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The Physics of Space Battles

tibit Re:It seems to me... (446 comments)

When pigs fly. That's my take on it.

37 minutes ago
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David Cameron Says Brits Should Be Taught Imperial Measures

tibit Re:Idiot (786 comments)

In the US, this is not a practical issue. You go to a store and get a measuring cup. I haven't really had a need to know exactly how many ml is in such a cup... It also doesn't matter that other "cup" definitions exist out there. When you cook, you go by the measuring cup you get from the store. When you are a manufacturer of such cups, you should know what you're doing. Easy.

7 hours ago
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David Cameron Says Brits Should Be Taught Imperial Measures

tibit Re:Idiot (786 comments)

US sticks of butter are graduated in tablespoons on their wrapper. There's two tablespoons to an ounce, and 8 oz to a cup. So if a recipe calls, for, say 1/4 cup of butter (2oz), you know it's 4 "notches" on the butter stick's graduation, or 4 Tbsp of butter.

7 hours ago
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David Cameron Says Brits Should Be Taught Imperial Measures

tibit Re:Idiot (786 comments)

Measuring by weight has one significant benefit: you have much less washing up to do. No measuring cups/spoons to wash. When I mix ingredients, the mixing bowl sits on a wiiboard repurposed to be a high-capacity kitchen scale that reads down to 0.1g and has accuracy down to 1g over 100kg. When I try out a recipe for the first time, I simply note the weight of each ingredient as measured by volume, and use the weights from that point onwards. BTW, the readout I prefer is in lbs/oz, not grams :)

7 hours ago
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David Cameron Says Brits Should Be Taught Imperial Measures

tibit Re:Universality (786 comments)

I couldn't agree more. There are, basically, more important problems than that. All imperial measures are defined in terms of SI units anyway. Big deal.

8 hours ago
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David Cameron Says Brits Should Be Taught Imperial Measures

tibit Re: Simple answer (786 comments)

Let's not forget that Centigrade and degrees Celsius are not the same thing. They are almost the same, but not quite.

8 hours ago
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The Physics of Space Battles

tibit Re: Umm no (446 comments)

Optics that work well with far infrared targets are much bulkier than radar optics. It's much, much easier to deal with centimeter waves than micrometer waves :)

8 hours ago
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Apple Fixes Shellshock In OS X

tibit Re:Ahh yes (163 comments)

Only some very awkward C++ would not eliminate this. I have lots and lots of C++ code where buffer overflows and dangling pointers are statically provable not to exist, and it's very obvious by inspection that it can't but be so. All it takes is proper libraries and proper approach. Yes, I see way too much C++ code written like it was Pascal-with-objects. Sigh.

8 hours ago
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David Cameron Says Brits Should Be Taught Imperial Measures

tibit Re:FP? (786 comments)

Who said the 1/2" is rounded? :)

8 hours ago
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David Cameron Says Brits Should Be Taught Imperial Measures

tibit Re:FP? (786 comments)

No, I do not. Sorry to disappoint. Whenever I do construction around the house, I do this so often it's second nature.

8 hours ago
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David Cameron Says Brits Should Be Taught Imperial Measures

tibit Re:FP? (786 comments)

Contractors use calculators or apps that handle that sort of a thing. The ones who are better at mental math simply do the mental math. No biggie. It only takes practice. Being a metric guy for 20 years, I had no trouble building some cabinetry, 20 years later, doing the whole thing in binary-base fractional inches. Anyone who's a computer geek should have no trouble there.

If you seriously think that most things are actually built down to a mm, you're crazy. Nobody in residential wood frame construction does it. Especially not when your materials are as dimensionally crazy as wood framing. Protip: studs aren't straight. If you're at the lumber yard, I wouldn't bet on 0.1% being within 1mm of the imaginary 3D box of ideal 2x4 straight lumber. Yeah, Europe doesn't have enough forest cover to build out of wood. Big deal, nobody builds down to 1mm using bricks and mortar either. I'd say that most US homes are built to the nearest 1/2 inch, if that. Heck, frame openings for windows are usually sized for the particular window being installed, not to any standard opening size. When it's time to replace the windows 30 years later, you end up swearing a lot :) I know that first hand.

8 hours ago
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David Cameron Says Brits Should Be Taught Imperial Measures

tibit Re:FP? (786 comments)

Look, I grew up on metric. I like imperial measurements for their practicality. I don't think why would I care how many feet are there in a yard, or a mile, or whatever. Feet and inches are used in contractor trade. You use them when building homes. I never, not once, had a need to convert between feet and miles. The metric system is great if you want to do back-of-the-envelope what if computations. For use within any given field of trade, its usefulness is diminished. Whether you know your furnace's output in kW or BTUs doesn't really matter - both are equally arbitrary and for an HVAC guy, whether a technician or an engineer, it doesn't make any difference what the units are.

Now, if it was up to me, would I want US and UK to go to metric overnight. Sure. But I think that in spite of recognizing the overblown arguments as to how "bad" the imperial system is. It's not. Not in practice.

8 hours ago
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David Cameron Says Brits Should Be Taught Imperial Measures

tibit Re:FP? (786 comments)

I don't think there's anything super-intelligent to it. When you've got a 5-digit number, you need a thousand separator anyway. Whether it's a thousand separator or a decimal point is a matter of preference, but you need *something* to make it easier to read. The imperial system makes it even more readable, since for single-family homes you typically have 2-3 digit number of feet, 1-2 digit number of inches, and then a base-2 fraction of inches. 5'6"1/2 is plenty readable to me. That's 1689mm. Both are 4 digits long. I don't see a clear advantage of using mm.

10 hours ago
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David Cameron Says Brits Should Be Taught Imperial Measures

tibit Re:FP? (786 comments)

More like 40x90mm. Seriously.

10 hours ago
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HP Introduces Sub-$100 Windows Tablet

tibit Re:So, now HP sells a tablet (181 comments)

Breaking down into manageable units shouldn't be conflated with iteration/repetition. Divide and conquer isn't a for loop. Integration by parts isn't a for loop either. The approach for long arithmetics taught in school is quite unproductive, actually, since if you *really* want to multiply and divide quickly by hand, you should be more like Feynman, not like the Japanese abacus guy. By the time I got into high school, I usually was much faster at long arithmetic by doing iterative approximations and trying to extract statements about the properties of the problem. For example, looking at factors, at constraints that must hold for values of some digits, etc. That's what teaches you actual mathematics. Doing long arithmetics, fraction reductions and similar menial stuff for weeks and weeks is a waste of time and I have not read any convincing arguments otherwise. It's a stand-in for unimaginativeness and lack of deep mathematical understanding among the teachers and the curriculum authors. The only reason we do it is because there was a time when it was useful. It's only the lack of historical context that makes people who should know better repeat ad nauseam that "we should do it cuz' it's good". No, it's no good at all. It keeps you back from learning more mathematics.

11 hours ago
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Grooveshark Found Guilty of Massive Copyright Infringement

tibit Re:Now sharing music is illegal? (161 comments)

I hate to be obvious, but in the U.S. at least, all "recent" music is subject to copyright protection unless the creator specifically places it into public domain (or it is so under law, like works of U.S. gov't employees). To distribute any such music at all you need a license.

yesterday
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HP Introduces Sub-$100 Windows Tablet

tibit Re:Battery life? (181 comments)

And to think that my friend was using a 2009 macbook with 2GB of RAM and a 128GB SSD until a few months ago. Now it has 4GB of RAM, and while doing development work (Eclipse and another copy of JVM running) and having two accounts logged in, both with Safari open, the swap sits unused, and there's a few pageouts but not too many (a couple thousand per hour)... And this is on Mavericks, which has higher resource needs compared to Snow Leopard.

My kid uses a MBP of similar vintage with 8GB of RAM. It works great even though I'm can't seem to bother to replace the mechanical hard drive with an SSD. On Mavericks you essentially either need an SSD or lots of RAM to cache the underperforming hard drive. Mavericks seems to access the hard drive in such a way that makes mechanical drives seem very sluggish. Minecraft, multiple instances of youtube, etc. -- all work great.

yesterday
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HP Introduces Sub-$100 Windows Tablet

tibit Re:No touchscreen by default (181 comments)

It concerns me somewhat that it didn't make you stop, think, re-read and understand. Because I surely did and I find it unthinkable that others wouldn't. Scary, even.

yesterday
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HP Introduces Sub-$100 Windows Tablet

tibit Re:So, now HP sells a tablet (181 comments)

My worry has been that kids in grade schools waste a lot of time doing menial arithmetic while they could have been - gasp - actually learning more advanced math instead. Like, you know, shit that one can use later in college. I really wish I didn't need to do all that long division/multiplication etc. - it was really pointless. I used to believe that it was good. I now know better. The whole reason for menial arithmetic was the Victorian-era-called-need for civil servants - back when nobody had a spreadsheet application to run the numbers back then. A civil servant doing manual math these days in a 1st world country would be probably reprimanded for wasting his or her time.

yesterday
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HP Introduces Sub-$100 Windows Tablet

tibit Re:now that its not $700 (181 comments)

It's probably good enough to do software development on. I can't see it being any slower, CPU-wise, than a Core II duo 5 year old MBP, never mind that it has 2 more cores. It seems like it could be a very good deal - hook up to an external monitor and BT keyboard/mouse and it should be a screamer. It's astonishing how good consumer-grade hardware is these days.

yesterday

Submissions

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MRI Magnets Cause Nystagmus

tibit tibit writes  |  about 3 years ago

tibit writes "In an interesting twist on "it's so old it's new again", Johns Hopkins researchers led by Dale Roberts found what must have been causing much confusion for doctors the world over: strong external magnetic field can stimulate the semicircular canals, causing vertigo and nystagmus (pendular eye motion). It's a textbook case of Lorentz force in action: our angular rate gyros, the semicircular canals in the middle ear, filled with endolymph, have a ionic current flowing across. In magnetic field, the current produces a force that pushes the lymph along the channel, causing stimulation of the cupula — a pressure sensor at the end of the channel. This is interpreted by the brain as rotation of head in space, and causes a nystagmus that's supposed to stabilize the image on the retina. Of course the subject is laying down and not spinning in space, and the mismatch between inertial measurements coming from the ear and real situation causes vertigo."
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