# Different forms of physical energy **URL:** \ **Category:** Factual Questions\ **Created:** [January 28, 2009, 1:51am UTC](https://boards.straightdope.com/t/different-forms-of-physical-energy/483331 "2009-01-28T01:51:10Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Kalico](https://avatars.discourse-cdn.com/v4/letter/k/8baadc/32.png) [@Kalico](https://boards.straightdope.com/u/Kalico)\ **Post date:** [January 28, 2009, 1:51am UTC](https://boards.straightdope.com/t/different-forms-of-physical-energy/483331/1 "2009-01-28T01:51:10Z")
Besides light, thermodynamic, electric, chemical, electromagnetic, magnetic, elemental (wind, earth, fire, water) and atomic, molecular, and radioactive energy what other forms of physical energy are there? ---
**Author:** ![Cider\_Depot](https://avatars.discourse-cdn.com/v4/letter/c/e274bd/32.png) [@Cider\_Depot](https://boards.straightdope.com/u/Cider_Depot)\ **Post date:** [January 28, 2009, 2:00am UTC](https://boards.straightdope.com/t/different-forms-of-physical-energy/483331/2 "2009-01-28T02:00:11Z")
how about kinetic? What do you mean by elemental? Fire is chemical energy being converted into thermodynamic energy; wind is thermdynamic energy being converted into kinetic energy. Never heard of earth energy ---
**Author:** ![Kalico](https://avatars.discourse-cdn.com/v4/letter/k/8baadc/32.png) [@Kalico](https://boards.straightdope.com/u/Kalico)\ **Post date:** [January 28, 2009, 2:15am UTC](https://boards.straightdope.com/t/different-forms-of-physical-energy/483331/3 "2009-01-28T02:15:40Z")
Is there such a thing as cosmic radiation? If so, does that stem from the other forms? ---
**Author:** ![Pasta](https://avatars.discourse-cdn.com/v4/letter/p/ecccb3/32.png) [@Pasta](https://boards.straightdope.com/u/Pasta)\ **Post date:** [January 28, 2009, 2:31am UTC](https://boards.straightdope.com/t/different-forms-of-physical-energy/483331/4 "2009-01-28T02:31:26Z")
It’s not clear what semantic context you wish to draw from. For instance, what is “earth” energy? Given that that appears in your list, I might take your question to be, “What things are (or have been) associated with the word ‘energy’ over the ages?” If you are instead interested in energy as a concept in physics, then you have a small list to choose from. Essentially all energy you encounter in daily life is one of: kinetic energy (stuff moving), photons and photon exchange (electromagnetism), and gravity. Completing the list are the strong and weak forces, which manifest themselves less obviously (with a big exception being the sun and other stars, which are turning potential energy due to the strong force into kinetic and electromagnetic energy.) But you might mean “energy” is some more vernacular way, in which case the question might need to be made more specific. ---
**Author:** ![Really\_Not\_All\_That\_Bright](https://avatars.discourse-cdn.com/v4/letter/r/e8c25b/32.png) [@Really\_Not\_All\_That\_Bright](https://boards.straightdope.com/u/Really_Not_All_That_Bright)\ **Post date:** [January 28, 2009, 2:43am UTC](https://boards.straightdope.com/t/different-forms-of-physical-energy/483331/5 "2009-01-28T02:43:20Z")
What happened to potential energy? ---
**Author:** ![Pasta](https://avatars.discourse-cdn.com/v4/letter/p/ecccb3/32.png) [@Pasta](https://boards.straightdope.com/u/Pasta)\ **Post date:** [January 28, 2009, 3:05am UTC](https://boards.straightdope.com/t/different-forms-of-physical-energy/483331/6 "2009-01-28T03:05:11Z")
> [@Really\_Not\_All\_That\_Bright](#): > > What happened to potential energy? It’s there. All of the non-kinetic items above could be called potential energy, depending on the context. Ball on top of a hill? It has gravitational (potential) energy. I could list chemical energy, radio energy, energy in a compressed spring, energy from an LED, muscular energy, and on and on, but these are all just electromagnetic energy in various guises. This is why some context is necessary to go further (unless the context is simply “anything that one might put in front of the word ‘energy’”, in which case the OP is asking about etymology, semantics, and history.) ---
**Author:** ![Kalico](https://avatars.discourse-cdn.com/v4/letter/k/8baadc/32.png) [@Kalico](https://boards.straightdope.com/u/Kalico)\ **Post date:** [January 28, 2009, 3:06am UTC](https://boards.straightdope.com/t/different-forms-of-physical-energy/483331/7 "2009-01-28T03:06:39Z")
I just saw this at wikipedia from [Energy - Wikipedia](http://en.wikipedia.org/wiki/Energy) : Energy (from the Greek ἐνέργεια - energeia, “activity, operation”, from ἐνεργός - energos, “active, working”[1]) is a scalar physical quantity that is an attribute of objects and systems that is subject to conservation law. In physics, energy is defined as the work of certain force. Various kinds of energy (gravitational, elastic, electric, magnetic, etc) are usually named after corresponding force. Several different forms of energy exist to explain all known natural phenomena. These forms include (but are not limited to) kinetic, potential, thermal, gravitational, sound, light, elastic, and electromagnetic energy. Any form of energy can be transformed into another form, but the total energy always remains the same. This principle, the conservation of energy, was first postulated in the early 19th century, and applies to any isolated system. According to Noether’s theorem, the conservation of energy is a consequence of the fact that the laws of physics do not change over time.[2] Although the total energy of a system does not change with time, its value may depend on the frame of reference. For example, a seated passenger in a moving airplane has zero kinetic energy relative to the airplane, but non-zero kinetic energy relative to the Earth. ---
**Author:** ![Absolute](https://avatars.discourse-cdn.com/v4/letter/a/b2d939/32.png) [@Absolute](https://boards.straightdope.com/u/Absolute)\ **Post date:** [January 28, 2009, 3:16am UTC](https://boards.straightdope.com/t/different-forms-of-physical-energy/483331/8 "2009-01-28T03:16:21Z")
It should be noted that energy is really just a bookkeeping quantity that makes our understanding of physical systems easier. It isn’t real or physical at all. When we talk about different “forms” of energy, we’re really talking about how we can measure this abstract property called energy in different physical systems. But energy itself doesn’t exist - it isn’t real, it doesn’t do anything. It’s just a verbal shorthand for referring to the actions of innumerable physical processes. ---
**Author:** ![Really\_Not\_All\_That\_Bright](https://avatars.discourse-cdn.com/v4/letter/r/e8c25b/32.png) [@Really\_Not\_All\_That\_Bright](https://boards.straightdope.com/u/Really_Not_All_That_Bright)\ **Post date:** [January 28, 2009, 3:38am UTC](https://boards.straightdope.com/t/different-forms-of-physical-energy/483331/9 "2009-01-28T03:38:59Z")
> [@Pasta](#): > > It’s there. All of the non-kinetic items above could be called potential energy, depending on the context. Ball on top of a hill? It has gravitational (potential) energy. That’s the one I meant. In my physics classes (up to introductory college level, and no further) potential always referred to “things in a high place”. ---
**Author:** ![Santo\_Rugger](https://avatars.discourse-cdn.com/v4/letter/s/e95f7d/32.png) [@Santo\_Rugger](https://boards.straightdope.com/u/Santo_Rugger)\ **Post date:** [January 28, 2009, 3:54am UTC](https://boards.straightdope.com/t/different-forms-of-physical-energy/483331/10 "2009-01-28T03:54:44Z")
> [@Absolute](#): > > It should be noted that energy is really just a bookkeeping quantity that makes our understanding of physical systems easier. It isn’t real or physical at all. > > When we talk about different “forms” of energy, we’re really talking about how we can measure this abstract property called energy in different physical systems. But energy itself doesn’t exist - it isn’t real, it doesn’t do anything. It’s just a verbal shorthand for referring to the actions of innumerable physical processes. I don’t get it. Is this the equivalent to saying length doesn’t exist, we just use meters as bookkeeping to make our calculations easier? ---
**Author:** ![Really\_Not\_All\_That\_Bright](https://avatars.discourse-cdn.com/v4/letter/r/e8c25b/32.png) [@Really\_Not\_All\_That\_Bright](https://boards.straightdope.com/u/Really_Not_All_That_Bright)\ **Post date:** [January 28, 2009, 3:57am UTC](https://boards.straightdope.com/t/different-forms-of-physical-energy/483331/11 "2009-01-28T03:57:39Z")
> [@Santo\_Rugger](#): > > I don’t get it. Is this the equivalent to saying length doesn’t exist, we just use meters as bookkeeping to make our calculations easier? I think he’s saying there’s no instrinsic reason to label heat energy released during combustion as the same thing as kinetic energy released when you kick a ball. We could just as easily call it heat [some other word] and kinetic [yet another word]. I’m not so sure that that’s _accurate_, just that I think that’s what he’s saying. ---
**Author:** ![Pasta](https://avatars.discourse-cdn.com/v4/letter/p/ecccb3/32.png) [@Pasta](https://boards.straightdope.com/u/Pasta)\ **Post date:** [January 28, 2009, 4:32am UTC](https://boards.straightdope.com/t/different-forms-of-physical-energy/483331/12 "2009-01-28T04:32:02Z")
> [@Kalico](#): > > Several different forms of energy exist to explain all known natural phenomena. These forms include (but are not limited to) kinetic, potential, thermal, gravitational, sound, light, elastic, and electromagnetic energy. This list is a good example of why I say context is relevant. Light and elastic energy are both electromagnetic energy. It’s just sometimes useful to talk about these manifestations separately. Thermal and sound energy are just kinetic energy on a molecular level (plus electromagnetic energy keeping molecules from occupying the same space.) As a different example, consider the energy in a piece of cake. One person might say that the cake has 500 Calories of chemical energy. A dietician, however, might say that the cake has 200 Calories of fat energy, 100 Calories of sugar energy, 150 Calories of other carb energy, and 50 Calories of protein energy. To the dietician, those different manifestations of chemical energy are relevant, so (s)he might want to separately identify them. But at the fundamental level, these are all just forms of electromagnetic potential energy. In making a list of energies, should both “fat energy” and “protein energy” be listed? Well, it depends on what you’re after. Just saying “chemical energy” counts both already, and just saying “electromagnetic energy” gets even more. One more example: say that you are trying to build a card house on a table. You have to protect your cards against disturbance or else they’ll fall down. You might close the windows to block wind energy; you might put bricks on the table to suppress seismic energy; you might turn off your subwoofer to eliminate sound energy. However, the only reason it looks like three different energies is because the context made them relevant. In reality, they are all just manifestations of kinetic, electromagnetic, and (depending on the nature of the seismic one) gravitational energy. No matter what “energy” you try to list, it will be a manifestation of kinetic energy plus some combination of the four fundamental forces (electromagnetic, gravitational, strong, and weak). As the cake example hopefully shows, there is no other unique list of “energies” – it all depends on context and on what humans have decided is worth separately labeling in those contexts. If you are looking for a list of anything anyone has every labeled “energy”, that is reasonable, but it is a language question. Such a list will have lots of overlap when viewed with a physical eye. ---
**Author:** ![Absolute](https://avatars.discourse-cdn.com/v4/letter/a/b2d939/32.png) [@Absolute](https://boards.straightdope.com/u/Absolute)\ **Post date:** [January 28, 2009, 4:36am UTC](https://boards.straightdope.com/t/different-forms-of-physical-energy/483331/13 "2009-01-28T04:36:55Z")
Length is a property you can measure directly. You can’t measure energy directly, because it doesn’t exist. It is purely an invented, derived quantity. You can measure other things directly, like a car’s mass and velocity, and then perform the appropriate calculations to determine how much “energy” that corresponds to - but you’re just doing math. There is no physical substance or entity or effect or field or process that is “energy”. Energy is simply an easy way of describing how many different physical processes interact. I am not just making shit up here. Let me quote Richard Feynman: > [@Richard Feynman](#): > > There is a fact, or if you wish, a law, governing natural phenomena that are known to date. There is no known exception to this law; it is exact, so far we know. The law is called conservation of energy; it states that there is a certain quantity, which we call energy, that does not change in manifold changes which nature undergoes. That is a most abstract idea, because it is a mathematical principle; it says that there is a numerical quantity, which does not change when something happens. It is not a description of a mechanism, or anything concrete; it is just a strange fact that we can calculate some number, and when we finish watching nature go through her tricks and calculate the number again, it is the same. ---
**Author:** ![Nametag](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/nametag/32/406_2.png) [@Nametag](https://boards.straightdope.com/u/Nametag)\ **Post date:** [January 28, 2009, 7:06am UTC](https://boards.straightdope.com/t/different-forms-of-physical-energy/483331/14 "2009-01-28T07:06:26Z")
Feynman’s not saying that energy doesn’t exist; he’s saying that the true nature of energy isn’t physically observable, and that it’s a mistake to identify it too closely with the phenomena that we observe and the mechanisms we use to manipulate it. There is much in the universe that we can only describe accurately through mathematics – physical comprehension is only approximate, and ultimately misleading. ---
**Author:** ![WoodenTaco](https://avatars.discourse-cdn.com/v4/letter/w/45deac/32.png) [@WoodenTaco](https://boards.straightdope.com/u/WoodenTaco)\ **Post date:** [January 28, 2009, 7:12am UTC](https://boards.straightdope.com/t/different-forms-of-physical-energy/483331/15 "2009-01-28T07:12:42Z")
> [@Absolute](#): > > Length is a property you can measure directly. You can’t measure energy directly, because it doesn’t exist. It is purely an invented, derived quantity. You can measure other things directly, like a car’s mass and velocity, and then perform the appropriate calculations to determine how much “energy” that corresponds to - but you’re just doing math. There is no physical substance or entity or effect or field or process that is “energy”. Really? What about gauge bosons? Do you think photons don’t exist? What _does_ exist to you? ---
**Author:** ![Kalico](https://avatars.discourse-cdn.com/v4/letter/k/8baadc/32.png) [@Kalico](https://boards.straightdope.com/u/Kalico)\ **Post date:** [January 28, 2009, 8:49am UTC](https://boards.straightdope.com/t/different-forms-of-physical-energy/483331/16 "2009-01-28T08:49:50Z")
I forgot about sound energy. ---
**Author:** ![hobscrk777](https://avatars.discourse-cdn.com/v4/letter/h/a6a055/32.png) [@hobscrk777](https://boards.straightdope.com/u/hobscrk777)\ **Post date:** [January 28, 2009, 5:46pm UTC](https://boards.straightdope.com/t/different-forms-of-physical-energy/483331/17 "2009-01-28T17:46:53Z")
> [@Kalico](#): > > Besides light, thermodynamic, electric, chemical, electromagnetic, magnetic, elemental (wind, earth, fire, water) and atomic, molecular, and radioactive energy what other forms of physical energy are there? Light, magnetic, and electromagnetic are all the same thing: electromagnetic radiation. ---
**Author:** ![WoodenTaco](https://avatars.discourse-cdn.com/v4/letter/w/45deac/32.png) [@WoodenTaco](https://boards.straightdope.com/u/WoodenTaco)\ **Post date:** [January 28, 2009, 9:30pm UTC](https://boards.straightdope.com/t/different-forms-of-physical-energy/483331/18 "2009-01-28T21:30:06Z")
> [@Kalico](#): > > I forgot about sound energy. Sound energy is kinetic energy. It’s a wave of pressure formed by air molecules bumping into each other at certain frequencies; those molecules bump into others forming the wave. When the wave hits your eardrum, your brain interprets it as sound. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [January 28, 2009, 9:56pm UTC](https://boards.straightdope.com/t/different-forms-of-physical-energy/483331/19 "2009-01-28T21:56:24Z")
> [@](#): > > You can’t measure energy directly, because it doesn’t exist. It is purely an invented, derived quantity. You can measure other things directly, like a car’s mass and velocity, and then perform the appropriate calculations to determine how much “energy” that corresponds to - but you’re just doing math. So, you can’t measure any sort of energy directly, but you can directly measure the rest energy of a car? ---
**Author:** ![YamatoTwinkie](https://avatars.discourse-cdn.com/v4/letter/y/cc9497/32.png) [@YamatoTwinkie](https://boards.straightdope.com/u/YamatoTwinkie)\ **Post date:** [January 28, 2009, 10:04pm UTC](https://boards.straightdope.com/t/different-forms-of-physical-energy/483331/20 "2009-01-28T22:04:01Z")
> [@Kalico](#): > > Besides light, thermodynamic, electric, chemical, electromagnetic, magnetic, **elemental (wind, earth, fire, water)** and atomic, molecular, and radioactive energy what other forms of physical energy are there? How about “Heart”? …By your powers combined, I am Captain Planet! [Next page](https://boards.straightdope.com/t/different-forms-of-physical-energy/483331.md?page=2)