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
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 ...
0
votes
1answer
47 views

Is it possible for another Big Bang event to occur inside our universe?

And if it were, would it constitute an expanding bubble in our universe - with a definite (expanding) surface. That would be nice - none of this irritating "everywhere is the centre and there is no ...
1
vote
1answer
46 views

Do we have enough time for understanding space? [closed]

May be there more big bangs out there... while studding about space i some times think about a bacteria living on my body that may have a life span of 5 seconds if it has logical understating even ...
0
votes
1answer
64 views

Can somebody tell me what was the size of the universe and the expansion rate at the big bang? [duplicate]

I want to know the exact numbers and preferably the calculations that gives the size of the universe at the Big Bang and the initial rate of expansion at the moment of big bang. Does somebody know ...
0
votes
1answer
31 views

What does the matter density in density parameter mean?

When we write $$\Omega_m = \frac{\rho_M}{\rho_{\mathrm{crit,o}}}$$ what density does $\rho_M$ refer to? As in, suppose our universe was made with just hydrogen. Then would $\rho_M$ mean just the ...
0
votes
1answer
77 views

How age of universe or galaxy estimated? [duplicate]

How scientist found age of universe as 13.8 billion years and age of Milky Way as 13.51 Billion years? Is there any proof?
1
vote
3answers
142 views

Why can we see the cosmic microwave background radiation?

This radiation (CMBR) is said to have its origin at the surface of last scattering that exposed itself when the big bang universe had expanded for less than a million years. In order to see radiation ...
3
votes
1answer
60 views

How could the early Universe have low entropy when it was so compact? [duplicate]

Entropy of a system can be understood as "the number of states that are macroscopically indistinguishable from the state its currently in". (Sean Carroll, "The Big Picture") Given that the early ...
0
votes
1answer
90 views

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 ...
2
votes
3answers
139 views

If information is conserved, why did the early universe had lower entropy than now? [duplicate]

If information and entropy are equivalent, and information is a conserved quantity because of unitarity, what does it mean to say that entropy is growing since the big bang (I know why it grows, I'm ...
-1
votes
2answers
81 views

How do we know the age of Cosmic microwave background? [duplicate]

How do scientists know the age of the CMB? And how does it correlate to the age of universe?
0
votes
0answers
18 views

How can we be sure if Universe has exploded with big bang? Can't it be implosion? [duplicate]

Why do we say the universe has exploded in the event of big bang? When we talk about big bang there was no concept of outside with the absence of space, so should’t the universe be imploded into the ...
0
votes
3answers
109 views

Does the Cosmic microwave background also lies in radio frequency spectrum?

I heard the CMB is the electromagnetic radiation from the big bang. It is 13.7 b years old but isnt it only in the microwave range of the spectrum (300MHz - 300GHz) . Can a FM radio receiver (87-...
0
votes
0answers
29 views

How can the universe expand faster than the speed of light? [duplicate]

In Neil deGrasse Tyson's Astrophysics for People in a Hurry, he writes: By now, one second of time has passed. * The universe has grown to a few light-years across... If nothing can move ...
1
vote
0answers
45 views

If Time and Space are intrinsically linked and space is ever expanding then surely time is slowing down [duplicate]

When we try to imagine the initial expansion after the big bang we see with the CMB that the universe went from initially smaller than a hydrogen atom to what we see today. However, when we try to ...
-1
votes
1answer
38 views

Seeing the Big Bang [duplicate]

The Big Bang happened almost 14 Billion years ago. Theoretically speaking , if we could teleport (Instant teleportation) to somewhere that’s 20 Billion light years away from the Earth , if we looked ...
4
votes
2answers
79 views

What caused neutrinos to decouple at $t=1$ second?

Was it simply that the density and/or kinetic energy got too low, because of expansion? Or was it something about the weak force itself (which I thought gelled around $10^{-10}$s? For the CMB, ...
1
vote
1answer
108 views

Big Crunch vs Big Rip vs Heat Death vs Conformal Cyclic Cosmology… What's the Most Common View? [closed]

I just saw that Penrose recently published a paper on Conformal Cyclic Cosmology and it made me wonder, what exactly is the consensus view these days? I first heard of Penrose in connection with Orch-...
0
votes
2answers
59 views

Mass and Expanding Space

1) space is expanding at an increasing rate, therefore things are getting farther from each other and therefore increasing in velocity. 2) the faster an object moves relative to another, the more ...
1
vote
2answers
90 views

Does Big Bang predict the size of the fluctuations in the CMB? [duplicate]

From this Ethan Siegel’s article The temperature fluctuations in the CMB are only 1-part-in-30,000, thousands of times smaller than a singular Big Bang predicts. Does big bang predict the size ...
4
votes
2answers
161 views

Was the universe already expanding before inflation occured?

Was the universe already expanding before inflation occured or did inflation cause the universe to start off expanding? By “cause it to start off expanding” , I mean the cause of the initial ...
0
votes
1answer
82 views

Would eternal inflation be really eternal since quantum fluctuations are usually very rare and very small?

I’ve read somewhere that quantum fluctuations in the inflaton field are usually very rare and very small. If the effect of quantum fluctuations pushing the potential uphill is too rare and too small ...
2
votes
1answer
128 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 ...
1
vote
1answer
137 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 ...
0
votes
2answers
81 views

Does object from which the universe is created still exist in its original form? [closed]

If time is passing more slowly near objects with bigger gravitational mass, could it be that the time at the object from which the universe is created has not started yet (or very little of time has ...
2
votes
2answers
121 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 ...
1
vote
2answers
61 views

In what sense the scale factor $a(t)\to 0$ lead to the big bang singularity?

How do we understand that the limit $a(t)\to 0$ (where $a(t)$ is the scale factor) lead to a spacetime singularity? Is it by substituting $a(t)$ in the FRW metric and concluding that space makes no ...
1
vote
0answers
104 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 ...
0
votes
1answer
41 views

The surface of the last scattering and pictures of deep field

Maybe this question (in fact I have a few of them) is naive but nevertheless, let me try to ask it: it is concerning the furthest regions of our universe. Is the Hubble telescope capable to ...
2
votes
1answer
73 views

How is the primordial abundance of Lithium measured?

I was reading about the "Lithium problem" and I came across this Physics SE post: Discrepancy problem in lithium? The answer mentioned On the other hand, measurements of the $\rm Li$ abundance ...
0
votes
1answer
143 views

Alexander Vilenkin - The Universe probably had a beginning [duplicate]

Is it true that the Universe can not have an eternal past? It seems like Alexander Vilenkin tries to argue this? Does this imply that the Universe had a beginning? Link to his publication regarding ...
5
votes
1answer
100 views

How far back in cosmology is there observational evidence?

It seems "the first three minutes" are well established... back to the first second? 10 seconds? What about the "hadron epoch" going back to the first microsecond? Or before that? I know there are ...
0
votes
1answer
104 views

Could matter in the universe come from some process other than the decay of inflaton field?

Could matter in the universe come from some process other than the decay of inflaton field? Do we have any theoretical reasons that support the idea that matter was created from the decay of ...
0
votes
1answer
112 views

Did negative pressure cause the universe to start off expanding at the big bang?

What caused the universe to start off expanding in the first place. Was it negative pressure that drove the initial expansion or was it just something else?
1
vote
1answer
140 views

Why do we think that the energy density of false vacuum/scalar field doesn’t dilute with the expansion?

I have a question about inflation theory. Why do we think that the energy density of false vacuum/scalar field doesn’t dilute with the expansion? Could it be that the energy density does dilute with ...
3
votes
3answers
111 views

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 ...
1
vote
1answer
89 views
-1
votes
2answers
338 views

Apparent contradiction between First and Second Laws of Thermodynamics

How is the Second Law of Thermodynamics not either false or incompatible with the First Law of Thermodynamics? In practice, the Second Law entails that, given an infinite amount of time, there should ...
0
votes
0answers
18 views

Was the big bang a black hole that collapsed [duplicate]

I know this might be a silly question and maybe a bit off topic, but I wonder, could the big bang have been the collapse of a gigantic black hole in which all off its contents was pushed out? I have ...
2
votes
0answers
51 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 ...
0
votes
0answers
32 views

The location of Big Bang [duplicate]

Every lecture I've attended, book I've read, or TV show watched explains that the universe was once no larger than the Milky Way, or the solar system, wait, it was so small that it could fit in a ...
3
votes
2answers
76 views

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 ...
0
votes
0answers
36 views

During big bang, everything expands same rate, homogenous, isotropic, nothing pulled towards each other. Did quantum randomness form stars, galaxies? [duplicate]

During big bang, space expands separating everything at the same rate, homogenous and isotropic, nothing is pulled towards each others. Did quantum randomness form stars and galaxies? If there is no ...
1
vote
1answer
67 views

Would the universe be significantly different if neutrinos were massless?

As far as I know, neutrino oscillation experiments have fairly conclusively demonstrated that neutrino states have mass. However, neutrinos are so frequently taken to be massless in cosmology that I ...
1
vote
0answers
73 views

How far are we from the “edge” of the universe? [duplicate]

According the the Big Bang theory, the universe started as a 0-dimensional point of infinite density. Shortly thereafter, it underwent inflation and grew to some measurable size, and continues growing ...
1
vote
1answer
58 views

Temperature after the big bang

I was just wondering about possible extreme temperatures. It came to my mind that shortly after the supposed big bang the universe was probably at its hottest in its entire Lifetime. But does it even ...
-2
votes
1answer
81 views

How to explain curvature of spacetime at the time of big bang [duplicate]

According to Einstein mass causes curvature of spacetime ,so he basically defined mass using space i.e (mass is something which causes curvature of spacetime).Now at the time of bigbang there was no ...
3
votes
2answers
123 views

Why did CMB decouple when neutral atoms formed?

Atoms can absorb and emit photons. But it is said that when the neutral atoms were first formed the photons got decoupled. If the atom-photon interaction is allowed how can we say that photons were ...
1
vote
1answer
72 views

Does the big bang model describe a first momment in time for the entire universe or just the observable universe

The big bang model describes the universe as contracting as we wind time backwards. Since the observable universe is of a finite size this ultimately sets the first moment of time at around 13.8 ...
2
votes
2answers
79 views

Can we have bubbles of the tenth dimension in our universe?

If the gap between the branes in the Big Bounce theory is the 10th dimension, and branes have wrinkles as they collide, can our universe have 'bubbles' in the 10th dimension? This is in reference to ...