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Offline PmbPhy

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Problem website
« on: 07/08/2014 14:17:30 »
Typically there's one way that I've been using to determine whether a website is reputable or not and that's whether its created by a physicist and is under a .edu website, i.e. a university. If it's not then that doesn't mean that there's anything wrong with it so please don't get me wrong.

Yesterday I ran into a problem. I found the following comment here
http://violet.pha.jhu.edu/~wpb/spectroscopy/basics.html
Quote
We can complicate it by talking about interacting electric and magnetic fields, quantum mechanics, and all of that, but just remember--light is energy.
(underline is mine). Wow! This is an astrophysicist at John Hopkins University saying that light is energy rather than the correct statement that light "has" energy.

I guess this means that even highly reputable websites never really deserved that trust.


 

Offline UltimateTheory

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Re: Problem website
« Reply #1 on: 07/08/2014 18:08:22 »
Respectable (?) scientists, especially astrophysicists, when they manage to get to tv in programs like "Through the Wormhole with Morgan Freeman" are starting talking about parallel universes, multi universes, parallel (curled?) dimensions, time travel, dark matter, dark energy, Hawking radiation, string theory etc, etc. They are mentioned without any indications that they're just hypothesis..
And layman people are starting believing - "after all scientists were talking about it, so they must know what they are talking".

Quote
I guess this means that even highly reputable websites never really deserved that trust.

None website or scientists (including Nobel prize winners) can be fully trust without any objections.
 

Offline Ethos_

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Re: Problem website
« Reply #2 on: 07/08/2014 20:29:12 »
Respectable (?) scientists, especially astrophysicists, when they manage to get to tv in programs like "Through the Wormhole with Morgan Freeman" are starting talking about parallel universes, multi universes, parallel (curled?) dimensions, time travel, dark matter, dark energy, Hawking radiation, string theory etc, etc. They are mentioned without any indications that they're just hypothesis..
And layman people are starting believing - "after all scientists were talking about it, so they must know what they are talking".

Quote
I guess this means that even highly reputable websites never really deserved that trust.

None website or scientists (including Nobel prize winners) can be fully trust without any objections.

Once the earth was thought to be flat by "Scientists"
Once subatomic particles were thought to be indivisible by "Scientists".
Once causality was the defining nature of determinism by "Scientists".

Once a very smart man, John Stewart Mill said the following:

Quote..........."The more things change, the more they remain the same."

Dissatisfied with the scientific weather?
Just stick around my good friend.
The truth is surely out there,....but!
Some theories may fall in the end.

.......................................Ethos

« Last Edit: 07/08/2014 23:03:24 by Ethos_ »
 

Offline percepts

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Re: Problem website
« Reply #3 on: 07/08/2014 21:08:56 »
What is surly about the truth ?

The problem with media such as the web is that it is never properly proof read.
« Last Edit: 07/08/2014 21:11:03 by percepts »
 

Offline Ethos_

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Re: Problem website
« Reply #4 on: 07/08/2014 23:01:20 »
What is surly about the truth ?

The problem with media such as the web is that it is never properly proof read.
It appears I might have done a better job proof reading myself. But of course, surely the truth is out there.

And it appears that the spelling police have struck again as well. "Surly", cough, cough, we have better things to do than scrutinizing everyone's spelling. But then again, some are blessed with, cough, cough, different talents.
« Last Edit: 08/08/2014 01:17:45 by Ethos_ »
 

Offline UltimateTheory

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Re: Problem website
« Reply #5 on: 08/08/2014 00:36:46 »
But of course, surely the truth is out there

Ethos, I agree with you.

There is only one version of reality, one version of Universe. Interpretation can vary from theory to theory, but it doesn't change Universe.

That's how I created mine unified theory, which is unifying the all particles to sub-particles the all others (photons, electrons, positrons, muons, pions, kaons, protons, neutrons etc. etc) are made of.
« Last Edit: 08/08/2014 00:39:29 by UltimateTheory »
 

Offline Ethos_

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Re: Problem website
« Reply #6 on: 08/08/2014 01:04:14 »
Wow! This is an astrophysicist at John Hopkins University saying that light is energy rather than the correct statement that light "has" energy.

I guess this means that even highly reputable websites never really deserved that trust.
I agree Pete, I've been victimized for trusting what I thought were reputable sources several times here lately. And I also agree that light "has" energy because the photon is a particle/wave. Only Mass is transmutable into Energy, not Matter. The equation E=mc^2 only describes the conversion of Mass into Energy and not the conversion of Matter into energy. This is a common misunderstanding about the nature of these conversions.

Because the photon is Matter, it is not proper to say that it is Energy.
Mass and Matter are not the same thing. Matter can have Mass/Energy but Matter is not Mass/Energy.
« Last Edit: 08/08/2014 01:08:00 by Ethos_ »
 

Offline chiralSPO

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Re: Problem website
« Reply #7 on: 08/08/2014 01:31:20 »
When photons are emitted and absorbed, is that the creation or destruction of matter (not mass)?
 

Offline Ethos_

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Re: Problem website
« Reply #8 on: 08/08/2014 03:21:05 »
When photons are emitted and absorbed, is that the creation or destruction of matter (not mass)?
No..............Matter can change from one form to another.

Example: Electron Positron annihilation produces photons. Photons are just another form of Matter, they are not mass/energy.

Note; I think it proper to point out that I prefer the term "mass/energy" instead of referring to one or the other as mass or energy. The reason for this is; Matter, in virtually every case contains both relationships. And because Mass and Energy are basically interchangeable, they can be dealt with as different aspects of the same thing.

The mass/energy that the electron and positron possessed is now transferred to the photons. Where in the case of the electron and positron, the mass/energy was represented by mass predominately, that mass is now converted to mostly energy remembering that the photon is virtually massless. I don't say totally massless because that presumption has yet to be proved conclusively.

 

Offline PmbPhy

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Re: Problem website
« Reply #9 on: 08/08/2014 03:21:48 »
Quote from: Ethos_
Only Mass is transmutable into Energy, not Matter. The equation E=mc^2 only describes the conversion of Mass into Energy and not the conversion of Matter into energy. This is a common misunderstanding about the nature of these conversions.

Because the photon is Matter, it is not proper to say that it is Energy.
Mass and Matter are not the same thing. Matter can have Mass/Energy but Matter is not Mass/Energy.
The only thing that can be converted is the form of the matter and the form of the energy. Energy and (relativistic) mass is a constant always.
 

Offline evan_au

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Re: Problem website
« Reply #10 on: 08/08/2014 12:03:52 »
Quote from: Ethos_
the photon is virtually massless. I don't say totally massless because that presumption has yet to be proved conclusively.
Maybe not conclusively proven, but a massless photon is a pretty basic assumption in the theory of relativity.

If the photon had rest mass, then according to relativity, it would take an infinite amount of energy to accelerate it to reach the speed of light in a vacuum. (Of course there are scenarios where light travels slower than the speed of light in a vacuum - such as when light is travelling through media such as air or water..)

Perhaps Ethos_ is thinking about neutrinos? Neutrinos are known to have a very small mass - but its mass is so small that it hasn't been accurately measured. Neutrinos travel very close to the speed of light - and a small equipment malfunction in the Gran Sasso experiment made it look like they were travelling slightly faster than the speed of light.
 

Offline PmbPhy

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Re: Problem website
« Reply #11 on: 08/08/2014 15:11:27 »
Quote from: Ethos_
the photon is virtually massless. I don't say totally massless because that presumption has yet to be proved conclusively.
Maybe not conclusively proven, but a massless photon is a pretty basic assumption in the theory of relativity.
That's a postulate from quantum theory. If you're talking about photons in concert with relativity then you're talking about quantum electrodynamics.

Elementary particle physics complicates things a bit more. Do you have the textbook Introduction to Elementary Particles by David Griffiths? If not then download it from  here - http://bookzz.org/book/1021786/9f3ef3

Now turn to page 60 and read
Quote
Actually, the physical distinction between real and virtual particles is not
quite as sharp as I have implied. If a photon is emitted on Alpha Centauri, and
absorbed in your eye, it is technically a virtual photon, I suppose. However, in
general, the farther a virtual particle is from its mass shell the shorter it lives, so
a photon from a distant star would have to be extremely close to its “correct”
mass; it would have to be very close to “real.” As a calculational matter, you
would get essentially the same answer if you treated the process as two separate
events (emission of a real photon by star, followed by absorption of a real photon
by eye). You might say that a real particle is a virtual particle which lasts long
enough that we don’t care to inquire how it was produced, or how it is eventually
absorbed.
 

Offline chiralSPO

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Re: Problem website
« Reply #12 on: 08/08/2014 16:01:03 »
When photons are emitted and absorbed, is that the creation or destruction of matter (not mass)?

No..............Matter can change from one form to another.

Example: Electron Positron annihilation produces photons. Photons are just another form of Matter, they are not mass/energy.

Note; I think it proper to point out that I prefer the term "mass/energy" instead of referring to one or the other as mass or energy. The reason for this is; Matter, in virtually every case contains both relationships. And because Mass and Energy are basically interchangeable, they can be dealt with as different aspects of the same thing.

The mass/energy that the electron and positron possessed is now transferred to the photons. Where in the case of the electron and positron, the mass/energy was represented by mass predominately, that mass is now converted to mostly energy remembering that the photon is virtually massless. I don't say totally massless because that presumption has yet to be proved conclusively.

What about a photon emitted due to the relaxation of an excited atom?  There is no annihilation here, only a change in electronic state. What matter is converted into the photon?
 

Offline PmbPhy

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Re: Problem website
« Reply #13 on: 08/08/2014 16:16:39 »
Quote from: chiralSPO
What about a photon emitted due to the relaxation of an excited atom?  There is no annihilation here, only a change in electronic state. What matter is converted into the photon?
When an atom emits a photon its mass decreases due to its decrease in energy. Something is said to have more matter if it has more mass. Therefore a decrease in mass corresponds to a decrease in matter. The form of the matter changes from rest mass to an electromagnetic wave. Or you can say that the mass decrease of the atom corresponds to the creation of a particle which has relativistic mass. Sweet, huh? :)
 

Offline Ethos_

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Re: Problem website
« Reply #14 on: 08/08/2014 16:22:23 »
Quote from: chiralSPO
What about a photon emitted due to the relaxation of an excited atom?  There is no annihilation here, only a change in electronic state. What matter is converted into the photon?
When an atom emits a photon its mass decreases due to its decrease in energy. Something is said to have more matter if it has more mass. Therefore a decrease in mass corresponds to a decrease in matter. The form of the matter changes from rest mass to an electromagnetic wave. Or you can say that the mass decrease of the atom corresponds to the creation of a particle which has relativistic mass. Sweet, huh? :)
Thanks Pete for this accurate description. I think you've hit that curve ball right out of the park!
« Last Edit: 08/08/2014 16:23:57 by Ethos_ »
 

Offline chiralSPO

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Re: Problem website
« Reply #15 on: 08/08/2014 16:59:09 »
Quote from: chiralSPO
What about a photon emitted due to the relaxation of an excited atom?  There is no annihilation here, only a change in electronic state. What matter is converted into the photon?
When an atom emits a photon its mass decreases due to its decrease in energy. Something is said to have more matter if it has more mass. Therefore a decrease in mass corresponds to a decrease in matter. The form of the matter changes from rest mass to an electromagnetic wave. Or you can say that the mass decrease of the atom corresponds to the creation of a particle which has relativistic mass. Sweet, huh? :)

Thanks for the answer, that mostly makes sense.

I know I'm splitting hairs here, but I am genuinely curious on this point. If "Something is said to have more matter if it has more mass" then is matter not increased when energy is converted to mass? Or does one count only relativistic mass as matter, not rest mass?
 

Offline chiralSPO

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Re: Problem website
« Reply #16 on: 08/08/2014 17:02:21 »
And does that mean that a very hot plasma has more gravitational mass than the "same quantity" of cool gas? ie does making something hotter actually increase its gravitational mass, or is it just inertial mass?
 

Offline PmbPhy

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Re: Problem website
« Reply #17 on: 08/08/2014 18:38:12 »
Quote from: Ethos_
Thanks Pete for this accurate description. I think you've hit that curve ball right out of the park!
You're welcome my dear friend and thanks so much for those very kind words. They mean a lot to me. :)

Quote from: chiralSPO
Thanks for the answer, that mostly makes sense.
You're quite welcome.

Quote from: chiralSPO
I know I'm splitting hairs here, but I am genuinely curious on this point. If "Something is said to have more matter if it has more mass" ....
Please keep in mind that the term matter has never been very well defined. Einstein defined it as anything that has a non-zero energy momentum tensor is called "matter". Not everyone knows and/or agrees with that definition.

Quote from: chiralSPO
...then is matter not increased when energy is converted to mass? Or does one count only relativistic mass as matter, not rest mass?
Please recall what I said above: The only thing that can be converted is the form of the matter and the form of the energy. There is no change in the total amount of matter, mass or energy. Energy can never be converted to mass.

Please study the following article very carefully. When you've finished you'll have a better understanding that anybody else in this forum .... besides me of course.
Rotlf!!! See Does nature convert mass into energy? by Ralph Baierleina, Am. J. Phys. 75 4, April 2007, which is online at http://www.uaz.edu.mx/neutron/fm/literatura/artw/AJP75320.pdf
Quote from: Ralph Baierleina in American Journal of Physics
Just what did Einstein mean by “equivalence”? The Appendix gives my historical evidence; here I state only my conclusion. All things considered, I think it fair to say that, for Einstein in 1907, the “equivalence of mass and energy” meant a numerical proportionality between the two quantities. Inertia and energy remained distinct—though profoundly related — concepts. No subtle intrinsic identity of the two notions was proposed or intended.

Do you recall the example I gave a while back? I used an example in Nuclear Fission to describe how nuclear fission "releases" energy. It's at
http://home.comcast.net/~peter.m.brown/sr/nuclear_fission.htm

I recommend studying this one very carefully too. It shows you something that is rarely talked about in nuclear physics, i.e. the potential energy inside the nucleus. It also makes it clear just un-mysterious nuclear energy is by describing it in terms of classical mechanics, i.e. kinetic and potential energy with special relativity thrown in to explain the rest.
« Last Edit: 08/08/2014 18:42:39 by PmbPhy »
 

Offline PmbPhy

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Re: Problem website
« Reply #18 on: 08/08/2014 18:44:37 »
Quote from: chiralSPO
And does that mean that a very hot plasma has more gravitational mass than the "same quantity" of cool gas? ie does making something hotter actually increase its gravitational mass, or is it just inertial mass?
Absolutely! Gravitational mass has the same value as inertial mass. This is talked about in GR textbooks. It's an important point. It was very wise of you to raise the subject. My compliments to the chef! :)
 

Offline jeffreyH

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Re: Problem website
« Reply #19 on: 08/08/2014 19:26:24 »
Quote from: chiralSPO
And does that mean that a very hot plasma has more gravitational mass than the "same quantity" of cool gas? ie does making something hotter actually increase its gravitational mass, or is it just inertial mass?
Absolutely! Gravitational mass has the same value as inertial mass. This is talked about in GR textbooks. It's an important point. It was very wise of you to raise the subject. My compliments to the chef! :)

What I like Pete is how you bring forward the finer points. Sometimes it is the lack of detail that confuses people wanting to learn. This precision does seem to be lacking in general with much of the information relating to physics online.
 

Offline PmbPhy

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Re: Problem website
« Reply #20 on: 08/08/2014 19:36:23 »
Quote from: jeffreyH
What I like Pete is how you bring forward the finer points. Sometimes it is the lack of detail that confuses people wanting to learn. This precision does seem to be lacking in general with much of the information relating to physics online.
Thanks, Jeff. That's a very kind thing of you to say. You, sir, are a gentleman, a scholar and a good judge of legs wine and women. :)
 

Offline PmbPhy

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Re: Problem website
« Reply #21 on: 09/08/2014 03:24:01 »
Ohanian explains the concept of light having mass nicely in his book Einstein's Mistakes. See http://www.einsteinsmistakes.com/deep_questions_6.html
Quote
Is an electromagnetic field or an electromagnetic wave, such as a radio wave, a form of matter?

Electromagnetic fields and waves have energy, and hence have mass. They therefore must be regarded as a form of matter. This view was first introduced by Einstein when he formulated his theory of gravitation: “We make a distinction hereafter between ‘gravitational field’ and ‘matter’ in this way, that we denote everything but the gravitational field as ‘matter.’ Our use of the word therefore includes not only matter in the ordinary sense, but the electromagnetic field as well.”  If we think of solids, liquids, gases, and plasmas as the first four states of matter, then electromagnetic fields and waves are the fifth state of matter.
(Underline is mine)
 

Offline jeffreyH

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Re: Problem website
« Reply #22 on: 09/08/2014 17:00:26 »
Hi Pete

From the site you referenced this is of most interest to me in my current research.

http://www.einsteinsmistakes.com/deep_questions_6.html

"What is spin?

Although spin is usually thought of as a quantum-mechanical phenomenon, it first made its appearance in classical physics, when it was recognized that a circularly polarized electromagnetic wave carries not only energy but also angular momentum. The ratio of energy to spin is equal to the angular frequency of the wave, exactly as expected for a photon, for which the ratio of energy to angular momentum is also equal to the angular frequency. The angular momentum of the circularly polarized wave arises from a flow of energy within the wave—in the peripheral part of the wave, the energy has a helical flow, that is, a circulation around the axis of the wave in addition to the main flow along the direction of propagation of the wave. More generally, all relativistic wave fields, except for scalar waves, carry both energy and angular momentum. Thus, the spin of an electron is merely the angular momentum arising from the helical flow of energy within the Dirac wave field that describes the electron quantum-mechanically."
 

Offline percepts

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Re: Problem website
« Reply #23 on: 12/08/2014 18:34:00 »
What is surly about the truth ?

The problem with media such as the web is that it is never properly proof read.
It appears I might have done a better job proof reading myself. But of course, surely the truth is out there.

And it appears that the spelling police have struck again as well. "Surly", cough, cough, we have better things to do than scrutinizing everyone's spelling. But then again, some are blessed with, cough, cough, different talents.

I couldn't agree more but sometimes spelling errors have a humorous result. My apologies for making the mistake of thinking you would have a sense of humour.
« Last Edit: 12/08/2014 19:11:39 by percepts »
 

Offline Ethos_

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Re: Problem website
« Reply #24 on: 14/08/2014 22:46:32 »
I couldn't agree more but sometimes spelling errors have a humorous result. My apologies for making the mistake of thinking you would have a sense of humour.
Oh but I do enjoy good humor Mr. 'percepts', I think you're absolutely hilarious.
« Last Edit: 14/08/2014 22:50:22 by Ethos_ »
 

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Re: Problem website
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