How does Jupiter protect the Earth from collision with space rocks?

[Owen Ransen]

TL;DR

I've read that Jupiter protects the Earth from collision with large rocks, but could it not just as well cause collisions?

I read (in "The View From The Center") that Jupiter protects the Earth from collision with large space rocks, asteroids, etc.

What I can't get out of my mind is that could it also cause collisions. A large rock (initially not heading for Earth) could be put on a different path by Jupiter's gravity and end up heading for Earth.

So, on balance, is it true that it would cause less collisions than it would help us avoid?

 

[sophiecentaur]

What I can't get out of my mind is that could it also cause collisions.

It's a matter of statistics.
There will be occasions when a particular rock could be deflected and guided straight at the Earth by going near to Jupiter but again, some could be deflected away. The fact that there are a vast number of asteroids in Trojan Orbits around Jupiter's orbit means that some of the rocks that could have been heading our way will get gathered into orbits of similar radii to Jupiter. Jupiter will have biassed the statistics away from Earth collisions. The action of large masses on dust and rocks tends to 'shepherd' the small bits into unlikely looking orbits - Saturn's rings are thought to be sustained by the mutual action of the small particles and the shepherding moons.
It helps that the majority of the stuff in the Solar System tends to be laying quite close to the plane of the ecliptic. Jupiter may have virtually no effect on objects arriving at other angles.

 

[davenn]

Summary:: I've read that Jupiter protects the Earth from collision with large rocks, but could it not just as well cause collisions?

I read (in "The View From The Center") that Jupiter protects the Earth from collision with large space rocks, asteroids, etc.……………..

Not really, consider that most of the meteorites on Earth have come from the Asteroid Belt which is inside
the orbit of Jupiter, there is no real way for Jupiter to stop them.
It's gravity effect on the asteroids is more likely to send them our way.

Also consider that, in the big scheme of things, Jupiter is tiny and its gravity is going to have little effect on
objects not within its immediate sphere of influenceDave