• Question: why do we change the time on our clocks coming into winter and into summer?

    Asked by killa to Colin, John, Kevin, Shikha, Triona on 7 Nov 2014. This question was also asked by 652bera39.
    • Photo: Shikha Sharma

      Shikha Sharma answered on 7 Nov 2014:

      Hi Killa,
      I have recently looked into the history of Daylight saving time (DST) as I am new to Ireland so thought of reading about it when it happened on 26th Oct 2014. DST is a change in the standard time with the purpose of making better use of daylight and conserving energy by setting your clock forward one hour during the summer months, and back again in the fall.

      History behind Daylight saving time (DST):
      It was first proposed in 1895 by English-born insect specialist George Vernon Hudson. Hudson used to do shift work and during his leisure time he collected insects, so valued the dear moments of his daylight after-hours. So, in order to save his day hours he proposed a two-hour daylight saving shift and presented it in a paper to the Wellington Philosophical Society. However, it was not given any importance at that time. Then, a British businessman William Willett also believed we should have more daylight hours after work so he also proposed similar concept. In 1907, William published a pamphlet “The Waste of Daylight. In 1909, the first daylight saving bill was drafted and presented to parliament and examined by a committee. But the idea was opposed by many farmers and it was never made a law. In 1916, during the First World War Germany became the first country to implement DST, in order to save fuel for the war effort. Thereafter, other countries followed it.

    • Photo: Kevin Motherway

      Kevin Motherway answered on 8 Nov 2014:

      The axis that the earth rotates on is tilted by about 23.5 degrees from the vertical . If you’ve ever looked at a globe you notice it spins on a spindle tilted like this \ and not like this |. So when the earth travels around the Sun, each hemisphere experiences longer days in their Summer and shorter days in their Winter. Not only that but the Earth is slowly slowing down as the friction from the atmosphere, the tides in the sea cause friction on this ball spinning in the vacuum of space. There is actually a daily tide about 100 km beneath the earths crust where the ground beneath your feet literally bulges by about a metre each day, not at the surface but In the upper mantle. Every release of energy like this slows the planet down: it’s estimated that the days (the time from sunrise to sunset) got about 2 millionths of a seconds longer due to the Japanese Magnitude 9 earthquake in March 2011! All this stuff adds up to us human beings trying to synchronise our watches and clocks with what the planet is actually doing. It takes 365.25 days for the earth to go around the sun so we cope with that by adding an extra day to a year every 4 years (leap years). We’ve had to have a couple of leap seconds since the start of the 20th century to re-synchronise our crude clocks with our slowing down planet as well. So basically we need to manage our lives around what the planet is actually doing. We have shorter days in winter, so we have a choice; do we have dark mornings or dark evenings. The consensus is that it’s better to have daylight when people are walking and driving to school and work still half asleep so that the daylight says to your body “WAKE UUUUUUUUP”. Apparently there are stats that show road traffic accidents rates are lower in countries that use Daylight Savings Time to have brighter mornings, but as with any human behaviour it’s very difficult to put something as complex as how many traffic accidents we have down to just how bright it is at 8 on a Monday morning.

      Going back to your namesake: Einstein would have argued there is no such thing as Time. There is a thing called Space-Time and whenever you have a bending of Space-Time you have gravity. So time moves slower close to dense objects. A twin living next to a mountain (where the earth is more dense at that point) will be ever so slightly older than the twin who lives on a flat area. The astronauts on the international Space Station who are slightly further away from the earth than we are, age slower than us who are closer to the dense earth. Inside a black hole, it so incredibly dense and there is so much gravity that time would go so slow it essentially stops!

      So next time somebody gives out you’ve arrived late, just launch into a tirade about there being no such thing as Time: it’s space-time and you choose not to sully your scientific understanding of the cosmos by crudely approximating your life around this “time” thing.