And now...
By ana (Fri Jan 22, 2010 at 12:12:42 PM EST) stuff, things (all tags)
Now, in stream of semi-consciousness form.*

---
*Who you callin' a semi?

So, what's up?

I've spent a lot of time lately doing sword-fighting games with the wii sports resort game we obtained over the holidays. There's this one with a whole Seven Samurai vibe going on; hundreds of little wii-people running at you with swords, and you get to kill them all. First Person Chopper for the win.

Occasionally the enhanced wiimote thingie loses its mind. There's a procedure for fixing that: point at the screen and poke the + button. Meanwhile some dude in black armor named Kyle comes and cuts you to ribbons. The physicist in me wonders if the gyro accelerometer thing gets into some kind of gimbal lock now and then. I suppose google would tell me...

Let me google that for you.

So, prolly not. (But don't you just love lmgtfy.com?)  No idea how the rotational sensor thing actually works.

Speaking of which, it's prolly be fun to learn more about how the GPS system works. We had a speculative conversation the other day over coffee about whether relativistic effects are important enough to consider.

Which in turn brings up a tale I read somewhere, about a physicist who collects old atomic clocks, and has the skill set required to keep them working. As part of a family vacation, and an object lesson for his daughters on how physics is actually done, he carefully synchronized all the clocks in his collection, put a few of them in his van, and took them up as high as you can drive on Mt. Rainier for two weeks. General relativity predicts that clocks run slower deeper in a gravitational potential well, and the effect is large enough to measure with such equipment. When he returned to Seattle, sure enough, the clocks left behind were slightly slower than the ones transported to high altitude.

And now, this.

When in doubt, write smut. That's more or less ana's law, for surviving NaNoWriMo. A small variation: write it someplace besides the main document. Involving, perhaps, characters who don't appear in the novel, or even live in the same universe.

I'm stuck in subscript hell. I have this code, written for historical reasons in a language called IDL (there's an open-source version called GDL) which automagically collapses a lot of the loops involved in using arrays. Except I can never quite keep track of what's what. Sorting doesn't actually rearrange anything; it just returns an array of indices into the original array. So I have this batch of events; you sort them in order of increasing energy, and then you wanna pick everything below the 20th percentile (or, well, you really wanna look at the cumulative distribution and read some number around 20 off the graph where it starts "getting steep", whatever that means exactly). And, uh, I get tangled up in my feet. Maybe I should write this in a real language.

I hate to say it, but I think on the whole it's more healthy for the country to have no super-majority anywhere, that obviates the need to consult members of the opposition. And that's pretty much all I have to say about that.

Genderfork sometimes has interesting things (like that one).

New band discovery of the week: Girlyman. They do folk-inspired stuff with close harmony that kind of reminds me of what I liked about ABBA and the Mamas and the Papas.

And now, it's actually more or less warm enough to go out for lunch, for the first time all week.

So should I set up a husi-compatible twitter identity? Do husi people use their nicks or their names or something else entirely?

I've been wanting to get out of my chair and do stuff in the evenings for a while, and the wii has helped with that. Maybe making music would be another thing I could do. Should re-string my 12-string guitar again sometime, and rebuild my callouses.

Right. Lunch. Seems like there was an "ask husi" kind of a thing I wanted to put in here, but, uh.  0:-/

On twitter by debacle (2.00 / 0) #1 Fri Jan 22, 2010 at 12:33:07 PM EST
All the good usernames are gone.

IF YOU HAVE TWO FIRLES THOROWNF MONEY ART SUOCIDE GIRLS STRIPPER HPW CAN YPUS :OSE?!?!?!?(elcevisides).

Yep. by barooo (2.00 / 0) #3 Fri Jan 22, 2010 at 12:43:29 PM EST
That's why I'm barooofnord over there.

man, i need a beefy taco now.
-gzt
[ Parent ]
Wiimote by ni (2.00 / 0) #2 Fri Jan 22, 2010 at 12:41:21 PM EST
I suspect they used a set of piezoelectric accelerometers. They were my plan when I thought I wanted to solve a similar problem a few years ago. They're dirt cheap, trivial to interface to, relatively high resolution and work pretty well.

I've seen some pretty good porn in which two young men got themselves in gimbal lock while sword-fighting.

"These days it seems like sometimes dreams of Italian hyper-gonadism are all a man's got to keep him going." -- CRwM

You said that camera was off! by mrgoat (4.00 / 2) #5 Fri Jan 22, 2010 at 12:47:34 PM EST

--top hat--
[ Parent ]
lmgtfy. by mrgoat (2.00 / 0) #4 Fri Jan 22, 2010 at 12:46:39 PM EST
And the less polite sister-site justfuckinggoogleit.com - which I can't check at work, as apparently it's blocked. I should get the guy who does the filter to check on that. Hey! That's me. But no - I won't. I'm in no mood for my shennanigans.

Wikipedia says yes on gps relativistic effects.

--top hat--

GPS & relativity by Herring (2.00 / 0) #6 Fri Jan 22, 2010 at 01:06:50 PM EST
Yes, it does.

Once, out of boredom, I calculated for Concorde whether a) the effect of time speeding up due to the altitude or b) the effect of time slowing due to the speed was greater. a wins. Just. If you took about 10^30 transatlantic flights on the Concorde, you'd age an extra couple of hours.

You can't inspire people with facts
- Small Gods

[ Parent ]
GPS by wiredog (2.00 / 0) #7 Fri Jan 22, 2010 at 02:38:49 PM EST
IIRC, from what Dad said (he worked with parts of it back in the 80's) the GPS system does take relativity into account. May even depend on it, but I'm not sure about that.

Earth First!
(We can strip mine the rest later.)

Time and Clocks by hulver (2.00 / 0) #8 Fri Jan 29, 2010 at 09:21:22 AM EST
I read the same thing about the physicist and the clocks as well. I did read about a clock so sensitive they had to re-calibrate it if they moved it up a level in the building.

Made me think, that if time is affected by mass, you might be able to use a super accurate clock as a mass detector. If it was accurate enough, you'd be able to use it to detect the difference in mass between two areas of stone. Then I thought you'd be able to use that to map out the difference in density of different parts of the great pyramid at Giza. Finally get an answer to where those little tunnels go, and are there any more passages anywhere.

That would be cool.

--
Cheese is not a hat. - clock
It's true. by ana (2.00 / 0) #9 Fri Jan 29, 2010 at 09:26:32 AM EST
There are easier ways to measure the local gravity field, though. ;-)

That said, yesterday I went to a talk by a radio astronomer who looks at millisecond pulsars... spinning neutron stars with rotation periods of a few milliseconds. They're really ultrastable clocks, like to a part in a trillion or something. Better than earth-based atomic clocks, they claim (not clear how you can know that...)

Anyway, his application for them was to look for gravitational waves. You can also see a host of other effects, like the gravitational redshift (time dilation) due to the gravitational field of the neutron star and its binary companion (if it has one). Really cool stuff.

"And this ... is a piece of Synergy." --Kellnerin

[ Parent ]
Very cool. by hulver (2.00 / 0) #10 Fri Jan 29, 2010 at 09:34:31 AM EST
I love physics, I just don't understand it as soon as equations become involved.

What easier ways are there for determining the density of rock, that might tell you about hidden passages? I'm pretty sure most sorts of waves are blocked by the amount of stone in the Great pyramid.
--
Cheese is not a hat. - clock
[ Parent ]
gravimeters by ana (2.00 / 0) #11 Fri Jan 29, 2010 at 10:09:09 AM EST
Something involving a simple pendulum, very accurately measured, and run allll over the surface of the pyramid and the surrounding area. Then to analyze the data, you'd first assume the whole thing was solid rock and calculate what you should see, and look at the differences, taking out one chamber after another. It'd be tricky.

Various people have tried looking for hidden chambers by setting up cosmic ray detectors in the known chambers under the pyramid. I don't think they learned much, but it's kind of like x-raying the structure.

"And this ... is a piece of Synergy." --Kellnerin

[ Parent ]
Ah by hulver (4.00 / 1) #12 Fri Jan 29, 2010 at 10:16:28 AM EST
Interesting. Thanks.
--
Cheese is not a hat. - clock
[ Parent ]