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15 votes

Was the "demon core" hot?

A simple way to estimate this would be to check reference decay heating powers for the isotopes. From here we can find a value of $1.9~\mathrm{W}\,\mathrm{kg}^{-1}$ for plutonium-239. For a sphere ...
Riley Scott Jacob's user avatar
11 votes

What mistake did Einstein make in 1911 when he miscalculated the light deviation?

The 1911 paper can be found here in German and there is an English translation here. The GR prediction is roughly $\displaystyle \frac{2GM}{R}\left(\frac{1}{v^2}+\frac{1}{c^2}\right)$ radians, and he ...
benrg's user avatar
  • 27.3k
7 votes

Gravitational attraction between two bodies

As it turns out, only an inverse square law of gravitation leads to Kepler's laws of planetary motion, which were established prior to Newton's time. Newton had worked out the details privately and ...
Albertus Magnus's user avatar
4 votes

Gravitational attraction between two bodies

Newton arrived at the $\frac{1}{r^2}$ law empirically quite a while before analyzing the planetary motion in the solar system. He did this by comparing the acceleration $a$ experienced by bodies at ...
Thomas Fritsch's user avatar
2 votes

Gravitational attraction between two bodies

Newton thought of light as particles ("corpuscles") radiating out from the source. Any radiating source naturally follows an inverse square law because the area of the expanding radiation ...
KDP's user avatar
  • 5,201
1 vote

Gravitational attraction between two bodies

From an experimental point of view, imagine that you do measurements of the gravitational forces at various distances. You would quickly see that half the distance does not just double the force, it ...
Steeven's user avatar
  • 51.3k
1 vote

What are the differences between Navier and Stokes versions of equation?

It took some years to get the current form of the Navier$-$Stokes equations, as it usually happens in Science: a well-established model is usually a result of some years of development and ...
basics's user avatar
  • 9,521

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