Re: Want to prove E=mc?? University labs should try this!

Tom Roberts <tjoberts137@sbcglobal.net> wrote:

On 11/23/24 1:12 AM, ProkaryoticCaspaseHomolog wrote:

[...] Of all the schemes I could think of whereby a DIY amateur scientist
can verify E=mc?, the only feasible one that I can think of is to
measure the energy of electron-positron annihilation.

 
You'll need a budget of at least $10,000.00 (probably more), and I doubt
you could obtain a useful resolution (say, 1%).
 

I'd need
the help of an expert former EE to put things together (hint, hint).

 
Or better, the assistance of an experimental particle physicist. But it
would be quite difficult to interest someone with the requisite
skills.... I have those skills, but am not interested.
 

Sealed sodium-22 positron sources are readily available for sale
online.

 
Yes. But I don't know if they will sell to an unaffiliated DIY
experimenter. Sales of radioactive objects are often restricted, and
they are usually prohibited in standard delivery channels (UPS, FedEx,
USPS, ...).
 

Calibrating the gamma-ray detectors will be the hard part.

 
Yes. You'll need several different gamma sources with known emission
energies.
 

Once
calibrated, I'd place two gamma-ray detectors 180 degrees apart
equidistant from an appropriate target. Connected to the detectors
will be a whole slew of equipment for coincidence counting, energy
measurement, etc. that the expert former EE will be responsible for.
 
With luck, the DIY experimenter will be able to confirm the
simultaneous emission of two 511 keV photons from each annililation.

 
This is certainly doable. Whether it is worthwhile is a quite different
issue -- personally I doubt it.
 
Note: this is the sort of experiment that could be in the syllabus of
the appropriate undergraduate lab class at a good college or university.
(They would use the equipment for several different experiments and many
students.)

Yes, but even if you could do it perfectly it is still an error
to claim that E=mc^2 has been verified.
Excercise for the kiddies: what does such an experiment verify nowadays,
(if anything)

Teaching them to interpret experiments correctly
is perhaps more useful than having them pottering about,

Jan