Crash Course Astronomy


For those astronomy buffs! A friendly and approachable view of the universe from the amazing Crash Course team.

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History of the Atomic Bomb & The Manhattan Project

As many know, the atomic bomb has been used only twice in warfare. The first was at Hiroshima. A uranium bomb nicknamed “Little Boy” (despite weighing in at over four and a half tons) was dropped on Hiroshima August 6, 1945. The Aioi Bridge, one of 81 bridges connecting the seven-branched delta of the Ota River, was the target; ground zero was set at 1,980 feet. At 0815 hours, the bomb was dropped from the Enola Gay. It missed by only 800 feet. At 0816 hours, in an instant, 66,000 people were killed and 69,000 injured by a 10-kiloton atomic explosion.

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Misconceptions: Electrical Circuits 2

My second post in the electrical misconceptions series relates to the use of terms in this topic.

The topic of electricity contains several abstract terms; voltage, current, resistance, energy, power etc. and students have understandings of some of these terms (current and resistance) from other areas of their lives. The other terms are more abstract because students often do not have a clear understanding, or framework or visual representation of what they mean. Of course, the terms that they have some kind of context for (current and resistance) may actually be leading to a further misconception because the meaning may vary in alternative contexts.

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Disney has created an algorithm that can turn almost anything into a spinning top


The spinning top is one of the oldest and seemingly simplest toys devised in human history, but that doesn’t mean we can’t improve it. Disney Research has come up with a new algorithm that allows it to design a stable spinning toy out of almost any shape. Researchers found that shapes that fail to maintain a balanced spin as a solid object could be analyzed before construction to optimize its center of mass for rotational stability — that is to say, the algorithm tweaked 3D meshes to create hollow, interior spaces that keep it balanced. Using this method, the team was able to 3D print tops in the shapes of teapots, asymmetrical ellipsoids and breakdancing armadillo without fear of them toppling over.

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Misconceptions: Electrical Circuits 1

Students often have difficulty with electrical circuit problems. In my experience, most of these difficulties are due to misconceptions.

Here is one of the most commonly held misconception;

Electricity exits the battery at the positive side, travels around the circuit and ends up at the negative side.

There are a few other related misconceptions that come out of this statement;

  • The moving charge, called electricity, travels at the speed of light
  • The wires are like empty pipes that the electricity travels through
  • Multiple bulbs in series are of ever decreasing brightness, with the bulb nearest the positive terminal of the battery the brightest, followed by the bulb next to it and so on.
  • Resistors need to be on the positive side in order to do their job of limiting the electricity (or current) after it.

I’m sure there are more, but these are all linked to a single misconception; that the battery supplies the current, or charge, or electricity, to the circuit.

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The Cloud Chamber – detecting radioactive particles at home

Have you ever notice the vapour trail left behind after airplanes jet through the air?

These trails, called contrails, are caused by aircraft travelling through the cold air at high altitudes. The trails are caused either by condensation of water vapor from the engine exhaust as it is ejected into the cold air, or by condensation of water vapor already in the air around pressure changes due to vortices formed as air passes over the aircraft’s wing.


Well in 1932 Carl David Anderson announced his discovery of the positron, a positively charged electron. A discovery that was made using a cloud chamber, a relatively simple device, that can produce contrails when particles pass through the vapour sealed within the cloud chamber container. Continue reading