Biggest photon possible?

[Mr Skeptic]

well, the wavelength can't get any bigger than the universe so i guess that imposes a physical limit on it.

 

Now there is an interesting thought, possibly worthy of its own thread. What happens when your photon is large enough that the expansion of the universe would "split" it in pieces? Or would it be impossible to get a photon with less than the Plank energy, giving it a maximum wavelength? But then what happens when you red-shift that photon?

[big314mp]

The Planck energy is quite large, and I doubt there are very many photons in the universe with that much energy. Maybe the planck energy would set a maximum, but it sure doesn't set a minimum:

 

http://en.wikipedia.org/wiki/Planck_energy

 

By the time you read this, it might have already changed, but you have 1666 posts, and I think that's kind of nifty.

[I_Pwn_Crackpots]

If the wavelength is as big as the universe, I don't think it can be redshifted. After all, cosmological redshifts are caused by the expansion of the universe itself. It can't get any longer then that.

[big314mp]

I think what they were going for was, the photon was as big as the universe at 2 o'clock, then the universe gets bigger, what is the photon at 5 o'clock.

 

Of course, you also have to consider that the universe may be infinite in size, so infinite wavelength may be a possibility.

[Mr Skeptic]

I meant a photon as big as the visible universe. Large enough that it would be impossible to reach one side of the photon from the other even at the speed of light. So then the expansion of the universe would tear the photon apart. It seems to me it should be impossible, but I don't know why it would.

[big314mp]

What would the result be? It seems like you would have 2 photons, each with a wavelength half of the original photon. Except that is 4x as much energy as the original photon started with.

 

Is it even meaningful to speak of the photon being that big? Do photons "get bigger" in the traditional sense that an elephant is larger than a mouse? I think part of the problem may be that we are applying human intuition to this problem.

[RENITA]

Photon yields — the number of photons generated per analyte atom — are of obvious analytical and mechanistic importance in flame chemiluminescence. However, such numbers are unavailable for spectral detectors in gas chromatography (as well as for most conventional spectroscopic systems). In this study, photon yields have been determined for the chemiluminescence of several elements in the flame photometric detector (FPD). The number of photons generated per atom of FPD-active element was 2×10−3 for sulfur (emitter S2*, test compound thianaphthene), 3×10−3 for phosphorus [HPO*, tris(pentafluorophenyl)phosphine], 8×10−3 for manganese (Mn*, methylcyclopentadienyl manganese tricarbonyl), 3×10−3 for ruthenium (emitter unknown, ruthenocene), 4×10−5 for iron (Fe*, ferrocene) and 2×10−4 for selenium (Se2*, dimethylbenzselenazole). Total flows, maximum thermocouple temperatures, and visible flame volumes have also been estimated for each element under signal/noise-optimized conditions in order to provide a database for kinetic calculations.

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RENITA

Edited September 17, 2008 by YT2095
url removed

[insane_alien]

that has nothing to do with this thread.

[ydoaPs]

Well, iirc, the visible universe is 46 billion lightyears across. [math]v=f \lambda[/math] where v is the speed of the wave(which we know to be c), f is the frequency, and [math]\lambda[/math] is the wavelength. We can rearrange the equation to find the frequency. [math]f=\frac{c}{\lambda}[/math]. Now, we can plug the wavelength in and see what we get.[math]f=\frac{c}{46,000,000,000 \times c \times 1year}[/math] That works out to be 1.6x10^-18Hz.

 

Actually, the period would be more useful. [math]T=\frac{1}{f}[/math], so, the period would be 1.6x10¹⁸seconds or 46 billion years. Consider the accepted age of the universe is roughly 14 billion years and draw your own conclusion from that.

[Klaynos]

<Klaynos> ydoaPs: does a photons period have to be less than the lifetime of the universe, if so, why?

[ydoaPs]

Klaynos, the period is the time it takes to complete a cycle. If the period is that much larger than the age of the universe, it would still need almost 3 more universe lifetimes to complete it's first cycle. EM waves are oscillating electric and magnetic fields. The oscillation in the case is so slow that it approximates not oscillating at all. This photon approximates a uniformly moving field with a constant magnitude. I wouldn't consider it a photon, but others might.

[SH3RL0CK]

So then what happens when the universe becomes 46 billion years old? (Actually, since the universe is expanding, when the age of the universe equals the distance across at the speed of light)?

 

Or, given that the universe expansion rate is increasing, would this ever happen?

 

Sorry, my math isn't good enough to calculate this by myself...I'm not even sure this calculation is possible given how little we know about "dark energy" driving the expansion of the universe.

[alan2here]

If the wavelength is as big as the universe, I don't think it can be redshifted. After all, cosmological redshifts are caused by the expansion of the universe itself. It can't get any longer then that.

The universe it infinity large. (why don't we say unfinite?)

[Pete]

Now there is an interesting thought, possibly worthy of its own thread. What happens when your photon is large enough that the expansion of the universe would "split" it in pieces? Or would it be impossible to get a photon with less than the Plank energy, giving it a maximum wavelength? But then what happens when you red-shift that photon?

I find this to be a confusing response. A photon doesn't have a spatial extent. Its not like the length of a photon is one wavelength or anything like that. Wavelength is physically realized by the spatial distribution associated with the wavelength.

[Klaynos]

You can only "fit" certain wavelengths in sized containers though, that's why the casimir effect works, only the photons of suitable wavelength can exist between the two plates....

 

You'd need to know the boundary conditions of the edge of the universe to work out what happens there though, and that's not really a question that we can answer right now, and probably doesn't even make sense...