No. Photons from the Sun’s core are primarily a result of electron-positron annihilation after the first step or during the second step of the pp chain reaction. (There is also some gamma production in some of the minor subsequent branches, and in the C-N-O cycle, but in terms of photon production in Solar-mass stars these are only very small fractions of total output). These photons don’t “exist”, even in the QED sense of being tied up in elevated energy levels or binding energies of charged particles, until the decay event occurs.
No. In any practical sense, there is no information to a photon besides its frequency (or wavelength) and momentum. Because of indeterminancy, even if you know the precise amount of energy that the photons resulting from a given gamma-electron interaction should be, you won’t be able to say which resulting photons came from where. All fundamental particles are exactly alike, save for their position and momentum (or other complementary paired dynamic properties).
A star will continue to produce energy, new photons if you will, as long as there is hydrogen to burn. When that runs out the fusion reaction stops. A star the size of our sun then expels most of its outer matter with the remainder collapsing to a white dwarf.
However long it is from the end of the hydrogen until the star throws off all of that matter to form a planetary nebula would seem to be all the time we would have.
I don’t think I need to worry. I don’t know about some of you younger folks.
Not quite. A star the size of the Sun will continue, once fuel for hydrogen fusion is exhausted, to “burn” helium via the triple alpha process, producing carbon and oxygen as it condenses into a white dwarf, held from further collapse by electron degeneracy pressure. Of course, by that time you aren’t going to be living on the surface of the planet, which will have been well scorched by the expanding Sun. Most of the photons being released at that point will have been originally produced in fusion reactions millions of years previous, due to the greater density of the star.
OK, but the outer material of the sun will have been blown away to fry the earth before the helium burning starts, or maybe as it starts.
Ireally think it’s better to call the “photons” inside the sun energy. The photons that reach the earth are all newly created by electron level changes right now, or 8 minutes ago.
It seems to me that any old photons here on Earth must, as a consequence of the nature of electromagnetic energy be from very far away. I cannot be aware of a photon until it has ceased to exist as a discrete particle anyway. Claiming that a photon that came from the sun must be older than the transit time for it to get from the sun to the device that captured it (and by the way, changed it into some other form of energy) is manifestly unprovable.
Now that I think of it, the cosmic background radiation is constantly being absorbed, and re-emitted by pretty much everything in the solar system. To pretend that the light emitted by the photosphere of the sun is “old” photons is an entirely argumentative, and misleading assertion, and fundamentally impossible to prove. It is equally pointless to decide that the energy those photons represent is in some comparative way “old.” Energy is all old. Older, in fact than the sun itself. The sun is only able to exist because of vastly older constructs of matter and energy, which themselves were created by older still forms of energy.
Let’s file the serial numbers off these photons, eh? A photon, as a discrete particle may exist for a continuous interval of time between its emission by some energetic particle, until it interacts with another particle, altering that particle’s energy state. I have trouble picturing a proof of even that nebulous a continuity, since I have only endpoints to examine, but I am willing to suppose it might be so. Supposing any other temporal continuity for a photon seems to me to involve a book and a half of assumptions, none of which seem testable.
So, if the sun magically stops producing “new photons” it becomes magically constant in temperature, but magically not able to transfer any energy within, or out of its own mass. The sun, then goes black instantaneously. It remains very hot, but it doesn’t radiate. Eight minutes later, bad weather sets in on Earth. A few minutes after that, magicians find new ways of staying warm, growing food, seeing what the hell is going on, etc.
[QUOTE=gatorman]
Life would cease to exist, but it wouldn’t be in 8.5 minutes. A few years for most of the life we see everyday, a few decades for insects and other smaller forms of terrestrial and aquatic life. Humans would probably be gone by then. The MAIN culprit for their eventual death would be from lack of oxygen, since most of the oxygen produced on our planet is from oceanic algae which would die off without sunlight.
[quote]
I agree with *Sam Stone on his analysis of this. I think lack of oxygen because all the oxygen has condensed to a liquid will happen way before things suffocate because no more oxygen is being produced. Plummeting temperatures are the killer, in short order.
I don’t think the hydrothermal vents would last long either - apparently they come and go, shutting down in one place, starting up in another - leaving the dependant ecosystem to die in one place and colonise the new place - difficult enough to do when the seed organisms have to move through water to colonise the new habitat. Impossible to do if the water between the old and new habitats is in it’s solid form.
One of the issues brought up was “can the high energy light of the Sun’s core be the same photons as the visible spectrum light we see on Earth?” I suppose you can make an argument that a photon that only experiences a direction change from the interaction can be considered the same photon, bounced. I’m not sure how you argue that a photon that changes wavelength can be considered the same photon.
Wavelength could appear different for the same photon depending on the reference frame of the observer (although of course that photon can only be observed one way, or the other, I think…)
Right. In the zero-momentum frame of the photon and the electron together (which is probably pretty close to the electron’s frame), the photon bounces off with the same wavelength as it came in with. This is true for every photon-electron interaction. However, the electrons are bouncing around randomly at high speeds, so they don’t all have the same frame. If you pick some global reference frame, such as the zero-momentum frame of the entire Sun, the net effect is that the energy gets redshifted as it makes its way out from the core.
When you say redshifting here, do you mean gravitational redshifting or some other effect? If you’re talking about a gravitational effect, how do you calculate the redshift caused by ‘climbing’ out of the sun’s gravitational field and/or the blue shift caused by the photon’s ‘falling into’ the earth’s field? Do the two things balance out somehow?
There will be a gravitational redshift, but it’ll be negligible. The redshift I was referring to is ultimately a Doppler shift (or rather, a whole bunch of Doppler shifts put together). Basically, interactions with the electrons at a given layer of the Sun will tend to bring the photons to the same temperature as the electrons at that layer. So the photons in the core of the Sun will have energies (and thus frequencies and wavelengths) corresponding to a temperature of millions of degrees, while photons leaving the surface of the Sun will have energies corresponding to a temperature of a few thousand degrees.
