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Light - For Those Who Are More Educated In This Field
- Thread starter Kenny
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Misunderstood
Active Member
I have to go to work, so do not have much time to check my own knowledge on this or give it much thought. My first feeling on this is yes, it can be in a scene. The speed of light is about 300,000km/s in a vacuum. However, through a diamond it is about half this speed. Meaning light would bunch up and stretch out so to speak, depending on what it is going through.
exchemist
Veteran Member
In a way, yes it can. The refractive index of a medium like glass (or even more, diamond, see post above) slows down the phase velocity, while not affecting the frequency (colour, energy), which therefore shortens the wavelength, i.e. compresses it. And the expansion of the metric in the universe stretches light, in a way that does alter the wavelength and frequency but not the speed, creating the cosmological red shift.
(The relationship between speed, c, frequency, ν, and wavelength,λ is:
c = νλ. So if c is fixed, a change in λ implies a change in ν, whereas if ν is fixed, a change in c implies a change in λ.)
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Yes, I guess in a sense gravity can have such an effect
The wave length of light can increase or decrease with the Doppler effect if its source is moving, but no, not in the literal sense, where something is compressed by a force and then returns to its original position when the compressing force is removed. Photons aren't solid matter:
"Elasticity is the tendency of solid objects and materials to return to their original shape after the external forces (load) causing a deformation are removed."
Yes. Its frequency can vary. Which looks a bit like a stretching.
For instance, if someone flashes light to me while running away from me, that light will look stretched to me. In the same way an ambulance running away from you will have a different sound tone.
However, that stretching just changes its energy, which is proportional to the frequency, but not its speed in vacuum, which is independent of any stretching.
Ciao
- viole
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There are several ways to interpret your question.
1. If light goes through a medium, like air or glass, it goes slower and has the same frequency, so the wavelength is longer. That can be interpreted as a dilation.
2. Doppler shift. If the source of light is moving either towards or away from you, the frequency will either go up (towards) or down (away). This is associated with a decreased (towards) or increased (away) wavelength, so as a compression or dilation.
3. Gravity. Light that moves up in a gravitational field loses energy, and so gets a longer wavelength. If it moves down, the wavelength gets smaller.
4. It is possible to talk about a 'photon gas' that has a temperature and a pressure. This is mostly relevant in regions like the interior of stars. A higher pressure will compress that photon gas.
5. In cosmology, the expansion of space also increases the wavelength of light (hence, a red shift).
I'm sure there are others, but these are the main ways off the top of my head.
1. If light goes through a medium, like air or glass, it goes slower and has the same frequency, so the wavelength is longer. That can be interpreted as a dilation.
2. Doppler shift. If the source of light is moving either towards or away from you, the frequency will either go up (towards) or down (away). This is associated with a decreased (towards) or increased (away) wavelength, so as a compression or dilation.
3. Gravity. Light that moves up in a gravitational field loses energy, and so gets a longer wavelength. If it moves down, the wavelength gets smaller.
4. It is possible to talk about a 'photon gas' that has a temperature and a pressure. This is mostly relevant in regions like the interior of stars. A higher pressure will compress that photon gas.
5. In cosmology, the expansion of space also increases the wavelength of light (hence, a red shift).
I'm sure there are others, but these are the main ways off the top of my head.
exchemist
Veteran Member
Surely the wavelength is shorter in an optically dense medium? c reduces, ν stays the same so λ must reduce. Isn't it?
Ben Dhyan
Veteran Member
According to the Tired Light Theory, light wavelength will increase with radiated distance due to....well read it for yourself. Tired Light Denies the Big Bang
exchemist
Veteran Member
Yes. Unfortunately that theory is ballocks. It doesn't work. Tired light - Wikipedia
Ben Dhyan
Veteran Member
The wiki piece is dated, you should have read the article.
Tired Light Denies the Big Bang
The Big Bang, after Hubble’s work, became the most accepted cosmological model. In recent years, problems related to Big Bang have been more and more clearly realized by cosmologists and astronomers. Some problems are directly related to the interpretation of the Doppler effect for cosmological redshift. The Big Bang model cannot surmount these problems. Fortunately, the study of “tired light” theory has continued. In 2013, Shao developed the “tired light” hypothesis on the basis of physical principles, that is, (a) electromagnetic field theory, (b) the mass-energy equivalence, (c) the quantum light theory, and (d) the Lorentz theory [2]. Based on these physical principles, the “tired light” theory explains the cosmological redshift as the result of photon energy loss due to the interactions with material particles as photons travel through cosmological space. By this interpretation for cosmological redshift, the Cosmos is infinite and eternal.
Besides, BB theory that existence came from nothing is nonsense, there is no nothing, never was, nor ever will be.
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exchemist
Veteran Member
That journal (IntechOpen) appears on Beall's list of predatory journals. As such, no article in it can be trusted to be good science. So I'm certainly not going to waste my time reading that stuff.
If the paper has been published in a proper academic journal, send me a link and I may read it. I am not aware that any reputable science has revived this obsolete theory but I'm open to reading something credible on the topic. Meanwhile however my previous comment stands.
Ben Dhyan
Veteran Member
Ok, this one.
The New Tired Light Theory correctly predicts the redshift of the CorBor galaxy cluster.
The New Tired Light Theory (NTL) is tested by using known data of the distance to the Corona Borealis galaxy cluster (A2065 in particular) and from this predicting the red-shift of the galaxy. This is then compared to the measured value. In NTL, photons of light are continually absorbed and re-emitted by the electrons in the plasma of interga-lactic space which recoil both on absorption and re-emission. Energy is transferred from the photon to the recoiling electron and thus the photon energy is reduced, the frequency is reduced and the wavelength is increased. It is redshifted. Using the wavelength of the ‘K line’ of ionised calcium, standard physics and published collision cross-sections, the predicted redshift by NTL is found to be z = 0.067. This compares favorably with the measured redshift value of 0.0714 - they agree to within 6%. The energy transferred to the recoiling electron is emitted as secondary photons. The predicted wavelength of these secondary photons is calculated and is shown to be in the microwave region of the electro-magnetic spectrum. This again is consistent with the NTL prediction that these secondary photons form the CMB.
The New Tired Light Theory correctly predicts the redshift of the CorBor galaxy cluster.
exchemist
Veteran Member
Nope. Academia.edu is not peer-reviewed and I know for a fact is used by cranks to publish their nonsense. Any fool can publish there.
I mean a proper, recognised scientific journal.
Ben Dhyan
Veteran Member
I do not think the red shift of light due to distance (TLT) is questioned by the expansionists, both distance and expansion result in red shift as I understand it, it is on other grounds.
exchemist
Veteran Member
So no paper in any recognised journal has revitalised the Tired Light hypothesis, then? I thought as much.
I expect it will be just fringe, crank stuff. Very often these crank ideas seem to be espoused by engineers, rather than physicists or cosmologists. Electrical and radio engineers are the worst, in my experience.
Ben Dhyan
Veteran Member
Haha, what about chemical engineers, they are the most cranky of all.So no paper in any recognised journal has revitalised the Tired Light hypothesis, then? I thought as much.
I expect it will be just fringe, crank stuff. Very often these crank ideas seem to be espoused by engineers, rather than physicists or cosmologists. Electrical and radio engineers are the worst, in my experience.
But at least we have established that tired light, ie. distance of radiation travelled results in red shift.
https://www.researchgate.net/public...e_Interpretation_of_the_Accelerating_Universe
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wellwisher
Well-Known Member
Light has the properties of being both a wave and a particle. If we look at light in terms of wave addition, two waves of the same wavelength, can add to a larger wavelength; stretch. This can be done with two similar waves, with a time delay between them, so they add over a longer total distance. This new composite wave can have frequency and wavelength not equal to the speed of light, since the particle and waves add differently.
Consider this scenario, we have a wave tank with two wave generators, one at each end of the tank. We will generate the exact same waves; wavelength and frequency with each wave generator. The waves will add in the middle. In this scenario, I will make each wave generator 180 degrees out of phase, so when the two waves meet and overlap in the middle, the troughs and crests of each wave will cancel; add to zero. This is called destructive interference.
What we will see is an interesting an affect. We are adding energy via the two wave makers, but where the two waves cancel, we have a zone of calmness, since the waves cancel each other out. Where did the wave energy go? This is an example of hidden wave energy. We know energy was used since the wave generators used X electricity each pulse, but there are no waves in the middle to express that energy. It is there but hidden.
We can show the audience the is hidden energy in the calm, and even get all this hidden energy back, if we place a partition in the stillness. This will disrupt the wave addition, so the two separate waves and their energy will reappear on opposite sides of the partition. In atoms electron orbitals occur with opposite spin electrons, so their wave cancel; tuck away some hidden energy for safe keeping.
exchemist
Veteran Member
Not really in my experience. (I once went out with a particularly pretty and capable one - and I knew a lot of (mostly male) ones at Shell, two of whom are still occasional drinking companions.
But engineers as a breed are not the best experts when it comes to pure science research, because that's not what they do.