PDA

View Full Version : Time ?



2001-Nov-01, 10:53 AM
second = Heart beat Minute = 60 hour 1/24 day
day = rev of Earth, week 1/4 Moon,
Month =Moon -Moon; Year = Earth Orbit; etc
do the units remain constant?
in the easiest case, the Moon, expanding its
orbit slows ? so a "Lunar" month New-New
might lengthen if the earths rotation rate
was not also slowing equivantly? Across the
Broad spectrum, electron orbit proton, to
Sun orbits Galatic center? How does it plot?

Matherly
2001-Nov-01, 12:34 PM
{Carl blinks}

Oh dear lord, I'm understanding HUb'. I've been here waaaay too long.

Anyways, you do raise an intresting point about the measurment of time. Does anyone out there know of a way to measure a unit of time that is always constant? (that is, it always yelds the exact same length of time). I sure can' think of one.

(Oh, and to head this on off at the pass, I am unconcerned about relativity here. Keep the measurments within the same frame of referance at the same velocity, etc.)

SeanF
2001-Nov-01, 02:11 PM
Well, the current "official" definition of a second is 9,192,631,770 "vibrations" of a Cesium-133 atom.

But, of course, that assumes that the atoms always vibrate at a constant rate.

I don't think there's any way to do it, since any measurement of time is going to be based on physical motion of some kind, and there's nothing independent to compare it against.

Even if you had two clocks that measured time in completely different ways, if they started to "drift apart," how would you know which one wasn't maintaining accuracy?

Days, years, and lunar months are changing -- or are they? We're measuring them based on atomic clocks. Maybe the year is actually keeping the same length but those dang cesium atoms are starting to speed up?

/phpBB/images/smiles/icon_wink.gif

Valiant Dancer
2001-Nov-01, 05:00 PM
On 2001-11-01 05:53, HUb' wrote:
second = Heart beat Minute = 60 hour 1/24 day
day = rev of Earth, week 1/4 Moon,
Month =Moon -Moon; Year = Earth Orbit; etc
do the units remain constant?
in the easiest case, the Moon, expanding its
orbit slows ? so a "Lunar" month New-New
might lengthen if the earths rotation rate
was not also slowing equivantly? Across the
Broad spectrum, electron orbit proton, to
Sun orbits Galatic center? How does it plot?


Are we talking about a permanent way of measuring a second? I don't think one exists. The only constant in the universe is change. Within one Terran lifetime, the Cesium 133 "vibrations" are pretty stable. Although to keep it in line with the spinning and revolving Earth year, occasionally there will be a leap second. Last one was about 2 years ago (I think). I wasted that second, too. What did you do with it? I think that the standard time keeping standard is even divisions of the Terran year. When months were truely Moon to Moon, there were five to six festival days which didn't count as any one month.

SeanF
2001-Nov-01, 05:15 PM
On 2001-11-01 12:00, Valiant Dancer wrote:

Although to keep it in line with the spinning and revolving Earth year, occasionally there will be a leap second. Last one was about 2 years ago (I think). I wasted that second, too. What did you do with it?


I wasted it, too, Dancer. I remember it, though, because I remember being at a party at a friend's house and watching the count-down on TV, thinking, "Gee, they're going to be celebrating a second too early!"

Does that make me a geek?

Diogenes
2001-Nov-01, 06:27 PM
All that matters, is, that our method of time-keeping, enables us to do do what we need to do.


Accuracy (when it comes to time) has no meaning apart from relativity.. (not 'the theory of)Any method of measuring (time) is only accurate with respect to some reference point that has been arbitrarily established.

Azpod
2001-Nov-01, 06:33 PM
Define wasting a second. I breathed; my heart beat, and because I was alive, you can't truly say that I wasted that second. Being dead, on the other hand, well... that does tend to be a waste of time.

That does bring up a good point, though: how does one consider an hour, or a day a waste of time, but be able to determine if said time was wasted on a second-by-second basis?

*ponder* I probably should see a whole lot of really bad movies and study the phenomenon. But would that be a waste of time, since I am studying something...?

OK, now my brain hurts. Hope your happy.

/phpBB/images/smiles/icon_smile.gif

Simon
2001-Nov-01, 08:24 PM
Erm... Yeah, I think that atomic clocks are the easiest way... If you compare the decay rates of several various elements, I think you might get a more exact answer.

You could, of course, measure the time it takes a beam of light to cover a set distance.

I believe that under ideal conditions, bacteria divide very regularly... though I think I'm getting weird here...

Pulsars spin very regularly and are relatively easy to keep track of, but even they slow down. Of course, if you know how FAST they slow down and can measure it very very accurately, you can not only tell the interval between two points of time but what time it IS (I mean you look at your radio telescope and say "Oh, this pulsar's spinning 432.533...... times a second, it must be the first of November, 2001").

Did that make any sense? It's midnight, so it's sorta hard to tell...

Phobos
2001-Nov-02, 02:01 AM
With a little thought I believe there are very logical ways to improve upon our definition of time.

Personally I believe time should be based upon a constant which we could call a Galactic Time Period (GTP) which would be defined as the time period between the big bang, and the formation of the first star in our galaxy as measured by an observer located in the gravitational centre of our galaxy.

Once such a GTP had been agreed upon we could then define a galactic second as being a specific fraction of the GTP period, and we could use that definition thoughout our galaxy (so it could last us quite a while).

Jeff

<font size=-1>[ This Message was edited by: Phobos on 2001-11-01 21:04 ]</font>

David Simmons
2001-Nov-02, 03:00 AM
On 2001-11-01 09:11, SeanF wrote:
Well, the current "official" definition of a second is 9,192,631,770 "vibrations" of a Cesium-133 atom.

But, of course, that assumes that the atoms always vibrate at a constant rate. [Emphasis added]



Minor quibble. I don't agree with the comment in italics. The definition defines the second and definitions are exact. Whether or not the standard that is used to measure seconds in the standards laboratory measures the defined second is another question.

For example. The speed of light is exactly 299 792 458 meters/sec. This isn't true because we are so darned good at measuring the speed of light. Rather, 1 meter is now defined in terms of the speed of light.

So, we have to start someplace and we have to agree on that place and even if the place shifts, it is still the starting place. In this context I think that the place "shifting" has no meaning.



<font size=-1>[ This Message was edited by: David Simmons on 2001-11-01 22:06 ]</font>

SeanF
2001-Nov-02, 12:22 PM
On 2001-11-01 22:00, David Simmons wrote:



On 2001-11-01 09:11, SeanF wrote:
Well, the current "official" definition of a second is 9,192,631,770 "vibrations" of a Cesium-133 atom.

But, of course, that assumes that the atoms always vibrate at a constant rate. [Emphasis added]



Minor quibble. I don't agree with the comment in italics. The definition defines the second and definitions are exact. Whether or not the standard that is used to measure seconds in the standards laboratory measures the defined second is another question.

For example. The speed of light is exactly 299 792 458 meters/sec. This isn't true because we are so darned good at measuring the speed of light. Rather, 1 meter is now defined in terms of the speed of light.

So, we have to start someplace and we have to agree on that place and even if the place shifts, it is still the starting place. In this context I think that the place "shifting" has no meaning.

<font size=-1>[ This Message was edited by: David Simmons on 2001-11-01 22:06 ]</font>


Sorry, I should have been clearer. I was responding to Matherly's question:




Does anyone out there know of a way to measure a unit of time that is always constant? (that is, it always yelds the exact same length of time).



If the vibration rate of the cesium atoms is not constant, then it does not qualify as a solution to Matherly's question, regardless of whether we always change a "second" to match up with the counted vibrations.

SeanF
2001-Nov-02, 12:25 PM
On 2001-11-01 22:00, David Simmons wrote:

The speed of light is exactly 299 792 458 meters/sec. This isn't true because we are so darned good at measuring the speed of light. Rather, 1 meter is now defined in terms of the speed of light.



Which brings up another interesting point. Not only is our measurement of time subject to variability (if the cesium atoms' vibration rate isn't constant), but our measurement of distance is also subject to the same variability, because it's only as accurate as our measurement of time!

/phpBB/images/smiles/icon_smile.gif


_________________
SeanF

<font size=-1>[ This Message was edited by: SeanF on 2001-11-02 07:25 ]</font>

Valiant Dancer
2001-Nov-02, 01:11 PM
On 2001-11-01 13:33, Azpod wrote:
Define wasting a second. I breathed; my heart beat, and because I was alive, you can't truly say that I wasted that second. Being dead, on the other hand, well... that does tend to be a waste of time.

That does bring up a good point, though: how does one consider an hour, or a day a waste of time, but be able to determine if said time was wasted on a second-by-second basis?

*ponder* I probably should see a whole lot of really bad movies and study the phenomenon. But would that be a waste of time, since I am studying something...?

OK, now my brain hurts. Hope your happy.

/phpBB/images/smiles/icon_smile.gif



Your brain hurts? It will have to come out. (See Monty Python's Flying Circus for joke.)

David Simmons
2001-Nov-02, 01:44 PM
On 2001-11-02 07:22, SeanF wrote:

If the vibration rate of the cesium atoms is not constant, then it does not qualify as a solution to Matherly's question, regardless of whether we always change a "second" to match up with the counted vibrations.




I certainly didn't intend to "blow off" the necessity of a constant reference. If the base by which the second is measured keeps changing, it would certainly lead to numerous practical difficulties.

It seems to me we still use the good old reliable orbit of the earth in 31471200 seconds (give or take) in order to be assured that the standard isn't drifting. A change of a second or so every now and then is expected and can be accounted for by known physical effects of the tides, etc. But you can bet that if one year it was discovered that the atomic clocks' average drift was in the hundreds or even tens of seconds there would be some mighty agitated scrambling going on.

David Hall
2001-Nov-02, 02:21 PM
Your brain hurts? It will have to come out. (See Monty Python's Flying Circus for joke.)


Interesting coincidence. I just watched that very episode last night on videotape. I tell you, it's really strange to (try to) read Japanese subtitles on Monty Python. They just can't quite carry the real humor over. /phpBB/images/smiles/icon_lol.gif

Here's the sketch:

http://www.montypython.net/scripts/gumbybrain.php

/phpBB/images/smiles/icon_smile.gif /phpBB/images/smiles/icon_lol.gif /phpBB/images/smiles/icon_biggrin.gif /phpBB/images/smiles/icon_razz.gif

David Hall
2001-Nov-02, 04:59 PM
Speaking of Monty Python, and to get this a little bit back to the topic of this board, I've just discovered a little bit of Bad Astronomy in it. (Yeah, as if a small slip in a 30 year-old comedy show means much. /phpBB/images/smiles/icon_biggrin.gif)

Here's the link to the offending sketch. I'm going to make it more of a challenge by not telling you the actual BA, but since it's in the first line I don't think it should be too hard. /phpBB/images/smiles/icon_smile.gif

http://www.montypython.net/scripts/algon.php

Nick
2001-Nov-02, 11:54 PM
Everybody forgets...

All time is, is a measurement between events - much like a distance can be measured in feet, metres, hands etc.

But even the rulers we use expand or contract depend on the weather (temperature)...

Time is a measurement between events - it is all in the eye of the beholder.

Nick

Kaptain K
2001-Nov-05, 08:52 AM
"Time is God's way of keeping everything from happening at once." /phpBB/images/smiles/icon_biggrin.gif

2001-Nov-06, 11:09 AM
On 2001-11-05 03:52, Kaptain K wrote:
"Time is God's way of keeping everything from happening at once." /phpBB/images/smiles/icon_biggrin.gif


HUb' 20011106 4:45 A.M. PST 97209
well there were today 28 pages of "LYNX" text
and so I've added one more with this one
I DID NOT add anthing to the "TIME AGAIN"
thread to day . so I donno how long? /phpBB/images/smiles/icon_razz.gif29ed spelling change on to one:4:51 A.M.

<font size=-1>[ This Message was edited by: HUb' on 2001-11-06 06:13 ]</font>

2001-Nov-18, 10:43 AM
20011118 HUb' 4:09 A.M. # 9 MUCUK 7 CEH
{ed 1-11-18 4:23 A.M. } mostly regrouping


On 2001-11-01 05:53, HUb' wrote:

day = rev of Earth,
Year = Earth Orbit;
1-11-18 4:13 A.M. listen? I think now that
1: the Earth Day lengthens
a. because of the Moon &b. because of>Mass
2: the Year lengthens
a. Sun mass decreas b. Earth mass increas
{um} I think the Solar system expands mostly
due to loss of mass by the sun. & cools2

On 2001-11-01 12:00, Valiant Dancer wrote:
Are we talking about a permanent way of measuring a second? I don't think one exists. The only constant in the universe is change. Within one Terran lifetime, the Cesium 133 "vibrations" are pretty stable. Although to keep it in line with the spinning and revolving Earth year, occasionally there will be a leap second. Last one was about 2 years ago (I think). I wasted that second, too. What did you do with it? I think that the standard time keeping standard is even divisions of the Terran year. When months were truely Moon to Moon, there were five to six festival days which didn't count as any one month.
4:18 A.M. as far as a way to measure?
Mu guess it must be by using the Moon
reletive to itself, I'll work on this answer


<font size=-1>[ This Message was edited by: HUb' on 2001-11-18 05:47 ]</font>

jkmccrann
2005-Nov-15, 02:04 PM
second = Heart beat Minute = 60 hour 1/24 day
day = rev of Earth, week 1/4 Moon,
Month =Moon -Moon; Year = Earth Orbit; etc
do the units remain constant?
in the easiest case, the Moon, expanding its
orbit slows ? so a "Lunar" month New-New
might lengthen if the earths rotation rate
was not also slowing equivantly? Across the
Broad spectrum, electron orbit proton, to
Sun orbits Galatic center? How does it plot?

Time is an interesting phenomenon, it means different things to different people, which in my book means its not something that can be narrowly defined by use of the vibrations of the cesium atom.

Some people waste time, some people make time. Many people take their time, whilst others make sure to give of their time. And what does it all mean? Well, at the end of the day, time, and how much you have of that precious resource, is really a function of one's personality and how you choose to view the world. Is pressing snooze in the morning really something you need to do to make the most of your time? I guess it depends on what you're after.

swansont
2005-Nov-15, 11:59 PM
Even if you had two clocks that measured time in completely different ways, if they started to "drift apart," how would you know which one wasn't maintaining accuracy?


You can't. To start to have a fighting chance, you need three clocks so that you can do pair-wise comparisons (called a three-cornered-hat) which allows you to assess the behavior of the clocks to some degree.

swansont
2005-Nov-16, 12:04 AM
I wasted it, too, Dancer. I remember it, though, because I remember being at a party at a friend's house and watching the count-down on TV, thinking, "Gee, they're going to be celebrating a second too early!"

Does that make me a geek?


Unless you were in England at the time, it wasn't an issue. Leap seconds are added at midnight UTC, not midnight local time. (And the media invariably gets this wrong) It should make sense, too - you wouldn't want clocks in each time zone to be off by a second for the whole day while you switch them over.

edit to add: ...and I just realized these were posts from 2001, which explains how I could have missed them in the past few weeks

Hugh Jass
2005-Nov-16, 09:02 PM
Check on jkmccrann, view his all his posts, he's been resurrecting all kinds of threads recently. Good or bad is up for debate, but certainly annoying to think it is a recent discussion.