# Why are planets spherical? Why are molecules spherical?

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Sure there is. Unless an object is in a vacuum, there is constant stream of oxygen molecules on it.

I don't get the importance of a stream of light waves on an object, though. Other than making sure we see it later, what's the relevance? We can only see things that have light. That's about it for the relevance. No?

I meant because light travels at maximum speed and everything else moves relative to that speed, the number of waves (peak, troughs, pick a reference point on the wave) remains fixed regardless of the motion or observed distance/time either observer. I.e. waves can shift to longer and shorter wavelengths but the number of waves is fixed because the amount of energy is fixed.

"Number of waves" makes no sense. Do you mean 'number of peaks' perhaps, as in higher frequency? do you mean more intensity? What number of waves? Wavelength? Wavenumber (1/wavelength) ?

I mean that frequency refers to #waves/second. For a speedy observer, the frequency increases though the speed of the waves is measured to be C. A really fast observer could measure lots of very high frequency x-rays because those waves are blueshifted radiowaves, while an observer at the source would view them as radiowaves because the source is not moving relative to the waves. Either way, the number of waves traversed during the journey of one to the other is the same, although time and distance may be measured differently for each. The moving traveller would measure the waves as x-rays and thus measure a much shorter journey that the observer viewing the waves as radio-waves, also moving at C relative to that vantage point. Am I getting this wrong?

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Frequency is clearly defined, lemur:

http://en.wikipedia.org/wiki/Frequency#Frequency_of_waves

It isn't "number of waves" per "second". There's no such thing is "number of waves". Do you mean a Period? Number of cycles?

Frequency = Velocity / Wavelength.

In the case of electromagnetic waves (such as light) the velocity is the speed of light. Hence, frequency is

F = c/Wavelength.

I meant because light travels at maximum speed and everything else moves relative to that speed, the number of waves (peak, troughs, pick a reference point on the wave) remains fixed regardless of the motion or observed distance/time either observer. I.e. waves can shift to longer and shorter wavelengths but the number of waves is fixed because the amount of energy is fixed.

I understand what you mean but it's not right, and it just serves to confuse you.

You know, maybe you should look at the math a bit. It's relatively easy math, nothing too fancy (pure algebra) and it might show you what the transformations mean?

See here as starting point: http://en.wikipedia.org/wiki/Lorentz_transformation

(Forget about the 'matrix form', it's not needed for the sake of this argument, the basics of lorentz transform are enough for now. But reading that article might help you understand the transformations that happen (time dilation, length contraction) when seeing between different reference frames.

~moo

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Interesting, I was under the impression Dark Matter was in "halos" around galaxies? Again, this is totally not my field, and completely and utterly above my head. http://www.universetoday.com/960/dark-matter-halo-around-the-milky-way/

Common confusion between the everyday usage of a word and the scientific meaning. In astronomy "Halo" refers to a spherical cloud or volume.

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Common confusion between the everyday usage of a word and the scientific meaning. In astronomy "Halo" refers to a spherical cloud or volume.

Ha! Nice... Thanks

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Why? Why shouldn't light take multiple paths between source and observer and re-integrate to form a coherent image at the point of the observer? Isn't this the way electrons travel, i.e. as lighting bolts?

edit: when electricity travels through a consistent conductor, the transmission appears integrated and stable, but if the same current has to flow across a distance of air or other insulating medium, it can fragment and take erratic and multiple paths.

The point of a telescope is to resolve only the light coming from a particular direction, so re-integrating would be somewhat difficult. Gravitational lensing has been observed, however. This effect would be noticeable, or the change in light behavior would be observable in the laboratory.

I know that. I was assuming a situation where it would somehow be possible to trace the same beam(s) of light identifiable by both source and receiver. E.g. if a constant radio signal was present throughout the entire journey, the number of waves could be counted as the same regardless of how length-shifted they would be by any observer.

Yes.

Frequency is clearly defined, lemur:

http://en.wikipedia....quency_of_waves

It isn't "number of waves" per "second". There's no such thing is "number of waves". Do you mean a Period? Number of cycles?

Frequency = Velocity / Wavelength.

In the case of electromagnetic waves (such as light) the velocity is the speed of light. Hence, frequency is

F = c/Wavelength.

If we consider one wave to be one wavelength, frequency is exactly the number of waves per second passing a certain point. There's no need to be condescending.

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If we consider one wave to be one wavelength, frequency is exactly the number of waves per second passing a certain point. There's no need to be condescending.

I didn't mean to be condescending, I apologize if that's how it came through. I was truly confused, and since the term kept repeating itself, I was getting a bit frustrated.

We should try and stick to existing terms so we know what we are all talking about.

~mooey

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If we consider one wave to be one wavelength, frequency is exactly the number of waves per second passing a certain point. There's no need to be condescending.

Thanks. It does actually make me feel a little dumb and confused because my physics learning has not been academic the way other people's has been. Of course I want to know when I've misinterpreted some concept by taking it out of context, but I think of "wavelength" and "frequency" as very empirically tangible terms. The length of a wave is another name for its frequency, if it is traveling at a fixed speed. "Frequency" literally means how frequent (how often) a wave passes and if more waves pass in the same period, their length has to necessarily be shorter. The redshifting/blueshifting/dilation/contraction stuff throws off intuition and complicates the math (I assume because I don't follow the exact math that closely); but the logic seems to be pretty clear that if you speed up relative to a star and the light-waves always reach you at C, then the fact that you're intercepting the waves more frequently means that their frequency has increased. Likewise, since time is measured the same vis-a-vis light in all situations, that also means that a second's worth of what you measure as x-rays emitted from the star are going to equal a longer time-period of, say, infrared rays from the perspective of an observer in orbit around the star. So while you are measuring your movement toward the star in the quantity of x-ray radiation received per minute at your time rate, the observer at the star would be measuring your movement as quantity of infrared waves emitted between your departure and arrival. You would both count the same number of waves emitted, only the wavelength of the waves and amount of time measured by each of you would be different.

I suppose you could calculate the rate of gap-closing between any two objects by measuring the distance in number of light-waves received at two different moments and then giving the speed as the difference per amount of time you measured on your clock between the two wave-counts. Now I'm getting confused, though, because I'm wondering when you would start and stop counting waves. If you start at the moment the image of the departing ship arrives, when do you stop? All you have is a constant stream of light that appears to you as a continuous image of the approaching ship. I think this should be another thread, though, because it is far from why nature forms spheres in certain cases.

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Thanks. It does actually make me feel a little dumb and confused because my physics learning has not been academic the way other people's has been.

I apologize if my response made it seem like I am condescending. I didn't mean it that way. I was slightly frustrated for not understanding you, so my questions were actually meant to guide you towards helping me understand what you meant, not to rub it in your face.

The fact you kept repeating the same incorrect definition made me think you didn't understand me in the first place, so I kept repeating it in different ways. I didn't mean to be rude.

And by the way, the links I supplied are really for your benefit; the wiki page has a lot of really good info on how relativity works and how the transformation from frame to frame is done. It's basic math, so it's not as intimidating if you don't have "high level" math.

Also, one more thing: You need to realize that you're asking for answers about high level physics. High level physics is often not intuitive, and involves high level concepts. They're *hard* to simplify, and sometimes, quite honestly, almost impossible to simplify without losing context or accuracy. I'm trying - and many other physicists on the forum often say the same and encounter the same problem -- but you have to give us a bit of leeway here. You can't expect a subject to be overly simplified but also accurate when the concept is high level and sometimes requires also high level math to TRULY understand the source of.

I felt like you're not cooperating with me; if I tell you that a term makes no physical sense and you keep repeating it in your question, it doesn't really help me help you understand what physics actually says rather than what you think it says. This isn't against you personally, but you need to try and understand things from that perspective. It's difficult to explain something without cooperation.

Of course I want to know when I've misinterpreted some concept by taking it out of context, but I think of "wavelength" and "frequency" as very empirically tangible terms.

They are. You just defined them in a language-manner rather than in a physical manner. I gave you the physical definition. In a physical context, that's what we use otherwise nothing makes sense.

The length of a wave is another name for its frequency, if it is traveling at a fixed speed. "Frequency" literally means how frequent (how often) a wave passes and if more waves pass in the same period, their length has to necessarily be shorter.

That is an okay way to imagine it, but when you encounter a conceptual problem like you had initially, it's NOT an accurate description and it's what increases your confusion.

Wavelength and Frequency depend on one another and are related, but they're not the same. Also, the word "Frequency" might mean what you just said when it is spoken in conversations, but in PHYSICS, it is not that.

There are quite a number of terms that are used differently in common language than they are used in physics. As you've seen with Janus' replies to me, the word "Halo" is used in common language differently than it is used in physics, which is resulting in misunderstanding (like the one I had with regards to Dark Matter).

For me to avoid misunderstanding, I need to understand the context used in PHYSICS. So I accept Janus' remark, forgo the definition I thought I knew and accept the physical one. If I don't trust him (which I don't have to) I can look up the physical definition online, examine it, and use the actual accepted definition.

Sticking to the definition I think makes sense to me on the expense of the actual definition used in physics will not help me understand the physical concept. On the contrary, it will just make me more confused.

That's what happened with your definition of frequency. I am attempting to explain that frequency is NOT number of waves not because I don't like the way you imagine things, I attempt to correct this definition because when you look at it from the perspective of relativity (which is a physics concept) it makes no sense and confuses you.

On top of that, I personally don't know what you mean when you say that, so that also doesn't help with *my* attempts to figure out where your confusion lies.

The redshifting/blueshifting/dilation/contraction stuff throws off intuition and complicates the math (I assume because I don't follow the exact math that closely);

It actually doesn't complicate the math, but it may complicate the intuitive nature of the concept.

Here's the reason why I posted the Lorentz Transform link: I wanted you to see what details we need to make this transformation. This would show you that if I know the velocity of one frame relative to another I can make a transformation. The red- or blue-shift and length contraction and time dilation is a *RESULT* of this calculation.

If I understand your confusion correctly, you seem to think it's a detail you plug in (as in you need to know the blue/red shift in advance) -- it's actually a result of the movement. Of course, if you have the red/blue shift you can calculate the velocity, but the red/blue shift is a *result* of the relative movement.

For that matter, there will be a DIFFERENT length contraction from one reference to another than there is relative to any other frame.

When I took my first special relativity class we had a problem to solve with two spaceships and the moon. A man stands on the moon and two spaceships move one towards and one away from the man in two different speeds. The problem asked to solve for length contraction, time dilation and relative velocity of everyone from all three frames.

You ended up having 6 different relative velocities, 6 different relative length contraction, etc.

It's relative. They're all relative. They are a RESULT of the calculation....

but the logic seems to be pretty clear that if you speed up relative to a star and the light-waves always reach you at C, then the fact that you're intercepting the waves more frequently means that their frequency has increased.

Here's where I think your problem lies: You are not intercepting the waves more frequently. You're intercepting the "peaks" more frequently.

I think you might want to go over the (more basic, but very very similar) concept of the Doppler Effect.

The wave itself moves at the same velocity, but it is more "compact" (the peaks are closer together), so you get the frequency higher. Or, alternatively, it's more "elongated" so the peaks are further apart, and you get lower frequency.

You need to understand, when you use a definition that makes no sense in physics but ask about a physics explanation it is confusing and, quite honestly, frustrating. You want an explanation in the context of physics, there's no reason why you can't use the definitions in that context. I'm all for helping you imagine or conceptualize ideas, but we have to speak a common language or we really won't understand each other at all.

Likewise, since time is measured the same vis-a-vis light in all situations, that also means that a second's worth of what you measure as x-rays emitted from the star are going to equal a longer time-period of, say, infrared rays from the perspective of an observer in orbit around the star.

Yes, that's a good way of looking at it. Spacetime and the speed of light are related. In fact, the speed of light (measured in meters per second, usually), is actually not a "basic unit of space" but rather a conversion of spacetime. The relationship to time is right, you can think of it as a result of the higher/lower frequency.

If you want to look at the equations, that's also how we calculate the red and blue shifts.

So while you are measuring your movement toward the star in the quantity of x-ray radiation received per minute at your time rate, the observer at the star would be measuring your movement as quantity of infrared waves emitted between your departure and arrival. You would both count the same number of waves emitted, only the wavelength of the waves and amount of time measured by each of you would be different.

You are confusing me again. No one would measure your movement as quantity of waves. If you are close enough, they will measure your velocity in the regular matter of how much time it takes you to go from point A to point B relative to me. That works if I know how far point A is from point B.

If I don't know the distance, then I can measure the frequency shift to see your velocity. So if I understand your definitions right, it would be "number of peaks" per second (which is not exactly frequency, but close enough) which is fine.

Just for the sake of proper definitions (and whoever may be reading this), frequency is not really "number of peaks" per second, but rather number of periods per second. In circular motion, it's number of revolutions per second. In waves, strictly speaking there are 2 "peaks" per period, one upwards and one downwards.

I just want to make sure we're clear.. If I understand you correctly, then saying "number of peaks" is not physical and I would very much rather we DON'T use it, but it is at least better than "number of waves" which can be easily confused with intensity or interference.

I know I may be a bitch on occasion (many.. occasions..) but this time, my insistence that we use proper definition is not just my lovely and loving character. It really does confuse the matter. A lot.

I suppose you could calculate the rate of gap-closing between any two objects by measuring the distance in number of light-waves received at two different moments and then giving the speed as the difference per amount of time you measured on your clock between the two wave-counts.

Again with number of waves, I shall replace it with "number of peaks" and then with "higher/lower frequency". Please tell me if this replacement is *not* what you mean.

It is true that you can measure an object's speed by calculating the frequency shift. The only thing you must have in order to do that is the *original* frequency. So for example in faraway stars we know what type of radiation is emitted by them, and hence what frequency they *SHOULD* have vs the frequency we see. We use the shift to calculate their velocity either towards or away from us.

Does this make it clearer? Is that what you meant?

Now I'm getting confused, though, because I'm wondering when you would start and stop counting waves. If you start at the moment the image of the departing ship arrives, when do you stop? All you have is a constant stream of light that appears to you as a continuous image of the approaching ship. I think this should be another thread, though, because it is far from why nature forms spheres in certain cases.

That's why you don't "count waves", lemur.

What you count is how many revolutions / periods there are in a second, and for that it doesn't MATTER when you start or finish counting. All I need to do is start counting revolutions and then stop after EXACTLY one second. I then have the frequency. 10 Hz is translated directly into 10 1/second where 1/second is "per second". Hence, 10Hz is in fact 10 revolutions per second.

You don't have to count ALL the peaks that exist, just how many fit in one second.... hence, it doesn't matter how many peaks there are in general but only what is the frequency of that particular wave.

Lastly, we often simplify things for the sake of understanding the basics. But when you're in space there actually ARE MORE than just "one wave" coming at you. "Number of waves" is confusing because it may imply that there are a number of waves - each with a different frequency or phase - that intersect. That creates interference and all sorts of fun things we can calculate, and create a whole NEW wave that is the interference of 2 or more waves.

So.. please... I'm not being just annoying for the sake of being annoying. Please stop saying "number of waves". It's not right and it's confusing.

~mooey

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Also, one more thing: You need to realize that you're asking for answers about high level physics. High level physics is often not intuitive, and involves high level concepts. They're *hard* to simplify, and sometimes, quite honestly, almost impossible to simplify without losing context or accuracy. I'm trying - and many other physicists on the forum often say the same and encounter the same problem -- but you have to give us a bit of leeway here. You can't expect a subject to be overly simplified but also accurate when the concept is high level and sometimes requires also high level math to TRULY understand the source of.

I don't expect anyone to simplify anything beyond the level of complexity with which they understand it. Since I am not a professional physicist, though, I have the leeway to study the available knowledge in the interest of making my own intuitive conceptions of physical phenomena more robust. You could say I'm not so much doing physics as you would define it as I am developing my own natural-philosophical approach to understanding, explaining, and predicting physical phenomena. Although I can't always understand or fully appreciate the anti-intuitive total-math approach that some people really seem to like, I do like being able to mine little gems of insight when I can and incorporate those into my more intuitive picture - which I express in the event that others may recognize some misinterpretation I have made and correct me before I build further on it. I hope it doesn't bother you too much that I'm not trying to do physics in exactly the same way you or others do it.

I felt like you're not cooperating with me; if I tell you that a term makes no physical sense and you keep repeating it in your question, it doesn't really help me help you understand what physics actually says rather than what you think it says. This isn't against you personally, but you need to try and understand things from that perspective. It's difficult to explain something without cooperation.

Well, I have to cooperate to the extent that you are providing me with valuable information and I shouldn't make it difficult for you to do that. However, I can't get around the fact that I look at and understand things slightly differently than you do, or so it seems anyway.

They are. You just defined them in a language-manner rather than in a physical manner. I gave you the physical definition. In a physical context, that's what we use otherwise nothing makes sense.

Well, sometimes definitions are phrased in a way to privileges one type of application and obscures another. If your definition is mainly geared toward the mathematics of specific equations, it may not be as robust in terms of qualitative-reasoning about the logic of the model. E.g. with this redshift/blueshift stuff, you seem to be focussed mainly on calculating the parameters and variables to arrive at results. I am more interested in intuitively understanding what is happening when you accelerate relative to a stream of EM radiation/waves. The two approaches have to overlap because they both must ultimately describe the same phenomenon accurately, but that doesn't mean that they won't confound each other epistemologically in some ways.

That is an okay way to imagine it, but when you encounter a conceptual problem like you had initially, it's NOT an accurate description and it's what increases your confusion.

That's why I accept critique welcomingly and use it to rethink my initial conceptions in light of new information.

Wavelength and Frequency depend on one another and are related, but they're not the same. Also, the word "Frequency" might mean what you just said when it is spoken in conversations, but in PHYSICS, it is not that.

At some point in your post, it became clear to me that this whole miscommunication is due to the fact that when I use the word, "waves," you think I am talking about a collection of waves as a unit, whereas I'm using it as a plural noun. So when I say waves have a frequency, it literally means how frequently a wave intercepts its receiver, which in the case of light is the result of the speed of the waves and their (wave)length. Shorter waves arrive more frequently when they're traveling at the same speed as longer waves, no? That's not intuitive?

If I understand your confusion correctly, you seem to think it's a detail you plug in (as in you need to know the blue/red shift in advance) -- it's actually a result of the movement. Of course, if you have the red/blue shift you can calculate the velocity, but the red/blue shift is a *result* of the relative movement.

I don't know what you mean by "plug in as a detail." To me, redshift/blueshift is a doppler-type shift similar to that of sound-waves except with sound waves, the higher frequency is due to adding the velocity of the receiver to that of the waves. With light, the waves always travel at C so the increase in frequency is due to the fact that the same amount of energy has to arrive in a shorter period of time because the speed of time has shifted for the moving receiver. Red and blue light have different frequencies/wavelengths but the same speed, so a shift from red to blue involves a time-shift relative to the sender because the blue light is moving at the same speed as the red light that it used to be before you accelerated toward it. Does that description work in terms of your approach too?

When I took my first special relativity class we had a problem to solve with two spaceships and the moon. A man stands on the moon and two spaceships move one towards and one away from the man in two different speeds. The problem asked to solve for length contraction, time dilation and relative velocity of everyone from all three frames.

You ended up having 6 different relative velocities, 6 different relative length contraction, etc.

It's relative. They're all relative. They are a RESULT of the calculation....

Isn't that because they're all moving at different speeds relative to each other?

Here's where I think your problem lies: You are not intercepting the waves more frequently. You're intercepting the "peaks" more frequently.

I think you might want to go over the (more basic, but very very similar) concept of the Doppler Effect.

The wave itself moves at the same velocity, but it is more "compact" (the peaks are closer together), so you get the frequency higher. Or, alternatively, it's more "elongated" so the peaks are further apart, and you get lower frequency.

See, this is what I meant earlier. When you say "the peaks are closer together" you are talking about the distance between the peaks (wavelength) along a series of waves. So when blue light is shining on you, the waves (peaks) are more frequent because there are more of them per second (which is why they deliver more energy than shorter-wave light).

You need to understand, when you use a definition that makes no sense in physics but ask about a physics explanation it is confusing and, quite honestly, frustrating. You want an explanation in the context of physics, there's no reason why you can't use the definitions in that context. I'm all for helping you imagine or conceptualize ideas, but we have to speak a common language or we really won't understand each other at all.

Well, I understood what you meant when you said "peaks" instead of "waves" because I know that waves are described in terms of peaks and troughs (even though I'm not sure that EM waves have peaks and troughs, actually, though they do in wave theories where two peaks can amplify each other when they overlap or cancel each other out when a peak and a trough overlap - though I never understand how energy could possibly cancel other energy out without violating conservation of energy.

You are confusing me again. No one would measure your movement as quantity of waves. If you are close enough, they will measure your velocity in the regular matter of how much time it takes you to go from point A to point B relative to me. That works if I know how far point A is from point B.

If I don't know the distance, then I can measure the frequency shift to see your velocity. So if I understand your definitions right, it would be "number of peaks" per second (which is not exactly frequency, but close enough) which is fine.

Yes, I see this is where I frustrated you, because I'm thinking about it in a way that you see as non-standard and therefore not-allowed for a non-vested physicist (not that you would let me use that term to describe myself - not that I would want to fight to define myself as such). Still, I think it makes sense to simplify distance/time into simply the number of waves encountered/emitted during a journey, since spacetime varies according to the speed of the observer. In a sense, there is no distance between them EXCEPT the amount of waves and the amount of time measured for those waves by either observer. I mean, it's not like you can say that the distance in infrared waves, based on that wavelength is the correct one and the one measured in x-rays is different, since each measures the wavelength of the waves and time elapsed in their own frame, right? The emission-point observer will measure the traveller's distance as farther because they're counting infrared peaks and the moving traveller measures it as shorter because they're counting x-ray peaks. So what else would the distance and speed be relative to except the distance and time as measured by each observer in their own frame?

Just for the sake of proper definitions (and whoever may be reading this), frequency is not really "number of peaks" per second, but rather number of periods per second. In circular motion, it's number of revolutions per second. In waves, strictly speaking there are 2 "peaks" per period, one upwards and one downwards.

I just want to make sure we're clear.. If I understand you correctly, then saying "number of peaks" is not physical and I would very much rather we DON'T use it, but it is at least better than "number of waves" which can be easily confused with intensity or interference.

I understand your concern with not giving false impressions about how to model light waves, but is does it really make a difference in the context of redshift/blueshift frequency/distance/time variabilities?

I know I may be a bitch on occasion (many.. occasions..) but this time, my insistence that we use proper definition is not just my lovely and loving character. It really does confuse the matter. A lot.

How about we just call each of us rigorous and committed to staying true to our own way of doing things, but being concerned enough about communicating with others that we don't give up easily bridging gaps of difference in understanding?

What you count is how many revolutions / periods there are in a second, and for that it doesn't MATTER when you start or finish counting. All I need to do is start counting revolutions and then stop after EXACTLY one second. I then have the frequency. 10 Hz is translated directly into 10 1/second where 1/second is "per second". Hence, 10Hz is in fact 10 revolutions per second.

You don't have to count ALL the peaks that exist, just how many fit in one second.... hence, it doesn't matter how many peaks there are in general but only what is the frequency of that particular wave.

I thought of that. And you could also just measure the amount of energy received by a photocell and divide by the amount of energy of each wave at that frequency, I think. But what got me confused is how you choose two separate moments as starting and stopping points for counting. If you start counting when the ship departs, when do you stop counting except when it arrives?

Lastly, we often simplify things for the sake of understanding the basics. But when you're in space there actually ARE MORE than just "one wave" coming at you. "Number of waves" is confusing because it may imply that there are a number of waves - each with a different frequency or phase - that intersect. That creates interference and all sorts of fun things we can calculate, and create a whole NEW wave that is the interference of 2 or more waves.

So.. please... I'm not being just annoying for the sake of being annoying. Please stop saying "number of waves". It's not right and it's confusing.

I actually thought of that too but I couldn't explain it as clearly as you just did. I guess you would just have to look at a whole spectrum distribution from a star and compare it to the shifted version of the same spectrum to see how much you'd accelerated. Is that too easy a solution?

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Well, I have to cooperate to the extent that you are providing me with valuable information and I shouldn't make it difficult for you to do that. However, I can't get around the fact that I look at and understand things slightly differently than you do, or so it seems anyway.

What I am asking you is to consider that this might be so because you don't have all the information.

These are not concepts that can be summed up in a single forum thread.

If you really are interested in what things *really* are, you should open yourself and do a bit of research. No one is against personal interpretation, but you can't insist on a personal interpretation without understanding what the accepted interpretation is.

I recommend you read the concept of relativity, lorentz transform, doppler effect and special relativity a bit. It will help you understand why things are the way they are, and from THERE, you can try and reach your own conclusions.

Well, sometimes definitions are phrased in a way to privileges one type of application and obscures another. If your definition is mainly geared toward the mathematics of specific equations, it may not be as robust in terms of qualitative-reasoning about the logic of the model. E.g. with this redshift/blueshift stuff, you seem to be focussed mainly on calculating the parameters and variables to arrive at results. I am more interested in intuitively understanding what is happening when you accelerate relative to a stream of EM radiation/waves. The two approaches have to overlap because they both must ultimately describe the same phenomenon accurately, but that doesn't mean that they won't confound each other epistemologically in some ways.

My definitions are physical. Yours are lingual.

You are asking a question about the physics, you should at least try to use the proper language. Physics is empirical and language is not. The whole reason that physics uses rigid mathematical definitions is to prevent misunderstanding and make the terms clear cut and without a shred of doubt as to what they mean.

Because physics is empirical.

Isn't that because they're all moving at different speeds relative to each other?

Yes. It's because each frame is relative to each of the other frame.

See, this is what I meant earlier. When you say "the peaks are closer together" you are talking about the distance between the peaks (wavelength) along a series of waves. So when blue light is shining on you, the waves (peaks) are more frequent because there are more of them per second (which is why they deliver more energy than shorter-wave light).

Sure.

Well, I understood what you meant when you said "peaks" instead of "waves" because I know that waves are described in terms of peaks and troughs (even though I'm not sure that EM waves have peaks and troughs, actually, though they do in wave theories where two peaks can amplify each other when they overlap or cancel each other out when a peak and a trough overlap - though I never understand how energy could possibly cancel other energy out without violating conservation of energy.

You can be quite sure E/M waves have peaks and troughs in more than just theory. If you have doubt, you can go do your own little research about it. You can even measure the peaks and troughs at home in your own microwave. I have an experiment to show this in my site: http://www.smarterth...speed-of-light/

I understand your concern with not giving false impressions about how to model light waves, but is does it really make a difference in the context of redshift/blueshift frequency/distance/time variabilities?

Yes, you can't look at light as non-dual and expect to understand what goes on physically. Many of the effects are *due* to its behavior as a light/wave duality.

How about we just call each of us rigorous and committed to staying true to our own way of doing things, but being concerned enough about communicating with others that we don't give up easily bridging gaps of difference in understanding?

... I'm sorry, but that doesn't cut it.

You are trying to do your own physics without knowing what the actual physics says. That's not rigorous. It's insistent.

If you think you have better theories (which is just fine) you should at the very least first do the research as to what the current theory *says*. You can't expect to ask a question, get a relatively simplified answer (since I can't paste the entire of relativity, why it is the way it is, why we know it, where it came from and how we derive it in a single thread) and then use the simplified version to decide that your version of things is better.

It's not fair to the theories that are actually said by physics, don't you agree?

I thought of that. And you could also just measure the amount of energy received by a photocell and divide by the amount of energy of each wave at that frequency, I think. But what got me confused is how you choose two separate moments as starting and stopping points for counting. If you start counting when the ship departs, when do you stop counting except when it arrives?

This is another reason you have to treat light as dual. The energy is related to the photons (matter). Frequency is about its wave behavior.

I actually thought of that too but I couldn't explain it as clearly as you just did. I guess you would just have to look at a whole spectrum distribution from a star and compare it to the shifted version of the same spectrum to see how much you'd accelerated. Is that too easy a solution?

Not accelerated, moved. Special relativity is not about acceleration it's about velocity.

Other than that, yes.

~mooey

Edited by mooeypoo
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If you really are interested in what things *really* are, you should open yourself and do a bit of research. No one is against personal interpretation, but you can't insist on a personal interpretation without understanding what the accepted interpretation is.

I recommend you read the concept of relativity, lorentz transform, doppler effect and special relativity a bit. It will help you understand why things are the way they are, and from THERE, you can try and reach your own conclusions.

I do read about these things all the time. I don't just read forum posts and websites. I also read the books available at the library. I have read various less-known physicists as well as books by Hawking, Feynman, Planck, and Einstein. Hobby learning is an active process and the enjoyable part about it is that you don't have to follow someone else's curriculum. Reason can be your guide.

My definitions are physical. Yours are lingual.

You should not claim that the reason things you say are right is because they're physics and something else isn't. "Physics" is a general term that refers to a practically timeless approach to knowing how material physicalities work. It is as general a term as metaphysics. I understand that in academia, people are fond of teaching/learning fields as historically fixed cannons of scholarship and knowledge, but please acknowledge that that is not the only possible approach to knowledge. Just as you wouldn't like to be told that your metaphysics is not metaphysics because it doesn't follow some set cannon of philosophical writings, you shouldn't claim that my physical knowledge and analyses are completely wrong or invalid because it doesn't march in perfect lockstep with everything that is recognized in academic physics. As I say this, I want to be careful to note that I deeply value academic physics because it is my main source of insight for building my own understanding. That said, however, I don't like to be told I have to do things according to someone else's way or hit the highway, so to speak.

Also, everything written or spoken (i.e. communicated through symbols) is "lingual." So your physics and every other physics is also "lingual." If you want to claim that your physics agrees with empirical observation better than mine, that's a legitimate claim and of course I wouldn't want to hear where anything I said diverged from empirical data.

You are asking a question about the physics, you should at least try to use the proper language. Physics is empirical and language is not. The whole reason that physics uses rigid mathematical definitions is to prevent misunderstanding and make the terms clear cut and without a shred of doubt as to what they mean.

I try to use the most accurate language possible without betraying my own understanding. If I am certain that it is accurate to call light "EM waves" then I find it slightly less risky to say, "waves" then to venture into talking about the peaks and troughs of the waves since, although I typically think of waves as having peaks and troughs, the only model of EM waves I am familiar with describes them as alternating-direction electric and magnetic fields at perpendicular angles to each other. I could say "peak" and mean the oscillation of the wave in one direction and say "trough" to mean when it oscillates back in the other direction, but then there's a chance someone like Swanson will say that EM waves don't have peaks and troughs because that is a classical mechanical concept and those don't apply to QM. I try to stick with what will cause the least controversy, but then you criticize me using "wave" instead of "trough." If Capt. Ref had not have given me some leeway in calling them waves, how far would you or someone else have gone in demonizing me for terminology? I'm not stubbornly arguing that my terminology must be accepted. I'm just wishing that terminological mistakes or miscommunication could be noted without derailing the constructiveness of the substantive part of the discussion.

You can be quite sure E/M waves have peaks and troughs in more than just theory. If you have doubt, you can go do your own little research about it. You can even measure the peaks and troughs at home in your own microwave. I have an experiment to show this in my site: http://www.smarterth...speed-of-light/

My browser couldn't find the server, but it sounds interesting.

... I'm sorry, but that doesn't cut it.

You are trying to do your own physics without knowing what the actual physics says. That's not rigorous. It's insistent.

I'm insistent that there are different approaches to learning, but that goes for any field. No discipline has a monopoly on determining the appropriateness of any methodology or learning style. I'm not trying to avoid what "the actual physics says." I'm learning from it constantly.

If you think you have better theories (which is just fine) you should at the very least first do the research as to what the current theory *says*. You can't expect to ask a question, get a relatively simplified answer (since I can't paste the entire of relativity, why it is the way it is, why we know it, where it came from and how we derive it in a single thread) and then use the simplified version to decide that your version of things is better.

Please don't do this to people. Don't put people in competition with establish institutions. All that does is put subjugational pressure on them. I'm neither trying to compete with any other physics or subjugate myself to its authority. I am just developing my own understanding and discussing things I learn, how I understand them, and thoughts they evoke. That's what I would do in any classroom in any subject. It is active learning.

It's not fair to the theories that are actually said by physics, don't you agree?

How is it "not fair?"

Not accelerated, moved. Special relativity is not about acceleration it's about velocity.

Other than that, yes.

Yes, good point. Light can't accelerate or decelerate. "Moved" "shift" "compress" "expand" "dilate" "contract" are all better words. If any of them are misleading, feel free to explain why so I can strike those from my list of possible synonyms to avoid using the same words over and over.

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I fixed the link (got broken in copy/paste). Check it out.

How is it "not fair?"

Arguing against something you don't understand results in misrepresenting the ACTUAL theory while you're at it.

Without noticing it, lemur, that's what you're doing. Not only is that frustrating to fix (and results in the "where the heck do I start" reaction by most people) but is also a logical fallacy: Strawman.

It's not just unfair to the theory, it's unfair to the person trying to explain things.

~mooey

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I fixed the link (got broken in copy/paste). Check it out.

It still doesn't work.

Arguing against something you don't understand results in misrepresenting the ACTUAL theory while you're at it.

Maybe, but don't you see that if I don't understand HOW I am misunderstanding it, I have no basis for accepting your claim or anyone else's that I am? What's more, if you don't explain your reasoning about how your perception of my understanding differs from yours, how can I even know what it is you are perceiving as the gap between my understanding and your knowledge is?

Without noticing it, lemur, that's what you're doing. Not only is that frustrating to fix (and results in the "where the heck do I start" reaction by most people) but is also a logical fallacy: Strawman.

I know this feeling while dealing with people who can't/don't understand things I'm trying to explain. I will do my best to at least understand something before discussing it, but the problem is that everyone believes that they get something once they FEEL like they get it. It sounds like what you're saying is that I should submit my own authority to someone else's, like an authoritarian student-mentor relationship but I dislike that model of pedagogy. I prefer clear communication and leaving the student (in this case me) to have the ultimate say in whether something makes sense or not. You can teach students to relinquish their self-trust in favor of trusting others, but then they can't really reach a point of deep understanding because they're always busy checking if what they're saying matches their mentor's expectations instead of evaluating whether it makes sense for themselves.

It's not just unfair to the theory, it's unfair to the person trying to explain things.

Well, there has to be a way of "fairly" negotiating discrepancies in understanding and communication problems without anyone relinquishing their authority over their own comprehension.

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The link worked for me, but here it is again: http://goo.gl/eRgVf

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Lemur, a small yet STAGGERINGLY important point, advanced physics is not intuitive. It just isn't, the universe doesn't act how people expect it to. So trying to interpret it in such a way will just result in you being wrong and what you think will happen disagreeing with what does happen. The universe wins, always.

!

Moderator Note

Please endeavour to stay on topic!

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Lemur, a small yet STAGGERINGLY important point, advanced physics is not intuitive. It just isn't, the universe doesn't act how people expect it to. So trying to interpret it in such a way will just result in you being wrong and what you think will happen disagreeing with what does happen. The universe wins, always.

!

Moderator Note

Please endeavour to stay on topic!

I think I'm going to start a new thread on this to avoid going off topic with it. Since yours is such a common forthcoming claim, I think it merits discussion about what "intuitive" does or should ultimately refer to and to what extent comprehension can be described as either "intuitive" or something else, whatever that would be.

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