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Balancing bicycles, looking back on Trinity, pricing up Pluto and more


By Tushna Commissariat

Mechanics was never my favourite topic when I was studying physics for my BSc, but I think I might have been more interested if we had looked at real-world situations rather than square blocks sliding down an incline plane. A bicycle that carries on, sans rider, without toppling over for quite a long time, for example, would have got my attention. This is a rather well-known quirk of mechanics though and it isn’t even the first time we have discussed it on the blog. Indeed, Physics World‘s James Dacey, a keen cyclist, delved into the topic in 2011. This week, we spotted a a new Minute Physics video on the subject, over at ZapperZ’s Physics and Physicists blog. Watch the video to get a good, if a tiny bit rushed, explanation of the three forces that come into play to allow a bicycle at a certain speed to zip along without its human companion. As the video suggests, all is not known about the secrets of free-wheeling bicycles just yet though, and I have a feeling that we will blog about it again in the years to come.

Yesterday marked precisely 70 years since humanity entered the nuclear era, with the Trinity nuclear bomb test that set ablaze the New Mexico skies at the crack of dawn. Over at the New Yorker, author and nuclear historian Alex Wellerstein has written a poignant piece about the fateful day. “The light of a nuclear explosion is unlike anything else on Earth,” he says in his opening sentence, and goes on to explain in detail what went into making Trinity possible. What was most interesting to me was how seemingly lax the various safety measures were, not to mention just how wrong the scientists were in their estimation of the explosion’s yield – it was four times larger than the predicted maximum, with a detonation force equal to about 20,000 tonnes of TNT.

Undoubtedly, the most exciting news of the week was New Horizon’s long awaited and hugely successful Pluto fly-by. While we have already covered that on the blog and on the website, here are two other interesting little Pluto-related stories we noticed. First, an amusing article on CBC News looked into the supposed love-hate relationship between the dwarf planet and esteemed scientist Neil deGrasse Tyson – a vocal critic of Pluto’s once-held planetary status. On a slightly more sobering note, take a look at Scienceogram UK‘s excellent infographic on the relative costs of the space mission versus the money spent by the US in Iraq in just one month.

And for some more weekend reading, go over to the Guardian to read about why the astronauts on board the ISS had to hide in their Soyuz capsule for over an hour and take a look at writer Matthew Francis’ blog post about why 2014 really was the hottest year on record. Finally, physicist and author Chad Orzel explains how physics could help you build a secret tunnel, using only a gyroscope and an accelerometer.

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One comment to Balancing bicycles, looking back on Trinity, pricing up Pluto and more

  1. M. Asghar

    Fermi estimated yield of the Trinity nuclear explosion rather well, by letting fall against gravity small pieces of paper and measuring their deflection against the shock wave from the explosion.


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