# Tag Info

### Why are what end up being meteorites not in stable orbit as planets and large asteroids are?

A couple of factors. Firstly most small asteroids are in stable orbits. They don't approach any planets closely, and orbit in ellipses that are stable on timespans exceeding the age of the solar ...

### What is the **actual** average distance of the Moon from Earth?

Lunar theory is complicated. ;) The Moon's orbit around the Earth is only approximately a constant Keplerian ellipse. As I mentioned here, the Moon's orbit around the Earth-Moon barycentre has an ...

### What is the **actual** average distance of the Moon from Earth?

Your guess on the requirement for calculus is correct. What you need to do is integrate the moon's distance over one orbit to find an average distance. Starting from the equation below, the Moon's (or ...
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### What is the **actual** average distance of the Moon from Earth?

Mean distance averaged over time for any Keplerian orbit is $a(1+\frac{1}{2}e^2)$, where $a$ is the semi-major axis and $e$ is the eccentricity. Using your NASA fact sheet, I get about 384,979 km for ...

### Explanation of an imaginary transformation occurring in the determination of trigonometric series for the elliptical equation of the center

 The first part of the specific question here asks what is the meaning of the 'imaginary transformation' in Scheibner's 1880 paper. If I read the paper right, there has been a confusion of symbols, ...

### How time-symmetric is orbital mechanics?

It's hard to give a definitive answer to this question. For the spherical-cow, Physics 101 answer, the answer is yes, the dynamics of orbital mechanics are time-reversible. However, as I'll get into ...

### How time-symmetric is orbital mechanics?

It seems that a source of time-asymmetry is becoming appreciable in increasingly high-precision accounts of the moon's orbit. The latest JPL lunar and planetary ephemeris comes in two varieties, DE440 ...