Daylight saving beyond the fading curtains

The issue of daylight saving is back on the agenda in Queensland. That happens periodically and no doubt will keep re-occurring until daylight saving is eventually introduced.

Born and bred in the UK I was totally used to “summer time” as it was called. I liked it and if I lived in England (or Tasmania) now would still enjoy it - and vote for it if a plebiscite were to be held on the issue. However Far North Queensland is neither England nor Tasmania in any way that is relevant to daylight saving.

First, in temperate areas there is a wide variation in the number of daylight hours. In winter it is not at all uncommon for the sun to struggle up at 8am and set again at 4pm: only eight hours of sunlight. In summer the same area would expect to have 16 hours of daylight, the sun rising at 4am and setting at 8pm.

Under those circumstances there is an obvious opportunity to “save” daylight and hence reduce the need for artificial light usage. Move the clocks so that the sun rises at 5am clock time and sets at 9pm. Such a move is simply an efficient use of a natural resource - light.

Second, in a cool temperate climate the sun is always welcome. It both brightens the place up and injects some much needed warmth. It is a welcome friend.

In the deep tropics the sun is not a friend except in the very short winter period. For the vast majority of the year the sun is so powerful it makes doing anything outdoors unpleasant after about 7.30am. The whole place gets “cooked” - house, roads, the ground and so on. There is little cooling until the sun sets, until then you wait for that time when relief comes. And that occurs when the sun decides, not the clock. Being bombarded by a celestial heater at the rate of approximately a kilowatt per square meter is not just unpleasant it also presents a significant risk of dehydration. Above all else the sun is terribly enervating.

The various publicity campaigns, such as “slip, slap, slop”, try to emphasise that exposure to high doses of sunlight is dangerous. It is not a fluke that Queensland is the skin cancer capital of the world. The “Sunsmart School Project”, a very sensible idea, is a clear recognition that the sun is not an unalloyed blessing, but is potentially dangerous.

The time at any place on earth is determined by its longitude. For convenience and to prevent total chaos, humans have determined that any given area of land is to be “run” by the time at an agreed place. In Australia, Eastern Standard Time is essentially the “time” at longitude 150 degrees east. Sydney lies near that line so EST is correct “sunwise” for Sydney. Melbourne, because it is about 5 degrees to the west of Sydney, operates on a year-round “daylight saving” of 20 minutes - even without official daylight saving. Adelaide, about 11 degrees west is 45 minutes “behind” Sydney which is of course why that state does not operate on EST.

The first thing to recognise about Queensland is that the coast does not run south-north. From a time point of view that means that even just along the coast we have Brisbane in the southeast corner which is actually east of Sydney by about 3 degrees and is hence running at 12 minutes of daylight “losing” time - if I may make up a phrase. However, when you move up to Cairns the longitude is about 146 degrees west and is running on a permanent 17 minutes daylight “saving”. Note that there is about half an hour difference between sun noon time in Brisbane and Cairns.

The second point to recognise about Queensland is that is has a considerable variation from the east coast to the west of the state. From a sun time point of view that means that Mount Isa is well to the west of Sydney or Melbourne and is in fact on almost the same line as Adelaide. So, inevitably it follows that Mount Isa residents operate on a permanent daylight saving of about three quarters of an hour. Furthermore the sun time difference between Brisbane and Mount Isa is roughly a full hour.

Queenslanders were supposed to be opposed to daylight saving because it would cause the curtains to fade. Sadly, I have never heard anybody actually say that, but never mind, it is a nice story that hurt nobody. Now although I know that the curtain fading idea - if it ever existed - is wrong, I know, as a scientific fact, that there really is something called The Equation of Time.

Due to the dual facts that the Earths orbit is not circular but elliptical, and the obliquity of the ecliptic, there is variation between clock time and sun dial time over each year. That variation is, in total, the result of the interaction of two sine curves due to the two facts mentioned above.

As is well known, the longest days are around December 20 each year. What is less recognised is the fact that, due to the effects of The Equation of Time, the earliest sunrise is towards the end of November and the latest sunset is in late January. The magnitude of the effect is greater in the Southern hemisphere than in the Northern hemisphere and is greater towards the Equator. In Far North Queensland the sun noon, i.e. when the sun is at its zenith is at a clock time of just gone 12pm in late November, but is about 12.30pm in late January.

The effects of the combination of longitudinal and latitudinal variation, compounded by variations in the effect of the Equation of Time are relevant to the issue of the introduction of daylight saving.

If, or when daylight saving is introduced here we shall have the fantastic situation that sun will rise in Cairns on December 20 at almost the same (clock) time as it will be on the June 20. Even a southerner (defined here as anyone south of Rockhampton!), should be able to see that to have sunrise in mid summer at the same clock time as sunrise in mid winter is peculiar - to put it mildly.

There are frequent grumbles from business people that it is very difficult to do business between Queensland and the southern states because of the lack of daylight saving in Queensland. That is truly pathetic. How do they think businesses in the United States survive - and they have to deal with five time zones on the mainland: Atlantic, Eastern, Central, Mountain and Pacific? People and businesses there seem to survive. One has to presume that people here are either inflexible or plain dumb or, the most probable, just exercising their good old Aussie right to cry “we’ll all be rooned”.

Contrary to fashionable thinking the issue of whether to introduce daylight saving is not simple. The effects vary from one area to another as a consequence of basic geographic facts. To deny that and to think there is some nice simple answer would be akin to King Canute proverbially trying to command the sea.

Sooner or later I expect that daylight saving will be introduced in this state. Well, I won’t be “rooned”, but I will think it silly that I will get up to make our early morning tea and listen to the radio by 6am onwards in mid summer in the dark. That will be caused by a human decision to impose “daylight saving”.

Never mind, put the lights on.

Daylight saving?

John Ridd is a retired secondary schoolteacher. For many years he was a member of the Moderation Committee of the Qld Board of Senior Secondary School Studies. John is co-author (with Santo Russo) of a series of Maths textbooks for Years 8/9/10.

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