Here's a brain teaser.

Suppose you are on a trip to the nearest star and are traveling at an appreciable percent of the speed of light, say about 50%,. How would you keep track of Earth time ??

Would it be possible ??

I am still not happy with Martins definition of time. He seems to insist that it has always has something to do with motion. I can leave a book on a table, and start a stopwatch beside it. Some interval later I can stop the stopwatch and remove the book.

In neither case did the book or the stopwatch move, only the hands of it. If an electronic stopwatch, then just the digits would be changing. What the stopwatch shows is the elapsed period between me leaving the book there and me retrieving it. The units that we choose to measure the elapse between the two events are arbitrary. For want of a better word we use time to describe this elapse between the two events.

We also know that a device to record these durations which we call time, will record slightly differently whether it is motion itself or not. Clocks on the ISS will run slightly slower than on earth because of relativistic effects of it's motion relative to earth and time dilation, predicted by Einstein in 1905.

Time is time is time. It is the same stuff everywhere, this stuff just elapses slower in some circumstances from the respect of different observers. It's like a runner in a 100 metres race, it's the same runner no matter how fast they complete the event.

+1 I've seen interviews on "Beyond the Wormhole" where some theoretical physicists debate the nature of time, even to the point where a few say time doesn't exist. But from our viewpoint it sure does and as you get older it passes much too quickly.

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Bob DeWoody

My motto: Never do today what you can put off until tomorrow as it may not be required. This no longer applies in light of current events.

+1 I've seen interviews on "Beyond the Wormhole" where some theoretical physicists debate the nature of time, even to the point where a few say time doesn't exist. But from our viewpoint it sure does and as you get older it passes much too quickly.

Getting older is age and is totally related to the deterioration of cells. It has nothing to do with "time". We just think it does.

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Try this:

Time is the interval between two events in our life experience. It is measured by yet another multiple or fraction of intervals of occurrence of repeatable events in out life experience.

Once again, thanks for all of the insightful comments on this thread, I really enjoy reading them. So it seems that once we leave Earth’s orbit we will need a new way to measure the passage of time. Now if we stayed in communication with Earth and we needed to know how long we have been in space,we could just ask mission control on Earth and they would say that we are three Earth day’s out, but that would really only apply to Earth’s time. The crew on the spaceship would have no way to measure the passage of time. This is just a lark and maybe a bad joke but remember watching Star Trek, they always give the date, StarDate 176.8 or something like that. I guess we will just have to wait until the first Enterprise Starship is launched to find out just what the hell that means, or when we meet our first Aliens and ask them how they do it. Just a little try at some humor that probably missed.

Once again, thanks for all of the insightful comments on this thread, I really enjoy reading them. So it seems that once we leave Earth’s orbit we will need a new way to measure the passage of time. Now if we stayed in communication with Earth and we needed to know how long we have been in space,we could just ask mission control on Earth and they would say that we are three Earth day’s out, but that would really only apply to Earth’s time. The crew on the spaceship would have no way to measure the passage of time. This is just a lark and maybe a bad joke but remember watching Star Trek, they always give the date, StarDate 176.8 or something like that. I guess we will just have to wait until the first Enterprise Starship is launched to find out just what the hell that means, or when we meet our first Aliens and ask them how they do it. Just a little try at some humor that probably missed.

Computers are very capable of keeping time when away from earth. That's also how they did it on Star Trek. Clocks will still work perfectly well in space. They may appear to run faster or slower depending on the observer's point of view. But to members of the spacecraft's crew the clocks will appear to run at a normal rate.

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Bob DeWoody

My motto: Never do today what you can put off until tomorrow as it may not be required. This no longer applies in light of current events.

+1 I've seen interviews on "Beyond the Wormhole" where some theoretical physicists debate the nature of time, even to the point where a few say time doesn't exist. But from our viewpoint it sure does and as you get older it passes much too quickly.

Getting older is age and is totally related to the deterioration of cells. It has nothing to do with "time". We just think it does.

You missed my point entirely. Believe me I know what aging is and what causes it.

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Bob DeWoody

My motto: Never do today what you can put off until tomorrow as it may not be required. This no longer applies in light of current events.

Computers are very capable of keeping time when away from earth. That's also how they did it on Star Trek. Clocks will still work perfectly well in space. They may appear to run faster or slower depending on the observer's point of view. But to members of the spacecraft's crew the clocks will appear to run at a normal rate.

Bob is correct. However a question. Enterprise was regularly traveling at Warp 7 or 8 speeds which were faster than light Warp speeds. After its 5 year mission it returned to Earth where Kirk was made an Admiral. How much had those on earth aged in relation to the crew and how did they cover it in the story?

They totally ignored time dilation. Whatever amount of time passed on the Enterprise was the same as what passed on earth. The same is true of most sci-fi space travel. That is why most people have no concept of what time dilation is and don't realise that travelling to the stars means never seeing your loved ones at home again.

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Bob DeWoody

My motto: Never do today what you can put off until tomorrow as it may not be required. This no longer applies in light of current events.

Bob is correct. However a question. Enterprise was regularly traveling at Warp 7 or 8 speeds which were faster than light Warp speeds. After its 5 year mission it returned to Earth where Kirk was made an Admiral. How much had those on earth aged in relation to the crew and how did they cover it in the story?

They totally ignored time dilation. Whatever amount of time passed on the Enterprise was the same as what passed on earth. The same is true of most sci-fi space travel. That is why most people have no concept of what time dilation is and don't realise that travelling to the stars means never seeing your loved ones at home again.

Very true and the aspects of reality that are ignored on TV give an unfortunately powerful mal-education to the audience... Especially badly so to any audience unknowing of Science...

Star Trek was a very thoughtful adventure for its time, but also for its time it was badly constrained by costs and what could be done in production. Such as the futuristic ideas of the "transporter" and that of the warp speed of the ship itself were at the time merely plot devices to allow for a change scene. Only much later did ideas about such devices form part of the story for themselves.


Including time dilation effects into the story gives a very different perspective for developments, as explored by:

The Forever War


Keep searchin',
Martin

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But to members of the spacecraft's crew the clocks will appear to run at a normal rate.

I don't think that that is the case. First we must define NORMAL--presumably Earth Time at sea Level. In the absence of Gravity the clock would not run at the same time. Regardless of the form of the clock.

What do you all think ??

... First we must define NORMAL--presumably Earth Time at sea Level. In the absence of Gravity the clock would not run at the same time. Regardless of the form of the clock.

What do you all think ??

What is 'special' about Earth and sea level on Earth as some special point in the universe?


Keep searchin',
Martin

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See new freedom: Mageia Linux
Take a look for yourself: Linux Format
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time is passing everywhere, every circumstances, at same pace.(only the clocks devices arent as accurate)

i think nobody proved the speed of light dilation yet, no (it s ONLY a theory)

Using your assumption, then GPS ("satnav") simply does not work.

For much more extreme examples, just ask the good people at CERN for their super-long-lived particles whizzing around and through the Large Hadron Collider.


And... Lots of other examples that are directly observed.


By the boring reality of "Science Learnin'" and observation, our best and most accurate explanation is that time is indeed "relative" to whatever your "frame of reference" is for "experiencing" time.

For a very direct experiment and example: There is the twin clocks experiment that was run whereby identical clocks were used to compare their time for one clock staying on terra-firma whilst the second clock was flown around the world... Would you like to guess their times?


Keep searchin',
Martin

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The ISS clock does run slow: About 0.0000000014% slower than one on earth.

Yes but time would also slow at the same rate for an observer on the ISS. That is why I stated that for a space traveller the clocks would appear to run at their normal rate. Our minds can't detect that infinitesimal change in speed that would occur.

It is a sobering thought that space travel for the foreseeable future will be limited to the confines of our solar system. It will take a radical breakthrough and change of the known laws of physics or planning on one way trips for us to visit other star systems.

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Bob DeWoody

My motto: Never do today what you can put off until tomorrow as it may not be required. This no longer applies in light of current events.

It will take a radical breakthrough and change of the known laws of physics or planning on one way trips for us to visit other star systems.

A slingshot around the sun could accelerate a space craft towards the stars but the journey would take more than a human lifespan to complete. I am still convinced we can travel faster than light, we just don't know how yet.

Notice, I didn't rule that out. I too hope so. Knowing what we know now make space the biggest tease of all time.

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Bob DeWoody

My motto: Never do today what you can put off until tomorrow as it may not be required. This no longer applies in light of current events.

The ISS clock does run slow: About 0.0000000014% slower than one on earth.

Yes but time would also slow at the same rate for an observer on the ISS. That is why I stated that for a space traveller the clocks would appear to run at their normal rate. Our minds can't detect that infinitesimal change in speed that would occur.

For the example on the ISS, there is nothing "different about time" for your mind to notice. One second is still exactly one second for you and your body and your mind and perceptions.

What you will see if given suitably accurate measurement, is that for you on the ISS, everything on earth appears to speed along that same 0.0000000014% faster.

It is a sobering thought that space travel for the foreseeable future will be limited to the confines of our solar system. It will take a radical breakthrough and change of the known laws of physics or planning on one way trips for us to visit other star systems.

See: The Forever War.

Or see what Science might discover about alternate ways and means to go beyond our solar system... It's only a question of time... ;-)


Keep searchin',
Martin

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See new freedom: Mageia Linux
Take a look for yourself: Linux Format
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... that's what i said...

We're trying to say that the time 'experienced' by an object as viewed by someone depends on the strength of the gravitational field, AND also by the motion relative to the observer.

Are you agreeing with that? Or something else?

... just standing in the air, and NOT moving at all

Levitation?! ;-)


Keep searchin',
Martin

---

See new freedom: Mageia Linux
Take a look for yourself: Linux Format
The Future is what We all make IT (GPLv3)

The time dilation is a consequence of mathematics and was proven by Lorentz at first and by thousands of other Physics graduate students including my self. At Princeton a clock at the top of the bell tower ran differently than an identical one in the basement. The difference was small but due to a small change in gravity which follows Newton's laws strangely enough.

Also: a clock flying in an airliner from East to West kept different time than one flying West to East. One direction added the speed of the rotation of the Earth. These are the facts. Time does not flow uniformly as Newton once wrote,

Actually it's the difference in the effects of gravity at different distances from the center of the earth's mass. Gravity is what causes space/time to stretch and bend.

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Bob DeWoody

My motto: Never do today what you can put off until tomorrow as it may not be required. This no longer applies in light of current events.

Actually it's the difference in the effects of gravity at different distances from the center of the earth's mass. Gravity is what causes space/time to stretch and bend.

i agree only with the first part :)

454 feet distance is still 454 feet whatever if we have 1g or 2-3g

i believe if i fly at 300mph 3.2 sec long or at 300mps 3.2 sec long cause gravity ... it s still 3.2 sec long. just the speed change cause the gravity :P

The particular advantage of the theory of General Relativity is that it explains, at a stroke, all the observed properties of gravity. For example the fact that it acts equally on all objects and substances becomes obvious when you think of gravity as a distortion of space-time rather than a force. as you pass through time, the distortion of space-time caused by the presence of the earth accelerates your body towards the centre of the earth. However, when your feet are touching the ground, the ground exerts a force on your feet in an upwards direction which pushes you in the opposite direction. In other words you are being accelerated upwards with respect to space-time by the force of the ground acting on your feet. It is exactly the same as the force which seems to push you back in your car seat when you accelerate, what is really happening is that the seat is pushing you forwards.

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Mass is what causes space to warp. There is no "Gravity" as we usually think of it--it's just that objects want to be in their lowest energy state.