55 When the intrinsic angular momentum is measured relative to the direction of the photon’s motion
56 There were a few Doc Savage novels published in the 1970s and 1990s that were credited to Dent posthumously, but his main run on the pulp magazine ended in July 1949.
57 The government should not have bothered—in 1911 Modern Electronics published “Ralph 124C 41+,” a science fiction story by Hugo Gernsback (who would go on to found Amazing Stories) that featured a fairly accurate description of radar, long before the term was coined.
58 I’m sure that there was a point in time for nearly all readers when glow-in-the-dark materials seemed to be the greatest technological invention in the history of the universe.
59 The lower energy seats that are filled for the individual atoms (Figure 31 c,d,e) also broaden into their own filled auditoriums that do not play a major role in the solid’s properties.
60 Note that a laser does not need to be a solid—the helium-neon laser pointers used by public speakers and lecturers employ a mixture of two inert gases to generate laser light. For simplicity, we’ll stick with solid-state lasers, but our arguments hold just as well for gas lasers.
61 Experts will note that the above argument applies to electric dipole transitions, but not to those involving magnetic dipole or electric quadrupole transitions. These are typically ten thousand to a million times less likely than electric dipole transitions. For the nonexperts—nothing to see here; move along!
62 The operation of a real laser cavity is a bit more complicated than this.
63 Old-timers may recall an early ancestor of the DVD—laser discs, which were twelve inches in diameter in order to have sufficient room for the relatively low-density bits encoding a video image that could be read with a laser.
64 To the men of America—you’re welcome!
65 The arguments for electrons in the balcony in one direction will hold for holes in the orchestra in the opposite direction. For simplicity, I focus on the electrons.
66 There are many different types of transistor structures—what we have described is technically referred to as a metal-oxide-semiconductor field-effect transistor, or a MOSFET.
67 For technical reasons the actual bits on a hard drive involve several magnetic domains, arranged in different sequences to represent “ones” and “zeros,” but for our purposes we can simplify this to single domains for a “one” or a “zero.”
68 Which is why one must avoid stray metallic objects in the MRI room when the magnet is powered.
69 In fact, the radio-wave signal is turned on and off continuously, but the emission of radio waves when the system relaxes back to the lower-energy configuration is what is detected.
70 As the person is at a temperature of 98.6 degrees Fahrenheit, there is enough thermal energy to promote protons into the higher energy state, even without radio-frequency light. Increasing the external magnetic field raises the energy separation between states, and fewer protons will be found in the upper level in the dark. The detection sensitivity in an MRI device is quite high, and the MRI system is able to detect the small additional fraction of protons that are promoted by the radio waves.
71 This technique is still in the experimental stage, so you don’t need to invest in tin-foil hats just yet.
72 A prime number is a number that can be divided only by itself or 1. The number 5 is a prime number, while 8 is not (it can be divided by 2 and 4, in addition to 8 and 1). Computer security involves numbers that are the product of two very large prime numbers. Security is maintained by requiring both sides of the transaction to know the factors (which are so large that it is impossible to guess even using conventional supercomputers to try all possibilities).
73 No pun intended.
74 This is similar to the question of position and momentum measurements in Chapter 7. The answer you receive depends on what question you ask.
75 This is for the first version of the arc reactor, “built in a cave—with a bunch of scraps!” Later models had even higher power outputs, though the exact specs are the classified proprietary information of Stark Enterprises.
76 Just as, in our discussion of solid-state thermometers a moment ago, the metal electrode and the contacting fluid represent two partially filled auditoriums, which will have electrons move from one room to the other, depending on which room has the higher concentration of electrons.
77 Though other chemical compounds are employed depending on the battery requirements.
78 These may seem like simple devices, but there is more to them than meets the eye!
79 Don’t worry, Fearless Reader—he was framed and eventually demonstrated his innocence.
80 I don’t want to tell them their jobs, but if I were an astronomer, I’d keep my eye on Planet X. I think it might be trouble.
81 Primarily because it involves imaginary numbers!
The Amazing Story of Quantum Mechanics Page 34