Wave lengths---

[JHAQ]

On all diagrams I have seen the highest frequency ( or shortest wave length ) seem to be in gamma rays. Are any frequencies higher than gamma or cosmic rays known or is there a theoretical limit ? Intuition would indicate a limit to wave LENGTH as energy content decreases as wave length increases , becoming zero at infinite wave length .

[Severian]

Yes there are higher frquencies. In principle, there is no absolute limit, but obviously it becomes harder and harder to make higher and higher frequencies because higher frequency waves have more energy.

 

The only possible limit in frequency is that the energy should be less than the Planck scale 10¹⁹GeV. This is the energy scale at which gravity becomes strong, so your photons will start to rip holes in space-time at these energies (ie. make black holes). Whether this is an actual limit is a little bit aesthetic...

[5614]

gamma rays have the highest frequency of the electromagnetic spectrum... the rest severian said well

[YT2095]

the diameter of a photon (when treated as a particle), would be the limit in my esstimation.

establish that, and THAT will be your MAX wave-length possible

[Martin]

On all diagrams I have seen the highest frequency ( or shortest wave length ) seem to be in gamma rays. Are any frequencies higher than gamma or cosmic rays known or is there a theoretical limit ? Intuition would indicate a limit to wave LENGTH as energy content decreases as wave length increases , becoming zero at infinite wave length .

 

it's worth discussing more and getting more into it

if you feel like it---so keep on asking questions

 

the energy of a photon is proportional to its frequency

so as the energy rises the frequency goes up and the

wavelength gets smaller and smaller.

 

Severian mentioned Planck energy which is 2 billion joules

(he said 10¹⁹ billion electron volts which is

roughly the same thing and easier to understand if you do

particle physics)

 

2 billion joules roughly the fuel energy in your car's tank of gasoline or petrol----it is half a billion calories.

one photon (around big bang time) is imagined to be delivering that much energy

 

the more energetic a photon is the SMALLER it is considered to be as a particle, because the size of the particle corresponds to the wavelength and very high frequency things have very tiny wavelengths

 

The wavelength of a photon carrying planck energy is a small length called PLANCK LENGTH (that is one way that the planck length could be defined---or viceversa one way to describe the planck energy: as the energy of a photon that has planck length as its wavelength) all the fundamental planck scale quantities are closely tied in together.

 

The reason a planck energy photon can create a black hole is because it is too much energy concentrated into too small a space

A black hole has a SCHWARZSCHILD RADIUS proportional to its mass-energy and a black hole with the planck energy has a radius that is of the same magnitude as the planck length-----when energy or mass gets that concentrated it can collapse forming a black hole.

 

I think I am just saying the same thing as Severian's post but in a lot more words. You asked " is there a theoretical limit ?" and the answer is yes.

there is a theoretical limit to how much energy a photon can carry

because as its energy approaches planck

its wavelength shrinks down

to where it approaches the Schwarzschild radius of a black hole

with that much energy

and so the photon gets to where it just collapses!

 

 

the main thing to remember is if you take ANYTHING and compress it down to that thing's schwarzschild radius then it will collapse.

the schwarzsch. rad. of the sun is about 3 kilometers so if you could squeeze the sun down to 3 km radius then you could stop squeezing because

it would then collapse by its own gravity, forming a BH

everything is like that, they just have different schw. rad.

and if you squeeze anything that much then it becomes so dense that its own gravity takes over and collapses it

 

this theoretical limit on a photons energy, or frequency (proportional to energy) is in a sense very simple because it is just applying this

schwarzschild radius idea to photons

 

hope that's not too redundant

[Severian]

one photon (around big bang time) is imagined to be delivering that much energy

 

I don't mean to confuse the issue, but why do you think that all the energy was all in one photon? Presumably at the Planck scale, the ultimate gauge group is unbroken, so there will be no 'photons', only gauge particles of the unified group.

 

Or was this just a figure of speech....?

[Martin]

I don't mean to confuse the issue' date=' but why do you think that all the energy was all in one [i']photon[/i]? Presumably at the Planck scale, the ultimate gauge group is unbroken, so there will be no 'photons', only gauge particles of the unified group.

 

Or was this just a figure of speech....?

 

Good point!

 

at a certain temperature one stops calling them photons and starts calling them by some other name

 

the photon mediates the electromagnetic force

the gluon mediates the strong force

if the two forces are the same, at a high enough temperature,

then the two particles are the same

 

similarly with the weak force

 

all three forces (strong, weak, electromagn.) merge

 

so if you go to a higher and higher temperature

(approaching the Planck temperature of 1.4 x 10³² kelvin)

at some point there are no more "photons"

because all the forces are one force

they stop being photons and one has to call them

something else

 

calling them "photons" is as you say a "figure of speech" and a bit of a

simpleminded naive one at that!

 

BTW I personally am skeptical about the unification of all four forces because I dont think people (even though physicists are very smart)

really know at this point how gravity fits together with the others.

 

I am not sure that in a highly curved energy-dense regime that even the idea of "particle" is entirely appropriate or that the notion of "graviton" is altogether certain to be valid.

 

I tend to consider the gravitational field to be spacetime itself, or its shape. and so I think of gravity as geometry and I think of matter as something that lives in or on that geometry. So I think a quantum theory of gravity---a fundamental theory---not as a theory of graviton particles whizzing around in some absolute rigid space---but as a quantum theory of space itself in which geometric concepts like distance and area and volume and angle are quantized and correspond to quantum observables.

 

 

BTW the analysis of the big bang by quantum gravitists that I have seen does appear to confirm that temperatures and densities are at the Planck scale. It is at the planck scale that the LQG formalism predicts a bounce occurs. You can smile, but different people keep getting the same result, investigating this by various quantum gravity approaches. the planck temperature seems increasingly to be a real thing

[Severian]

I am still a big fan of the graviton being the consequence of local supersymmetry....