# Thread: Photosynthesis Means the Earths Mass is ever increasing?

1. This is a question for whoever is out there.

Is the earths mass ever increasing? I understand that under the Second Law of Thermodynamics, the Earth is a closed system, ie it exchanges energy with its environment, but not matter.

So, my question is, if sunlight energy is constantly radiating onto the Earth, and plants transform that energy into matter, wouldn't it follow that the earth is constantly gaining mass?

This idea is also informed by something I read from the food systems writer, Michael Pollan, called "Pumpkins Leave No Holes." It was about how, if you take 50 lbs. of soil and plant a pumpkin seed in it, and lets say the pumpkin grows to 50 lbs. also. If you took everything that grew out of the seed, the salk, the leaves, the stem and the pumpkin, and you weighed the soil, it would still weigh 50 lbs.

What's more, if you ate the edible parts of the pumpkin, and composted the inedible parts, you would produce MORE soil, making this process more than sustainable. Its actually constantly growing.

Is this correct? Is the earth gaining mass? Is our gravitational pull increasing slightly because of it? Does it matter?

love,
Nick

2.

3. The only way Earth is gaining mass, is by smaller asteroid impacts (larger actually cause us to lose mass). In case of photosynthesis, the formula is , from which you can quite clearly see that there is no mass change. As for the pumpkin example, I have not read the book, but I'm quite sure increased mass comes from water that you used to grow the pumpkin, and from some of the gases in the air.

4. The mass gained by the plants in your example comes from the very air around it. Plants can for example get carbon from carbon dioxide in the air. To do the pumpkin experiment really rigorous one would have to do it in an airtight room, and weigh both the room, the air and the plant - in which case weight difference would be negligible.

5. yes, the radiation of energy to the earth causes the earth to gain mass. However, the loss of air particles in the upper atmosphere and the re-radiated energy from the earth causes it to lose mass. So it comes out roughly even in the long run, save for those asteroid and meteor impacts as stated.

The "formula" you put in actually does have heavier resultants than constituents. But, that's explainable, and accounted for. The chemical bonds cause an increase in mass that is negligible, but present, and once the bonds are broken and the molecules are changed, the energy is released, along with the mass.

6. Originally Posted by nicholasmelas
This is a question for whoever is out there.

Is the earths mass ever increasing? I understand that under the Second Law of Thermodynamics, the Earth is a closed system, ie it exchanges energy with its environment, but not matter.

So, my question is, if sunlight energy is constantly radiating onto the Earth, and plants transform that energy into matter, wouldn't it follow that the earth is constantly gaining mass?
Plants do not transform energy into matter. They use the energy of sunlight to combine carbon dioxide from the air and water into carbohydrates which they use to feed themselves and grow.

This idea is also informed by something I read from the food systems writer, Michael Pollan, called "Pumpkins Leave No Holes." It was about how, if you take 50 lbs. of soil and plant a pumpkin seed in it, and lets say the pumpkin grows to 50 lbs. also. If you took everything that grew out of the seed, the salk, the leaves, the stem and the pumpkin, and you weighed the soil, it would still weigh 50 lbs.
Most of the weight of the pumpkin is water, water which came from irrigating the soil (and outside source). Some of that irrigation water was combined with CO2 to make up the rest of the pumpkin. This is where the vast majority of the weight of the pumpkin comes from.
However, the soil will not weight exactly fifty pounds after removing the pumpkin mass. There are some essential nutrients that the soil will have given up to the pumpkin; mainly Nitrogen, Potassium and phosphorous( some plants can get their nitrogen directly from the air). The left over soil will weigh shy of 50 lbs by the amount of these elements contained in the pumpkin.

What's more, if you ate the edible parts of the pumpkin, and composted the inedible parts, you would produce MORE soil, making this process more than sustainable. Its actually constantly growing.
Composting will return those elements to the soil contained in the inedible parts, but not those in the edible parts. The new soil will have a little less of these needed elements. The cycle is not infinite. Eventually the soil will not have enough to grow any more pumpkins, andyou will have to replenish them by fertilizing the soil.
Crop rotation can help here. If you grow legumes(peas for example), these are the type of plants that get there nitrogen from the air. You can use them to return nitrogen to nitrogen depleted soil, which then allows you to plant other crops there with less fertilizing.

Of course, the elements in the edible parts will eventually return to the environment in the form of our wastes and when we die.

Is this correct? Is the earth gaining mass? Is our gravitational pull increasing slightly because of it? Does it matter?

love,
Nick
So no, the Earth is not gaining mass in this way, as no new matter is being created.

7. Originally Posted by Arcane_Mathematician
yes, the radiation of energy to the earth causes the earth to gain mass. However, the loss of air particles in the upper atmosphere and the re-radiated energy from the earth causes it to lose mass. So it comes out roughly even in the long run, save for those asteroid and meteor impacts as stated.

The "formula" you put in actually does have heavier resultants than constituents. But, that's explainable, and accounted for. The chemical bonds cause an increase in mass that is negligible, but present, and once the bonds are broken and the molecules are changed, the energy is released, along with the mass.
Man I love you, I didnt know this, thank you. Now it would be interesting to know how much this neglected mass actually is, because in the scale of the whole earth I bet it could add up to some significant value.

8. Originally Posted by nicholasmelas
This is a question for whoever is out there.

Is the earths mass ever increasing? I understand that under the Second Law of Thermodynamics, the Earth is a closed system, ie it exchanges energy with its environment, but not matter.

So, my question is, if sunlight energy is constantly radiating onto the Earth, and plants transform that energy into matter, wouldn't it follow that the earth is constantly gaining mass?

This idea is also informed by something I read from the food systems writer, Michael Pollan, called "Pumpkins Leave No Holes." It was about how, if you take 50 lbs. of soil and plant a pumpkin seed in it, and lets say the pumpkin grows to 50 lbs. also. If you took everything that grew out of the seed, the salk, the leaves, the stem and the pumpkin, and you weighed the soil, it would still weigh 50 lbs.

What's more, if you ate the edible parts of the pumpkin, and composted the inedible parts, you would produce MORE soil, making this process more than sustainable. Its actually constantly growing.

Is this correct? Is the earth gaining mass? Is our gravitational pull increasing slightly because of it? Does it matter?

love,
Nick

Well to my understanding cellular respiration also has an output of energy.