31 Aug 15:48

Feynman Lectures Released Free Online

by samzenpus
Anna Merikin writes In 1964, Richard Feynman delivered a series of seven hour-long lectures at Cornell University which were recorded by the BBC, and in 2009 (with a little help from Bill Gates), were released to the public. The three-volume set may be the most popular collection of physics books ever written, and now the complete online edition has been made available in HTML 5 through a collaboration between Caltech (where Feyman first delivered these talks, in the early 1960s) and The Feynman Lectures Website. The online edition is "high quality up-to-date copy of Feynman's legendary lectures," and, thanks to the implementation of scalable vector graphics, "has been designed for ease of reading on devices of any size or shape; text, figures and equations can all be zoomed without degradation." Volume I deals mainly with mechanics, radiation and heat; Volume II with electromagnetism and matter; and Volume III with quantum mechanics. Last year we told you when Volume I was made available. It's great to see the rest added.

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31 Aug 04:33

kaminas-spirit: House dressed as a house painting a house on a...


House dressed as a house painting a house on a house

30 Aug 15:54

Reformatting a Machine 125 Million Miles Away

by Soulskill
An anonymous reader writes: NASA's Opportunity rover has been rolling around the surface of Mars for over 10 years. It's still performing scientific observations, but the mission team has been dealing with a problem: the rover keeps rebooting. It's happened a dozen times this month, and the process is a bit more involved than rebooting a typical computer. It takes a day or two to get back into operation every time. To try and fix this, the Opportunity team is planning a tricky operation: reformatting the flash memory from 125 million miles away. "Preparations include downloading to Earth all useful data remaining in the flash memory and switching the rover to an operating mode that does not use flash memory. Also, the team is restructuring the rover's communication sessions to use a slower data rate, which may add resilience in case of a reset during these preparations." The team suspects some of the flash memory cells are simply wearing out. The reformat operation is scheduled for some time in September.

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01 Sep 04:00


Time to dance in front of Mary Jane! If I'm lucky, she'll turn out not to practice pre-copulatory sexual cannibalism!
31 Aug 03:11


01 Sep 04:00

September 01, 2014

Just a reminder, the Pluto shirt is available a little while longer.
02 Sep 00:00

All the Money

by xkcd

All the Money

People sometimes say "If I had all the money in the world ..." in order to discuss what they would do if they had no financial constraints. I'm curious, though, what would happen if one person had all of the world's money?

Daniel Pino

So you've somehow found a way to gather all the world's money. We won't worry about how you did it—let's just assume you invented some kind of money-summoning magic spell.

Physical currency—coins and bills—represents just a small percentage of the world's wealth. In theory, you could edit all the property records on Earth to say that you own all the land and edit all the banking records to say you own all the money. But everyone else would disagree with those records, and they would edit them back or ignore them. Money is an idea, and you can't make the entire world respect your idea.

Getting all the world's cash, on the other hand, is much more straightforward. There's a certain amount of cash in the world—it's about $4 trillion—and you want it all.

It won't necessarily do anything for you, since—without the cooperation of the outside world—you probably won't be able to spend it. But maybe you can swim around in it, like Scrooge McDuck in his giant room full of gold.

So you cast your magic spell and summon all the money.

The pile of cash is the size of the Empire State Building, but heavier. You probably don't want to be standing under it, so let's assume you're standing over here, off to the side:

The vast majority of the weight in the pile is coins, and the biggest single contributor is the US penny. Despite periodic efforts to kill off the penny, the US Mint keeps producing more of them.

There are probably 150 billion pennies[1]A 1996 GAO report mentioned a US Mint estimate of the number of pennies in circulation: 132 billion. If you're excited by phrases like "General Accounting Office", "auditing standards", and "Subcommittee on Domestic and International Monetary Policy", you can read the report here.

If you're so excited about penny statistics that the GAO report isn't enough for you, you're in luck: There's another way to derive this number.

We can get an idea of the number of pennies in circulation by looking at all the change in our pockets, counting the dates, and using that to estimate a loss rate. In 1999, some statisticians recorded the dates on 1,000 pennies they had lying around, and published the data in the book Workshop Statistics: Discovery with Data and Fathom, page 389. By plotting the frequency with which they saw pennies of various ages against the frequency we'd expect from US Mint production numbers, we can estimate the rate at which older pennies drop out of circulation per year. Using their numbers, I come up with an estimate of about 190,000,000,000 pennies in circulation.

We can then apply the same formula to previous dates, and come up with a number for 1996, to check against the GAO number. (I have a lot of spare time on my hands.) Surprisingly, this produces an estimate that's still about 190,000,000,000. Either number (190 billion or 132 million) is probably a reasonable estimate, but if you're serious about your penny statistics—and if you've read this far, you must be—you should probably go with the US Mint guess. After all, they presumably know a thing or two about counting pennies. currently in circulation, for a total weight of over 300,000 tons. In total, US coins and bills are responsible for about 30% of the pile's weight, while the European Union—which has barely been minting coins for a decade—contributes 15%.

Unfortunately for you, the pile doesn't stay a pile for long,[2]When you pour lots of loose material in a heap, it tends to form a cone. Different materials will form cones with different slopes; the steepness of the slope for a given material is called its angle of repose.

I've never found the exact angle of repose for coins—or had enough of them to test it—but a forum poster with the username Master of Coin (who claims to be well-acquainted with "how piles of coins 'slish' about") says that it's probably no more than 5 or 10 degrees. and what seems like a safe distance isn't so safe.

In 1919, a tank of molasses in Boston collapsed. Molasses is thick, so you might think it would flow out slowly, but it didn't. The wave of molasses swept down the streets too fast to outrun, demolishing buildings and killing 21 people.

Something similar happens with the pile of coins. As it collapses, the pile spreads outward, a wave of money carrying a staggering amount of momentum. The pennies, quarters, loonies, and euros scour the landscape in an expanding ring. Within seconds, the wave of coins engulfs you and you die.

There are ways to avoid this. You could, say, build a wall around the coins to contain them. Unfortunately, then you might face a problem worse than death:

Building code violations.

Heavy skyscrapers need ground strong enough to support them. Places with large skyscrapers, like those in Manhattan, need bedrock sturdy enough to hold them up.[3]For a long time, people said that this was why there was a gap in Manhattan's skyline—the bedrock wasn't strong enough to support skyscrapers in the middle. However, a 2011 paper in the Journal of Economic History says that this is a myth, and the bedrock had little influence on the location of skyscrapers. A search through this giant PDF of NYC building codes suggests that if we went ahead with this plan, we would be in serious danger of violating section 1804 ("ALLOWABLE BEARING PRESSURES").

Which makes me wonder: Did Scrooge McDuck ever had to worry about this stuff?

31 Aug 16:57

[bluechaircomics/via webtoons]

01 Sep 08:54

Selling Your Soul

01 Sep 08:11

Цитата #429854

Прочитала про переходник для мясорубки и вспомнила, как искала в начале 90-х папе запчасть к трактору. Обзванивала магазины запчастей и говорила: "здравствуйте, мне нужна деталь на трактор, которая выглядит как плоская квадратная железка примерно десять на десять сантиметров с маленькими дырочками для болтиков по углам и большой дыркой, обделанной резинкой, посередине". Приблизительно на пятом звонке вместо "ЭЭЭ, а вы не знаете номер по каталогу?", услышала: "Да, Это фланец ведущей каретки трактора ДТ - 75, стоит 320 рублей, в наличии отсутствует,но вы можете взять каретку в сборе за полтора миллиона". Видимо, у мужичка был черный пояс по разгадыванию кроссвордов...
01 Sep 07:12

Цитата #429851

Мне всегда в именах всадников апокалипсиса слышалось что-то родное из детства.
Сегодня понял что, это же классическое советское госучереждение, ГладМорСмертьСтрах.
31 Aug 18:00

sofapizza: your sheep looks concerned


your sheep looks concerned

30 Aug 20:40

The steaks have never been higher. [via]

The steaks have never been higher. [via]

30 Aug 19:01

Someone advertises their hackathon on the public mailing list

01 Sep 16:00

Pun Dog #14 (previously)

Pun Dog #14 (previously)

01 Sep 06:35

Pole dancing is an art form

31 Aug 15:52


30 Aug 23:49

Dealing pot in public

30 Aug 20:00

История дня по итогам голосования за 31 августа 2014

Выгуливал собаку, проходим мимо пары с коляской, и пёс решил гавкнуть, может, испугался большой коляски. Женщина сразу начала орать:
- Сука! Заткни свою собаку, у меня ребёнок спит!
Муж ей отвечает:
- Не ори, ты орёшь громче, чем собака!
- Он всё равно ребёнка разбудил!
- Он спит.
Мамаша заглядывает в коляску и кричит:
- Идиот! Ты ребёнка дома забыл!
И быстро убегает в сторону дома.
Стоя на тротуаре, мы смотрели, как она бежит к парадной.
Стояли я, мой пёс и мужик... со спящим ребёнком на руках.
30 Aug 18:00

How to exit the back of a pickup truck. [via]

How to exit the back of a pickup truck. [via]

02 Sep 04:40


by abbyinamerica

01 Sep 22:44

singingsh0wtunes: subway sure doesn’t mess around when it comes...


subway sure doesn’t mess around when it comes to puns

01 Sep 17:10


by Reza


01 Sep 14:41

Efficient and Uniform Planar-Type Perovskite Solar Cells by Simple Sequential Vacuum Deposition

by Chang-Wen Chen, Hao-Wei Kang, Sheng-Yi Hsiao, Po-Fan Yang, Kai-Ming Chiang, Hao-Wu Lin
Thumbnail image of graphical abstract

A novel sequential layer-by-layer sub-100 °C vacuum-sublimation method to fabricate planar-type organometal halide perovskite solar cells is developed. Very uniform and highly crystalline perovskite thin films with 100% surface coverage are produced. The cells attain maximum and average efficiencies up to 15.4% and 14%, respectively. This low- temperature, all-vacuum process is suitable for a wide variety of rigid and flexible applications.

01 Sep 14:28

Structure Tuning of Crown Ether Grafted Conjugated Polymers as the Electron Transport Layer in Bulk-Heterojunction Polymer Solar Cells for High Performance

by Yi-Lun Li, Yu-Shan Cheng, Po-Nan Yeh, Sih-Hao Liao, Show-An Chen

A series of novel electron transport (ET) polymers composed of different conjugated main chains (fluorene, thiophene, and 2,7-carbazole) and crown ether side chain (crown ether, aza-crown ether and amine) is presented for bulk-heterojunction polymer solar cells with poly(3-hexylthiophene) (P3HT) or poly[[4,8-bis[(2-ethylhexyl)oxy]benzo [1,2-b:4,5-b′] dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl]](PTB7) as the active polymer and aluminum metal as the cathode. Unexpectedly, it is found that the main chain of ET polymers has a greater effect on the interfacial dipole than the side chain, even when attaching a high polarity group. The electron-rich bridge atom of the main chain may also contribute appreciably to the interfacial dipole. When used as the ET layer, all of these polymers can generate an optical interference effect for redistribution of the optical electric field as an optical spacer and, therefore, allow more light to be absorbed by the active layer, thus leading to an increase in short-circuit current density. They can also block hole diffusion to the cathode and prevent electron–hole recombination during the ET process. Among the five ET polymers investigated, PCCn6 is the most effective one, providing a remarkable improvement in the power conversion efficiency (measured in air) of the device to 8.13% compared to 5.20% for PTB7:[6,6]-phenyl-C71-butyric acid methyl ester (PC71BM).

Thumbnail image of graphical abstract

Alcohol-soluble conjugated polymers are designed for use as the electron transport layer in polymer solar cells to improve the power conversion efficiency. The use of a suitable conjugated main chain increases the open-circuit voltage via the interfacial dipole and enhances the short-circuit current density of active the layer by rearranging the optical electric field within the device. Additionally, a deeper highest occupied molecular orbital level, compared to the light-absorbing active polymer, serves to block holes and supress leakage current.