# a question

#### eddymrsci

##### Beware of the dark side
Registered Senior Member
so according to classical mechanics, when you jump off say a desk, the Earth actually comes back at you, so (I heard this somewhere) if everybody in China or India or any other populous nation jumped at the same time, it would actually pull Earth out of its orbit.

Myth or fact?
thanks

eddymrsci said:
so according to classical mechanics, when you jump off say a desk, the Earth actually comes back at you, so (I heard this somewhere) if everybody in China or India or any other populous nation jumped at the same time, it would actually pull Earth out of its orbit.

Myth or fact?
thanks
The orbit would likely restabilize after some weeks or months or years, but the plate techtonics could take a hit from which our planet might never recover.

Who knows

hehe its Pulled??? maybe after the initial hit... shocks back?
I dont know what im talking about

I dont think it would be enough to cause a very big change.

eddymrsci said:
Myth or fact?
Definitely Myth.
Think about the centre of mass of the Earth, and all living beings. This is in a stable orbit around the sun. When any number of people jump from the surface of the earth, no external forces are applied, and so the CoM is unaffected. However, if you are talking about the rotation of the Earth, that can be perturbed - there's a centrifuge in Cambridge,UK that accelerates a 1 ton mass to about 100g, which produces a measurable perturbation.

geodesic said:
.. the rotation of the Earth, that can be perturbed - there's a centrifuge in Cambridge,UK that accelerates a 1 ton mass to about 100g, which produces a measurable perturbation.
Well please ask them to... CEASE AND DESIST!

geodesic said:
Definitely Myth.
Think about the centre of mass of the Earth, and all living beings. This is in a stable orbit around the sun. When any number of people jump from the surface of the earth, no external forces are applied, and so the CoM is unaffected. However, if you are talking about the rotation of the Earth, that can be perturbed - there's a centrifuge in Cambridge,UK that accelerates a 1 ton mass to about 100g, which produces a measurable perturbation.

A measurable perturbation meaning exactly what, the rotational velocity of the surface?
Thank you for the post.

Geistkiesel.

Conservation of momentum says that everybody on Earth jumping at once would have absolutely no effect on the Earth's orbit.

James R said:
Conservation of momentum says that everybody on Earth jumping at once would have absolutely no effect on the Earth's orbit.
You're probably thinking about a group jump into the air and right back. The original post dealt with jumping off a desk. If everyone gradually ascended to some platform then later, all simultaneously jumped off their perches... uh.