We say that the input and output of water is in equilibrium.
The water level just sits there even though the hose is going full blast.
This argument was popularized by Henry Morris (1974, p.164), who used some calculations done in 1968 by Melvin Cook to get the 10,000-year figure. Whitelaw, using a greater ratio of carbon-14 production to decay, concluded that only 5000 years passed since carbon-14 started forming in the atmosphere!
What the magnetic field does is to partially shield the earth from cosmic rays which produce carbon-14 high in the atmosphere.
It's a great argument except for one, little thing.
The water is coming out of the hose at a steady rate as our model assumed!
The curve is roughly 180 degrees out of phase with the C-14 curve.
(Strahler, 1987, p.156) The idea [that the fluctuating magnetic field affects influx of cosmic rays, which in turn affects C-14 formation rates] has been taken up by the Czech geophysicist, V.