B Does earth mass get heavier?

Now wait, mass can be converted to energy and it doesn't require a nuclear reaction. Every chemical reaction changes the mass of the constituents by the change in the binding energy.

However there are two reasons why this is negligible. First. The earth is in somewhat of a steady state. The chemical configuration today is not much different than yesterday. Second, and much much more importantly, the effect is minuscule. Even if you set fire to the earth and burned every bit of the surface to its lowest energy state I don't think you would change the mass significantly. Completely irrelevant, but fun to contemplate.

I believe the most significant contribution to changing the earths mass is the accretion of bits and pieces from space. Much much much more relevant than the previous ... and yet still pretty negligible. Estimates vary, but it could be 60 tons per day. That sounds like a lot, but it's 20 orders of magnitude less than the mass of the earth. In a billion years it would still only change the mass by one part in 10^8. Completely irrelevant.

Then there's the mass of our deep space probes. Now THAT is eroding the earth at an alarming rate!

 

In addition to what others have already touched on, we have to consider the second half of your question, what effect would this have on Earth's orbit. The fact is that since the Sun's mass is so much greater than the Earth's, it dominates the nature of the orbit. For example, even if we assumed that the mass of the Earth suddenly doubled, and all else(orbital speed etc.) stayed the same, the effect on the Earth's orbit would be smaller than than its present variation due to the eccentricity of its orbit.

 

Doesn't the solar energy collected by photosynthetic plants then incorporated into organic molecules add a little to the mass of Earth?

 

What we defecate is the waste left over from what we eat. What we eat comes from the mass of the Earth. In other words, what we defecate does not add to the mass of the Earth as it was always a part of the mass of the Earth. The same with the dead, everything that made up their bodies was always there as a part of the Earth's mass.

Besides, I don't think you realize just how small the total mass of living and dead animals (including humans) is compared to the mass of the Earth as a whole, We are talking about a fraction that is less than 1/1,000,000,000.

 

Shouldn't we be tackling the OP's confusion from a slightly more systemic vantage point?

Sources of mass/energy input:

• solar radiation (EMR), solar wind (particles)
• infalling comets, meteors, stray dust, gas

Sources of mass/energy output:

• heat loss (EM radiation)
• escaping atmosphere (particles)

Everything else:

• all people,
• all animals,
• all plants, fungi and bacteria,
• their breaths, their food, their defecation,
• their reproduction, their births, their deaths

are all mass neutral - they take from what is there, move it around a lot then deposit pretty much back where it came from - on Earth.

 

No, it is not hidden.
Energy's mass can be derived from E=mc²

 

Yes, Simba, but let me explain. When we die, our bodies become the grass, and the antelope eat the grass. And so we are all connected in the great Circle of Life.

 

Hey, that brings up an interesting point. That doesn't conserve momentum. Forget the earth. Say a nuclear bomb is in orbit around the sun. When the bomb explodes suddenly a significant fraction of the mass disappears. Say the explosion is spherically symmetric so the center of mass doesn't change. How is momentum conserved? It has to be, so where would it go?

 

This is a different question, and warrants its own thread so as not to derail this one.

But here's a teaser:

What makes you think it simply disappears? We're talking mass/energy conversion here, not disappearance.

 

Yes, I shouldn't have said it like that. In fact I added "is it in the momentum of the generated photons?" But erased that to avoid steering the answers. However, I really don't see in detail how the conservation comes about. Maybe I will start a new thread. Interested parties can look for it.