# Tag Info

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### What is the most accurate measurement of the Astronomical Unit?

The astronomical unit was defined to be exactly 149 597 870 700 meters in 2012, so it is no longer a measured value. In fact, it never was a measured value. It was instead a computed value, and it was ...
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### At what point in history was the idea of planets being spit out by the sun abandoned?

That specific idea doesn't seem familiar to me, and I work in that field. Particularly this idea would only be called 'theory' when making testable predictions. The only thing that comes to mind here ...

### What do the symbols signify in Dr. Becky Smethurst's radiation pressure equation for black holes?

Epsilon is a factor to describe how much of the mass that is falling towards the black hole is converted to photons. The general equation for radiation pressure is (source) P_{\rm rad}=\frac{L}{4\pi ...
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### At what point in history was the idea of planets being spit out by the sun abandoned?

Between 1965 and 1980 I recall a book from the "Ladybird" series of short non-fiction books for children which included two possibilities for the formation of the planets. One was "...
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### What is the most accurate measurement of the Astronomical Unit?

As mentioned in a comment, the AU is no longer measured, it is defined, as 149 597 870 700 metres, or exactly the distance that light travels in a vacuum in $499 \frac{9823}{2053373}$seconds. But I ...
• 127k

### At what point in history was the idea of planets being spit out by the sun abandoned?

Spit out? In 1955 my parents gave me an illustrated book on Astronomy, which gave two hypotheses: the Kant-Laplace (nebular) hypothesis, and Sir James Jeans' idea that a passing star pulled some ...
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### What is the most accurate measurement of the Astronomical Unit?

As Wikipedia says, the Astronomical unit is "roughly the distance from Earth to the Sun".  The astronomical unit was originally conceived as the average of Earth's aphelion and perihelion; ...
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### Visualized shapes of areas of total and partial solar eclipse

There are purpose-made animations for recent eclipses on the NASA pages: 2021 Annular Solar Eclipse. You can download the video, and with a decent player like vlc, you can thus go back and forth. You ...
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### Books to use for NSEA (first stage of IOAA in India)

I've bagged a gold medal for India in the IOAA-Jr, so I think I may answer your question to some extent. Math and Physics are pretty standard introductory JEE level stuff they ask in NSEA. If you take ...

### Book for young enthusiast

Try Astronomy today, by Eric Chaisson and Steve McMillan. It is very comprehensive, easy for people with little background in mathematics or astrophysics to understand, and has plenty of visuals to ...
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### Book for young enthusiast

David A. Aguilar seems like a really good author to read. Basically, nearly all of his books do not use pain-in-the-a** algebra or neuron-damaging equations, easy to digest for a teenager or perhaps ...
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