Before I get flamed… yes, I know Star Trek is science fiction, but its concepts are supposed to be based on science fact. Then again, that may be the cause of my confusion. Supposedly, a matter-antimater reaction gives you THE most bang for your buck: 100% matter to energy conversion. But just HOW much energy are we talking about? I remember hearing someplace that enough energy is generated by an electron and a positron collision to power Manhattan for a month. Is this true? If so, how on Earth are these reactions contained in particle accelerators? And if antimatter DOES provide so much juice, why the hell aren’t we using it?
First of all, I think you may have been misled concerning the quantity of energy that is created on the combination of positron and electron.
Second, a big reason for not using this wonderful energy source is that we don’t have a lot of antimatter on hand. The antimatter that we have an opportunity to see within the accelerator’s chamber is created by expending even more energy to bang a few little bits together. Thus, we would need a huge powersource to create the fuel for a smaller powersource.
Now, the real reason I come to the messageboard-
Karen, that answer rocked! I don’t know how you did it, but your answer absolutely brimmed with your enthusiasm for particle physics. I haven’t thought about this stuff since college and you’ve made me want to learn more.
Here’s an antilink: ?derevocsid ti saw woH ?rettamitna si tahW
Livin’ on Tums, Vitamin E and Rogaine
Not even close. Take the famous equation:
E=mc^2
where m is your mass, in this case one electron and one positron. An electron has a mass of 9.11 x 10-31 kilogram, as does a positron. So…
E=2*(9.11 x 10-31 kg.)*(2.998 x 10^8 m/sec)^2
E=1.638 x 10-13 Joules
or 3.912 x 10^-14 calories
That’s enough energy to heat 1 gram of water 1/100 trillionths of a degree centigrade. In short, nothing to write home about.
Not even close. Take the famous equation:
E=mc^2
where m is your mass, in this case one electron and one positron. An electron has a mass of 9.11 x 10-31 kilogram, as does a positron. So…
E=2*(9.11 x 10-31 kg.)*(2.998 x 10^8 m/sec)^2
E=1.638 x 10-13 Joules
or 3.912 x 10^-14 calories
That’s enough energy to heat 1 gram of water 1/100 trillionths of a degree centigrade. In short, nothing to write home about.
…and he sat in his chair, his respiration quickening, his hands trembling, as a wave of raw terror enveloped him. It was at this moment the dread realization sank upon him–the curse of the double-post was real!
And, to make Karen’s prediction of the Kansas-Schoolboard-style answer on this message board come true:
(ahem)
The Straight Dope Mailbag article at http://www.straightdope.com/mailbag/mantimatter.html is an atheist plot to take God out of our schools! The matter-antimatter dissymmetry in the early universe doesn’t need any fancy-schmancy “CP violation between B+ and B- mesons” to describe it, if you’ll only accept in your heart that the LORD caused the imbalance to pave the way for His creation!
There. How’s that? 
Ok, so a small amount of antimater doesn’t generate THAT much juice. So how much WOULD it take to make a 1 megaton explosion? And would this amount of antimatter be more or less than the amount of plutonium to create the same effect? How about when compared to a hydrogen bomb?
I didn’t realize Al Gore was a particle physicist.
tracer: Nah, The Lord just created everything in six days. That “CP violation” egghead mumbo-jumbo is either: 1) ITSELF the plot by the antiChristians, or 2) an observation of a real effect which actually means nothing, like the fossils that were created in the (new) rock strata. (Just believe it.)
Klytus: I once heard (how’s that for good science?) that critical mass for fission purposes was around 10-15 lbs plutonium. (And that’s a lot smaller ball than you’d think.) Assuming that’s close, it’d get you a few tens of kilotons of yield. BUT only a small percentage of that plutonium (or deuterium/tritium in fusion devices) actually gets converted to energy, maybe at most in the ounces range??? Whatever the mass that ACTUALLY is converted to energy, that would be the same mass of matter-antimatter you’d need to get the same yield.
Seraphim: you’re right, that doesn’t sound like it would power manhattan for very long. Also, it’s in the wrong form. (How many calories to a Rogaine, anyway?)
An excellent point. A few measly positrons is insufficient to get manhattan lit for even a little while, let alone a whole month.
Get me a margarita and an anti-margarita. Then we’ll talk.
Livin’ on Tums, Vitamin E and Rogaine
Manhattan, your anti-link wins my prize for funniest posting of the day (so far)
I used to think that Linux geeks were strange. Then I followed the link to Karen’s paper that she mentions, and read the abstract.
Quote:
“Penguin, or loop, decays of B mesons induce effective flavor-changing neutral currents, which are forbidden at tree level in the Standard Model.”
Translation:
“Those rotten penguins aren’t allowed to fly, but they sure are tasty!”
Bob the Random Expert
“If we don’t have the answer, we’ll make one up.”
One kilogram of mass (so, 500g matter + 500g
antimatter) is about 10^17 (9*10^16) Joules,
orabout 20 megatons. If 10kg of fissionables
gets you 20 kilotons, total conversion is
about 10 000 times more efficient.
Note that making an antimatter bomb of this
size is not that easy, because when you slam
your pound of antimatter into your pound of
matter, the explosion where they touch blows
the remainder of the lumps outward so the
rest of the mass can’t react.
Why even put matter in your bomb? Chances are, the target will be matter too. (Not to mention the plane, the air, etc., etc.)
OK, just for fun…
In theory, could antimatter be gathered and contained in a matter universe? Is some sort of magnetic or “matter-neutral” bottle possible for this application?
-David
who reads way too much bad science-fiction
Dave asks:
In theory, could antimatter be gathered and contained in a matter universe? Is some sort of magnetic or “matter-neutral” bottle possible for this application?
Well that is exactly what the photon torpedoes do in Star Trek (IIRC): anti-matter contained in a magnetic shell that ruptures when it hits the target. And if it only takes 500g to give a 20 megaton yeild… ouch!
Manhattan, shouldn’t your link connect to
I am from Kansas. Well, I am originally from NY, anyhow-Just because the freakin’ school board has their heads AND their thumbs in their nether regions doesn’t mean that I won’t teach my kids the things they need to know. Besides-the Kansas voters will have their say Next November. And before anyone insults Kansas again-let me say that for Fred Phelps doesn’t speak for any of the sane people in Kansas. Really-it’s a nice place to live. Oh yeah-sorry about Bob Dole. And Todd Tiahrt. But we did give good things to the country-Pizza Hut, White Castle, &Joe Walsh to name a few. Plus the Cosmosphere is the greatest-they were chosen to do the restoration work on the Liberty Bell 7. If anyone asks if the dimes story in “The Right Stuff” is true, the answer is YES. They recovered dimes from the capsule. Oh, and sorry about Ross Perot-he isn’t from Kansas, but sorry anyway.
johnnyt: thanks
tracer: thanks (And, really, which is cooler? A God who folds his arms and blinks his eyes and the universe appears, or a God who crafts a finely honed, intricate set of physical laws such that the most esoteric penguin decays of teeny tiny quarks is especially relevant to the existence of the universe.)
SoulFrost: Antimatter is difficult to contain for very long. At your particle accelerators, for example, they try to keep the antimatter around at least until they can smash it into something. You do this by steering (charged) antimatter with powerful magnets into the center of a vacuum-filled tube. Of course, the kind of vacuum that mortals can achieve still contains lots of residual air molecules, and you can only steer charged particles if they are moving, so it doesn’t take long for the antimatter to collide with air or hit the sides of the pipe. At Fermilab, where the antiprotons are especially precious, they keep the antiprotons circulating in the ring for something like 8 hours. At the Cornell Electron Storage Ring, it’s much easier to dump the positrons after an hour or so and create a lot more new ones.