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3443 clicks; posted to Geek » on 29 Sep 2013 at 5:30 PM (4 years ago)   |   Favorite    |   share:    more»

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 1 vote:

Bacontastesgood: Professor Science: Highlights include the requirements for a 60 MeV electron beam to start, and a Ti:sapphire laser illuminating the chip.  Neat trick, though, and I hope to see it develop.

Thanks for clarifying.  To dumb it back down again, in addition to the grain-of-rice sized thing, you need a block-long accelerator and a half million bucks worth of optics.  This is in the parlance an 'afterburner'.  You still need the jet.

Better than requiring the combined effort and resources of an entire continent.  A half million dollars is a drop in the bucket to many research universities, as well as many companies.

LrdPhoenix: If you divide by the speed of light again, you get just mass left over and no length/time, so you can also use eV/c2 as a unit of mass, but once again, by reducing c to 1, it cancels out and they just use eV as the units again.

Just an addenda on this: If a unit of energy can be divided by c2 to get a unit of mass then, m = E/c2.

If you solve for E then you get E = mc2
 1 vote:

LrdPhoenix: simplicimus: I'm not really all that stupid, but what meaning has been assigned to acceleration? Pretty sure it doesn't refer to speed of electrons.

Particle physics often measures momentum in electron volts.

The electron volt unit, a unit of energy, has dimensions, which are mass*length2/time2, like velocity has the dimensions length/time like miles/hour or km/second.

If you divide electron volts by the speed of light, which is a velocity, you get mass * length / time (by cancelling out dimensions) as the resulting dimensions and eV/c as the units, which are the same dimensions as units of momentum (since momentum is mass * velocity, which again is distance/time).

Then with some math, they set the speed of light to a constant of 1 rather than a big long number, so the c on eV/c might as well not be there, so you just get it in electron volts.

If you divide by the speed of light again, you get just mass left over and no length/time, so you can also use eV/c2 as a unit of mass, but once again, by reducing c to 1, it cancels out and they just use eV as the units again.

Also note, the reason the energy units have dimensions of mass * length2/time2 is that the equation for energy (or work as it's usually known) is Work = force * distance.  The equation for force is F = mass * acceleration, so Work =  mass * acceleration * distance.  And acceleration is change in velocity/change in time. So, if you put it all together you get:
Work = mass * (distance/time)/time * distance (just ignoring the deltas on acceleration), and with some simplification you get Work (or Energy) = mass * distance2 / time2
 1 vote:
Make this simple for me. Am I going to be able to get these or not?

 1 vote:

simplicimus: I'm not really all that stupid, but what meaning has been assigned to acceleration? Pretty sure it doesn't refer to speed of electrons.

Particle physics often measures momentum in electron volts.

The electron volt unit, a unit of energy, has dimensions, which are mass*length2/time2, like velocity has the dimensions length/time like miles/hour or km/second.

If you divide electron volts by the speed of light, which is a velocity, you get mass * length / time (by cancelling out dimensions) as the resulting dimensions and eV/c as the units, which are the same dimensions as units of momentum (since momentum is mass * velocity, which again is distance/time).

Then with some math, they set the speed of light to a constant of 1 rather than a big long number, so the c on eV/c might as well not be there, so you just get it in electron volts.

If you divide by the speed of light again, you get just mass left over and no length/time, so you can also use eV/c2 as a unit of mass, but once again, by reducing c to 1, it cancels out and they just use eV as the units again.
 1 vote:

doglover: clocking in 300 million electron volts per meter

Methinks the author of the article doesn't understand units.

300 million electron volts per meter?  Wow!  With that kind of power, she could make the Kessel Run in less than 12 parsecs!
 1 vote:
So?  I guarantee you, nothing will happen with it.  The great advances of the past that have led to cell phones, Internet, and so forth are over.  Now, the only way this thing will see the light of day in any kind of consumer aplication is if some corporation figures out how to make tons of money on it, while simultaneously locking out everyone else.
 1 vote:
clocking in 300 million electron volts per meter

Methinks the author of the article doesn't understand units.

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