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Hi Jen, Thanks!
Enjoyed reading about Little Green Men & pulsars.
As for Dark Matter have you seen this post from Bee
and the bubbles in aero chocolate

or this fun one
about hitting CDs or DVDs with a laser pointer

PS - I notice you've gone to the darkside on the sidebar on the left. Must have good eyesight to read that faint (almost invisible) red print.
Well, at least I can make out the headings in 'bold' - lol! laters ...

Nice picture of the Crab nebula!

"In essence, a pulsar is a rotating neutron star. Just like a lighthouse, it emits twin beams of radiation that appear to pulse 30 times per second, producing a main pulse and an interpulse. That rotational energy is converted into electromagnetic energy, giving rise to the short, powerful burst of radio emissions observed by astronomers. However, no one is quite sure what the actual physical mechanism is that causes the energy conversion in the first place, hence, the continued interest of astronomers in studying these funny little objects. The current thinking is that it results from a collapsing soliton, and that collapse abruptly converts energy into electromagnetic radiation. What causes the collapse is still a bit of a mystery."

I did a course in this a decade ago but pulsar speculations didn't interest me, so I can't recall anything and don't have the lecture notes handy. But my thinking is that conservation of energy is key. Are you sure that the slowing down of spin (ie the loss of rotational kinetic energy of the pulsar) is exactly correlates to the radiation of electromagnetic waves?

Why isn't it simply a matter of material (gas, dust, whatever) being attracted into the pulsar, converted into energy, and the energy being radiated away in a beam as it rotates?

Think about the Earth! Electrically charged particles stream in from the sun, get trapped in the van Allen belts at 500-40,000 miles up (highest over the magnetic equator) and gradually trickle into the atmosphere at the magnetic poles where the magnetic field lines dip into the air and go to the poles on the ground (or below ground).

If the rotating neutron star is like the Earth, with a magnetic field, but with the magnetic poles located well off the axis of spin (unlike the Earth where the two axes are close to one another), then electrically charged radiation (ionized matter) streaming into the rotating neutron star will drain into the magnetic poles, which will heat up, emitting a beam of radio waves.

As it rotates, the beam will sweep around the sky like a lighthouse, as you explain, because it will emerge from the magnetic poles which don't coincide with the poles of rotation. I can't see any mystery!

A legibile sidebar! You have indeed seen the light :-)

Your crabby reader,
Stu Savory

Thanks for reporting on this. The COSMOS survey and Dark Matter are very big news! A contour map of mass distribution was in Sunday's post.
Dark mass within these voids was predicted in a brief student paper from 2004.

Is the crab nebula really in a far away galaxy? I thought it was fairly close...

Lablem, the Crab Nebula is in a galaxy (our galaxy) and it is far far away, 6300 light-years. " A galaxy far, far away" is a nice turn of phrase.

5245 BC wasn't that long ago- mid-Holocene, and not much more than a 14C halflife.

(I've never commented before, but I had to share)I loved the magnetic badges too! I heard complaints, but I was tired of maming holes in my shirts. This was the first time I was actually wearing a suit to the AAS meeting and would have gotten along fine with the lapel clip, but I prefered the magnets.

I am impressed that you are onto to NSF senior review stuff. It's the first mention of it that I have seen in the science blogsphere. The astro-community seems to be out of touch about its effects on the field as a whole. You even reported on the findings about Arecibo better than some of the main stream press who were under the impression that the NSF was closing it down.

As an aside, will you be at NSF when Sean gives a talk?

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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.