# Tag Info

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Gravitational potential of universe can't be defined now because the universe has been expending due to this we can't find the exist value of gravitational potential. As the diameter of universe has being expend,gravitational potential become decrease & the gravity due to sun on all the planet would be decrease, because sun is the centre and all eight ...

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How fast does space/time travel? Fast. But note that there's no travelling per se, and that space expands. Have a google on that. Spacetime is a "space at all times" abstract thing. Here's a depiction of it, courtesy of NASA: It looks like a champagne flute on its side, without a handle or base. The time axis goes from left to right, and the diameter ...

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Your question is very easy to answer because the answer is just the value of the Hubble constant (or its inverse the Hubble time). The trouble is that it's hard to explain to a non-physicist what the answer means. I'll have a go, but you may find it hard going. When we are describing the expansion of the universe we can't simply talk about its size. That's ...

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time will disappear in the same way it appears I don't know how to explain it but in easy way the the end is just the beginning and it will look like a cycle as it began it will end

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The universe is described by a scale factor, normally indicated by the symbol $a(t)$, that is a function of time. We take the scale factor to be one right now, so in the past $a$ was less than one and in the future $a$ will be greater than one. Roughly speaking, if $a$ has the value $\tfrac{1}{2}$ it means everything was half as far apart as it is now, and ...

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The answer is a definite YES. A larger atom in the past explain all the observed features, namely the redshift and the time dilation. from Ned Wright's FAQ in Cosmology: Q: Is the Universe expanding or is it just that our definitions of length and time are changing? A: The definitions of length and time are not changing in the standard model. The second ...

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The simple answer would be no. If that were the case every thing in the universe would have the exact same gravitational pull. Meaning gravity on the moon, earth and sun would all be the same value and that is simply not the case.

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I will show that he Dark energy is an artifact of the referential used. We measure with atoms, ex: 1 kg is defined as an ensemble of atoms, lets say N, in Paris, such that one atom weights 1/N kg. Similar recursivity with length/time unit. We live at Earth's surface and not knowing that it rotates we conclude that the Sun rotates around Earth, daily. ...

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When treated properly, one has to study Einstein's equations with the dark energy as the source. For example, when the dark energy is cosmological constant (the most important subtype of dark energy), the resulting spacetime is a de Sitter space, a Minkowski-signature type of a hyperboloid. Galaxies move along geodesics and those geodesics are "repelling" ...

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Here is a model that might get you many features you look for. Imagine a balloon. Imagine the surface is expanding. If it is like bubble gum then as it expands it gets thinner and expands more easily, and it could pop. If however you had some objects free to move around the surface but attached by springs then they might slow the expansion and even make the ...

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What evidence is there for additional dark energy coming into existence when space increases? None. As I understand since cosmological constant is a 'constant' - increasing the space must generate additional dark energy that fills that space That's what people say. But we have no evidence whatsoever of anything wherein conservation of energy does ...

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At the moment we don't know what dark energy is so we formulate hypotheses and compare them to the experimental data. The two most popular hypotheses are: dark energy is due to a cosmological constant dark energy is a scalar field referred to as quintessence and both of these have the property that the total energy inside a volume of space increases as ...

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If we want to observe the universe expansion with the most straightforward and direct way we have to measure redshifts of galaxies. The minimum distance where this effect would start to be observable is that at which the speed of recession is larger than the average noise speed, which is around a few hundred $km/s$. Given that the value of the hubble ...

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Despite the comments, this question can be answered with physics. You didn't specify what you mean by either "everything" or "doubles in size" so I'll assume you meant all massive objects double in length along each orthogonal spatial dimension while maintaining their form and composition. The apparent speed and actual speed are unchanged. A radar dish on ...

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I hate to give a mainly-link answer, but Alan Guth's video about dark energy was very educational to me. He's the cosmologist who's a primary author on the inflationary universe theory. Basically, if I can summarize it, there can be a kind of material that has repulsive gravity rather than attractive gravity. In addition, its density in space does not ...

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Universe when created is filled on same number of matter and anti- matter . Maybe. Some particles, like photons, are their own antiparticles, others like electrons and positrons are anti-particles of each other. There is no real, objective, way to say which is matter and which is antimatter. We just said that up and down quarks were matter because ...

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The universe does not have a centre. See http://math.ucr.edu/home/baez/physics/Relativity/GR/centre.html

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How does dark energy allow the universes expansion to accelerate? I hope that it is clear to the questioner and the readers that the horse pulling dark energy is the experimental observation that the expansion of the universe is accelerating. Dark energy is proposed as the reason why the expansion is accelerating. It is called "dark" because it is not ...

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We can explain everything we see in universe by just assuming the rest mass of any particle decreases with time. Therefore the gravitational force will be zero. See for details this link https://www.scribd.com/doc/279174920/Decreasing-Mass-Cosmology-and-the-Accelerating-Expansion-of-the-Universe

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Read the article on this link https://www.scribd.com/doc/279174920/Decreasing-Mass-Cosmology-and-the-Accelerating-Expansion-of-the-Universe and you'll see that 'dark energy'isn't neccessary for the accelerating expansion of the universe

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Yes it changes. In this case 'dark enargy' is uneccessary. The cosmologicam model which is based on a changing Λ explaines the astronomical data perfectly.Read on this link for more details https://www.scribd.com/doc/279174920/Decreasing-Mass-Cosmology-and-the-Accelerating-Expansion-of-the-Universe Dimitri Deliyiannis.

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The Big bang theory model the time period when the Universe had hot dense soup of particles and the nucleosynthesis that happened.It's the FLRW metric that models the evolution of the Universe and the way the distance between two points in the space has been increasing. But what actually made the space to expand. The Big Bang. It is a solution of the ...

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I suspect this may not make much sense to non-GR heads, but the Einstein equation relates the curvature of spacetime to an object called the stress-energy tensor. The stress-energy tensor describes the properties of the matter/energy that is causing the curvature. In most cases we're only interested in the amount of matter/energy present i.e. its density, ...

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Nobody has any certain answers to this, but IMHO there's an obvious issue with the cosmological constant, which is "the value of the energy density of the vacuum of space". If it's really constant, we've got energy being continually created as the universe expands. That goes against the grain of conservation of energy. I'm not happy with that because I ...

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Rather belatedly, let me mention my answer to Did the Big Bang happen at a point?. This explains the geometry of the expanding universe in laymans terms, and should make it clear how it differs from the geometry of a black hole. because the geometry of the two solutions is completely different there is no reason to expect them to evolve in the same way, and ...

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The question details contain a misconception: "due to the expansion of the universe (and thus not related to the Doppler effect)". Actually, whether or not a distant galaxy is receding from us because of expansion or some other reason, the Doppler shift will be the same. (As a matter of fact, with the exception of spatial curvature and the cosmological ...

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First off, the Doppler effect (in this case cosmological redshifting of distant galaxies) is a direct result of an expanding universe, and was used by Hubble and others to measure the expansion velocities of such galaxies (and thus the universe itself). I found a great little ditty on this topic in Matt Roots' Introduction To Cosmology: The Expanding ...

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Anna's answer is perfect in the sense, that photons are indivisible particles, which during their life don't loose energy. Nor Faraday effect, nor magnetic fields or the dispersion with intergalactic dust made the redshift. At the end of the answer Anna pointed out that the universe is expanding we know from measurements of the velocities of clusters of ...

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Yes, photons do lose energy because of the expansion of space. Their wavelengths are increased by a factor of $(1+z)$ between when they were emitted at redshift $z$ and when we detect them now. Their energies are therefore decreased by a similar amount. The "tired light" interpretation of this effect has been discussed, debated and disproved. In my opinion, ...

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We live in the age of measurements and observations and specific mathematical theories that fit measurements and observations beyond any doubt. Photons are elementary particles. . They have zero mass, and other characteristics which separate them from other elementary particles . Can photons lose a small amount of energy over time when traveling large ...

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