# Tag Info

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I don't know if negative pressure, more importantly there is a theory of inflation, and some good evidence for it. It was caused by a yet unknown inflation field, with its parameters somewhat matching what the cosmic microwave background (CMB) measurements show. As for eternal inflation, it is speculation that if it could happen once it could happen ...

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Pocket universes have arisen in different theories. Just to name you two, one is alan Gut's inflationary theory idea that Eternal inflation produces pocket universes with all physically allowed vacua and histories. Another is that from sean carroll, who claims that inside every black hole there is an entirely new universe.

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We should start by saying that we don't understand the physics that produced a matter-antimatter asymmetry. It seems likely that the asymmetry was around one extra matter particle per billion or ten billion matter-antimatter particles, but this figure is based on general principles rather than any precise calculation. What this means is that if we take a ...

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It is not entirely crazy to think of there being a black hole lurking behind the origin of the cosmos. Some such as Smolin have suggested this sort of thing. I will offer what I think is maybe my favorite idea along these lines. I am going in part to recycle something I wrote previously. Sean Carroll, Matt Johnson and Lisa Randall showed that a black hole ...

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I've answered the questions I can below. @John Rennie already gave a link to Lemaitre's paper. Here's a summary from John Gribbin's The Scientists, on page 596-597: ...the Belgian astronomer Georges Lemaitre (1894-1966), who was also an ordained priest, independently published similar solutions [to those of Aleksandr Friedmann's] to Einstein's ...

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Okay, I'm going to start with your last question and work toward the top. While the early universe wasn't necessarily an inside-out black hole, it can be thought of as such (http://www.scientificamerican.com/article/according-to-the-big-bang/ explains this further). The universe is indeed still expanding and we can see that. The reason we are made of ...

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Here are some references: Time and chance by david Albert Time's arrow by huw price From eternity to here by sean carroll The direction of time by H. D. Zeh Physical basis of time Asymmetry by paul davies There are many other excellent books or articles about the subject. Especially, in relation to the foundation of statistical mechanics I saw Two ...

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We have to be careful what we mean when we say "moving away". Imagine a grid in which we are at the origin and there are light sources located at each of the grid intersections. If the grid stays as it is while the light sources accelerate away from us, their light will appear to be redshifted. If you set up the accelerations such that everything moves ...

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That is not quite that simple. There is theory and measurements, and it places some constraints. There is more. First, if the universe is infinite now it was infinite at the Big Bang. You can have an infinite universe and have it all in the spacetime at the Big Bang. It does not grow to be infinite, it either is or is not. (Ignoring multiple dimensional ...

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As you and others have said, it looks like Boltzmann could plausibly be credited with the idea that the universe had a low-entropy past: The second law will be explained mechanically by means of assumption A (which is of course unprovable) that the universe, considered as a mechanical system—or at least a very large part of it which surrounds us—...

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Infinity is a mathematical concept, as well as the concept of variables describing dimensions. Physics is about observations, either in the laboratory or of the cosmos, which are fitted with mathematical models. It started with the geocentric system, became the heliocentric system and then the realization that the galaxy is composed out of sun like stars, ...

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So that narrows it down to some time between 1896 and 1979 The second law was known to Clausius, and trivially implies the knowledge that the entropy in the far past was much less than now. (That is, if one is permitted to apply the notion to the universe as a whole; cf. below.) It seems that Clausius stated explicitly (in 1856) only the extrapolation to ...

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The comment by Walter is on the right track: The "acceleration" does not refer to the fact that recession speed increases with distance, because this is just a consequence of space expanding everywhere. This is why we measure the expansion in km/s per megaparsec. Today, the expansion rate (the Hubble constant) is $H_0 \simeq 70\,\mathrm{km}\,\mathrm{s}^{-1}\,... 1 The FLRW energy equation for the motion of test masses in the universe is $$\left(\frac{\dot a}{a}\right)^2 = \frac{8\pi G\rho}{3}.$$ the scale factor for space is$a$and its time derivative is$\dot a$. I derived this from Newtonian dynamics. The density of mass$\rho\$ for the case of a quantum vacuum energy level is constant. I now replace this with ...

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I would argue that the expanding of space cannot and should not be understood adding space into space, nothingness into nothingness. We have no way of observing the space itself as a reason like the one you presented likes. Things seem to get away from us through and the observed mechanism is called redshift, which, in close distances(inside let's say the ...

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Tl,dr: Entropy is the right definition, because it's incredibly useful in the description of statistical and thermodynamic systems. Whether or not it quantifies "disorder" in whatever sense of the word is completely irrelevant - it just so happens that it can be interpreted that way. Entropy is not a measure of disorder. At least not really. Then again, ...

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The noboundary condition means there is no boundary that marks the end of space or time. With respect to time one might think of the lines of longitude on a globe as representing the time direction at different point in a spatial manifold modeled as the lines of latitude. As one looks further to the north, which is the big bang that eventually you look north ...

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Edit: As noticed above in the comment, let's define BBN. Big Bang Nucleosynthesis is a process of formation of light nuclei from primordial protons and neutrons in the Early Universe. Standard BBN theory is extremely successful in predicting the abundances of multiple nuclei and is very sensitive to a number of parameters. Let's see how it holds. Below you ...

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The technique is to sight in on known frequencies of sources in the Milky Way and other galaxies. Any signal bearing the multiband set of data is subtracted.

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