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 Apr 24 comment Milk or sugar first to maximize temperature of a hot cup of tea? The order of tea and milk does make a noticeable difference and led to developments in the design of experiments and the Fisher's Exact Test: en.wikipedia.org/wiki/Lady_tasting_tea Mar 23 awarded Yearling Mar 14 comment Why is second the duration of exactly 9192631770 periods of radiations? Measuring a mean solar day is not that easy: there are only four times a year when an actual solar day is exactly 24 hours long and even those are usually not midnight to midnight, or midday to midday, or dawn to dawn, or dusk to dusk. So it takes time to measure a mean solar day, during which its length may actually change. Dec 14 comment Why is there a temperature gradient on Earth? The relatively small differences in distances to the Sun is not substantial compared with other effects: the Earth's orbit takes it closest to the Sun at the beginning of January, but in most of the northern hemisphere temperatures are usually much higher in July when the Sun is further away. Jun 24 comment Water pressure on a floodlight in a swimming pool Rule of thumb: roughly an additional $10$kPa (about $0.1$ atmospheres) per metre of water depth, based on $g$ times the density of water. Don't forget the air above the swimming pool (about $100$kPa or $1$ atmosphere). The issue is going to be making the floodlight waterproof more than pressure at $45-70$cm. Apr 16 comment Can we theoretically balance a perfectly symmetrical pencil on its one-atom tip? There is a mathematical continuity argument which suggests that there may be a starting position at which the pencil will remain balanced for any pre-specified amount of time (in effect, consider the starting positions which lead to the pencil falling over in particular directions). This probably does not survive a quantised viewpoint. Mar 23 awarded Yearling Feb 24 comment Will the upcoming solar eclipse stress the European electrical grid? The rate of change is more dramatic in time than the effect of clouds (you can see France's solar generation in blue lines in the second column of gridwatch.templar.co.uk/france ) but since the effect is predictable, there will be dispatchable sources used to fill the gap (probably a combination of hydro, pumped storage, gas and coal). In terms of balancing supply and demand it will probably be no less dramatic than each day's sunset leading to a boost in demand. Sep 30 awarded Explainer May 12 comment How long does it take an iceberg to melt in the ocean? In 2008 a rather smaller (27 km^2 but still 1 to 2 Petagrams) ice island calved off the same glacier and was tracked for a year, including a frozen winter, as it travelled almost 20 degrees south to Frobisher Bay. Mar 23 awarded Yearling Nov 29 revised Archimedes' principle for two liquid layers see comment on denominator Nov 29 comment Archimedes' principle for two liquid layers You are probably correct about the denominator - I will edit Nov 28 answered Archimedes' principle for two liquid layers Nov 28 comment Archimedes' principle for two liquid layers Messy may be the correct word for overflows, but it depends on the liquids you have to clean up. Nov 28 answered How many years would it take the Pioneer space probe to travel to Proxima Centauri with its current speed? Nov 26 awarded Enlightened Nov 26 awarded Nice Answer Nov 23 answered Strange behaviour of water drops on a heated pan Oct 4 comment What happens when a bacteria tumble? Is it an active or a passive process? That is a biological question