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BadgerBadger92
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Not long after the Big Bang, space expanded faster than light for a brief amount of time, slowed down, then sped up again.
Is there an answer to this question?
Is there an answer to this question?
References please. You know how this works here at the :PF.BadgerBadger92 said:Not long after the Big Bang, space expanded faster than light for a brief amount of time, slowed down, then sped up again.
Is there an answer to this question?
BadgerBadger92 said:Not long after the Big Bang, space expanded faster than light for a brief amount of time, slowed down, then sped up again.
Is there an answer to this question?
Yep. that's apparently what happened based on observations, and reasonable maths.BadgerBadger92 said:Not long after the Big Bang, space expanded faster than light for a brief amount of time, slowed down, then sped up again.
Is there an answer to this question?
This isn't an accurate description. In the standard model of cosmology, which includes inflation in the early universe, the rate of expansion has always been decreasing (and faster-than-light expansion is a nonsensical statement with no meaning, as expansion is not a speed: it's like saying a car is traveling faster than 1MHz).BadgerBadger92 said:Not long after the Big Bang, space expanded faster than light for a brief amount of time, slowed down, then sped up again.
Is there an answer to this question?
kimbyd said:In the standard model of cosmology, which includes inflation in the early universe, the rate of expansion has always been decreasing
PeterDonis said:it was increasing during inflation, decreasing after the end of inflation until a few billion years ago, and since then has been increasing again
Islam Hassan said:Alan Guth in his lectures “Inflationary Cosmology: Is Our Universe Part of a Multiverse” says that inflation was caused by a patch of repulsive gravity-bearing matter in the pre-inflationary universe
This is the one at around 13:20:PeterDonis said:Which particular lecture? There are a lot of them (assuming you mean the video lectures on the MIT open courseware site).
Islam Hassan said:The slide showing that he is commenting says “The combination of GR and modern particle theories predicts that, at very high energies, there exists forms of matter that create a gravitational repulsion!”
This issue is also addressed in the video I posted.bahamagreen said:In the Guth video, at about 57:30 he is talking about local decay of eternal inflation that results in the multiverse "pocket universes", and he clarifies that "eternal" inflation means "forever into the future" only... that "inflation would start at some finite time".
Why? If the inflation is able to produce "pocket universes" forever, it seems to me that its properties that allow that must be continuous. I'm not seeing why inflation can't have always been happening. He does not elaborate on why it's only into the future... it would seem very attractive and elegant if the inflation was eternal both past and future, so there must be some reason why not. Anyone know?
"...expansion is not a speed..." What does inflation / expansion mean in this context? Also, has the standard model for the big bang been discredited and replaced by another model? If so, which model has replaced it. I'm a novice so please keep your answer novice-friendly if you can.kimbyd said:This isn't an accurate description. In the standard model of cosmology, which includes inflation in the early universe, the rate of expansion has always been decreasing (and faster-than-light expansion is a nonsensical statement with no meaning, as expansion is not a speed: it's like saying a car is traveling faster than 1MHz).
But there isn't any known cause for inflation at the moment. Inflation itself isn't entirely certain (there are a few alternative models around that also match the data).
Speed is the rate at which something moves through space with respect to another object but that doesn't have any meaning when it comes to the expansion of the universe. The expansion of the universe has a rate but it doesn't have a speed, see here for more details.cliffhanley203 said:"...expansion is not a speed..." What does inflation / expansion mean in this context? Also, has the standard model for the big bang been discredited and replaced by another model? If so, which model has replaced it. I'm a novice so please keep your answer novice-friendly if you can.
windy miller said:In may textbooks it is stated that inflation happens after the big bang but this may be mistake.
Agree with two exceptions though. Slightly after that bit about a patch of repulsive gravity material he sets out that this is possible without violating the conservation of energy because the energy budget of the universe as a whole is zero, or very close to zero.PeterDonis said:It is. Guth explains the correct model well in the video.
Islam Hassan said:In this way, he says that the positive energy of all matter and radiation in the universe is balanced by the negative energy of gravity. I don’t quite understand this if an object in a gravitational field has (positive) energy. Does he mean that the ‘creation’ of a gravitational field involves negative energy?
Cosmic inflation refers to a period of rapid and exponential expansion of the universe that is believed to have occurred in the first few fractions of a second after the Big Bang. This theory helps to explain the large-scale structure of the universe and the uniformity of the cosmic microwave background radiation.
The exact cause of cosmic inflation is still a subject of debate among scientists. Some theories suggest that it was triggered by a sudden release of energy during a phase transition in the early universe, while others propose the existence of a hypothetical field called the inflaton field.
Cosmic inflation is believed to have occurred immediately after the Big Bang and is considered a crucial component in our understanding of the early universe. It helps to solve some of the problems with the original Big Bang theory, such as the horizon problem and the flatness problem.
While there is no direct evidence for cosmic inflation, several lines of evidence support this theory. These include the observations of the cosmic microwave background radiation, the distribution of galaxies, and the presence of gravitational waves in the early universe.
While the most widely accepted theory suggests that cosmic inflation only occurred once in the early universe, some alternate theories propose multiple episodes of inflation. However, there is currently no conclusive evidence to support either scenario.