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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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Big-crunch divergence? (Not very serious) [closed]

Slightly whimsical question, inspired by Poul Anderson's story "To Outlive Eternity" and novel "Tau Zero." If the Big Crunch model of cyclic cosmology actually applies in some ...
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As per Friedmann Equations, is big-bang singularity necessary?

The Friedmann Equations do not directly require that the scale factor $a(t)$ was zero in the beginning. Since Einstein's static universe is still a valid solution, is it possible that before the Plank ...
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Will expanding space rupture an empty box floating in outer space

Under the theory that space itself is expanding, but the space inside of atoms and molecules doesn't expand because nuclear and electromagnetic bonding forces exceed the forces that expand space, ...
mdswartz's user avatar
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Simple question about finite Universe [duplicate]

If, by Big Bang, Universe was created from initial singularity, with finite "speed" of expansion of matter, shouldnt it be finite as well?
Влад Дедков's user avatar
3 votes
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Free Neutron Decay

I've read that free neutrons can decay into hydrogen, but it's rare because the energy from the decay usually sends the electrons away, unable to bind with the protons. But if trillions of free ...
mdswartz's user avatar
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Is there an estimate for how many monopoles would be produced in the very early universe?

The question really hits it with this one. I haven't really found some good numbers other than the whole “It'd be so many (per Hubble vol) to recollapse the universe”. I don't know if that comes of as ...
Mike's user avatar
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Cyclic Universe Problems

In Penroses's hypothesis, at the end of each iteration the universe undergoes a conformal transformation, meaning distances are rescaled. If I am right, it implies that a planet from the previous ...
Nayeem1's user avatar
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Inflation in background free models of the universe

There are many authors who are attempting to construct a model of physics that doesn't rely on the objective existence of spacetime. This is part of the work in quantum gravity. This leads to things ...
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Does the fact that we are able to see CMBR implies that universe expanded faster than light?

Supposedly, the universe underwent rapid expansion immediately after the big bang, surpassing the speed of light. If we can detect remnants from that era, does this suggest they moved faster than ...
Mr. Spock's user avatar
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2 answers
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Could Space and Time Be Decoupled Pre- Big Bang?

The traditional view holds that both space and time emerged together from the Big Bang. However, I'm curious about the possibility that time could be eternal, with no beginning, while space began to ...
VVM's user avatar
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Is cosmic background radiation the same photons bouncing around?

Or are "new" photons from perhaps later stages of the expansion encountered?
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Is the matter-antimatter asymmetry a logical or a statistical problem?

When I read on Wikipedia about Big Bang (Inflation and Baryogenesis), I got the impression that in the beginning of the universe all matter and antimatter had been created exclusively as pairs: ...
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If we consider the spacetime of the universe to be four-dimensional, does the Big Bang lie in its center?

Apologies for the (hopefully now somewhat less) clickbait-y title. Now, of course, I know that the Big Bang did not happen at any point connected to a single point in our current $3$-dimensional ...
paulina's user avatar
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Are there any observations from the beginning of the universe until the CMB?

The question that concerns my mind is that in the time period before the cosmic microwave background, did humans have any observations or not? I mean, are all the materials mentioned in physics about ...
QQQ's user avatar
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1 answer
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Was the singularity a boson? [closed]

I was wondering if there is any truth in the perspective that the singularity point at the beginning of our universe would be considered a boson. I have heard it said that the universe at that one ...
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What would one use a theory of quantum gravity for?

I am generally wondering how useful new more ambitious theories would be considering that even with standard non-relativistic electrostatic QM one usually has to employ unsatisfyingly crude ...
Zaph's user avatar
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Probability of a primordial black hole absorbing background radiation?

I'm thinking of the early universe when there was a lot of energetic radiation around. A primordial black hole (PBH) that would be about to evaporate completely about now, would have an initial mass ...
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A problem on cosmic inflation

I analyze inflation in this following scenario: Suppose that at some very early epoch, $t_1 ≤ t ≤ t_2$ (where $t_1 ≪ t_2 ≪ t_r$ and $t_r$ is the time at the recombination epoch), the universe resides ...
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Unification of Interactions

It has been asked before but with a different aim, and was answered mathematically, while I look for a practical understanding of it. If the Four Foundamental Forces were unified in the first instants ...
FringesExplorer's user avatar
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Time of deuterium bottleneck

in lectures we derived that the time for the deuterium bottleneck to pass (the time after which deuterium production is possible) is $t_D = (\frac{kT_D}{1MeV})^{-2} s$ (edited, used to lack s), where $...
NX37B's user avatar
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Could primordial black holes have been supermassive?

Usually when primordial black holes are mentioned, they are imagined to be tiny. Could they have been supermassive? This would explain the existence of quasars in early universe.
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Big Bang Escape Velocity

When our entire section of the universe was in a single hot dark dense state, right before our big bang, what was the escape velocity?
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Another universe due to a rogue wave fluctuation

Let us consider our Universe at its heat death state, and the rogue wave phenomenon that is due to improbable superposition of small waves. Is it possible that a rogue wave-like quantum fluctuation ...
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Do we still not know whether the universe had a beginning? [duplicate]

The Question: According to Prof. Brian Cox in the first 30 seconds of this YouTube video from 4 years ago, we do not know whether the universe had a beginning. Is it still the case that we do not ...
Shaun's user avatar
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How low can the scale of cosmological inflation be?

Usually, when we think of inflation we think of it happening at high energy scales, close to the bound set by CMB polarization measurements (with a Hubble scale of $H_I\sim 10^{14}$ GeV). However, ...
illa_94's user avatar
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What model tells us there is nothing outside the universe?

Is there an existing model or theory that shows there is nothing outside of the universe that interacts with anything inside the universe? Or to put it in other words, is there a model or theory ...
foolishmuse's user avatar
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13 votes
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Why is the horizon problem a problem?

I am curious about physics and astrophysics in particular, although I have no academic basis. Usually, I find it easy to understand the concepts and explanations, but I have particular difficulty in ...
Alaor's user avatar
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Cause of the light curtain after big Bang?

In the current model of the big bang there is a short phase of some minutes, where all the light in the universe was trapped. Which mechanisms were able to disable the expansion of light in this phase?...
Andreas Macher's user avatar
2 votes
5 answers
506 views

What is the branch of physics that asks the question 'what was before the Big Bang'?

What is the branch of physics that asks the question 'what was before the Big Bang', assuming the Big Bang is truly what happened at the beginning of the universe? If there could be a better model ...
Bruce M's user avatar
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3 answers
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If the observable universe had only one galaxy, how would people know the expansion of the universe?

Hubble measured high redshifted galaxies to discover the cosmic expansion. In a hypothetical universe where only one galaxy exists, would there still be observational evidence for the Big Bang theory? ...
user74750's user avatar
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Why isn’t $\rm H_2 O$ a primordial element? [closed]

We’re told the universe was very hot and energetic immediately after the Big Bang, and just shows H2O was present early on. Yet, it is not considered to be a primordial element. Why is that?, and what ...
Patrick Payne's user avatar
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1 answer
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Common clock reference of Big Bang

Relativity tells us that there is no preferred reference frame, yet current cosmology does operate on the hypothesis that all points in the observable universe originate from the same big bang ...
Freedom's user avatar
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7 votes
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How can micro black holes exist?

How could a micro black hole exist, when there is so little matter to produce the intense gravitational force required to crush matter to that extent? It takes the collapse of a supermassive star to ...
Peter R. McMahon's user avatar
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0 answers
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Complete Old Figure of Friedmann Universe Models

I have found this quite old figure (R. D'Inverno, Introducing Einstein's Relativity. Clarendon Press, 1992) that I want to modernize for a course using TikZ/LaTeX. My questions are: Do you know if ...
Vincent ISOZ's user avatar
10 votes
6 answers
4k views

Why do we say that temperature of Universe is around 2.7 K?

I am little confused, so please correct me if I am wrong. Temperature of Universe is calculated using cosmic microwave background and it is around 2.7 K. The cosmic microwave background is the relic ...
SacrificialEquation's user avatar
4 votes
1 answer
892 views

What important milestones happened in the first attosecond after the Big Bang?

I googled "the first attosecond after the Big Bang", but didn't get any relevant results. So, I am asking the question here, in hopes of being more successful. What happened during the first ...
user107952's user avatar
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Big Bang as stretching space time?

I am still new to researching the big bang so please be patient. I am having trouble envisioning the expansion. As I understand under current theory it is not to be thought of as a singularity ...
Stargazer's user avatar
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Are all of the characteristics of elementary particles essentially symmetry differences?

I am trying to get a better conceptual grasp on the "splitting" of the fundamental forces at the beginning of the universe. The first force to separate was the gravitational force. Am I ...
blacktopshaman's user avatar
-3 votes
1 answer
91 views

In the Big Bang theory which came first, the vacuum or matter? [closed]

Simply what is our best estimation of what came first in the the first fraction of time of the BB? Was it the vacuum and then matter popped out from violent quantum vacuum fluctuations or matter then ...
Markoul11's user avatar
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0 votes
3 answers
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Determining location of Big bang [duplicate]

I am just a high school student. I had already heard that we can't determine the exact location of big bang. So now i have a question can't we approximate it? Like say divide the observable universe ...
Astrobuuz's user avatar
-4 votes
2 answers
143 views

Suppose the universe from our big bang is surrounded by many distant blackholes with each a mass of sextillions of suns. Could it explain dark energy?

Could dark energy "simply" be from multiple distant universe-scale mass black holes, that are there "all-around" the big bang? Scattered apparently randomly, throughout infinity (...
MGamsby's user avatar
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-2 votes
2 answers
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Since the instant of the big bang, has the progression of the universe been entirely determined?

[Note I am asking up to, but not including, consciousness as this bleeds into philosophy and is a much messier question] Assuming that the laws of physics have remained constant across space & ...
Runeaway3's user avatar
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3 votes
3 answers
212 views

One-Way Speed of Light and the Big Bang

Variations on this question have been asked a few times (e.g. here, here, and a few YouTube videos here and here). The claim seems to be that because we can only measure the round-trip speed of light, ...
user218912's user avatar
1 vote
0 answers
37 views

Understanding the additional field in shape dynamics calculation of big bang

I read this fascinating paper (RG). The total collision is a well-known singularity in Newton mechanics: the distances become zero and, therefore, the potential becomes infinite. In a paper before ...
MartyMcFly's user avatar
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1 answer
107 views

Interaction between energy and spacetime

I hope it's not too stupid but if we say that what we call matter or energy is creating or consuming the spacetime, would not that make the big bang more logical?
omid's user avatar
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Can two $W$ bosons convert a proton into an antiproton by becoming two $W^+$ bosons?

Would this process have been more or less likely in the high energy conditions around the time of the big bang?
user avatar
1 vote
1 answer
191 views

Why does the Matter Anti-Matter imbalance require breaking CP symmetry? Why can't it occur if time symmetry is broken?

I understand the general argument that, without some breaking of symmetry, all the matter in the universe would annihilate all the anti-matter and we'd be left with nothing but photons and some other ...
The Shepard's user avatar
1 vote
1 answer
76 views

Does General Relativity, without Cosmic Inflation, predict a perfect blackbody for the CMB radiation?

My understanding is that the universe did not have enough time to thermalize before the epoch of recombination, so many patches of the sky were not in causal contact with each other, which means they ...
The Shepard's user avatar
1 vote
1 answer
157 views

Why did the Big Bang happen first?

As far as I know, the laws of physics are time-reversal invariant, which means there is no preferred direction of time. The arrow of time emerges with entropy which is a property of macrostates, not ...
John Smith's user avatar
0 votes
2 answers
115 views

Not an "intelligent design" question: How do galaxies collide given the Big Bang? [duplicate]

If all matter began from one infinitesimally small point, and flew outward from there. How can we have galaxies colliding? Did they make left hand turns or something? Or it is possible multiple ...
David Raymer's user avatar

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