Physics Discussion Thread

[Amber G.]

It seems a few people are confused beyond any hope ... trying to calculate density of stars and stuff like that.. what if some one tells them, or they read it any elementary book on stellar structure, that there are starts where the density is billions of time more than water... while some black holes can be lighter than air while others billion billion times denser than osmium.. .

[johneeG]

Refractive index does not change due to wave-length:

Wavelength and the Index of Refraction
Light travels as waves, with the wavefronts perpendicular to the direction of motion. In the animation shown here, the wavefronts are represented by the green parallel lines. The red arrow represents the direction of motion. As light moves from air into water, it not only slows, but the wavelength changes. The animation below illustrates how the wavelength becomes shorter in the denser medium of water. To replay an animation, click on "replay". Once you have viewed the first animation, click on "2" to continue.



Interestingly enough, the frequency of the waves does not change as the light moves from air to water. As we saw in the Review page, the wave's speed v is related to both the frequency f and the wavelength :
v = f.


Combining the above expression for velocity with the definition of index of refraction, we find a relationship between the wavelength = v/f in a medium and the wavelength 0 = c/f in vacuum:


In the above equation, the frequencies cancel because frequency does not change as light moves from one medium to another.

Link

This is the operative part:

In the above equation, the frequencies cancel because frequency does not change as light moves from one medium to another.

The ratio of wavelengths should be equal to refractive index.

So, wavelength of light in vacuum/wavelength of gamma ray(light in sun) = refractive index of sun

Wavelength of light is in nanometers = 10^-9.
wavelength of gamma rays is supposed to be picometers = 10^-12.

So, refractive index of sun = (10^-9)/(10^-12) = 10^3 = 1000.

So, according to the mainstream numbers. Density of sun is around 1.4 g/cm^3. Refractive index must be around 1000.

If refractive index is 1000, then the speed of light in sun must be:

refractive index of sun = speed of light/ speed of gamma rays(light in sun)

1000 = 300,000,000/x
x = 3,000,000 m/s.

If this is the speed of gamma rays(light) in sun, then it should take how much time to cover a distance of 696,000 *10^3 m?

speed = distance/time.

time = distance/speed.

time = (696,000 *10^3)/(3,000,000) seconds.

time = 696/3 seconds.

time = 232 seconds.

time = 232/60 minutes.

time = 3.8 minutes or 4 minutes.

But, they say that it takes 4000 years.

I made a mistake in these calculations. I assumed the frequency of the photons to be equal inside and outside the sun. But, since, they are called gamma rays inside the sun and gamma rays are supposed to be high frequency. The frequencies are also different.

This is the operative part:

In the above equation, the frequencies cancel because frequency does not change as light moves from one medium to another.

Speed of gamma rays in sun = wavelength * frequency.

wavelength of gamma rays is supposed to be picometers = 10^-12 m.
Gamma rays are supposed to be high frequency.
Frequency of gamma rays is supposed to be around 10^20 Hz.

Speed of gamma rays in sun = 10^-12 m * 10^20 Hz. = 10^8 m/s.

That means the speed of gamma rays inside the sun must be 100,000,000 m/s

The speed of light outside the sun is 300,000,000 m/s.

So, refractive index of sun:

refractive index of sun = (speed of light/frequency of light)/ (speed of gamma rays(light in sun)/frequency of gamma rays)

refractive index = { (300,000,000 m/s) / (4*10^14) /s} / { (100,000,000 m/s)/ (10^20 /s)}

refractive index = {0.00000075 m}/ {10^-12m}

refractive index = 75 * 10 ^4

Time taken by the gamma rays:
If the speed of gamma rays(light) in sun is 100,000,000 m/s, then it should take how much time to cover a distance of 696,000 *10^3 m?

speed = distance/time.

time = distance/speed.

time = (696,000 *10^3)/(100,000,000) seconds.

time = 6.96 seconds.

But, they say that it takes 4000 years.

[TSJones]

Vacuum transmits heat. . Time to move to GDF phijjiks dhaaga???

Heat transfer occur through conduction, convection AND radiation(as in EM radiation)

So, heat is not molecule vibration? And sun releases heat directly? And that sun's heat then travels through the vacuum of space?

Einstein explained this in Brownian Motion.

.......there is a whole section of science/astronomy based on sensing infrared em spectrum. the US is spending over $8 billion dollars on the James Webb Space Telescope and they plan on sending it beyond the dark side of the moon. Why? so that it can sense infrared em spectrum better!

finally, rattlesnakes in parts of the US make a very good living sensing infrared........

astronomers and rattlesnakes luuuurve infrared waves...........

[UlanBatori]

Wavelength of light is in nanometers = 10^-9.
wavelength of gamma rays is supposed to be picometers = 10^-12.
So, refractive index of sun = (10^-9)/(10^-12) = 10^3 = 1000.

Not so fast... wavelength in the middle of the solar spectrum is ~500 nanometers. "Green line" of usual lasers is ~ 515 to 540 nm.

From Prof. Wik-e-Pedia:

Gamma rays typically have frequencies above 10 exahertz (or >10^19 Hz), and therefore have energies above 100 keV and wavelengths less than 10 picometers (10^−11 meter)

Also says there that a typical time for an excited atomic nucleus to release a gamma photon is ~10^-12 seconds.
That is the number that our Physicists were so reticent about. Now we are on to something. Consider the implication of that: The diameter of an atomic nucleus is apparently of the same order of magnitude as the wavelength of a gamma ray. The time for interaction (between excitation and re-emission) is basically equal to the time for a million cycles of the wave. But does ALL of a photon interact with an atomic nucleus or does most of it just go around it like Caspar the Friendly Ghost going around someone? I have no idea when two Heisenberg Uncertain Principals try to step around each other in a hallway. Probably head-on collision and both fall down.

Also, what happens when an atomic nucleus is hit by a photon? Doesn't the photon have momentum? Does the nucleus sit still for the next million cycles? (million collisions)? Or does it get accelerated in short order to near the speed of light, so that when it emits, it is already 0.9 million wavelengths along the original trajectory of the photon? What happens to the Drunken Walk if the lamppost that the drunk walks into, moves 10 feet back with every collision?

So from the philosophical pov, all the confusion is because ppl are talking about a star which IS observable, and sticking to the Fallacies-e-EkPatthar, viz, constant speed of light. And we find that we really don't know such things as the interaction times of photons with matter in regions where mass/energy conversion is likely.

The answer that g reaches infinity at the Event Horizon is really not an acceptable one - that is the Sound Barrier fallacy. At the center of our own galaxy, just a few (million?) Light Years away, is the Galactic BH. Surely one can get some idea of the actual value at the event horizon, since the event horizon has a FINITE radius?

I am particularly eager to hear about the Air-Headed Black Hole.

[member_22733]

Around in circles we go.

Question: A nuclear core of a reactor melts down, how long before it completely cools back to solid metal and rocks.

[TSJones]

So from the philosophical pov, all the confusion is because ppl are talking about a star which IS observable, and sticking to the Fallacies-e-EkPatthar, viz, constant speed of light. And we find that we really don't know such things as the interaction times of photons with matter in regions where mass/energy conversion is likely.

OK, let's put the burden of proof on you Boss.

How does the photons speed back up when it hits vacuum after passing through a denser medium?

Heck, let's make it more real world. How do the photons speed back up after it passes through glass?

[rsingh]

Me think Gurus need a "Super Fiziks " thread and leave this thread alone for mortals like me who are who are intrigued by little daily life experiences. Why my dog need exact coordinate of Islamabad to answer the natures call? Why do we yawn? etc etc Salam.

[Amber G.]

Also small pooch

What happens to Van dear Waals equation in BH
Doe it hold
T must absolute zero
Volume will be zero
Only P will be infinite?
If there is no matter then how can P be perceived?


Chal better stick to strength of Materials rather than weakness of theory

Palmer,

Any good textbook of physics will explain it but in short -

Van der Wall equations, as good they may be, are for gases (or may be fluid) made out of molecules like that of ordinary gases. (Here, btw , one only consider Electromagnetic force and gravitational force is completely ignored which is ok since gravity is so much weaker than molecular forces)

BH is not made out of molecules and the VdW model makes no sense.. Here gravitational force dominates all other fundamental forces (EM).
Anyway for BH:
(T is NOT absolute zero.. (Check out "Hawkins radiation" )
(Volume can vary from very small to very large ( radius of SMBH in center of our own galaxy is thought to be more than a billion Km!)
for P, you may have to define what you mean. (In ordinary case of gases, the walls "feel" pressure because the molecules bounce against it -- that is why one can use KE of gas and get pretty good results like WvW equation)..

Hope this helps.

[Amber G.]

Me think Gurus need a "Super Fiziks " thread and leave this thread alone for mortals like me who are who are intrigued by little daily life experiences. Why my dog need exact coordinate of Islamabad to answer the natures call? Why do we yawn? etc etc Salam.

OTOH I think there are already too many threads in brf like "Astrology,Numerology,Palmistry,and Paranormal Sciences.", "Great Indian Political Drama " and "Positive news" where Gurus like JohneeG, and UB can post, brag about pseudo-science, insult others .. So hope this thread recovers and and we see more physics related conversation.

[Amber G.]

There is too much confusion in this thread. If AmberG can please come back and straighten this out it will certainly help.

Just to make it clear. Our sun is not a perfect black body, but an ideal reference black body since it is consistent and predictable.

As far as I understand, Blackbody mainly radiates heat. Sun mainly radiates light. So, how can the two be compared?

Blackbody is more of a concept (idealization of an object which radiates/follows SB law of radiation)..A hot object (like tandoor) may give "heat" if you touch it, but when one talks about Sun "radiating" .. you are not exactly touching the sun. Sun radiates EM waves (from x-ray to visible light to infrared to radio waves).. that energy is what earth receives when one talks about 600 watt of power per sq meter at earth.

......the sun is not uniformly dense through out it's volume. that is an accepted fact by scientists who understand fusion. therefore the speed of the gamma rays are not uniform inside the sun as they travel through various densities.

.

Yes, and that is consistent with all experimental data..As said before, not only density but temperature varies. The temperature varies from about 6000K to millions of degree inside. Similar values for density. All this information confirmed by observed gamma rays (EM spectrum) from earth.

As for Einstein, he didn't believe in black holes and quantum mechanics.

No, this is not true. It is as odd as saying Kasab was not Pakistani. These kind of statements are laughable.

Fact is, though Wheeler was first to coin the term "Black Hole", but Einstein General Theory of Relativity
is the one where the math, concept and theory came. ( Schwarzschild completed his work and it was published 1916 - This is the famous paper - "On the Field of Gravity of a Point Mass in the Theory of Einstein" ) -- So saying Einstein didn't believe in black holes is like saying India does not believe in New Delhi as being it's capital.

As to quantum mechanics, don't let pseudo knowledge - CT cloud simple facts.

Einstein's Noble prize was awarded for photo- electric effect. This is essentially proving that light energy comes in quantum.

Sure, there were some aspects of probabilistic QM which he was not comfortable with, and hope to develop a simpler/better foundation. I know all about his famous quote ("God does's play dice") but saying the he did not "believe" in QM is laughable.

PAM Dirac (Nobel prize and who worked closely with Einstein)is the one who is famous for uniting QM and Relativity (QED Theory).

(I have taken a course in Quantum Mechanics from Dirac, and his text book on Quantum Mechanics is a classic.)

[UlanBatori]

OK, let's put the burden of proof on you Boss.
How does the photons speed back up when it hits vacuum after passing through a denser medium?
Heck, let's make it more real world. How do the photons speed back up after it passes through glass?

Sorry, but the more I think about that the more my head hurts. Must be the rooh Afza. If photons have mass, isn't that infinite acceleration, requiring infinite force? Maybe it's NOT the same photon? I have made it clear before that the whole idea of electromagnetic wave propagation through vacuum makes no sense to me, so I plead ignorance.

Problem here is that the Physics Royalty don't really explain things, they just sneer at my ignorance and questions (or go complain to the Bouncers about my even being allowed in the club). So no, I can't prove anything, sorry.

[Amber G.]

Okay, I see there are some very LONG posts explaining refractive index theory here, so allow me to ask an old classic problem.

Now we all know that: (if you don't know this, just check out a reference such as) http://henke.lbl.gov/optical_constants/getdb2.html

X-ray refractive indices for quite a few metals are LESS than 1. Even our pure water (which for visible light have index about 1.3) for X-ray(near 30keV) has mu close to but LESS than 1 (about 0.99999974).

Doesn't this mean that x-ray photon travels faster than c???

Can some one explain this?
(Those who have heard it before and know the answer, please do not spoil the fun for others a day for two -- let others google/wiki or think and get their own answer, before one gives an explanation.)

[UlanBatori]

Oh, good! The night sky is going to become clear of stars in the future, leaving only glowing pieces of Space Junk to adorn the sky. From Wik-e-Pedia The Holiest:

Rules that apply to relative velocities in special relativity, such as the rule that relative velocities cannot increase past the speed of light, do not apply to relative velocities in comoving coordinates, which are often described in terms of the "expansion of space" between galaxies. This expansion rate is thought to have been at its peak during the inflationary epoch thought to have occurred in a tiny fraction of the second after the Big Bang (models suggest the period would have been from around 10−36 seconds after the Big Bang to around 10−33 seconds), when the universe may have rapidly expanded by a factor of around 1020 to 1030.[22]

There are many galaxies visible in telescopes with red shift numbers of 1.4 or higher. All of these are currently traveling away from us at speeds greater than the speed of light. Because the Hubble parameter is decreasing with time, there can actually be cases where a galaxy that is receding from us faster than light does manage to emit a signal which reaches us eventually.[23][24]

"Our effective particle horizon is the cosmic microwave background (CMB), at redshift z ∼ 1100, because we cannot see beyond the surface of last scattering. Although the last scattering surface is not at any fixed comoving coordinate, the current recession velocity of the points from which the CMB was emitted is 3.2c. At the time of emission their speed was 58.1c, assuming (ΩM,ΩΛ) = (0.3,0.7). Thus we routinely observe objects that are receding faster than the speed of light and the Hubble sphere is not a horizon." [25]

However, because the expansion of the universe is accelerating, it is projected that most galaxies will eventually cross a type of cosmological event horizon where any light they emit past that point will never be able to reach us at any time in the infinite future,[26] because the light never reaches a point where its "peculiar velocity" towards us exceeds the expansion velocity away from us (these two notions of velocity are also discussed in Comoving distance#Uses of the proper distance). The current distance to this cosmological event horizon is about 16 billion light-years, meaning that a signal from an event happening at present would eventually be able to reach us in the future if the event was less than 16 billion light-years away, but the signal would never reach us if the event was more than 16 billion light-years away.[24]

I think this Special Relative -Itty is what they call "Bent Poker" in Reno. Going on:

Apparent superluminal motion is observed in many radio galaxies, blazars (?? Cosmic VBIEDs?), quasars and recently also in microquasars. The effect was predicted before it was observed by Martin Rees[clarification needed] and can be explained as an optical illusion caused by the object partly moving in the direction of the observer,[27] when the speed calculations assume it does not. The phenomenon does not contradict the theory of special relativity. Interestingly, corrected calculations show these objects have velocities close to the speed of light (relative to our reference frame). They are the first examples of large amounts of mass moving at close to the speed of light.[28] Earth-bound laboratories have only been able to accelerate small numbers of elementary particles to such speeds.

[johneeG]

So, heat is not molecule vibration? And sun releases heat directly? And that sun's heat then travels through the vacuum of space?

Einstein explained this in Brownian Motion.

.......there is a whole section of science/astronomy based on sensing infrared em spectrum. the US is spending over $8 billion dollars on the James Webb Space Telescope and they plan on sending it beyond the dark side of the moon. Why? so that it can sense infrared em spectrum better!

finally, rattlesnakes in parts of the US make a very good living sensing infrared........

astronomers and rattlesnakes luuuurve infrared waves...........

So, please clarify: what is heat? Is it Infra-red waves or is it molecular vibration?

So from the philosophical pov, all the confusion is because ppl are talking about a star which IS observable, and sticking to the Fallacies-e-EkPatthar, viz, constant speed of light. And we find that we really don't know such things as the interaction times of photons with matter in regions where mass/energy conversion is likely.

OK, let's put the burden of proof on you Boss.

How does the photons speed back up when it hits vacuum after passing through a denser medium?

Heck, let's make it more real world. How do the photons speed back up after it passes through glass?

Density.

Me think Gurus need a "Super Fiziks " thread and leave this thread alone for mortals like me who are who are intrigued by little daily life experiences. Why my dog need exact coordinate of Islamabad to answer the natures call? Why do we yawn? etc etc Salam.

OTOH I think there are already too many threads in brf like "Astrology,Numerology,Palmistry,and Paranormal Sciences.", "Great Indian Political Drama " and "Positive news" where Gurus like JohneeG, and UB can post, brag about pseudo-science, insult others .. So hope this thread recovers and and we see more physics related conversation.

So far, as far as I know, I haven't even supported any theory(conspiracy or otherwise) on the this thread this time. I was just asking questions and how I think the numbers don't add up. You seem to be complaining too much even at that. You are invoking 9/11 or 26/11. What nonsense!

Appeals to authority don't count as physics, dude. Atleast, put up some counter arguments if you think you have a case. Provide some logical explanations. You are not even putting up anything. You seem to be hoping that your snobbery and bluster would be interpreted as some kind of superior knowledge. And then, you ironically lament about the quality of thread. Its amusing to watch your antics and pretense.

As far as I understand, Blackbody mainly radiates heat. Sun mainly radiates light. So, how can the two be compared?

Blackbody is more of a concept (idealization of an object which radiates/follows SB law of radiation)..A hot object (like tandoor) may give "heat" if you touch it, but when one talks about Sun "radiating" .. you are not exactly touching the sun. Sun radiates EM waves (from x-ray to visible light to infrared to radio waves).. that energy is what earth receives when one talks about 600 watt of power per sq meter at earth.

- Comparison between blackbody & sun:
Sun produces energy. Blackbody does not produce energy.
Sun radiates light mainly. Blackbody radiates heat mainly.
Sun does not absorb energy or if it does absorb energy, thats not its main function. Blackbody absorbs energy, thats its main function because thats the way it gains energy in the first place.

In short, Blackbody and sun are completely different in terms of creating energy and releasing energy as far as I can see. On what basis, are the two being called similar?

- I'll come back to heat later.

As for Einstein, he didn't believe in black holes and quantum mechanics.

No, this is not true. It is as odd as saying Kasab was not Pakistani. These kind of statements are laughable.

Fact is, though Wheeler was first to coin the term "Black Hole", but Einstein General Theory of Relativity
is the one where the math, concept and theory came. ( Schwarzschild completed his work and it was published 1916 - This is the famous paper - "On the Field of Gravity of a Point Mass in the Theory of Einstein" ) -- So saying Einstein didn't believe in black holes is like saying India does not believe in New Delhi as being it's capital.

As to quantum mechanics, don't let pseudo knowledge - CT cloud simple facts.

Einstein's Noble prize was awarded for photo- electric effect. This is essentially proving that light energy comes in quantum.

Sure, there were some aspects of probabilistic QM which he was not comfortable with, and hope to develop a simpler/better foundation. I know all about his famous quote ("God does's play dice") but saying the he did not "believe" in QM is laughable.

PAM Dirac (Nobel prize and who worked closely with Einstein)is the one who is famous for uniting QM and Relativity (QED Theory).

(I have taken a course in Quantum Mechanics from Dirac, and his text book on Quantum Mechanics is a classic.)

What nonsense, man! You are denying simple facts and then turn around and abuse and insults others! Einstein didn't believe in Black holes and quantum mechanics. Thats a fact. You may not like it. But, its still a fact. Yes, its true that both black holes and quantum mechanics use Einstein's work. But, its also true that Einstein himself didn't believe in these theories. Einstein actually wrote a paper in 1939 to disprove black holes. That paper was not accepted. Please read Einstein's biography if you don't believe me. Infact, Quantum mechanics and relativity apparently don't gel together. These are things that are quite well known. You obviously don't know much on the subject.

What a pretender!

[TSJones]

So, please clarify: what is heat? Is it Infra-red waves or is it molecular vibration?

I swiped this off the internet but lost the link.

it's impossible to perfectly insulate any object. Eventually, one of two things will happen: either the vibrating particles will be passed on to another object of lower thermal energy (conduction & convection), or the movement of the particles themselves create electromagnetic waves that radiate out at the speed of light and pass the heat into space or other objects (radiation).

Any charged particle (electrons, protons) that accelerate create electromagnetic radiation. So when little particles are bouncing around, both the visible ones and the invisible intramolecular movements, they are releasing this radiation. For room temperature, that radiation is in the infrared range (that's what an infrared camera is seeing). If you heat up an object in a flame, it eventually starts to glow, which is that vibrational energy turning into visible light. If you heat stuff up even further, you keep getting brighter light and smaller wavelengths. The sun is vibrating so much that they release very bright visible and ultraviolet radiation (and infrared).

[TSJones]

Sorry, but the more I think about that the more my head hurts. Must be the rooh Afza. If photons have mass, isn't that infinite acceleration, requiring infinite force? Maybe it's NOT the same photon? I have made it clear before that the whole idea of electromagnetic wave propagation through vacuum makes no sense to me, so I plead ignorance.

Mongolji, there is no comparison between your intellect and mine. Not even in the visible range. I am beginning to suspect that you are conducting some guerrilla street teaching ala Socrates who professed that he knew nothing; he only had questions.

It is forcing me to obtain knowledge that an ex-grunt would not have thought possible. In other words I suspect you are creating an ad hoc science street lab for dummies such as me.

Can you imagine me going to the local watering hole to start bending my elbow to do my 12 oz curls and I start babbling this argle bargle? it would confirm to people that I have lost my mind.

I seriously need to re-assess my barking on this thread.

[Viv S]

Sun radiates light mainly. Blackbody radiates heat mainly.

Say what?!

[UlanBatori]

Sun radiates light mainly. Blackbody radiates heat mainly.

Say what?!

True until it reaches some temp > ek-do hajaar degrees, hain? Then it becomes red-orange-yellow-white-blue-body? Don't shoot - just asking. Sun is approx a yellow star, isn't it? Soon 2 become orange and then Commie at which point ppl will quit about Anthropogenic Climate Change and conduct (brief) demonstrations against the Sun outside the (Black, Charred) House?


TSJi: Hu, ME? Guerrilla war? But I do have to admit that what was a pastoral Mutual Admiration Society thread with comfortably unquestioned assumptions like "everything travels slower than light" and "acceleration reaches infinity at Event Horizon" and "Random Drunken 4000 - 171,000 Year Walks" (all 3 now seen 2 b dud TOWs?) has become more like that bar u were talking about. So much more fun.

BTW, last November (or was it the year b4? time flies) I attended a lecture by a Nobel Prize winner at a college in Bawstun. Truly impressive. But I asked them what they taught in freshman physics these days, and admitted that I learned Bohr Model, Schrodinger's Equation (or was it Cat?) etc. They said:

Hmm! That's pretty much it.

So I am not **THAT** enamored of all this new-fangled stuff.

[Bade]

Oh this thread is not gonna last long at this rate....if there is any out gassing anywhere in the universe, it is clearly visible here...lot of heat (infra dig) and smoke...under the guise of logic...and refusal to learn when told or explained clearly by someone who knows.

AmberG, I can understand your frustration. Hope your classes are not filled with istudents with super calibre at display here....disruptive...nay...what is the term used for that...trolling ! Yes of course....

[sudarshan]

Time taken by the gamma rays:
If the speed of gamma rays(light) in sun is 100,000,000 m/s, then it should take how much time to cover a distance of 696,000 *10^3 m?

speed = distance/time.

time = distance/speed.

time = (696,000 *10^3)/(100,000,000) seconds.

time = 6.96 seconds.

But, they say that it takes 4000 years.

Is this a serious post, or am I missing something? I thought the reason why sunlight takes 4000 years to get to the surface from the center, is because of the mean free path, not the refractive index? It's the same phenomenon as the "drunkard's walk," look it up (assuming your post wasn't in jest or something). Statistically, with a "drunkard's walk - related phenomenon," the distance from the initial point will increase as the square-root of the time.

It's the same reason why traveling one km in peak hour Chennai traffic takes hours, while on a superhighway you can do the same distance in less than a minute.

[UlanBatori]

c what I mean - same things being repeated. This must be what R. Tagore had in mind when he cautioned against it:

...Where the clear stream of UBCN reason has not been lost in random walks in the dreary sands of mindless equation-quoting habit

But the Chennai traffic vs. superhighway is a good analogy. Take a Florida superhighway, where there are Toll Booths every kilometer. It takes 1 minute to traverse 1 km (incl. finite acceleration times, which was the other source of distress here). But it takes 30 seconds to go through a toll booth. So now it takes 1.5 minutes to go 1 km.

Now what happens if there is one Toll Booth every 100 m instead over every km? Baaad! 6 minutes per km, assuming very fast acceleration and deceleration.

What if there is one every 10m? 55 minutes per km, approaching Bangalore (old) Airport Road. This is what they claim is what happens inside the sun, discounting the Random walk. Interaction time ~10^-12 seconds, mean free path only a few centimeters.

Now what happens if one car goes in and it is another that comes out? Still takes 30 seconds per changeover.

Now what happens if Incident car slows down only by transferring momentum to the toll booth? Toll booth is now moving at 30 kmph when the other car is Emitted. But some distance has been gained during the process, and the Emitted Car comes out at 30kmph, not zero, to accelerate to 60+. So overall time to go 50 km is brought down by this last model.

Since there is a preferred direction for the random motion, and since gamma ray photon and Toll Booth are of similar size (and mass?), the Random Walk is definitely not the right model for these: the Incident Cars don't go off at 90 degrees or 180 degrees to the original direction, but basically along the same direction. This last fact is verified in lasers (Light Amplification by Stimulated Emission of Radiation). The stimulated emission photons, unlike random emission, are generally along same vector as the incident photon. If that were not the case, resonator lengths would have nothing to do with resonant frequency! LASERs and MASERs would be impossible!

HOWEVER, if the Toll Booths are all like "Express Card" and allow Cruise Lane operation, then there is NO delay due to the booths, even though there is an "Interaction". Or if they were like a shunting yard, the Incident Photon would come in and transfer momentum entirely and instantaneously to the photon waiting to leave inside there with no delay.

So these may be the reasons why the Random Walk Model is called the Drunken Physicist Model. It does not make sense though it talks a lot.

[Amber G.]

Few comments: (If interested, please read as there may be some physics related stuff below)

As for Einstein, he didn't believe in black holes and quantum mechanics.

No, this is not true. [.. Einstein General Theory of Relativity
is the one where the math, concept and theory of Black Hole came. ( Schwarzschild completed his work and it was published 1916)

As to quantum mechanics, don't let pseudo knowledge - CT cloud simple facts.

Einstein's Noble prize was awarded for photo- electric effect. This is essentially proving that light energy comes in quantum.

Sure, there were some aspects of probabilistic QM which he was not comfortable with, and hope to develop a simpler/better foundation. I know all about his famous quote ("God does's play dice") but saying the he did not "believe" in QM is laughable.

PAM Dirac (Nobel prize and who worked closely with Einstein)is the one who is famous for uniting QM and Relativity (QED Theory).

(I have taken a course in Quantum Mechanics from Dirac, and his text book on Quantum Mechanics is a classic.)

What nonsense, man! You are denying simple facts and then turn around and abuse and insults others! Einstein didn't believe in Black holes and quantum mechanics. Thats a fact. You may not like it. But, its still a fact. Yes, its true that both black holes and quantum mechanics use Einstein's work. But, its also true that Einstein himself didn't believe in these theories. Einstein actually wrote a paper in 1939 to disprove black holes. That paper was not accepted. Please read Einstein's biography if you don't believe me. Infact, Quantum mechanics and relativity apparently don't gel together. These are things that are quite well known. You obviously don't know much on the subject.

What a pretender!

Correct me if I am wrong, but my 10 sec google search points me that your "Einstein Denied Black holes and 1939 paper may have come from this wiki page:
https://en.wikipedia.org/wiki/Einstein% ... lack_holes
(I noticed that that wiki article (with multiple notation of ".[citation needed]" .. ditto for QM part which comes below that wiki article (again with "citation needed" comment).
Is that what makes it a fact? ???
OTOH, as I have said,

Einstein Nobel prize: Please check the Nobel citation: (This is explained only by "quantum physics")

(Folks please do the checking.. there is much more to learn here..and definitely worth your time..it is not
scoring a debating point)
http://www.nobelprize.org/nobel_prizes/ ... ates/1921/

The PE effect for his Noble Prize: (From wiki - as good a source as any)

...To make sense of the fact that light can eject electrons even if its intensity is low, Albert Einstein proposed that a beam of light is not a wave propagating through space, but rather a collection of discrete wave packets (photons), each with energy hf. This shed light on Max Planck's previous discovery of the Planck relation (E = hf) linking energy (E) and frequency (f) as arising from quantization of energy. The factor h is known as the Planck constant.
-(Sears,Zemansky, Young University Physics . 843–844)

You can not explain it using classical physics so Einstein has to use Quantum Physics.

As to "Quantum mechanics and relativity apparently don't gel together."
(Really Really???)

Tell that to Noble committee. who awarded noble to PAM Dirac's for see... Nobel citation: (Please do read it)
http://www.nobelprize.org/nobel_prizes/ ... facts.html

Formulated a Fully Relativistic Quantum Theory

During the intense period 1925-26, quantum theories were proposed that accurately described the energy levels of atoms. However these equations should be adapted to Einstein's theory of relativity. In 1928 Paul Dirac managed to formulate a fully relativistic quantum theory. The equation gave solutions that he interpreted as being due to the existence of a particle corresponding to the electron, but of positive charge. This particle, the positron, was later found experimentally.

PAM Dirac was a very close colleague of Einstein and along with Einstein, is considered one of the greatest mind.

As I told here (long ago in this thread too) I have taken a course of QM with Dirac, even taken walks with him about which I think I wrote about in this dhaga long time ago.)

But, its also true that Einstein himself didn't believe in these theories..

How do you know what Einstein believed? Did you talked with him? .. just curious. Did you talk with anyone who knew what Einstein believed? Did Einstein write any paper where he said "he does not believe in QM"? etc..

OTOH I have read quite a bit of Einstein's work from original papers, have spent years (if not decades) studying some of the stuff and have even read a few of his biographies too. I have also have come into contact with many who worked with Einstein closely ..

So, I will say those stories of Einstein not believing in quantum theory are highly exaggerated.

[Bade]

The stimulated emission photons, unlike random emission, are generally along same vector as incident photon. If that were not the case, resonator lengths would have nothing to do with resonant frequency! LASERs and MASERs would be impossible!

I am not sure of the underlined part being true at all. In a working laser there are reflectors at both ends....madrassa model....stimulated emission does not mean photons are emitted in a particular direction in space or in the medium. This is true even for simple scintillating materials. Hence great care is taken to avoid light leaks to keep the photon collection efficiency high...not just to keep the outside ambient light out and not contaminate your signal in the material inside..

[Amber G.]

This post can be ignored if you are familiar with black body radiation.

Good points below. Expanding a small but important point which it seems is the reason for confusion among some. Hoping that it will be useful to some. I am editing the quote for brevity.

[for heat transfer to occur] either the vibrating particles will be passed on to another object of lower thermal energy (conduction & convection), or the movement of the particles themselves create electromagnetic waves that radiate out at the speed of light and pass the heat into space or other objects (radiation).

Any charged particle (electrons, protons) that accelerate create electromagnetic radiation. So when little particles are bouncing around, both the visible ones and the invisible intramolecular movements, they are releasing this radiation. For room temperature, that radiation is in the infrared range (that's what an infrared camera is seeing). If you heat up an object in a flame, it eventually starts to glow, which is that vibrational energy turning into visible light. If you heat stuff up even further, you keep getting brighter light and smaller wavelengths. The sun is vibrating so much that they release very bright visible and ultraviolet radiation (and infrared).

(Considering a black body in thermal equilibrium emitting electromagnetic radiation also called black-body radiation -- Black body is idealized concept - see note below )

- Strictly speaking - All bodies (as they are about absolute 0 temp) radiate heat in all frequencies (or wavelengths)..
- The total energy radiated per unit of area is proportion to T^4. (times e which is 1 for BB)
- The spectrum of the radiation is emitted according to Planck's law, meaning that it has a spectrum that is determined by the temperature alone (not by the body's shape or composition ityadi)
- Higher the temperature, higher the frequency (lower wavelength) of the median of the spectrum of the curve (or the most prop. value)

This means everything (from a tree, to a snow ball to a human to the surface of the sun) emits radiation.... (There was a old physics problem I put here - see problem 1 viewtopic.php?p=1521388#p1521388). The total energy radiated per unit area is proportional to T^4. While a tree (or a human being at) 300K may emit most of its energy in infrared spectrum, Sun (6000) does in visible range. Sun also radiates in infra-red, radio waves even x-rays or gamma rays.. (Ditto for you.. yes, you do emit in x-ray range but is so low energy that one can neglect - most of what can be detected is in infra-red range )

***
A black body is a concept - idealization of a physical body that absorbs all EM radiation, (frequency, direction etc does not matter).

A black body in thermal equilibrium ) emits electromagnetic radiation called black-body radiation. The radiation is emitted according to Planck's law ( This means that it depends only on temperature and not on shape, or composition etc).. this is distributed in all the directions equally.

In practice, a kajol (lamp-black) coating makes a very good approximation of a black body for experiments in a typical physics lab, but if you are looking for one which absorbs radar perfectly, you may like to consider a coating which they do on radar evading planes.

[UlanBatori]

In a working laser there are reflectors at both ends....madrassa model....stimulated emission does not mean photons are emitted in a particular direction in space or in the medium. This is true even for simple scintillating materials. Hence great care is taken to avoid light leaks to keep the photon collection efficiency high...not just to keep the outside ambient light out and not contaminate your signal in the material inside..

Badeji: Argon ion laser is simply a glass tube with a mirror or prism at one end and a mirror with transparent hole (non-silvered surface I mean) at the other. Filled with low density argon that is ionized, I suppose. Pretty basic Plane Parallel Fabry-Perot Resonator, except that it's axisymmetric. Mode 100(?) aka doughnut/gaussian is simply a beam that bounces back and forth hajar-karod times b4 it is allowed to partially exit through the hole. If random walk was very significant, the mirror and prism would not be much more effective at reflecting, than the very transparent glass tube, hain? Of course other modes jump all over the place. You can actually leave the thing operating with the cover off if you defeat the safety interlock (DO NOT TRY THIS AT HOME!! EYE PROTECTION REQUIRED!) and it looks very pretty. VEry little escapes sideways once you get it going - until then you see all blue/violet coronas or whatever. In fact one does this when the tube is first aligned, hopefully never again.

[A_Gupta]

Sigh! UlanBatori, let me see

Wavelength of light is in nanometers = 10^-9.
wavelength of gamma rays is supposed to be picometers = 10^-12.
So, refractive index of sun = (10^-9)/(10^-12) = 10^3 = 1000.

The above is meaningless.

Also says there that a typical time for an excited atomic nucleus to release a gamma photon is ~10^-12 seconds.

I believe most of the scattering is off of free electrons.

But does ALL of a photon interact with an atomic nucleus or does most of it just go around it like Caspar the Friendly Ghost going around someone? I have no idea when two Heisenberg Uncertain Principals try to step around each other in a hallway. Probably head-on collision and both fall down.

All of the photon interacts; the outcome is probabilistic.

Also, what happens when an atomic nucleus is hit by a photon? Doesn't the photon have momentum? Does the nucleus sit still for the next million cycles? (million collisions)? Or does it get accelerated in short order to near the speed of light, so that when it emits, it is already 0.9 million wavelengths along the original trajectory of the photon? What happens to the Drunken Walk if the lamppost that the drunk walks into, moves 10 feet back with every collision?

The energy of the gamma rays produced in fusion is of the order of a few MeV (millions of electron volts). The energy equivalent of a proton (a H nucleus) is of the order of a GeV (a billion electron volts). The nucleus most certainly does not get accelerated to near the speed of light.

So from the philosophical pov, all the confusion is because ppl are talking about a star which IS observable, and sticking to the Fallacies-e-EkPatthar, viz, constant speed of light. And we find that we really don't know such things as the interaction times of photons with matter in regions where mass/energy conversion is likely.

See Thomson scattering.
http://farside.ph.utexas.edu/teaching/e ... ode96.html

The answer that g reaches infinity at the Event Horizon is really not an acceptable one - that is the Sound Barrier fallacy. At the center of our own galaxy, just a few (million?) Light Years away, is the Galactic BH. Surely one can get some idea of the actual value at the event horizon, since the event horizon has a FINITE radius?

http://mathpages.com/rr/s7-03/7-03.htm

[A_Gupta]

Now what happens if there is one Toll Booth every 100 m instead over every km? Baaad! 6 minutes per km, assuming very fast acceleration and deceleration.

What if there is one every 10m? 55 minutes per km, approaching Bangalore (old) Airport Road. This is what they claim is what happens inside the sun, discounting the Random walk. Interaction time ~10^-12 seconds, mean free path only a few centimeters.

Now what happens if one car goes in and it is another that comes out? Still takes 30 seconds per changeover. ...

Thomson scattering link provided previously.

[Vayutuvan]

UB ji: you referring to upwinding in CFD? Collimation vs. spatial coherence?

[Vayutuvan]

AmberG ji: All these days I was under the impression that Einstein got the nobel for his Brownian Motion research.

[Amber G.]

AmberG ji: All these days I was under the impression that Einstein got the nobel for his Brownian Motion research.

He got it, as I mentioned in previous posts, for ( see (http://www.nobelprize.org/nobel_prizes/ ... ates/1921/)):
"..for his services to Theoretical Physics, and especially for his discovery of the law of the photoelectric effect".

[sudarshan]

Olan* Butteri, are you saying the sun is a giant laser? You don't have just absorption and re-emission going on, you also have scattering and reflection. So the random walk model should be valid?

* Signature Mallu Dish

[UlanBatori]

(Sigh!) Imagine how Archimedes must have felt, trying to explain buoyancy and its relation to density, (or density to the relations?) to the Royal Court!

Speaking of the Sun as a laser, that is eminently possible. Not LASER but MASER. Pls 2 c Stellar MASERS onlee

[SriKumar]

... I am beginning to suspect that you are conducting some guerrilla street teaching ala Socrates who professed that he knew nothing; he only had questions.....

This is a good line TSJ. Afterall, it is also a method of teaching. Back to lurk mode...

JohneeG mian,
It is a good idea to to question every basic tenet till you understand it and are convinced....a worthy way of learning I agree, but sometimes I am not sure how far one can take it. I recall your posts ages ago where you stated you do not believe rockets can travel in space, and defended your position with several posts.

Do you still believe that rockets cannot travel in space (because as you said, rockets have to push against air to move, or some such thing IIRC) or have you changed your mind about that?I ask because understanding the causes of rocket locomotion is far easier than trying to understand the state of matter in black holes,sun; the mode of propagation of gravitational waves etc.

[UlanBatori]

Oh wonderful! Great thread! I am learning so much.

[Bade]

^^ That is quite a strong statement to make from someone making flying carpets and herding yaks in Mongolia. No wonder we still have to fly these dinosaurs after a 100 years. No improvement onlee and it takes a full 24 hrs to do the globe. Wonder what all those bazillions in funds are going to in rona&dhona instead of towards fundamental sciences. Little hard to digest that physicists are getting all the attention and Nobels which are well deserved of course on fraction of money spent... sour grapes only, what to do, na ? We are much smarter onlee !

[Bade]

To add salt to misery, again it took a physicist to claim a new mode of transport by photons...well it used to be a graduate school problem for qualifiers as I recall. It is headline news for some reason today.

[UlanBatori]

But TSJi: Note how he avoided the issue of the argon ion laser debunking the Random Walk? BUT.. the explanations from Physicsts on this thread are so superior! I am awed!

[UlanBatori]

Badeji: Apparently the bolded part is what is new:

To beat these odds, the new NIST two-photon source relies on a microstructured optical fiber. The fiber has a slender glass core at the center of an array of hollow channels, giving it a honeycomb appearance in cross-section. The geometrical structure of the fiber tightly restricts the way light can travel down it, increasing the intensity of light in the thin central core. Higher intensity means that photons are crowded more densely together, making events such as pair production more likely.

That greater efficiency allows the NIST researchers to get significant production of photon pairs by sending laser light through a mere 1.8 meters of the microstructured fiber, in contrast to the hundreds of meters of ordinary fiber that might be used in other systems. In addition, modifying the size of the channels in the microstructured fiber allows its properties to be optimized to reduce the amount of Raman scattering relative to the two-photon light of interest. The result is a source that produces significantly more pairs of photons over a wide frequency range, and with greatly reduced contamination by spurious Raman photons. Photon pairs from the new source could be useful, for example, in exploring quantum "entanglement," in which measurements on one of a pair of quantum particles with a common origin exert a subtle influence on the properties of the other, or in quantum cryptography.
Read more at: http://phys.org/news/2007-04-mass-nist- ... n.html#jCp

IOW, they kicked out those spurious yindoos and voila! Better entanglement!
My interest in this "entanglement" business comes from this:

Einstein was wrong: Groundbreaking test reveals spooky 'quantum entanglement' phenomenon IS real
In quantum physics, entangled particles are connected despite distance
This means the action of one will instantly change behaviour of the other
Theory riled Einstein as it suggested data could travel faster than light
A Dutch team proved the phenomenon using entangled electrons held in tiny diamond traps 0.8 miles (1.3km) apart
Read more: http://www.dailymail.co.uk/sciencetech/ ... z41Mz6AuSs
Follow us: @MailOnline on Twitter | DailyMail on Facebook

Imagine! There are spin-twins for the great Physicists!

[TSJones]

I have a horse sh*t theory about this faster than light photon data transfer.......

If I was to create a solid rod from Earth to Mars and I previously told the Martians that if I move the rod one inch then they must must come help me because I need their expertise. Soooo, the time comes that I need their help and I shove the rod towards Mars one inch, did I just exceed the speed of light data transfer? (disregard the effects of orbit and flexing, etc.)

No, I don't think I did. Why is that?

because of the physical properties of the rod make it all one thing. I shoved the rod, the whole thing moved. It had to because of it's physical structure in our dimension of the universe.

my horse sh*t theory is that it is the same with a photon.

you mess with one part of a split photon, you're messing with the other part also. In its dimension, it still all one thing.

I'm prolly way off the reservation on this one.

[sudarshan]

You ARE way off the reservation. Shoving the rod will generate a pressure wave, which will travel at the speed of sound in the medium. The other end won't move until the pressure wave reaches there - assuming all that energy isn't dissipated as heat before it even reaches Mars. Solids are supposedly incompressible (which means no energy dissipation and infinite propagation speed of pressure waves) but in practice, the bulk modulus is a very large but finite number, not infinity. And the speed of sound in (say) steel is way less than the speed of light.