Cosmic Inflation: The Solution to the Big Bang Theory and the Universe

Follow up video on Eternal Inflation:

References:

Chapters:
0:00 - Popular models of Big Bang are incorrect
2:27 - Observations not explained by original Big Bang model
4:37 - Common misunderstandings of Big Bang
7:12 - How Inflation "fixes" the Big Bang
11:56 - What caused cosmic Inflation?
15:23 - Next video: Eternal Inflation!

Summary:
The Big Bang theory: In the beginning, the universe was packed tightly together into a point of infinite density. It then exploded into the universe we see today. This is actually INCORRECT.

There was no explosion. There was no substance like stars, galaxies, or even atoms that went flying. The universe did not have zero size or infinite density. It is just a moment in time when the universe was very hot and very dense.

And contrary to popular belief, the big bang model is not a theory of how the universe began. We don't know how it began.

The early model of the BB failed to explain some later observations about the universe - its homogeneity, its flatness, and no magnetic monopoles. The theory of cosmic inflation proposed by Alan Guth and others, solved these puzzles.

What is this theory of Inflation? How does it fix the big bang? What caused Inflation to happen?

Cosmic Inflation is a sudden expansion, faster than the speed of light, whcih happend from about 10^-36 seconds after the beginning to 10^-32 seconds. It expanded a factor of at least 10^78x

How could inflation occur faster than speed of light? Einstein’s theory of special relativity shows that speed limit applies only to things moving within space, not the expansion of space itself.

Some descriptions of inflation say the universe started out smaller than an atom, then expanded to the size of a grapefruit. This is misleading because it implies that the universe has an edge. It doesn’t.

Other common misunderstandings about the Big Bang: The universe did not come from a point of infinite density and heat. This is purely due to mathematical extrapolation. A singularity is probably not a physical thing.

Universe is expanding, but galaxies aren’t actually moving at that expansion rate, only the space between galaxies is becoming larger, and only on very large scales. But on smaller scales gravity still holds stars together within a galaxy, and certain galaxies are still attracted to each other.

There is no center of the universe or location. Every point moved away from every other point.

The universe is extremely homogenous and isotropic which means that it appears roughly the same anywhere. This can be seen in the cosmic microwave background, or CMB, where the tiny differences you see on its image represent temperature fluctuations of only 0.0001 Kelvin.

How did the universe smooth out? Imagine it like the surface of deflated balloon. There may be tiny imperfections like wrinkles randomly distributed on it. If the balloon is suddenly inflated to a very large size, the wrinkles get smoothed out.

How does inflation explain the flatness issue? If you were the size of an ant on a small balloon, and the balloon expanded to the size of the Earth, it would appear flat to you, even though it is still a sphere, that it's flat. Note "curvature" means an overall curvature of the universe in FOUR dimensions. This is usually shown as 2D surface on a 3D object like a balloon.

How does inflation solve the fact that we observe no magnetic monopoles?

Monopoles can only theoretically form at very high temperatures, that were only present during the big bang. But once they formed they would be stable enough to survive. Since Inflation would have quickly cooled the universe, no new monopoles would be created after inflation. These would have been distributed so broadly that there would be hardly any left in any given part of space.

The universe is not completely smooth. CMB shows that there were small temperature differences. This anisotropy explains the large scale structures of the universe.

How did inflation start? What was responsible for inflation?

This is not well understood. It is thought that there may have been a scalar inflation field during the time of the big bang, called the inflation field.
#cosmicinflation
#bigbang
This field would have been in a false vacuum at very high temperatures, but moved to its true vacuum at lower temperatures, with the help of quantum tunneling. When the field reached the lowest minimum energy density in the potential, Inflation came to a stop. This is a very short process.

[hupekyser]

I've said it many times but. Your explanations are absolutely remarkable, in that you can explain so many complicated ideas so straight forward and accessible. I have no idea how you can do it.

Bravo, on another fascinating video.

[effectingcause]

Why is the flatness problem not just assumed to mean the universe is so HUGE that we cannot even measure the curvature due to a lack of experimental sensitivity to the curve?

[stanfordyu]

Why do I found your videos addicting? Like, I can’t stop watching them… Ur my favorite educator so far.

[Raphael]

This channel always has the best physics explanations on Youtube!

[ktish]

Good timing. I literally just finished reading chapter 4 in the book "Origins" by Tyson that goes over this very subject. Seeing it after reading it makes it easier to understand. Always love your videos!

[fellopiantube]

thank you for addressing those many misconceptions. the story is now much more clearer for me.

[daffidavit]

I've heard this explained by many others, but this is one of the better presentations.

[thestragequack]

Impatiently waiting for the next part!

[robotaholic]

Guth is the opposite of arrogant. He never brags or even gets heated in discussions. I really like his attitude and yours too sir

[matkosmat]

Thanks, Arvin, for another great video! My mind was still struggling with the X10^78 growth during Inflation when you said "unimaginably bigger"... I wonder what would be "unimaginable" to a person like you or Dr Guth :)

[anthonyghossoub]

Simply amazing videos that makes us all more and more interested in physics

[johngrey]

Excellent lecture! Thank you, Mr. Ash.

[shmigelsky]

Thanks, that is super interesting. This has to be one of my favourite channels, please keep up the outstanding videos.

[d_xnii]

i love your videos so so much, thank you for putting so much work in to them💗

[jeancorriveau]

I watched videos from other sources (and read articles). Arvin's contribution clarifies a few concepts. I find inflation theory makes sense now. The timeline presented gives me a feel (sort of) for such tiny durations, like 10^-32 second. At the level of the Planck units, this is a huge duration. A lot can and did happen. That the universe expands from every single spot in the universe, and in all directions, can only be possible with a fourth dimension feeding space with energy (dark energy?). It's not the time dimension.

[Dragrath]

Given that recent observations have largely falsified the cosmological principal assumption of the existence of any scale where the universe is isotropic and homogeneous up to 4.9 sigma (meaning there is only a 1 in 2 million statistical odds of the observations being a statistical fluke arising by chance within a universe where the cosmological principal largely applies) I have personally become extremely skeptical of the so called inflationary model.

What has been conveniently forgotten with the standard narrative for modern cosmology is that we have *never* had proof that the dipole observed in the CMB is "kinematic" that was merely assumed for convenience in the absence of any data. However there was an experimental test proposed in the 1980's which could test this assumption either verifying or falsifying the kinematic dipole assumption. The catch is that the test requires millions of cosmologically distant sources all across the whole sky which can be used to construct a dipole to compare to the CMB dipole in magnitude and direction data which hasn't existed. As such the field of cosmology largely went on assuming their assumption since then as an initial premise despite warnings of other cosmologists and mathematicians

Last year this test was finally performed by Nathan J. Secrest et al. using 1.36 million quasars measured over the various initial and extended missions of WISE that are cataloged into the meta catalogue catWISE.

The Dipole differs in 8 degrees of direction with over twice the magnitude of the CMB dipole which is at 4.9 sigma disagreement with the kinematic dipole assumption which requires that both dipoles be the same in both magnitude and direction. Citation: Nathan J. Secrest et al 2021 ApJL 908 L51

This is significant enough to rule out the pure kinematic dipole assumption, i.e. the cosmological components of the CMB dipole arising from inhomogeneities and anisotropies encoded in the CMB epoch must be nonzero.

Remember the observed dipole in the CMB is in general a combination of the kinematic component of the dipole but also two cosmological components that respectively represent both the initial inhomogeneities and anisotropies at the time of recombination when the CMB was emitted and all the distortions from intervening inhomogeneities in density.

The standard cosmological model is built on the *assumption* that all of these components are zero except the kinematic term. This has now been experimentally *falsified* showing that at least one of these other components must be significantly nonzero.

*The existence of a nonzero cosmological component to the CMB dipole automatically is sufficient to falsify the existence of the cosmological principal within the observable universe.*

This in turn is sufficient to falsify one of the main lines of "evidence for inflation namely the supposed "smoothness" of the early universe, hence inflation is now on far more shaky ground as the reason it appears smooth turns out to be that you have applied a correction to eliminate the large temperature and density fluctuations that were actually encoded in the CMB because they looked to large for cosmologists to except.

TDLR *the CMB fluctuations appear small not because they actually are small but because cosmologists have removed the large fluctuations from the data set before they analyzed it because they seemed too large to be fluctuations in their assumed model.*

If you want the paper to check for yourself I have cited it above and if needed I can provide a link to the paper so you can read it for yourself.

[sabarapitame]

Here, in Argentina, economic inflation grows almost in the same way as cosmological inflation every year.

It just occurred to me watching the video, couldn't we be a black hole that exploded in another universe by Hawking radiation?

[stevemonkey]

Your explanation of inflation starting at about 13:20 is very interesting. I have never seen anything like it on a popular science channel 👍

[rwarren]

As always a great presentation. In combination with your other videos, I think of the incredible odds it took to make our universe just right and for us to be inhabitants of this universe. Your next video will answer (or at least explain) my question about fine tuning, so I will ask this. What is the purpose of the Universe? Thanks again and welcome back. It feels like aeons since you last posted.

[petergreen]

❤beautiful lesson and explanation. Thank you very much publisher. Thank you Arvin.