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Studies show that the more you test your knowledge, the more you learn. This is known as the Testing Effect. Whenever you take a Quiz for free, GoConqr captures your score and tracks it so you can measure your progress over time.

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Check out our new quizzes:

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 I work for the Galactic Public Archives YouTube series. If you haven’t already seen it, I suggest taking a look at our newest video: Losing Your Mind? Great Thinkers On the Brain It's a great piece on what the leading philosophers of our time thought about the history of the brain and the great brain debate.

I hope that these compelling visions of the future from the perspectives of scientists and innovators are as exciting to you as they are for me.

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Learn • Explore • Interact

We're introducing our newest infographic that describes the variety of student resources found at The Physics Classroom. The infographic is intended for placement upon a classroom wall to help teachers introduce the website to their students and to help students find the website. Feel free to share on your social networks and to distribute it in any manner you wish. Help us get the word out.


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The architecture of water

Water is fascinating, for many reasons.   It takes more energy to heat than most substances.  It's one of the few substances that expands when it freezes.  It forms complicated patterns in its liquid state, which are just beginning to be understood.  There are at least 18 kinds of ice, which exist at different temperatures and pressures.  Snowflakes are endlessly subtle.  

And ice can form cages that trap other molecules!  Here you see the 3 main kinds.

They're called clathrate hydrates.  There's a lot under the sea beds near the north and south pole - they contain huge amounts of methane.   At some moments in the Earth's history they may have erupted explosively, causing rapid global warming.  

But let's focus on the fun part: the geometry!  Each of the 3 types of clathrate hydrates is an architectural masterpiece.

Type I consists of water molecules arranged in two types of cages: small and large.  The small cage, shown in green, is dodecahedron.  It's not a regular dodecahedron, but it still has 12 pentagonal sides.  The large cage, shown in red, has 12 pentagons and 2 hexagons.   The two kinds of cage fit together into a repeating pattern where each unit cell - each block in the pattern - has 46 water molecules.

Puzzle 1: This pattern is called the Weaire-Phelan structure.  Why is it famous, and what does it have to do with the 2008 Olympics?

You can see little balls in the cages.  These stand for molecules that can get trapped in the cages.   They're politely called guests.   The type I clathrate often holds carbon dioxide or methane as a guest.

Type II is again made of two types of cages – small and large.  The small cage is again a dodecahedron.  The large cage, shown in blue, has 12 pentagons and 6 hexagons.  These fit together to form a unit cell with 136 water molecules.

The type II clathrate tends to hold oxygen or nitrogen as a guest.

Type H is the rarest and most complicated kind of clathrate hydrate.  It's built from three types of cages: small, medium and huge.  The small cage is again a dodecahedron, shown in green.  The medium cage - shown in yellow - has 3 squares, 6 pentagons and 3 hexagons as faces.  The huge cage - shown in orange - has 12 pentagons and 8 hexagons.  The cages fit together to form a unit cell with 34 water molecules.

The type H clathrate is only possible when there are two different guest gas molecules - one small and one very large, like butane - to make it stable.   People think there are lots of type H clathrates in the Gulf of Mexico, where there are lots of heavy hydrocarbons in the sea bottom.

Puzzle 2: how many cages of each kind are there in the type I clathrate hydrate?

Puzzle 3: how many cages of each kind are there in the type II?

Puzzle 4: how many cages of each kind are there in the type H?

These last puzzles are easier than they sound.  But here's one that's a bit different:

Puzzle 5: the medium cage in the type H clathrate - shown in yellow - has 3 squares, 6 pentagons and 3 hexagons as faces.   Which of these numbers are adjustable?  For example: could we have a convex polyhedron with a different number of squares, but the same number of pentagons and hexagons?

The picture is from here:

• Timothy A. Strobel, Keith C. Hester, Carolyn A. Koh, Amadeu K. Sum, E. Dendy Sloan Jr., Properties of the clathrates of hydrogen and developments in their applicability for hydrogen storage, Chemical Physics Letters 478 (27 August 2009), 97–109.

#geometry #water

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Scientists make world’s thinnest transistor - at three atoms thick - ScienceAlert

'... The transistor is made using two-dimensional semiconductors known as transition-metal dichalcogenides (TMDs). When reduced to a single layer, these TMDs are just three atoms thick, made from members of a family of elements called transition metals. One of these, molybdenum disulfide, is a type of silvery, black metal that's been touted for its superior electrical qualities over the past few years.

The team crystallised it down, and figured out how to peel ultra-thin sheets just a few atoms thick from the surface of the crystals. Amazingly, even at this thickness, the molybdenum disulfide film retained its electrical properties, which makes it a promising candidate for use in future electronics. "The electrical performance of our materials was comparable to that of reported results from single crystals of molybdenum disulfide, but instead of a tiny crystal, here we have a 4-inch (10-cm) wafer," one of the team, Jiwoong Park, said in a press release.

Chemists cook up three atom-thick electronic sheets | Cornell Chronicle

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The Types of Intelligence

In 1983 Howard Gardener described 9 types of intelligence:

1: Logical-mathematical
2: Linguistic
3: Bodily kinesthetic
4: Musical
5: Naturalist
6: Interpersonal
7: Intra-personal
8: Spacial
9: Existential

What other scientists thought were just soft-skills, such as interpersonal skills, Gardener realized were types of intelligence. It makes sense. Just as being a math whiz gives you the ability to understand the world, so does being “people smart” give you the same ability, just from a different perspective. Not knowing math you may not calculate the rate at which the universe is expanding, but you are likely to have the skills to find the right person who will.

Even 20 years after Gardener’s book came out, there is still a debate whether talents other than math and language are indeed types of intelligence or just skills. What do you think?

#psychology #productivity #infographic #intelligence #talent #mind


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How to Make a Human 

Here is a handy visual of what’s inside the human body. Of what makes us, well, us. While it may seem rather simple to measure all the various parts of a human, it’s really quite complicated. This is primarily because there are a number of ways that you can measure what makes a human a human.

Essentially, you need to go with either mass or atomic composition ie., what has the most weight or how many atoms there are.

Case in point, we know that people are, on average, 50% water. More specifically, it’s about 57% water. Now then, water is made up of 2 hydrogen atoms and 1 oxygen atom. This means that there is actually more hydrogen in the body than oxygen. As an aside, if you are wondering, the average adult human has some  7 x 1027 atoms that make up their body.

That’s 7,000,000,000,000,000,000,000,000,000 atoms

However, hydrogen is the lighter element. As a result, when looking at mass, you will find that there is more oxygen than hydrogen. And interestingly, nearly 99% of the human body is made up of just six elements: These are hydrogen, carbon, oxygen, nitrogen, calcium, and phosphorus. 

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An Amazing visualization of a mechanical wave.
Animated Photo

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