Just watched a program on Time and how it seems to confound scientists. It was explained that we can now measure time with extreme accuracy by utilizing the cesium atom. Apparently that gives us an accuracy of (+/-) 1 sec in perhaps 100 billion years. Impressive. But seconds, minutes, hours, days, etc. are only relative measurements to the earth and are meaningless elsewhere in the universe, except to us.

Everywhere else in the universe time is different. At near SOL time slows down and our cesium accuracy becomes meaningless in terms of real measurement. Perhaps this is why it confounds scientists so.

I may be wrong but to me time is one of the easiest natural phenomena to understand.

a) without space there is no time
b) without matter there is no time
c) without movement there is no time.
d) when all of the above are present there is time.

IMO, time is an emergent property in the creation and progression of physical reality itself. It cannot exist by itself and is created (emerges) as a result of quantum, i.e. matter moving from one space(time) coordinate to another. Even at quantum this shift in coordinates “takes or needs time”, and time is created (emerges) during the event. This concept holds true universally as a property of relativity. Without relativity there is no time.

Not sure I understand any of that. The main breakthrough in Einstein is the notion that there is no such thing as “time” per se. What there is is “spacetime”. For Einsteinian physics, “time” is a dimension just like the three of space. The main issue that ‘confounds’ people (philosophers more than scientists, I’d say) is in attempting to elucidate how or why it seems to us that time is different from space, when physics tells us it isn’t.

I don’t think time is “controversial” except to those of us who are limited in our knowledge about physics. Even physicist had little or no know knowledge about times except as we experience it on earth until Einstein came along. Then it all changed but its only controversial to those of use who know little about it.

I don’t think time is “controversial” except to those of us who are limited in our knowledge about physics. Even physicist had little or no know knowledge about times except as we experience it on earth until Einstein came along. Then it all changed but its only controversial to those of use who know little about it.

Well, that’s interesting. The physicists on the program aren’t even sure if the present is different from past and future, or whether travel to past or future is possible. They believe time will eventually cease to exist - that’s not controversial? Seems that we all are “limited in our knowledge about physics” in terms of time. Did you watch the show, deros?

I was only quoting the tv program, which specifically stated that while we can measure earth time with extreme accuracy, time, as a quality of spacetime itself is still a mystery.

As Doug said, space has three dimensions. But what is time? Is it sufficient to say that it is a dimension which seems different, though part of it?

IMO, time is not a dimension in and of itself, it is an emergent quality from activity within three dimensional space. Thus as soon as we begin to measure space, we create time, the interval “needed” to move from one space coordinate to another.
Thus space and time are inextricably connected, but only when there is matter (quanta).

Not sure I understand any of that. The main breakthrough in Einstein is the notion that there is no such thing as “time” per se. What there is is “spacetime”. For Einsteinian physics, “time” is a dimension just like the three of space. The main issue that ‘confounds’ people (philosophers more than scientists, I’d say) is in attempting to elucidate how or why it seems to us that time is different from space, when physics tells us it isn’t.

Hmm, I am not so sure. Physicists doing as if they know what time is, is not the same as physicists knowing what time is. The equal position of space dimensions and the time dimension can only be obtained by a mathematical trick: taking time multiplied by i (the imaginary i, sqrt(-1)).

The original Lorenz-invariance is:

x^2 + y^2 + z^2 = (ct)^2 (x,y,z are the space dimensions, c the velocity of light, t the time)

Now this can be rewritten as:
x^2 + y^2 + z^2 - (ct)^2 = 0

And then (here is the trick), by defining t = ict:
x^2 + y^2 + z^2 + t^2 = 0

So mathematically, we can define time in such a way that it behaves just like a space dimension. But when physicists do their calculations in this formalism, they always have to translate back to our normal time, with a normal timely order (imaginary numbers even have no order in the sense that 1 is less than 3), with past, present and future.

But surely, time and space are interrelated, but I would not say time is just like space.

(Sorry for the math. I think some people here understand what I am saying.)

Special note for Write4U: imaginary numbers have a perfect mathematical definition, which has nothing to do with our daily use of the word imagination.

The way I imagine it works is like this: The moment Forrest Gump opens his box of chocolate while sitting on the bench in the park can be found either at 58 minutes into the movie (time), or, if we measure the length of the actual strip of the film, it happens in frame number 14,557 (space). Same thing.

I do agree with Doug that a problem arises when we realize that we experience time as different from space. But I guess we won’t know why that is until we understand consciousness.

What was the motivation for this equality “trick”?

To make calculating easy… But of course to get ‘real time’ one must transfer this ‘imaginary time’ back to it.
A similar trick is used in calculations of oscillations (yes just electrical currents and so). Calculations with trigonometric functions (cosine, sine, etc) are notoriously complicated. By using Euler’s formula, one can use exponential functions which are often easier to work with. But again, in the end one must transform the results back to real numbers.

traveler - 10 November 2011 07:34 AM

Also, CPT violation has not been observed, correct?

Not sure, I have to Google myself… Found the funny gif below. Why are you asking?

Ah, I missed the italicized t in your original post - thanks.

traveler - 10 November 2011 07:34 AM

What was the motivation for this equality “trick”?

To make calculating easy… But of course to get ‘real time’ one must transfer this ‘imaginary time’ back to it.
A similar trick is used in calculations of oscillations (yes just electrical currents and so). Calculations with trigonometric functions (cosine, sine, etc) are notoriously complicated. By using Euler’s formula, one can use exponential functions which are often easier to work with. But again, in the end one must transform the results back to real numbers.

traveler - 10 November 2011 07:34 AM

Also, CPT violation has not been observed, correct?

Not sure, I have to Google myself… Found the funny gif below. Why are you asking?

Because I thought that both CPT and Lorenz invariance were preserved in field theory (from what little I remember). I like the GIF.

I do agree with Doug that a problem arises when we realize that we experience time as different from space. But I guess we won’t know why that is until we understand consciousness.

But consciousness exists in time too… Doesn’t it?
And explaining consciousness by its physical structure, which exists in time too, then also gives no solution… Doesn’t it?

Of course. What I find interesting, though, is how differently we perceive time when we are conscious compared to when we are sleeping and dreaming. I’ve had dreams (usually in the morning) that I know only lasted a few seconds, but they can feel hours long. Or when you incorporate a noise (e.g., alarm clock, door bell, etc.) into your dream as a part of that dream’s story and realize that the noise happened only a few seconds ago, even though the dream’s plot seemed to have been steering into the noise culmination for much much longer.

Well, I think however we approach the subject of time we should be careful to distinguish experienced time, which has the odd properties that George alludes to, from objective time. The latter is what the physics stuff from Einstein is about.