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The Flying Dutchman
12-14-2011, 02:59 PM
From here (http://www.care2.com/causes/physicists-zero-in-on-glimpsing-the-god-particle.html)

The putative particle weighs in at about 125 billion electron volts, about 125 times heavier than a proton and 500,000 times heavier than an electron, according to one team of 3,000 physicists, known as Atlas, for the name of their particle detector. The other equally large team, known as C.M.S. — for their detector, the Compact Muon Solenoid — found bumps in their data corresponding to a mass of about 124 billion electron volts.

1. How did a unit of energy, the electron volt become a unit of mass ?

2. How is it that a proton that colides and breaks up into sub particles produces a particle that weighs 125 times heavier ?

OldGuy
12-14-2011, 03:16 PM
1. When they give a mass in energy terms, they are relying on the relation E = mc2. Sometimes you explicitly see masses stated as 125 GeV/c2.

2. When you get the proton moving very fast it has a lot more "mass" than its rest mass since its kinetic energy has a mass equivalent.

Sunspace
12-14-2011, 03:43 PM
1. How did a unit of energy, the electron volt become a unit of mass ?Energy and mass are aspects of the same thing, is the way we learned it in high school. E=mc2, and all that, where E is the energy, m is the mass, and c is defined as the speed of light in a vacuum (3 * 108 m/s). (And I was ridiculously thrilled to be actually using that famous equation in real homework in chemistry...)

You can measure mass in units of energy, or energy in units of mass. E=mc2, so one gram expressed in units of energy (joules) is 1 g * c2, or 1 g * ((3 * 108 m/s) 2 = 9*1016 J. Which is enough energy to take around 35 million tonnes of water from room temperature to the boiling point, and then boil it. :eek:

There's a lot of energy locked up in each piece of mass... and that's just the "rest mass" (see below).
2. How is it that a proton that colides and breaks up into sub particles produces a particle that weighs 125 times heavier ?'Cause it's going very fast. It has kinetic energy (energy of motion) as well as rest mass ( the mass that remains around when something isn't moving). The kinetic energy is basically all the energy put into the particle by the pushes that got it up to speed. When the particle is going within an eyelash of the speed of light, as they do in these experiments, the kinetic energy of the particle is much more than the energy present as the particle's rest mass.

So it's no surprise that when these particles hit head-on, there's enough energy in the smash to create all sorts of unexpected things. (Yes, they hit particles head-on in these experiments. That must take excellent aiming skills...) It's like the difference between two cars rolling up to one another and gently tapping the bumpers versus hitting head on and creating noise and sparks and bending things and throwing stuff around... but even more so.

The Flying Dutchman
12-14-2011, 05:20 PM
Thanx guys... so one gram expressed in units of energy (joules) is 1 g * c2, or 1 g * ((3 * 108 m/s) 2 = 9*1016 J. Which is enough energy to take around 35 million tonnes of water from room temperature to the boiling point, and then boil it. :eek:

It don't often use the expression, but that is awesome.

Sunspace
12-14-2011, 07:28 PM
It don't often use the expression, but that is awesome.Isn't it? I thought my math was off at first, so I looked up the explosion of the Hiroshima bomb. According to Wikipedia (http://en.wikipedia.org/wiki/Little_Boy), the Little Boy bomb converted "600 to 860 milligrams" of matter to energy, and that was enough to incinerate a city and kill more than a hundred thousand people. It yielded between "54 and 75 TJ", or 5.4*1013 to 7.5*1013 joules. So that's roughly within the same few orders of magnitude.

Pasta
12-14-2011, 09:33 PM
1. When they give a mass in energy terms, they are relying on the relation E = mc2. Sometimes you explicitly see masses stated as 125 GeV/c2.
OldGuy is correct in essence, but the more extended answer is that things are being expressed in a different unit system, one where c=1 by definition. This makes time and distance have the same units, and it makes energy and mass (and momentum) have the same units.