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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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 ...
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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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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?...
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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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96 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 ...
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81 views

Understanding time [duplicate]

Am sorry if this is a silly question. I have heard something like this from cosmologists: "There is no intrinsic arrow of time. Today, we believe that the direction of this arrow is due to our ...
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1answer
293 views

If the Big Bang theory is true, what caused it to explode?

According to the Big Bang theory, all the matter in the universe was amassed together at one single point. If this was the case, why was it able to explode? The density of the mass would create a ...
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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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61 views

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 ...
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1answer
46 views

Does energy to matter+antimatter conversion increase the amount of information?

If I am not mistaken; when matter and antimatter annihilate each other and release energy, all the information except the total amount of mass, becomes lost. So, can we say that the reversed process ...
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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
225 views

Isn't the Big Bang contradictory with the existance of singularities in black holes? [duplicate]

So it's my understanding that the current models predict that a super massive object will collapse beyond the event horizon into a singularity of infinite density. My question is the following: isn't ...
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2answers
1k views

If energy cannot be created, how did the universe come into existence? [duplicate]

The first law of thermodynamics states that energy cannot be created. If that's the case, how did the universe come into existence? I mean, doesn't that require energy to be created? Excuse my ...
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1answer
103 views

Quantum Tunneling

Does Quantum tunneling prove there is a chance of big bang after the heat death of the universe? I mean how can we say it can produce another Big Bang in some years.
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1answer
170 views

Big bang singularity in an infinite universe [duplicate]

If the spacetime of the universe is infinite now, then it must have been infinite at every point in its history, right? How then can Big Bang be an expansion of space and time? Can somebody show the ...
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1answer
537 views

Why does the temperature of the early Universe decrease as it expands? [duplicate]

According to the Big Bang theory, the universe cooled down as it expanded. I would like to know why does the temperature decrease? And by "why" I mean how. What causes the temperature to decrease, ...
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301 views

The “Big Rip” -vs- Color confinement [closed]

One model for the end of the Universe says that space will continue to expand faster and faster, until even atoms are ripped apart in the so called big Rip. It is also stated by QCD (quantum ...
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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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1answer
114 views

If space is expanding does the Plank unit also expend?

There are three elements which I find their connection a bit confusing regarding the expanding universe. 1. The growing distance between the matter in the universe. 2. The actually expansion of space ...
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How did temperature exist at the moment of Big Bang? [duplicate]

As we know at the moment of big bang ($10^{-43}$ seconds or Planck time) the temperature was $10^{32}~\rm K$. I hope for temperature to exist there should be some medium or matter needed. Is it ...
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1answer
73 views

At what temperatures did various atomic and subatomic particles begin to form?

I've been simulating the expansion of the universe using the Friedmann Equation and some numerical integration in python. I've been able to calculate the temperature of the universe by dividing the ...
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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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3answers
209 views

Could Dark Matter/Energy be explained by a second universe? [closed]

Is it possible that prior to our current universe's Big Bang, there was a universe made up of Dark Matter/Energy created from a prior Big Bang? Its physics/matter could have been different than what ...
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1answer
641 views

What are the problems or shortcomings of the Big bang theory? [closed]

I know Big Bang is the most accepted model among scientists today and has been for several decades but I am just curious to see if it has any flaws as well. So what are its flaws? And what are the ...
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59 views

Who's Time Is It Anyway? [duplicate]

13.7 billion years ago, the universe suddenly had a low enough energy density that we could understand it, and we call this the big bang. However, we are in the thrall of several gravity fields. The ...
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1answer
88 views

Is the observable universe analogous to a white hole?

My instinct is no, but my lack of understanding with respects to white holes doesn't tell me why. My thinking is this: The universe is expanding and the further away from us the faster it is expanding....
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1answer
81 views

Why does the lack of antimatter in the observable universe suggest a baryon asymmetry?

My title question relies on the answer to this question: Under the standard model and assuming baryon symmetry, is it possible (however unlikely) that some small local pocket of the universe might ...
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1answer
129 views

Were the 1st generation stars low or high-mass stars?

I have been taught that the first stars to be "born" could not use the CNO cycle to fuse Hydrogen into Helium as there were no elements heavier than Helium and a bit of Lithium to use in those ...
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202 views

How do we know that universe is flat?

Last measures by WMAP indicates that the universe is flat with a 0.04 margin of error. What does that exactly mean? Is it almost flat but with a soft curvature that could be negative or positive?
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1answer
84 views

What is so natural and inevitable about the expansion of the universe?

The opening paragraph of the section the Introduction to Standard Big-Bang Model in the PDG review claims that The observed expansion of the Universe is a natural (almost inevitable) result of any ...
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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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1answer
386 views

Formula used to calculate the speed of a receding galaxy

I am trying to explain why the Hubble redshift-distance diagram can't be interpreted as evidence for a large explosion having taken place a long time ago in a static universe, sending all galaxies in ...
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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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120 views

After the Big Bang Planck time [duplicate]

What happened before the Planck time in the big bang? I have seen a timeline for after the big bang but there is no description of what happened before the Planck time.
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683 views

What was the size of universe at big bang [duplicate]

While self studying cosmology as well as reading around I can't find a satisfactory answer to this question. My thinking is that in principle universe could have started already infinite or as a thiny ...
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56 views

Was there a point in the past when the density of the universe was infinite?

I would just like to put it out there that I do believe that the Big Bang was a cosmic occurance. However, I have been asked to argue the fact that there was a point in the past when the density of ...
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1answer
342 views

How can an infinite universe be dense at the big bang? [closed]

If the universe is infinite, it always had to be spatially infinite since at the big bang. And I'm assuming that cosmologists don't think that a Big Bang singularity actually occur in the real ...
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1answer
52 views

Can gradual expansion in the early universe instead of inflation creates a flat universe?

Can gradual expansion creates a smooth, uniform, and flat universe. Is it possible that the early universe was a gradual expansion instead of a very rapid and short expansion (inflation)?
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450 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
121 views

Big Bang or Big Suck?

Mathematically, is there any difference between a colossal inner force pushing out the singularity and continuing to expansion, and a colossal outside gravity pulling out the singularity and ...
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The growing expansion speed of our universe [duplicate]

Is there a definitive way to calculate the speed at which the expansion of our universe is growing? To clarify i don't want to know the speed. I want to know if there is a way to calculate the ...
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1answer
73 views

Geometry of Big Bang

As you look at circle cross-sections around a sphere it's obvious that as you move the circles along the z-axis, the circles get bigger and smaller. When you're at the farthest points on the $z$-axis, ...
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Must the origin of the universe be non-physical? [duplicate]

Since the 2nd law of thermodynamics says the universe's entropy is constantly increasing, then its initial entropy must have been smaller than it is today. However, no known physical law can reduce ...
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1answer
56 views

Assumption in Lambda CDM model

I just read that the Lambda CDM model assumes that General Relativity holds on a cosmological scale. Could someone please explain to me why that assumption would be needed? General relativity is the ...
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1answer
36 views

What is a Coulomb suppressed reaction?

I have specifically been reading the in context of Big Bang Nucleosynthesis however, I feel the concept is more general. I could not find a definition online, I am just not sure what it means. Many ...
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1answer
608 views

What was (physically) present within the mass of initial singularity?

I've been trying to figure out what scientists believe to have been infinitely condensed in initial singularity. It is claimed that all mass existed before the big bang, this leads me to many ...
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2answers
873 views

Age of the CMB: How do we know?

As short as possible: From what I understand the Cosmic Microwave Background was predicted by multiple people as a theoretical consequence of the Big Bang theory, and hence today, is evidence for the ...
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0answers
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If a magnet were hypothetically traveling faster than the speed of light, then how would that affect its magnetic field? [closed]

If a magnet were somehow traveling faster than the speed of light through perhaps starting with that initial velocity during the big bang or perhaps a alcubierre drive then how would this effect the ...
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1answer
82 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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In the singularity prior to the big bang where time doesn't exist, if something is possible (making a big bang) will it eventually happen? [duplicate]

If there was no time prior to the big bang and it was possible that it expanded and created the universe (and it happened) then, despite time doesn't exist there, if something is possible it will ...