Saturday, March 26, 2022

I Worry That Science is No Longer Being Taught

Instapundit linked to this Science Alert article about how the data we are creating is changing the mass of the Earth. Reading the comments scares me.  Instapundit's readers would be I expect smarter and better educated than most.  Yet a number of these people do not know conservation of mass.  Yes mass can be converted to energy but energy to mass is quite a bit harder.  Mass seldom converts to energy; chemical bond energy is released as heat but that is converting chemical energy to heat energy.

One sad comment observed to solar panels are converting electrons.  Another thought photosynthesis was converting light into mass. Neither seems to realize light causes movement of electrons in existing materials: selenium for photovoltaic cells and chemical bonds in plants.  Did no take chemistry or biology in high school?

Interesting question: how much mass is incoming?  5200 metric tons a year.

Wow!  What I learned in chemistry, that conservation of mass applied everywhere except fission and fusion, appears to be incorrect.


  1. Clayton, the mass of the earth is constancy changing. Some by the slow loss of atmosphere to space. Then there is the Constance bombardment of earth by asteroids.

    1. Agreed. More inputs than outputs. We lose hydrogen (photolysis of water vapor) and helium, but I am sure incoming meteor dust masses more.

  2. And the author of that article is a PhD in Physics at a university in England...


  3. It's absolutely true that photosynthesis does indeed convert energy to mass - sure the amount is teeny tiny, but when light energy is stored as "chemical potential energy" by the plant, it really is stored as mass because Einstein tells us that *all* energy is "massive" in the sense of curving spacetime gravitationally. You're right that light causes movement of electrons, but it's a basic principle of special relativity that a moving object has a greater mass than a stationary object does. Again, the effects are tiny, but the mass *must* increase when energy is stored or you end up violating conservation of energy.

    There's a decent explanation of how mass is always changed in a chemical reaction that releases or absorbs heat here:

  4. Another way of looking at how photosynthesis converts light to mass - consider the analogy to nuclear physics.

    A proton has a mass of about 1.007 amu and a neutron has a mass of about 1.009 amu. Put together six protons and six neutrons and you end up with a carbon nucleus with a mass of exactly 12.000 amu, considerably less than the sum of its parts. That difference is called a "mass defect" by physicists. You end up absorbing an amount of energy equal to that mass defect divided by c-squared if you split the nucleus into its constituents, or releasing that amount of energy it if you form the nucleus from its constituent nuclei (i.e., through nuclear fusion), even though none of those constituents are created or destroyed. Total mass-energy is conserved, so any addition or subtraction of energy must necessarily reduce or increase the mass, respectively.

    This conservation of mass-energy is *exactly* the same for chemical reactions as it is for nuclear reactions, as it must be considering it's a fundamental law of the universe. Any energy absorbed in a chemical reaction is converted to mass, and any energy released subtracts from the mass, even though no particles are created or destroyed, just like in a nuclear reaction. We just ignore the mass defect in chemical reactions because it's so tiny as to be immeasurable compared to the mass of an atom. But yes, in photosynthesis the absorbed energy from sunlight is indeed stored as mass.

  5. Everything else that I can find says that energy rearranges existing mass and the energy input can cause the molecules to change energy state, but the mass does not change. If light increased mass, there would be quite dramatic changes in the Earth's mass from side to side during each day. That is a LOT of energy.

  6. I gave you a link above from a physicist at Texas A&M discussing how mass changes. I'm also a physicist myself, and we were taught very early on in learning relativity that if you, for example, burned a piece of wood and were able to capture all physical residue from that burning and weigh it very carefully the total mass would be reduced by the energy released during the burning divided by c-squared.

    Here's another explanation from a layperson's perspective:

    Yet another from the American Chemical Society:
    "Nevertheless, when a chemical reaction emits energy to its surroundings, its reactants lose an equivalent quantity of mass in the process."

    You can't talk about "energy input" without talking about changes in mass - if energy is put in, then where does it go? How could it be that different conservation laws apply to chemical reactions than apply to nuclear reactions? If the internal molecules or electrons are in a "higher energy state", then the system is more massive by mass-energy equivalence - what else does "higher energy state" mean to you?

    As for your solar energy point, the earth receives a power input of about 173 petawatts from the sun. If I'm working my math correctly, that's a mass equivalent of about 2 kilograms per second. Sounds like a lot! But that's spread over the whole earth. Compare that to the influx of cosmic dust, which is about 200 tonnes per day, or more 2000 kilograms per second, and its not very much.

  7. Here's a good reference explaining the mass defect in both nuclear and molecular bonding:

    Quoting the summary:
    "The mass of a stable nucleus is less than the sum of its parts by Δm = E/c^2, where E is the binding energy. Similarly, the mass of a stable atom or molecule is less than the sum of its parts by Δm = E/c^2, where E is the binding energy. The mass defect is evident in nuclear reactions when the masses are measured to several significant figures. The strong force in the nucleus is much larger than the electric force in atoms and molecules. Consequently, the mass defect in atomic and molecular calculations is much smaller and is usually neglected. The difference is quantitative, however, not qualitative. Apart from their strength, there is nothing special about the nuclear forces with regard to the mass defect."

    1. I confess to being surprised. When we learned chemistry at USC, conservation of mass had only one exception: fission and fusion.

    2. It would be a much weirder universe if fusion/fission were a one-off exception to an otherwise universal conservation law rather than conservation of mass-energy being the true conservation law that applies in all cases.

      According to relativity, a mass deficit exists in all bound systems from the quarks inside a nucleon all the way up to stars in a galaxy - the mass deficit is what binding energy actually *is* [1]. Pick up an apple off the table and you've just increased the total mass of the apple+earth system by putting energy into it. In Newtonian physics you talk about "increasing the potential energy" of the apple by moving it against gravity, but "potential energy" isn't a thing you can hook up to a voltmeter and measure - instead it's a decrease of the mass deficit and if you had a sensitive enough way to measure the mass of the apple+earth, you could actually measure it.

      Fission/fusion isn't an exception to conservation of mass - it's more like the one real-world case where you actually have to keep track of the mass deficit to reproduce a reasonably precise measurement. Similarly, space-time is *always* curved by gravity according to Einstein, but you can ignore that for almost all purposes and pretend that you're in flat space with Newtonian gravity unless you're dealing with the physics of black holes or predicting the precession of Mercury to five significant figures or something.


  8. I did finally click through to the actual paper written by Vopson (the physicist in question). I don't know what kind of publication "Science Alert" is, but their summary of the paper is just wrong, though they did at least link to it at the bottom of their article.

    The part from Science Alert that Instapundit quoted: "In fact, in 350 years, some experts predict the weight of our digital bits could outweigh all the atoms on Earth."

    From the actual paper in AIP Advances: "it has been estimated that at the current digital information production growth rate, ∼350 years from now we will create more digital bits than all atoms on Earth."

    Those are wildly different claims, especially since Vopson calculates that the "mass of a digital bit" is a small fraction of the mass of an electron. The article also doesn't mention "changing the mass of the Earth" even once, just the idea that storing a digital bit would change the mass of the storage medium - that mass-energy could easily come from terrestrial sources.

    If I were Instapundit, I would not rely on Science Alert to alert me about science.