0
$\begingroup$

Recently read a question regarding the temperature of the CMB & one of the comments got me thinking...

From what I understand, collisions between subatomic particles and objects out in interstellar space affect the objects energy and movement. So I have assumed that similar collisions happen between larger bodies (such as Earth/Moon/sun) and the space around them. That said, is the movement of our Earth affected or changed in any measurable way? If the Earth loses enough energy from these collisions (over a very long period of time of course) could its orbital path eventually "collapse" and get sucked in towards the Sun"?

Or is some type of conservation of momentum still in play which keeps these bodies in their correct path?

-And please if you are going to downvote my question, provide a relevant explanation for it-

$\endgroup$
1
$\begingroup$

As the Earth isn't a closed system with regard to other objects in the Solar System, including atomic particles, its momentum is affected by collisions. But if the collisions were inelastic (if the atomic particles were absorbed into elements of the crust and the atmosphere), the momentum of the atomic particles and the momentum of the Earth involved in the collision would be converted to potential energy. If enough of the Earth's momentum were converted into potential energy, eventually the Earth would lose angular momentum and the rate of spin would slow, or it would fall into the Sun. However, as mass is added to the Earth, it's momentum would grow. There would be a trade-off between the velocity component of momentum lost to potential energy, while the mass component of momentum is augmented.

Light, also, carries momentum, and light from the Sun which is converted to other forms of energy, such as growth of plants and heating of the earth and sea, converts part of Earth's momentum (the part involved with inelastic collision of light and planet) into potential energy. Light which is reflected back into space, however, is part of an elastic collision, and results in an equal amount of momentum of the Earth being redirected opposite to the light emitted from the Sun. This may drive the Earth farther away from the Sun. This is all a very slow process. For example, a flashlight left on for an hour gains 10^-5 kg*m/sec momentum of recoil from the light it emits.

This is a readable treatment of conservation of momentum: http://lightandmatter.com/html_books/lm/ch14/ch14.html

$\endgroup$
0
$\begingroup$

It does affect the Earth, but at a rate so slow that the sun will expand into a red giant before that happens.

$\endgroup$
  • $\begingroup$ That what I was thinking, so how about something smaller like the Moon or non-planetary bodies. $\endgroup$ – Greg Olsen May 6 '15 at 23:51
  • $\begingroup$ @GregOlsen even the moon is too large to be greatly affected by collisions of this sort. $\endgroup$ – Jimmy360 May 6 '15 at 23:53
  • $\begingroup$ @Jimmy360, could you provide s very a analytic expression to back this. I do not doubt the correctness of your answer, i just think a simple model would add to the quality of the answer. $\endgroup$ – rul30 May 7 '15 at 4:52

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.