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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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Can someone explain this paragraph on inflation in Stephen Hawking's lecture?

In this lecture, Stephen Hawking writes According to the no boundary proposal, the universe would have expanded in a smooth way from a single point. As it expanded, it would have borrowed ...
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1answer
135 views

Can collapsing of the first star cause a staggering chain reaction throughout the universe?

Forgive me but I am not an academic but I have an enormous curiosity and am more or less teaching myself. I stumbled upon this site totally by accident and have relished the information here - ...
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923 views

What is the source of energy of the universe?

For example, our human body obtains the energy for work by food, water etc for the nutrition, the plants require water, fertilizer for nutrition to produce food, machines require fuel to work, may it ...
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261 views

Why does the big bang not violate Heisenberg's uncertainty principle? [closed]

I have been doing some reading about the start of the universe and some sources would state that the universe started as a singularity. But how does this not clash with the uncertainty principle?
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Since gluon fields do not appear apart from quarks, did gluon fields first appear during the quark epoch?

Big Bang cosmology and grand unification theories say that the strong force and the electroweak force separated during the electroweak epoch, i.e., $10^{-36}$ to $10^{-32}$ seconds after the Planck ...
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1answer
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Meaning of “time” related to existence of the universe [duplicate]

A question, that bugs me since a long time already, are sentences like "in the first second after the big bang". The problem that I have, is that time measurements would need an observer, which in ...
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110 views

Which came first: leptons or baryons?

If you had a big collection of neutrons, they could decay into protons, electrons, and neutrinos through beta decay since protons are the only stable baryons. After a while, you should get hydrogen ...
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How is the CMB used to determine the age of the universe? [duplicate]

Bear with me if this question sounds dumb, I don't understand relativistic redshift and general relativity very well. To imagine it, I picture the universe as being on the surface of an expanding ...
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279 views

If the CMB was emitted at the ionization energy of hydrogen, why is it a blackbody spectrum instead of a line spectrum?

Context From what I understand about the Cosmic Microwave Background Radiation is that it was from the big bang, and since space has streched and become bigger since then the wavelength of the CMBR ...
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Is big bang theory is correct? If is it true then how can possible to store trillions of atom in a single point? [duplicate]

Can you give me the proof of big bang theory? If is it true then how can possible to store trillions of atom in a single point? Why and how it's explode
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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 is the universe infinte if it started with the Big Bang? [duplicate]

Big Bang is portrayed as the expansion of an infinitely-dense singularity. How does this work with the possibility of the universe being flat and therefore infinite? That could only work if the ...
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Hubble's Constant Calculation [closed]

I am solving a question about Hubble's constant. One estimate of the age of the universe is $13.7 \times10^9$ years. Calculate the Hubble constant in $km s^{-1}Mpc^{-1}$ Approximate that 1 year = $...
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When did matter/energy come into existence? Before or after the CMB?

First of all thank you to anyone who replies this question, I am not a physics major, but foolishly chose to take a physics for non-science majors at my local university I am going to. I am trying ...
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1answer
924 views

Can quantum vacuum exist without space and time?

The title won't do justice with what i want to ask so let me put forth scenario. I studied and i have researched that it is a established and well supported theory that space and time did not exist ...
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99 views

What is meant by “spontaneous creation” in this paper?

https://arxiv.org/abs/1404.1207 I have some questions in regard to this paper. If I am not mistaken it is akin to Alexander Vilenkin's proposed cosmological model that has the Universe begin to exist ...
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Where did the Big Bang happen? [duplicate]

Does the Big Bang theory directly imply that there is a much larger structure in which our universe is embedded? If this is not true then where did the Big Bang happen? Where did the material before ...
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When did the first black holes form?

How long after the big bang did the first black holes form? How can we determine the answer to this question?
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51 views

How did the Big Bang cause the cosmos to be infinitely large? [duplicate]

If the cosmos is product of the big-bang as we think then it would seem there is a problem with the probability of it's supposed infinity (as it was initially finite). In addition, the rate of it's ...
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522 views

How can time be finite and without boundaries?

Stephen Hawking wrote about the "the possibility that space-time is finite but had no boundary" (A Brief History of Time, 2011, p.120), and that "when one combines general relativity with the ...
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1answer
94 views

What information do we have about time before the big bang?

I've heard for awhile now that a lot of physicists think that time was created in the big bang as a dimension (just like space). When I try to look this up online though i just get on old lecture from ...
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4answers
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When did the Universe turn from a quantum system to a multi-particle system?

Background: The properties of quantum particles and fundamental fields are the same all across the Universe. Each particle of a certain kind is identical to all other particles of that kind ("a ...
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3answers
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Why is Hubble's constant exactly the inverse of the age of the universe?

Why is Hubble's Constant exactly the inverse of the age of the universe? This cannot be coincidence. If according to our laws of physics this is coincidence then surely we have got something worked ...
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Why do singularities either lie completely in the future or completely in the past?

In his book "A Brief History of Time", Prof. Hawking goes on to state that singularities either lie completely in the future or in the past. What does that mean in layman terms and why does it so ...
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Do galaxies have a halo of neutrinos and cosmic microwave background?

If virial arguments as in "How can dark matter collapse without collisions or radiation?" allow concluding that dark matter could collapse to galactic halos purely gravitationally, then is this true ...
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Gravitational Waves from the beginning of time

I just heard a physicist say "[an] exciting discovery would be to find gravitational waves from the beginning of time." Since gravity travels at the speed of light, wouldn't gravitational waves ...
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1answer
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Space-time infinite [duplicate]

My apologies if this is a duplicate question. I could not find it. Why do we think space-time itself started at the BB? Or to word it another way, could space-time have always existed infinitely in ...
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1answer
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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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198 views

After the big bang

So much time has passed after big bang. We say that when we look at the night sky we see past.so when will the light from big bang showing how was it back then come to us and, show us how it existed.
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Where would you get the most time, compared to everything else? [closed]

If from a photons perspective it doesn’t experience time and travels zero distance in zero time, and from anything else’s perspective light clearly travels and it takes time to do so, could there be ...
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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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Evidence before CMB

I have been looking online and in other resources for some answers to no avail. Thought I would sign up on astrophysics forums to find the answer. What is the evidence and data for the period before ...
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3answers
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If free quarks can't exist, how did the universe form?

As I understand, the Big Bang started with a photon gas that then created the other particles. Thus obviously there would be some free quarks in the early Universe unless quarks are always created in ...
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Was there a first moment in time?

Disclaimer. I am a mathematician, not a physicist. The extent of my physics training is a couple of high school courses. So, you may have to be very patient with me in understanding your answer(s)/...
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Encoding information in the CMB [closed]

Given that a civilization had the capability (Kardashev type IV?), and supposing Ω > 1, would it be possible to adjust the universe in a way that would effectively encode information in the CMB before ...
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2answers
482 views

Why isn't the universe uniform? [duplicate]

I always have a question in my mind when I think about the big bang. It is that if the universe has expanded from a tiny singularity by an explosion to the universe of today, why didn't it expand into ...
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2answers
574 views

Does the existence of matter and energy in the universe violate the second law of thermodynamics?

The second law of thermodynamics is often cited as the reason that "free energy" is not possible. That we cannot get more energy out of a system than we put in. It is my understanding that the ...
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1answer
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How is the age of the universe theorized? [duplicate]

There are statements in wiki like: The current measurement of the age of the universe is 13.799±0.021 billion (109) years within the Lambda-CDM concordance model. My question is how does ...
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1answer
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Jim's Simple Physics Issue #i: The Big Bang Theory and Inflation

this is Jim again with another of my Simple Physics installments. This time I want to cover the much misunderstood concepts of the Big Bang theory and cosmological inflation. Like many of my other ...
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What does one second after big bang mean?

Consider the following statement: Hadron Epoch, from $10^{–6}$ seconds to $1$ second: The temperature of the universe cools to about a trillion degrees, cool enough to allow quarks to combine ...
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Black Holes collapsing [duplicate]

If a black hole collapses on itself, then could the energy and matter that causes from the implosion/explosion, could a new universe/galaxy be born from that?
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1answer
191 views

Was the big bang singularity rotating?

See, I was thinking that every atom has electrons rotating around the nucleus and there are huge number of atoms in the universe, according to law of conservation of angular momentum, it remains ...
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41 views

Before the Beginning [duplicate]

At some point the material universe(s) began. At some point Big Bang(s) apparently took place. IOW, we are here: "I think therefore I am." But how did "all this" begin, whenever that may have been? ...
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95 views

How do we understand time & size in the earliest moments of the universe?

1) I don't know whether this question should belong to this site: please correct me if not. In the earliest moments of the universe history probably all fundamental forces where indistinguishable: in ...
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1answer
157 views

Black hole thought experiment

We have two super-massive black holes with the same mass rotating around their center of mass. Now, lets put something very dense at the center of mass. It has to be that it's radius is the ...
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2answers
85 views

Will all mass eventually decay, ending space-time but starting a new-space-time?

I seem to recall learning from a TV programme (so there may be problems with this already!) that the 2nd law of thermodynamics provides that everything in the universe will at some point decay into ...
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2answers
105 views

Was the Big Bang denser and hotter than a black hole?

I know that the Big Bang theory states that the early Universe had a very high temperature and was extremely dense (thus causing a gravitational/space-time collapse) but if that's the case then wouldn'...
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2answers
255 views

Big-Bang and third law of thermodynamics

From third law of thermodynamics, if temperature T➡0, the entropy S➡0. In another way we can also say that with the rise of temperature, the entropy will rise. But we also know that our universe at ...
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119 views

Why is the universe expanding yet remaining flat?

According to The Big Bang Theory everything started from nothing and suddenly started expanding creating everything that is. So why is it only expanding on an X&Y axis? I can only find facts that ...
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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-...