Leaving the sun

1. Dec 1, 2005

Newlaws

I have seen an article about the earth flying away from the sun due to the use of nuclear energy: the earth becomes lighter as we convert mass into energy, therefore the sun pulls less on the earth, causing the earth to fly away from the sun.
See http://www.cheap-tickets-to-games.com/polka_dot_highway/ [Broken]
Does the math work out? How fast will it the earth fly away? How much nuclear energy will we have to use before this effect will start working? What can we do to counter this?
Thanks,
--NL

Last edited by a moderator: May 2, 2017
2. Dec 1, 2005

Staff: Mentor

Actually, if you work through the math, it turns out that the mass of the extra photons that are captured in by our planet due to greenhouse gasses (hence global warming) almost exactly cancel out the mass lost in fission nuclear power plants. So the earth will stay stationary right where it is today. :rofl:

3. Dec 1, 2005

Anzas

this article is pretty much nonsense, nuclear power plants use very little amount of mass to get energy. from e=mc^2 its obvious that even a very small amount of matter produces vast amounds of energy, if anything the guy should be worrying about nasa just think about all the mass we take from the earth and launch into space :rofl:

4. Dec 1, 2005

Staff: Mentor

Yeah, but it's only the interplanetary probes that we need to worry about. Their mass gets pushed outward, so that makes the earth spiral inward toward....the....sun....

:tongue2:

5. Dec 1, 2005

Danger

We should tie a string to the next one so it can tow us back out.

6. Dec 1, 2005

Staff: Mentor

I don't see any math on the site, but sure, the idea is valid. I suspect in a few quadrillion years, there'd be a noticeable difference. But don't sweat it, you'll be dead.

7. Dec 1, 2005

daveed

a smaller force acting on a smaller mass produces the same acceleration

the earth would stay in the same place...

Last edited: Dec 1, 2005
8. Dec 1, 2005

Staff: Mentor

Heh - yeah, you're right. An orbit is an orbit.

Slow day, sorry...

9. Dec 4, 2005

Newlaws

Yes, I see it now. Here's the thought experiment I used to better understand it:

If you had two balls orbitting the sun, each close to the other, attaching one ball to the other with a small rope wouldn't mean they suddenly are attracted by the sun more due to their combined weight such that they would go toward the sun... thus the weight doesn't make a difference.

10. Dec 4, 2005

NewScientist

What if we got everybody to go to China (its big enough for the entire population) and got them to jump up and down would that make a difference to our orbit?! I really hope somebody goes and does the math on this one!!

11. Dec 4, 2005

TiBaal89

Oh but its not just those pesky nuke plants... what about coal plants! Wait... what about all combustion?!?! we're doooomed :rofl:

12. Dec 5, 2005

Newlaws

Burning stuff doesn't change total mass does it? I say explain to people that what you eat and drink all comes out -- there's no nuclear fission going on in your body.

13. Dec 5, 2005

Pengwuino

Its energy, mass changes. Someone also noted that there are photons that hit the earth and i wouldnt be surprised if they nearly cancel out the energy produced by nuclear reactors :P

14. Dec 5, 2005

Martin Rattigan

The acceleration due to gravity towards the sun would remain the same, but wouldn't the Earth have to accelerate tangentially to conserve momentum as the mass reduces?

15. Dec 5, 2005

TiBaal89

Yes, Indeed. As I type, the tremendous energy with which my fingers are striking the keys is destroying mass... how many billions of decimal places out that would be in kg or lbm I don't really know, but hey its happening. :tongue2:

16. Dec 5, 2005

Mk

Your fingers aren't destroying mass, its deforming mass.

17. Dec 6, 2005

TiBaal89

I'll admit I was mistaken in my last post. I suppose if my fingers are adding energy to the keyboard by striking it, I'm actually CREATING mass!! :rofl:

The silliness of these concepts in practical matters gets the best of me, but truly if we are to buy into these concepts of mass-energy equivalence... then it is still true regardless of how comically small these quantities are mathematically, and how wildly impossible they are to detect.

18. Dec 6, 2005

Newlaws

I don't get it. An old colleague of mine told me that if you squeeze a spring between your fingers, it gets heavier? I understand e=mc^2, but I don't think it applies in this case?

19. Dec 6, 2005

Danger

That doesn't make any sense to me. It'll get warmer, but I can't see how the mass would change.

20. Dec 7, 2005

TiBaal89

Of course it does. We never speak in these terms becuase obviously there is absolutely no purpose to do so. But I'm not aware of a "cut off" where e=mc^2 ceases to be true. If thats the case then there is a change in mass in these situations, despite the fact that it is radically small and undetectable.

That's all I'm getting at is that on some ludicrous level these things are happening. I like that spring example, thats a good one.... and no doubt true!!