It's a Matter of Time

Time (t)

t=s/v

Distance (s) Speed (v) acceleration (a)

s=vt v=s/t a=v/t

A Grand Prix motorcycle circles the track. After level pegging for most of the race, its average lap time is compared with the other competitors and found to be 0.2 seconds quicker than the next fastest. With a top speed recorded on the longest straight of 100 metres per second (m/s) - that's over 200mph - it's right up there with the best, but it's still not primo top-speed. But the bike is winning – so, it must be going quicker through the bends. If it carries on like this, by the time the race finishes in five laps time, the motorcycle will have won by a margin of one second. It covers the final lap in 50 seconds, winning with an average speed of 50m/s (during this lap). This means that the track is 2500 metres in length. As the machine in second place is 0.2 seconds slower over this distance, its average speed, therefore, is 49.98m/s. Prediction, calculation and evaluation; all possible because of time.

Time: the only proper constant in the world we understand. While everything we can see and touch can vary, time is the truly independent ingredient. Time gives the fixed marker posts of change; a uniform grid over which all that happens in life is laid. Unlike anything else in our everyday perception of the world, it never varies. Everything you can physically see changes at differing rates, because of time, and are only quantifiable because time is unvarying and constant. Time is both the base and the dimension that provides the measure of life. Without time there would be no comparison of events – change would be unquantifiable and unpredictable. Our deterministic world could not function without the concept of time.

Time is sometimes referred to as the fourth dimension because to find meaning in the words, faster, slower, quicker, a perceptible but intangible benchmark is required, one that exists outside the world we see. Imagine you have no recognition of time. A truck overtakes you on the motorway, he's in front of you, so he will arrive before you. How do you arrive first? Your truck must get in front of his, but how do you get the front of your truck ahead? The simple answer is to increase speed. But time doesn't exist, so neither does speed.

When speed increases or decreases, it simply means the distance travelled changes in a fixed period of time. When we accelerate or decelerate, the distance travelled in a fixed period of time changes in a fixed period of time. Using the standard (SI) units of time and space, metres and seconds, a truck travelling at a speed of 13m/s, travels 13 metres every second. If it accelerates at a rate of 2 metres per second, per second (m/s/s), its speed will increase by 2 metres per second every second. So, if a truck travelling at 13 m/s accelerates at a rate of 2 m/s/s, after 1 second it will be travelling at 15 m/s, after 2 seconds, its speed will have increased to 17 m/s.

Time permits change in the physical world; speed, acceleration and interest on savings are all changes in things we can touch. Time makes change relative. When you next overtake another truck on the motorway, think about it. A 16.5 metre artic attempts to pass another. The distance needed from the front of the overtaking vehicle passing the rear of the other, to its rear passing the front of the other, is 33 metres. This is an absolute minimum and takes no account of the extra distance required to turn back to the lane in front of the overtaken truck. You are averaging 56mph, he's averaging 55mph. The difference is about 0.5m/s. The time needed is 66 seconds, just over a minute. In that time you will have travelled over 1650 metres, a little more than a mile.

So, by overtaking, you gain just over 30 metres for every mile travelled, and it takes about a minute. At 56mph, a 200 mile journey will take 3 hours 34 minutes. Or, 3 hours and 38 minutes had you sat behind the other lorry. Four minutes: a motorcycle on an A road would cover 4 miles – at 60mph; a mile a minute. Roger Bannister could change position by a mile. A Grand Prix motorcycle, travelling at over 200mph would have overtaken your truck in just under a second. (As the comparison is between your truck and the motorcycle, the relative change in distance is 16.5 metres, plus 2 metres for the length of the bike.) And, at 200mph, the race bike would arrive at the end of the 200 mile journey no less than two and a half hours before your truck (had you both started in the same place and, of course, at the same time). That's enough time for a serious athlete to run a marathon. It's all a matter of time.