Time is a complicated topic itself but it has become an everyday thing for all of us. We are constantly basing our day to day activities on “time” and even the fact that we exist on it (i.e. birthdays). But is that all time is – made up numbers and units to base our lives on? Or is there much more? And exactly what is time besides the continuous ticks of a clock?
If I was asked what time was, my reply would have been simply “time” if I am being perfectly honest. There just doesn't seem to be any other word that can describe it. Dictionary.com however gave me a very complex-sounding definition to start off with: “the system of those sequential relations that any event has to any other, as past, present, or future; indefinite and continuous duration regarded as that in which events succeed one another.” In this case, time seems to be a relative “thing” relating one event’s precession or succession to another but then it talks about a “duration” and the idea of precessions and successions itself which is strictly like repeating the word time alone in the definition and doesn't really help us to understand or generalise what it is exactly.
So I thought of researching into slightly more familiar grounds: like the time zones. The time zone system was introduced as a standardisation of time as time-keeping started off as a local custom and whenever people travelled to a new village, the slight differences in time meant that they had to change their idea of time to a very strange time when they travelled which was quite chaotic. So in 1878, Canadian Sir Sanford Fleming proposed the system of worldwide time zones that we use today. As the Earth rotated once in a 360 degrees angle (360o of longitude) every 24 hours, the time zones were based on the fact that each hour, the Earth would rotate 1/24th of its total rotation (15o) therefore each time zone varied every 15o of longitude by an hour: where the Prime Meridian was the line at Greenwich just because it was used traditionally by several countries already and was internationally accepted. This gives us the time zone system.
So here we gain a possibly vital piece of understanding: perhaps time is based on motion. On our planet, the time is regarded as early when the Sun “comes out” and late when it can’t be seen anymore. Here, the time system seems to be based on the motion of the Sun through the sky as it appears on the Earth’s surface (which is essentially the concept of sundials). This is also why the current time zone system works. The earth is continuously rotating and orbiting the Sun. The orbiting rate and the positions of the countries or the time zones on the earth are not changing in relationship to each other (ignoring plate tectonics) but the area of the earth which is exposed to the Sun is constantly changing due to its rotation in relation to the Sun so time is only progressing because there is a motion to judge it with. However this also means that time is itself dependent on a combination of forces: i.e. the forces which allow the universe and the objects within it to have relative motions.
The effect of forces on time is evident and can even be observed from the effect of different gravitational strengths on time itself. The following link (http://www.gravityfromthegroundup.org/pdf/slowtime.pdf) describes a tried experiment where the effect of gravity on time is tested. It turns out that the greater the force of gravity, the slower time progresses. This can also be explained through our knowledge of the interaction of objects through spacetime or what we can now call the higgs field perhaps. We know that the universe is expanding in all directions which is a definite motion itself. The stronger the gravitational pull of an object the more it creates a “dip” in spacetime by curving it further or suppressing and slowing the expanding motion within its gravitational field. So the increase in force causes a decrease in motion therefore slowing time more, closer to the core of the object creating the gravitational field. A similar effect is also observed when a similar experiment is done but with the independent variable as velocity. So essentially at a higher velocity, you age slower than at a lower one but only by a very, very small fraction because we can’t exactly compare the effect to travelling at the speed of light where there would be a notable difference!
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| >Different objects in space have different gravitational strengths. The Earth and Moon for example are two such objects; the Earth evidently with a stronger gravitational field thus curving space-time more |
Space-time is a word that I have been using quite frequently in this article and it is evidently important in the attempt to explain something as complicated as this. Once again referencing to the definition from dictionary.com: “Spacetime, also called space-time continuum, the four dimensional continuum, having three spatial coordinates and one temporal coordinate, in which all physical quantities may be located”. So spacetime is like a constant against which all things can be measured or located within – I would probably think of it as a lot like a common denominator in maths which you need to find in order to judge a group of fractions against each other to order them from biggest to smallest. But as we see from the definition there are three spatial coordinates (based on height, width and depth which we are familiar with in the 3D world) and a temporal coordinate: time. But without knowing this we can easily see that in order to reach such a continuum, all fundamental factors pertaining to the occurrences in/of the universe must be included: i.e. height, width and depth are evidently important in defining an object as we know it but in space other important factors particularly motion and forces (or time) are also required. Therefore time is an essential concept, as not only does it allow the existence of the word spacetime but also does it allow the existence of any object in space-time!
This is a fascinating article which explains a complex idea very well. It's amazing how time, which many of us feel is something that isn't really related to much except daily activities, is so fundamental in the workings of the universe.
ReplyDeleteThank you! I'm glad it was useful because it was certainly one very difficult topic to understand especially because it branches off into other complicated things like time dilation but I'm glad that it makes sense :)
DeleteHi, I really like that model of the earth that is in your article. Just one question, are the longitude and latitude lines labeled correctly?
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