I remember watching on a science TV show recently that almost all illustrations of asteroid belts are to dense. And in reality, you could fly through an asteroid belt and most lively never be at risk of hitting an asteroid.
Is this true? If these asteroids are so far away they don’t pose the threat of hitting a spacecraft flying through them, would an observer even see an asteroid on the journey through the belt?
NASA says about 600,000 miles.. That’s pretty close together as astronomical distances go, but would seem a pretty safe margin for most spacecraft.
I saw a science fiction movie once in which they got alarmed because they were one mile from the asteroid belt. It made me laugh.
I said never tell me the odds!
If you lived in on an asteroid in an asteroid belt you would not know about it unless you spent many hours tracking orbits with a telescope (or read about it someplace like SDMB). Asteroids are too small and distant to be noteworthy from one another.
A planet in an asteroid belt would certainly have more impact craters, but it’s a target thousands of miles across. You’re still not going to notice the impacts unless you hear about them through communications or go exploring for craters.
Space is just to big and empty to be visually exciting - even in the asteroid belt. Now if they wanted to have an exciting flight through Saturn’s rings that would probably closer to Star Wars type ‘asteroid belt’ in density.
Not only do they always get the density wrong they get the colour wrong too. Asteroids in movies and TV are usually brown, which I always thought was weird. Admittedly until quite recently we did not have much in the way of images of asteroids but… the moon is grey, most rocks are grey. Brown is a pretty unusual colour for rocks actually so why someone would think asteroids would be brown is beyond me. Its not even a cool colour.
Depictions of nebula in scifi is always wrong too. Nebula are so dim that they only become viisible in long exposures. Our night sky is actually full of large nebula so dim we cannot see them.
If it were as dense as those illustrations, we wouldn’t be able to see through it. It would appear as a black line against the Milky Way.
If you had a big swirling bumping mass of rocks in a tight clump in space somewhere like that (far away from any planets say), how long would it take for them to all disperse? Assume that they are all yes orbiting their star…
Here are two videos showing some asteroid orbital characteristics. Note that the asteroids are shown many times larger in proportion to Jupiter, other wise you couldn’t see them on your screen at all.
The first shows two sets of asteroid families in resonance with Jupiter. In the first halt the group mainly shown are 3:2 oribital resonance. Note how some of them have a triangular path. Some even go retrograde at the “angles” of the triangle, from Jupiter’s perspective. It’s like a cosmic version of Spirograph. The second half shows Trojans (1:1). These asteroids “orbit” their Lagrange point.
Jupiter is the blue dot on the left. The orientation is set to keep it relatively fixed. Due to it’s elliptical orbit, it wobbles a bit.
The second shows the asteroid belt starting from above and moving edge on. In this one, Jupiter is shown moving in orbit.
Note how the bulk of the belt is mostly close to Mars and not much close to Jupiter. It has really cleaned out that chunk of space.
As to “edges” of the asteroid belt and such, note how it is somewhat fuzzy but not at much as I expected.
We’ve sent numerous spacecraft through the asteroid belt into the outer solar system, like Voyager, Cassini, New Horizons, etc. Other than making sure to avoid some of the larger ones we know of, none of the flight plans of those spacecraft needed to take into account dodging asteroids while passing through, because the chances of a collision are so remote.
I don’t think they would disperse. Gravity would clump them together into a single body.
If you had a planet in an asteroid belt, would you even have an asteroid belt? That is (and my physics is weak, so please be gentle): I thought that the more massive an object was, the faster it would have to move (in the same orbit) to maintain it’s orbit. If that’s correct (and I’m not sure it is), wouldn’t a planet crash into and absorb the asteroids in relatively short order?
That is incorrect. Same orbit == same speed, no matter the mass of the orbiter.
Although if you did have a planet-like-object in the asteroid belt, it would, be definition, not be a planet until it cleared its orbit (i.e. destroyed the asteroid belt). Call it the “Ceres rule”. 
I was going to mention Ceres. It’s a big round thing, which is basically a planet. It doesn’t fit the nitpickers’ rule about having cleared its own orbit, but it’s a big round thing.
And if this weren’t the case, when two spacecraft docked together, they’d suddenly go into a different orbit.
The definition of “planet” has always involved more than bigness and roundness. There are about twenty objects known in the system that are larger than Ceres and smaller than Mercury.
Thank you, sir or ma’am. Once again, ignorance has been fought!
Just to make things clear, an object of say, Mercury’s size and mass, if suddenly introduced into the asteroid belt, would clear its orbit in short order. Short order here meaning a few million years or so (very short compared to the age of the solar system). Also note that “clear” does not mean every single asteroid would be either absorbed or ejected. The vast majority would be and that’s good enough for astronomers.
As has been mentioned, same orbit = same speed, regardless of mass. However, the more massive the focus object being orbited, the faster an orbiting object must go to maintain a given distance. So a satellite orbiting Jupiter at 100,000km (from its center) would have to go much faster than a satellite orbiting Earth at the same distance.
No, they’re not.
No, it isn’t. It’s a pretty damn common rock colour.
The moon is very variable in colour. Note that most of what you see on the moon in Apollo photos isn’t moon rock so much as moon dust. Which tends to to wash out colour variations (try looking at a handful of sand up close, sometime, then look at a beach)