Edwin Hubble discovered that light from distant galaxies was redshifted around 1930; the more away, the more shifted. This was rapidly deduced to suggest that galaxies were moving away from Earth. If Earth does not occupy a unique, privileged, central position in the cosmos, then all galaxies are moving apart, and the further they are apart, the quicker they are moving apart. The cosmos is expanding, carrying galaxies with it and creating this discovery, it is now understood. Many other observations support this theory and lead to the same conclusion. For many years, however, it remained unclear why or how the cosmos was expanding, or what it meant.
It is presently thought that the cause for the discovery is that space itself is expanding, and that it expanded very rapidly within the first fraction of a second following the Big Bang, based on a large amount of experimental observation and theoretical work. A “metric” expansion is the name for this type of expansion. A “metric” is a measure of distance that meets a precise set of qualities in mathematics and physics, and the phrase suggests that the perception of distance inside the cosmos is changing. Metric difference is now much too minor an influence to notice on anything smaller than an interplanetary scale.
Physicist Alan Guth presented the modern theory for the metric expansion of space in 1979, while looking into why there are no magnetic monopoles nowadays. According to general relativity, if the cosmos had a field in a positive-energy false vacuum state, it would cause an exponential expansion of space. It was rapidly understood that such a growth would solve a slew of other long-standing issues. These issues come from the fact that, in order for the Universe to appear as it does now, it would have had to begin with extremely finely adjusted, or “unique” beginning conditions at the Big Bang. Inflation theory also largely answers these issues, making a world similar to ours much more feasible in the context of the Big Bang theory.
There is yet to be identified a physical field that is accountable for this inflation. However, such a field would be scalar, and the Higgs field, the first relativistic scalar field shown to exist, was only discovered in 20122013 and is currently under investigation. As a result, the fact that a field responsible for cosmic inflation and the metric expansion of space has yet to be discovered is not considered as an issue. The inflaton is the name given to the hypothesized field and its quanta (the subatomic particles associated with it). Without this field, scientists would have to come up with an alternative explanation for all of the evidence that strongly show a metric expansion of space has occurred, and is continuing occurring (although much more slowly) now.
What is the cosmic inflation theory?
The idea of cosmic inflation argues that the universe had a period of exceptionally rapid exponential expansion in its early moments (beginning at 1036 seconds after the Big Bang singularity, to be precise).
What was the size of the universe before inflation?
However, scientists have yet to figure out how those two times are linked. A recent study shows a connection between the two epochs.
In less than a trillionth of a second, the universe expanded from an almost unimaginably small point to approximately an octillion (that’s a 1 followed by 27 zeros) times its original size. This period of inflation was followed by the Big Bang, a more gradual but violent period of expansion. An extremely hot fireball of fundamental particles, including as protons, neutrons, and electrons, expanded and cooled to produce the atoms, stars, and galaxies we see today during the Big Bang.
Has the speed of light been exceeded by cosmic inflation?
Cosmic inflation is a faster-than-light expansion of the universe that gave birth to a slew of new universes.
Inflation was created to explain a few aspects of the universe that would be difficult to explain otherwise. The first is that matter, according to Einstein’s general theory of relativity, bends space and time, so you’d expect a universe like ours, which has mass, to be overall curved in some way, either inward like a ball (“positive”) or outward like a saddle (“negative”).
In reality, it’s almost completely flat. Furthermore, even sections of it far apart in various directions as seen from Earth have nearly the same temperature, despite the fact that in an expanding cosmos, there wouldn’t have been enough time for heat to move between them to smooth things out. That appears to be a direct challenge to the rules of thermodynamics.
Cosmic inflation solves all of these issues at once. The universe grew faster than light in its early moments (light’s speed restriction only applies to things within the cosmos). That smoothed out the wrinkles in its early chaotic state and ensured that even now, far-flung areas could exchange heat because they were formerly in close proximity.
What makes inflation happen quicker than light?
In an inflationary Universe, any two particles will watch the other one recede from them at rates that appear to be faster-than-light after a fraction of a second. The reason for this is that the space between the particles is expanding, not because the particles themselves are moving. When particles are no longer in the same place in space and time, they can begin to experience the general relativistic effects of an expanding Universe, which quickly overwhelm the unique relativistic effects of their individual motions during inflation. We fool ourselves into believing a faraway particle travels faster-than-light when we ignore general relativity and the expansion of space and instead ascribe all of its motion to special relativity. The Universe, on the other hand, is not static. It’s simple to realize this. The difficult thing is figuring out how that works.
What did Alan Guth come up with?
Alan Guth, buried beneath a stack of papers and empty Coke Zero bottles, ponders the beginnings of the universe. Guth is a world-renowned theoretical physicist and professor at the Massachusetts Institute of Technology. He is best known for developing the cosmic inflation theory, which explains the universe’s exponential growth mere fractions of a second after the Big Bang, as well as its continued expansion today.
However, cosmic inflation encompasses more than just the physics of the Big Bang. It also supports the theory that our universe is one of many, with even more universes yet to create, according to Guth.
Alan Guth (Alan): I recall an incident from high school that may be indicative of my desire to pursue a career as a theoretical physicist in particular. I was in high school physics, and a friend of mine was conducting an experiment that involved punching holes in a yard stick in various locations and rotating it on these holes to see how the period varied depending on where the hole was. I had just studied enough fundamental physics and calculus at this point to figure out what the answer to that question should be. I recall getting meeting with him one day and using a slide rule to compare my formula to his data. It was a success. I was ecstatic at the prospect of being able to calculate things in a way that accurately reflects how the real world operates.
You completed a particle physics dissertation and stated that it did not come out as you had hoped. Could you elaborate on that?
The quark model and how quarks and anti-quarks could bind to generate mesons were the subject of my dissertation. However, it was only a matter of time before the theory of quarks underwent a profound transformation. That revolution caught me off guard, and I was on the wrong side of it. Around the time I finished my thesis, it had become largely obsolete. I certainly gained a lot of knowledge from it.
It wasn’t until my seventh year as a postdoc that I became interested in cosmology. Henry Tye, a Cornell postdoc, became interested in grand unified theories, a newfangled class of particle theories at the time. He approached me one day and inquired if these grand unified theories predicted the existence of magnetic monopoles.
I had no idea what grand unified theories were at the time, so he had to teach me, which he did admirably. Then I had enough knowledge to put two and two together and conclude, as I’m sure many others did around the world, that yes, grand unified theories indeed predict the existence of magnetic monopoles, but that they would be absurdly heavy. They would be around 10 to the 16th power times heavier than a proton.
Six months later, Steve Weinberg, a fantastic physicist whom I had known since my graduate student days at MIT, paid a visit to Cornell. He was attempting to explain the predominance of matter over anti-matter using grand unified theories, but it required the same basic physics as determining how many monopoles were in the early cosmos. Why not me, I reasoned, since it was smart enough for Steve Weinberg to work on?
After a while, Henry Tye and I arrived to the conclusion that combining conventional cosmology with conventional grand unified theories would result in far too many magnetic monopoles. We were beaten to the punch in publishing it, but Henry and I resolved to keep trying to figure out whether there was anything that could be adjusted to make grand unified theories compatible with cosmology as we know it.
A few weeks before I started talking to Henry Tye about monopoles, there was a lecture at Cornell by Bob Dicke, a Princeton physicist and cosmologist, in which he presented the flatness problem, a problem about the early universe’s expansion rate and how precisely fine-tuned it had to be to produce a universe like the one we live in. Bob Dicke reminded us in this discussion that if you thought about the universe one second after it began, the expansion rate has to be exactly right to 15 decimal places, or else the universe would either fly apart or re-collapse too quickly for any structure to form.
That struck me as great at the moment, but I had no idea what it meant. But, after six months of working on the magnetic monopole problem, I realized one night that the kind of mechanism we were considering for suppressing the amount of magnetic monopoles produced after the Big Bang would have the unexpected effect of driving the universe into a period of exponential expansionnow known as inflationand that exponential expansion would solve the flatness problem. It would also bring the cosmos to the precise expansion rate required by the Big Bang.
After inflation, how quickly did the cosmos expand?
The expansion of the universe is defined as the time-dependent increase in distance between any two gravitationally unbound regions of the observable universe. It is a natural expansion in which the scale of space alters. The cosmos does not expand “into” anything, nor does it necessitate the existence of space “outside” of it. This expansion does not entail space or objects in space “moving” in the usual sense; rather, the metric (which determines the size and geometry of spacetime) shifts in scale. Objects get further distant from one another at ever-increasing speeds as the spatial element of the universe’s spacetime metric scales up. All of space appears to be expanding to any observer in the cosmos, and all save the nearest galaxies (which are constrained by gravity) appear to retreat at rates proportionate to their distance from the observer. While things in space cannot travel faster than the speed of light, this restriction does not apply to the consequences of changes in the metric. Objects beyond the cosmic event horizon will eventually become unobservable since no fresh light from them will be able to overcome the expansion of the universe, limiting the size of our observable cosmos.
The expansion of the cosmos differs from the expansions and explosions witnessed in everyday life as a result of general relativity. It is a quality of the universe as a whole, and it occurs throughout the universe rather than in a single location. As a result, unlike previous expansions and explosions, it cannot be witnessed from the “outside”; it is claimed that there is no “outside” from which to observe.
The FriedmannLematreRobertsonWalker metric is used to simulate metric expansion in Big Bang cosmology, and it is a generic attribute of the universe we live in. However, because gravity holds matter together tightly enough that metric expansion cannot be observed on a smaller scale at present moment, the hypothesis is only viable on large scales (about the scale of galaxy clusters and higher). As a result of metric expansion, the only galaxies that are receding from one another are those separated by cosmologically relevant scales larger than the length scales associated with gravitational collapse that are possible in the age of the universe given the matter density and average expansion rate.
According to inflation theory, the universe expanded by a factor of at least 1078 during the inflationary epoch, which occurred about 1032 of a second after the Big Bang (an expansion of distance by a factor of at least 1026 in each of the three dimensions). This would be the same as expanding an object 1 nanometer (109 m, about half the width of a DNA molecule) in length to 10.6 light years (1017 m, or 62 trillion miles) in length. After that, space continued to expand at a much slower and steady rate until, around 9.8 billion years after the Big Bang (4 billion years ago), it began to grow more quickly and is currently doing so. As a solution to explain this late-time acceleration, physicists have proposed the existence of dark energy, which appears as a cosmological constant in the simplest gravitational models. This acceleration becomes increasingly dominant in the future, according to the simplest extrapolation of the currently favored cosmological model, the Lambda-CDM model. Based on research utilizing the Hubble Space Telescope, NASA and ESA scientists stated in June 2016 that the universe is expanding 5 percent to 9 percent faster than previously thought.
What major physics rule does cosmic inflation defy?
Inflationary cosmology, on the other hand, cannot be the final hypothesis of the Universe. When the Universe is projected backward in time, it becomes so hot and dense that the physics principles that underpin inflation (classical general relativity) break down.