[Winstonm]

Some ramblings by a non-scientist, non-physicist, non-mathematician, non-sense kind of guy who goes hmmm a lot.

What is the definition of time? The most common I have read is that time is a 4th dimension; however, my problem with this idea is that time according to this concept would have both a past and a future, which would mean, would it not, that the future is preordained but we won't know what that is until our time "flow" carries us through that part of the time dimension. In other words, there is a time "flow" from past to future, and everything exists in past, present, and future, but all we can see is that part that we know as the here and now.

The other problem I have is that theoretically at the speed of light time stops - if there is a point where time stops, then doesn't that mean that there is no time at that point and thus no dimension of time, either? Does this mean that at the speed of light time does not exist? If so, then it would seem that time as we understand it- or as a dimension - cannot exist. In this fashion, all that can exist is untime, i.e., velocity moving slower than the speed of light. It is the lesser speed rather than light's speed that gives time any meaning - hence, it is nothing more than a measurement - which might explain Heisenberg's Uncertainty Principle, no? At light speed, there can be no measurement of speed because time does not exist. It is the relative slowness difference between actual velocity and light speed that creates the illusion of time. At the speed of light, there can only be now; no future, no past.

Strangely, if we slow down enough even light speed disappears, doesn't it, with light itself trapped in a black hole? And with no relationship to light speed available, time in a black hole cannot exist, can it - if time is indeed nothing but a measurement of the relative slowing from light speed?

So it would seem to me that at both extremes, in a black hole with no light speed possible or outside a black hole at the speed of light there can be no dimesnsion of time in the sense of past and future - all that can occur at these extremes is now.

We now return you to your regular programming.

[kenberg]

You will need a better informed person than I to really sort it all out, but first you should rethink your view about time and the fourth dimension. To use a phrase, it doesn't take an Einstein to see that if we are to meet we not only need to specify the physical coordinates but also the time coordinate. Hence in some sense time was always understood to be a fourth dimension, even if the term was not used. The great discovery wasa that time and space interact.

Pre_Einstein: There are various ways to specify a point in three dimensional space. If we just look locally, we might use latitude, longitude, and height. Or we might run three perpendicular coordinate axes through the center of the earth. Lots of possibilities. Given the three space coordinates in one representation, we can work out the three space coordinates in another. For time, we can change units.

Einstein: The space and time coordinates interact. Changing from three space coordinates and one time coordinate to another system with three space coordinates and one time coordinate is not really a matter of one person changing the space coordinates and perhaps another person changing the time. Rather, the space and time of one system have to be transformed, all together, to the space and time of another.


Short version; It's the interaction of space and time that is the relativistic innovation. The exact nature of time was a tough enough philosophical issue before all this.


There will be people with a better grasp of this who will respond I am sure.

[helene_t]

Intuitively, time seems to be more than just the fourth dimension:

Objects are persistent. Given a time coordinate, my space coordinates are unique. This makes time special. It's not like given one of the three space coordinates in some arbitrarily chosen coordinate system, the other two coordinates + time are given. I may visit the same plane, the same line, or the same point many times.

The flaw in that argument is that it presumes that one can talk about a "point" in space as if it exists throughout time. That the question "at this point, there is a coffee pot now, what (if anything) will be at this point in one hour?". That is not correct. A coordinate system that moves is just as valid. Suppose coordinate system A and coordinate system B assign the same coordinates to the coffee pot. Suppose in coordinate system A, the coffee put has the same coordinates one hour ahead. We would say the coffee pot hadn't moved. But coordinate system B has it's origin moved by one kilometer/hour relative to A, so someone using coordinate system B would say that the coffee pot would move by one kilometer. None is more correct that the other, it's just a matter of taste.

[qwery_hi]

I suggest the book "Fabric of the cosmos". If I understand it correctly -

Time has no independent existence, space-time is the background in which all physics takes place. Speed of light attainable only for mass-less particles, and for these particles, the concept of "now" doesn't exist, or rather, past and future have no meaning if you are traveling at the speed of light, time stops.

Time typically associated with the direction in which entropy increases, however, nothing in all of our equations favors the future over the past for entropy increase. So the real mystery is why the entropy was small at the beginning of the universe.

[Echognome]

I always thought of "dimension" as a characteristic. Perhaps it's not the best way to think of it.

For example, you can imagine another dimension being density. So we can describe our object by it's XYZ position at a given point in time (discrete or continuous) and the density of the object. That's five dimensions and it's easy enough to expand from there.

[barmar]

No, a dimension is not a characteristic. Dimensions are used to locate something, and then a characteristic is what you find at that location. So you could say that the object at location XYZ and time T has the following characteristics: density D, color C, etc.

[Echognome]

barmar, on May 14 2009, 12:21 PM, said:

No, a dimension is not a characteristic.  Dimensions are used to locate something, and then a characteristic is what you find at that location.  So you could say that the object at location XYZ and time T has the following characteristics: density D, color C, etc.

And how many dimensions would that be?

My point is that we can always make our vectors have as many arguments as we want (even infinite).

Edit: Under your definition, why isn't time also a characteristic? By "location" I can either assume it's an XYZ location or a space-time location. Which is the appropriate use of "location"?

[barmar]

The point is that a dimension is something you use to find the thing whose characteristics you then observe.

If someone tells you that the building is at the northeast corner of Hollywood and Vine, you can use that to find the building, and discover that it's red. If someone tells you that the building is red, you can't use that to find the building, or discover that its address is the corner of Hollywood and Vine. When time is added to the dimensions, the thing being located is no longer just an object, it's an event, which is an object existing at a particular location and time.

However, the word "dimensions" has multiple meanings. In physics it's a location in space-time, but in common usage it's also used to describe something. The length, width, and height are called its dimensions. Maybe that's what you're thinking of.

[barmar]

Going back to the original question, if you find time confusing you're in good company. The physics community doesn't have a good idea what time really is, either. They know how to use it as a dimension in all their calculations, but they don't really understand why it "flows", but other dimensions don't. Time is different from the other dimensions -- the direction of its flow figures into the 3rd Law of Thermodynamics (entropy increases as time flows). Physics is symmetrical regarding left/right, up/down, and forward/backward, but past/future are different from each other. Cosmologists have some theories about this, but I don't think they've reached anything close to a concensus.

[Winstonm]

I really appreciate you guys chiming in with your thoughts. I do find this subject fascinating, but have the handicap of no training at all to help me understand. I have to attack it somewhat like a thought problem.

I may not grasp the Heisenberg uncertainty principle, but I thought it stated that a the subatomic level we can never know both the position and the velocity of an object.

My thoughts on this subject are along the lines that any correct theory must be able to solve the paradoxes between subatomic physics and other physics, and it seems to me that understanding time will be imperative to that end.

[qwery_hi]

Winstonm, on May 14 2009, 04:47 PM, said:

I really appreciate you guys chiming in with your thoughts. I do find this subject fascinating, but have the handicap of no training at all to help me understand. I have to attack it somewhat like a thought problem.

I may not grasp the Heisenberg uncertainty principle, but I thought it stated that a the subatomic level we can never know both the position and the velocity of an object.

My thoughts on this subject are along the lines that any correct theory must be able to solve the paradoxes between subatomic physics and other physics, and it seems to me that understanding time helps that end.

Hey Winston, you should check out "Fabric of the cosmos"

[Lobowolf]

So Werner Heisenberg gets pulled over for speeding...the cop comes and taps on his window and says, "Excuse me, Sir, but do you know how fast you were going?" Heisenberg says, "No, but I know where I am!"

[Winstonm]

Lobowolf, on May 14 2009, 08:08 PM, said:

So Werner Heisenberg gets pulled over for speeding...the cop comes and taps on his window and says, "Excuse me, Sir, but do you know how fast you were going?"  Heisenberg says, "No, but I know where I am!"

That's good. LoL.

A corollary joke:

So Werner Heisenberg gets pulled over for speeding....the cop comes and taps on his window and says, "Excuse me, Sir, but where's the fire?" Heisenberg says, "I know I was going 68 miles per hour. How can I possibly know the location of the fire, too?"

[Winstonm]

qwery_hi, on May 14 2009, 08:05 PM, said:

Winstonm, on May 14 2009, 04:47 PM, said:

I really appreciate you guys chiming in with your thoughts.  I do find this subject fascinating, but have the handicap of no training at all to help me understand.  I have to attack it somewhat like a thought problem.

I may not grasp the Heisenberg uncertainty principle, but I thought it stated that a the subatomic level we can never know both the position and the velocity of an object. 

My thoughts on this subject are along the lines that any correct theory must be able to solve the paradoxes between subatomic physics and other physics, and it seems to me that understanding time helps that end.

Hey Winston, you should check out "Fabric of the cosmos"

Will do. Thanks.

I realize my lack of knowledge and education in this subject can make me appear foolish to the knowledgeable, but I don't care about that. I enjoy the challenge of thinking about this stuff.

[Trinidad]

True story.

I am a scientist who was supposed to meet some fellow scientists in a building in the Heisenberg street, a small street in the city of Münster, Germany. One of these came over 20 minutes late. His taxi driver couldn't find the Heisenberg street.

This scientist joked: "How can you possibly schedule any meeting in the Heisenberg street? You know that there will be uncertainty about the precise location!"

Another scientist replied: "I know precisely where my hotel is. It is on the Einstein street. I just never know when I am there."

Rik

[kenberg]

Regarding the possibility of thinking through issues such as the Heisenberg Uncertainty Principle w/o a lot of specialized training, I also present a true story:

Some years back there was a plan to have the various departments nominate a short list of upper level courses as suitable for students outside of the major. All students would be required to take some of these in the interest of broadening their horizons. I was assigned to write a description of why the course in non-euclidean geometry would be suitable, a friend was to take on number theory. My proposal was accepted, his was not. He came across the hall and read mine, after which he said "Ken, you write really good bullshit". I took this as a compliment. He rewrote his proposal, using mine as a guide, and number theory was put on the list of suitable courses.

Nothing that I said in the description was a lie, but neither would it stand up to a determined examination for technical accuracy. I hope my life never depends on me being able to defend exactly what is the difference between a lie and not exactly technically accurate. Sill, I think it is possible for scientists to describe in general terms what they are about, but the public then has to accept that if they really want to grasp the issue, they need to dive in fully and for an extended length of time.


Btw, I really liked the Heisenberg/Einstein story.

[se12sam]

The time concept is somewhat mind-boggling to unravel. Based on whatever little bit I know (and I confess I know very little):

1. Time is a dimension EXACTLY like space. That's why Einstein called it space-time.
2. Visualise the universe moving on TIME dimension at light speed. That's the mind-boggling bit -- the universe is in motion (on 1 of the 4 space-time dimensions) at the speed of light.
3. We learnt that Einstein's theory states nothing can travel faster than light (but it can travel at the speed of light).

Now take any object and impart it velocity along a space dimension. If we know that point #3 is valid, then every body with velocity on a space dimension slows down on the time dimension.

So when you drive a car to work, your time slows down compared to that of your partner who chooses to stay at home!! The reason we cannot sense the change is that our controlled velocities are so insignificantly smaller than the speed of light that the time distortion is of an imperceptible amount.

If you managed to get into a body that reaches (say) 20% of the speed of light, your movement on the time dimension will slow down (perhaps to 80% of the speed on earth). So if I travel to a distant planet and back @ 20% of light speed and took 4 years to complete the journey (as per the onboard clock), I will find that it's been 5 earth years since I left. And both my clock and that on earth would be correct!

At the speed of light (space dimension), your movement along the time dimension reaches a speed of zero. The time dimension still exists, but it is as if you are glued to one place (in time, instead of in space). It is easy to visualise oneself glued to a fixed place (in space). The same principle when extended to time gives you the idea.

[helene_t]

I did my M.Sc. externship at an electronics company that needed a mathematics extern to develop a heuristic that could approximate the wavelet-transform of a sampled sound trail in a fast way. It was great fun and gave me a taste of applied physics, something I didn't do much of during my college years.

The wavelet transform basically works by folding the signal with a particular kernel. Use a narrow kernel and you get an accurate estimate of the timing of the acoustic events, but an inaccurate estimate of the pitch (frequency) of the sound. Use a wide kernel and you get the opposite. Now it turns out that the standard error of the frequency multiplied by the standard error of the time was a constant. This is very similar to Heisenberg's equation so the engineers called said constant the "Heisenberg number".

I didn't understand much of the theory so I just did what you can expect from a clueless statistician, namely trying out all kinds of ad-hoc regression models until I found one which mysteriously gave good predictions of the exact wavelet transform and made the engineers happy. But I am still wondering how deep the analogy is. Suppose we are observing a light signal rather than sound. By Planck's equation, the frequency of a photon is proportional to its energy, so if a "measurement" works by folding a sampled signal with some kernel, then we are back at Heisenberg's equation.

[kenrexford]

If a man takes of in a rocket at a very fast rate of speed, and then returns, he will have aged slower than the people at home, they say.

So, suppose he makes several shorter trips at the same speed. Same net result, right?

What if his trip went in circles? Out into the vast unknown in a circular path, returning back each time, all in circles.

What if these circles were really small, like maybe eight feet away, always returning, always fast?

What if he was just spinning around a central spot like a tetherball, going really fast in circles?

What is "he" was a block of uranium? That would seem to slow down the decay rate relative to us.

Now, the tetherball of uranium would have a larger mass than usually. But, what if the tetherball was made of something that has no mass?

What if you could spin something that had no mass in a circle? Perhaps not spin, but simple re-direct it in a circle? Like, perhaps light somehow trapped in a closed loop of fiber optic cables?

Or, what if the object, mass or no mass, just shook violently? Or, spun violently?

I'm not sure where this leads, and I cannot remember how I decided this, but somehow all of this seemed to me years ago to suggest that disk-shaped spinning devices (or tubes of trapped light) might somehow play havoc on and actually reduce the effect of gravity, or at least the felt effect of gravit, so as to create a theoretically-plausible means of elevating things or reducing the relative weight of the thing such that heavier atmospheres might "lift" the thing. Something like that.

[jdonn]

My head feels like a slowly-aging spinning tetherball of uranium.