Archive for January 21st, 2009

Pictures at an Inauguration

No surprise that The Big Picture has some great photos of the inauguration.

The Inauguration of President Barack Obama

I stayed indoors and watched on TV. No way I was braving that throng.

Multiplying by 1

Unit conversions for mere mortals at Dot Physics

Are There Black Holes Hiding Under the Bed?


Entropy, Black Holes, and “Monster” states.

It is generally believed that black holes carry entropy. The need for that isn’t hard to understand: if you throw something into a black hole, its entropy shouldn’t just vanish since this would violate the second law. So an entropy must be assigned to the black hole. More precisely, the entropy is proportional to the surface area of the black holes, since this can be shown to be a quantity which only increases if black holes join, and this is also in agreement with the entropy one derives for a black hole from Hawking radiation. So, black holes have an entropy. But what does that mean? What are the microstates of the black hole? Or where are they? And why doesn’t the entropy depend on what was thrown into the black hole?

[I]f you create the monster state and let it evolve in time, it inevitably forms a black hole.

The the Impotence of Proofreading

Probably NSFW

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Complete transcript

Has this ever happened to you?
You work very horde on a paper for English clash
And then get a very glow raid (like a D or even a D=)
and all because you are the word¹s liverwurst spoiler.
Proofreading your peppers is a matter of the the utmost impotence.

This is a problem that affects manly, manly students.
I myself was such a bed spiller once upon a term
that my English teacher in my sophomoric year,
Mrs. Myth, said I would never get into a good colleague.
And that¹s all I wanted, just to get into a good colleague.

Of course its impotent to note that four proofreading two bee effective in catching substitution errors, you have too actually know that you’ve used the wrong word, you looser.

Deeper Than it Looks

My recent post on Haidinger’s brush reminded me of another optical phenomenon I have observed, and one that is a bit easier to see: the Pulfrich effect.

The Pulfrich effect is a phenomenon that gives the illusion of depth based on the response time of different light levels in the eye and how the brain interprets the delay. Lower light levels take longer to process, so if the image viewed by one eye is dimmer than the other, the signal from the dimmer view will lag in reaching your brain to be interpreted. With one eye darkened, something moving across your field of view will appear to get closer or further way.

When I first read about this, I consulted Wikipedia, which tells me

In the classic Pulfrich effect experiment a subject views a pendulum swinging in a plane perpendicular to the observer’s line of sight. When a neutral density filter (a darkened lens – typically gray) is placed in front of, say, the right eye the pendulum seems to take on an elliptical orbit, appearing closer as it swings toward the right and farther as it swings toward the left.

Well, gee, I work in an atomic physics lab. I can make a pendulum and have neutral density filters, so I went ahead an made up the experiment, using some scrap wire and a few optical-mount bases for the pendulum. And sure enough, with the right combination of filters (I think I ended up with ND=0.3 or 0.4) I was able to easily see the effect — the pendulum’s oscillation got closer at one end and further away at the other, and it reversed itself when I switched and darkened the other eye.

I wanted to show this off, so to make things a little easier I salvaged a damaged pair of sunglasses and popped one of the lenses shades out. (Not really lenses are they? OK, pedantic man says they are, albeit with an infinite focal length) That covers the eye better than the ND filter, which only has a 1″ diameter. I can use either the free eyepiece or the glasses. The biggest problem is getting people to look with both eyes — their natural tendency is to shut one eye and only look through the shade.