Units of measurement, constants, dimensional analysis, etc. From @JohnDCook
Joined April 2014
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Remember the time we lost a $330 million Mars orbiter due to unit conversion?
The Lockheed Martin propulsion team used pound-seconds; the JPL navigation team used Newton-seconds.
So the orbiter missed its orbit and burned up in Mars' atmosphere.
Oops.
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I’ve started a new Twitter account: @CryptographyTip.
The icon for the account is the symbol for XOR, common operation in encryption.
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Tutor: Let’s write down our units.
Student: Why bother? The problem is asking for m/s so we just tack on m/s when we’re done.
Tutor: I see. You either haven’t seen dimensional analysis before or haven’t solved a problem complex enough to see its usefulness. Let me show you.
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Using dimensional analysis to check probability calculations
johndcook.com/blog/2023/11/0…
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A chemist froze himself at -273.15°C.
Everyone thought that he was crazy, but he was 0K.
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It would be cool if there was a place on earth where g=π²=9.8696 m/s². But this article agupubs.onlinelibrary.wiley.… says the max value of g is approximately 9.83366 m/s² at a location in the Arctic Sea.
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1/3rd of an inch is a BARLEYCORN.
1/12th of an inch is a BUTTON.
1/20th of an inch is a POPPYSEED.
1/48th of an inch is a HAIR’S-BREADTH.
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The mass of an electron is about 900 quectograms.
johndcook.com/blog/2022/11/1…
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New SI prefixes and their etymologies
johndcook.com/blog/2022/11/1…
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Pop quiz:
(1) Draw an angle of 0.25 radians.
(2) Approximate the sine of 0.25 radians.
(3) Draw an angle of 22 degrees.
(4) Approximate the sine of 22 degrees.
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That's a very specific amount of sugar.
ALT Recipe calling for: 0.125 tsp celery salt 0.125 tsp mustard powder 0.25 tsp black pepper 0.5 cup water 0.5 tsp garlic powder 0.66666668653488 cup white sugar
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Happy Smoot Day! October 4, 1958, marks the day Oliver Smoot '62 was used by his fraternity brothers to measure the length of the Mass. Ave. bridge. mitsha.re/SYdfr
Image: Jenny Baek '25
ALT One Smoot is 1.7018 meters and 5.58333 feet. There are six boxes with a drawn illustration in each. Oliver Smoot is 1 smoot. The Harvard Bridge is 364.4 smoots. The Great Dome is 19.922 smoots in diameter. A beaver, MIT's mascot is usually between .54 and .72 smoots long. Rexy from Jurassic Park is 7.933 smoots long. Your list of responsibilities is infinite smoots.
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let's order strange things from NIST! first up is this jar of reference peanut butter. it's only $881 per jar!
