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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2answers
812 views

What would be the first compound formed in the early universe?

This may sound like a chemistry problem, but I suspect this would have lot to do with primordial nucleosynthesis. After all physics underlies everything. It is believed that several elements were ...
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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 ...
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Why is there not enough CP violation to account for baryogenesis in the SM?

One of Sakharov conditions states that both C and CP symmetries must be violated by a theory which includes any baryogenesis mechanism. The Standard Model happens to be such a theory, and happens to ...
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646 views

Does second law of thermodynamics imply the big bang?

Given that the second law of thermodynamics states that entropy always increases and the universe is currently not in a state of maximal entropy does that not imply that it must have started at a ...
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2answers
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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 ...
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What would we observe as background on the sky if the big bang had never occurred?

The data we've received so far from satellites such as WMAP paints a near uniform distribution in intensity of the background radiation that we take as evidence that our universe had an origin, and ...
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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 ...
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59 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 ...
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127 views

How to derive number of nucleons in Universe?

I understand that there are roughly $N=10^{79}$ nucleons in the visible Universe. This number comes from adding up the nucleons of $100$ billion stars in $100$ billion galaxies in the visible Universe ...
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Statistical physics in cosmolgy

In https://ned.ipac.caltech.edu/level5/Sept03/Trodden/Trodden4_2.html and also in Mo et al. (Galaxy Formation and Evolution) the number density, energy density and pressure of the different particle ...
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How can I read density fluctuation from microwaves?

The Cosmic Microwave Background Radiation shows temperature differences. The red and yellow areas are warmer. The green and blue areas are cooler. For example consider this picture of CMBR ...
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1answer
139 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 ...
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1answer
141 views

Antimatter/Matter energy release

I am not a physicist, nor do I have a university degree, but I have a question that has been on my mind for some time. If Antimatter and Matter were created equally during the 'Big Bang' would the ...
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1answer
203 views

How to reconcile these two principles?

Quantum mechanics says that the entropy of an unobserved system remains constant. As such, the apparent growth of entropy is a subjective illusion. If we consider the wave function of the universe, ...
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2answers
135 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 ...
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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 ...
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60 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.
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165 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 ...
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1answer
177 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 ...
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130 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 ...
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243 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 ...
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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 ...
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30 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 ...
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1answer
48 views

Could the big bang singularity have been set into motion by a drop in the higgs field?

Could the big bang have been set into motion by a drop in the energy level of the Higgs field?
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How were the particles created from the vacuum state, in the beginning of the universe?

How were the particles created from the vacuum state, in the beginning of the universe? If the particles are created when some energy is supplied to vacuum state, then how were particles created? ...
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1answer
143 views

Hints of pre Big-Bang physics and how to detect them?

The Big Bang model is the current large-scale accepted and tested theory. However, several new physics models or theories propose that there could be a previous Universe. To what extent can be test ...
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451 views

2nd law of thermodynamics in Cyclic Universe Model?

Standard view on Big Bang is that it has started with a perfect point, followed be faster-than-light inflation. This initial perfect point does not seem to agree with CPT symmetry, which is generally ...
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1answer
83 views

How does the scale of homogeneity and isotropy of the universe change as we go back in time?

This question is an upshot of a previous question asked by me. The FRW metric of the Universe is based on homogeneity and isotropy of the universe on a length scale of 100 Mpc or larger. If we go ...
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1answer
60 views

How to reconcile maximum density versus big bang baseball 'material'

I have an incredibly curious 6 yr old who watches Secrets of the Universe constantly and so far I can answer most of his questions but I am struggling on one now. When watching a show about the very ...
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157 views

Where is the missing energy from the Big Bang?

"They" say the Big Bang created 1 billion particles of anti-matter for every 1 billion and 1 particles of normal matter. That the 1 billion particles of anti-matter were annihilated when they met 1 ...
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What process(es) created the initial anisotropies in the energy density distrbution of the universe?

Inflation theory, proposed by Alan Guth, was, in part, an explaination for the observed near-thermodynamic equilibrium of our observable universe. My question is: Why - at the instant of the big-...
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1answer
73 views

Creating two universes at the event horizon of a black hole

Using the uncertainty principle involving time and energy, is it possible a universe and anti-matter universe be formed at the event horizon of a supermassive black-hole? If so, could one the anti-...
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162 views

The steady state theory, can it now be falsified on particle physics grounds, in addition to CMB data?

The steady state theory is no longer taken seriously by most physicists and the Big Bang theory is supported by an enormous amount of evidence, especially the CMB data. But from a quick scan through ...
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Why did the universe have a low entropy at the big bang?

Sean Carroll, in his book "From Eternity to Here", asks the following question. Why did the universe have a low entropy at the big bang? in John Cramer version of the Wheeler - Feynman absorber ...
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1answer
143 views

Is the center of the universe in another dimension?

If we live in a four dimensional world and when we try to find the center of the universe (where the big bang occured) we found that there is no apparent center, could that means that the big bang ...
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468 views

What evidence is there of a universe older than 13.8 billion years

I've read an analogy that finding iron-rich galaxies just 900 years after the Big Bang is like finding an old man in a crib in a nursery. We just recently found a supermassive black hole 12 billion ...
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Is energy since the big-bang still here in the present?

Based on the concept that energy can never be destroyed and is only transferred. Does it mean that energy since the formation of literally everything still here today?
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270 views

Big Bang, Heat Death, and cause and effect

If the Universe has two 'end points', one being the Big Bang, and the other being heat death, is there anything in the laws of physics which forbid a random fluctuation in the heat death state from ...
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According to Penrose, Weyl Tensor=0 is the start/end of the Universe. Must it =0?

If I understand Roger Penrose's theory, as the Universe expands and cools, matter is consumed by black holes. Eventually the black holes collide and evaporate so that there is only energy and the Weyl ...
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Is there any “fundamental” uncertainty to the timing of the Big Bang?

I wondered whether, under the probabilistic interpretations of QM, the timing of the Big Bang (or perhaps any other historical event) is fundamentally as uncertain as (or: like) other (e.g., future) ...
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What is the relation between $X_e$ and $n_e$?

I'm trying to compute the Damping Tail of the CMB. A critical parameter to this calculation is the mean free path of the photons in the plasma:$$\lambda_C=\dot\tau^{-1}$$Where$$\dot\tau=n_e\sigma_Ta$$...
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Why is momentum divergence from energy release not considered in Big Bang models?

From the formation of subatomic particles to the formation of atoms to the nuclear fusion in stars to the explosions of supernovae, the process of conversion of rest-mass energy from fields into ...
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What is the relationship between the Cosmological Constant and the Cosmological Principle?

I believe I've misunderstood a relationship between the cosmological constant and the cosmological principle having read: Einstein introduces his cosmological constant which attributes, in the ...
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1answer
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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?
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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 ...
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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 ...
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1answer
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Is the expansion of the universe really accelerating? Or does it just look like it?

I pulled this quote from an article on the Hubble Constant: "...for example, if the Hubble Constant was determined to be 50 km/s/Mpc, a galaxy at 10 Mpc, would have a redshift corresponding to a ...
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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, ...
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1answer
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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 ...
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Cyclic/Orbiting/Oscillating Universe

Edit: I've changed the title a couple times. I hope this is not an exact duplicate of Big Bounce type questions. Imagine two bodies in a very highly eccentric orbit around each other in their ...