what is time? why is it unidirectional?why is it linear?

Question

If it is just another dimension, how?-no complicated maths please.

Answer 1

Time is quantified motion. That is, it is the way we measure motion. That's why it is unidirectional. Although it can be treated as such matematically, it is not a physical dimension.

Answer 2

We live in a physical universe. We try to understand the metaphysical, and the supernatural.

One of the tools we use to understand our universe - our physical universe - is logic. If something is not logical, it is hard for us to understand.

From logic we have derived many useful tools such as science, and mathematics. Sometimes we use a logical tool in order to solve a problem that without the logical tool seems impossible, but with the tool can be solved. The tool acts like a catalyst which helps us solve the equation without being part of the answer because it cancels itself out.

The idea of time is such a tool. It is very useful to help us understand our physical universe. But is time a force or material thing? No. It is a tool to help us understand change, to measure speed, to understand life and death. Can we capture a piece of time, and put it in a box? No. Can we measure how things change, using the tool of time? Yes.

So to be a useful tool it has to have consistent qualities or it would not be logical and of no use as a tool. So, we give it linearity and devise ways to measure change down to the billionth of a second.

Oh. Second? Yes, just a tool to help us understand minutes hours, days and years. We can make a machine that will change in exactly the time we have defined as a second: a clock. Did a second exist before we named it and defined how much change it measured? No. Who decided that 60 seconds was a minute and 60 minutes was an hour, and 24 hours in a day? The ancient Egyptians. What if they had decide that there should be 10 seconds in a minute and 10 minutes in an hour and 10 hours in a day? or some such idea? Our words and ideas about time would be different than they are now. That is, our tools would be different. But we would still measure 'time' with them. That's the long answer.

;-D Take time to enjoy life! That's the short answer.

Answer 3

Great question! By coincidence, I'm now reading Brian Greene's "The Fabric of the Cosmos", where he devotes a very substantial part of the book addressing these questions.

Briefly, he says (from relativity) that there is a time dimension (a fourth dimension), but it can't be separated from the space dimensions (hence, spacetime). Time is not absolute, so time appears different to different observers who are moving relative to each other.

The "arrow of time" is one of Greene's hot buttons. Much of physics (Newton's Laws, Einstein's Relativity) is indifferent to the "direction" of time; they work equally well in both directions.

What gives time a definite direction is the law of increasing entropy, and that in turn depends on conditions in the very young universe. That says that overall, the amount of in the universe is constantly increasing. An egg rolls off the table, falls to the floor, breaks, and splatters. It doesn't occur the other way around (a splattered egg comes together, rises intact to the top of the table, etc.)

For this law of increasing entropy to hold, the early universe had to be characterized by extremely entropy, that is, it had to be incredibly uniform in composition in all directions. And, aided by "inflationary cosmology", it was.

Greene says it didn't have to be this way, but it was, aided by something called a "Higgs plateau". But that's too technical. Nevertheless, that's the reason, according to Greene, why time is unidirectional.

Answer 4

Time is like a hair on your head. Each day (a measure of time) it grows a little longer and is divided into a series (organization of time) of events that you can divided as finely as you wish. The hair grows by cell division. Cell division can be broken down into a necessary series of events. Even the chemical reactions involved in the various steps of cell division take finite time; but you could dertermine when each step is half done or 3% done, etc. Time is unidirectional because we do not observe (on Earth?) a hair shrinking and the chemical reactions and steps of cell division being reversed. Time certainly is not linear. If you are on a space ship approaching the speed of light or entering a black hole time will perform very strange tricks. For a photon speeding through space, time is frozen. Luckily on earth we move so very slowly that we almost never have to reset our watches due to speed (unless we enter another time zone) and we absolutely never have to reset our watches because of distortions caused by mass, space and velocity. What we have is constant here. Even Newton's laws of motion work perfectly well. Great question.

Answer 5

Why time is linear can be best explained by the Laws of Thermodynamics when related to the fact that the Universe is expanding. (Not to suggest that if it were contracting time would run backwards...no!).

Watch out for other non-scientific definitions of time, like psychological perceptions of time, or the idea of "cyclical time" represented in the Mayan calender (The Maya believed that time, and literally, events, repeated themselves through cycles called "suns"). Physical time is different. It's been demonstrated that physical time can slow as one nears the speed of light, or for similar reasons near black holes (where light cones become distorted).

Hope this helps!

Answer 6

I believe time is a consequence of the existence of mass, and it is a paradox.
It isn't necessarily linear, although that is how we witness it from our perspectives. And, I don't believe it is unidirectional either, except from our perspective.
The best way I can describe my understanding of time is to look at light, which moves at C in a vacuum. From relativity theory and the Lorentz transformation equations, it is so far understood that light travels an infinite distance in zero time from its own perspective. That means, wherever light goes, it is already there, it is not moving. But, light bends in a gravitational field, thus it must have mass. No two particles of mass can occupy the same space at the same time, so, light does the only thing it can do and that is exist "next to" itself in time. When we see a beam of light, we are looking at one "packet" of light exisiting at multiple times, like looking at the multiple frames that make up a moving picture (film). We never actually witness anything that is happening in the present, it is always past, because it takes "time" for light to go from an object to your eye and then the signal to be processed and "seen". By the time we see it, it is a different time than when we look at it. So, everything we are witnessing is essentially memory. You have probably heard about stars being so far away it takes billions of years to reach us. The star may have died a billion years ago, yet we still see it today. It doesn't really exist, yet we see it. Here is something for you to consider. In reality, there is no such thing as space for light. It is always in the same space. And, if the light in that space has mass, how can we exist in that space at the same time as the light? In truth, we don't. We exist in the same space at a different time. This has implications as to why we view energy as quantized. In Einstein's famous E=MC^2 equation, he is saying that energy and mass are the same thing but different in magnitude. However the 'C' in the formula must be used to make them equal. It is the same thing as looking at two identical rocks. One is 2 times bigger than the other. So rock=rock is not true until I say rock=2rock. C is a number in this equation, it happens to be the same number that is the speed of light, but why that is nobody has yet explained. It is the number that workd, the number of times the energy rock (E) is bigger than the mass rock (M). This says mass IS the same thing as energy, only energy is C squared times bigger. Why C squared? Why C? Why does the speed of light work in this equation? What is the relationship to actual light? That is an unanswered question in physics today. I have a theory, and it is one I think most would find very difficult to accept, but I think all mass in this universe is actually the same single particle of light (it may be that there are 2 of them), and is/are appearing to us as physical bodies, whether "living" or inert. All of our bodies, the earth, the planets, stars and galaxies are made up of the same particle(s) of light, since the light has an eternity to be these things and we can never pinpoint the state of its existence until it is already past. Time is the phenomenon that makes the light appear as separate bodies. One last thing, what are the very first words God spoke according to the Christian Bible? Wish I could give you a better answer, but some illustrations have to be shared in mathematical terms..

Answer 7

According to Albert Einstein Time is relative. Unfortunately, I do not know more than that, since I am not studying physics. However, it is a very good and perhaps one of the most difficult question I have ever read.
By the way, I can send you the entire book by Einstein, if you want me to. Just send an email to and you will get it.

Answer 8

Thats a deep question! look up the 2nd law of thermodynamics for some idea of why time is unidirectional (entropy).

Answer 9

48

Answer 10

Time isn't unidirectional. Our senses just percieve it that way, probably because the chemical processes that keep us running are unidirectional.