Time is among the most mysterious of fundamental quantities. Time was originally defined and quantified through astronomy, and today astronomers are used to glibly talking of vast stretches of time. But even after Einstein showed time to be an elastic, changing thing we still have to resolve all its mysteries. Martina Redpath looks at the enigma of Time.

image of Tarantula nebula

Looking back in time: At the exact centre of this image of the Tarantula Nebula in the Large Magellanic Cloud lies the brilliant but isolated star VFTS 682. This extraordinary star is three million times brighter than the Sun. We see it as it shone 170 000 thousand years in our past. (Image credit: ESO/M.-R. Cioni/VISTA Magellanic Cloud survey. Acknowledgment: Cambridge Astronomical Survey Unit)

Time is a fundamental part of life. We have mealtimes, home time and bed time sometimes we have a great time other times maybe we need a time-out. Time management, working full-time, not wasting time having family time are all part of daily life but just what is time in the grand scheme of the Universe?

In the days before clocks and watches, man was in tune with the Sun, Moon and stars and was able to deduce how much time had passed accordingly. Sunrise and sunset marked the beginning and end of day, the length of time between one full Moon and the next marked a lunar month, the change in seasons could be seen witnessed depending on which constellations were visible. With the development of the sundial and eventually clocks, we are able to measure time passing with a little bit more precision.

On Earth there are 24 different time zones. Often travelling on holidays you can change your watch to the time at your destination by winding your watch forward or backwards. Sometimes when travelling further afield the affects of jet lag can be felt. Travelling from (West-East) is more likely to cause jet lag rather than travelling (North-South). Fatigue, feeling disorientated and struggles to sleep at night are common consequences associated with the jet-set life. However within a few days, our bodies can adjust accordingly without any lasting disruption.

If travelling to the other side of the world causes jet lag, what about travelling beyond our planet. The effects of travelling into space cause astronauts to experience a whole new time cycle. A day on Earth is how long it takes for the planet to turn once on its axis. On the International Space Station astronauts experience sunrise and sunset every 45 mins. It only takes 90 minutes for the ISS to orbit the Earth once. Hence ultimately they have day and night every three quarters of hour. This would have a significant impact on one’s biological clock which over generations has adapted to the Earth and its day/night cycle and a 24 hour day. In order to counteract the possible effects of such a drastic change of time, astronauts keep routine just like they would on Earth. They have around 8 hours sleep; wearing eye-masks and ear plugs to aid sleep in a bright space. Maintaining routine helps adjust to this unusual living space and readjusting back on Earth.

When astronauts travel they use Earth time, i.e. one day/ 24 hours, to help them whilst living in the Space Station. In the future if humans were to travel a little further in to the realms of our Solar System how would time be different? Would we maintain Earth Time or adjust to local planetary time? A day on Mars is only 39mins longer than here on Earth maybe it could useful when travelling on Mars to adopt Martian time and maybe have an extra 39mins to have a lie-in, or bond with the locals? Either or it may be useful.

Image of Albert Einstein

Time Lord: Albert Einstein during a lecture in Vienna in 1921 (Image credit: Photograph by Ferdinand Schmutzer)

A day is defined as the length of time it takes for a celestial body to make one rotation around its axis. When thinking of time in space rather than on a planet, this causes our traditional measurement of time as we know it (an hour or a day) to become obsolete. Albert Einstein (1879-1955) had pondered this when he considered space time. Einstein said time is relative rather than absolute like suggested by Isaac Newton. This make sense, notice how time flies when you’re having fun yet waiting for a bus in the rain seems to last for ages. Einstein said that if someone could travel on a fast spacecraft they could travel somewhere in a few hours or days, whereas for someone remaining here on Earth, months could have passed for them, therefore time is based on a person’s relative movement with respect to another.

Light is the fastest thing that we know, this is demonstrated often during a thunder storm where we see a flash of lightning before we hear the crash of thunder. Light travels of speeds of 300,000 kilometres per second (186,000 miles per second). Einstein suggested that if one could travel at the speed of light, time would no longer exist and you would exist in a realm of timelessness. If there actually was a way to travel beyond the speed of light would this mean you could go back in time, potentially altering past and leading to a paradox. Perhaps this is something best left in the hands of the Doctor? Our Universe is a vast place and to travel beyond our Solar System using any kind of foreseeable technology could take thousands of Earth years so the ability to travel at light speed would be extremely useful when exploring the Cosmos.

Jumping back to reality, there is a possibility of real life time-travel on Earth. Disclaimer: apologies now to those imagining dining with the dinosaurs or perhaps witnessing the first man land on the Moon, I can’t deliver that! However as I mentioned earlier on Earth there are 24 different time zones. So in the South Pacific if you were to visit the isle of Tonga, then take the 1hour 7min flight to the isle of Samoa, you would arrive 1hr 7mins after you took off but only it would be yesterday! This will be the case until the end of this year when Samoa time will change jumping forward 24 hours to allow the country to trade more easily with countries like Australia and New Zealand .

Image of Pacific Ocean

The Pacific Ocean seen from the ISS on 13 June 2003. The Republic of Kiribati islands are in the foreground. The International Date line curves around Kiribati as to not divide the country into separate days. This is due to happen with Samoa at the end of this year. (Image Credit : NASA)

The International Date Line spans the globe from the North Pole to the South Pole. It isn’t a straight line but bends around different countries to ensure that they have the same time. This imaginary line marks where one day changes into the next. Kiribati used to be separated by this line meaning the same country had a time difference of 24 hours but in 1995 they changed this and now the whole group of islands is on the same day. Crossing this line is as close as we can currently get to time travel.

Physicists have been pondering time and space time for years and still have not come to any definitive conclusion. How time exists outside of planet Earth remains a mystery. Time is relative… I think perhaps I’ve just discovered a new excuse the next time I’m late.

Image of_Martina Redpath

Martina Redpath, ESO (Image credit: Armagh Planetarium)

(Article by Martina Redpath)


1 Comment

Vulcan: ghost planet | Astronotes · October 15, 2013 at 03:47

[…] (1879-1955) published his ground-breaking General Theory of Relativity. This postulated that space and time were linked and that the mass of very large objects could bend both. Einstein was not overthrowing Newtonian […]

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