Keeping track of time

    Helen Czerski Helen Czerski | 18:00 PM, Friday, 28 October 2011

    Distance travelled ~ 773'769'600 km

    Noon is personal. It's the time of day when the sun is highest in the sky and your shadow is shortest. It's the reference point for a clock that is always with you, because you can be your own sundial. The spinning Earth provides us with a built-in natural chronometer. Brilliant!

    That clock has served nature well for millennia - birds sing at dawn, foxes come out at dusk, humans go to sleep when it gets dark, and we all live day to day. One daily cycle follows another. But the growth of human civilizations and the need for greater co-operation than ever before meant that humans had to control time instead of being controlled by it. Clocks were standardized. The day was split up into hours, and humans had to agree to start work, meet or provide services at specific times. It was the only way of co-ordinating a civilization. But the Sun was still the reference point.

    Faster travel, and inventions like the radio and telephones, meant that time zones had to be invented. Local noon where I am, in Southampton, happens four minutes later than local noon in London, so society agreed that all of the UK would be in a single time zone, for convenience. 12 o'clock in Southampton now happens at the same time as 12 o'clock in London. The Sun is no longer the reference point. The shortest shadows still happen around lunchtime, but you can't set your watch by that any more. And as clocks got more and more accurate, we discovered that the shape of Earth's orbit means that the length of a day varies by about a minute over the course of each year. Solar time seemed to be almost unhelpful in our standardized world.

    So humans weren't living and working according to the Sun any more, but sunlight hadn't gone away.

    The standardization of time meant that some people were sleeping when it was light and working when it was dark. And so Daylight Savings Time was invented, to try and compensate for the limitations imposed by standard time. The clocks go back in the UK Sunday 30 October 02:00am in a return to GMT, after a summer of allowing us an extra hour of daylight in the evenings (upcoming DST times). Of course, we don't actually get an extra hour of daylight - we just move our time reference to take that hour off the start of the day and tack it on the end. We couldn't have built the modern world without standardized time, and now we're trying to patch up some of its inconveniences.

    daylight saving maps

    Image courtesy of C.G.P Grey. For more on daylight saving watch his video.

    Should we bother? Every clock change causes sleep deprivation, a demonstrated drop in productivity and a day where the whole country risks turning up at the wrong time. It's a nice ritual to mark the changing of the seasons, but is it worth it?

    I think that the crux of the argument might be in how society is changing. Fifty years ago, a giant siren marked the time when work began and ended in factories. The development of our society relied on us all working together, at the same time. It was an enormous example of human co-operation. But now, we live less constrained lives. We work flexibly, and internationally. The standardization of the working day is disappearing - some businesses start work at 8am, some at 10am. I adapt my daily routine so that I can go running when it's light, whether that's in the morning or the evening.

    As long as I get my work done, maybe it doesn't matter when I do it. So I can choose for myself what I do with my daylight hours, irrespective of the official time that they start and end.

    Do we even need time zones any more? Maybe the logical end to this argument is that we could have just one Earth time, so that everyone has lunch at a different official time, but it's still when the sun is more or less overhead. I'm not necessarily advocating for that, but it's not as close to science fiction as you might think. Scientists in every country frequently record data using "Universal Time" or Zulu time, which is GMT. That way there's no confusion at all over when it was recorded, wherever you were on the planet.

    So, is the era of British Summer Time/Daylight saving time over? What do you think?

    The half way point: a look back over 468'000'000 km of our planet's annual journey

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    Stephen Marsh Stephen Marsh | 14:45 PM, Friday, 1 July 2011

    Distance travelled ~ 468'249'600 km: day 182 in Earth's orbit

    We've come a long way since filming the wintery and snowy mountains of Aonach Mor in Scotland on January 3rd 2011.

    We are at the halfway point of our 940 million kilometre [584 million mile] annual circumnavigation of the Sun, hurtling through space at 107,200 kilometres [66,700 miles] an hour. On this odyssey we are discovering how gigantic forces like the tilt of the Earth and its spin determine our climate and influence the life cycle of every living thing on the planet. We will discover how our relationship with the sun creates the seasons, powers the most spectacular weather on the planet, and even dictates how we live our lives.

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    So far we have been ice road trucking in Yellowknife, the coldest place in North America, where winter temperatures routinely plunge below minus 35 degrees. We've witnessed the Sun lighting up the serpent on the side of the Temple of Kukulkan , at Chichen Itza in the Yucatan Peninsula of Mexico and the dramatic break of the ice on the waterfall on the Hay River. We have driven into the heart of a snowstorm in Upper New York State and witnessed the awesome destructive power of a Tornado on the Great Plains on Nebraska. We travelled on dog sleds to the very edge of the sea ice in Greenland and sailed deep into the southern ocean off Tierra Del Fuego on the vey southern most tip of South America.

    But we're only half round our orbit. Now the northern hemisphere is tilting towards the Sun and it's mid summer. And all that warmth is about to trigger some incredible weather phenomena. Asia is about to experience its annual monsoon and Hurricane season has begun in the Atlantic - so the US can expect some of these monster storms to hit it's eastern seaboard. And the 23 Degree team will be there - witnessing the incredible power of nature unleashed and discovering how our cosmic dance with the Sun drives these stunning weather phenomena.

    So stick with us for the second half of our journey - it's going to be a bumpy ride.

    Can we use the Moon to tell time?

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    Helen Czerski Helen Czerski | 15:01 PM, Friday, 4 March 2011

    d ~ 162'086'400 km: day 63

    Earth's relationship with the Sun is of huge significance to the 23 Degrees team. Its 23.5 degree tilt is what makes our planet's annual journey around the Sun interesting and it's why we're encouraging everyone to help us record that journey. But maybe it's time we also looked up at the moon. Our planet's relationship with the Moon also plays a part in the Earth's cycle and the passing of time - the moon goes around the Earth and the Earth goes around the Sun which goes around the galaxy. It almost sounds like the solar system runs like clockwork right? But maybe it should be the other way around. Clocks run like the solar system. Our Sun dominates our concept of time but the moon is 400 times closer to us than the Sun is, and it moves around our planet steadily like the hand of a clock. Could we use the moon to tell the time if we wanted to?

    Earthrise Apollo 8 Lunar mission 1968

    It's tricky because the moon orbits Earth at a fixed rate but that rate has nothing to do with how fast the Earth spins or how fast the Earth goes around the sun. Inconveniently the numbers don't divide cleanly. However, during any single day the position of the moon doesn't change very much so it's quite a good reference point. Once the sun has set you're on the side of the Earth facing away from the sun slowly spinning back towards sunlight. If you know where you are on that journey you know the time. Here are some ways that the moon can help.

    The ocean bulges out towards the moon attracted by its gravity. As the Earth spins we pass through the bulge and out the other side. We call that bulge a tide. If you're by the beach on a cloudy night you can get an idea of the time just by watching the tide level. In most places high tide is six hours after low tide, and you can use this even if you can't see the moon directly.

    The moon's gravity doesn't only affect the water. It's also tugging on us, and if the moon is overhead pulling us upwards, it balances out a little bit of Earth's gravity pulling us downwards. If you stood on some very sensitive scales at a full moon, you'd notice that you weighed about a quarter of a gram less at midnight than you did at midday. So you could tell the time by monitoring how your weight changed during the night. It's not a very useful clock - you'd have to weigh anything you ate or drank and not put any extra clothes on. But in theory you could use your weight as a clock, because it changes systematically as you rotate closer to and further away from the moon. You have your own tide.

    At full moon a normal sundial can be used as a moon dial. The moon is more or less exactly where the sun would be in the sky during daytime, except that the times on the sundial will be 12 hours too early. And of course, if you can see the moon, you can watch its progress across the sky and estimate the time in the same way that you would with the sun.

    But why expend all this effort to help the moon tell solar time? The moon has its own time, and there's a tide-powered clock in London to tell you what that is.
    The Aluna clock is at Trinity Buoy Wharf in London - a prototype for a larger one to be built next year. I love this idea because the progress of the sun going across the sky is only one way of keeping track of time. Everything in the universe with an orbit is like the hand of a different clock all measuring the same time in different units. The moon is just one clock of many!

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