Celestia Forums

First step is to multiply the Sun's mass by 3. Then press the 1/X button to invert that. Then multiply that number by the Earth's mass. This gives you the m/3M term in the brackets in this equation . Then multiply that number by the distance. Finally, (I'm assuming you have a reasonably scientific ...

What are the masses of your planets? Your first two planets might be saved from collision in the very short term because of their 3:2 resonance (similar to Neptune and Pluto). But that outermost planet looks pretty massive. I'd guess that it would cause major instability throughout the entire region...

I saw the most intense Northern Lights 15 years ago in Minnesota, but what you're describing sounds just as powerful. The ones I saw started out dull and static. Like the hands of a clock, you could tell they were moving if you took your eyes off them for a minute and then looked back. But after abo...

Rassilon wrote:...Wheres grant?

lol... I was thinking the same thing. Many of these types of questions are followed by our guesses, and then followed by Grant's explanations and formulas.

We gets lots of fog in San Francisco too. Today is just overcast though. I can see a few miles out to the Pacific Ocean and can clearly make out the horizon. But looking up, I can't tell where the Sun is. The only shadows on the ground are under cars, and they're caused by the car blocking the sky a...

Just a guess.... The Earth's radius is 4 times larger than the moon's radius, so it's surface area of its visual disk will be 16x greater than the Moon disk from Earth. The Moon is a dark almost charcoal black color. The Earth has bright white cloulds, snowy plains and continents, dark land, and dar...

Tethys is very interesting for another reason. It holds 2 smaller moons captive in its L4 and L5 Lagrange points. Telesto and Calypso share an orbit with Tethys, orbiting Saturn 60 degrees ahead of and 60 degrees behind Tethys.

I"m not quite sure I understand your question. If you want points on the great circle, its just 0 to 360 degrees. If you want them as x & y points you could do x = cos(degree) * radius of Earth, y = sin(degree) * radius of Earth. If you want latitude and longitude coordinates on the surface of the e...

Good Luck! I also enrolled in a physics class at San Francisco State University this semester. I'm not going for a degree or anything. It's just that for as much as I love physics, I decided it would be nice to actually take a college level course.

In a double system, the barycenter is going to be at the same place as the L1 point, and orbits around the L1 point are always unstable. Think about the gravitational pull as a potential field and you'll see why. When the moon is closer to one planet than the other, it wil no longer feel a net forc...

I just spent a bit of time reading a thread about a flight mode using a simplistic gravity model, which I agree with fridger, you just cant do it. If I remember my physics classes, and I was a history major, so dont get mad if I get something wrong, isn't the following true: Gravity, as experienced...

But in the retrograde case (rotation slows down, potential energy decreases) where does the energy go? Rotation speeds up. If the Moon orbited Earth retrograde, it would speed up the Earth's rotation while being pulled into a smaller, faster orbit. If the primary body rotates more slowly than the s...

Thanks, will have a look, but actually more interested in seeing an accurate representation of space. - Seb Orbiter does an impressive job with the 8 planets (Mercury - Neptune) and Earth's Moon. It uses VSOP87 and an additional dll for the Moon. There's tricks you can play to get the other moons a...

Anyone got a handy way to grok this sort of thing? I groked it with my camera's light meter. I forget the exact numbers, but aiming it at a white piece of paper on the floor of my living room gave me a reading that was in the ballpark of 1000 - 2000 times dimmer than the same piece of white paper o...

Pluto is tidally locked to its moon, Charon. They orbit their barycenter in about 6 Earth days. So a day on Pluto is about 3 Earth days, and night is also about 6 Earth days. Same for Charon. Here's an old thread where the brighntess of the Sun at distant planets is discussed: http://www.celestiapro...

I don't believe that any object other than dust or particles have been observed passing through our solar system. So the shooting stars you see are all from here. The giveaway would be the speed. The Leonids in November are among the fastet meterors. I believe they travel about ~ 70km / second relat...

is it me, or can you actually see that Toutatis is non-spherical in that animation above? It seems to be tumbling as it moves... It's not just you. It appears tumbling to me too. But that's probably an artifact of the animation. I don't think Toutatis is large enough to be resolved in a telescope (...

When near the equator, that's how the crescent moon rises and sets every day, with the line connecting the cusps being horizontal. Since the moon must be directly above the Sun as defined by the Earth's horizon for this to happen, it's pretty rare from non-equatorial latitudes. If the moon were at t...

Thanks, Grant. Your formulas work perfect! (lol, I'm starting to think that should be my signature line)

My 30 billion km seperation between 1 & 0.05 solar mass objects was only varing by +/- 500,000 km. That's pretty darn circular!

The Moon is more heavily cratered than Mercury. Do you have a reference for that, or is it just a visual impression? It's usually said that the Mercurian and lunar highlands have very similar primary crater densities, though you see fewer secondaries on Mercury. Grant Much of what I know I learn fr...