Author Archives: Mr Reid

Whiteboards

Posted on 4th February by Mr Reid

Some­times after a lesson I take a pho­to­graph of the white­board left over. Some recent pho­to­graphs are below.

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The cost of coins

Posted on 23rd January by Mr Reid

It used to be the case that coins used as currency had value because of the material from which they were made: a solid gold coin weighing one ounce had the same value as one ounce of gold. The intro­duc­tion of … Continue reading →

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Technetium-99m generators

Posted on 15th January by Mr Reid

Technetium-99m is a radio­active tracer that is used in twenty million medical dia­gnostic pro­ced­ures per year. At least 31 radio­phar­ma­ceut­icals based on Tc-99m are used for imaging and studying organs such as the brain, heart muscle, thyroid, lungs, liver, gall­bladder … Continue reading →

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Plug wiring colour scheme

Posted on 6th January by Mr Reid

UK plugs use brown insu­la­tion for the live wire, blue insu­la­tion for the neutral wire and green with yellow stripes insu­la­tion for the earth wire. But why this par­tic­ular com­bin­a­tion of colours? The answer is decept­ively simple: there is no type … Continue reading →

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Night vision

Posted on 2nd January by Mr Reid

The vision of human beings is well-adapted to daylight; the human eye has evolved to see in the range of wavelengths that are brightest in the spectrum of light that the Sun emits. The intensity of the light the Sun emits … Continue reading →

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The most radioactive parts of the UK

Posted on 28th December by Mr Reid

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

Posted on 27th December by Mr Reid

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

Posted on 21st December by Mr Reid

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

Posted on 20th December by Mr Reid

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

Posted on 17th December by Mr Reid

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

Posted on 14th December by Mr Reid

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

Posted on 12th December by Mr Reid

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

Posted on 6th December by Mr Reid

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

Posted on 1st December by Mr Reid

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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The speed of jet lag

Posted on 28th November by Mr Reid

Jet lag (ICD-10: G47.2) occurs when the body’s internal clock (its cir­ca­dian rhythm) gets out of sync with the time of day. Example: London to Los Angeles Leaving London at 1200 you will arrive in Los Angeles ten hours later and your … Continue reading →

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Types of Desert

Posted on 24th November by Mr Reid

A desert is defined as an area that receives a very small amount of pre­cip­it­a­tion: these areas come in three main forms. The most recog­nis­able type of desert is the sub­trop­ical desert, typified by the Saharan and Arabian deserts. They are … Continue reading →

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UK electricity import and export

Posted on 20th November by Mr Reid

The UK doesn’t have enough elec­tri­city. The amount of elec­tri­city that the UK produces (from various sources) is not enough to meet demand, and the UK relies heavily* on imports from France and the Neth­er­lands in order to meet its … Continue reading →

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The Moses Bridge

Posted on 14th November by Mr Reid

The Moses Bridge, designed by Ro & Ad Archi­tects in the Neth­er­lands is my new favourite water crossing (taking over from the Mag­de­burg Water Bridge). The bridge allows visitors to cross the West Bra­bantse Water­line to reach Fort de Roovere. … Continue reading →

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Why does metal feel cold?

Posted on 8th November by Mr Reid

One adjective commonly used to describe metals, along with the adject­ives like “shiny” and “silvery”, is “cold”. But this doesn’t makes any sense when you take the Zeroth Law of Ther­mo­dy­namics into account. Over a long enough period, everything in the … Continue reading →

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Star traveller etymology

Posted on 2nd November by Mr Reid

The term astro­naut comes from the two Greek words: ástron (star) and nautes (trav­eller), making an astro­naut a “star trav­eller”. In Russia astro­nauts have always been known as cos­mo­nauts, an angli­cised version of the Russian word kos­monavt (ori­gin­ally from the … Continue reading →

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