# Tag Info

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The facts: No antigravity has been observed ... and no DE has been observed also. It was discovered (measured) in 1998 an acceleration in the expansion of space. The mass (M) is the source of gravity (G). Every force has a source of it, charges, masses,... . The source of antigravity (AG) is ??????????? (SoAG). In the absence of apparent source of AG we ...

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Imagine you have a star sized ball of gas that is in equilibrium i.e. the pressure of the gas exactly balances the inwards gravitational force. Now imagine compressing the gas. This has two effects: The first effect is the obvious one that compressing the gas increases the pressure, so the result is an outward force and if we stop compressing the gas we ...

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You should distinguish two things: the pressure itself, and the gravitation that it creates. First of all, why does it create some gravitation? Because energy does. It is not the mass of the Earth that pulls us down - it is the energy of that mass, $E=mc^2$, that makes us heavy and not flying but walking. And the energy does that indirectly. First, it ...

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Here is an excellent (blog) summary of the results. The most relevant figure being: Here is the full index of the Planck release papers. The 'cosmological parameters' paper is the most relevant.

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There is a similar plot on page 41 (fig 25) of Planck 2013 results. XVI. Cosmological parameters, although it doesn't display supernova data.

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How do we know the universe is expanding and the speed of light isn't slowing instead (thanks to innisfree for the idea of where to look.) From wikipedia By the 1990s and on into the twenty-first century, a number of falsifying observations have shown that "tired light" hypotheses are not viable explanations for cosmological redshifts.[2] For ...

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It is important to remember that very early ($10^{-10}$ seconds) on in the universe history there was no distinction between dark matter and normal matter as it is expected that all the forces were unified and there would be no difference between dark matter particles and normal matter particles since there were "no particles" in the classic sense. Recall ...

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This question doesn't have a "correct" answer yet because we simply don't know what dark matter is. That aside, assuming dark matter consists of particles (WIMPS for example), the LHC hasn't turned up any sign of dark matter production yet. Since the number and "size" locations in the Universe that are able to reach LHC energies are very limited compared ...

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The expansion of the universe is (approximately) described by the FLRW metric. The Wikipedia article I've linked gives lots of gory details, but the key result we need is the dependance on the acceleration on the density and pressure: $$\frac{\ddot{a}}{a} = -\frac{4\pi G}{3}\left( \rho + \frac{3p}{c^2} \right) + \frac{\Delta c^2}{3}$$ If there is no dark ...

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I guess that you are imagining an expansive force accelerating the Universe versus gravity pulling the Universe together, and that if somehow gravity were weaker, the expansive force would win. That is not the correct picture. In popular models, the accelerating Universe is caused by gravity, because of a vacuum energy with negative pressure (see dark ...

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I think the term acceleration implies a change in direction of the net forces acting on galaxies on the large scale. Gravity (regardless of magnitude) acts to collect the galaxies, while the acceleration acts in the opposite direction.

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