5 ms·

Solar eclipse measured on Mars, affects interior

39 points by dnetesn 6y ago

Chris2048 6y ago
Mars (mean diameter 6780 km) has two known moons, Diamos (mean diameter of 12.4 km) and Phobos (mean diameter of 22 km). So Phobos is ~0.3% the diameter of mars, and Diamos is ~0.2%; for comparison the moon is 27% the diameter of Earth, though is considered abnormally large. Also, "Mars may have moons smaller than 50 to 100 metres". I'm surprised there's no lower limit on what is considered a moon. Wikipedia suggests smaller objects are called "moonlets", but I guess Russell's teapot would count as one, but for the uncertain fact it might not be considered "natural"?
- lizknope 6y ago
  We have changed the definition of "planet" multiple times so I'm sure we will redefine "moon" as well. Pluto was recently demoted but this has happened before to Ceres and others. https://en.wikipedia.org/wiki/IAU_definition_of_planet https://en.wikipedia.org/wiki/IAU_definition_of_planet By 1851, the number of "planets" had grown to 23 (the eight recognised today, plus fifteen between Mars and Jupiter), and it was clear that hundreds more would eventually be discovered. Astronomers began cataloguing them separately and began calling them "asteroids" instead of "planets"
est31 6y ago
Has slightly more comments: https://news.ycombinator.com/item?id=24383060 https://news.ycombinator.com/item?id=24383060
andy_ppp 6y ago
"Its orbit passes between the sun and any given point on Mars about once each Earth year. Each time it does so, it causes from one to seven solar eclipses within the space of three days." Does anyone have an explanation of how this works? Seven solar eclipses seems like a lot and I can't seem to visualise what is happening, presumably it's Mars spinning and Phobos staying still that causes this, but I can't understand why the difference is so huge.
- mercurywells 6y ago
  Phobos is extremely close to Mars so its orbital period is only 8 hours. Its inclination is also very low compared to our own moon. Therefore it is far more likely to cause an eclipse and it occurs in sets.
1DRACOSEA8 6y ago
12 KM that’s the dual graviton posited by DeWitt. I have written a WZW that predicts exactly this; but the proof itself, at this point. Remains mathematical. What you’re witnessing is the apparent perihelion between two gravitons acting; one short distance, the other long; the solution is a Gromov holomorphic homotopy of the seven sphere contraction to two dots on the Celestial plane.

39 points by dnetesn 6y ago

Chris2048 6y ago

Mars (mean diameter 6780 km) has two known moons, Diamos (mean diameter of 12.4 km) and Phobos (mean diameter of 22 km). So Phobos is ~0.3% the diameter of mars, and Diamos is ~0.2%; for comparison the moon is 27% the diameter of Earth, though is considered abnormally large. Also, "Mars may have moons smaller than 50 to 100 metres". I'm surprised there's no lower limit on what is considered a moon. Wikipedia suggests smaller objects are called "moonlets", but I guess Russell's teapot would count as one, but for the uncertain fact it might not be considered "natural"?

lizknope 6y ago
We have changed the definition of "planet" multiple times so I'm sure we will redefine "moon" as well. Pluto was recently demoted but this has happened before to Ceres and others. https://en.wikipedia.org/wiki/IAU_definition_of_planet https://en.wikipedia.org/wiki/IAU_definition_of_planet By 1851, the number of "planets" had grown to 23 (the eight recognised today, plus fifteen between Mars and Jupiter), and it was clear that hundreds more would eventually be discovered. Astronomers began cataloguing them separately and began calling them "asteroids" instead of "planets"

est31 6y ago

Has slightly more comments: https://news.ycombinator.com/item?id=24383060 https://news.ycombinator.com/item?id=24383060

andy_ppp 6y ago

"Its orbit passes between the sun and any given point on Mars about once each Earth year. Each time it does so, it causes from one to seven solar eclipses within the space of three days." Does anyone have an explanation of how this works? Seven solar eclipses seems like a lot and I can't seem to visualise what is happening, presumably it's Mars spinning and Phobos staying still that causes this, but I can't understand why the difference is so huge.

mercurywells 6y ago
Phobos is extremely close to Mars so its orbital period is only 8 hours. Its inclination is also very low compared to our own moon. Therefore it is far more likely to cause an eclipse and it occurs in sets.

1DRACOSEA8 6y ago

12 KM that’s the dual graviton posited by DeWitt. I have written a WZW that predicts exactly this; but the proof itself, at this point. Remains mathematical. What you’re witnessing is the apparent perihelion between two gravitons acting; one short distance, the other long; the solution is a Gromov holomorphic homotopy of the seven sphere contraction to two dots on the Celestial plane.