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Topic: This Week's Finds in Mathematical Physics (Week 227)
Replies: 9   Last Post: Mar 18, 2006 10:52 PM

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John Baez

Posts: 542
Registered: 12/6/04
Re: This Week's Finds in Mathematical Physics (Week 227)
Posted: Mar 18, 2006 10:52 PM
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In article <>,
Gerry Myerson <> wrote:

> John Baez wrote:

>> An EeV is an "exa-electron-volt", which is the energy an electron picks up
>> going through a potential of 10^18 volts. 300 Eev is about 50 joules -
>> the energy of a one-kilogram mass moving at 10 meters/second, presumably
>> all packed into one particle! Nobody knows how such high energies are
>> attained -

>How fast does, say, a proton have to be going to have that much energy?

It's sort of tiresome figuring out the right number of nines, so I won't
bother with the precise figure, but it's something like .999999...
times the speed of light. Fast.

Too vague for you?

The mass-energy of a proton is very roughly 1000 MeV. This particular
proton had an energy of 300 EeV. So, find the velocity v, as a fraction
of the speed of light, such that

300 EeV / 1000 MeV = 1/sqrt(1 - v^2)

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