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What is your frame of reference for what to measure for elevation from on the moon? How does a compass perform in deep space? What does it point to? Best Regards. Also, you guys should watch adventure time. It is majestic.
Answer 1:

What is your frame of reference for what to measure for elevation from on the moon?
That’s an interesting question– one that required a bit of research. On Earth, elevations are reported relative to sea level, but there are no seas on the moon. I found out that most lunar elevations are reported relative to the surface of sphere with a radius of 1738 km (e.g., Margot et al., 1999). This means that if you took an imaginary ball and lined-up the center of the ball with the center of the moon, the surface of the ball would be the reference. Things like lunar volcanoes would stick up above the surface of the ball and have positive elevation. Things like lunar craters would be below the surface and have negative elevation (like “below sea-level” on Earth). The moon is not actually a perfect sphere; it is a spheroid or ellipsoid. This means that it is sort of egg shaped and not perfectly round. Because it is egg-shaped, a line from its center to its surface (the radius) is going to be different lengths in different directions (it will be shorter from the center to the surface of the narrow part of the egg and longer from the center to the surface of the pointy part of the egg). If you took the egg shaped moon and squashed it back into a sphere, the sphere would have a radius of 1738 km.

How does a compass perform in deep space?
What does it point to?
Best Regards. Also, you guys should watch adventure time. It is majestic.
Well, I have never really thought of that before. As a field-geologist I use a compass all of the time (on Earth). A compass is made up of magnetized material; many types of metal alloys that contain iron can be magnetized. Because the needle is magnetized, it responds to Earth’s magnetic field. The magnetic field is potential field. When the magnetized compass “sees” the magnetic potential field, it will experience a force and deflect. This will make the needle point toward the north magnetic pole and away from the south magnetic pole. Earth has a solid- metal inner core that rotates in a molten (liquid) outer core. This system, called the geodynamo, is what created Earth’s magnetic field. As you get farther and farther from Earth (out into space), its magnetic field get weaker and weaker…

So, how will a compass work in deep space?
A compass needle will always respond to a magnetic field, but are there magnetic fields in space? I think that there must be magnetic fields everywhere in space, though they might be caused by different things. If you are very far away from a body that has a geodynamo (like a planet with a molten core), the magnetic field is not going strongly affected by it. Magnetic fields are also generated by electrical currents, which is basically the movement of charged particles like electrons, protons, and ions (atoms that have lost or gained some electrons). This is basically how the geodynamo is generated, but a different version of this process might be important in space. Currents of ions known as solar winds are very common in space. The movement of these ions would cause a magnetic field that a compass would respond to. The magnetic field that is generated by a current is always perpendicular to the current, so the compass needle would point at a right angle to the direction of the current.

There might be other important sources of magnetic fields in space. You should check out the NASA website (nasa.gov) for more information!

Margot, J.L., Campbell, D.B., Jurgens, R.F., Slade, M.A. (1999). Topography of the lunar poles from radar interferometry: A survey of cold trap locations. Science, 284, 1658–1660.



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