You have heard that time is the fourth or fifth dimension I am sure. I don't believe that time is a dimension. Then it is explained that the level of dimensions proceed as such. You have a point in space with no width or depth. That's one dimension. You have two of these and you have a line. A line is two dimensional or so you would think. Actually you don't. Even with multiple points you still only have one dimension as long as no points lie outside that line. Even at just two points the problem becomes as much metaphysical as it does mathematical. Do you really have a line or just two points in space. You really wouldn't even get that far in this discussion since if these two points or even a single point existed "in space" then you already have dimensionality because of the space that contains them. What if you have a thousand points all lined up? Do the number of dimensions jump? Intuitively you say no.
Most people would agree that a plane, such as a sheet of paper with no thickness would be two dimensional. To form this geometric construct you would need a minimum of three points and one must not be in line with the other two. So when you think about it any two points of any triangle are lines but you need all three points to define a plane.
If you build on this idea in a minimalist fashion and ask yourself how many points you need for three dimensions you realize you need four but this is only a geometric construct it doesn't actually represent reality. For this "space" to contain points then it must already have dimensional characteristics so the points do not define the "first" dimensional construct the space that they occupy must first. That is unless your construct is the only thing that exists. Furthermore couldn't two planes exist with each having its own set of points without the two being connected and therefore not achieving dimension? If so then would the two separate planes need to occupy the same plane and would just be segments of a larger plane?
As you can see by the time you reach any discussion about a fourth and fifth dimension and the property of time you aren't talking about anything you know with any degree of certainty. To call time a dimension wouldn't even make sense in this context. If time existed in a universe with two geometric dimensions like a sheet of paper would time add a third dimension? And which dimension comes first?
In this thought experiment lets say that time is not a dimension thus saving ourselves the trouble of trying to define its rank in the universe. The very idea of "dimensions" is a human construct and therefore not necessarily a true representation of "nature's reality" as opposed to those things that are "human realities"
So what is time as we know it?
We experience time as the property of the universe that does not allow for everything to happen all at once which would destroy the universe? We only experience anything that we experience due to the property of the passage of time. I have to admit I am having trouble forming a sentence to describe time without using the word time. As I said it's one of those things you know when you see it but I don't think we have the language to explain it we can only quantify it.
Measuring Time
<===synchronous
digital===>
<==== cesium atomic
strontium atomic===>
The first clock above (synchronous) works on the fact that the power grid has a certain frequency. AC current in America is kept as close to 60 hertz, or 60 back and forth cycles, as possible for this reason originally. This is averaged out over the course of a day. This method of time keeping is more a counting of the oscillation of the power supply than it is a time keeping device.
The second clock (digital) works on the same principle. Again a counter of pulses or oscillations is used.
Atomic clocks are similar in that they are merely counters. In the case of Cesium the oscillation is the radiation emitted from an electron jumping from one energy level to another very rapidly. How this is achieved is simple if you are a physicist but the rest of us will just take their word for it.
The second is defined as 9,192,631,770cycles of this radiation. Note that radiation does not always mean something deadly.
Radiators in your home "radiate" heat. Again we are counting something and defining what that means. A more
detailed account is found in the following link. This probably seems odd that this is the number used and it matches a second
except the second was already a pretty defined length of time. This is "backward engineering" in that the second existed
and they found a number that suited their needs. If they had chose 9,192,631,771 the difference would only show up after
9,192,631,770 seconds which is over 12 years and then you would only be off by a second. An Atomic Second anyway.
http://www.popsci.com/science/article/2010-11/where-international-standard-units-come-part-two-second
In general terms the length of a second is 60 x 60 x 24 parts of a day or 86,400 seconds in a day. This is what matches our clocks. This is a day divided into 24 hours and hours into 60 minutes and minutes into 60 seconds. This is somewhat "natural" as is the first clocks used. Water clocks and then pendulum clocks were "natural clocks". But even then the length of the pendulum used had to be determined to make a number of swings that matched the possibly arbitrary division of the day into 86,400 seconds.
There are a few books on the measurement of time. I would suggest Deep Time by Gregory Benford and In Search Of Time by Dan Falk. And many others I have read that I don't recall right now.
Given the volume of books on the subject I could not possibly go into all the aspects of time but my hope is to actually get you interested in looking for yourself. For instance why do you need a clock as accurate as over 9 billion parts per second as demonstrated in the Cesium Atomic Clock. What could you possibly need with that kind of accuracy?
One answer is GPS. We owe a lot of our modern transportation, especially on the ocean, to the use of GPS. Global Positioning System. We also owe our ability to wage war with precision guided weapons to this system. But we also use it to measure the height of volcanoes to see if they are growing and combined with lasers could measure the movement of fault lines. For this to be possible the signals from the satellites to a receiver on the ground and between the satellites have to know exactly what time it is and not just any old time. The signal between two satellites or the time between signal from and to the ground needs to be measured very accurately. Radio signals travel at the speed of light just like well just like light does. To measure something with the accuracy of say 30 feet is a pretty remarkable feat. A foot is roughly 1 / 11,784,960,000 the distance an electromagnetic signal travels in a second. Thus 30 feet is a calculation roughly of 1 in 392 millionths. In atomic clocks time that is about 23 or so super super small ticks of the atomic clock. It is easy to see that over greater distances even an atomic clock would eventually lead to large inaccuracies. And we haven't even factored in the speed of the satellites at nearly 9,000 miles per hour not to mention the effect of time dilation on moving objects etc.
On a more general level we have an idea what the greatest amount of time is. We already know or believe the universe to have existed for nearly 14 billion earth years which is odd when you think about it since the earth has only been around about a third of that. Which leads me to the point that the measurement of time is a totally human endeavor. However it would not be surprising to find out that if an alien race were to ever visit humankind that they too invented Cesium Atomic Clocks and Quartz Clocks both of which use natural phenomenon to achieve accurate oscillations to count. But their definition of what a standard unit of time like the second would be different and probably based upon the orbit and rotation of their home planet at first. As I mentioned in a previous blog when you use nature as your units of measure a species not "from here" would, if they had science, encounter the same universal properties that we do and thus science and math would be our common language. What their language and imagery means would be more difficult to decipher but math is math and a pendulum is a pendulum no matter where you are.
So what is the smallest amount of time? A much harder question to answer. Max Planck sought to answer that with the idea of Planck Time. For a decent article on this subject check out the following link.
http://www.universetoday.com/79418/planck-time/ basically Max Planck did what I would do, if I may be so bold, is to reduce time, velocity, size, etc into a system based on the observed universe where the fasted thing we know is the speed of light and the smallest thing we know is in the smallest sub sub atomic particles. A Planck length is the point at which two points are distinguishable. Below this measurement any two points, if they existed independently of each other, would be indistinguishable. This of course cannot be proven at present. The distance is on the order of 1 x 10 to the minus 20 which is very very small. And it may turn out that you can't have two points indistinguishable from each other and still have two points until you bring in string theory or some such thing. Something I don't pretend to understand or necessarily believe.
The use of atomic clocks in a way divorces us from nature. The number of cycles 9 billion or so is only the way it is because it closely matches the second we have become accustomed to a second that goes all the way back to the earliest civilizations who divided time by 12s and 60s for whatever reason we can only guess. Is it because circles divide easily into 60s? Would this even matter in a time when there were no clock faces? Probably not. So why those numbers? It's a mystery lost to time. Why did people with 10 fingers decide to stop counting at 60 discrete numbers and then use multiples of that number? 70 becomes 1 x 60 + 10 not just plain old 70.
Here is a quick quiz of course only you will know if you get it right. What are the first 10 numbers? Did you say 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 ? Look closely. How did you get 10? You just stuck a zero after a 1. But where did you get a zero? The actual first numbers or digits are the same as above except you start with 0 and end with the 9. As you count higher and higher you just move numbers around. 10, 20, 30 or 100, 200, 300, etc. Easy enough to figure out unless you don't believe in 0. You don't have 0 fingers. Hopefully. So it is kind of understandable that some people may not believe or understand 0. But still why 60?
The actual day, expressed in seconds, is 23 hours 56 minutes and 4 seconds. This is how long it takes for the earth to rotate once but based on what? In this case for the sun to reach its highest point on two successive days but this is somewhat arbitrary and changes depending on the season as much as 146 seconds from least to greatest. There is also the sidereal day or the time for the earth to rotate enough to have a distant star in the same place two days in a row. Or two nights anyway. While you are thinking about that think about this. At the same time the earth is rotating it is also moving around the sun slightly less than 1 degree per "day" but which "day". Once the concept of days became known to some degree of accuracy and "fixed" as a standard it became apparent over time that things didn't quite appear where they should appear in the daytime or nighttime sky. This is why we have a leap day every 4 years, but not in 3 successive years that fall on a century, and one extra every 4th century. Example 1700, 1800, and 1900 were not leap years but 2000 was. Also 2100, 2200, and 2300 will not be but 2400 will. These account for the "decimals" in the numbers. A "year" turns out to be 365.242 rotations of our planet or "days" and therefore in four years you get an extra day on the calendar but over four centuries this turns out to add 3 days too many so you keep them out at three century years but include it on the fourth century year.
If you really want to cook your brain follow this link. http://www.universetoday.com/14700/how-long-is-a-day-on-earth/
There are obviously lots of things to consider when we consider time or at least the marking of time. Over the thousands of years that man has been marking time it was the use of astrology and then astronomy and ultimately physics that lead us to the understanding that time is slippery in that when you seek to measure it at some point you are going to be wrong and at some point you realize that time is relative to the observer. Even at the smallest level Planck Time is not the smallest unit of time but the smallest measurement.
The whole point of this blog entry is to get the reader interested in the history of telling time. How man arrived at his measurement of time from sundials, to water clocks, to the pendulum, to synchronous, to quartz, and ultimately to atomic clocks is story of deep and clever thinkers. Just think about this. Currently there is a camera in existence that can actually take an image of a light beam as it strikes an object so quickly that you can tell where the light ends and begins and this method could produce some scientific discoveries we can't imagine yet. Machines and the use of time has enabled mankind to peer into worlds we could not possibly see on our own because we simply are not capable. Already the "slowing" of time by using cameras has enabled us to image the wings of insects in flight and create our own mechanical insects that fly as well as toy birds. Before the invention of digital movie making, it took only 16 frames per second of still photographs, taken in succession, to trick you into realizing the illusion known as the motion picture. Only 16 per second. Lots of things can happen in a 1/16th of second especially inside an atomic clock.
And now I am out of time. I will leave you with one of the most profound quotes that I have ever heard in my life and they come from a Star Trek movie no less. In the movie Generations Malcolm McDowell is talking to Captain Picard and he says "time is the fire in which we burn" and later "time is the ultimate predator". And when you think about it both of those things are true. Time eventually wins. After the last star burns out in trillions and trillions of years and the blackholes evaporate and perhaps the universe expands into a substance so thin as to not even have gravity anymore time will still exist. Time will be the very very last fundamental force/law of nature to exist long after the rest are gone.
And we didn't even get into the fact that our orbit around the sun isn't a circle or even an ellipse. Not really. Here is another link to upset what you thought you knew about reality. http://aa.usno.navy.mil/faq/docs/seasons_orbit.php
Goodbye
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