Ok, ok... first of all, energy can change forms.Yes - but then again there are some schools of thought that suggest thinking of energy as having "forms" is completely wrong. They don't suggest that energy is anything solid or anything you can touch, taste, see, hear or feel, it has no form at all. Instead they use concepts where there are "stores" of energy and that energy is just an abstract numerical quantity that seems to be conserved.
...and matter, like it or not, is an actual thing that we can define and see.Just because we can define it and apparently touch it does not mean that we understand it. Science tends to take a reductionist approach, pulling things apart into it's most fundamental components. We think a quark is the most fundamental piece of ordinary matter but we don't know or have a better theory yet. Interestingly, most of the mass of a composite particle like a proton is not due to the sum of the mass of the quarks in it. There is something that we can call binding energy and this is most of the mass of the proton.
Even crazier than this however is a photon's ability to move, like, actually straight up apply motion to matter by transferring their momentum to them.The link between momentum and energy has not gone un-noticed by scientists and mathematicians. There are systems of mechanics that seem to based on momentum (like most conventional Newtonian mechanics) and also systems of mechanics that seem to be based on energy (like Lagrangian mechanics and Hamiltonian mechanics). The two systems seem to be inter-related and allow one to be derived from the other in ways that are quite profound. There are also things like the stress-energy Tensor in General Relativity which use BOTH energy and momentum as sources of gravitation and don't seem to treat either them all that differently. Even in Special Relativty it becomes apparent that we need to work with 4-vectors and then the 4-momentum vector treats energy just as a component of momentum.
And finally, just to top it all of we have the Einstein's famous E = MC² equation, which gave rise to the notion that matter (or I guess mass in this case) and energy were one and the same and could be transformed into each other.The topic of many long articles, threads on forums, documentaries and YT videos. It's been used tacictly already in my reply (protons have mass, most of which is energy not mass from the quarks).
If energy really can't be considered a 'thing' the same way that matter is often considered a 'thing', why does it have any of these properties? Why can I clearly feel and see its effects on the world around me? What actually is energy?I've already mentioned that not everyone considers energy as something that can exist in "forms".
I will attempt to answer by question:
what is value? (Like money.)
I don't mean like physical coinage. Like what do coins represent and what can they be used to exchange? What does it mean that a coin is "worth $1" what if it is a rare coin with a $1 face value but was just sold for $21000?
And any object can have value, but it is context dependent.
Now back to energy: like "value" energy is a property that something can "have" but only in a context set by what else can accept and give energy (or value).
For example: if I am standing on the floor and drop a book on my toe, the book will accelerate in Earth's gravitational field, converting its potential energy into kinetic energy, which is then transferred to my toe when it hits. But if the floor is also falling (say I'm in an airplane in free fall), then when I drop the book, it is in no position to transfer any energy to my toe. You can either think of me and book both falling at the same rate, or you can think of my perspective, which is that the book is weightless. (if we return to the airplane not in free fall, we can think that the book becomes weightless when I drop it, and the plane accelerates my foot up into the book)
Now let's imagine the point of view of the poor seagull under me that is about to get smacked with a book falling at 50 meters per second.
How much energy does the falling book have? Depends who you ask, but everyone will agree about their predictions of what the book will do.
In short: energy is like the money in a made up accounting system that we use to make predictions. Just as we can change the money from $ to ¥ to £ to € and back to $, when can change the energy from light, to heat, chemical potential energy etc. but there is no "pure" form of money, just as there is no "pure" form of energy.
That still doesn't explain why energy exhibits the bizarre properties that it does (e.g. light interacting with matter and black holes the way it does....+similar references to energy in earlier posts.
I find it incredibly difficult to think of energy as anything but a thing.Many people would do the same. Sadly, nature doesn't really care what seems sensible to you (any of us).
That still doesn't explain why energy exhibits the bizarre properties that it does (e.g. light interacting with matter and black holes the way it does and even being able to move it, the ability to be transformed in matter, etc.). Again, with certain pieces of technology, you can see, like straight up perceive with your vision, sound waves and infrared light. Even if energy lacks a true, definitive form, I find it incredibly difficult to think of energy as anything but a thing. Not a visible, tangible thing mind you, but a thing non the less.The answer given by @chiralSPO is the correct scientific answer. Most of your other questions are answered in @Eternal Student post #6.
Ah yes, but/t surely it's the IR photons and the vibrations in the water which scald?Absolutely, that’s what we are saying. Not a ‘thing’ called energy in the water.
So... energy is just molecular/atomic motion?No, but such vibrations are considered to be one form of energy and/or those vibrations do have energy.
Molecular/Atomic motion that can be turned directly into matter,Well, a hot cup of tea has more mass than a cold cup of tea. The only differences that seem to be there when you take a reductionist approach and look at microscopic level is in the kinetic energy of the molecules.
...can be visibly seen in the form of lightNo. Light isn't energy, it's just one form that energy might have and/or it's a thing that has some energy.
and sound and heat become visible too with technologyBeing able to see something (or detect it in some way) is not a requirement for something to have energy. Neutrinos should have kinetic energy but we are struggling to detect them. There is thought to be vaccum energy - energy contained within empty space, there is no substance or radiation in there and nothing to see but there should still be energy content there.
Hi again,
@Aeris , Energy is mysterious and complicated. It's well worth pausing to ask what energy is and you can come up with different ideas at every stage of understanding about Science that you might acquire. I don't claim to know what energy is on any deep level. It seems to be a quantity that can be defined in some systems (but not all systems) and it is conserved in most systems that we do study. I do think it's importance is over-stated, Energy is not as fundamental as we might have thought and the conservation of energy law it isn't quite the sovereign rule that we once thought it was. Most of the evidence for this would come from Noether's theorem, where energy is just a relationship between some variables that describe a system and we see that some systems would not have a conserved quantity we can call energy. There are also some real Astronomical observations which support this idea, so that "the universe" might be one system where total energy is not a well-defined quantity.
Anyway, you're perfectly entitled to your opinions and energy is a truly fascinating concept that is well worth considering and discussing. For the moment, I'll be antagonistic to your last post and try to present the argument that energy doesn't have to be any kind of physical substance.
I myself don't think of energy as a physical substance that you can pick up and hold in your hand. I sorta view energy the same way I view Air. It's invisible and I can't interact with it the same way I can with solids and liquids, but I know that it exists, can visualize it, feel it around me and see it's effects on the environment. Maybe that view is horribly incorrect to what energy actually is, but it's, in my opinion, the most satisfying view I have on the stuff.
Quote No, but such vibrations are considered to be one form of energy and/or those vibrations do have energy.
Ok, what are the other forms then?
Quote Well, a hot cup of tea has more mass than a cold cup of tea. The only differences that seem to be there when you take a reductionist approach and look at microscopic level is in the kinetic energy of the molecules.
At a macroscopic level, the hot cup of tea has more inertial mass (resistance to a change in motion) and more gravitational mass. It has more "mass" by any method you want to define what mass is. Using mass as a measure of the amount of matter, there is more matter in a hot cup of tea. You don't have to read this as an indication that energy has been converted into matter but could instead consider that we might have been wrong about what mass actually is. Perhaps mass was always a manifestation of some energy that has become bound and localised to one region of space.
I'm not talking about warmer objects having more mass than cooler objects though. I'm talking about turning energy into matter the same way scientists turned photons into matter and antimatter particles, or how the Hydrogen atoms of the early universe were made from the energy of the big bang. Black Holes supposedly loose their mass as energy through a process called Hawking Radiation and something similar may very well happen to matter in a few billions years or so once we're all gone called radioactive decay (the theory of Heat Death actually somewhat depends on this happening). Even then though, the fact that objects gain more mass when heated seems like pretty compelling evidence that energy isn't just an extension of matter. It's its own thing all together.
Quote No. Light isn't energy, it's just one form that energy might have and/or it's a thing that has some energy.
This seems like a contradiction. Light isn't energy, but light is also a form that energy may take on? Are you saying that energy has a true, definitive form that changes depending on its surroundings, or are you saying that light is just an extension of matter?
Quote Being able to see something (or detect it in some way) is not a requirement for something to have energy. Neutrinos should have kinetic energy but we are struggling to detect them. There is thought to be vaccum energy - energy contained within empty space, there is no substance or radiation in there and nothing to see but there should still be energy content there.
Meh. I still think that the fact that we're able to see SOMETHING at all is enough proof to show that energy is its own thing, but again, this is just my view. I will never go against the opinions/feelings/thoughts of others no matter how different they may be from mine.
Ok, what are the other forms then?Perosnally, I'm not certain that energy has forms. However, the terminology is in use, it is what I was taught in school and I still use the terminology today sometimes. The problem with the terminology is that it does lead people to think that energy has some substance and measurable physical characteristics.
Perosnally, I'm not certain that energy has forms. However, the terminology is in use, it is what I was taught in school and I still use the terminology today sometimes. The problem with the terminology is that it does lead people to think that energy has some substance and measurable physical characteristics.There is a lot in physics that is shorthand for some detailed descriptions, some of the shorthand can be misleading
Hi.Thank you Eternal Student Yes potential energy is like the sun it is broiling away but the actual energy is the heat that arrives having moved from the sun one can say we are energy but only if we get off the couch and walk to the refrigerator to get a bear is that energy realized. If this is not so then all things sitting must be called energy. Does a dead man have energy only if he moves?
@Just thinking
Your last post is profound. There are a great many scientists that now think energy should be divided into two types: Kinetic and Potential and that is all. Furthermore, potential is just the ability (the potential) to provide the other form of energy. So they would say there is only one genuinely observable form of energy - Kinetic, the energy of movement.
Best Wishes.
I think the most simple answer to what is energy is the power of movement.
walk to the refrigerator to get a bearA polar bear? Or has the barbecue culture gone too far? Strewth, Bruce, it's time to put a grizzly on the griddle...
Would you use "distance" and "speed" in the same way?You have got me there.
I'm starting to think that maybe I'm asking too many "We honestly don't know." questions on here.I don't think you can ask too many questions but I'm not sure what your statement is.
I'm starting to think that maybe I'm asking too many "We honestly don't know." questions on here...We know a lot, but you have to read and understand the @chiralSPO post
I mean I'm asking the kind of questions that you can't give a 100% accurate answer to because they deal with things that we can't test, observe or comprehend.I think your question about what is energy has been answered in many ways but can be refined and discussed further.
I think your question about what is energy has been answered in many ways but can be refined and discussed further.
I'm starting to think that maybe I'm asking too many "We honestly don't know." questions on here...The thing is, you ask them well. It seems (to me anyway) that you didn't want a short definitive answer and some of us prefer to discuss rather than lecture.
Photons, which are LITERALLY made of energy....Photons are NOT made of energy. They are NOT a pure or naked form of energy, there just isn't one. We have never isolated a quantity of stuff we can call "energy", it's always something in a particle, carried by a particle or possessed by a whole system.
Honestly if this was all energy really was, I'd be 110% ok with that.Well that is the best, shortest and most current answer. ChiralSPO said it earlier but this version is even shorter.
So... Photons are the vibrations of an electromagnetic field that manifest as massless particles that can carry both energy and momentum? Am I right in saying this?Sounds reasonable. Fine details could be argued over but you seem to be seeking short answers. (Let's take one obvious example we could argue over - light only sometimes has particle properties and/or particles aren't quite what we might have thought they are).
that just leaves me with even more questions like what are they actually transferring, where do they get their momentum from and where does this electric field exist (is it a property of matter or space?)?Perfectly good questions. Put them in another thread or make it clear you do want those answered.
I just wish we could live in a universe where everything was so simple...No you don't. That would be the end of the story or process we call Science. You want more questions and mysteries, always and it doesn't hurt if the universe is complicated and/or difficult to understand.
When you say ideas, do you mean hypothesizes based on our current understanding of physics? Because if you do (and I cannot stress this enough), I will happily accept the most scientifically-sound/agreed-upon hypothesis as an answer.No, I meant there is some history, various ideas that are now discredited, some sideline discussions that will surely pop up along the way, more general discussion around the topic etc.
Since I have so many more questions similar to this one, can I post all of them at once on a single thread? Like, is that allowed? Asking multiple questions in a single thread?I'm not a moderator but the following seems reasonable:
your weight sliding across the surface of a smooth skating rink doesn't do much work,It is a great shame that uttering the scientific definition "Conservative forces do no work" would get you banned from the BBC.
very funny.your weight sliding across the surface of a smooth skating rink doesn't do much work,It is a great shame that uttering the scientific definition "Conservative forces do no work" would get you banned from the BBC.