# Tag Info

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The Pauli Exclusion Principle forbids two indistinguishable fermions occupying the same quantum state. It does not prevent them getting arbitrarily close together so long as they have very different momentum states. The big bang model relies on classical General Relativity. When we go back to scales where quantisation of space might become important (i.e. ...

9

I think this is at best a weird typo, but more likely a confusion by the authors (who are not cosmologists or astronomers, but a biologist and a geologist). The book is 10 years old, but our view of the timeline of the evolution of the Universe was pretty much the same then. Note that the calculation of the size of the Universe as a function of time is a bit ...

8

That diagram does not depict the entire universe. At most, it depicts the history of what is now our observable universe (specifically, a 2D slice through it), with us at the center only because we're observing it. Someone at the furthest reaches of that portion of the universe would see us at the furthest reaches of their observable universe, and themselves ...

6

By request: Beyond the fact that the cosmic microwave background (CMB) is a direct prediction of the big bang model, there is the question of how you would produce it in any other way. It is remarkably close to being isotropic and remarkably close to being a blackbody spectrum - i.e. it is almost a perfect blackbody radiation field. A blackbody radiation ...

5

The CMB is visible at a distance of 13.8 billion light years in all directions from Earth, leading scientists to determine that this is the true age of the Universe. This is wrong in a few ways. First, we do have good reason to think that the CMB was produced around 13.8 billion years ago, but that doesn't mean it's 13.8 billion light years away. The light ...

4

A singularity isn't an object. It is a property of a differential equation. For example: $$t \frac{dx}{dt} + 2x= 0$$ This can be "solved" to give $x = \frac{C}{t^2}$, and given a value of $t$ and the corresponding value of $x$ the constant of integration can be found unless $t=0$. If you are given this equation and the value of x at time t=0, you can't ...

4

The universe started with "big bang" is a slogan for "There was a time when the universe was hot and dense, and this time may be considered to be the start of the universe, and the start of time." The universe has (as far as we know) always been infinitely large. That's not certain, but we have no evidence contradicting it. The universe ...

2

This seems to refer to the diameter of the observable universe at that time. The region of space that is now 93 billion light-years in diameter (in the comoving metric that takes account of the expansion of spacetime) was about 100 million lightyears in diameter at the time when electrons and protons combined to form neutral gas. The whole universe may well ...

2

In his book "Brief Answers to the Big Questions" completed by his colleagues after his death, Stephen Hawking does sort of mention that the negative energy created (along with equal amount of positive) at the time of Big Bang is in space now or is space as both matter-energy and space were created after the Bang. The universe is the ultimate free lunch. As ...

2

This is a difficult question to answer. Physics really starts after the big bang. Scientist don't know about the laws, if any, before the first instance after the big bang. The time before and during the big bang is really the province of philosophy.

2

The big bang (a singularity 13.8 billion years ago that was the beginning of time) didn't happen at all. Inflationary cosmology consists of: ΛCDM (aka "big bang") cosmology starting at a cosmological time of some small fraction of a second, preceded by an inflationary epoch lasting for an unknown amount of time (but at least 50-60 e-folds), ...

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(I can't comment)- See https://physics.stackexchange.com/questions/136860/did-the-big-bang-happen-at-a-point TLDR, The big bang happened everywhere in the universe at the same time, because it was the universe. The top answer goes more in depth.

1

the expansion of the universe is relative to where it is being observed from. Much like dots on a balloon. Its easy to point to the center of the balloon (like what the picture shows) because it is only a 3d object. But for higher dimensions we don't have the spacial awareness to understand where than center of the universe is (if there even is one)

1

There are theories which suggest that the universe is like a giant spring, constantly expanding and collapsing. Its possible that pre-big-bang, there was another universe which collapsed, only to re-expand into the universe we know now. But in reality we have no idea

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