B Does the Earth's Mass Change Due to Biological Processes?

[Althepump]

Trees, plants grow. people eat, animals eat. Their dungs in ground everyday. People die. Does it have effect on the Earth mass? On its orbit around the sun?

 

[Doc Al]

Why would you think any of that affects the mass of the earth?

 

[mfb]

Does your food come from space?

 

[Cutter Ketch]

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 Earth's 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!

 

[mfb]

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

~150 missions to leave Earth orbit in 55 years, for a rate of a few tons per year. Add something like 10,000 tons in Earth orbit, then we have 200 tons per year, but most of that mass will fall back to Earth eventually.

The mass-energy equivalent of geothermal heat is about 10-15 tons per year.

 

[Nugatory]

Trees, plants grow. people eat, animals eat. Their dungs in ground everyday. People die. Does it have effect on the Earth mass? On its orbit around the sun?

Imagine a large spherical surface surrounding the earth. Everything (energy, space probes, gas molecules escaping the atmosphere, ...) passing outwards through that surface reduces the mass of the earth. Everything passing in through it (energy, meteors, cosmic radiation, stray space dust, ...) increases the mass of the earth. Everything that happens inside the sphere and stays inside it (growing plants, consuming food and defecating, water falling from the sky as rain and evaporating back into clouds, ...) has no effect on the mass.

In practice, all of these effects are so small that we can take the mass of the Earth to be constant without introducing significant erros into our calculations.

 

[Althepump]

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 Earth's 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!

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 Earth's 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!

Your answer: convert mass to energy may be the solution to my question.

 

[Althepump]

Imagine a large spherical surface surrounding the earth. Everything (energy, space probes, gas molecules escaping the atmosphere, ...) passing outwards through that surface reduces the mass of the earth. Everything passing in through it (energy, meteors, cosmic radiation, stray space dust, ...) increases the mass of the earth. Everything that happens inside the sphere and stays inside it (growing plants, consuming food and defecating, water falling from the sky as rain and evaporating back into clouds, ...) has no effect on the mass.

In practice, all of these effects are so small that we can take the mass of the Earth to be constant without introducing significant erros into our calculations.

Cutter Ketch's reply: mass convert to energy may be the answer. Your answer is good, but I am not happy. We are aware that we defecating everyday. It should add up. Animals,too. They are doing that since dinosaurs' days.65 million years ago. It should add up by now..significantly. People die every day.. it should be lots more dead in the ground than live ones like you and me. The probability has to be 1000 to 1. Common sense will agree with me. Don't count zombies. I think mass convert to energy is the answer. We cannot weigh energy so small.

 

[Janus]

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.

 

[rootone]

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

 

[Althepump]

Does your food come from space?

Good question. I always buy food at Shoprite. Workers may be spacemen.

 

[Althepump]

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.

Thank you for the thought.

 

[Janus]

Cutter Ketch's reply: mass convert to energy may be the answer. Your answer is good, but I am not happy. We are aware that we defecating everyday. It should add up. Animals,too. They are doing that since dinosaurs' days.65 million years ago. It should add up by now..significantly. People die every day.. it should be lots more dead in the ground than live ones like you and me. The probability has to be 1000 to 1. Common sense will agree with me. Don't count zombies. I think mass convert to energy is the answer. We cannot weigh energy so small.

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.

 

[DaveC426913]

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.

 

[Althepump]

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

Good thought. Maybe someone can help you about the energy because it's has no gravitational tendency like mass. Looks like to me that energy is just electrostatic, repelling and attracting each other in all directions although intact inside that it counterbalances virtually zero resulting miniscule in weight. Hidden.

 

[DaveC426913]

Good thought. Maybe someone can help you about the energy because it's has no gravitational tendency like mass. Looks like to me that energy is just electrostatic, repelling and attracting each other in all directions although intact inside that it counterbalances virtually zero resulting miniscule in weight. Hidden.

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

 

[jbriggs444]

Cutter Ketch's reply: mass convert to energy may be the answer. Your answer is good, but I am not happy. We are aware that we defecating everyday.

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.

 

[Cutter Ketch]

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.

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?

 

[DaveC426913]

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

But here's a teaser:

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?

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

 

[Cutter Ketch]

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.

 

[DaveC426913]

In fact I added "is it in the momentum of the generated photons?"

(Actually, in a typical nuclear explosion only a very small amount of mass gets converted to energy - on the order of a gram or so. All the rest remains particulate and expanding rapidly. Each particle carries with it a tiny amount of the original angular momentum of the unexploded device.)

 

[mfb]

I think mass convert to energy is the answer.

No it is not. Matter on Earth is in a closed cycle for all practical purposes. All feces, all dead bodies, all organic material in general is used as resource by some species, which produce other products which are used as food by other species and so on.

Atoms don't suddenly appear and they also don't suddenly disappear. There is no process where Earth would gain or lose any relevant amount of mass, and in particular there is no biological process where the mass would change at all.

 

[rootone]

...there is no biological process where the mass would change at all.

I wondered about photosynthesis though, earlier in thread.
Light ends up being incorporated into energy carrying molecules
I do know of course that no new atoms are created, but doesn't the energy contributed to making say an ATP molecule represent a small mass increase?

 

[mfb]

Not if you consider the light to be part of Earth before already.

I think we are confusing the OP by discussing incredibly tiny effects in detail while OP is still working on understanding much more basic concepts.

 

[fresh_42]

Why isn't it simply what @DaveC426913 suggested?

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)

I think the EMR part sums up to zero for it's either used by lifeforms or radiated back in space. Eventually a small amount due to global warming due to decreasing outward bound radiation. So we'll have some positive amount $S$.
Then we have negative amounts on losing atmosphere $A$ and the rockets we launch above escape velocity $R$.
Also to add is natural stony space junk, someone said $60 t$ a year, say $J$.

Thus the annual change of Earth's mass $M_t$ is $M_1 - M_0 = S + J - A - R$ and we could start to argue about the figures, esp. $S$.

 

[Janus]

Why isn't it simply what @DaveC426913 suggested?

I think the EMR part sums up to zero for it's either used by lifeforms or radiated back in space

Not quite all of it. Sometimes vegetation converts solar energy to chemical energy which is not released but remains stored. This is where our oil reserves came from; The energy we get from them is, in effect, stored solar energy. ( Of course, now that we are pulling it out of the Earth and burning it, we are releasing this energy back into the environment.)

 

[fresh_42]

Yes. $S(t)$ is probably the most difficult part of the equation. The oil example shows, that $S(t)$ (sun) isn't simply a linear function, but varies on large timescales. Unfortunately I can't remember a source, but I think that I've recently heard, that the $A(t)$ term above, i.e. the loss on atmosphere is by far the biggest cost factor - something about millions of tons a year. Since $J$ (meteors / space junk) and $R$ (rockets) are easy to compute, resp. estimate, it all comes down to the atmospheric question and the actual form of $S(t)$. In the end, the sun is the only input that keeps the system Earth from being closed.

As I've already read figures here for $J$ and $R$, does anyone know, which amount of atmosphere we (on average) annually lose?

 

[davenn]

We are aware that we defecating everyday. It should add up. Animals,too.

add up to what ?

where do you think all that excretion came from for a start ??

 

[Bystander]

"Does Earth mass get heavier?"
"Heavier" implies "weight," or force. Should we examine the implication? Given that the sun is losing mass at 1.5 million tons per second, the Earth should be losing "weight."

 

[Althepump]

Cutter Ketch,

Yesterday you brought up an interesting point. Mass convert to Energy. But this morning I ask myself " if it's true, why not the Earth convert to energy as well?

 

[jbriggs444]

Cutter Ketch,

Yesterday you brought up an interesting point. Mass convert to Energy. But this morning I ask myself " if it's true, why not the Earth convert to energy as well?

As others have said, mass-energy equivalence is a drop in the bucket -- irrelevant for this purpose.

What do you mean by "earth convert to energy"?

 

[mfb]

Mass cannot suddenly disappear. Chemical and nuclear reactions release a tiny fraction of the mass of the involved atoms as energy. Most of the possible reactions happened in the past already.

 

[davenn]

"Does Earth mass get heavier?"
"Heavier" implies "weight," or force. Should we examine the implication? Given that the sun is losing mass at 1.5 million tons per second, the Earth should be losing "weight."

what is your reasoning there ??

 

[Bystander]

what is your reasoning there ??

Less attractive force between the Earth and the sun.

 

[DaveC426913]

Less attractive force between the Earth and the sun.

Ah. I see what he did there.

The Earth's weight is determined by the Sun's gravity. Sun's mass is shrinking, so Earth's weight is shrinking

 

[Janus]

Ah. I see what he did there.

The Earth's weight is determined by the Sun's gravity. Sun's mass is shrinking, so Earth's weight is shrinking

But since the Earth is following a free-fall trajectory, it is technically weightless.

 

[Bystander]

a free-fall trajectory,

An expanding/growing free-fall trajectory; i.e., the force exerted by the sun is decreasing, so, technically less than weightless.

 

[Cutter Ketch]

An expanding/growing free-fall trajectory; i.e., the force exerted by the sun is decreasing, so, technically less than weightless.

Oohhh! I like that. It's drifting up. It must be less than weightless! Ok, I don't think that's going in the textbooks anytime soon, but it's funny.

 

[davenn]

Less attractive force between the Earth and the sun.

The Earth's weight is determined by the Sun's gravity. Sun's mass is shrinking, so Earth's weight is shrinking

That mite affect the weight of the Earth but it doesn't affect the mass of the earth

and since the OP is talking about the MASS of the Earth ... it's weight in any gravity field is irrelevant
particularly in an orbit

hence Janus's response

But since the Earth is following a free-fall trajectory, it is technically weightless.

 

[Chadi B Ghaith]

As per my knowledge, having more people or trees doesn't add any mass to the planet. Humans and things are done with the matter that is already on the planet. It's just been transformed.