Astronomy without a telescope -- time freeze

January 24, 2011 By Steve Nerlich, Universe Today

Astronomy without a telescope -- time freeze

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Is it ever possible to find yourself in a situation where you see the hands of a clock freeze? Nnnnnnnnnn...

There is a story told about traveling at the speed of light in which you are asked to imagine that you begin by standing in front of a big clock – like Big Ben. You realize that your current perception of time is being informed by light reflected off the face of the clock – which is telling you it’s 12:00. So if you then shoot away at the same speed as that light – all you will continue to see is that clock fixed at 12:00, since you are moving at the same speed that this information is moving. And so you discover that at the speed of light, time essentially stands still.

While there are a number of things wrong with this story – as it happens, one correct thing is that if you were able to travel at the speed of you would experience no passage of time – although there are several reasons why this is probably an impossible situation to find yourself in.

But nonetheless, if you were able to travel at light speed and not experience the passage of time – then you would have no time available to reassess your situation – indeed there would be no time available for your neurons to fire. So, you might well leave Earth with the image of the fixed on your retina, but since your brain has stopped working, this has nothing to do with the information carried in the light beam you are moving along with. Your retina is never refreshed with a new image as long as you stay at the speed of light.

Some insight into special relativity is gained by considering the context of someone who stayed back on Earth. If your light speed trip was aimed at a mirror at Alpha Centauri (4.3 light years away) – then from their perspective, it takes you 8.6 years to go there and bounce back. This is true even though you leave and return with an image of 12:00 stuck on your retina and rightly announce that (from your perspective) no time has passed since your departure.

But moving at light speed and experiencing no passage of time is probably an impossible scenario for we mass-challenged beings. Relativity has it that you possess a proper mass, a proper length and a proper time – which persist regardless of your velocity. If you could survive the G forces to get up to such speeds, then you could happily coast at 99.95% of the speed of light and check your pulse against your watch to find your heart still beating at 72 beats per minute – just like it did back on Earth.

Astronomy without a telescope -- time freeze
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At speeds of less than 10% of the speed of light (0.1c or 30,000 km/sec) time dilation is miniscule, but from 99% speed of light up it increases asymptotically towards infinite.

It’s only when you check back with Earth that you see that something remarkable is happening. Moving at 99.5% of the speed of light gives you a factor of around 10. So while someone back on Earth will still measure your trip duration at about 8.6 years – for you it will only be around 10 months. And with a remarkably good telescope you might look back to Earth and see a distorted Big Ben, red-shifted and running slow on the way there and then blue-shifted and running very fast on the way back.

One of the reasons that probably makes the experience of /time freeze unobtainable is that time dilation keeps increasing the faster you move, For example, at a speed of 99.99995% of the speed of light you get a time dilation factor of about 1,000. So even if you have a spacecraft with an infinite power source capable of seemingly infinite velocities – you will keep arriving at your destination before your speedometer makes it all the way from 99.99999(etc)% of the to c = 1.0.

This is perhaps how we will populate the universe – using difficult-to-imagine investments of energy, coupled with the principle of time dilation to cross vast distances. The trick is not to get homesick, because after covering such distances you can never go back – unless it is to meet your very, very, very great grandchildren.

(I have cheated a bit by ignoring any periods of acceleration and deceleration within the journeys described here).

More information: Relativity calculator

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StandingBear
Jan 24, 2011

Rank: 1 / 5 (5)
The universe is a cacophony of heteroginicity moving randomly relative to all its parts in all six degrees of spatial freedom. Now propose that we have time dilation? But wait! Suppose that time has dimensionality as well; maybe even higher dimensionality!? Of course with that there is no possibility of causality violation if one formulates a new Pauli Principle of quantum temporal physics to match cartesian spatial physics..no direct quantum temporal congruent backtrackin past the point of quantum temporal origin. Schroedinger's cat is again safe..for now; as are grandfathers from their ingrate grandchildren. However one digresses, there will always exist somewhere some particle pair connected by an imaginary skewline in visible space that has an apparent rate of length change greater than ...300,000kM/sec. It is just common sense!
vacuum-mechanics
Jan 24, 2011

Rank: not rated yet
Beside mathematical description, could anyone explain,what is the mechanism of the time dilation?
soulman
Jan 24, 2011

Rank: 1 / 5 (2)
Beside mathematical description, could anyone explain,what is the mechanism of the time dilation?

Sorry, there's no real answer to that - it's just the way things are. Mathematics is used to describe what's observed (Minkowski spacetime defined by the Lorentz transformation).

SDrapak
Jan 24, 2011

Rank: not rated yet
I don't believe this is correct. From the frame of reference of the clock time would not pass for you, but the only reliable frame of reference is yourself. It would also not be possible to return to the clock without reversing the effect on the way back.
There would be an infinite number of external references, all moving at different relative velocities to yourself. Your brain wouldn't stop just by choosing to view one of them directly behind you, you just wouldn't get any new light from it.
The light would essentially be red-shifted to zero - since it's stationary (zero frequency) you may not see anything except black.
nuge
Jan 25, 2011

Rank: 4 / 5 (2)
Beside mathematical description, could anyone explain,what is the mechanism of the time dilation?


Well, it was originally decided that this all happens in an effort to make sure light speed is always the same, whether you are travelling parallel to it or anti-parallel to it, because Maxwell's equations give only one velocity for electromagnetic waves. Length contraction and time dilation are needed to explain how that could possibly be true. It is hard to wrap your head around, but that is what Einstein did and that it why he is so revered.
DavidMcC
Jan 25, 2011

Rank: not rated yet
Why not just use a wrist-watch? It would save all this trouble!
ODesign
Jan 25, 2011

Rank: not rated yet
It seems to me from a travelers point of view very little time would pass but several light years distance would be covered. So from the perspective of someone traveling they would be going faster than the speed of light because time would slow.

-is this correct?
Glyndwr
Jan 25, 2011

Rank: not rated yet
'The trick is not to get homesick, because after covering such distances you can never go back – unless it is to meet your very, very, very great grandchildren.'

They always end on quaint little tidbits like this..............by the time we can travel near lightspeed.....aging may well be cured easily. If the universe is built around maths.....ANYTHING WHICH SEEMS IMPROBABLE IS POSSIBLE ;) (glass half full here) XD
GoodElf
Jan 25, 2011

Rank: not rated yet
Hi SDrapak,
From the frame of reference of the clock time would not pass for you, but the only reliable frame of reference is yourself. It would also not be possible to return to the clock without reversing the effect on the way back

Not so... time is a scalar not a vector. There is no going back in time (using Relativity). The analogy of image on retina is good. You "are" your nerve impulses.

Your brain wouldn't stop just by choosing to view one of them directly behind you, you just wouldn't get any new light from it.
The light would essentially be red-shifted to zero - since it's stationary (zero frequency) you may not see anything except black.

You "experience" nothing between those "ticks" of a clock. A "redshift" would only be "seen" while you were traveling near the speed of light - for almost "zero" of your time. Time appears "seamless" to the traveler and the suspension in time is observed only by "external observers". It's all "relative" you see!
ubavontuba
Jan 25, 2011

Rank: 3 / 5 (4)
Sorry, there's no real answer to that - it's just the way things are. Mathematics is used to describe what's observed (Minkowski spacetime defined by the Lorentz transformation).
That's a cop-out.

The lay explanation is:

In special and general relativity, time dilation is a property of space having to do with the speed of light and different observers' points of view. That is, in order for all observers to see the speed of light as a constant, their clocks cannot agree. Hence: time dilation.

Time is also part of the topology of space. Hence: "spacetime."
soulman
Jan 26, 2011

Rank: 3 / 5 (2)
Sorry, there's no real answer to that - it's just the way things are. Mathematics is used to describe what's observed (Minkowski spacetime defined by the Lorentz transformation).
That's a cop-out.

The lay explanation is:

In special and general relativity, time dilation is a property of space having to do with the speed of light and different observers' points of view. That is, in order for all observers to see the speed of light as a constant, their clocks cannot agree. Hence: time dilation.

Time is also part of the topology of space. Hence: "spacetime."

Dude, you've just used up a whole bunch of words to say what I encapsulated in three or four. But crucially, you still haven't explained the underlying *mechanism* at work, as origionally asked.
ubavontuba
Jan 26, 2011

Rank: 2 / 5 (4)
Dude, you've just used up a whole bunch of words to say what I encapsulated in three or four.
But your words were not exactly descriptive, and you fell back on to the very mathematical concepts which the questioner sought to avoid.
But crucially, you still haven't explained the underlying *mechanism* at work, as originally asked.
Yes I did. The "mechanism" is that the speed of light must be constant to all observers.
soulman
Jan 26, 2011

Rank: 3.7 / 5 (3)
Yes I did. The "mechanism" is that the speed of light must be constant to all observers.

No, you did not. The mechanism is the underlying reason why the phenomenon happens. It's like asking why does the speed of light have the value that it does? No one knows - it just does. Best we can do is describe it mathematically.
ubavontuba
Jan 26, 2011

Rank: 1 / 5 (1)
No, you did not. The mechanism is the underlying reason why the phenomenon happens. It's like asking why does the speed of light have the value that it does? No one knows - it just does. Best we can do is describe it mathematically.
He didn't ask why the speed of light is a constant, now did he? He asked about time dilation. The cause of time dilation is that the speed of light must be constant to all observers.
soulman
Jan 26, 2011

Rank: 3.7 / 5 (3)
He didn't ask why the speed of light is a constant, now did he?

Your reading comprehension skills also seem to be faulty.
ubavontuba
Jan 26, 2011

Rank: 1 / 5 (1)
Your reading comprehension skills also seem to be faulty.
Well, let's check this hypothesis.

The question was:
Beside mathematical description, could anyone explain,what is the mechanism of the time dilation?
Hmm. I don't see anything in there about the speed of light. Is it written in invisible text that only you can see, perhaps?
soulman
Jan 26, 2011

Rank: 3.7 / 5 (3)
Hmm. I don't see anything in there about the speed of light. Is it written in invisible text that only you can see, perhaps?

You still don't get it. My speed of light reference was just a simile so that you might better understand what the questioner meant by 'mechanism'.
ubavontuba
Jan 26, 2011

Rank: 1 / 5 (1)
You still don't get it. My speed of light reference was just a simile so that you might better understand what the questioner meant by 'mechanism'.
Oh, so now you're claiming to read minds? Or, perhaps you're being just a bit presumptuous?

I answered the question that was asked. No more, no less. You're just annoyed with your own shortcomings (in this regard) and you're taking it out on me.
vacuum-mechanics
Jan 26, 2011

Rank: 5 / 5 (1)
What is the physical mechanism in which the constant speed of light make the time dilate?
soulman
Jan 26, 2011

Rank: 3 / 5 (4)
I answered the question that was asked. No more, no less.

You did not and you're too blind to see it.
You're just annoyed with your own shortcomings (in this regard) and you're taking it out on me.

That's not it at all. I've said all that needs to be said and I see no need to keep flogging a dead horse, so I'm out (for now).
ubavontuba
Jan 26, 2011

Rank: 1 / 5 (1)
What is the physical mechanism in which the constant speed of light make the time dilate?

Cute! I love it! Did soulman put you up to it?

Anyway, the short answer is rather circular: Light makes time dilate so you observe light speed as a constant.

A longer answer is:

If time was constant, or neither time nor light speed were constant, you could hypothetically travel faster than light and you'd run into problems of causality (cause and effect).

Here's some "light" reading on it (pun intended):

http:/en.wikipedia.org/wiki/Special_relativity#Causality_and_prohibition_of_motion_faster_than_light

And:

http:/en.wikipedia.org/wiki/Time_dilation

Enjoy!

ubavontuba
Jan 26, 2011

Rank: 1 / 5 (1)
You did not and you're too blind to see it.
Well, I checked this hypothesis, and it didn't hold up. The light speed constant was not directly a part of the question. So you're going to have explain your contention more thoroughly.

That's not it at all. I've said all that needs to be said and I see no need to keep flogging a dead horse, so I'm out (for now).
Okay, me too. Goodnight.
Wulfgar
Jan 26, 2011

Rank: not rated yet
So if you're travelling 99.5% the speed of light, your travel will take a little longer from the point of view of earthlings than it would for light to go to the star and come back, right? (discounting the practicalities of acceleration and deceleration). What I don't understand is how if you go faster and faster than 99.5% and approach the speed of light without achieving it, time dilation increases, which means what people on earth see your voyage taking INCREASINGLY more time than it would take for light to bridge the same distance, no?
Wulfgar
Jan 26, 2011

Rank: 1 / 5 (1)
Time from what I've read, is fuzzy in its definition and an oscillating atomic clock has a different kind of relationship to time than macroscopic things that we are familiar with such as mountains and people. The arrow of time does not apply to the very small, as I understand it. If their relationship to time is different, then what can be said ultimately about the universality of time dilation? Have we ever seen anything that isn't a particle travel at highly relativistic speed such that we could see if, say, a bowl of soup spoils more slowly traveling at 50% of C, than it should? I know we compare atomic clocks and see relativistic particle lifetimes grow in particle accelerators, but what of the macroscopic? I know we see cosmic objects traveling at such speeds but I'm not sure if that applies. Not saying I doubt the physics, far from it. I'm just curious.
AmritSorli
Jan 29, 2011

Rank: 1 / 5 (1)
Light does not move in a space-time. According to the formalism X4 = ict cosmic space is 4D and time t is a numerical order of photon motion. Clocks run in a space only and not in time. With clocks we measure numerical order of change in 4D space. Experiments with clocks confirm clocks run slower on the fast airplane than on the surface of the earth. So "relative" is speed of clocks and not time. Time is merely a numerical order of a clock motion.
Moebius
Jan 30, 2011

Rank: 1 / 5 (1)
Beside mathematical description, could anyone explain,what is the mechanism of the time dilation?


The mechanism is that we use physical processes to perceive time, firing of neurons and chemical reactions. All of that stuff slows down as the speed of light is approached. If it is a wind up clock the springs transfer energy slower, if it is an atomic clock, particles move slower.

If you are asking about the underlying mechanism that causes that, physicists have an answer. Don't take it as gospel though, it's probably wrong but they will swear up and down it isn't until a better theory comes along, and rate any posts that question that gospel down too. If Einstein had posted his theories here before publishing them, they would have gotten one's from all the physicists here.

If you were a non-corporeal entity like the accepted definition of a soul, not made of matter or energy or anything that we know of, you would not experience time dilation due to velocity.
Rank 4 /5 (9 votes)
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