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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What implications to cosmology would it have if Webb Telescope probing the far end of our observable Universe finds out a large number of galaxies?

Since it is predicted that Cosmos is no less than 250 times that of the observable Universe (13.8 Blyrs) in size: MIT Technology Review I wondering how you can calculate any age of matter creation (...
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How does it make sense for the universe to have started from a big bang?

It has been said that the Big Bang started from a singularity. Think about a balloon radially growing over time. Fix a time $t_0, t_1 > 0$, and let $M_0, M_1$ be two balloons at time $t_0, t_1$ ...
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How is the Big Bang compatible with the preservation of quantum information?

As detailed at https://en.wikipedia.org/wiki/No-hiding_theorem , in the quantum world, information cannot be created or destroyed. The Bekenstein bound limits the amount of information that can be ...
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What is there at a point the universe hasn't expanded past yet? [duplicate]

(Please don't mark as a duplicate) If the universe is constantly expanding that means that there is a point the univese hasn't expanded past, with that what would be past that point? This isn't about ...
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What is at the edge of space? [duplicate]

if the universe is constantly expanding that means that there is an end where the universe hasn't expanded yet if you could be at that before it was to expand more, or go past/into that edge, what ...
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How can the universe be hot or dense in the first moments after the big bang when it has no matter?

From the CERN website: In the first moments after the Big Bang, the universe was extremely hot and dense. I've always heard this about the big bang but I've never thought about it before now. If &...
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Do the apparent infinities at the center of black holes disappear if instead a phase-change takes the place of its singularity?

When I watch physics documentaries that discuss black holes, they talk of impossible infinities in the singularity at a black hole's centre. I was wondering about the bubbles of water vapour in ...
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Deriving the age of the universe

I am trying to work out the solution to exercise 8.4 from An Introduction to Modern Cosmology by Andrew Liddle. I could derive the Friedmann equation as below, $$\dot{a}^2 = H_0^2 \left[\Omega_0a^{-1} ...
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Based on structure formation and the lifetime of the universe why is there an upper bound on the cosmological constant?

I understand that significantly greater values than the cosmological constant would result in difficulty for the formation of large gravitationally bound structures within the lifetime of the universe....
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Why did the quark epoch occur earlier than the lepton epoch?

I don't understand the reason and hypothesis behind why the quarks appeared first—as per the big bang cosmology—shortly after the strong and electroweak force separated. We don't know what the quarks ...
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${}$Hawking radiation and Einstein-Cartan theory

As I understand it, Einstein-Cartan theory predicts that inside every black hole, there is an einstein rosenbridge connecting to a new universe that forms due to a white hole. Where does hawking ...
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Does photon-photon scattering influence classical vacuum E&M dynamics?

At a purely classical level, Maxwell's equations are completely linear, and associated with a linear coupling to a conserved current in the electrodynamical Lagrangian. When this Lagrangian is ...
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Why is the age of the universe $=D/v$, despite that $v$ is not constant with time?

I am watching a series of lectures by the Noble prize laureate Brian Schmidt and Paul Francis and in this episode (at 4:20) they make the simple assumption that a galaxy receding from us due to the ...
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What if cosmological inflation never stopped?

If inflantionary theory is correct, the universe ceased to expand after just $10^{−32}$ seconds. Imagine a scenario where cosmic inflation never actually stopped. At the extremely accelerated ...
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Are there any Big Bounce models where the laws of physics (even the most fundamental ones) would change between cycles?

Big Crunch-Big Bang models (usually called Big Bounce models or cosmological oscillatory models) are highly unlikely to happen due to the discovery of the accelerated expansion of the universe. But ...
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What does it mean that gravitation separated from the four forces at $10^{-36}$ seconds?

Physicists have used math to calculate that gravitation separated from the 4 forces at 10^-36 seconds after the big bang, which is even before the inflationary period. The universe was still smaller ...
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Trying (and failing) to calculate baryon/photon ratio

I'm reading through Modern Cosmology by Dodelson and Schmidt 2nd edition on my own, and at the start of Section 4.2 the book says that we can compute the baryon/photon ratio at the time of big bang ...
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Can the age of the universe be much bigger than 13.8 billion

If observable universe is only a small fraction of the existing universe, does it imply that the age of the universe is much more than 13.8 billion years or the expansion of the universe is much ...
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Assuming that heat death or Big Freeze would be the final outcome for the universe, what would happen with energy?

According to Big Freeze, the universe will expand forever and it will reach a state of thermodynamical equilibrium. It is said that the temperature of the universe will reach an asymptotically ...
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The big bang conditions involve a low entropy state—Is this really true? [duplicate]

The CMB and large-scale structure observations show that our universe was very homogenous in the past. This leads to the horizon problem, and there are two ways of getting around it. One way is to ...
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Does whether or not inflation occurred change the estimated age of the universe?

When we say "age of the universe," I assume this means the time interval for the Euclidean FLRW metric $$ ds^{2} = -dt^{2} + a^{2}(t)\Big(dx^{2}+dy^{2}+dz^{2}\Big) $$ from when the scale ...
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Ratio of specific entropy after a particle decay

I am working through the following problem (not homework, but revision), and would appreciate some feedback on my answers to parts (b) and (c). For part (b), I used Friedmann's first equation ...
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What is the furthest thing we can see at the time the light was emitted?

To be more precise, let $P$ denote the position where the Earth is at the time this post is submitted. Assume our coordinate system is such that this point is fixed in space and the rest of the ...
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Given lots of time and space, could $10^{80}$ virtual particles become real particles at the exact same time and place? Could that cause a Big Bang?

Given lots of time and space, could $10^{80}$ virtual particles become real particles at the exact same time and place? Could that cause a Big Bang?
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Dark energys energy density value

What mathematical property does dark energy have that causes the effect of an expansion? I have read that the energy density of dark energy is time invariant, which is the main cause of an accelerated ...
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Could our universe still work if either one of $c$, $h$, $q$, $G$, permeativity, permeability or $H_o$ were slightly different? [closed]

Could our universe still work if either one of c, h, G, q, permeativity, permeability or Ho were slightly different? Also all of them are thought of as being constants for the whole history of the ...
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Why is gravity believed to have been as strong as the other fundamental forces at the beginning of the universe?

Why is gravity believed to have been as strong as the other fundamental forces at the beginning of the universe and what should be the cause of that possibility?
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What is the reason for density fluctuations in the primary matter of the early Universe? [duplicate]

After a period of inflation and nucleosynthesis, small density fluctuations appeared in the primary gas, which became the "seeds" of the first stars and galaxies. What led to the appearance ...
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The location of the exact center of the observable universe

If simultaneously in every direction, I were to precisely measure the distance to the edge of the observable universe (not: the physical universe), then would I find myself exactly in the center with ...
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Expansion speed of the universe in the interval between Big-Bang until first galaxies, and in the interval between first galaxies and 'now'

If the redshift or elongation of microwave background radiation is about 1000 times and the redshift of light of the most distant galaxies which are the oldest ones in our Universe is only about 10 ...
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Does this paper show that the universe could have come from nothing?

The beginning of the universe is exciting and as Ive read about it I’ve come across a paper that talks about quantum mechanics and how quantum fluctuations can cause space to be created from a meta ...
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How is the expansion of the universe measured if redshift depends on the expansion itself? [duplicate]

To me this seems like a bit of a chicken egg problem. Based on the redshift of light (plus the assumption that physics worked the same way back then and there as it does now and here), we can ...
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1 vote
2 answers
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Can dark energy dominate from the Big-Bang?

I'm studying the age of the universe for a universe dark energy dominated. Using Friedmann equation $$ \left( \frac{\dot{a}}{a} \right)^2 = H_0^2 \left[ \Omega_R \cdot a^{-4} + \Omega_{NR} \cdot a^{-3}...
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Age of the universe and time dialation [duplicate]

We currently believe the age of the universe is 13.8 billion years old. However because time is relative, what is this age relative to? As for e.g Light 0 seconds has elapsed.
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Is the inflation rate of the universe uniform throughout?

Is inflation constant at any given moment throughout the entire observable universe? I realize inflation was once much more prevalent, so at the edge of the observable universe, we would observe a ...
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How can we extrapolate gravitational waves in the early universe from CMBR?

I know it has to do with polarization of CMBR, but not sure how gravitational wave polarized early light.
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How was the Big Bang possible if it was so dense even light cannot escape? [duplicate]

Since the big bang comprises of all the particles in the universe in an extremely dense point, couldn't it to be said it would be the most massive black hole to ever exist? Since even light cannot ...
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Actual physicists: shoot down my hypothesis regarding antimatter, primordial black holes, and the origin of the universe [closed]

Let's get this out of the way up front: I'm no physicist and have no business proposing any of the things I'm about to propose. The likely outcome here is that someone with relevant education can ...
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Was the Big Bang an isolated event in an otherwise empty universe? [duplicate]

I have been told that the big bang happened everywhere at once. This I think implies that the entire universe at large looks like our observable universe, starts galaxies and such. But do we know that ...
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Can there be a start of the universe? [duplicate]

I remembered learning about the essential law of conservation of mass, stating that no mass/matter can be made or destroyed. That got me thinking, if no matter can be made or destroyed, then there can'...
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Does time flows differently now compared to moments after big bang?

Has time been flowing at a steady pace ever since big bang or it was very different compared to the early universe say before photon epoch? I suspect time ticks at the same rate throughout the ...
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What is the origin of the Universe's primary density perturbations?

We get the following picture of the formation of inhomogeneities: initially the fields (which has now decayed into well known fields of Standard model) lived in a vacuum state -- there were no real ...
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How can we show that the very early universe can be considered to be flat?

Let me confess that it's a homework problem. I was working on a heuristic proof of the following problem. How can we prove that the very early universe can be considered to be flat. It was asked in ...
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When we say that the universe is expanding, what is causing this?

I could understand an initial explosion imparting momentum to matter but where is the energy stored in space itself? How does empty space have momentum that causes this expansion?
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Big Bang and relativity [duplicate]

Wasn't the big bang's explosion itself faster than speed of light? how does this not violate relativity, I had read an explanation earlier but it wasn't sufficient, can someone explain to me how the ...
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4 votes
3 answers
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Where did the CMB come from? What is due to the matter/antimatter annihilation? Or perhaps the radiation released when the electrons decoupled?

Where did the CMB originate from? I get that at the beginning of the universe, by the Big Bang theory temperatures and pressures were too high for matter to exist, and even if it did, it would just ...
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6 votes
4 answers
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Did the universe need the presence of matter and radiation to start expanding?

I have read this question: Hence it is not possible that photons generated by stars is contributing to dark energy. Could photons generated from the many trillions of stars be some how contributing ...
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2 votes
1 answer
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Is cosmic background radiation consistent with the Cosmological Principle? [duplicate]

Is the observation of cosmic background radiation really consistent with the cosmological principle? It implies that there is a "special" rest frame of motion with respect to the big bang. ...
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Is the age and expansion of the universe the same from all perspectives? [duplicate]

If I understand the Cosmological Principle correctly the age and rate of expansion of the universe must be the same from all frames of reference, yet is this consistent with relativity that states ...
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-2 votes
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If the sky is full of microwave radiations then why don't we see it?

So basically we know that the sky is full of microwave radiations but why can't we see it if so ?
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