Stack Exchange Network

Stack Exchange network consists of 174 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

Questions tagged [big-bang]

According to the current cosmological theories, it's the model that explains the early life of the universe, starting from a rapid expansion of hot and dense matter.

4
votes
2answers
141 views

Was the universe already expanding before inflation occured?

Was the universe already expanding before inflation occured or did inflation cause the universe to start off expanding? By “cause it to start off expanding” , I mean the cause of the initial ...
0
votes
1answer
75 views

Would eternal inflation be really eternal since quantum fluctuations are usually very rare and very small?

I’ve read somewhere that quantum fluctuations in the inflaton field are usually very rare and very small. If the effect of quantum fluctuations pushing the potential uphill is too rare and too small ...
1
vote
1answer
107 views

Is there any way to tell if the Big Bang happened everywhere or just in some regions of the entire universe?

On large scales, matter seems to spread uniformly in our observable universe so we think the Big Bang happened everywhere in the observable universe. Is there any way to tell if the Big Bang happened ...
1
vote
1answer
102 views

Heat death in eternal inflation

Heat death is the predicted fate of the universe. Eternal inflation theory states that new hydrogen atoms are created in each pocket universe so that means new hydrogen atoms are still being created ...
0
votes
2answers
80 views

Does object from which the universe is created still exist in its original form? [closed]

If time is passing more slowly near objects with bigger gravitational mass, could it be that the time at the object from which the universe is created has not started yet (or very little of time has ...
2
votes
2answers
109 views

How do we know the universe is expanding and wasn't already infinite?

From what I know, the decision that the universe was expanding came from the discovery of the redshift and that other celestial objects, such as galaxies, were moving away from us; the farther they ...
1
vote
2answers
57 views

In what sense the scale factor $a(t)\to 0$ lead to the big bang singularity?

How do we understand that the limit $a(t)\to 0$ (where $a(t)$ is the scale factor) lead to a spacetime singularity? Is it by substituting $a(t)$ in the FRW metric and concluding that space makes no ...
1
vote
0answers
90 views

How was it possible for the big bang to occur?

I think the person who asked this Phys.SE question meant a different thing than any of the people who wrote an answer thought so I'm asking what I'm guessing the author probably really meant. If there ...
0
votes
1answer
31 views

The surface of the last scattering and pictures of deep field

Maybe this question (in fact I have a few of them) is naive but nevertheless, let me try to ask it: it is concerning the furthest regions of our universe. Is the Hubble telescope capable to ...
2
votes
1answer
69 views

How is the primordial abundance of Lithium measured?

I was reading about the "Lithium problem" and I came across this Physics SE post: Discrepancy problem in lithium? The answer mentioned On the other hand, measurements of the $\rm Li$ abundance ...
0
votes
1answer
98 views

Alexander Vilenkin - The Universe probably had a beginning [duplicate]

Is it true that the Universe can not have an eternal past? It seems like Alexander Vilenkin tries to argue this? Does this imply that the Universe had a beginning? Link to his publication regarding ...
5
votes
1answer
96 views

How far back in cosmology is there observational evidence?

It seems "the first three minutes" are well established... back to the first second? 10 seconds? What about the "hadron epoch" going back to the first microsecond? Or before that? I know there are ...
0
votes
1answer
100 views

Could matter in the universe come from some process other than the decay of inflaton field?

Could matter in the universe come from some process other than the decay of inflaton field? Do we have any theoretical reasons that support the idea that matter was created from the decay of ...
0
votes
1answer
99 views

Did negative pressure cause the universe to start off expanding at the big bang?

What caused the universe to start off expanding in the first place. Was it negative pressure that drove the initial expansion or was it just something else?
1
vote
1answer
134 views

Why do we think that the energy density of false vacuum/scalar field doesn’t dilute with the expansion?

I have a question about inflation theory. Why do we think that the energy density of false vacuum/scalar field doesn’t dilute with the expansion? Could it be that the energy density does dilute with ...
3
votes
3answers
108 views

How do you explain cosmological red shifting in terms of gravitons?

We know that the photons from the big bang are continually being red shifted and losing more and more energy. In terms of the graviton view, how would you explain that? Where is the energy going? Are ...
1
vote
1answer
87 views
-1
votes
2answers
259 views

Apparent contradiction between First and Second Laws of Thermodynamics

How is the Second Law of Thermodynamics not either false or incompatible with the First Law of Thermodynamics? In practice, the Second Law entails that, given an infinite amount of time, there should ...
0
votes
0answers
18 views

Was the big bang a black hole that collapsed [duplicate]

I know this might be a silly question and maybe a bit off topic, but I wonder, could the big bang have been the collapse of a gigantic black hole in which all off its contents was pushed out? I have ...
2
votes
0answers
49 views

Matter generation during cosmic inflation (Hawking radiation like…)

Is there any estimation of how much of the matter in the observable universe was not created during the big bang, but later during cosmic inflation? My thought is as follows: Suppose we are in the ...
0
votes
0answers
32 views

The location of Big Bang [duplicate]

Every lecture I've attended, book I've read, or TV show watched explains that the universe was once no larger than the Milky Way, or the solar system, wait, it was so small that it could fit in a ...
3
votes
2answers
73 views

Is it sensible to talk about protons at the time when the universe was a quark-gluon plasma?

I'm currently studying from "Particle Astrophysics" by Perkins. On page 132 it says: After $kT$ fell below the strong quantum chromodynamics (QCD) scale parameter ∼ $200$ MeV, the remaining ...
0
votes
0answers
36 views

During big bang, everything expands same rate, homogenous, isotropic, nothing pulled towards each other. Did quantum randomness form stars, galaxies? [duplicate]

During big bang, space expands separating everything at the same rate, homogenous and isotropic, nothing is pulled towards each others. Did quantum randomness form stars and galaxies? If there is no ...
1
vote
1answer
62 views

Would the universe be significantly different if neutrinos were massless?

As far as I know, neutrino oscillation experiments have fairly conclusively demonstrated that neutrino states have mass. However, neutrinos are so frequently taken to be massless in cosmology that I ...
1
vote
0answers
69 views

How far are we from the “edge” of the universe? [duplicate]

According the the Big Bang theory, the universe started as a 0-dimensional point of infinite density. Shortly thereafter, it underwent inflation and grew to some measurable size, and continues growing ...
1
vote
1answer
53 views

Temperature after the big bang

I was just wondering about possible extreme temperatures. It came to my mind that shortly after the supposed big bang the universe was probably at its hottest in its entire Lifetime. But does it even ...
-2
votes
1answer
65 views

How to explain curvature of spacetime at the time of big bang [duplicate]

According to Einstein mass causes curvature of spacetime ,so he basically defined mass using space i.e (mass is something which causes curvature of spacetime).Now at the time of bigbang there was no ...
3
votes
2answers
111 views

Why did CMB decouple when neutral atoms formed?

Atoms can absorb and emit photons. But it is said that when the neutral atoms were first formed the photons got decoupled. If the atom-photon interaction is allowed how can we say that photons were ...
1
vote
1answer
67 views

Does the big bang model describe a first momment in time for the entire universe or just the observable universe

The big bang model describes the universe as contracting as we wind time backwards. Since the observable universe is of a finite size this ultimately sets the first moment of time at around 13.8 ...
2
votes
2answers
76 views

Can we have bubbles of the tenth dimension in our universe?

If the gap between the branes in the Big Bounce theory is the 10th dimension, and branes have wrinkles as they collide, can our universe have 'bubbles' in the 10th dimension? This is in reference to ...
1
vote
1answer
54 views

What is energy debt?

What exactly is energy debt and why does not having energy debt mean that particles and antiparticles don't instantly annihilate each other. I'm struggling to understand why this happens (quote from ...
12
votes
4answers
2k views

Does the fact that energy is not conserved in cosmology open the possibility of new matter/atoms being created in the universe?

Does it open the possibility of new baryonic matter/atoms being created in the universe and avoiding the Heat Death of the universe?
1
vote
2answers
66 views

Size of the Universe at end of recombination (~477000 years)?

What was the size of the Universe at start of recombination (377000 years) when the Universe started to become transparent and release of trapped photons into what we now know as the CMB and till end ...
0
votes
0answers
35 views

Reconciling the Hubble time with the non-constant recessional velocity of galaxies [duplicate]

Two ideas about universal expansion seem inconsistent to me. Many of you will be familiar with the stretching rubber sheet analogy for the metric expansion of the universe, however I will detail it ...
0
votes
0answers
58 views

Is it the same time, does time pass at the same pace everywhere in the universe? [duplicate]

According to big bang cosmology, the universe has a beginning, a definite age. Does this mean that it is the same time, that time passes at the same pace everywhere?
0
votes
1answer
95 views

Pauli principle before big bang [closed]

i understand that the Pauli exclusion principle states that two fermions cannot occupy the same quantum state. This question is not about a black hole. It is more about the singularity at moment of ...
4
votes
2answers
122 views

Why abundance of matter requires fundamental asymmetry - cannot be statistical symmetry breaking?

There are rather no doubts that there is more matter than antimatter in our Universe, it is usually assumed that it was created during short baryogenesis (violating baryon number conservation) period ...
1
vote
1answer
54 views

If the observable universe after inflation was all there was, would this form a black hole?

There have been other similar questions, but none of the answers address this point. Inflation ends after the first 10^-32 seconds. Our observable universe was the size of a grain of sand that ...
0
votes
0answers
45 views

How are the temperature, density, and size of the Universe calculated during the first few minutes after the Big Bang?

I'd like to know the assumptions cosmologist use when they give a timeline of temperature, density, and size of the universe from $T=0$ to $T=$ a few minutes later, as Steven Weinberg did in his book, ...
1
vote
0answers
135 views

Can matter/antimatter “annihilation” produce “dark matter”?

I was thinking about the following reasoning: If a matter and antimatter reaction produces energy, this energy would have particles itself. I found out (reading...) that one (the main?) product are ...
0
votes
0answers
102 views

Why does it even need a matter / antimatter asymmetry? (No mixed visible universe) [duplicate]

Summary: Why can't the missing antimatter simply be outside the observable universe? Always when I hear about the big bang mystery why there is only matter left, it is said that there needs to have ...
0
votes
1answer
81 views

What is the difference between a quantum fluctuation and a singularity in the beginning universe?

I am sure this is a naive question that shows my lack of sophistication in physics but I keep reading "the early universe was a "singularity", on the other hand ..... I also see quantum fluctuation ...
1
vote
1answer
179 views

TV snow and Big Bang

How come the white and black snow we see sometimes on TV is a result of the Big Bang? (the cosmic radiation) I meant the random dot pixel pattern of static in TVs, when there is no signal.
-2
votes
1answer
102 views

Can light be one of the causes for the expansion of universe? [closed]

first of all, is the universse infinite or finite? If finite, then the universe is itself expanding, so if you assume the farthest star in the farthest galaxy emits light. The photon would be able ...
0
votes
0answers
35 views

What are the current cosmology models of the universe before the big bang? [duplicate]

What are the current models of the pre big bang nature of the universe? The post big bang scenario or model might be just one phase of the evolution of the universe.
0
votes
2answers
93 views

Entropy in the early universe

If entropy must increase for any real process and natural processes move from order to disorder then the early universe must have been "highly ordered". However, when I think of the extremely dense ...
1
vote
0answers
23 views

Why temperature gets so hot a fraction of seconds right after big bang?

I read that right at the moment of big bang, time and space are created and there is only quantum fluctuation, so there should be no temperature because photon and many elementary particles did not ...
0
votes
2answers
451 views

Where did the energy for the big bang come from? [duplicate]

Conservation of energy entails that all energy in the present has existed for all time. Therefore, this implies that the big bang was initiated with preexisting energy. Where did this energy come from?...
1
vote
0answers
27 views

Does the virial theorem prohibit dark matter BH's on any size or timescale, or just make them very unlikely?

I've read other Q's on dark matter/black holes, but none seem to be technically specific enough to clarify this point. I understand so far, that because classic CDM doesn't interact in ways that ...
0
votes
1answer
82 views

How were atoms able to form after the big bang?

How where atoms able to form after the big bang? From my understanding all the materials to form atoms were floating around and by random chance they collided and created atoms. If the universe was ...