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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How does inflation relate to spontaneous matter creation?
According to Inflation for Beginners,
... quantum physics allows the entire Universe to appear, in this supercompact form, out of nothing at all, as a cosmic free lunch. The idea that the Universe ...
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Could false vacuums potentially describe, in part, the Big Bang?
I've just read about something I had never of before, false vacuums. After reading a couple descriptions of what a drop (or rather, a vacuum metastability event) would imply, I thought of the Big Bang....
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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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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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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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Why didn't a black hole form right after the Big Bang? [duplicate]
Why didn't a black hole form right after the Big Bang and the universe contract towards a singularity?
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Conservation of Energy in the Universe [duplicate]
Possible Duplicate:
Is energy really conserved?
Why can’t energy be created or destroyed?
One of the laws of the universe that dazzles me the most is the law of conservation of energy. I ...
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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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Do we need dark matter and dark energy, if the behaviour of the universe in its initial stages was similar to that of the Sun? [closed]
According to CMBR the universe was a cloud of plasma and was a perfect black body, $380,\!000$ years after big bang.
But the Sun in our solar system also is in the state of plasma, thus making it a ...
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How is Big Bang related to theory of relativity?
I'm not someone with good scientific knowledge, so if my question are weird, correct me.
I was reading about big bang and I came by the theory of relativity. Can someone explain the relation between ...
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Age of the universe $ \equiv 1/H$?
How can the age of the universe be calculated as $1/H$, with $H$ the Hubble constant, when its expansion has been far from linear?
The $1/H$ comes from Hubble’s law, and implies that the universe ...
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Has anyone ever tried to formulate physics based on computer science or information processing?
Some physicists and university researchers say it's possible to test the theory that our entire universe exists inside a computer simulation, like in the 1999 film "The Matrix." In 2003, University of ...
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How can we still see the CMB? [duplicate]
May seem stupid but i cant wrap my head around it. if a star explodes we eventually see it when the light gets here. but once its got here we see the event and the star is now gone, we cant see it ...
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How bright was the universe after Big Bang during photon epoch?
After 10 seconds of Big Bang, most of the leptons and antileptons annihilate each other leading to an outburst of photons. The universe was said to be dominated by photons resembling a glowing fog. ...
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How do we know that space expanded with speed faster that a speed of light during big-bang inflation?
How do we know that space expanded faster than a speed of light in inflation?
I have read this Phys.SE question, and it says that limit for faster than a speed of light is for matter and waves only.
I ...
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Universe Expansion as an absolute time reference
Why we call "constant" to the Hubble constant?,
if the universe were really expanding then the Hubble "constant" should change, being variable, smaller and smaller..with "time".
Other example/view ...
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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 ...
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What happened during the Planck Era of the Big Bang?
If you look at a big bang timeline before 10 to the -43 seconds you can see
Planck time - ????
So I googled it and was met with
Before 1 Planck Time
Before a time classified as a Planck ...
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The first $10^{-35}$ seconds [closed]
I am a rank amateur, so please forgive me if the answer to this is well-known.
The following quote can in a weekly update for an EdX course I am following in astrophysics:
"And what a week it's ...
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Excluding big bang itself, does spacetime have a boundary?
My understanding of big bang cosmology and General Relativity is that both matter and spacetime emerged together (I'm not considering time zero where there was a singularity).
Does this mean that ...
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In the big crunch theory, when the big crunch singularity forms, can the resulting black hole decay through hawking's radiation?
I've been pondering about this and I couldn't really find the answer for this. The big crunch theory postulates that the universe will eventually stop expanding and reverse back in on its self into a ...
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Why is Big Bang Nucleosynthesis favored over Stellar Nucleosynthesis?
We know that a hot soup of plasma as it cools (as space expands) can produce light elements if the baryon-photon ratio is just right and the space expands quickly enough so that the neutrons and ...
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Is the commonly accepted Universe age of 13.8B years really accurate? [closed]
Hmm...challenging the error margin of a specific calculation result of a specific model based on confirmed inconsistencies is regarded as "opinion-based". Interesting. Just curious, is the ...
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Black hole cosmology vs. Big Bang cosmology
The evidence for Big Bang cosmology is an expanding universe. The expansion of the universe is accelerating. Gravity causes acceleration. What evidence is there that proves everything is moving away ...
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Any theory/author using the white hole model to explain the birth of the universe?
The maximally extended Schwarzschild solution (Kruskal diagram) envisages a white hole, which is the time-reverse of a black hole, i.e. a part of spacetime from which things can escape to us, while we ...
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Why don't we see galaxies going back in time?
Galaxies 4,200 megaparsecs away will travel faster than the speed of light away from each other, so why don't we see those galaxies as Going back in time up to the moment of the big bang?
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How long was the first second?
After the Big Bang all of the matter in the observable universe was condensed into a space that was very small (grain of rice sized).
The time dilation due to gravity should have been very large. So ...
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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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The Helium mass fraction from the Big Bang Nucleosynthesis
In Perkin's book Particle Astrophysics (page 144): I do not understand how one comes to the following expression (the second equality with $r$) for the Helium mass fraction due to the Big Bang ...
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Was Planck's constant $h$ the same when the Big Bang happened as it is today?
Was Planck's constant $h$ the same when the Big Bang happened as it is today?
Planck's constant :
$$h= 6.626068 × 10^{-34}\, m^2 kg / s,$$
$$E=n.h.\nu,$$
$$\epsilon=h.\nu$$
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Why do we need the concept of dark energy to explain the expansion of the universe?
Why can't the expansion of the universe be thought as the Big Bang itself still in progress? Why do we need to introduce dark energy? The Big Bang was powerful, and that explosion itself could still ...
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spacetime expansion and universe expansion?
First of all, does the expansion of spacetime solely cause the expansion of universe?
Secondly, if spacetime is the sole cause, do objects(matter with mass) themselves expand?
Thirdly, by spacetime ...
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How were quarks made?
I recently read about the early universe and found that first quarks were made $10^{-12}$ seconds after the inflation or the beginning.
But what was the cause of this minute delay, since inflation ...
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Can Hubble law be explained by galaxies moving away from one point at random constant speeds?
Let’s put a lot of material points at coordinates (0,0).
Let’s give them completely random velocities.
Let’s evolve this system for some time ...
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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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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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Where did energy come from?
So it is my understanding that before the big bang there was a very small point that held all of the matter in the universe. My question is what form did energy of the universe take on when it was in ...
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Quantum Wavefunctions Without Space
A handful of physicists have a rather peculiar definition of 'nothing' in terms of cosmology. Their claim is that the Universe, assuming it has 0 total energy, could have arisen from nothing but ...
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Infinite Universe and the big bang
OK, I was thinking of the big bang and how it relates to an infinite universe.
If the universe is infinite is mass and there was a big bang, then at the big bang there was an infinite amount of ...
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Many times speed of light [duplicate]
http://www.huffingtonpost.com/2014/03/24/theory-of-everything-big-bang-discovery_n_5019126.html
What does "many times speed of light" really mean in this context? For a layman it's easy to draw wrong ...
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Approximation of the energy for low $T$ in the early universe
In Perkins `Particle Physics', to compute the baryon-antibaryon-ratio, he uses that for $Mc^2\gg kT$:
$$E= Mc^2 + \frac{p^2c^2}{2m}.$$
I realize that the approximation comes from $E^2=M^2c^4 + p^2c^2$ ...
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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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Can we look further than the CMB?
As I understood it, the map of the cosmic microwave background (CMB) corresponds to the time when photons decoupled from matter, making the universe transparent. In this sense, we might expect the CMB ...
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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 ...
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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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(Physics Newbie) Reaching the edge of the expanding universe
Say you have a space ship so fast that it was able to instantly reach the edge of the expanding universe.
and you decided to try and drive straight into that edge, would you :
Ram into something ...
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Where are all the Population III galaxies?
We can now see back to 400 million years after the Big Bang. Yet we still haven't seen any Population III galaxies. Why is this? How do metal-rich galaxies evolve in just 400 million years?
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Could a pocket universe be birthed out of the negative pressure in our universe?
I have just recently started learning about inflationary cosmology so I don't know much about it. But from my understanding, the theory says the big bang was started by the expansion of a small region ...
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Why is the gravitational constant.. constant? [duplicate]
Many scientists have now come to the conclusion that a big bang might not explain the 'start' of the universe and are coming up with alternatives. Could it be that gravity is dependent on the ...
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Is there an absolute center of mass exist in the universe? [duplicate]
By the "absolute center of mass" I mean the center of all the matter that exists in a given moment. My friend asserted that today and it intrigued us very much but since we only have a CS degree and ...
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