Physics/ AstroPhysics Question

[robm3]

Okay, my CEO and I are having a stupid debate....
If we sent all of Earth's waste plutonium into the sun, the Earth would eventually become lighter in mass.
Now if the Earth is lighter in mass, would the Sun's gravity pull us in closer or would we drift further away?

I think it would pull us in, he thinks drift away....seeing as he's the CEO, he's right...but I would just like to know.

[Eric Mc]

No change.

[satchbot]

The weight is negligible so irrelevant. The Earth is slowing down so will be getting closer to the Sun but we will be eaten by the Sun's growth before we are slow enough to be pulled in.

[Established 1984]

You're right it would pull us into a closer orbit. Somewhere I have the sums that would prove it/provide better explaination but I can't remember where

[Parrot of Doom]

In real life nothing would change, as the transfer of mass is so small as to be irrelevant.

Theoretically, the orbits of all bodies in the solar system would be affected to a small degree, but the earth will never tumble into the sun, or fly away on a tangent of its own.

[robm3]

The initial part is kinda irrelevant now, the question is really, does a lighter Earth get pulled into the sun or drift further away.

[robm3]

Established 1984 said:

You're right it would pull us into a closer orbit. Somewhere I have the sums that would prove it/provide better explaination but I can't remember where

Brilliant if you could find them, yes it would kill my career but I'd be right, right goddamit!

[satchbot]

Depends on the speed it's travelling at/is there a sudden loss of mass.

[Geoff82]

Call me crazy but I think there would be no change for this reason:

The gravitational force an object exerts is directly proportional to its mass. If you transfer the mass of the plutonium from the Earth to the Sun then the earth is lighter and exerts a smaller gravitational force (relatively speaking it would make no difference)

The sun equally would exert a slightly large gravitational force (Again of negligible size)

As the sun and the earth are still the same distance apart the gravitational pull experienced by the earth would not change.

Any takers?

In practical terms though it would make no difference as the change in mass for both bodies is minimal

Edited by Geoff82 on Friday 5th December 17:34

[rhinochopig]

Geoff82 said:

Call me crazy but I think there would be no change for this reason:

The gravitational force an object exerts is directly proportional to its mass. If you transfer the mass of the plutonium from the Earth to the Sun then the earth is lighter and exerts a smaller gravitational force (relatively speaking it would make no difference)

The sun equally would exert a slightly large gravitational force (Again of negligible size)

As the sun and the earth are still the same distance apart the gravitational pull experienced by the earth would not change.

Any takers?

Agreed. That's what I was going to post, but you saved me the job.

[johnfm]

no such thing as 'gravitational pull'.

How could the force of 'gravity' act instantaneously over 93 million miles? Faster than the light coming from the sun?

It is curvature of space-time.

Newton was close, but no cigar.

Albert did the maths.

I expect Albert's maths would suggest no change.

[rhinochopig]

johnfm said:

How could the force of 'gravity' act instantaneously over 93 million miles? Faster than the light coming from the sun?

Quite easily, my wife can tell instantly from anywhere in the house when I'm watching pornography. Why should gravity be any different?

Edited by rhinochopig on Friday 5th December 17:43

[johnfm]

rhinochopig said:

johnfm said:

How could the force of 'gravity' act instantaneously over 93 million miles? Faster than the light coming from the sun?

Quite easily, my wife can tell instantly from anywhere in the house when I'm watching pornography. Why should gravity be any different?

Edited by rhinochopig on Friday 5th December 17:43

have a

[kambites]

Depends on whether it was sent as a projectile or under power.

[rhinochopig]

kambites said:

Depends on whether it was sent as a projectile or under power.

You going down the equal and opposite reaction route? Wouldn't matter.

[s2art]

Depend how the mass is transferred. If it was magically moved, taking its momentum with it then the Sun would be a tiny bit more massive and vice versa for the Earth, as the formula for gravitational attraction is proportional to M1*M2 divided by distance squared and the inertial force of the Earths orbit is proportional to omega squared times the mass, it all seems to cancel out nearly but not quite. So the Earth moves slightly closer.

[johnfm]

s2art said:

Depend how the mass is transferred. If it was magically moved, taking its momentum with it then the Sun would be a tiny bit more massive and vice versa for the Earth, as the formula for gravitational attraction is proportional to M1*M2 divided by distance squared and the inertial force of the Earths orbit is proportional to omega squared times the mass, it all seems to cancel out nearly but not quite. So the Earth moves slightly closer.

We've already discounted 'the formula'.

Gravity doesn't exist. Postulated by Einstein. Proved by Eddington.

[s2art]

johnfm said:

s2art said:

Depend how the mass is transferred. If it was magically moved, taking its momentum with it then the Sun would be a tiny bit more massive and vice versa for the Earth, as the formula for gravitational attraction is proportional to M1*M2 divided by distance squared and the inertial force of the Earths orbit is proportional to omega squared times the mass, it all seems to cancel out nearly but not quite. So the Earth moves slightly closer.

We've already discounted 'the formula'.

Gravity doesn't exist. Postulated by Einstein. Proved by Eddington.

Irrelevant. You could use GR if you wanted to, you would get the same results unless relativistic speeds are involved. the classical formula is fine for this purpose.

BTW Gravity certainly does exist. Otherwise we would all be in freefall.

Edited by s2art on Friday 5th December 18:04

[kartmaster4213]

s2art said:

Depend how the mass is transferred. If it was magically moved, taking its momentum with it then the Sun would be a tiny bit more massive and vice versa for the Earth, as the formula for gravitational attraction is proportional to M1*M2 divided by distance squared and the inertial force of the Earths orbit is proportional to omega squared times the mass, it all seems to cancel out nearly but not quite. So the Earth moves slightly closer.

just about to post that so good job i didn't haha

the formula for the force of gravity is -GMm / R(squared) where G is the universal gravitational constant, M is the mass of the sun, m is the mass of the earth and R is the radius of the orbit.

The earth would move slightly closer but as the mass of the earth is roughly 6.4x10^24kg (that is 6.4 with twenty four 0's after it) the distance would be negligible.

[carmonk]

I don't understand the question. Is plutonium mentioned because of it's special qualities or are we just treating it as a mass?

If we're treating it as a mass alone then the answer is, nothing would happen. If we removed the plutonium we have access to from Earth I suspect that weight defecit would be made up within minutes or hours by the weight of meteorite dust falling from the atmosphere. In other words, it's insignificant.

If a significant mass removal occurred, for whatever reason, then the Earth would drift away from the sun.

Gravitational Force = (Gravitational Constant * Mass 1 * Mass 2) / the square of the distance

(EDIT to explain that the Pu mass would likely be transferred to energy in the sun and therefore the mass defecit would continue to exist)

Edited by carmonk on Friday 5th December 18:19