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nykkyo · Sep 30, 2013, 06:05 AM

After the scan. Is there any mass left after interactions?

ebaines · Sep 30, 2013, 08:45 AM

No - positron and electron annihilate each other, generating two gamma photons.

nykkyo · Sep 30, 2013, 11:34 AM

Originally Posted by ebaines

No - positron and electron annihilate each other, generating two gamma photons.

If annihilation produces E=mc^2 why does the body not explode?

ebaines · Sep 30, 2013, 01:19 PM

Do the math:

$E=mc^2$ , where m = mass of positron + mass of electron

$E = 2(9.1 \times x 10^{-31 }\ Kg) \times (3.0 \times 10^8 \ \frac m s )^2 = 1.6 \times 10 ^{-13} J$

So the energy of a positron-electron annihiliation is minuscule.

nykkyo · Sep 30, 2013, 02:28 PM

Originally Posted by ebaines

Do the math:

$E=mc^2$ , where m = mass of positron + mass of electron

$E = 2(9.1 \times x 10^{-31 }\ Kg) \times (3.0 \times 10^8 \ \frac m s )^2 = 1.6 \times 10 ^{-13} J$

So the energy of a positron-electron annihiliation is miniscule.

Since there are millios of annihilations why do we no see the sum(E)?
Sum(E) may not be explosive; but what about collateral thermal damage?

elscarta · Oct 6, 2013, 02:03 AM

Even if there were 100 million annihilations the total energy released would only be 1.6x10^-5 J or 16 microjoules. This is still a minuscule amount. Given that the specific heat of water is 4.2 joules per gram per degree C and assuming that all the energy was concentrated in 1 milligram of water ( in reality it's all over the body) it would only raise the temperature of that milligram of water by about 4thousandths of a degree C. Definitely no thermal damage occurring

nykkyo · Oct 6, 2013, 02:39 AM

Originally Posted by elscarta

Even if there were 100 million annihilations the total energy released would only be 1.6x10^-5 J or 16 microjoules. This is still a minuscule amount. Given that the specific heat of water is 4.2 joules per gram per degree C and assuming that all the energy was concentrated in 1 milligram of water ( in reality it's all over the body) it would only raise the temperature of that milligram of water by about 4thousandths of a degree C. Definitely no thermal damage occurring

Thanks