# Tag Info

-7

Some people have very long explanations of why the universe can be created out of nothing "because the universe always does this". As a counter argument: There is no proof that the universe always does this. It is only theoretical. If you believe that the whole universe can be created out of nothing, it means you could create energy and matter out of ...

7

These types of theories that physicists such as Krauss espouse of a "Universe Coming From Nothing" are quite flawed, as by no means are they talking about nothing! Further, the concepts of particles, mass, and energy are not even well-defined when talking about the universe in general. I wrote a paper on this (excuse the shameless self-promotion), it can be ...

8

You're quite correct that measuring time from the Big Bang does separate spacetime into a time bit and a space bit, but this isn't arbitrary. When we want to describe the universe around us we need to choose some coordinate system that we can use to record physical quantities. Whatever coordinate system we choose will have one coordinate that behaves like ...

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Let $|\Omega\rangle$ be the quantum state that describes the whole universe. Certainly it doesn't make sense to talk about the entanglement of $|\Omega\rangle$ with something else, since $|\Omega\rangle$ describes everything. However, we can meaningfully discuss the entanglement of the marginals of $|\Omega\rangle$: ...

0

A particle can only be maximally entangled with exactly one other particle. If it helps, you can think of being maximally entangled as having a perfect relationship between two particles rather than either particle having a perfect property in the slightest. If you had a perfect spin up (in a particular direction) then obviously you could have some (that ...

4

If you "run the clock backwards" using the Friedmann equations, you can avoid a singularity; you just need the pressure and energy to behave in the right way when the Universe was very hot and dense. The catch is that "the right way" in this case means that $\rho + 3 p < 0$; in other words, either the energy density or the pressure (or both) have to be ...

2

The Big Bang was originally just the zero time limit of the FLRW metric. I'm not sure that Big Bang Theory has a meaning outside of CBS, but to the extent that it does have a meaning it is synonymous with the solution to Einstein's equations for a homogenous isotropic universe. Life is more complicated now because we believe the universe underwent a period ...

0

As the universe expands, isn't energy required for stuff to fill in? If you had a universe with a cosmological constant of the right size and magnitude and nothing else, it is possible to expand, in particular there might be no mass, no matter, no antimatter, no dark matter, no light, nothing except space, time, curvature, and a cosmological constant. You ...

2

CMB hasn't a frequency but a typical black body frequencies x radiances distribution. With the Planck law, the curve distribution gives the temperature of the radiation. I found this image in a previous question Relationship between temperature and wavelength? As you can see, each temperature has a typical curve. Yes, red/blueshift affect the ...

4

No. Light travels at the speed of ... light, when measured locally in inertial reference frames. And the relationship between wavelength and frequency is $\lambda = c/f$. As the universe expands, the wavelength of the cosmic microwave background photons is "stretched" and thus their frequency must decrease by the same factor of $(1 + z)$, where $z$ is the ...

-6

Has the frequency of CMBR changed at all since the beginning of the universe? The usual answer is yes. It's thought to have redshifted by a factor of a thousand. But there is an issue: conservation of energy. Where did the energy go? This is an intriguing thread to pull, because we don't know of anything that's in breach of conservation of energy. There ...

0

Theoretically, the CMBR is what we see of the early visible universe. If we could be there to observe it, we might see much higher frequency radiation. However, due to the expansion of the universe, the wavelengths got stretched out and the frequency redshifted. Or perhaps you can say in our reference frame, we happen to measure these photons to be ...

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I think, John Rennie's answer is far far better than anything I can do, but I'm going to give you the "universe for dummies" answer anyway. Mass of the observable Universe: 10^53 KG Density of the observable Universe: 9.9×10−30 g (equivalent to 6 protons per cubic meter of space - not very dense.) Source (Wiki): ...

1

Energy, in the context of the universe and the models used in describing it , is in the stress energy tensor, which contains the energy/mass transformations. The accepted at the moment model for the universe is the Big Bang model, as summarized in this plot , is a good fit to the available observations using all known physics to date. Known physics is ...

-2

This looks like another Chicken or the egg problem. I think I have the answer. The amount of energy and matter are constant. Remember there is only energy. Matter has been called "energy at rest." The two often change places but the quantity in the infinite universe is the same. The evidence for the Big Bang was recently presented as a residual background ...

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