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 Post subject: Astronomy factoid
PostPosted: Fri Aug 25, 2017 2:43 pm 
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230 million years from now: Prediction of the orbits of the planets is impossible over greater time spans than this, due to the limitations of Lyapunov time.

Lyapunov time is the characteristic timescale on which a dynamical system is chaotic.

If time-travel was possible, travelling back to the Triassic, we'd be under the impression of living on an alien planet rather than a planet which eventually becomes Earth. The sun would be dimmer (https://en.wikipedia.org/wiki/Faint_young_Sun_paradox), stars and constellations wouldn't be recognizable, and Earth's environment would be different but familiar.

Hayes, Wayne B. (2007). "Is the Outer Solar System Chaotic?". Nature Physics. 3 (10): 689–691. Bibcode:2007NatPh...3..689H. arXiv:astro-ph/0702179 Freely accessible. doi:10.1038/nphys728.

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 Post subject: Re: Astronomy factoid
PostPosted: Fri Aug 25, 2017 2:47 pm 
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In 600 million years, Tidal acceleration moves the Moon far enough from Earth that total solar eclipses are no longer possible.

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The Moon's orbit is increasing by about 3.8 cm (1.5 inches) per year. When the Moon's mean distance from Earth has increased an additional 14,600 miles, it will be too far away to completely cover the Sun. This is true even at perigee when its disk will be smaller than the Sun's disk even at perihelion. At the current rate that the Moon's orbit is increasing, it will take over 600 million years for the last total eclipse to occur. A complicating factor is that the size of the Sun itself will grow slightly during this time, which will act to make the time of "no more total eclipses" a bit sooner than 600 million years.


https://web.archive.org/web/20100312030 ... 06/faq.php

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 Post subject: Re: Astronomy factoid
PostPosted: Thu Feb 08, 2018 9:29 am 
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What's it like in the Bermuda Triangle of Space?

http://www.bbc.com/future/story/2018020 ... e-of-space

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Astronauts fly through an anomaly with such high levels of radiation, computers stop working.

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