# Help me! Super New bee many questions on energy-space relation and waves.

1. Jan 10, 2009

### wannaknow4995

Hey, I'm a new guy here and also to physics, Consider me a baby in the subject, but I love the subject. My question is simple. Does energy require space like matter to "exist"?? Considering that most forms of energy are waves. Does energy require matter to "exist"??
Does light have mass?? Can energy be independent of matter?? If light has mass, does it increase the mass of earth each second?? How many waves can pass through a point?? Infinite?? Please, please someone answer these questions. I'm dieing to learn more. I have to learn more! Help me!!! A humble request from a guy who wants to know.....

2. Jan 10, 2009

### Redbelly98

Staff Emeritus
Welcome to PF.

I want to say that no, energy does not require matter. Electromagnetic waves (light and radio waves, for example) can exist in a vacuum with no matter present.

That being said, EM waves do need matter, specifically charged particles, in order to be generated in the first place. So in that sense matter is necessary.

I'm trying to think of other forms of energy: kinetic energy, heat, sound, gravitational or electrostatic potential, mass itself ... all these are directly tied in to matter.

Hope that helps some.

3. Jan 10, 2009

### jshuford

No, light does not have mass. The particle of light, the photon, is mass-less. However, it is still affected by gravity.

I assume you mean at one time. That's a tricky question. I'm going to go with infinite though. Someone might correct me on this one though. Since waves have no mass there's nothing to physically prevent them from moving past each other at the point they intersect. Now it's possible, even probable, that a large number of waves moving through one point would interfere with each other, but I don't think that you would reach a point that something was physically stopping them from moving through a given point.

If you want to know more I'd start with "A Brief History of Time" and "The Universe in a Nutshell" by Stephen Hawking. Both of those are excellent. The illustrated version of Brief History I found particularly helpful. Also, "Cosmos" by Carl Sagan is great.

4. Jan 11, 2009

### wannaknow4995

Thank you for giving the answer, Red belly and Jshuford. One more question that I'd like u guys to think over is here... As mentioned previously in the question, "Does energy{considering energy waves and not particles} require space(empty space, not the spacial space above the atmosphere) to 'exist'??
Jshuford, tell me more about "The history of time"

Last edited: Jan 11, 2009
5. Jan 11, 2009

### Hunterbender

EM waves come from energy, so they need matter in order to be created. In addition, can you imagine energy outside of space? Since space is a dimension that matter and energy act on, I think it is hard to remove space from the picture. (unless you mean vacuum, which isn't exactly empty space).

The history of time, well, that is a long story. I recommend that you read Universe in a Nutshell by Hawking, it answers all these questions and more! (they even have an audio version for it. Don't worry, Hawking isn't the one reading. Lol)

6. Jan 11, 2009

### gmax137

"Energy" is not a "thing" -- it is a construct of the human mind. It does not require 'space' in order to exist, any more than '3.25' requires space. Sorry if that is a little obscure.

How's this?: Energy is a notion we use to simplify our thoughts, to facilitate our calculations. Did you see the other thread on free fall? In there someone said, "the maximum velocity is equal to the escape velocity" - this is a calculation facilitated by using 'energy.' We calculate the 'potential energy' due to the separation of the masses, and then calculate a velocity assuming that all of that 'potential' is 'converted' to 'kinetic energy.' This approach easily gives us the right answer, but the masses themselves, all they feel are the forces. They are blissfully unaware of the 'energy.' There is no conversion of anything except in our minds.

7. Jan 13, 2009

### wannaknow4995

Wow, thanks gmax! That was a beautiful answer. Now I'm clear of what I'm dealing with now, thanks. :)

8. Jan 14, 2009

### wannaknow4995

What do u mean by the term "dimension"? When I meant space, I meant space as empty space, not vacuum , or a dimension(p.s. I dunno what a dimension is.) Thanks for your reply anyway. Yeah, space can't be ignored, since, matter and energy act on it. But, the question was, "Does it need space to exist?" {No doubt matter requires space to sxist} Is vacuum empty space? I dont know.... Thats the reason I'm asking lol :D Thanks for ur answer, Can u reply this plz? :)

9. Jan 14, 2009

### jshuford

This is getting picky with definitions, but basically yes. A vacuum is defined by an area of space that is free of matter. A vacuum may, and inevitably does, contain energy however. Energy does not need matter to exist.

As for the term "empty space", this gets into the vagaries of the term "space". "Space" is defined by the four important dimensions, height, width, depth and time (I'll elaborate more on this below). But people also use the word "space" to mean the area outside the earth's atmosphere that the stars and planets are in (as in "The Space Race", the time when the Soviet Union and America were competing to launch satellites and orbiting craft, or the Space Shuttle). Another term is "outer space", which is almost certainly better to use, as it's at least slightly less confusing. So, if we define "outer space" as the area outside of Earth's atmosphere, then yes it is a functional vacuum. It's not a perfect vacuum, there are a few interstellar particles floating around out there, but the density is so low that there's no real difference for most purposes. But you probably already knew that. I was just making sure that we were all using consistent terms. You'd be surprised how important that is in science, and how many misunderstandings happen when two people are saying the same word and meaning different things!

Ok, let's see if I can help you on this one. There are four "dimensions" in which we functionally operate: Height, width, depth, and time (there are probably a good bit more, but they probably aren't very useful and we don't interact with them, but that gets more complicated than you need right now). Dimensions are defined mathematically, but you can understand them without the math. Let me see if I can explain:

Imagine a single point, as a zero dimension object. Now imagine stretching that point in some direction, by doing this you get a 1-dimensional object. It now has width, so your point becomes a line. By stretching your 1-dimensional object in a new direction, you get a 2-dimensional object. If you stretch it straight "up", your line becomes a square. Now it has width and height. Stretch it in another direction and you get depth. Mathematically there's no reason to stop there, you could keep on adding dimensions, but we know from observation that our universe only has three dimensions that we operate in. However, it's worth noting that some math uses high dimension space for conceptual purposes.

Let me give you another example, your computer screen, right now, is projecting you an image that you see in two dimensions. You have height and width, but no depth. You can't reach into your screen, thus no depth. A TV is the same way. That's why, if you've ever watched American Football, on a Field Goal kick, when the ball is in the air, sometimes you think the ball is going to miss going through the goal posts, but in reality, the kick is straight down the middle. You don't see it correctly without depth (the third dimension). Time is the fourth dimension, and probably a bit of a special case from the others, and a bit too complicated for me to explain, mostly because I probably understand only a little more than you. :)

So when we think of "space" (not necessarily "outer space", but just, for instance, empty space on a table) we are thinking of those three dimensions which we interact with freely, height, width, and depth; and time, which is a special dimension we can only move through in one direction (we can't go backwards in time, obviously ;) ).

So, space, in those four dimensions, is pretty much what the universe exists in. If there were no space, there would be no height, width, depth or time. A place without space would have to be outside the boundaries of the universe (if such a thing can even be said to exist, which it probably doesn't). So, I'm going to disagree with gmax and say that yes, in that sense, energy needs "space" to exist. I guess the "concept" of energy is arguably independent of space (and I would argue against even that), but energy, as a measurable phenomenon, cannot exist in a place that has no "space". We couldn't, for instance, transmit a radio wave or an X-Ray outside the boundaries of the universe. In fact, there is no place in the universe without "space". It's kind of an oxymoron, since the universe is defined by the existence of space.

Oh, and you asked for more information about "A Brief History of Time", well check out https://www.amazon.com/Illustrated-...s_sr_2?ie=UTF8&s=books&qid=1231953243&sr=8-2". I would very strongly recommend this book. I read it when I was in High School and it really sparked my interest in understanding the universe.

Last edited by a moderator: Apr 24, 2017
10. Jan 14, 2009

### jshuford

Gmax137, I disagreed with you in my above response, but I wanted to elaborate on my disagreement more directly with you to give you a chance to respond if you want.

So first, let's establish our terms. Space is simply that which things exist in. Like I said in my above post, in our universe "space" is defined by height, width, depth, time (and maybe whatever extra dimensions String Theory needs if String Theory is right). There is no "space particle", but space is measured by our interaction with it, and the interaction of other things in the universe with each other. Things move through space, and exist within it, matter and energy curve it; that's how we know space is there.

You equate energy with numbers, and I think that's probably fair in some ways, but here are two thoughts:

1) Not to get into the whole ontology of mathematics argument, but numbers can't exist without space either. First, if you deal with numbers as a concept, numbers need something to conceive of them (an intelligent being), and that can't exist without space (at least not in any way we can conceive and thus the point is moot for a scientific discussion). Numbers are probably not (if you ask me) a fundamental aspect of the universe independent of intelligent observation. They're a useful construct of thinking beings, created to help explain and conceptualize what they're experiencing.

But even more fundamentally, numbers are abstract representations of things. Even if you say numbers exist independent of the concept of numbers, if there were no space there would be no "things" and thus nothing for numbers to represent. They would be like an acronym that wasn't short for anything. They would just be words that didn't (and couldn't) represent anything.

2) Energy, unlike numbers, does exist independently of an intelligent observer. Before there were humans to calculate motion and define energy, the sun was radiating heat to the Earth, and the universe was expanding. Both of those need energy. So yes, the concept of energy, like numbers, is an idea intelligent beings came up with to explain what they see, but those concepts are actually representing something that exists in the universe independent of the observers who invented the concepts. If no idea for energy were ever invented, the sun would still burn and the universe would still expand. So while, again, the concept of energy exists in our minds, that which the concept represents exists independent of our observation.

However, energy does not exist independent of the universe. A radio wave probably can't exist without depth or time. I say probably because we, of course, can't possibly conceive of anything that exists outside the universe since we can't possibly have any frame of reference for it. But there are several good theories that say that there doesn't need to be anything outside the universe, and in fact there probably isn't. There is absolutely nothing outside the universe, no height, width, time, and certainly not any energy. It's not like there's some empty thing that the universe is expanding into. What the universe is expanding into doesn't exist until the universe expands into it. In a way, you could say that the area outside of the universe is defined by a negative. It is defined by the total lack of things that are inside the universe. So therefore, energy cannot be there.

Last edited: Jan 14, 2009
11. Jan 16, 2009

### gmax137

OK - you & I might like it for awhile, but it is bound to irritate the others. Plus, it would be off-topic.

Where does energy exist? Go fetch me a bucket of energy.

No, the sun was emitting photons of various frequencies; or if you like it was radiating electromagnetic waves. There isn't a stream of "energy" flying away from the sun.

In my view energy is a calculational aid. A bookkeeping device. It's like the gross domestic product. You can carry bananas, or tractors, or even cash. But you can't put your hands on the GDP.

12. Jan 16, 2009

### The Dagda

Energy is what happens when matter interacts directly or indirectly. Which is why it has so many different types, from kinetic to gravitational to chemical.

It is not matter in and of itself as it has theoretically no mass. So you could say energy are fields, and matter is what exhibits/produces those fields. No matter no energy, photons are basically what everything that is matter will degrade to given enough time and assuming theory is correct, consider them fundamental to particles and fundamental in their own right as "particles".

Heat death is a good issue to research here.

Wiki: heat death of the Universe.

13. Jan 16, 2009

### The Dagda

Indeed there is no time and space outside of the Universe because the Universe creates its own time and space to expand into if you see what I mean.

Thus the term outside the universe is not only unobservable, but unlikely too. If there are millions of other Universes chances are we could never experience them on any more of an abstract level.

If some theories are correct eventually if you started off from point a and went in the direction of x you would end up back at a. But no one is entirely sure of this, the observable Universe is actually smaller than the Universe so there's no way of directly knowing as such.

14. Feb 9, 2009

### wannaknow4995

To jshuford and gmax... U both appear to be right in your own ways about energy and space. Initially, people did consider the mathematical definition of "Energy."(energy as capacity to do work.)-> gmax considered this. Me, considering this,

Gmax, my question to you is, Do electromagnetic waves posses only energy and has no matter or mass? If it is so, we can consider sun to be emitting energy itself. If not so, we can say energy is not being emitted by sun. The e-m waves have the capacity to do work,(photo electric effect) so they have energy, right? By the way, you asked Jshuford to get a bucket of energy. Nice question, very nice indeed, but when u get a bucket of water(matter which also has mass) also contains energy. Therefore, you have a bucket of matter and energy, the capacity to do work. :-D

Gmax, after a deep thinking period, I do think energy requires "space" because, energy is mathematically, capacity to do work, which means
E=capacity of{Force*displacement} is true. If that is true, from, F = m a we can say,
E = capacity of {m a d(d=displacement)}
Since acceleration is velocity per time "mathematically" Since velocity(in 3 dimensional motion) needs the three dimensions to be defined, the definition of acceleration can be explained by space. Hence energy requires the dimension "space" to be defined.
I think that I may be wrong, if I am... someone please rectify me. :-)

I have another question to both of you now. Do electro-magnetic waves require space(vacuum not the dimension "space") to exist? I hope this is not an absurd question. :-)

[Please do ignore the grammatical errors :-D]

Last edited: Feb 9, 2009
15. Feb 9, 2009

### wannaknow4995

To Jshuford and gmax i'd like to mention that there are two types of scientists and people who study science.
1.) People who study science with imagination by imagining the various scientific phenomenon.
2.) People who study science mathematically with mathematic definitions and verifications.

I am one of the first of the two groups. I'd like to be explained with examples and statements which require imagination. Explaining with mathematical terms may result in a failure for me to understand.
I would like to add the both of u as my friends.. what do u say?

16. Feb 9, 2009

### wannaknow4995

Err... What is time? Can you define it? I ask this to you Dagda as you said "The universe creates its own time and space." Please Can you prove it? :-)

17. Feb 9, 2009

### wannaknow4995

Hunterbender, The reason I asked that question is, I can "imagine" energy out of space. But is it practical?????? Please do reply. :-)

18. Feb 9, 2009

### wannaknow4995

Hunterbender, I can "imagine" energy out of space... But is it practical?

19. Feb 9, 2009

### The Dagda

I can't prove it it is a hypothesis primarily by Stephen Hawking et al about the singularity at t>0, the outcome of which is that space and time have no meaning before the BB and the Universe. So let's just say it's an educated guess at conditions close to the big bang, it's fairly complicated stuff to do with gravitation and some hypothetical force conditions as they become discrete from the point that is the singularity.

Last edited: Feb 9, 2009