Monthly Archives: December 2011

The most radioactive parts of the UK

The average radio­active back­ground dose in the UK is 2.7 mil­lis­iev­erts. Of this 2.7 mSv, 1.35 mSv comes from radio­active radon gas leaking out of the ground. This radio­active radon (Rn-222) is produced by the decay of uranium-238, after a series of inter­me­diate … Continue reading

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Biosphere lungs

Some people refer to the rain­forests as “Earth’s lungs”. In reality this is quite far from the truth, as rain­forests actually con­tribute little (net) oxygen to Earth’s atmo­sphere; 70% of oxygen pro­duc­tion is done by water-bourne green algae and the … Continue reading

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Anscombe’s quartet

Anscombe’s quartet is four sets of data that are used to demon­strate the import­ance of graphing data. Set 1 Set 2 Set 3 Set 4 x y x y x y x y 10 8.04 10 9.14 10 7.46 8 … Continue reading

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Haversine formula

The hav­er­sine formula is used to cal­cu­late the distance between two points on the Earth’s surface spe­cified in lon­gitude and latitude. d is the distance between two points with lon­gitude and latitude (ψ,φ) and r is the radius of the Earth. As … Continue reading

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Patterns in birthdays

If births were evenly dis­trib­uted throughout the year (i.e. a 1 in 365 chance of being born on any given day) then the graph of number of births against birth month would look like the one below: You’re least likely to be … Continue reading

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Curiosity’s nuclear battery

The Curi­osity rover that is the main part of the Mars Science Labor­atory mission is very dif­ferent from its pre­de­cessors Sojourner and the twin rovers Spirit & Oppor­tunity. L-R: Spirit/Oppor­tunity, Sojourner and Curi­osity. L-R: The wheels of Sojourner, Spirit/Oppor­tunity and … Continue reading

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You’ve already experienced the earliest Easter you’ll ever know

You may have noticed that the date of Easter Sunday changes every year: The date of Easter Sunday is cal­cu­lated using a calendar that is based both on the Sun and the Moon* and takes place “on the first Sunday after the … Continue reading

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Logarithmic scales

Some of the quant­ities measured in physics cover a very large range of values and this can make dis­playing meas­ure­ments of their value dif­fi­cult or con­fusing. pH, tra­di­tion­ally thought of as a meas­ure­ment of acidity, but actually a meas­ure­ment of the … Continue reading

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The Milky Way is shaped like a CD

The Earth orbits just one of the 200  –  400 billion stars that make up the Milky Way. This star, the Sun, orbits at a distance of about 27000 light years from the Galactic Centre, trav­el­ling at 220 km/s (one mile every seven thou­sandths … Continue reading

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