Teach me stuff!

[extro…]

Some of them glow in the dark.

[Guest]

I really like the way it shows the little guy runnng away from the car. Pretty good assumption that if you ever find yourself shut in the trunk of a car, you gonna want to run like hell if you manage to get out.

[Doc Borodog]

The Most Important Thing You Will Learn Today

Most modern movie theaters have two separate wings, one to the right of the concessions, one to the left. Each wing typically has its own restrooms. Furthermore, movie show times are typically staggered to reduce congestion in the lobby as films end and patrons exit the theaters. If, like me, when you exit the theater you usually have to piss like a racehorse and hate getting caught in the crowd of similarly afflicted exants, proceed immediately to the other wing and use the restroom there, since it is unlikely that a film has just ended there, and there will be no wait. I always do this, and it has never failed me.

You are welcome.

[Guest]

Entertain your friends with these stupid quotes.

"Inbreeding is how we get championship horses."
- Carl Gunter, Louisiana state representative, explaining why he was fighting a proposed antiabortion bill that allowed abortion in cases of incest.

"Everything that can be invented has been invented."
- Charles H. Duell, Commissioner, U.S. Office of Patents, 1899.

"The concept is interesting and well-formed, but in order to earn better than a 'C,' the idea must be feasible."
- Yale University management professor in response to Fred Smith's paper proposing reliable overnight delivery service. (Smith went on to found Federal Express Corp.)

"Predictions are difficult, especially about the future."
- Yogi Berra, Baseball player

"Yes, maam? Right here, this lady. No, she! Yes, right, second row. Next to the guy in the blue shirt, holding her left hand up. It's a he? Sorry about that. Gotta be careful. I'm very sorry. Go ahead! I'm, excuse me, I'm very sorry. Go, ah, I, a thousand apologies, go ahead."
- George Bush Sr., Former U.S. President, at a press conference

"I have opinions of my own --strong opinions-- but I don't always agree with them."
- George Bush, former U.S. President

"It is white."
- George W. Bush, when asked what the White house was like by a student in East London

"If it weren't for electricity we'd all be watching television by candlelight."
- George Gobel

"I didn't realize I was in a Buddhist temple."
- Al Gore, former U.S. Vice President when asked about his illegal fundraising activities that took place in a Buddhist temple.

"Sure there have been injuries and deaths in boxing - but none of them serious."
- Alan Minter, Boxer

"I favor access to discrimination on the basis of sexual orientation."
- Ted Kenneday, US Senator

"Did people build this, or did Indians?"
- Tourist question at Mesa Verde National Park

[Quailman]

I learned something interesting today. Steelhead and Rainbow Trout are the same species. It makes it quite difficult to invoke the Endangered Species Act to protect the steelhead, which can grow to 20 pounds and spends part of its life in the ocean. The rainbow trout on grows to three or four pounds and lives its entire life in fresh water.

[MillerTime]

Bump.

Here's how to build a simple low-pass filter using a resistor and a capacitor. A low-pass filter, as the name implies, allows signals with low frequencies to pass through but blocks high-frequency signals.

A capacitor with capacitance C has impedance Z = 1/sC, where s is the frequency of the circuit. So, for very high frequencies, Z --> 0 and the capacitor acts as a short circuit. Similarly, for very low frequencies, Z --> infinity and the capacitor acts as an open circuit. To take advantage of this, set up your resistor and capacitor as follows:

[Lepton]

Gravitational Radiation

Maxwell's Equations, which describe electromagnetiism, and Einstein's Equations, which describe general relativity (gravity) have more than a few similiarities. One of the most impressive results from Maxwell's equations is the prediction of a electromagnetic wave that travels at ~300 000 km/s (light!). Well, the equations of general relativity can do the same sorts of things that Maxwell's equations can do, and so there's been speculation for a long time about the possibility of the existence of gravitational radiation.

These gravity waves would contract and expand spacetime itself as they pass. A wave that passes through a yardstick, for example, will enlarge the yardstick in comparison with a nearby yardstick. Incidentally, this is sort of how we are searching for them. The two yardsticks are replaced with two (kilometer-long) laser beams at right angles. When the laser beams are recombined, their relative phase will tell us whether one beam travelled further than the other. There are 4-km-long beams in Washington State and near New Orleans, and 2-km-long beams in Washington State and Pisa, Italy.

However, the process of detecting these waves is very difficult because they are so weak. The best sources would be colliding black holes and neutron stars. We think that, once the current detectors are running at full steam, we should see conclusive evidence of a gravity wave roughly once every few days.

For a phenomenon that hasn't been detected, they are causing a fair bit of exciting (and funding!). One reason for this is the Hulse-Taylor binary pulsar. Pulsars are neutron stars that spin extremely fast and with an extremely accurate frequency (better than our best atomic clocks, in some cases). The Hulse-Taylor object is two neutron stars that are spiralling towards each other. As they do this, their frequency is slowing down at exactly the right speed if the energy loss from the system were due to graviational radiation being generated from the system. Pretty strong evidence, imho.

Right now, I am working on a project that involves calculating how effective the gravity wave detectors would be for determining parameters of the sources (ie: neutron star/black hole masses, orbital configuration, distance, etc). The distance is especially important, because the systems that generate gravitational radiation should be visible from extremely far away (since gravity waves don't damp out by intervening matter like light does) and thus the sources of gravitational radiation can be used to determine the evolution of the size of the universe.

If you'd like to hear more, email me or post your questions here. I think it's fascinating stuff, but i suppose that I am biased. =]

[wordcross]

I find the concept fascinating as well, but not being a physicist, i think that this little blurb of yours is about as far as i'd be able to follow you (not to impugne upon your pedagogical abilities, but i'm just not that motivated)
_________________
Has anyone really been far even as decided to use even go want to do look more like?

[kennykiller*]

The word "vitamin" was suggested by the polish biochemist Casimir Funk. It consists of the latin words for life and nitrogenous (vita, amin).

[alphatango]

Lepton, I'd be extremely interested in seeing more info and the results of your calculations when you're done. As it happens, I'm currently taking a course on gravitational wave analysis, and I'm presenting a half-hour seminar tomorrow on a relevant paper.

This one's a little more involved than Lepton's description above; I'll try to explain the idea behind the paper in simple terms. Our method of detecting gravitational waves involves a number of test masses and lasers. Because of the size of the effect we're trying to see (very, very small!), we need to worry about something called quantum noise.

This quantum noise (think "quantum mechanics") can be thought of as coming from a few different sources. One of these is Heisenberg's uncertainty principle as applied to the test masses. (This is the one that says we can't know both a particle's position and its momentum to arbitrary precision.) Even though these things have a mass of many kilograms, where we wouldn't normally expect to see quantum effects, the size of the effect we're trying to measure is so small that we have to take the uncertainty introduced by the HUP into account.

Another source of quantum noise is that introduced by lasers, which inherently rely on the principles of quantum mechanics. Now, the interesting thing is this: when you calculate the noise introduced into your measurement from the test masses and the noise introduced by the laser, you get the same expression!

So despite calculating this noise from two completely different sources, we end up with the same answer. The obvious question is whether or not they're actually the same thing. There have been varying opinions on this over the past 30 years or so, but in 2003, a physicist named Vladmir Braginsky published a paper in which he claimed to have finally laid the question to rest. His answer is this: the two are indeed different, and under some circumstances, they can add, but if we're clever, we can design our experiment so that only the noise introduced by the laser affects our experiment, and not that introduced by the quantum mechanical description of the test masses.

I'm not sure how coherent and understandable that description is -- explaining stuff is a skill I'm trying to work on at the moment. Maybe I can clear it up a bit in response to any questions.
_________________
"Hanging is too good for a man who makes puns; he should be drawn and quoted." -- Fred Allen

Keeper of the Eternal Flame of the Inner Geek.

[Lepton*]

A good description, AT. The workaround for the quantum mechanical noise is absolutely fascinating and rather inspired.

I'm knee-deep in some statistics right now, but I'll let you know if I hit upon anything interesting.

[extropalopakettle]

Today I discovered that many English speaking Asians are under the mistaken impression that "prepone" is a word, meaning the opposite of "postpone". Example: "Can we prepone next Friday's meeting to Thursday or Wednesday?"

[Jack_Ian]

Prepone is a recent inclusion and is now a recognised valid English word.

[Lepton*]

[wordcross]

haha, postcipitation
_________________
Has anyone really been far even as decided to use even go want to do look more like?

[Lepton*]

Is no-one else willing to make the joke that only an East-Asian would ever think of "preponing" anything?

[wordcross]

well, they'd have to understand *why* it's a joke to want to post it.... anyone care to fill me in?
_________________
Has anyone really been far even as decided to use even go want to do look more like?

[Lepton*]

East Asians (especially the Japanese) stereotypically have a strong work ethic.

[extro...*]

I actually discovered the alleged word while in a room with about a dozen people, 2/3s Indian. That we (American English speaking people) don't even have a word that's the precise opposite of 'postpone' is perhaps scary.

[Antrax]

Just found out about this thread. Looks like "just for fun" only with facts. Neat.

It is impossible to write a computer algorithm that receives another computer program and input values to it, and correctly tells you if the program will run forever or not. Assuming such an algorithm exists creates a logical contradiction.
_________________
After years of disappointment with get rich quick schemes, I know I'm gonna get rich with this scheme. And quick!

[Samadhi]

The "halting problem." Read that in my discrete math book, pretty cool.
_________________
And he lived happily ever after. Except for the dieing at the end and the heartbreak in between.

[extro...*]

[Antrax]

extro: Kudos. I couldn't find a way to put Rice's theorem into simple words
_________________
After years of disappointment with get rich quick schemes, I know I'm gonna get rich with this scheme. And quick!

[Jack_Ian]

Antares is the 15th brightest star in the sky. It is more than 1000 light years away.

[Courk]

If Earth orbited Antares at the same distance from the surface it orbited the Sun, what would that look like in the sky?

[Jack_Ian]

I'd guess black. No atmosphere. (apart from the Sun, which would take up most of the sky during daytime)
The rest of Earth would be black too (once it cools down).

[Courk]

Hey, the Sun, Pollux, Arcturus, Betelgeuse, Aldebaran, and Antares are all the same ball!

How much would be "most of the sky"? 99% or more? That's what I'm picturing, and I have no idea if that's right.

[Jack_Ian]

[extro...*]

I've always liked those pics, but from looking at them I've always thought they're really poor quality reproductions (grainy, jpeg artifacts) of some really nice computer graphic originals. Have never been able to find the originals though.

[jadesmar]

[Jack_Ian]

[Jack_Ian]

The American civil War in 4 minutes

Coke machine Jackpot (I'd love to know if this actually works)

[MTGAP]

[MTGAP]

[MTGAP]

[MTGAP]

Antares is very big. How big is that compared to the solar system? Like, would it be bigger than Earth's orbit around the sun?
_________________
This statement is false.