5 ms·

A pithier way to introduce this topic: the first law of thermodynamics, a.k.a. the law of conservation of energy, is that energy cannot be created nor destroyed

by lisper 3y ago

A pithier way to introduce this topic: the first law of thermodynamics, a.k.a. the law of conservation of energy, is that energy cannot be created nor destroyed, only transformed from one form to another. In light of this, how can there ever be a shortage of energy? [Note that this is intended to be a rhetorical question advanced for the purposes of pedagogy. If you find yourself wanting to post an answer, you have missed the point.]

sghiassy 3y ago
Usable energy is different than total energy. If energy isn’t concentrated (say something like gasoline) it’s not usable
dekken_ 3y ago
> how can there ever be a shortage of energy I think it's not so much a shortage of energy, but that there thermodynamic equilibrium and thus no available energy to do anything. I don't think this will ever happen tho, it's pretty clear to me that making energy more dense is a universal process.
- sghiassy 3y ago
  Not really - look up “heat death” of the universe.
  - jjaken 3y ago
    Heat death doesn’t mean “no heat” or that energy has depleted. It just means that energy is fully dispersed. All kg the hear exists, it’s just that no one place has any more than anywhere else, and so there is no longer any transfer of energy.
    - A_D_E_P_T 3y ago
      > so there is no longer any transfer of energy. Ah, but there is. The Second Law is a statistical law, not an absolute law. On long enough timescales, low-probability fluctuations in local entropy will allow for energy transfer. These fluctuations will also allow for the formation of structures. (Boltzmann himself was of the opinion that the low-entropy universe emerged from a higher-entropy background state. And indeed there's nothing in physics to rule out the emergence of Boltzmann Brains and even Boltzmann Galaxies from homogeneous and maximally entropic universes in "heat death." This is a philosophical problem of the highest order, because it implies that we're not necessarily going from "less likely to more likely states" as the video implies, but rather from a relatively deterministic state to a probabilistic state.)
      - jjaken 3y ago
        Oh interesting, I didn’t know that
  - credit_guy 3y ago
    The "heat death" of the universe is a concept that deserves to die. The second principle of thermodynamics is true only if you ignore gravity. In the presence of gravity, systems tend to go towards lower entropy, just see how a planetary system can form out of a gas cloud.
    - consilient 3y ago
      > In the presence of gravity, systems tend to go towards lower entropy, just see how a planetary system can form out of a gas cloud. This isn't correct: the entropy (and energy) of the gas cloud goes decreases as it collapses, but the entropy of its surroundings increases faster as it radiates.
      - credit_guy 3y ago
        Is that a fact? Or just a hypothetical way that could save the second principle?
        consilient 3y ago
        It's a fact. See for instance https://arxiv.org/pdf/0907.0659.pdf https://arxiv.org/pdf/0907.0659.pdf
        credit_guy 3y ago
        It's more like an opinion. Of one particular guy who has a Ph.D. in Physics. But there are many, and there is no consensus overall. Here's the relevant quote from wikipedia [1] Recent work has cast some doubt on the heat death hypothesis and the applicability of any simple thermodynamic model to the universe in general. Although entropy does increase in the model of an expanding universe, the maximum possible entropy rises much more rapidly, moving the universe further from the heat death with time, not closer. This results in an "entropy gap" pushing the system further away from the posited heat death equilibrium. Other complicating factors, such as the energy density of the vacuum and macroscopic quantum effects, are difficult to reconcile with thermodynamical models, making any predictions of large-scale thermodynamics extremely difficult. [1] https://en.wikipedia.org/wiki/Entropy#Cosmology https://en.wikipedia.org/wiki/Entropy#Cosmology
uoaei 3y ago
Energy is actually a red herring -- what's relevant here is work. Useful work, aka information, is work that can be employed in dynamics vis a vis processing. Useless work, aka heat, is the devil's share of the energy expenditure which is lost as entropy when undergoing a process.
dahart 3y ago
Why is this pithier than the video? I’m not entirely sure I see added pedagogical value. Asking the rhetorical question how can there be a shortage of energy sounds a little like someone sort-of intentionally misunderstanding what that phrase “energy shortage” means in any practical economic context. “Energy shortage” is an economics phrase, not a physics phrase. The first law of thermodynamics doesn’t suggest there can’t be energy shortages on earth, because the phrase “energy shortage” is not used to suggest a loss of energy to the universe, energy shortages are all about not having enough specific forms of energy in specific places at specific times [1], and it’s no surprise that we can’t capture dissipated heat, or that a local power system has a maximum limit at any given time, for example. Something similar could perhaps be said for the video’s approach; “what do we get from the sun?” is an ambiguous question, not necessarily a fair setup to ask a lay person when you have entropy in mind as the answer. We do get energy from the sun, that is a correct answer, and we use some of it before it goes away. But, there is the nice a-ha that all the energy from the sun eventually leaves the earth, right? [1] “An energy crisis or energy shortage is any significant bottleneck in the supply of energy resources to an economy.“ https://en.wikipedia.org/wiki/Energy_crisis https://en.wikipedia.org/wiki/Energy_crisis
- JumpCrisscross 3y ago
  It’s pithy, but in the way of word play. Energy, colloquially, means useful energy. The question collides the conventional and technical definitions to create the illusion of profundity.
  - lisper 3y ago
    Pithy != profound. The intent was to get people to think about the fact that the word "energy" means different things in different contexts, and that the thing that actually has value is not energy but the absense of entropy.
    - JumpCrisscross 3y ago
      > intent was to get people to think about the fact that the word "energy" means different things But the question posed is weaker at prompting that than the sequence of questions posed by the video. It's a strange response that doesn't add to the discussion.

by lisper 3y ago

sghiassy 3y ago

Usable energy is different than total energy. If energy isn’t concentrated (say something like gasoline) it’s not usable

dekken_ 3y ago

> how can there ever be a shortage of energy I think it's not so much a shortage of energy, but that there thermodynamic equilibrium and thus no available energy to do anything. I don't think this will ever happen tho, it's pretty clear to me that making energy more dense is a universal process.

sghiassy 3y ago
Not really - look up “heat death” of the universe.
- jjaken 3y ago
  Heat death doesn’t mean “no heat” or that energy has depleted. It just means that energy is fully dispersed. All kg the hear exists, it’s just that no one place has any more than anywhere else, and so there is no longer any transfer of energy.
  - A_D_E_P_T 3y ago
    > so there is no longer any transfer of energy. Ah, but there is. The Second Law is a statistical law, not an absolute law. On long enough timescales, low-probability fluctuations in local entropy will allow for energy transfer. These fluctuations will also allow for the formation of structures. (Boltzmann himself was of the opinion that the low-entropy universe emerged from a higher-entropy background state. And indeed there's nothing in physics to rule out the emergence of Boltzmann Brains and even Boltzmann Galaxies from homogeneous and maximally entropic universes in "heat death." This is a philosophical problem of the highest order, because it implies that we're not necessarily going from "less likely to more likely states" as the video implies, but rather from a relatively deterministic state to a probabilistic state.)
    - jjaken 3y ago
      Oh interesting, I didn’t know that
- credit_guy 3y ago
  The "heat death" of the universe is a concept that deserves to die. The second principle of thermodynamics is true only if you ignore gravity. In the presence of gravity, systems tend to go towards lower entropy, just see how a planetary system can form out of a gas cloud.
  - consilient 3y ago
    > In the presence of gravity, systems tend to go towards lower entropy, just see how a planetary system can form out of a gas cloud. This isn't correct: the entropy (and energy) of the gas cloud goes decreases as it collapses, but the entropy of its surroundings increases faster as it radiates.
    - credit_guy 3y ago
      Is that a fact? Or just a hypothetical way that could save the second principle?
      - consilient 3y ago
        It's a fact. See for instance https://arxiv.org/pdf/0907.0659.pdf https://arxiv.org/pdf/0907.0659.pdf
        credit_guy 3y ago
        It's more like an opinion. Of one particular guy who has a Ph.D. in Physics. But there are many, and there is no consensus overall. Here's the relevant quote from wikipedia [1] Recent work has cast some doubt on the heat death hypothesis and the applicability of any simple thermodynamic model to the universe in general. Although entropy does increase in the model of an expanding universe, the maximum possible entropy rises much more rapidly, moving the universe further from the heat death with time, not closer. This results in an "entropy gap" pushing the system further away from the posited heat death equilibrium. Other complicating factors, such as the energy density of the vacuum and macroscopic quantum effects, are difficult to reconcile with thermodynamical models, making any predictions of large-scale thermodynamics extremely difficult. [1] https://en.wikipedia.org/wiki/Entropy#Cosmology https://en.wikipedia.org/wiki/Entropy#Cosmology

uoaei 3y ago

Energy is actually a red herring -- what's relevant here is work. Useful work, aka information, is work that can be employed in dynamics vis a vis processing. Useless work, aka heat, is the devil's share of the energy expenditure which is lost as entropy when undergoing a process.

dahart 3y ago

Why is this pithier than the video? I’m not entirely sure I see added pedagogical value. Asking the rhetorical question how can there be a shortage of energy sounds a little like someone sort-of intentionally misunderstanding what that phrase “energy shortage” means in any practical economic context. “Energy shortage” is an economics phrase, not a physics phrase. The first law of thermodynamics doesn’t suggest there can’t be energy shortages on earth, because the phrase “energy shortage” is not used to suggest a loss of energy to the universe, energy shortages are all about not having enough specific forms of energy in specific places at specific times [1], and it’s no surprise that we can’t capture dissipated heat, or that a local power system has a maximum limit at any given time, for example. Something similar could perhaps be said for the video’s approach; “what do we get from the sun?” is an ambiguous question, not necessarily a fair setup to ask a lay person when you have entropy in mind as the answer. We do get energy from the sun, that is a correct answer, and we use some of it before it goes away. But, there is the nice a-ha that all the energy from the sun eventually leaves the earth, right? [1] “An energy crisis or energy shortage is any significant bottleneck in the supply of energy resources to an economy.“ https://en.wikipedia.org/wiki/Energy_crisis https://en.wikipedia.org/wiki/Energy_crisis

JumpCrisscross 3y ago
It’s pithy, but in the way of word play. Energy, colloquially, means useful energy. The question collides the conventional and technical definitions to create the illusion of profundity.
- lisper 3y ago
  Pithy != profound. The intent was to get people to think about the fact that the word "energy" means different things in different contexts, and that the thing that actually has value is not energy but the absense of entropy.
  - JumpCrisscross 3y ago
    > intent was to get people to think about the fact that the word "energy" means different things But the question posed is weaker at prompting that than the sequence of questions posed by the video. It's a strange response that doesn't add to the discussion.