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Nice discussion on pool! Being something of a fan(atic) myself, I was pretty stoked to see something mentioned on this blog related to pool (haven't gone through all the postings yet so I may have missed something.) To be a reasonably good pool player one must have at least a minimal understanding of the physics involved in the game, particularly in the way the balls interact with each other, the rails, and the cloth. Jim Loy's site does a great job of discussing these things, but the second site is a little harder to take seriously (every reasonably experienced pool player knows that the six ball is GREEN, for instance.) It has some impressive equations (which are WAY over my head as an armchair physicist) but some things seem to be missing in the ball collision example. One page describes the angle of deflection as being roughly 90 degrees (the tangent line at the point of impact.) While this is true at the instant of contact, it rarely remains that way for very long. The examples don't speak to the angular momentum of the cue ball (the draw, follow, or side spin you mention in your post) or the effects of throw (the effect that cue ball side spin has on an object ball at the moment of impact.) These things cause not only a change in the path of the cue ball but also in the path of the object ball as well.

I've been a long time armchair physicist, which is to say I find the subject of physics fascinating and study it as it relates to other interests, but have no formal education in it beyond the one high school class I took. For instance, as a windsurfer, it's good to know the physics of wind and water. For the longest time I would wipe out thinking that the board's fin had ripped off completely when it actually hadn't. (Imagine suddenly finding yourself sliding sideways across the water at 20MPH praying that you don't catch the leading edge. It does loosen the sphincter somewhat.) It was fascinating to discover the reason it occurs is related to the reason why military submariners don't want to spin the propellers on their subs too fast (cavitation is the scientific term.)

All that being said, I really enjoy reading your blog posts and learning about various other aspects of math/science that I wouldn't normally go research on my own.


Ah, who cares about the science? I wanted to hear more about Witchblade! I too have been watching it lately and am happy to discover that I missed many of the first season when it aired.

I really appreciate your blog as an educational tool for my friends (I have advanced degrees in geophysics, so I benefit less, but still enjoy it).

There's this bracelet, see, with mystical powers.... :) Actually, there IS a bit of temporal physics involved, i.e., when Sara undergoes the Periculum (a bizarre test of worthiness) and is told that while we think of time as linear, it's really more like individual frames in a film. It's our perception that makes it appear to be linear and continuous, when in fact one moment can touch another moment ("frame") at any time. I think brian Greene said something similar in THE FABRIC OF THE COSMOS, without all the mystical trappings. :)

And I think we could probably come up with a hypothetical type of material out of which the Witchblade might have been made. "A branch from the Tree of Good and Evil" is just a bit too vague.... Ferromagnetic liquids/solids might be a contender...

At least I gave you a saucy shot of Sara Pezzini!

A deterministic spherical-cow analysis of billiards is fine, and so is quantum billiards, but you've omitted one other fashionble analysis. Chaos theory needs to be represented:

"Even the motion of a frictionless billiard ball becomes completely unpredictable after only 11 collisions, owing to the uncertainty principle's limit on describing its initial state."

This is from a really splendid obituary for Edward N. Lorenz, by Kerry Emanuel, Science 23 May 2008: Vol. 320. no. 5879, p. 1025;

Can't speak for anyone else, but I've been waiting for years (not being a physicist and exposed to this sort of thing in journals) to see exactly this merger of chaos and uncertainty.

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    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.