My Photo

Salut!

  • Jen-Luc Piquant sez: "They like us! They really like us!"

    "Explains physics to the layperson and specialist alike with abundant historical and cultural references."
    -- Exploratorium ("10 Cool Sites")

    "... polished and humorous..."
    -- Physics World

    "Takes 1 part pop culture, 1 part science, and mixes vigorously with a shakerful of passion."
    -- Typepad (Featured Blog)

    "In this elegantly written blog, stories about science and technology come to life as effortlessly as everyday chatter about politics, celebrities, and vacations."
    -- Fast Company ("The Top 10 Websites You've Never Heard Of")
Blog powered by Typepad
Bookmark and Share

« inside the actor's studio | Main | ring cycle »

Comments

Nobody loves Hitchhikers Guide more than me. It is with great distress that I have to point out a critical error in the book. The answer is 36, not 42. If the computers had gotten that right, everything else would have worked out OK. (Example: Rush L would have come in contact with his anti-Rush mass and disappeared by now.)

Interesting side note:

The Higgs mechanism gives mass to **elementary** particles, but the proton and neutron are not elementary. The majority of their mass comes from the forces binding their constituent quarks together! By Heisenberg's uncertainty principle, if you want your quarks to be localized in a tiny space, their momentum has to be, well, uncertain: the more you squeeze the probability distribution for finding a quark in a particular location in space, the more the probability distribution for its momentum will spread out. But if there's a chance for the momentum to be large, that means there's a chance the **energy** is large, and in relativity, energy and mass are the same thing -- that's the famous E = mc^2. So, having an attractive force bind three quarks together into a proton means that the proton will necessarily have mass, even if the quarks inside have none!

Frank Wilczek goes into a little more detail here:

http://www.physicstoday.org/vol-54/iss-6/p12.html

Now, the fun thing about the Higgs is that it can give mass to particles which would otherwise be indistinguishable, so that the **forces** carried by those particles behave in different ways. The W and Z bosons which carry the weak nuclear force have mass, while the photon which carries the electromagnetic force doesn't; we like the Higgs because it could explain this "electroweak symmetry breaking".

More from Wilczek here, along with other what-is-this-thing-called-Higgs essays, at a slightly less technical level:

http://www.hep.yorku.ca/what_is_higgs.html

(I don't mind pimping Wilczek's writing so much, since he's a cool guy. He was able to give a colloquium presentation to the MIT physics department even after he'd been up for two days since the call from the Nobel Prize people had come in.)

Am I behind the times in understanding that elementary particles are either a wave (massless) or particle depending on the experiment? Of course even a wave may be thought of as having mass in that it has energy and therefore mass due to E=mc2. Do I have some catching up to do?

A more useful way of expressing the statement is to say that elementary "particles" are neither waves nor particles. They behave like **nothing** in the familiar world, but rather choose to act in their own inimitable fashion. Sometimes, they're a little more like what we'd call "particles", and in other situations, we catch them behaving a little more like what we'd call "waves".

And yes, even when an electron or a proton is acting like a wave, it still has mass.

Mass can be a tricky concept: there's the **intrinsic** mass of an object, which is the sort of thing you find when you look up electrons or protons in an encyclopedia ("the electron mass is 9.1 times ten to the minus thirty-one kilograms"). This is the "rest mass", the mass you measure when the object is sitting still relative to you. The rest mass can be converted into energy: if you bring an electron and a positron together, they vanish in a flash of light. Two (or sometimes three) photons come zinging out, with a total energy equal to the rest mass of the two particles. That's E = mc^2.

However, if an object is moving relative to you, you'll measure its mass higher, augmented by a multiplicative factor which depends on its velocity. The total energy of a moving object isn't just its rest-mass energy, but also includes the **kinetic** energy which is due to its motion. Writing m for the rest mass and E for the total energy,

E = mc^2 + K.

Thanks, I see I do have some more reading to do.

Our fellow physics blogger over at Skulls in the Stars has been writing a good series of background articles on relativity and how it was discovered:

http://skullsinthestars.com/category/relativity/

The best book I've found for "getting a feel" for quantum mechanics without having one's head explode is Richard Feynman's **QED: The Strange Theory of Light and Matter**. It's moderately old (1980s), but because it covers stuff which had been very well worked out, almost all of the contents are still good. The only two addenda I can think of off the top of my head are that the top quark has been discovered (1995) and that some conceptual advances in quantum field theory have made the process of "renormalization" (what Feynman calls "sweeping the infinities under the rug") less problematic. The former is a minor addition, and the latter is a technical point which doesn't really matter if you're trying to get a handle on the basic ideas of quantum physics.

Since being pedantic is what I do both for a living and for a hobby, I feel obliged to point out that although the Standard Model requires the Higgs to give a mass (selectively) to bosons, it is not required to do the same to fermions (although it can) and is thus only half a "god" particle. So think of it, maybe, as the father and half the holy ghost.

All this input is much appreciated, thanks people! And Blake, not only do I share your enthusiasm for QED (even I could understand it), but also, thanks for plugging Skulls in the Stars, one of my new fave physics blogs. ONe of these days I'll find the time to seriously overhaul my long-outdated blogroll...

The comments to this entry are closed.

Twitter Updates

    follow me on Twitter

    Physics Cocktails

    • Heavy G
      The perfect pick-me-up when gravity gets you down.
      2 oz Tequila
      2 oz Triple sec
      2 oz Rose's sweetened lime juice
      7-Up or Sprite
      Mix tequila, triple sec and lime juice in a shaker and pour into a margarita glass. (Salted rim and ice are optional.) Top off with 7-Up/Sprite and let the weight of the world lift off your shoulders.
    • Listening to the Drums of Feynman
      The perfect nightcap after a long day struggling with QED equations.
      1 oz dark rum
      1/2 oz light rum
      1 oz Tia Maria
      2 oz light cream
      Crushed ice
      1/8 tsp ground nutmeg
      In a shaker half-filled with ice, combine the dark and light rum, Tia Maria, and cream. Shake well. Strain into an old fashioned glass almost filled with crushed ice. Dust with the nutmeg, and serve. Bongos optional.
    • Combustible Edison
      Electrify your friends with amazing pyrotechnics!
      2 oz brandy
      1 oz Campari
      1 oz fresh lemon juice
      Combine Campari and lemon juice in shaker filled with cracked ice. Shake and strain into chilled cocktail glass. Heat brandy in chafing dish, then ignite and pour into glass. Cocktail Go BOOM! Plus, Fire = Pretty!
    • Hiroshima Bomber
      Dr. Strangelove's drink of choice.
      3/4 Triple sec
      1/4 oz Bailey's Irish Cream
      2-3 drops Grenadine
      Fill shot glass 3/4 with Triple Sec. Layer Bailey's on top. Drop Grenadine in center of shot; it should billow up like a mushroom cloud. Remember to "duck and cover."
    • Mad Scientist
      Any mad scientist will tell you that flames make drinking more fun. What good is science if no one gets hurt?
      1 oz Midori melon liqueur
      1-1/2 oz sour mix
      1 splash soda water
      151 proof rum
      Mix melon liqueur, sour mix and soda water with ice in shaker. Shake and strain into martini glass. Top with rum and ignite. Try to take over the world.
    • Laser Beam
      Warning: may result in amplified stimulated emission.
      1 oz Southern Comfort
      1/2 oz Amaretto
      1/2 oz sloe gin
      1/2 oz vodka
      1/2 oz Triple sec
      7 oz orange juice
      Combine all liquor in a full glass of ice. Shake well. Garnish with orange and cherry. Serve to attractive target of choice.
    • Quantum Theory
      Guaranteed to collapse your wave function:
      3/4 oz Rum
      1/2 oz Strega
      1/4 oz Grand Marnier
      2 oz Pineapple juice
      Fill with Sweet and sour
      Pour rum, strega and Grand Marnier into a collins glass. Add pineapple and fill with sweet and sour. Sip until all the day's super-positioned states disappear.
    • The Black Hole
      So called because after one of these, you have already passed the event horizon of inebriation.
      1 oz. Kahlua
      1 oz. vodka
      .5 oz. Cointreau or Triple Sec
      .5 oz. dark rum
      .5 oz. Amaretto
      Pour into an old-fashioned glass over (scant) ice. Stir gently. Watch time slow.