Free Death by Black Hole: And Other Cosmic Quandaries by Neil deGrasse Tyson Page A

Try to picture the tumult! Dishevelled atoms tear along at 50 miles a second with only a few tatters left of their elaborate cloaks of electrons torn from them in the scrimmage. The lost electrons are speeding a hundred times faster to find new resting-places. Look out! A thousand narrow shaves happen to the electron in [one ten-billionth] of a second…. Then…the electron is fairly caught and attached to the atom, and its career of freedom is at an end. But only for an instant. Barely has the atom arranged the new scalp on its girdle when a quantum of aether waves runs into it. With a great explosion the electron is off again for further adventures. (p. 19)
     
    Eddington’s enthusiasm for his subject continues as he identifies aether waves as the only component of the Sun on the move:
As we watch the scene we ask ourselves, can this be the stately drama of stellar evolution? It is more like the jolly crockery-smashing turn of a music-hall. The knockabout comedy of atomic physics is not very considerate towards our aesthetic ideals…. The atoms and electrons for all their hurry never get anywhere; they only change places. The aether waves are the only part of the population which do actually accomplish something; although apparently darting about in all directions without purpose they do in spite of themselves make a slow general progress outwards. (pp. 19–20)
     
    In the outer one-fourth of the Sun’s radius, energy moves primarily through turbulent convection, which is a process not unlike what happens in a pot of boiling chicken soup (or a pot of boiling anything). Whole blobs of hot material rise while other blobs of cooler material sink. Unbeknownst to our hardworking photons, their residential blob can swiftly sink tens of thousands of kilometers back into the Sun, thus undoing possibly thousands of years of random walking. Of course the reverse is also true—convection can swiftly bring random-walking photons near the surface, thus enhancing their chances of escape.
    But the tale of our gamma ray’s journey is still not fully told. From the Sun’s 15-million-degree Kelvin center to its 6,000-degree surface, the temperature drops at an average rate of about one one-hundredth of a degree per meter. For every absorption and re-emission, the high-energy gamma-ray photons tend to give birth to multiple lower-energy photons at the expense of their own existence. Such altruistic acts continue down the spectrum of light from gamma rays to x-rays to ultraviolet to visible and to the infrared. The energy from a single gamma-ray photon is sufficient to beget a thousand x-ray photons, each of which will ultimately beget a thousand visible-light photons. In other words, a single gamma ray can easily spawn over a million visible and infrared photons by the time the random walk reaches the Sun’s surface.
    Only one out of every half-billion photons that emerge from the Sun actually heads toward Earth. I know it sounds meager, but at our size and distance from the Sun it totals Earth’s rightful share. The rest of the photons head everywhere else.
    The Sun’s gaseous “surface” is, by the way, defined by the layer where our randomly walking photons take their last step before escaping to interplanetary space. Only from such a layer can light reach your eye along an unimpeded line of sight, which allows you to assess meaningful solar dimensions. In general, light with longer wavelengths emerges from within deeper layers of the Sun than light of shorter wavelengths. For example, the Sun’s diameter is slightly smaller when measured using infrared than when measured with visible light. Whether or not textbooks tell you, their listed values for the Sun’s diameter typically assume you seek dimensions obtained using visible light.
    Not all the energy of our fecund gamma rays became lower-energy photons. A portion of the energy drives the large-scale turbulent convection, which in turn drives pressure waves that ring the