The Naked Scientists

The Naked Scientists Forum

Author Topic: Do we know exactly what time is?  (Read 23989 times)

Offline Alan McDougall

  • Neilep Level Member
  • ******
  • Posts: 1285
  • Thanked: 14 times
    • View Profile
Do we know exactly what time is?
« on: 18/06/2013 16:37:20 »
Hi

What is time?

Some say it is just measure of movement or an aggregation of events. Time is not a constant and I would like you guys to put forward your own ideas on the topic before adding my piece to the story.

Alan


 

Offline yor_on

  • Naked Science Forum GOD!
  • *******
  • Posts: 11978
  • Thanked: 4 times
  • (Ah, yes:) *a table is always good to hide under*
    • View Profile
Re: Do we know exactly what time is?
« Reply #1 on: 18/06/2013 17:03:03 »
:)

locally it is a constant.

It's only when you compare over frames of reference you find it to give you a time dilation. Using gravitational time dilations your body can be defined to belong to different 'time zones' if you like. But from each position (loosely speaking) in SpaceTime its clock has a 'constant rate', definable as locally invariant, just as 'c' will be so for each of those 'frames of reference'. That as a 'gravity' can be translated, according to the equivalence principle, into a uniform constant acceleration. So you can consider all those 'points' of your body as 'differently gravitationally accelerating', although each one of them must present you with 'c' locally, as a 'constant', just as they must with that  'arrow'.

And that is a local definition.

Defining time 'globally', you have to measure over 'frames of reference'. Doing so you compare far away clocks relative your 'local clock', macroscopically defined as being 'at rest' with you (although still subject to microscopic gravitational time dilations). As you in your observatory, measuring, using the clock on the wall as your local reference. Then 'a far away arrow' becomes subject to Lorentz transformation, to fit your local one.

It's a very tricky subject, for example, where is a consciousness situated? Does it have a specific location, or is it a synthesis, undefinable to any single location, over a brain? If it is a synthesis and we assume that it should be able to define a 'frame of reference' as something meaningful in itself (physically). Then choosing Planck scale as the 'smallest common nominator' for both 'c' and that  local arrow. Then your brain, and subsequent thoughts, must handle 'time dilations' as well as 'Lorentz contractions', assuming that those two are complementary.
=
corrected a question mark :)
da*n.
=

As I already destroyed the unspoiled beauty of my post, if you're considering presenting a new theory, TNS have a lovely spot for those in 'New Theories'.

And a simple proof for a arrow, as being a local 'constant', is the fact that wherever you go that 'local clock' follows you. And your lifetime, relative that clock, is a set one.
« Last Edit: 18/06/2013 17:32:36 by yor_on »
 

Offline AndroidNeox

  • Sr. Member
  • ****
  • Posts: 251
  • Thanked: 2 times
    • View Profile
Re: Do we know exactly what time is?
« Reply #2 on: 24/06/2013 22:05:18 »
This sort of metaphysical question isn't what contemporary physics excels at... the general mental rigor of natural philosophy has been replaced by mathematical expertise (even if the equations are often misapplied).

I think that a better question than "what is time?" is, "when we measure time, what do we measure?". The first includes the assumption that time is something. Time doesn't seem to be a "something" any more than space does. Neither are conserved quantities. Einstein felt that "space" had no meaning independent of the fields within it.

When we measure time we are counting a sequence of events: heart beats, pendulum swings, quartz vibrations, etc. When we time some process we are comparing counts of two or more sequences.
 

Offline Alan McDougall

  • Neilep Level Member
  • ******
  • Posts: 1285
  • Thanked: 14 times
    • View Profile
Re: Do we know exactly what time is?
« Reply #3 on: 25/06/2013 10:03:59 »
:)

locally it is a constant.

It's only when you compare over frames of reference you find it to give you a time dilation. Using gravitational time dilations your body can be defined to belong to different 'time zones' if you like. But from each position (loosely speaking) in SpaceTime its clock has a 'constant rate', definable as locally invariant, just as 'c' will be so for each of those 'frames of reference'. That as a 'gravity' can be translated, according to the equivalence principle, into a uniform constant acceleration. So you can consider all those 'points' of your body as 'differently gravitationally accelerating', although each one of them must present you with 'c' locally, as a 'constant', just as they must with that  'arrow'.

And that is a local definition.

Defining time 'globally', you have to measure over 'frames of reference'. Doing so you compare far away clocks relative your 'local clock', macroscopically defined as being 'at rest' with you (although still subject to microscopic gravitational time dilations). As you in your observatory, measuring, using the clock on the wall as your local reference. Then 'a far away arrow' becomes subject to Lorentz transformation, to fit your local one.

It's a very tricky subject, for example, where is a consciousness situated? Does it have a specific location, or is it a synthesis, undefinable to any single location, over a brain? If it is a synthesis and we assume that it should be able to define a 'frame of reference' as something meaningful in itself (physically). Then choosing Planck scale as the 'smallest common nominator' for both 'c' and that  local arrow. Then your brain, and subsequent thoughts, must handle 'time dilations' as well as 'Lorentz contractions', assuming that those two are complementary.
=
corrected a question mark :)
da*n.
=

As I already destroyed the unspoiled beauty of my post, if you're considering presenting a new theory, TNS have a lovely spot for those in 'New Theories'.

And a simple proof for a arrow, as being a local 'constant', is the fact that wherever you go that 'local clock' follows you. And your lifetime, relative that clock, is a set one.

Even locality is not in absolute terms a constant, simply because the different parts of you physical body move at differently rates, relative to other parts of your body. Thus, your legs might be moving due to walking and your arms held over your head stationary to the rest of your torso. Thus, relative to each other they are moving at different rates and this effects time, albeit so infinitesimally tiny, that on our human macro scale it is meaningless, but, nevertheless real in the quantum world of the minute.

Time is really a mystery?

Alan

Alan
 

Offline evan_au

  • Neilep Level Member
  • ******
  • Posts: 4096
  • Thanked: 245 times
    • View Profile
Re: Do we know exactly what time is?
« Reply #4 on: 25/06/2013 10:49:40 »
Quote
your arms held over your head stationary to the rest of your torso
If your hands are over your head, then they are further out of Earth's gravitational field.
So time passes more rapidly for your hands than your feet (by an infinitesimal but measurable amount).
 

Offline Alan McDougall

  • Neilep Level Member
  • ******
  • Posts: 1285
  • Thanked: 14 times
    • View Profile
Re: Do we know exactly what time is?
« Reply #5 on: 25/06/2013 15:30:30 »
Quote
your arms held over your head stationary to the rest of your torso
If your hands are over your head, then they are further out of Earth's gravitational field.
So time passes more rapidly for your hands than your feet (by an infinitesimal but measurable amount).

What you stated is true, but so is my example!

I, however, disagree that it is possible to measure the difference rates of time, between your hand and feet due to the effect of gravity? The force of gravity is incredibly weak and the effect you are referring to is simply imperceptible to our very best measuring devices, even atomic clocks would not pick up this effect.

Alan

Alan
« Last Edit: 25/06/2013 15:39:41 by Alan McDougall »
 

Offline yor_on

  • Naked Science Forum GOD!
  • *******
  • Posts: 11978
  • Thanked: 4 times
  • (Ah, yes:) *a table is always good to hide under*
    • View Profile
Re: Do we know exactly what time is?
« Reply #6 on: 25/06/2013 15:38:26 »
Yep, you can use gravitational time dilations and their complementary Lorentz contractions to define 'time zones'. But to do that you need a 'local clock' from where to compare it. There are two ways to define one single frame of reference. You can either use being 'at rest', as we macroscopically can be defined being 'at rest' with earth in its relative motion. Or you can refer to some 'inertially defined' object.

Then there is a third that I'm wondering about, and that is in fact that 'local clock' you either way must use, no matter if you define it macroscopically or microscopically.

It exists, and you can't work around it. And that one, if possible to define, I would define as belonging to Planck scale, as that is where light 'freeze' :), holding at one Planck length in one Planck time. As well as it is there physics stops giving you meaningful answers.
« Last Edit: 25/06/2013 15:40:21 by yor_on »
 

Offline yor_on

  • Naked Science Forum GOD!
  • *******
  • Posts: 11978
  • Thanked: 4 times
  • (Ah, yes:) *a table is always good to hide under*
    • View Profile
 

Offline Alan McDougall

  • Neilep Level Member
  • ******
  • Posts: 1285
  • Thanked: 14 times
    • View Profile
Re: Do we know exactly what time is?
« Reply #8 on: 25/06/2013 15:46:21 »
Yep, you can use gravitational time dilations and their complementary Lorentz contractions to define 'time zones'. But to do that you need a 'local clock' from where to compare it. There are two ways to define one single frame of reference. You can either use being 'at rest', as we macroscopically can be defined being 'at rest' with earth in its relative motion. Or you can refer to some 'inertially defined' object.

Then there is a third that I'm wondering about, and that is in fact that 'local clock' you either way must use, no matter if you define it macroscopically or microscopically.

It exists, and you can't work around it. And that one, if possible to define, I would define as belonging to Planck scale, as that is where light 'freeze' :), holding at one Planck length in one Planck time. As well as it is there physics stops giving you meaningful answers.

I agree at the Plank limits such as Plank time we can't get meaningful answers, however, do we know for sure that the Plank limits on time are really the absolute smallest possible division of time? Has this been proven in any scientific experiment?
 

Offline yor_on

  • Naked Science Forum GOD!
  • *******
  • Posts: 11978
  • Thanked: 4 times
  • (Ah, yes:) *a table is always good to hide under*
    • View Profile
Re: Do we know exactly what time is?
« Reply #9 on: 25/06/2013 15:58:49 »
You can't prove anything, as none can probe that scale Alan, that is as far as I know. What makes me define that way is that it is a limit for what makes sense physically. Under it we meet a new regime. If you use 'c' (locally measured), and split it into even chunks of 'time', to define ones local arrow, then at Planck scale that arrows stops 'move' just as light. What then might be 'under it' must be 'something totally else'. You do not have a arrow (locally defined) under that scale as I expect.
 

Offline yor_on

  • Naked Science Forum GOD!
  • *******
  • Posts: 11978
  • Thanked: 4 times
  • (Ah, yes:) *a table is always good to hide under*
    • View Profile
Re: Do we know exactly what time is?
« Reply #10 on: 25/06/2013 16:12:06 »
The problem with probing something is that you will use your local arrow (clock) to measure. So if we define it this way you will still measure it 'taking time' by the macroscopically, arbitrarily defined, 'clock' you do use in your measurement. To really define it, measuring by a experiment, should be impossible as we are talking about something at Planck scale, and measured strictly locally 'in itself', not by you using a macroscopic definition of a 'local clock' to measure it by. It becomes a contradiction in terms doing it by comparing. The only way you can define time as 'stopping' is relative another frame of reference, as you measuring a event horizon using that local clock of yours to compare it to. And that one is only true relative your clock, for someone at that event horizon, 'locally' defined, time is as always and ticks. But to measure inside a frame of reference, being at one Plank length, belongs to science fiction so far :) Never the less, my logic works for me. We all need that 'local clock' to exist, and it 'ticks' relative 'c', both locally defined as constants, but the clock is not well defined quantum mechanically.
 

Offline yor_on

  • Naked Science Forum GOD!
  • *******
  • Posts: 11978
  • Thanked: 4 times
  • (Ah, yes:) *a table is always good to hide under*
    • View Profile
Re: Do we know exactly what time is?
« Reply #11 on: 25/06/2013 16:27:49 »
Using it this way moves 'c' from being a 'speed', to instead becoming a pure mathematical constant. Locally defined and locally true, wherever you go, however fast you find it, relative some other frame of reference. Every constant that exists must be true locally defined. We then compare our local descriptions with each other, and if we find them agreeing from our locally expressed 'repeatable experiments', we lift them up to constants. But locality and that clock, to me that is, starts at Planck scale, as 'c' begets a 'speed' over frames of reference, always locally defined. Although depending on choice of macroscopic clock, still arbitrarily done from a quantum mechanical point of view.
« Last Edit: 25/06/2013 16:34:41 by yor_on »
 

Offline Alan McDougall

  • Neilep Level Member
  • ******
  • Posts: 1285
  • Thanked: 14 times
    • View Profile
Re: Do we know exactly what time is?
« Reply #12 on: 25/06/2013 16:39:34 »
You can't prove anything, as none can probe that scale Alan, that is as far as I know. What makes me define that way is that it is a limit for what makes sense physically. Under it we meet a new regime. If you use 'c' (locally measured), and split it into even chunks of 'time', to define ones local arrow, then at Planck scale that arrows stops 'move' just as light. What then might be 'under it' must be 'something totally else'. You do not have a arrow (locally defined) under that scale as I expect.

I wonder does time flow like a river or can it be broken down into smaller and smaller discrete moments , something like frames on a movie reel?
 

Offline yor_on

  • Naked Science Forum GOD!
  • *******
  • Posts: 11978
  • Thanked: 4 times
  • (Ah, yes:) *a table is always good to hide under*
    • View Profile
Re: Do we know exactly what time is?
« Reply #13 on: 25/06/2013 16:53:36 »
From my thinking :) I think it 'flows', because as long as we introduce one more frame, comparing between two, you must find 'c', and that goes microscopically as well as well as macroscopically. you can only 'freeze' that arrow using one single frame of reference, and, as I think? How would one do that measurement? But you can also consider it a 'bit' as we, at least theoretically, might be able to define it as a 'quanta of time' at Planck scale.
 

lean bean

  • Guest
Re: Do we know exactly what time is?
« Reply #14 on: 25/06/2013 18:30:45 »
I, however, disagree that it is possible to measure the difference rates of time, between your hand and feet due to the effect of gravity? The force of gravity is incredibly weak and the effect you are referring to is simply imperceptible to our very best measuring devices, even atomic clocks would not pick up this effect.
Alan
If the distance between your head and feet is one metre or just under, then these chaps claim to have measured/detected the relative time difference over that distance.

Quote
We can now also detect time dilation due to a change in height near Earth’s surface of less than 1 meter. This technique may be extended to the field of geodesy, with applications in geophysics and hydrology as well as in space-based tests of fundamental physics.
From http://adsabs.harvard.edu/abs/2010Sci...329.1630C

Quote
In 2010, Chou et al. performed tests in which both gravitational and velocity effects were measured at velocities and gravitational potentials much smaller than those used in the mountain-valley experiments of the 1970's. It was possible to confirm velocity time dilation at the 10-16 level at speeds below 36 km/h. Also, gravitational time dilation was measured from a difference in elevation between two clocks of only 33 cm
from http://en.wikipedia.org/wiki/Hafele%E2%80%93Keating_experiment#Similar_experiments_with_atomic_clocks
« Last Edit: 25/06/2013 18:53:19 by lean bean »
 

Offline Alan McDougall

  • Neilep Level Member
  • ******
  • Posts: 1285
  • Thanked: 14 times
    • View Profile
Re: Do we know exactly what time is?
« Reply #15 on: 25/06/2013 19:12:11 »
I, however, disagree that it is possible to measure the difference rates of time, between your hand and feet due to the effect of gravity? The force of gravity is incredibly weak and the effect you are referring to is simply imperceptible to our very best measuring devices, even atomic clocks would not pick up this effect.
Alan
If the distance between your head and feet is one metre or just under, then these chaps claim to have measured/detected the relative time difference over that distance.

Quote
We can now also detect time dilation due to a change in height near Earth’s surface of less than 1 meter. This technique may be extended to the field of geodesy, with applications in geophysics and hydrology as well as in space-based tests of fundamental physics.
From http://adsabs.harvard.edu/abs/2010Sci...329.1630C

Quote
In 2010, Chou et al. performed tests in which both gravitational and velocity effects were measured at velocities and gravitational potentials much smaller than those used in the mountain-valley experiments of the 1970's. It was possible to confirm velocity time dilation at the 10-16 level at speeds below 36 km/h. Also, gravitational time dilation was measured from a difference in elevation between two clocks of only 33 cm
from http://en.wikipedia.org/wiki/Hafele%E2%80%93Keating_experiment#Similar_experiments_with_atomic_clocks

If that is true, it is beyond amazing!
 

Offline yor_on

  • Naked Science Forum GOD!
  • *******
  • Posts: 11978
  • Thanked: 4 times
  • (Ah, yes:) *a table is always good to hide under*
    • View Profile
Re: Do we know exactly what time is?
« Reply #16 on: 25/06/2013 23:47:31 »
You can see the universe we exist in two ways. The one we're most used to is the one in where we share a common universe. In that one we're 'here', all together. I can touch someone, they can touch me. We are 'here'.

In the other we're still here, but your definition of that universe is not mine. I can translate your definition to mine, you can translate mine to yours. If I would take a measurement of a distance in this universe it will be true for me, and my arrow of time, and life span, is directly connected to my measurement of 'c'. But to fit it to your description of a universe, 'time' and a distance we might need Lorentz transformations. We're still 'here' though, but what defines us is 'c', and frames of reference. I was stuck on this one for the longest time, and in a way I still am.

To reconcile those two definitions we use the same constant, 'c'. But looking at it my way simplify some things, your life span for example. And the way we define a repeatable experiment. It becomes two definitions, depending on what view you take of life, the universe, and all, as Douglas Adams would have said :)

It's not as much as one must be truer, it's just that I like to simplify it, as good as I can.
 

Offline Alan McDougall

  • Neilep Level Member
  • ******
  • Posts: 1285
  • Thanked: 14 times
    • View Profile
Re: Do we know exactly what time is?
« Reply #17 on: 27/06/2013 13:26:45 »
You can see the universe we exist in two ways. The one we're most used to is the one in where we share a common universe. In that one we're 'here', all together. I can touch someone, they can touch me. We are 'here'.

In the other we're still here, but your definition of that universe is not mine. I can translate your definition to mine, you can translate mine to yours. If I would take a measurement of a distance in this universe it will be true for me, and my arrow of time, and life span, is directly connected to my measurement of 'c'. But to fit it to your description of a universe, 'time' and a distance we might need Lorentz transformations. We're still 'here' though, but what defines us is 'c', and frames of reference. I was stuck on this one for the longest time, and in a way I still am.

To reconcile those two definitions we use the same constant, 'c'. But looking at it my way simplify some things, your life span for example. And the way we define a repeatable experiment. It becomes two definitions, depending on what view you take of life, the universe, and all, as Douglas Adams would have said :)

It's not as much as one must be truer, it's just that I like to simplify it, as good as I can.

Although off topic, this does relate to your post above. How each person might perceive the same thing differently.

Take colour perception,do you see red exactly as I do RED or
BLUE. So long as our different perception are consistent with each other, how are we ever to know for sure, we are both observing the same thing in the exact same way?

Perception of time might be different from person , to person, under the exact same conditions?

Alan
 

Offline Pmb

  • Neilep Level Member
  • ******
  • Posts: 1838
  • Physicist
    • View Profile
    • New England Science Constortium
Re: Do we know exactly what time is?
« Reply #18 on: 27/06/2013 16:27:07 »
Hi

What is time?

Some say it is just measure of movement or an aggregation of events. Time is not a constant and I would like you guys to put forward your own ideas on the topic before adding my piece to the story.

Alan
I would define time as the phenomena which pertains to different configurations of the world around us.

 
What then is time? If no one asks me, I know what it is. If I wish to explain it to him who asks, I do not know. - St. Augustine
 

Offline Alan McDougall

  • Neilep Level Member
  • ******
  • Posts: 1285
  • Thanked: 14 times
    • View Profile
Re: Do we know exactly what time is?
« Reply #19 on: 27/06/2013 18:45:58 »
Hi

What is time?

Some say it is just measure of movement or an aggregation of events. Time is not a constant and I would like you guys to put forward your own ideas on the topic before adding my piece to the story.

Alan
I would define time as the phenomena which pertains to different configurations of the world around us.

 
What then is time? If no one asks me, I know what it is. If I wish to explain it to him who asks, I do not know. - St. Augustine



I would like to post a dream about time I had a few years ago, please!, I am not going metaphysical, my odd dream just shows how strange time and movement could be from different perspectives. It is not a reflection of reality

What I am now going to describe is very weird, but it is a lucid dream I have had and for which I simply have no explanation. I seem to go to another dimension or universe, where time and movement were reversed, relative to everything and me, in this alternate dimension, everyone was moving backwards in time and movement.

You might have heard the phrase, "In the land of the blind the one eyed man is king"

In this bizarre alternate reality, I who could move both back and forward appeared to be king as I could easily reveal or hide myself there. Take one example, I saw a man who was walking backward after a workday at 5 pm, to his bedroom when he got up at 9am.  As he started to walk backwards from his desk 5pm, from my perceptive, time and movement,I was walking forward. However, in his reality he was moving (walking) back in time to the morning when he left for work at 9am. (moment)

From my viewpoint, I arrived at the moment he began to walk backward from his work desk at 5pm, to the elevator, reversing back to the moment when he got up at 9am in the morning. As I watched him he synchronized exactly with the elevator the moment door of the elevator opened, without looking, he just backed into the elevator. Weird not really! If you play the scenario forward in time and movement, when the elevator reached his floor, it opened and he got out and went to his desk, as if anyone would in our reality.

To try and make him aware my presence, I walked forward in front of him, because from my perspective, he was reversed and walking backward, from his evening at 5pm to his morning at 9pm, when he got up for work. He became very distressed by me, because he saw me, as a being that suddenly appeared in front of him. From his perceptive as he walked forward to his desk, he saw me walking backward in front of him in, no matter how hard tried to get rid of this apparition, that was I, I was always in front of him, reversing by walking backward relative to him. During another moment, I got behind him as he was walking backward and stopped him by placing my hands firmly on his back, thus, in his world he was suddenly stopped by some sort of outside force with a weird sense that there was another entity behind him that he could not identify. I think the hairs on his neck stood up straight. I could really have fun here I was the phantom of the opera in that moment.

In my dream, he was a very real person and I could see he was confused even frightened by the apparition, that was I. To him, I had become an unpleasant ghostly thing from some alternate reality. The interaction between these two alternate reversed time dimensions, were so complex, I think maybe one would need more than an Einstein, to explain what was really going on.

For instance, I noticed that at moments he could see me and tried to rush at me and touch me. When he did that, I simply stood still and slowly receded out of view, from his perceptive. When he to rushed/ran toward me, the time, the time, distance and movement variations between our alternate realities just increased. When he ran faster and faster toward me all that happened was, I moved receded faster and faster backward in distance and time from him.

The harder he tried to touch or reach me, the more I receded. "Weird" very "Weird" From his perspective he was moving forward in time, and I was reversing time and movement. I following him back from 5 pm, the moment he was supposed to knock off work him, until 9 am when he left for work and got out of bed. The dream is hard to explain and confusing and convoluted, but it really gives one a glimpse of how strange time and movement can be from different perspectives and perceptions.

Alan  8D
 

Offline RD

  • Neilep Level Member
  • ******
  • Posts: 8124
  • Thanked: 53 times
    • View Profile
Re: Do we know exactly what time is?
« Reply #20 on: 27/06/2013 20:09:17 »
... it is a lucid dream I have had and for which I simply have no explanation. I seem to go to another dimension or universe, where time and movement were reversed ...

Are you sure it wasn't the "backwards" episode of "Red Dwarf"  :) ...

Quote from: wikipedia.org/wiki/Backwards_(Red_Dwarf_episode)
Kryten and Rimmer think that the backwards world is wonderful, pointing out that when the second world war comes around again, millions of people will come back to life, and Hitler will retreat across Europe, liberating France and Poland. Lister though looks at the other side of the argument and states that in this universe St. Francis of Assisi is the petty-minded little sadist who maims small animals and that Santa Claus is a big guy who sneaks down chimneys and steals all the kids' favourite toys.
http://en.wikipedia.org/wiki/Backwards_%28Red_Dwarf_episode%29#Cultural_references
« Last Edit: 27/06/2013 20:19:24 by RD »
 

Offline Bill S

  • Neilep Level Member
  • ******
  • Posts: 1802
  • Thanked: 11 times
    • View Profile
Re: Do we know exactly what time is?
« Reply #21 on: 28/06/2013 03:07:59 »
Quote from: Alan
I following him back from 5 pm, the moment he was supposed to knock off work him, until 9 am when he left for work and got out of bed.

I assume you spotted the inconsistency here.  At 9am, had he been travelling backwards through time, he would have fallen backwards into bed, his alarm would have gone off and he would have gone to sleep.  Time reversal is a complex thing.  I'm very pushed for time at the moment, but I hope to have a chance to air a few of my thoughts on the subject.
 

Offline evan_au

  • Neilep Level Member
  • ******
  • Posts: 4096
  • Thanked: 245 times
    • View Profile
Re: Do we know exactly what time is?
« Reply #22 on: 28/06/2013 06:40:23 »
Quote
I, however, disagree that it is possible to measure the difference rates of time, between your hand and feet due to the effect of gravity
The aluminium clock experiment at NIST in 2010 were a significant advance in timekeeping. But I was referring to earlier measurements that were able to detect time dilation effects over altitude differences as small as 30mm (not 30 cm).

The earlier researchers had a coherent beam with a very short wavelength. They aimed it at a target which split the beam in 2 paths, and then recombined it, causing interference fringes.

By rotating the splitter/recombiner, they were able to make the two beams take paths with the same altitude or different altitudes, and they could see changes in the interference patterns. They interpreted the results as showing that when the beam was further from the Earth, time passed more rapidly, so the beam was out of phase when recombined with the lower beam.

This is a very difficult experiment due to the required mechanical tolerances, but was an ingenious way to demonstrate the effect of time dilation on human scales without requiring two calibrated clocks - you just need one stable source.
 

Offline syhprum

  • Neilep Level Member
  • ******
  • Posts: 3812
  • Thanked: 19 times
    • View Profile
Re: Do we know exactly what time is?
« Reply #23 on: 28/06/2013 11:01:09 »
I wonder if it has been considered when we seek to communicate with aliens that they may have vastly different life times than us and that their conception of time may be very different from ours.
If they have the life time of a mountain 1 Hz would be supersonic but if they have the life time of a fly it would represent an extremely low frequency. 
 

Offline Alan McDougall

  • Neilep Level Member
  • ******
  • Posts: 1285
  • Thanked: 14 times
    • View Profile
Re: Do we know exactly what time is?
« Reply #24 on: 28/06/2013 14:53:24 »
Quote from: Alan
I following him back from 5 pm, the moment he was supposed to knock off work him, until 9 am when he left for work and got out of bed.

I assume you spotted the inconsistency here.  At 9am, had he been travelling backwards through time, he would have fallen backwards into bed, his alarm would have gone off and he would have gone to sleep.  Time reversal is a complex thing.  I'm very pushed for time at the moment, but I hope to have a chance to air a few of my thoughts on the subject.

Yes it was difficult to write and keep in mind the two opposite arrows of time , within the alternate dimensions. I will look at your comment and correct the error.

Alan
 

The Naked Scientists Forum

Re: Do we know exactly what time is?
« Reply #24 on: 28/06/2013 14:53:24 »

 

SMF 2.0.10 | SMF © 2015, Simple Machines
SMFAds for Free Forums