# Tag Info

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Following Edwin Hubble, it is widely believed that the universe is expanding, which is based on the red-shift of light from distant objects. Can dark matter cause light to be red-shifted and make it look like the universe is expanding while in fact it is not? The problem is cosmic dust can red-shift light without Universe expansion. Since cosmic dust is ...

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I want to start by clarifying what M-theory is, in relation to string theory, just so the context of my answer will be understood. These days, "string theory" encompasses five ten-dimensional superstring theories, the 11-dimensional M-theory of membranes, 26-dimensional bosonic string theory, "supercritical strings" in more than 10 dimensions, and other ...

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Our Universe is a larger version of a galactic polar jet. 'Was the universe born spinning?' physicsworld [dot] com/cws/article/news/46688 "The universe was born spinning and continues to do so around a preferred axis" Our Universe spins around a preferred axis because it is a larger version of a galactic polar jet. 'Mysterious Cosmic 'Dark Flow' Tracked ...

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In cosmology, when you apply the Einstein equation to the whole [homogeneous and isotropic] universe, you get the Friedman-Lemaître-Robertson-Walker (FLRW) equations. These equations dictate how the size of the universe evolves depending on its material content. The different components are characterized by their equations of state, the ratio between ...

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I agree with atsby, and would like to say that Dark Matter and Dark Energy are two fundamental concepts of which we know very little about. However I doubt that Dark Matter can be converted to Dark Energy the same way we can convert normal matter to energy, let alone convert Dark Matter to Dark Energy at all. For starters, Dark Matter is the substance ...

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Mass and energy are the same thing. If you have a sealed internally reflective box of photons, it will have inertia and a exert a gravitational pull on any other mass/energy that may be around. http://usersguidetotheuniverse.com/?p=2865 That being said, no properties of dark matter or dark energy are known. These terms are used to refer to matter and ...

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This is a misconception. Theoretically, Dark Energy is a form of energy which accelerates the expansion of the universe, whereas Dark Matter is thought to be made up of weakly interacting particles (which account for most of the matter in the universe). Dark Matter and Dark Energy have completely different properties, and their names don't imply that they ...

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Dark matter are not related in that way. Dark energy is the energy responsible for the accelerating expansion of the universe. Dark matter is a source of gravitation which we couldn't see directly.

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In the FLRW model which is used today normal (baryonic) matter and dark matter together add up to matter. It dilutes with the growing radius to the third power (because volume is proportional to radius³). So the ratio matter : dark matter is and was always the same, at least in the plot you showed and the model that was used there. Edit: Maybe the 5.25 to ...

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The ratio of dark to baryonic matter is 5.25 in the first diagram and 5 in the second diagram, but I don't think the difference is significant. We don't know the densities with absolute certainty, especially near the Big Bang, and the small difference between the ratios is probably just down to the uncertainties in the densities. We would expect the ratio ...

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Dark matter/energy is related to the Big Bang but probably not as much as your popular thinking implies (don't really know what you're referring to). So let me explain the link. Most people know dark matter solves missing gravity in galaxy's. However this is only the first and most obvious clue that led to dark matter. Another one is key to inflation ...

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This is an interesting suggestion, and I don't claim to know much about neutralinos, but to be degenerate they would need to have a temperature $$T \ll \frac{p_F^{2}}{2mk_{B}},$$ where $p_{F}$ is the Fermi momentum and $m$ is the neutralino mass, thought to be in the range 100 GeV/$c^2$ - 1 TeV/$c^2$. The present mass density of dark matter in the solar ...

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Are there another views on what dark matter/energy is? Yes, but you tend not to hear about them because there's a presumption that dark matter consists of particles. This is despite Einstein saying "the energy of the gravitational field shall act gravitatively in the same way as any other kind of energy" in The Foundation of the General Theory of ...

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I think the strong CP problem is still a pretty important problem. Although some people don't worry too much about these fine-tuning problems. Just like some people didn't consider the flatness problem a big deal before the inflation theory explained it. So like every problem, it's as big as you make it. It depends on how much you value naturalness... ...

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