A Geiger counter, also called a Geiger-Müller counter, measures ionizing radiation._ (from wikipedia.org)
Sean Connelly (Peebrain), the guy behind the great psionics site PsiPog.net writes on his blog about experiments with a geiger counter to detect psi activity. On his weblog he describes the repeatable results he and his friends have had with geiger counter readings being affected by some forms of psi:
Erik first reproduced his experiment, but this time with me watching, so I could see how it was setup. Over his webcam, he showed me his geiger counter, transducer, and oscilloscope. First, I tried to get the geiger counter to go crazy, like he described JoeT doing it. I failed. Roy tried. He failed. So finally we invited JoeT to do it again… The average detection range for a geiger counter sitting in a normal room is anywhere from 8 to 25 counts per minute (CPM)… and it’ll usually average between 12 and 15. When JoeT focused on it, he got the counter to max out at 47 CPM. Very significant.
I went to look if this indeed was unique… Apparently not. Looking for the information I’ve arrived again to the Uri Geller’s site and one of the pages describes how he was tested in a laboratory conditions, also trying to influence a geiger counter. Uri Geller was able to bring this thing to a 1000! count, which was 500 times above the average at that place.
Here’s the excerpt:
The final test was to determine if Geller could produce a deflection on the Geiger counter; this should indicate whether he could produce radioactive radiation. When it was held near him, Geller registered a zero count on the instrument, taking into account the average background rate of about two counts per second produced by cosmic rays coming from outer space. Geller then took the monitor in his own hands and tried to influence the counting rate. We all stood round looking at the dial and listening for the telltale tone.
At first nothing happened, but by extreme concentration and an increase in muscular tension associated with a rising pulse rate, the needle deflected to 50 counts per second for a full two seconds, the sound effects heightening the drama of the occasion. By means of a small loudspeaker each count produced a “pip,” and before Geller affected the machine the sound was of a steady “pip … pip … pip . . . .” In his hands the sound sud- denly rose to become a wail, one which usually indicates dangerous radioactive material nearby. When Geller stopped concentrating the Wail stopped and the apparent danger with it. This wail was repeated twice more, and then when a deflection of 1 00 counts per second was achieved, the wail rose almost to a scream. Between each of these attempts there was an interval of about a minute. A final attempt made the needle deflect to a reading of 1000 counts per second, again lasting for about two seconds. This was 500 times the background rate – the machine was emitting a scream in the process. After a rest of several minutes, a further deflection of 200 counts per second was produced, lasting about five seconds.
So it seems that using the instrument can be a great proof for the skeptics. I wish Sean best luck with his continuing attempts with the geiger counter.