time to put up or shut up
I ran some calibrating issues down today. There will be a few more before the actual experiment. A failure is no good unless it's a solid, professional failure. You can't prove or disprove anything with shoddy designs or procedures. Let us first and foremost be thorough.
1) Magnetic field interference
There is a magnetic field in my computer room from the earth. I need to know if it will affect the outcome on an experiment in any way. To quantify this possibility I took two magnets I had in my metal toolbox from long ago. They are super powerful for their size (1/2"x 3/16" cylindrical). Doesn't seem like much but I decided to use two from a stack of about eight because that's the only way I could get enough leverage to pry them from the rest. I can' t use these to hold stuff to the refrigerator because they scratch the finish when I try to move them or take them off. If you got your finger stuck between two, they just might bite off a little piece of skin and give you a "bleeder".
I later found out that these magnets can overpower the earth's magnetic field at a considerable distance. Using my compass set flat on my desk, I was able to force the compass needle to go opposite the earth's field by holding the magnets six inches above the compass but they gave control back to the earth's field at eight inches.
Anyway, I laid the two in the balance pan in such ways that the north and south poles were aligned with the earth's magnetic field ... then I reversed the magnets and made them oppose. Here's the result:
1:46 PM 11/27/2006 North south magnetic experiment 10.43cm (+-) .02 ... reading on the balance with poles reversed: 10.44cm (+-) .02 Because the scale is reversed [28-27-26-... 1cm instead of 1-2-3...28cm] the second experiment shows that the magnet is lighter. Hence,it must be in the same direction as the earth's magnetic field. Testing with compass confirmed this.I did this little experiment three times and dutifully typed the results into notepad ... then ... proceeded to lose the data for the 2nd and 3rd experiments. How? Somehow ... I don't know. I learned a valuable lesson. Never put your primary data into a computer ... write it on a piece of paper ... then ... put it in the computer. Then, when you screw up, you will still be able to do the paperwork (typing) over again. But ... you gotta' have dem numbers.
I could do it over but it would be pointless because both the other experiments confirmed that the effect of the earth's magnetic field on my experiments will be all but unnoticeable. I could detect a difference ostensibly caused by the earth's magnetic field but just barely. We're talking about tenths of a millimeter here. I could see it but had to strain to do so.
Consequently, as a magnetometer, my setup sucks. But I want to measure a force on the scale of a one centimeter difference at least so a tenth of a millimeter won't upset anything. I can just ignore the earth's magnetic field here. It's just tooooooo damn weak.
Redoing the above 11/30/38
I realized yesterday the I had not used my vice grip to raise the center of gravity of my balance. So, I have resolved to do the same magnetometer calibration as the above but will make my gizmo much more sensitive if at all possible.
I put my vicegrip counter weight at the highest point and got these measurements:
N to N ... 13.90cm (+-).02 fields alined S to N ... 13.90cm (+-).02 fields opposed N to N ... 13.91cm (+-).02 fields alined S to N ... 13.92cm (+-).02 fields opposed With vicegrip and pipewrench N to S ... 13.83-13.98cm (+-).02 fields opposed N to N ... 13.80-14.00cm (+-).02 fields alinedMy vicegrip didn't pick up the center of gravity enough to make a definite call so I added a small pipe wrench to add some more weight. At one point I had it almost top heavy which made the apparatus unwieldy. So I lowered the duo to get a best possible compromize. I give two measurements in each test with the vicegrip-pipewrench combo because I could not get the balance to stop oscillating no matter how delicately I tried (with my little piece of paper). So, I settled for a high-low value. The truth is somewhere in between.
Despite my most dilligent efforts, I cannot say that I am able to detect any difference at all in the force on my magnet in the pan caused by the earth's gravitational field. I give up the magnetometer calibration and will henceforth ignore the earth's field in all subsequent experiments.
I had no idea that the earth's field was so incredibly weak ... but it is. I have now first hand knowledge. And I see also that any measurement at all in any experiment must yield at least a two millimeter difference to be considered at all noteworthy (and maybe more for any dynamic experiments).