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.

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Time from big bang to here [duplicate]

New to this so apologies for my ignorance, the simpler the answer the better. Here goes. Light took 13.5 billion years to get to us from the big bang. On an imaginary neighboring planet that is much ...
Nick Yiannop's user avatar
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Analytic expression for a universe without a big bang [duplicate]

I was reading introduction to modern cosmology by Andrew Liddle. On page 56 he shows a graph of the $\Omega_{\Lambda}$, $\Omega_{0}$ plane and there's a region where no big bang is needed, later on ...
Muñoz Castro Yusef's user avatar
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How was the universe once small enough to be subject to quantum mechanical effects?

I have often read that our universe was once small enough to be subjected to quantum mechanical effects, potentially altering how our universe turned out. This is a large theme in Laura Mersini-...
cosmicpawn's user avatar
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Do all galaxies in our observable universe have more or less the same age?

What is the current consensus about the age variation of the existing galaxies in our observable universe? Not to be confused with the age of very distant galaxies as observed today by our telescopes ...
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How can there be a Big Bang without a singularity?

I have read to Sean Carroll that he says that the Big Bang model is correct, but the Big Bang event is incorrect, so what is the difference? And everyone knows that the Big Bang model is linked to ...
مروان حسين's user avatar
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Big Bang and where do we stand relative to it? [duplicate]

Maybe dumb question, not sure, but I would need some help here to understand. https://theglobestalk.com/james-webb-telescope-see-back-in-time/ So according to physics we can look back in time ...
Panagiotis Bougioukos's user avatar
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No symmetries in the universe at the Big Bang...?

I apologize in advance if this is a stupid question but... According to some scenarios about the beginning of the universe (namely cosmological inflation), in layman terms, everything was born out of ...
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Matter-antimatter asymmetry during hadronization

When quark gluon plasma is created during heavy ion collisions, the QGP exists extremely briefly before hadronizing--the process where the QGP cools and quarks combine to form colorless hadrons. A ...
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Can the quark-gluon plasma of the very early universe be accurately characterized as a type of quark star?

The very early universe was dense and opaque. During the quark epoch, the entirety of the universe, up to every boundary, was a filled-in ball of QGP. Much like a star is a ball of ionized nuclei that ...
blacktopshaman's user avatar
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Were all particles once bosons?

For all matter to have been occupying the same point in space, this would violate the Pauli exclusion principle. Since fermions cannot occupy the same quantum state, the particles that are now ...
blacktopshaman's user avatar
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Is there any remote possibility that a singularity may be real? [closed]

Usually, when physicists talk about singularities in Einstein's theory of relativity, they say that these cannot exist and that they are only mathematical artifacts that indicate that is likey that ...
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In the Steinhardt's bouncing cosmology, how would the CMB differ for patches close to pre-existing black holes

In Steinhardt's bouncing cosmology model, during the contraction phase the Hubble radius shrinks to microscopic sizes, although the overall contraction of the universe is much less significant. Each ...
cosm_ques's user avatar
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Why is it surprising that the universe was in an extraordinarily low-entropy state right after the big bang? [duplicate]

So I don't understand why it's surprising that the universe in an extraordinarily low-entropy state right after the big bang? The way I see it the second law of thermodynamics forbids almost anything ...
More Anonymous's user avatar
7 votes
2 answers
386 views

Why is the deuterium bottleneck temperature 0.1 MeV?

During big bang nucleosynthesis (BBN), deuterium has a lower binding energy per nucleon (~1.1 MeV) than the other similar nuclei, and so prevents heavy elements from forming until the temperature ...
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Solving this first-order differential equation for neutron abundance using given data

The time rate of change of neutron abundance $X_n$ is given by $$\frac{dX_n}{dt} = \lambda - (\lambda + \hat\lambda)X_n$$ where $\lambda$ is neutron production rate per proton and $\hat\lambda$ is ...
Gurbir Singh's user avatar
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Was Big Bang the "START" of time? [duplicate]

I know that this question has been repeated a lot. But I still don't understand this concept. Big bang created matter and space but how could it possibly create time? If Big bang didn't create time ...
MpH81679's user avatar
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Is the big bang (BB) correctly summarized as a sequence of symmetry-breaking events? [closed]

Please take this as a serious question from a curious yet deeply underinformed lover of this universe. This is more of a basic question concerning the overall mechanics of the transition stages from ...
blacktopshaman's user avatar
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Did time have a beginning? [duplicate]

Did time have a beginning in the current scientific consensus? Or has it existed forever?
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Why is Big Bang so misunderstood?

I was reading this answer where it's explained that the Big Bang is not a theory but a model and that it doesn't say anything about the origins of the Universe. I was taught in school instead that ...
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4 votes
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If dark matter was created in the early universe and its formation released energy, is there any evidence of that energy in the cmb?

When atomic nuclei fuse, energy is released. Is there anything about the CMB energy distribution that suggests that dark matter could have formed from other particles that released energy?
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The common explanation to what happens before the Big Bang is wrong? [closed]

When you ask a physicist what happens before the big bang, they will say - the question does not make sense cause there was no time, hence no "before" etc. And that Time appeared with the ...
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Why didnt early universe collapse into black hole? [duplicate]

Given the early universe was infinitely small, why didnt it immediately collapse into a blackhole before it had time to expand?
Chris Glass's user avatar
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Why can't we run the laws of physics backwards and forwards in time infinitely?

So assuming we know all the laws of physics in differential equation form, and I have an estimate for the current large scale state of the universe (whatever standard assumptions/data cosmologists use ...
Ameet Sharma's user avatar
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LCDM epoch or point where it fails

Nobody denies the currently success of the LCDM of cosmology. Recently, I wondered myself if there is a point or epoch (beyond the space-time singularity) where it breaks down. Does it fail at phase ...
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Is anti-desitter cosmology internally consistent?

In the string landscape all known vacua that have been found have been anti-desitter (negative cosmological constant). Is there any cosmological or physical principle that may rule out anti-desitter ...
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What happened to particles with less energy than their rest mass?

Today, particles like electrons can only be created if there is enough energy that exceed their corresponding rest-mass energy. As far as i understand, all particles were massless before the higgs ...
Anon's user avatar
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When was the Higg's particle created after the Big Bang?

Was the Higg's particle created with the Bag Bang?
user382965's user avatar
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What were the first particles, according to different models?

At what point, and in what cosmological epoch, did particles begin to exist? What particles were they? My understanding is that things as we know them involved the Big Bang singularity, and that the ...
blacktopshaman's user avatar
1 vote
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Can we infer the size of the whole universe from its expansion rate? [closed]

If the universe inflated to 100 billion km in its first second, that suggests only 1/160,000 of it was observable from any point at that moment. The expansion rate slowed after that, of course, but ...
Doradus's user avatar
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Why is cosmological time unique?

According to the definition I have encountered for the concept of cosmological time, it is defined in the following way: The cosmological principle states that, at each location in the universe, it ...
Wild Feather's user avatar
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Can the temperature of the extremely early universe be negative? If so, does it have any measurable consequences?

We know at the Big Bang the universe is extremely hot. We also know that what is hotter than infinite temperature is negative temperature, provided that the system has an upper bound for energy, or ...
pathintegral's user avatar
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Why doesn't temperature of recombination epoch coincide with Hydrogen plasma transition?

The temperature of recombination epoch was 3000-4000K. The temperature of Hydorgen transition to plasma is >10000K. Shouldn't they coincide? Why not then? Is this because of lower pressure, than on ...
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Has it been proven the fine-structure constant (FSC) changes with time?

I have heard this claimed over and over, even that the FSC was 1 at the Big Bang. Is there any actual consensus among scientists that this is so?
Derek Seabrooke's user avatar
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What have been the biggest factors for the increase in entropy in the universe?

Entropy has been increasing since the Big Bang. But how? It seems relatively intuitive, but the universe is cooling down. Often when things cool down, entropy decreases. So why, in the case of the ...
Lara's user avatar
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Isn't the universe older than 13.8 billion years? [duplicate]

To preface this, I'm not an expert, I'm just an avid astronomer with little mathematical knowledge. I was watching a video that was explaining the cosmic scale and how the observable universe is only ...
JamesM's user avatar
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Time dilation between now vs right after the Big Bang should imply the universe is much older than 13.8 bn years? [duplicate]

The universe is said to be 13.8 bn years old. But if we go back in time towards the Big Bang singularity time will slow down more and more and eventually stop because of the density of the singularity....
Gandolph's user avatar
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1 answer
270 views

Size of the universe 13 billion years ago

When wee look at the sky in opposite directions, we can see early galaxies that were formed about 13 billion years ago. At that time, the distance between two such galaxies at the opposite ends of the ...
Wolphram jonny's user avatar
1 vote
1 answer
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How can we know if our big bang is a one side of a wormhole?

According to Hawking, he proved that (excluding quantum mechanics) the big bang started at a singularity. Hence showing a connection between the mathematics of the big bang and black holes. Equally, ...
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1 answer
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Could an observer in time determine whether time had no beginning or had a beginning infinitely long ago? [closed]

I don't know if this is more a question for mathematicians or physicists (or even philosophers), but what would be the difference between time having a beginning infinitely long ago and time having no ...
Michael Greaney's user avatar
2 votes
0 answers
107 views

Was Big Bang a phase transition? [closed]

Was Big Bang a phase transition (critical phenomenon)? If "yes", what is the order parameter and what determined the value of the order parameter chosen? When talking about phase transitions ...
Roger V.'s user avatar
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"What" was expanding during the Inflationary epoch?

I know, space. But in my opinoin, space makes only sense if there is something that experience things like position and distance. A universe without anything that require position and distance to ...
Anon's user avatar
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6 votes
1 answer
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We say the big bang (initial singularity) didn't happen at a point, but is it the same with the singularity of a black hole?

I have read this question: The simple answer is that no, the Big Bang did not happen at a point. Instead, it happened everywhere in the universe at the same time. Consequences of this include The ...
Árpád Szendrei's user avatar
1 vote
0 answers
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Dark energy/dark matter erodes confidence in origin theories [closed]

My layman's understanding is that we believe we have a good understanding of the development of the universe after the instant of the Big Bang. Also, I understand that we believe that about 95% of the ...
Ken's user avatar
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3 votes
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Why is most of the matter in the universe made of hydrogen instead of helium? Or iron?

Hydrogen, while being the simplest element, is near a peak of the binding potential curve. Presumably in the first 1 second or less of the Big Bang timeline, densities and temperatures were such to ...
RC_23's user avatar
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Can the universe break like a balloon that pops?

I have been investigating inflation and the big difference in the theoretically predicted value of the cosmological constant and the actually measured value of it. There would be 120 orders of ...
Ward Blondé's user avatar
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1 answer
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How Existence Of Matter Is Possible Inside The Black Hole? [closed]

According to Chronology of the universe, origin of the universe initiated as per below sequence: Big bang (at 0 sec) occurs in the black hole (10^-35 m in size, Planck Length) at the center of the ...
Satyajit Patidar's user avatar
9 votes
2 answers
4k views

Why do we need inflation?

wiki (https://en.wikipedia.org/wiki/Inflation_(cosmology)) says that immediately after BB there was expansion at speed greater than $c$, what makes this necessary, what would happen if expansion took ...
user avatar
2 votes
1 answer
146 views

Particle horizon in an empty universe

So in this thread, Can space expand with unlimited speed?, the author Pulsar made amazing diagrams of different horizons and paths for a benchmark model that describes our current universe, and gave a ...
ABC's user avatar
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1 answer
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Cosmos at minimum 250x bigger than our observable Universe, so why then the need for a Big Bang?

Please correct me If I'm wrong but does not the BB only refers to our light speed limited observable Universe (OU) from our home position? Also it is estimated that the Cosmos is minimum 250 times the ...
Markoul11's user avatar
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Is a meter constantly getting bigger? [duplicate]

If the bigbang is the start of the expansion of space everywhere then does that mean that a 1 meter ruler is bigger tomorrow than it was today? Does this apply to the size of atomic particles and ...
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