## Strange Question: Time Difference between stars

Message boards : SETI@home Science : Strange Question: Time Difference between stars
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RObert_5150

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Message 1644783 - Posted: 21 Feb 2015, 4:37:38 UTC

I am trying to understand what the time difference between starts and their respective plants.

For example, Lets assume that right now it's 6:00 PM "Earth Time" throughout the entire planet. In fact lets say there is only 1 time zone for all of earth.

What time would it be on mars?
What time would it be on Jupiter?
What time would it be on Pluto? (yes I know it got fired)

Now assuming my question wasn't entirely stupid, what time would it be:

On Sirius?
On any planets who "orbit" Sirius?

I am trying to figure out what the change in time is relative to the start itself.

Thanks

Robert
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Message 1644787 - Posted: 21 Feb 2015, 5:02:57 UTC - in response to Message 1644783.

Time, as we measure it here on Earth, is base 60, based upon the rotation of the Earth and how long it takes to make one 360 degree rotation on its axis.

Time zones are decided based upon the position of the Earth relative to the randomly chosen Meridian line. For example, if we were to pretend to stop the Earth for 12 hours (and pretend that it doesn't fling everyone off in the sudden stop), then start it spinning all over again, the US Central Time Zone would still be Meridian -6:00 hours. It would simply be that 6:00PM (PM meaning Post Meridian) would now be in the early hours of the morning and 6:00AM (AM meaning Ante Meridian) would be in the late evening relative to the daylight received.

None of this would apply to any other planet. Each planet would have their own spin, with differing amounts of time to complete a rotation, and likely different points for its imaginary Meridian line. Any given point on Earth is irrelevant to any point on another planet.

So, to answer your question: it wouldn't matter if its 6:00 here on Earth, it would be any o'clock on any other planet, relatively.
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RObert_5150

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Message 1644789 - Posted: 21 Feb 2015, 5:09:18 UTC - in response to Message 1644787.

Ok. thanks for the answer. So then the star has nothing to do with it and planets time measurement is basically localized to the planet itself, as you described.
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Message 1644790 - Posted: 21 Feb 2015, 5:14:58 UTC - in response to Message 1644789.

Yes, that's correct.
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Julie
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Message 1644848 - Posted: 21 Feb 2015, 9:39:18 UTC

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Message 1646261 - Posted: 25 Feb 2015, 6:48:19 UTC

Did you wanted to tell what is the difference 'cause of the gravity distorsion of the planet/star & speed of the system?
;)

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Julie
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Message 1646352 - Posted: 25 Feb 2015, 10:52:02 UTC - in response to Message 1646261.

Did you wanted to tell what is the difference 'cause of the gravity distorsion of the planet/star & speed of the system?
;)

I guess...;)
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Bob DeWoody

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Message 1646613 - Posted: 25 Feb 2015, 19:48:21 UTC

The fact that time passes is universal. The means by which we measure that passage is entirely subjective and a product of our local situation. A day is the time it takes the earth to make one revolution on it's axis. A year is the amount of time it takes for earth to make one revolution around the sun. A light year is a measure of the distance light travels in an earth year. As long as we are the only intelligent beings that we know of, how time gets measured is totally dependant on how we choose to do it.
Bob DeWoody

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Julie
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Message 1646618 - Posted: 25 Feb 2015, 19:55:30 UTC - in response to Message 1646613.

The fact that time passes is universal. The means by which we measure that passage is entirely subjective and a product of our local situation. A day is the time it takes the earth to make one revolution on it's axis. A year is the amount of time it takes for earth to make one revolution around the sun. A light year is a measure of the distance light travels in an earth year. As long as we are the only intelligent beings that we know of, how time gets measured is totally dependant on how we choose to do it.

+1 Stephen Hawking should take this advice.
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Josef W. Segur
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Message 1646644 - Posted: 25 Feb 2015, 20:59:12 UTC - in response to Message 1646613.

The fact that time passes is universal. The means by which we measure that passage is entirely subjective and a product of our local situation. A day is the time it takes the earth to make one revolution on it's axis. A year is the amount of time it takes for earth to make one revolution around the sun. A light year is a measure of the distance light travels in an earth year. As long as we are the only intelligent beings that we know of, how time gets measured is totally dependant on how we choose to do it.

A day as we measure it for ordinary use is the time period between sun crossings of the north-south line (solar day). The actual one revolution on earth axis relative to the "fixed stars" is shorter, about 23 hours 54 minutes and 4 seconds (sidereal day). Rotation around the sun effectively removes one day, so there's one more day in the sidereal year.

That doesn't make much difference except for astronomical observations, but since that's what we're analyzing it is important to the science we are doing.
`                                                                   Joe`
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Bob DeWoody

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Message 1646720 - Posted: 26 Feb 2015, 0:39:54 UTC - in response to Message 1646644.

The fact that time passes is universal. The means by which we measure that passage is entirely subjective and a product of our local situation. A day is the time it takes the earth to make one revolution on it's axis. A year is the amount of time it takes for earth to make one revolution around the sun. A light year is a measure of the distance light travels in an earth year. As long as we are the only intelligent beings that we know of, how time gets measured is totally dependant on how we choose to do it.

A day as we measure it for ordinary use is the time period between sun crossings of the north-south line (solar day). The actual one revolution on earth axis relative to the "fixed stars" is shorter, about 23 hours 54 minutes and 4 seconds (sidereal day). Rotation around the sun effectively removes one day, so there's one more day in the sidereal year.

That doesn't make much difference except for astronomical observations, but since that's what we're analyzing it is important to the science we are doing.
`                                                                   Joe`

I was aware of the technical definition of a day and a year. However, for the casual level of knowledge displayed by most members of this board I was trying to keep things as simple as possible. No matter what the technical definition is the measure of time is still a subjective value we assign to allow time to have meaning.
Bob DeWoody

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Gary Charpentier
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Message 1646734 - Posted: 26 Feb 2015, 2:27:32 UTC - in response to Message 1646720.

Now is what you and the distant observer agree is now. For two people standing a few feet apart, it is impossible to measure any difference, but there is one. For two GPS satellites the difference is measurable and you have to agree on a single reference frame to measure now. If you are just looking in a telescope, then the difference is the distance from your eye -- light years. If you are driving a robot on Mars, you picked a prime meridian on Mars and know the rotation rate of the planet so that noon happens when the sun transits the prime meridian and you correct for your longitude of your robot. If you mean what time is it on ET's planet, we and ET have to know how each keeps time on their home world and agree on a "now" -- likely the distance between the worlds -- and how each expresses the value of now, then a little math and you can convert times either way.

What might be a bit more interesting is talking to an ET 13 billion light years away and finding out what they measure the age of the universe as. Did it expand uniformly, did the expansion start at the same time .....

And last, if you are a photon, now is!
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Message 1647233 - Posted: 27 Feb 2015, 11:25:02 UTC - in response to Message 1647211.

As long as we are the only intelligent beings that we know of, how time gets measured is totally dependant on how we choose to do it.

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rob smith
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Message 1647400 - Posted: 27 Feb 2015, 19:16:39 UTC

There two "time" attributes to consider.
The first is the time interval, and the second the displayed time.
Displayed time is the time the observer sees, so look at your watch and, depending where on the planet you are, and the time zone you have opted your watch to be displaying it will read something like 19:11 (as my wrist watch does as I type).
The time interval is the rate at which this displayed time changes. We have defined this in terms of "seconds", which are defined in terms of number of oscillations of a particular atom under a very specific set of conditions.
While "wrist watch time" will vary, even on Earth, from location to location the interval time will remain constant.

(The forgoing assumes that neither the wrist watch nor the interval timer are moving at an appreciable fraction of the speed of light - appreciable in this case is probably much less than 0.1%c, in which case corrects for our friend Einstein have to be made...
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Message 1647421 - Posted: 27 Feb 2015, 19:59:09 UTC - in response to Message 1647233.

As long as we are the only intelligent beings that we know of, how time gets measured is totally dependant on how we choose to do it.

The above clock tells Universal Spacetime in the most illuminating way humans can understand. Not a clock is more precise than the above. At the risk of sounding AMORC'ish, I shall stop now:))
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Julie
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Message 1647437 - Posted: 27 Feb 2015, 20:32:36 UTC - in response to Message 1647421.

As long as we are the only intelligent beings that we know of, how time gets measured is totally dependant on how we choose to do it.

The above clock tells Universal Spacetime in the most illuminating way humans can understand. Not a clock is more precise than the above. At the risk of sounding AMORC'ish, I shall stop now:))

We do have the numbers 8 and 9 but they are too hard to comprehend.. Mathematics is the language of the Universe, nuff said..
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Message 1648431 - Posted: 2 Mar 2015, 7:55:45 UTC - in response to Message 1647426.

We have defined this in terms of "seconds", which are defined in terms of number of oscillations of a particular atom under a very specific set of conditions.

The second is the duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium 133 atom.

That's all very well for the scientists and geeks amongst us. When ET lands the rest of the world will talk basic day to day stuff to them. As in, look Mr ET

Our planet revolves on it's axis during which time we call one day.
We divide that day into 24 bits called hours.
We divide those hours into 60 bits called minutes
We further divide those minutes into 60 bits called seconds.

Our planet orbits our star during which time we call one year.
We divide that into 365 bits called days referred to above.
But we have to have a correction every 4 years, sorry about that. Not a leap forward really.

Now still with me? OK.

We divide this year above into 12 bits called months
But each month has a different number of days.
Yeah we know, but a couple of guys in the past had ego trips.

Look mate, it's opening time, let your geeks talk to our geeks, keeps 'em off street corners. Sorry we're out of Romulan Ale, London Pride do at a pinch?

Why didn't you divide one revolution of the planet into 13 eqaul parts? Like the Moon orbits Earth 13 times in a one Earth revolution, every 28 days...

How would you respond to ET? ;)

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Message 1648479 - Posted: 2 Mar 2015, 13:17:39 UTC - in response to Message 1644783.

I am trying to understand what the time difference between starts and their respective plants.

For example, Lets assume that right now it's 6:00 PM "Earth Time" throughout the entire planet. In fact lets say there is only 1 time zone for all of earth.

What time would it be on mars?
What time would it be on Jupiter?
What time would it be on Pluto? (yes I know it got fired)

Now assuming my question wasn't entirely stupid, what time would it be:

On Sirius?
On any planets who "orbit" Sirius?

I am trying to figure out what the change in time is relative to the start itself.

Thanks

Robert

I would recommend to read corresponding chapter of this book: Roger Penrose. Â«The Emperor's New MindÂ»

It describes quite visually how time depends on velocity of observer. For galaxy-scale ranges (that is, event occurs in another galaxy from us) "simultaneity" will be different even for 2 mans walking towards each other.
In any case the sense of simultaneity is very abstract for Ð¿Ñ€Ð¾ÑÑ‚Ñ€Ð°Ð½ÑÑ‚Ð²ÐµÐ½Ð½Ð¾-Ð¿Ð¾Ð´Ð¾Ð±Ð½Ñ‹Ð¹ interval.

EDIT: Even Wiki page illustrates it well enough: https://en.wikipedia.org/wiki/Relativity_of_simultaneity

EDIT2: Actually, Wiki has all needed parts:
people pass each other on the street; and according to one of the two people, an Andromedean space fleet has already set off on its journey, while to the other, the decision as to whether or not the journey will actually take place has not yet been made. How can there still be some uncertainty as to the outcome of that decision? If to either person the decision has already been made, then surely there cannot be any uncertainty. The launching of the space fleet is an inevitability. In fact neither of the people can yet know of the launching of the space fleet. They can know only later, when telescopic observations from earth reveal that the fleet is indeed on its way. Then they can hark back to that chance encounter, and come to the conclusion that at that time, according to one of them, the decision lay in the uncertain future, while to the other, it lay in the certain past. Was there then any uncertainty about that future? Or was the future of both people already "fixed"?

â€”Roger Penrose, The Emperor's New Mind: Concerning Computers, Minds, and the Laws of Physics

https://en.wikipedia.org/wiki/Rietdijk%E2%80%93Putnam_argument
But I would recommend to read the original book though, there is lot interesting, much more than just this single time relativity illustration.
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Message 1648487 - Posted: 2 Mar 2015, 13:56:25 UTC - in response to Message 1648479.

I have read it, but also read the following book, "Shadows of the mind". I've had an exchange of letters with Penrose, a very kind person to answer a letter by an unknown person who was bold enough to send him an unpublished text for his judgment. He then advised me to read "Shadows of the mind".
Tullio
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Bob DeWoody

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Message 1648543 - Posted: 2 Mar 2015, 19:06:29 UTC - in response to Message 1646543.

Perhaps we should try Stardates ....

Star Trek

Chris, I know you were joking here. Star Trek totally ignored the problems of "spacetime" thru the use of a medium called subspace. Otherwise stardates would make no sense at all. Only on Star Trek could a starship leave earth for a two week voyage and return to earth with the same amount of time passing both on the starship and on mother earth.

Unfortunately that is one aspect of long distance space travel that most people don't grasp the reality of. A long duration space flight at near light speed would, for example, only take a couple years from the point of view of the crew while back on earth a much longer span of time, probably decades, will have passed. Meaning a returning crew would find a totally different earth situation and hopefully a new population to deal with.

In other words, space travel like we have seen in popular Sci Fi movies and TV isn't going to happen......EVER.
Bob DeWoody

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