inflation. Was there a singularity? Maybe, but even if so, it doesn't have anything to do with the Big Bang. Even though this hasn't been the leading thought in the field in nearly 40 years, it serves as an example of people, today, getting a well-known detail wrong through simple lack-of-care.
Inflation came first, and its end heralded the arrival of the Big Bang. There are still those who disagree, but they're now nearly a full 40 years out of date. When they assert that "the Big Bang was the beginning," you'll know why cosmic inflation actually came first.
As far as what came before the final fraction-of-a-second of inflation? Your hypothesis is just as good as anyone's. This is a BETA experience. You may opt-out by clicking here. Perhaps light is still slowing now, just at a rate that is imperceptible even to our most sensitive detectors.
Cosmic inflation is a faster-than-light expansion of the universe that spawned many others. Articles Videos. Physics crunch: The dark void at cosmology's heart Everything we know about the universe — and a few things we don't The four puzzles that tell us a cosmological revolution is coming We may be able to find magnetic fields from the start of the universe The eternal debate about the eternal inflation of the universe.
Roberto Trotta: What has Einstein ever done for you? Inflation works as a cosmic microscope to see the quantum fluctuations in the very early Universe. Using classical physics , the evolution of the inflationary Universe is homogeneous - each spatial point evolves exactly the same way.
However, quantum physics introduces some uncertainty in the initial conditions for the different spatial points. These variations act as seeds for structure formation. After the inflationary period, when fluctuations are amplified, the density of matter will vary slightly from place to place in the Universe.
Gravity will cause the more dense regions to start contracting, leading to the formation of galaxies. The figure below shows how the image of quantum noise may appear imprinted on the cosmic microwave background. Red and blue denote hot and cold variations of the temperature, measured by the WMAP satellite over seven years.
Comparing the statistics of the measured data with our theoretical calculations shows very good agreement. Outreach home. An introduction to inflation Low density inflationary Universes Geometry and density Low density Universes and inflation General open inflation Phase transitions in the early Universe Cosmic strings and other topological defects Cosmic string dynamics and evolution High-resolution cosmic string simulations Cosmic strings and large scale structure.
Introduction The inflationary Universe According to the theory of inflation, the early Universe expanded exponentially fast for a fraction of a second after the Big Bang.
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