And what caused the cosmic inflation? Was it energy? If so then what caused the energy? We know that energy can't be created, so how would it have a cause if the cause is not even there? For something to begin to exist without an external cause would make it self caused. So did existence itself cause energy?

Sorry for too many questions lol.

Hi all, Im having another sleepless night and thought of three questions about the universe, and thought id shoot my shot in this subreddit.

My first question originated from my brother talking about space and its expansion.

It is: Is the universes exapansion creating new space or stretching the space in between atoms? If it is stretching the space, wouldn’t that mean in an infinitely large universe there would be infinite space between atom and individual molecules?

My second question is: Where does consciousness fit into the universe? Is it as simple as a folding of an objective universe into many subjective folds? I know this question poses many more arguments in biology and whatnot, and can be more philosophical than scientific, I just want to know the science side of it.

My third and final question is: Is it plausible that the universes laws of physics work so well is not only determined by chance, but a structural creation of everything so that new laws of physics were made as the universe progressed to create a stable system? It was organized by a more complex system?

Thank you for reading my questions, I recently got back into cosmology.

So I have a B.S. in Applied Physics and a Master's in Astronomy and while the Lambda-Cold Dark Matter model of cosmology is the currently accepted model I have always had some reservations about certain aspects of it. -Nuclear Bariogenesis- The reason we only see matter instead of anti matter is explained with symmetry breaking. I always thought it just made way more sense that equal amounts of matter/AM were created during the big bang, most of which annihilated immediately, and what was left were pockets of matter only then pockets of AM only, expansion pushed these pockets far enough away that they now no longer interact. Pockets could be individual galaxies, galactic clusters or even where the entire observable universe in matter and there are equally large portions of AM past where we can see -Dark Matter- This always seemed like a stubborn closed mind band aid for the galactic rotation curves not matching. Normally you get new data conflicting with your model you realize that your model in incomplete. Instead of that people were like, "Well, if we just add some mass around the galaxy our model works, oh yeah, and we can't detect said matter." I'm not saying that M.O.N.D. is correct but at least it's a more open minded approach to new conflicting data.

I was reading these papers by Sean Carroll (https://arxiv.org/abs/1405.0298; https://arxiv.org/abs/1505.02780) in which, among other things, he argues against vacuum up-tunneling occurring in the universe. He only acknowledged that it would be possible in the first moments of the universe while it was heated, but after that the rate goes to zero.

Meanwhile, vacuum energy can be excited by high energetic events like high energy cosmic rays. I thought that cosmic rays, being massive particles, were not redshfited by the expansion of the universe as photons are; therefore, if cosmic rays were produced in the big bang or as a result of a previous false vacuum decay, then these particles could eventually excite the vacuum, essentially causing an up-tunneling.

However, apparently cosmic rays can get redshifted as well (https://astronomy.stackexchange.com/questions/43525/is-there-an-equivalent-of-the-red-shift-effect-for-cosmic-rays). Then, is it impossible that cosmic rays may excite the vacuum in the future? Is there any kind of energy that does not get "redshifted" and therefore could cause an up-tunneling of the vacuum (like perhaps matter-antimatter generation: https://www.sciencedaily.com/releases/2011/10/111028142508.htm)? Is it really utterly impossible to excite the vacuum?

Ask your cosmology related questions in this thread.

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Modern cosmology and physics calculates that for Baryogenesis only 1 hadron per 2*10^9 survived.

What a that ratio for leptons after the following Leptogenesis?

Looking for a book that explains the most contemporary cosmological theories. I’d want some of the nitty gritty math and science, but not overly so as I probably won’t understand all of that.

What are the best books to learn cosmology with full mathematical details and with great physical explanations? For example I love Klauber’s books „Student friendly quantum field theory”, because there are no skipped derivations, and the topic is covered with great detail. I’m looking for a similar book about cosmology.

I want to learn enough to be able to describe universe of various shapes: hypersphere, hypertorus, S3*torus, etc.

Light/photons often have funny implications.

At some point, due to expansion, all of the galaxies and stars we now see won’t be visible anymore. But it also means that we won’t feel their gravity anymore.

When there are far less things gravitationally “pulling” each other, quantum gravity supercedes classical gravity. This could pool localized energy together in certain pockets, which would contain vast amounts of particles and, eventually, photons, etc., potentially creating localized gravitational structures or, might I say, mini-singularities scattered all over the universe.

Of course it is not achievable in the current state of the observable universe, but with the notion I provided, I’m really hypothesizing about the state of the universe during or after the photon epoch, where quantum gravity must prevail due to incredibly low matter density. It could strengthen the argument for cyclic models, since this idea could give rise to something reminiscent of a singularity, repeating the cycle eternally, constantly creating new universes over an infinite amount of time.

I’ll also go out on a limb and mention that this could be fertile ground for the theoretical exploration of the baryon asymmetry problem. When one singularity manifests itself into a “big bang,” it could smash into another singularity, where there’s possibly an interplay of unknown physics that could potentially cause a discrepancy between matter and antimatter in localized areas of the universe. Although this would require extensive theoretical modeling, simulations and observational constraints to test viability, I thought it was a unique thought which went along with what I mentioned.

Please let me know your thoughts, I’m just a casual observer with a very curious mind, any feedback, criticism or advice is more than welcome. My biggest hope is for this to turn into a broad discussion because it’s something I’m very interested in learning much more about, and that requires many perspectives. Thank you.

If the universe expanded and enough time passed so that even all the black holes evaporated, the zero point energy field would still exist. Also, if the zero point energy field was the only thing that exists, because of relativity, its quantum fluctuations world be gigantic. This in essence would create an incredibly complex and chaotic and loud universe making the big freeze death impossible.

I read Seven Brief Lessons on Physics yesterday, and watched a video where Rovelli talks about white holes, and I was just wondering if physicists have problems with these descriptions, and if so, which parts, because I thought these descriptions were pretty beautiful and more logical than other theories I've read, but I'm just a layman:

The central result of loop quantum gravity is indeed that space is not continuous, that it is not infinitely divisible but made up of grains, or "atoms of space." These are extremely minute: a billion billion times smaller than the smallest atomic nuclei. The theory describes these "atoms of space" in mathematical form and provides equations that determine their evolution. They are called "loops," or rings, because they are linked to one another, forming a network of relations that weaves the texture of space, like the rings of a finely woven, immense chain mail.
Where are these quanta of space? Nowhere. They are not in space because they are themselves the space. Space is created by the linking of these individual quanta of gravity. Once again, the world seems to be less about objects than about interactive relationships.
But it's the second consequence of the theory that is the most extreme. Just as the idea of a continuous space that contains things disappears, so the idea of an elementary and primal "time" flowing regardless of things also vanishes. The equations describing grains of space and matter no longer contain the variable "time." This doesn't mean that everything is stationary and unchanging. On the contrary, it means that change is ubiquitous-but elementary processes cannot be ordered in a common succession of "instants." At the minute scale of the grains of space, the dance of nature does not take place to the rhythm of the baton of a single orchestral conductor, at a single tempo: every process dances independently with its neighbors, to its own rhythm. The passage of time is internal to the world, is born in the world itself in the relationship between quantum events that comprise the world and are themselves the source of time.
The world described by the theory is thus further distanced from the one with which we are familiar. There is no longer space that "contains" the world, and there is no longer time "in which" events occur. There are only elementary processes wherein quanta of space and matter continually interact with one another. The illusion of space and time that continues around us is a blurred vision of this swarming of elementary processes, just as a calm, clear Alpine lake consists in reality of a rapid dance of myriads of minuscule water molecules.
Viewed in extreme close-up through an ultrapowerful magnifying glass, the penultimate image in our third lesson should show the granular structure of space.
Is it possible to verify this theory experimentally? We are thinking, and trying, but there is as yet no experimental verification. There are, however, a number of different attempts.
One of these derives from the study of black holes. In the heavens we can now observe black holes formed by collapsed stars. Crushed by its own weight, the matter of these stars has collapsed upon itself and disappeared from our view. But where has it gone? If the theory of loop quantum gravity is correct, matter cannot really have collapsed to an infinitesimal point. Because infinitesimal points do not exist-only finite chunks of space. Collapsing under its own weight, matter must have become increasingly dense, up to the point where quantum mechanics must have exerted a contrary, counterbalancing pressure.
This hypothetical final stage in the life of a star, where the quantum fluctuations of space-time balance the weight of matter, is what is known as a "Planck star." If the sun were to stop burning and to form a black hole, it would measure about one and a half kilometers in diameter. Inside this black hole the sun's matter would continue to collapse, eventually becoming such a Planck star. Its dimensions would then be similar to those of an atom. The entire matter of the sun condensed into the space of an atom: a Planck star should be constituted by this extreme state of matter.
A Planck star is not stable: once compressed to the maximum, it rebounds and begins to expand again. This leads to an explosion of the black hole. This process, as seen by a hypothetical observer sitting in the black hole on the Planck star, would be a rebound occurring at great speed. But time does not pass at the same speed for him as for those outside the black hole, for the same reason that in the mountains time passes faster than at sea level. Except that for him, because of the extreme conditions, the difference in the passage of time is enormous, and what for the observer on the star would seem an extremely rapid bounce would appear, seen from outside it, to take place over a very long time. This is why we observe black holes remaining the same for long periods of time: a black hole is a rebounding star seen in extreme slow motion.
It is possible that in the furnace of the first instants of the universe black holes were formed and that some of these are now exploding. If that were true, we could perhaps observe the signals that they emit when exploding, in the form of high-energy cosmic rays coming from the sky, thereby allowing us to observe and measure a direct effect of a phenomenon governed by quantum gravity. It's a bold idea-it might not work, for example, if in the primordial universe not enough black holes were formed to allow us to detect their explosions today. But the search for signals has begun. We shall see.
Another of the consequences of the theory, and one of the most spectacular, concerns the origins of the universe. We know how to reconstruct the history of our world back to an initial period when it was tiny in size. But what about before that? Well, the equations of loop theory allow us to go even further back in the reconstruction of that history.
What we find is that when the universe is extremely compressed, quantum theory generates a repulsive force, with the result that the great explosion, or "big bang," may have actually been a "big bounce." Our world may have actually been born from a preceding universe that contracted under its own weight until it was squeezed into a tiny space before "bouncing" out and beginning to re-expand, thus becoming the expanding universe that we observe around us.
The moment of this bounce, when the universe was contracted into a nutshell, is the true realm of quantum gravity: time and space have disappeared altogether, and the world has dissolved into a swarming cloud of probability that the equations can, however, still describe. And the final image of the third lesson is transformed thus: [...]
Our universe may have been born from a bounce in a prior phase, passing through an intermediate phase in which there was neither space nor time.

​

On Thermodynamics -

Heat, as we know, always moves from hot things to cold. A cold teaspoon placed in a cup of hot tea also becomes hot. If we don't dress accordingly on a freezing cold day, we quickly lose body heat and become cold. Why does heat go from hot things to cold things and not vice versa?
It is a crucial question because it relates to the nature of time. In every case in which heat exchange does not occur, or when the heat exchanged is negligible, we see that the future behaves exactly like the past. For example, for the motion of the planets of the solar system heat is almost irrelevant, and in fact this same motion could equally take place in reverse without any law of physics being infringed. As soon as there is heat, however, the future is different from the past. While there is no friction, for instance, a pendulum can swing forever. If we filmed it and ran the film in reverse, we would see movement that is completely possible. But if there is friction, then the pendulum heats its supports slightly, loses energy, and slows down. Friction produces heat. And immediately we are able to distinguish the future (toward which the pendulum slows) from the past. We have never seen a pendulum start swinging from a stationary position, with its movement initiated by the energy obtained by absorbing heat from its supports. The difference between past and future exists only when there is heat. The fundamental phenomenon that distinguishes the future from the past is the fact that heat passes from things that are hotter to things that are colder.
So, again, why, as time goes by, does heat pass from hot things to cold and not the other way around?
The reason was discovered by Boltzmann and is surprisingly simple: it is sheer chance.
Boltzmann's idea is subtle and brings into play the idea of probability. Heat does not move from hot things to cold things due to an absolute law: it does so only with a large degree of probability. The reason for this is that it is statistically more probable that a quickly moving atom of the hot substance collides with a cold one and leaves it a little of its energy, rather than vice versa. Energy is conserved in the collisions but tends to get distributed in more or less equal parts when there are many collisions. In this way the temperature of objects in contact with each other tends to equalize. It is not impossible for a hot body to become hotter through contact with a colder one: it is just extremely improbable...

Probably a dumb question but here goes.

So I understand that light can't escape the event horizon meaning we can't observe what's on the inside. I also understand the concept that singularities are likely not real and just a failure in our theories at this time.

Isn't the inside of a black hole just all the mass/energy that fell into the black hole? We know all that masses is still there because the gravity exerted by all that masses is still there. But, what else could happen? What do physicists mean when they say "we dont know what's on the inside" though? What more is there other than the mass/energy that went in?

I've read "Black Hole Wars" twice over now, and listened to about all of LS' lectures I've found on YT.

What is the position of the physics community at large on this dispute? How accepted is Hawking Radiation and the presercation of information stuff?

Is this still considered up-on-the-air?

Hi guys, i'm egyptian
i want to know the best countries that i can study cosmology at ?

Let's assume an infinite universe. The first thing I saw came up to scientists that make that assumption, is cloning. And it seems reasonable at first glance. Why? Because you have a finite number of, let's say, building blocks to the universe (aka electrons, up quark, down quark. Although scientists have found out about other different types of quarks that are a bit unstable, but still they appear to be finite). And with a finite amount of "building blocks" of the universe, there is a finite (maybe unimaginably large, although still finite) number of ways these finite building blocks could combine in, which leads them to the assumption that, hey, if there is a truly infinite universe, there has to be repitition of these combinations.

What I see is an invalid way of thinking about this issue is: Why stop there? Why stop at the assumption of an infinite universe? Why not also an infinite number of building blocks that form this universe? Why isn't that a possibility that scientists are taking into consideration?

I mean yeah sure, everything around us (that we can detect) is made up of the same repeating building blocks, and that could fool you into thinking that there is indeed a finite number of building blocks in the universe. But what if that is just not true? What if those building blocks combine in a certain way that the same building blocks align together in the same place (in our case, the observable universe), and other building blocks align in a different place? There is a lot of possibilities in which we could get an infinite universe and also an infinite amount of different, new, places and creatures to explore.

I have been accepted to University of Bologna for Masters in Astrophysics & Cosmology and in Brown University for Masters in Physics. Both are 2 year program with final year contributing towards master's thesis. Bologna offers specialized courses in Cosmo while Brown offers courses Astrophysics and Cosmology; Nuclear & HEP; General Relativity.

I am confused whether I should go forward with Bologna (because my main aim is to gain specialization in Cosmo so that I can further go for a PhD) or with Brown (because its an Ivy League and would open doors to other Ivy's)?

Hypothetically, if cost is not an issue, then what should I go forward with? Which would give me more opportunities and exposure? I am hoping to get some advise or clarification on what should be my priority.

​

P.S. I will have my 4 year Bsc by May (with final year bachelor thesis) from India. I have done a few research projects and fellowships as well.

My question is because I find the term "observable universe" misleading. It's usually the ball of radius X where X is "how far light can have traveled so far." I.e. X is currently around 46 billion light years. So it's the part of the universe where we can currently see its past. But a more interesting concept in a sense would be the present (instead of past) observable universe.

By this, I mean something like, given Earth as a reference frame, the ball that is close enough so that if a photon left right now from that place, it could still outrace Hubble expansion and reach us. Meaning, we still get to see an observation of its present in our future. Instead of, we see an observation of its past in our present.

In other words, the observable universe is an inherently historical concept. Whereas what I'm describing is the (smaller) subset of the universe that still has a chance to send us something new (in our distant future).

You'd have to do a bit of Hubble expansion math to figure out how much smaller this universe would be (I imagine a fair bit smaller). Has anybody done that math? And does this concept exist as a term? Is there some simple reason why my mental model actually makes no sense?

I have posted this question in a number of other subs but I always get down voted. Perhaps I didn't explain my reasoning properly. I remember seeing Brian Greene explain how a spacial dimension could be coiled around another dimension by saying that an ant on a string could go up and down the string and we would see that as one dimension. But. to the and it could also go around the string and we as distant observers would no see that motion. Just as that, if a massive object that was rotated off of our 3 dimensional space may not be observable to us but could still have a gravitational affect on our space. What am I getting wrong here?

Hey! I will be doing a cosmology project this summer. I am taking IB math and physics, and I am also learning Linear Algebra, Multivariable Calculus, and some Abstract Algebra. What math and physics should I study to be able to understand more or less what is going on once I get there? Any guidance would be greatly appreciated!