I’ve been tooling around with a neat program called “Universe Sandbox”. It simulates all types of things in space and lets you alter the properties of the objects.
For example you can double the mass of the sun and see how it effects the orbits of the planets. You can drop Neptune in orbit around Saturn and watch it ruin the rings.
One thing I noticed very quickly is it’s HARD to get to objects to collide. I made the earth the size of the sun and watched the solar system fall apart. Planets would be sucked towards the new super earth, but at the last minute they would sharply veer away very quickly and get ejected from the system. Then after the smaller planets got ejected, the super earth and the sun (now the same mass) settle into a strange orbit that seems stable, in that it repeats over and over.
I’m not asking for any complicated math or in depth explanation. More just a verification of does this sounds accurate, or would there be more collisions?
Also, if this is true, I guess the theory of the planet colliding with Earth to make the moon would have been an absolute one in a million shot huh?
P.S: Here’s a video I found of the scenario I mentioned above.
Space is very large, and objects–even planets–are comparatively small. However, given millions of years of iterations, collisions are inevitable, something which we should be very concerned about, as collision with even a relatively minor celestial object–say, a nickel-iron asteroid 100m in diameter–would do massive regional damage, and impact by an object greater than 1 km in diameter could well spell destruction for modern civilization as we know it.
Calculations for planetary fly-by trajectories such as that for the Voyager or Cassini-Huygens mission are calculated to a degree of precision that challenges even modern scientific calculation codes. Of course, fly-by trajectories are intended to (slightly) miss, rather than intercept a planet, but the degree of difficulty is roughly the same.
In the scenario you describe, the Earth suddenly becomes larger, more massive and more gravitationally attractive - so all the other objects in the system experience a distinct tug directly toward Earth.
However, they still have their own orbital velocities, so although there is a force vector pulling them directly at the Earth, there is also their own tendency to carry on doing what they were doing before - these two components add up to a new vector that *isn’t * aiming directly at the Earth.
Statistically it may be a very rare event, but one needs only to look at the moon’s many craters to see that it happens - given enough time, it looks like it happens alot
There’s also Lake Manicouagan, in Quebec. The lake is directly north of Maine and is easily spotted on maps. It is half the size of Delaware and is the earth’s sixth largest confirmed impact crater according to rim-to-rim diameter.
To get a rough qualitative feel for how rare collisions are: Get out a telescope, and point it at a random spot in the sky. Look through it, right at the spot where the crosshairs cross. Is that spot on a planet? The odds of hitting the surface of a planet using your telescope are comparable to those of hitting a planet using an impactor.
Those are collisions of fairly small bodies though - collisions between two planet-sized bodies are rarer, because:
[ul]
[li]There aren’t so many of them to begin with[/li][*]The orbital motion of a planet is harder to perturb than that of a small asteroid - tug on a rock, it comes more or less directly here - but tug on a planet and it kind of carries on regardless.[/ul]
What about the fact that a lot of the stuff in orbit around our solar system is roughly on a plane, though? Certainly that has something to do with increasing the odds.
Wow, ecliptic. That’s what it’s called? Roughly how “thick” is the ecliptic, just out of curiosity? If that doesn’t make sense I’ll think of another way of phrasing it.
I wouldn’t say the the ecliptic itself has a thickness, it is a plane based on our orbit. But these are the orbital inclinations of the other planets relative to it, so the ‘band’ of sky where we might expect to see a planet is rather narrow.
You can also go to http://www.heavens-above.com/
Click on “whole sky chart”. Play with the time if necessary to make sure some planets/moon/sun are visible. Check the box labeled “ecliptic plane” and you’ll see that all the planets line up very nicely.
One other thing to think about: Start with an small object (like the earth) that is far away from a more massive object (like the sun) with vacuum otherwise. “Arrange” that small object to move so that is very close to the large object. In doing so, the small object with lose a lot of gravitational potential energy, and with nowhere else to put that energy it has to gain a lot of kinetic energy.
Since the small object has a lot of kinetic energy, it has to be going really fast, and if its now-large velocity vector is not pointed right at the large object it is going to miss it. “Whipping around” is really the more common thing in that case, unless there is a third body to suck up some of the excess energy (and get ejected).
In real life we have so many places to dump excess energy (physical deformation, heat, &c) that we don’t realize how hard it is to stick things together when there’s a strictly fixed amount of kinetic energy plus potential energy and you don’t get to “cheat” at conservation of energy.
Where, by “real life”, you mean “familiar life”, i.e., life on the surface of a planet with an atmosphere. The orbits of the planets are just as “real” as more familiar things, though.
I’m sure that I’ve seen shows on Discovery, etc. that say even when two galaxies “collide” it is unlikely that there will be any actual physical contact between stars or planets. Space is mostly space.
When I was a kid, I hit the one between Mars and Jupiter and broke it. I put the pieces back on the shelf and quitely walked away before management noticed and made me pay for it.
