Stack Exchange Network

Stack Exchange network consists of 175 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.

2
votes
1answer
85 views

Did the observable universe come from nothing?

Does the big bang theory hold that there is a possibility that the whole of the observable universe came out from NOTHING? I mean if all of this universe was occupying an extremely small size of a ...
2
votes
2answers
71 views

Does time stop inside a black hole? How about at it's singularity?

I'm a layperson who just read Brief Answers to Big Question and in the book, Hawking proposes that: A typical black hole is a star so massive that it has collapsed in on itself. It’s so massive ...
1
vote
3answers
109 views

Is there a contradiction between isotropy and the Big Bang? [duplicate]

Disclaimer: I'm not asking whether the Big Bang happened at a point. I'm asking whether the fact that the universe is isotropic and that the Big Bang happened contradict each other. To be honest I am ...
0
votes
3answers
48 views

Questions regarding photons and distance contraction

I've got a few question regarding photons and lorentz contraction. they may be really stupid questions (I am not a physicist). But they have been bothering me for a while. 1. Is Lorentz distance ...
7
votes
1answer
315 views

Neutrino energy density vs photon energy density

So I'm currently following a course in Cosmology and we're covering the densities of different species in the universe right now. Starting from the photon density $\rho_{\gamma}$ we need to derive the ...
2
votes
1answer
69 views

Experimental status of the Big Bang theory

Take the most successful version of the Big Bang theory I'm aware that the Big Bang theory have unanswered questions related to the very first moments of the Big Bang. I also know that for our ...
1
vote
1answer
54 views

Imaginary time concept in S.Hawking's No Boundary proposal, extra-time dimensions and the Big Bang

In this post I will be refering to S.Hawking's lecture: http://www.hawking.org.uk/the-beginning-of-time.html I have a couple of questions regarding the Imaginary time and the Big Bang. In the ...
-2
votes
0answers
29 views

The universe, as a whole? [duplicate]

If the current visible universe looks the same no matter which direction you look, how can it be described as flat? Since the big bang is the current theory of the beginning of the universe, there is ...
0
votes
5answers
82 views

Does the Universe itself move to any direction on top of expansion?

So the universe expands right, but does this expansion move to any direction in hyperspace as an expanding cluster of matter somewhere? It's like if you would explode a bucket of paint under the. ...
1
vote
1answer
77 views

$W$, $Z$ bozons and fermions gained their masses WHEN?

I have read these questions: How does the Higgs mechanism work? How does the Higgs boson give mass to other elementary particles like electrons? What is the difference between the Higgs Boson ...
0
votes
1answer
42 views

Entropy of the big bang

At the moment of big bang, all the matter was in perfect order, that is entropy 0 so what force or disturbance would occur to begin the chaos and the entropy start to increase?
0
votes
1answer
46 views

How did some very large supermassive black holes form in the time span of the universe?

I saw a program recently called "How the Universe Works" discussing Black Holes. One of the enigmas, it seems, is the existence of extraordinarily large 'supermassive' black holes -- black holes of ...
1
vote
0answers
60 views

In what ways is eternal inflation less certain than standard inflation? [closed]

Eternal inflation is the idea that inflation could be eternal due to the effect of quantum fluctuations of the inflaton field. Why do some cosmologists accept inflation, but consider eternal ...
1
vote
1answer
103 views

Why is there equal protons and electrons in the universe?

Matter and anti-matter are asymmetric. Why are protons and electrons symmetric? Would we still have galaxies and stars if there were a strong overall charge?
0
votes
1answer
138 views

Horizon Problem: How did different regions of space acquire different temperatures?

I'm trying to understand the Horizon Problem. Inflation describes how non-causally connected parts of the universe (that we see today) could once have been in causal contact. The reasoning goes that ...
0
votes
0answers
16 views

How would primordial black hole forms if expansion of space overwhelms gravity? [duplicate]

I read that density is quite high in the early universe and many speculate that primordial black hole can form and would probably have a mass similar to a human ovum(egg cell). Usually black hole only ...
0
votes
0answers
12 views

According to the actual understanding, was the Big Bang a singularity in space or rather in density? [duplicate]

Often in cosmology erroneous pictures are transmitted by the recurrent hearing from various sources or by sentences taken out from bigger discussion, and even by omitting adjectives and the likes. I ...
0
votes
1answer
24 views

Higgs Coupling in the moments after the Big Bang

How did the Higgs interaction differ due to the densities, temperatures, pressures, etc. in the moments following the big bang? I am aware that around $10^{-43}$ seconds all the fundamental forces ...
3
votes
3answers
114 views

Could the spatially flat universe start small?

The global space has been measured flat within a small margin of error. According to FLRW, the flat universe has always been infinite. At the time of the Big Bang the universe was infinitely large ...
0
votes
2answers
42 views

Was the singularity just a mini model of our current unvierse? [duplicate]

Did the singularity just "containe" the matter, the energy and the space-time or it created them. If it just contianed them and then the expansion hppened, can we say it was just a mini model of our ...
2
votes
2answers
81 views

Is inflation a possible explanation for what started the expansion?

Alan Guth stated in this article But let me start the story further back. Inflationary theory itself is a twist on the conventional Big Bang theory. The shortcoming that inflation is intended to ...
1
vote
3answers
107 views

How exactly is conformal time, $\eta$, calculated?

As I understand it, Conformal Time is basically the comoving distance divided by the speed of light. $$\eta=\int_0^t\frac {dt'}{a(t')}$$ I can make the connection between the scale factor and redshift:...
0
votes
1answer
74 views

How do we know what happened during the Planck epoch era of the big bang?

The Cosmic Microwave Background provides the left over radiation of the big bang. Cosmologists have theorised what happened at the Planck epoch era of the big bang. Where is the evidence of what ...
0
votes
2answers
66 views

What if humans doubled size… and everything else… could we notice? [duplicate]

After the big bang, everything expanded from a small mass. That expansion is said to be still happening. Imagine if everything observable constantly grew in size. EG. Everything slowly doubled in ...
35
votes
14answers
8k views

How could quantum effects occur in the early universe without an observer?

In inflationary cosmology, primordial quantum fluctuations in the process of inflation are considered responsible for the asymmetry and lumpiness of the universe that was shaped. However, according to ...
1
vote
1answer
31 views

Can a no boundary proposal work without the big bang?

In Hawking's no boundary proposal he assumed that the the amplitude for a state A (such as a given 3-manifold) is the sum of all amplitudes for histories starting at a special big-bang-state (like the ...
1
vote
1answer
103 views

How is Inflation able to create an infinite amount of energy?

Follow up to this question here: If the universe is flat, does that imply that the Big Bang produced an infinite amount of energy? As I understand Inflation theory, some time after the Big Bang, the ...
0
votes
0answers
27 views

How big is the universe 1 second after the Big Bang? [duplicate]

In his book Astrophysics for People in a Hurry, Neil de Grass Tyson starts of with the Big Bang and narrates on what (probably) happened within the first moments of our universe. He further states (p. ...
0
votes
2answers
83 views

If the universe is flat, does that imply that the Big Bang produced an infinite amount of energy?

Too much density and the universe is closed, analogous to a sphere in four dimensions: you travel in a straight line and you end up where you started. Too little and you have a saddle: not sure about ...
1
vote
0answers
28 views

Is it possible to replicate condition at planck time after big bang by smashing 2 protons really hard?

Because we need to achieve really really high temperature to mimick the condition just planck time after big bang, so suppose we can accelerate 2 protons at extremely close to speed of light and let ...
3
votes
1answer
91 views

How long was the first second?

After the Big Bang all of the matter in the observable universe was condensed into a space that was very small (grain of rice sized). The time dilation due to gravity should have been very large. So ...
-1
votes
1answer
65 views

Does space expansion increase potential energy, and hence increase mass?

As space expands the gravitational potential Energy increases. So does the potential energy between Atoms and quarks and so on. I have read several times that these effects are so minuscule that they ...
0
votes
0answers
29 views

BBN: How is the expansion rate related to the freeze-out of Neutrons?

I've been making my way through several papers and textbooks on the subject, but they all seem to gloss over this subject: how is the equilibrium of protons, neutrons and photons related to the ...
1
vote
1answer
81 views

Is the Big Bang a naked spacelike singularity?

While reading some answers on similar topics, I was wondering about the nature of the Big Bang singularity in the standard cosmological model. I know it's a spacelike singularity that have a ...
1
vote
0answers
59 views

Could the horizon problem be explained by a finite universe instead of inflation?

Suppose the universe is finite (either closed or open with a non-trivial topology), any point could be within the horizon of another.
17
votes
4answers
3k views

Could quantum fluctuations spawn real matter?

Would it be plausible for fluctuations in the QED vacuum to spawn actual matter (such as quarks, electrons the constituents of a hydrgen atom) given enough time and space?
5
votes
1answer
182 views

Where is all the Antimatter?

This is obviously a duplicate of If matter and antimatter... However, it's now four to five years after a swarm of videos were made on this subject. At the time, there was a consensus that the LHC ...
4
votes
2answers
162 views

Big Bang: what is it exactly that is expanding?

I have read a bit about the Big Bang over the years, but being no physicist I have never been able to really understand what it is about. As far as I know, starting with Hubble we have been able to ...
1
vote
1answer
33 views

Effective low energy actions in string cosmology

I wonder why can SUGRA actions be used in string cosmology, since in some cases they are used to model big bang scenarios (for example the pre big bang scenario in chapter 4 of Gasperini's "Elements ...
0
votes
0answers
21 views

Does the universe has a center like a real explosion? [duplicate]

I don't really know much about cosmology but I was thinking one day about the center of the universe. Now 'Big Bang' was the birth of our universe. Then Shouldn't the place (or region of space) where ...
1
vote
1answer
59 views

How was electrical charge formed in the Big Bang?

We know that fundamental particles (Quarks, electrons, etc.) were formed a while after the Big Bang. How was their electrical charge (its value and sign) determined? Was electrical charge present in ...
0
votes
1answer
76 views

How far can an atom collapse under gravity? [closed]

Can an atom condense (collapse?) under gravity to a volume less than the nucleus? The Big Bang is the example motivating the question - if the entire mass of the universe is condensing to some ...
0
votes
1answer
69 views

How did Big Bang determine the initial conditions of the universe?

My question is that how did the Big Bang determine the initial distribution of the particles and their wavefunctions? In theories like Bohmian mechanics or Many worlds, how was the universal ...
3
votes
1answer
64 views

Is Gravity still considered to be part of the “Superforce” which existed at the instant of the “Big Bang”

My limited understanding of the Big Bang is that all the Fundemental Forces (Electromagnetic, Weak Nuclear, Strong Nuclear and Gravity) were originally part of a "Superforce." As the universe cooled ...
1
vote
0answers
134 views

Why am I a Boltzmann brain?

The Boltzmann brain hypothesis states that a big-bang-causing entropy fluctuation is larger than a brain-causing entropy fluctuation, therefore, you are much more likely to be a BB rather than a wet ...
1
vote
1answer
33 views

Curvature in space time during Big Bang and present scenario

Space time in the presence of masses is curved. But during the time of Big Bang it's presumed that all the matter in this universe was at a single point, so it must have been super dense and had very ...
0
votes
1answer
52 views

How large was the universe at the start of BBN? How large was it after?

I'm trying to get a handle on the basics of BBN. I've read several authors quote the figure of 17 minutes. So BBN started at 3 minutes and ended at 20 minutes after the start of time. So how large ...
0
votes
2answers
119 views

Hubble's time and the age of the universe

If Hubble's time is the inverse of a changing Hubble's "constant" and it estimates the age of the universe up to now, since Hubble's parameter is converging to an actual constant value, how can the ...
0
votes
0answers
25 views

what are possible explanations for the larger scale anomaly in Planck satellite's data?

In the Planck satellite's image of the Cosmic Microwave Background (CMB), there have been anomalies, the most important of which is a deficit in the signal at large angular scales on the sky, which is ...
2
votes
0answers
90 views

What was the informational content of the universe at the Planck time?

If the energy of $1 \, \mathrm{bit}$ of information is $k_{\small{\text{B}}}T \ln{2}$, then the energy of that bit increases with the temperature of the system. When I try to calculate how much energy ...