asteroid

[top_driver]

if the asteroid that missed the planet at 200,00 miles or whatever it was, since it's on the belt, and cycling the system plus the gravity of earth, doesnt that mean it will be going off track and next time it passes it will be closer, or is it one that has left the belt and going straight on

[David H]

Comets appear to have regular and reliable paths that continue many thousands of years. I think you mean Elenin which left on October the 16th and was far too far away to cause us any concern. http://www.jpl.nasa.g....cfm?release=2011-135

[David H]

Ah, that was such a little one it only just got on the news after I posted, it's the same distance away as the moon, so although closer than Elenin still the same orbital rule will apply and a very long way from any danger.

[beso]

David H has answered incorrectly.

The orbit of all bodies is constantly under the influence of all other bodies via Gravitation. The closer the other body the greater the influence according to an inverse square law. Double the distance and the influence is reduced to one quarter.

Comets and asteroids that don't pass close to planets do maintain a fairly regular orbit as David has indicated.

However when something passes close to a planet the orbit can be extremely perturbed. Tiny variations in the distance at which it passes have a large effect. Only after the object has passed can the new orbit be determined and the potential for future interactions with the Earth calculated.

The new orbit might be on a collision course or it might be flung out to a new one well away from us.

These bodies that encounter the Earth can be on a very elliptical path where they just happen to come close to us occasionally as they intersect with our orbit. This is why Halley's comet is better some passes than others.

Other asteroids are on a very similar orbit to Earth. These are a much bigger problem because the potential to encounter them is much larger. Sometimes, despite being more elliptical than ours their motion is in a harmonic relationship with the Earth's orbit and they return regularly.

[heathfield]

The asteroid's track has been monitored closely and predictions of its future track made by taking into account the gravitational influence of other bodies in the solar system. It is predicted that its track will miss the Earth for at least the next few hundred years.

http://www.bbc.co.uk/...-environment-15572634

[Old_Geezer]

But I'm expecting advances in medical science to keep me going for at least 500 years from now !

[top_driver]

thats great for us, but not for the next few generations, but by then there may be a bigger threat, and for it all to collapse millions of years time when the Andromeda collides with ours creating a super nova and with 2 scenarios

[Gusssss]

You are right that it is thought we will collide with the Andromeda galaxy, but it will not necessarily mean more supernovae, which are deaths of old stars, in fact it will probably cause more star births.

If you imagine the Sun as a grain of sand, on the same scale the nearest star, Proxima Centauri, would be about 15 kilometres away. That is the amount of 'empty' space in the galaxy. So the stars themselves will be unlikely to hit each other.

Not quite empty because there is a lot of gas and dust which we see as the great range of nebulae, and when galaxies collide this gets compacted resulting in the creation of more stars.

On the other hand, we think most if not all galaxies have at their centre a "supermassive black hole", and depending on which side of our galaxy we happen to be on at the time of the collision, our solar system might or might not get swallowed by it.

But this will not happen for about 5 billion more years, if we don't miss altogether.

[top_driver]

a supernova is also caused by the collision of infinite mass, it will create a bigger galaxy, if anyone human lives, will also destroy that galaxy, haha