Dr. Hovind (R2): The C-14 decay rate is not constant. Several factors, including the 11-year sunspot cycle, affects its rate of decay.It is painfully obvious that Dr. Hovind knows next to nothing about carbon-14 dating! Changes in the sunspot cycle do have a noticeable, short-term effect on the rate of C-14 production inasmuch as sunspots are associated with solar flares that produce magnetic storms on Earth, and the condition of the earth's magnetic field affects the number of cosmic rays reaching the earth's upper atmosphere. (Carbon-14 is produced by energetic collisions between cosmic rays and molecules of nitrogen in the upper atmosphere.) Sunspots have absolutely nothing to do with the rate of C-14 decay, which defines the half-life of that radioactive element. Dr. Hovind has confused two completely different concepts.
Quantum mechanics, that stout pillar of modern physics, which has been verified in so many different ways that I couldn't begin to list them all even if I had them at hand, gives us no theoretical reason for believing that the C-14 rate of decay has changed or can be significantly affected by any reasonable process. We also have direct observation:
That radiocarbon ages agree so closely with tree ring counts over at least 8000 years, when the observed magnetic effect upon the production rate of C-14 is taken into account, suggests that the decay constant itself can be assumed to be reliable.
Since 8000 years is almost two half-lives for carbon-14, it's half-life being 5730 years (plus or minus 40 years), we have excellent observational evidence that the decay rate is constant. We also have laboratory studies which support the constancy of all the decay rates used in radiometric dating.
A great many experiments have been done in attempts to change radioactive decay rates, but these experiments have invariably failed to produce any significant changes. It has been found, for example, that decay constants are the same at a temperature of 2000 degrees C or at a temperature of 186 degrees C and are the same in a vacuum or under a pressure of several thousand atmospheres. Measurements of decay rates under differing gravitational and magnetic fields also have yielded negative results. Although changes in alpha and beta decay rates are theoretically possible, theory also predicts that such changes would be very small [Emery, 1972] and thus would not affect dating methods. Under certain environmental conditions, the decay characteristics of C-14, Co-60, and Ce-137, all of which decay by beta emission, do deviate slightly from the ideal random distribution predicted by current theory [Anderson, 1972; Anderson & Spangler, 1973], but changes in the decay constants have not been detected.
There is a fourth type of decay that can be affected by physical and chemical conditions, though only very slightly. This type of decay is electron capture (e.c. or Kcapture), in which an orbital electron is captured by the nucleus and a proton is converted into a neutron. Because this type of decay involves a particle outside the nucleus, the decay rate may be affected by variations in the electron density near the nucleus of the atom. For example, the decay constant of Be-7 in different beryllium chemical compounds varies by as much as 0.18 percent [Emery, 1972, 64]. The only isotope of geologic interest that undergoes e.c. decay is K-40, which is the parent isotope in the K-Ar method. Measurements of the decay rate of K-40 in different substances under various conditions indicate that variations in the chemical and physical environment have no detectable effect on its e.c. decay constant.
Believe it or not, a number of creationist attacks against radiometric decay rates are aimed at a kind of "decay" called internal conversion (IC), which has absolutely nothing to do with the radiometric dating methods (Dalrymple, 1984, p.88). Harold Slusher, a prominent member of the Institute for Creation Research, claimed that "Experiments have shown that the decay rates of cesium 133 and iron 57 vary, hence there may be similar variations in other radioactive decay rates." (Slusher, 1981, p.22, 49; from Brush)
These are both stable isotopes so there is no decay rate to be changed. This statement merely reveals Slusher's ignorance of nuclear physics. (Gamma decay of an excited state of iron 57 has been studied, but this has nothing to do with the kinds of decays used in radiometric dating.)
DeYoung  lists 20 isotopes whose decay rates have been changed by environmental conditions, alluding to the possible significance of these changes to geochronology, but the only significant changes are for isotopes that "decay" by internal conversion. These changes are irrelevant to radiometric dating methods.
Keep an eye on those creationists! They will switch tracks faster than you can say "tiddlywinks." One moment they're talking about the radioactive decay of the nuclides involved in geochronology, and, in the next moment, they're passing out examples of IC decay in stable isotopes. Morris (1974) claimed that free neutrons might change the decay rates. However, Henry Morris, that icon of creationism, only demonstrated that he knew no more about radiometric dating than does Dr. Hovind today. "...[Morris'] arguments show that he does not understand either neutron reactions or radioactive decay." (Dalrymple, 1984, pp.88-89). Free neutrons might change one element into another, but the decay rates all remain true to their elements.
Another attempt by Morris invokes neutrinos.
Morris  also suggests that neutrinos might change decay rates, citing a column by Jueneman (72) in Industrial Research. The subtitle of Jueneman's columns, which appear regularly, is, appropriately, "Scientific Speculation." He speculates that neutrinos released in a supernova explosion might have "reset" all the radiometric clocks. Jueneman describes a highly speculative hypothesis that would account for radioactive decay by interaction with neutrinos rather than by spontaneous decay, and he notes that an event that temporarily increased the neutrino flux might "reset" the clocks. Jueneman, however, does not propose that decay rates would be changed, nor does he state how the clocks would be reset; in addition, there is no evidence to support his speculation.
There was also an attempt by Slusher and Rybka to invoke neutrinos. Those mysterious neutrinos seem to be a hot topic!
Slusher (117) and Rybka (110) also propose that neutrinos can change decay rates, citing an hypothesis by Dudley (40) that decay is triggered by neutrinos in a "neutrino sea" and that changes in the neutrino flux might affect decay rates. This argument has been refuted by Brush (20), who points out that Dudley's hypothesis not only requires rejection of both relativity and quantum mechanics, two of the most spectacularly successful theories in modern science, but is disproved by recent experiments. Dudley himself rejects the conclusions drawn from his hypothesis by Slusher (117) and Rybka (110), noting that the observed changes in decay rates are insufficient to change the age of the Earth by more than a few percent (Dudley, personal communication, 1981, quoted in 20, p.51). Thus, even if Slusher and Rybka were correct which they are not the measured age of the Earth would still exceed 4 billion years.
Dalrymple goes on to debunk several other creationists attacks on the reliability of the radiometric decay rates used in geochronology. Judging from the above, it is easy to see that creationists are indulging in wild fishing expeditions. Compare their flighty arguments to the solid support provided by theoretical work, laboratory testing, and, for the shorter half-lives, actual observation, and add to that the statistical consistency of the dates obtained, including numerous crosschecks between different "clocks," and only one conclusion is left. The radiometric decay rates used in dating are totally reliable. They are one of the safest bets in all of science.