Post by: thedoc on 23/09/2016 14:23:02
If I move backwards at the speed of light (bear with me here) and turned on a torch, what would happen to the start of the beam of light? Would it be a glow frozen in one place? Would stationary bystanders be able to see a terminating light source, dangling in the air/space/whatever?
What do you think?
Post by: Zer0 on 17/11/2017 02:03:01
Considering B is the point you stand still with your torch.
You move from B towards A, backwards holding the torch.
Light beam from the torch moves from B to C forwards.
If I am Observing you from a distant point, I would see you moving from B to A at the speed of light, and a light beam moving from B to C at the speed of light.
Although I might be totally wrong, and if you would observe any redshift/blueshift from your point of observation is still unclear to me.
I've read about a Theory/Law that irrespective of the Observers point of Observation or Velocity, the observed speed of light would remain the same.
But Honestly, I haven't understood this completely as yet.
Although nothing to worry about, cause we are at the right place where all questions regardless of how stupid they sound or how meaningless they look, they will be answered with due importance in the right manner.
P.S. - (Apologies to Luke Pullar for the incredibly delayed response, how on earth did this question go unanswered is out of my perceptions.)
Post by: Kryptid on 17/11/2017 04:56:19
Post by: geordief on 17/11/2017 11:39:52
If it (the source) is moving at any other speed its frequency and wavelength will be altered
So if the flashlight is retreating from the observer at a speed close
to the speed of light it will appear to that observer as very faint (red shifted) but with the same speed in a vacuum.
Post by: Colin2B on 17/11/2017 12:48:02
P.S. - (Apologies to Luke Pullar for the incredibly delayed response, how on earth did this question go unanswered is out of my perceptions.)Very easy. If there are lots of posts at a particular time it doesn’t take long for a question to disappear off the page and get missed.
Yes, extreme Redshift will occur close to light speed.
Why does speed of light remain constant for all observers? The roots of this go back to electromagnetic theories of Faraday, Amper, Gauss and Coulomb but was never recognised until Maxwell did his famous equations and even he didn’t really understand the full implications. I’m afraid you will need to dig into these equations in order to understand.
Post by: elidaesilva on 17/11/2017 15:04:15
Quote
The source of light cannot move at the speed of light in a vacuum.That makes sense. All object will fail to gain light speed. Light does not have resistance but other object have.
If it (the source) is moving at any other speed its frequency and wavelength will be altered
So if the flashlight is retreating from the observer at a speed close
to the speed of light it will appear to that observer as very faint (red shifted) but with the same speed in a vacuum.
Post by: Zer0 on 17/11/2017 15:46:34
@P.S. - (Apologies to Luke Pullar for the incredibly delayed response, how on earth did this question go unanswered is out of my perceptions.)(1) Very easy. If there are lots of posts at a particular time it doesn’t take long for a question to disappear off the page and get missed.
(2) Yes, extreme Redshift will occur close to light speed.
(3) Why does speed of light remain constant for all observers? The roots of this go back to electromagnetic theories of Faraday, Amper, Gauss and Coulomb but was never recognised until Maxwell did his famous equations and even he didn’t really understand the full implications. I’m afraid you will need to dig into these equations in order to understand.
(1) Yes I understand out of sight is out of mind.
I'm a Newbee n learning how this forum works, but I've realized that before posting a question/op it helps to use the Search Option n look for keywords/tags n check if a same/similar question was asked before n then take it forward from there. 👍
In fact I would also recommend newbies/newcomers to just browse through Page 1 2 3 4 etc and explore multiple pages as there are a lot of hidden treasures to be found. 👌
(2) Thanks for the feedback. ✌
(3) Looks like I'm gonna be doing a lot of reading now, surely its going to take me a whole day to come to speed.
But I'm ready as always with my shovel of curiosity not afraid to dig deep into the ground of knowledge going where a lot of great men n women have gone before. 👊
Post by: Zer0 on 17/11/2017 16:03:30
A--------------------B
Total distance from A to B - 1 light year.
I race with a beam of light, start point A n finish point B.
Both light beam n my velocity is same = speed of light.
Considering we start at the same time, both will require a year to reach finish point B.
Now...
(1) Who would win, me or the light beam or none/draw ?
(2) While I'm travelling parallel to the beam of light travelling in a straight line, what would I observe red/blue/white/black ?
(3) Irrespective of my velocity which is the speed of light, will I still calculate the light beam travelling at the speed of light ?
(Hopefully in a day or two I shall be in a position to comeback n answer theses questions, until then any/all opinions/views are Welcome). 🙏
21st Nov 2017.
I'm back, a bit wiser than before I would say...
" You cannot travel at the Speed of Light. " Thanks for the Info geordief 👍
(1) Irrelevant. 👎
(2) Irrelevant. 👎
(3) Irrelevant. 👎
If anyone ever reached 50% speed of light, and tried to measure/calculate speed of light beam it would still be 'c' constant considering their clock/stopwatch would be ticking 50% slower. ⌚⏰
Light which is made of Photons have zero rest mass hence 'c'. If a particle or body with mass would try to match 'c' speed then it would require infinite energy/force cause as the mass body accelerates its mass would increase infinitely. 🚀
Light is often simply considered as the one visible to human eyes, but in fact it has a lot of unseen variants.
A bit of reading on ElectroMagnetic Radiation would help one to understand different variants such as xrays, gamma rays, infrared, micro n radio waves n so on and also provide explanations as to why they are different due to frequencies & wavelengths. 🍭💎
P.S. - (Yeah I travelled back in time n answered my own questions. Why? In order to Help a layman/newbie who one day might stumble upon this OP.) ✌
Thanks TNS for being such a time traveller friendly forum! 🙏
Post by: geordief on 17/11/2017 16:16:34
I race with a beam of light, start point A n finish point B.You cannot travel at the speed of light. :P :'( :o ;) :)
Both light beam n my velocity is same = speed of light.
No matter how close you come to the speed of light (as measured from your point of departure,as well as that of the beam of light) the beam of light ,if you were able to measure its speed would still be c .
The only difference would be its frequency .
Post by: Bill S on 17/11/2017 20:55:31
Quote from: Geordief
You cannot travel at the speed of light. :P :'( :o ;) :)
There are a few who argue against that, but I doubt they are taken seriously. However, is it only "experts" who are permitted to speculate about possible effects of doing so, without being shouted at?
Einstein did it with outstanding success, and J Richard Gott has a go.
In "Time Travel in Einstein’s Universe" he formulates an interesting argument under the heading “Why Rockets Can’t Go Faster than Light”. He says:
Quote
If an astronaut’s rocket were to travel by us at faster than the speed of light, a light beam he sent forward could never catch up with the front of his rocket. The light beam could never catch up because the front of the rocket would be moving faster and have a head start. Any athlete should know that catching another runner who is running faster and has a head start is impossible. The astronaut’s observations would be most peculiar: he would take out a flashlight and shine it towards the front of his rocket, but he would never see the beam of light arrive. That’s not what an observer at rest would see: rather than perceiving he was at rest, this astronaut would know he was moving, and that’s not allowed by the first postulate.
I find this interesting because he seems to be saying that the astronaut (in his/her RF) would not observe light as travelling at c.
Post by: geordief on 18/11/2017 02:41:16
Yes ,though I do think it is fair and prudent to leave speculations in the main to those who have mastered the essentials of the subject.
Which counts me out.
Post by: Bill S on 18/11/2017 13:17:29
Quote
Yes ,though I do think it is fair and prudent to leave speculations in the main to those who have mastered the essentials of the subject.
Which counts me out.
If you stop speculating, how do you know you are still alive? :)
Post by: geordief on 19/11/2017 02:56:30
If you stop speculating, how do you know you are still alive? :)We all speculate but only based on what we think we already think we know.
My own speculations would be of far less interest to another person than the speculations of someone with learned knowledge and experience.
If I speculate I can easily discover the truth by inquiring of someone who knows the subject ahead of me .
Post by: Bill S on 19/11/2017 13:49:49
Quote from: Geordief
My own speculations would be of far less interest to another person than the speculations of someone with learned knowledge and experience.
Not necessarily. Just because someone has a lot of knowledge in a particular area does not mean that he/she can always use that knowledge to the best advantage, or draw the "best" conclusions from it. Don't undervalue your own efforts.
I spent much of my early childhood deep in the Cornish countryside. I still retain "pearls" of wisdom that came from people who could hardly read or write. One of these was: "Never pretend to understand something you don't really understand: and never believe something unless you understand it". OK, one can pick holes in that, but it contributed to my being known as "What if", because I questioned everything. (Not aloud, if they happened to be my mother's edicts :) )
Post by: jeffreyH on 19/11/2017 15:44:12
Post by: Bill S on 19/11/2017 15:49:20
Quote from: Jeffrey
The gamma factor for an object travelling at c is infinite.
Please could you simplify that a bit (a lot :) )for me. It could be something I've been looking for.
Post by: jeffreyH on 19/11/2017 16:02:52
https://en.m.wikipedia.org/wiki/Lorentz_factor
Post by: jeffreyH on 19/11/2017 16:52:50
. When v = c the result of the function is infinite.
Post by: Bill S on 19/11/2017 17:28:00
Post by: jeffreyH on 19/11/2017 17:43:57
Post by: Bill S on 19/11/2017 17:55:52
Quote
No. I am saying the opposite. You cannot match or exceed c.
That's what I would have expected you to say. I must have misinterpreted #14 as saying something else. I think that arose because you said: "the object will experience no time or motion".
I'm still not clear as to whether you would propose this as a reason for saying that a photon doesn't "experience" time.
Post by: jeffreyH on 19/11/2017 18:05:46
Post by: Bill S on 20/11/2017 14:52:27
Quote
Time is irrelevant for a photon
I've followed several lines of reasoning on this subject, and I have to say that's the best "get out" I've met. I'll try to remember to reference you if I ever use it. :)
This just leaves the question as to whether, or not, the equations of SR can justifiably be extrapolated to "c".
Post by: Colin2B on 20/11/2017 15:03:44
It would be reasonable to say that certain values tend towards certain limits as speed tends towards c.
This just leaves the question as to whether, or not, the equations of SR can justifiably be extrapolated to "c".
Post by: Bill S on 20/11/2017 16:04:53
Quote from: Colin
It would be reasonable to say that certain values tend towards certain limits as speed tends towards c.
Are you trying to trump Jeffrey's get-out clause? :)
Post by: Colin2B on 20/11/2017 18:17:41
It’s not really a get out clause, it’s just the way things behave. ;)Quote from: ColinIt would be reasonable to say that certain values tend towards certain limits as speed tends towards c.
Are you trying to trump Jeffrey's get-out clause? :)
Post by: jeffreyH on 20/11/2017 18:26:05
Post by: Bill S on 20/11/2017 20:08:44
Quote from: Colin
It’s not really a get out clause, it’s just the way things behave.
I accept that; but the question was whether one could justify extrapolating SR to "c", rather than just an "infinitesimally" small distance away.
Quote from: Jeffrey
Just wait until I get deeper into quantum mechanics.
I look forward to hearing about your discoveries.
Post by: Janus on 20/11/2017 20:38:30
Quote from: ColinIt’s not really a get out clause, it’s just the way things behave.
I accept that; but the question was whether one could justify extrapolating SR to "c", rather than just an "infinitesimally" small distance away.
One cannot. For example the time dilation equation is
t = t`/sqrt(1-v2/c2)
if you try to make v=c, you end up with a division by zero which is undefined.
It is an asymptotic function with no solution for v=c
Post by: Bill S on 20/11/2017 20:51:30
So does that mean that we cannot know if something travelling at "c" "experiences time?
Post by: Colin2B on 20/11/2017 22:48:25
So does that mean that we cannot know if something travelling at "c" "experiences time?Absolutely :)
To have the capacity to experience implies (as currently understood) that the experiencer has mass.
Post by: Bill S on 20/11/2017 23:35:24
Quote from: Colin
To have the capacity to experience implies (as currently understood) that the experiencer has mass.
Thanks, a straight answer is always welcome.
Opinions are, as you are aware, quite sharply divided on the (speculative?) question of photons and time. I'd be interested to know where you stand on that; and why.
Post by: Colin2B on 21/11/2017 09:09:42
Opinions are, as you are aware, quite sharply divided on the (speculative?) question of photons and time. I'd be interested to know where you stand on that; and why.
Where I stand is as I stated:
It would be reasonable to say that certain values tend towards certain limits as speed tends towards c.
Or as @Janus put it in more detail:
It is an asymptotic function with no solution for v=c
The important fact, which has a solution, is that photons travel at c relative to us. This is measurable.
Post by: geordief on 21/11/2017 11:18:36
Can it also be viewed (in a different sense) as a limit when applied to massless particles?
I may well be wrong ,but it is the quantity from which all other measurements depend (are a function of).
If we we to take some other quantity as the benchmark would we find that the value we found for c would have to be expressed as a limit?
I also understand that c is a function of the permittivity and the permeability of a vacuum .Are there any conceivable circumstances where those quantities might vary?
Post by: Bill S on 21/11/2017 12:23:49
To me, your statement: "To have the capacity to experience implies (as currently understood) that the experiencer has mass." says something like:
Because nothing with mass can be accelerated to "c", and since we cannot reasonably attribute "experience" to a massless object, we have no way of knowing what the relationship between a massless object and time, as we measure it, would be.
Bear with an ill-informed, pedant, and tell me if I've got that right. :)
Post by: Colin2B on 21/11/2017 15:39:48
Bear with an ill-informed, pedant, and tell me if I've got that right. :)That’s pretty well it.
However, if we consider the photon from our reference frame we can say that the time dilation we measure would be extreme, so decay time (drawing a parallel with Muons) would be close to infinite - which, I assume, is why we don’t see photon energy as being distance dependent.
Post by: jeffreyH on 21/11/2017 17:13:29
Bear with an ill-informed, pedant, and tell me if I've got that right. :)That’s pretty well it.
However, if we consider the photon from our reference frame we can say that the time dilation we measure would be extreme, so decay time (drawing a parallel with Muons) would be close to infinite - which, I assume, is why we don’t see photon energy as being distance dependent.
All those who are actually here to learn read Colin's answer carefully. You will learn something very important about relativity and time.
Post by: Bill S on 21/11/2017 17:59:10
Quote from: Jeffrey
All those who are actually here to learn read Colin's answer carefully. You will learn something very important about relativity and time.
No doubt, everyone expects me to ask how you can be close to infinity; but that’s not for this thread.
There’s the bit about considering the photon from our reference frame. To me, that says that any practical measurement can only be made from our RF. We might theorise about how, it might look from some other RF. We might even construct a mathematical argument to back up our theory, but we can never actually place ourselves in a RF that would not be ours, once we were in it.
“…time dilation we measure would be extreme…” We can measure time dilation to a very high accuracy, but whatever the extremity we reach, there will always be a limit that stops short of “c”.
“…so decay time (drawing a parallel with Muons) would be close to infinite - which, I assume, is why we don’t see photon energy as being distance dependent.”
If by “infinite” we mean that it is so extreme that we cannot reasonably, distinguish between its value and infinity, then we would be faced with the possibility that at “c”, muons might not decay.
“…which, I assume, is why we don’t see photon energy as being distance dependent.”
If we apply the same principle to the photon, its energy would appear never to reach zero, in our RF, no matter how far, and for how long, it had travelled.
OK, Colin, what have I misinterpreted; Jeffrey, what have I missed?
Post by: jeffreyH on 21/11/2017 22:33:46
Quote from: JeffreyAll those who are actually here to learn read Colin's answer carefully. You will learn something very important about relativity and time.
No doubt, everyone expects me to ask how you can be close to infinity; but that’s not for this thread.
There’s the bit about considering the photon from our reference frame. To me, that says that any practical measurement can only be made from our RF. We might theorise about how, it might look from some other RF. We might even construct a mathematical argument to back up our theory, but we can never actually place ourselves in a RF that would not be ours, once we were in it.
“…time dilation we measure would be extreme…” We can measure time dilation to a very high accuracy, but whatever the extremity we reach, there will always be a limit that stops short of “c”.
“…so decay time (drawing a parallel with Muons) would be close to infinite - which, I assume, is why we don’t see photon energy as being distance dependent.”
If by “infinite” we mean that it is so extreme that we cannot reasonably, distinguish between its value and infinity, then we would be faced with the possibility that at “c”, muons might not decay.
“…which, I assume, is why we don’t see photon energy as being distance dependent.”
If we apply the same principle to the photon, its energy would appear never to reach zero, in our RF, no matter how far, and for how long, it had travelled.
OK, Colin, what have I misinterpreted; Jeffrey, what have I missed?
You have an excellent grasp of the idea.
Post by: Bill S on 21/11/2017 23:41:35
Post by: geordief on 21/11/2017 23:53:52
Is there such a concept as a potential internal structure of a photon that would be subject to change?
If any particle is massless does it necessarily lack an internal structure?
Post by: Bill S on 22/11/2017 00:29:28
Quote
If any particle is massless does it necessarily lack an internal structure?
That might depend on whether or not you consider things like frequency, amplitude and energy as internal attributes/structure.
Post by: geordief on 22/11/2017 01:16:14
That might depend on whether or not you consider things like frequency, amplitude and energy as internal attributes/structureI don't think that.I thought its(ie a photon's) energy came from its relationship to its environment.
I thought the frequency and amplitude were similarly a function of its relation to its environment.
So not internal.
I am not clear whether a proton is supposed to not experience proper time** or whether it is simply a question that cannot be asked (a bit like the singularity scenario(s?) which just seems to show that the present model has run out of road)
**no matter what speed a massive object travels at it is always said that it experiences the same proper time as any other object in any other FoR (1 sec per sec as it is put simplistically), but with light I get the feeling that this circumstance may no longer apply-unless I have misunderstood and all that is being said is that the question does not arise.
Post by: jeffreyH on 22/11/2017 12:49:27
In it's own inertial frame of reference nothing is happening.
Post by: geordief on 22/11/2017 15:35:24
If on the other hand you made a dash for it as it was a rainy day and similarly took a check of the news ,practically nothing would have(had time to have) happened.
Are we talking the same phenomenon , the faster you move the less happens over the course of your journey. With light the same happens ,but to an infinite degree.
Or is there a lot,lot more to it than that?Is that example even relevant and are these light related effects entirely relativistic
Post by: Bill S on 22/11/2017 15:49:48
Post by: Bill S on 22/11/2017 16:17:56
Quote from: Jeffrey
In a universe containing only one object with the only two states the object has are constant velocity and straight line motion and that is the only thing observable then how would the passage of time be marked?
In it's own inertial frame of reference nothing is happening.
Indeed, how would space or motion be measured.
I found this in my notes from a few years ago, when I was struggling with some basic ideas.
I remind others that I write my notes as though I were trying to explain a point to someone with even less knowledge than I might have, so anything that sounds patronising is not intended as such.
“Imagine you are in a space craft at the “centre” of an infinite, void. Nothingness stretches infinitely in every direction. You perceive yourself as being stationary, but suppose you engage your engine and travel at fractionally below light speed for five seconds, then stop. You review your position; are you 1,500,000 kilometres away from where you started? Is there now more nothingness behind you than there is in front? On reflection you conclude that there is still an infinity of nothingness in every direction. There is in fact nothing to which your motion can be relative. You have “moved”, but you are still in the same place - in the “centre” of an infinity of nothingness - your movement has no real meaning.
You can argue that if you use your engine to propel your craft forward you will be able to detect your motion, as you will be accelerating, and accelerated motion can be felt by the person doing the accelerating. Undoubtedly this is so, but as you had no way of telling if you were in motion or not before you engaged your engine, you cannot tell if you have moved off from a standstill, if you have simply increased the speed at which you were already travelling, or if you have decreased your speed; which would be the case if you had already been travelling “backwards” without being aware of that fact.
However, because no matter how far you move, you will still perceive yourself as being in the same place, the whole question of how far you might have travelled, and at what speed, is purely academic.”
Post by: Bill S on 22/11/2017 16:29:15
Quote from: Geordeif
is this time stopping thing as banal as the way ,if you went to the shops and took your time ,maybe dropping in at the Nag's Head and the bookie's and then glanced at your smartphone to catch up on the news you would see that by God that M'gabe F**er (and much more besides had also happened ) had resigned in the course of your journey.
If on the other hand you made a dash for it as it was a rainy day and similarly took a check of the news ,practically nothing would have(had time to have) happened.
Are we talking the same phenomenon , the faster you move the less happens over the course of your journey. With light the same happens ,but to an infinite degree.
Or is there a lot,lot more to it than that?Is that example even relevant and are these light related effects entirely relativistic
The distinction must be that, in your example, time has remained unchanged, you have simply experienced more of it in one scenario than in the other.
BTW, the whole idea of stopping time assumes that time is moving. This must mean that time is something in its own right. Could be safer to think in terms of our moving through time.
This introduces the ideas of “tensed” and “untensed” time. That’s fun. :)
Post by: Colin2B on 22/11/2017 18:11:43
Is this time stopping thing as banal as the way ,if you went to the shops and took your time ,maybe dropping in at the Nag's Head and the bookie's and then glanced at your smartphone to catch up on the news you would see that by God that M'gabe F**er (and much more besides had also happened ) had resigned in the course of your journey.What you are talking about here is the difference between perceptual time ie internal brain memory etc, and measured time ie clock time.
If on the other hand you made a dash for it as it was a rainy day and similarly took a check of the news ,practically nothing would have(had time to have) happened.
Are we talking the same phenomenon , the faster you move the less happens over the course of your journey. With light the same happens ,but to an infinite degree.They are relativistic.
Or is there a lot,lot more to it than that?Is that example even relevant and are these light related effects entirely relativistic
If you could travel say from earth to a point 1lightyear away, the faster you travelled the shorter the distance would appear – length contraction – so the less time you would spend getting there. However, someone on earth would measure the distance as one light year so conclude that time is dilated for you.
When it is said that time does not pass for a photon as it moves in a vacuum does that imply that no internal activity is possible? (or does this description only apply to observations upon the photon moving in a vacuum?)What do you mean by internal activity or internal structure?
Is there such a concept as a potential internal structure of a photon that would be subject to change?
If any particle is massless does it necessarily lack an internal structure?
The photon is a travelling/propagating variation of the electromagnetic field, as such it will have a fundamental frequency and harmonics and hence has wavelike/pulselike properties. Because the varying fields can interact with certain materials eg dielectrics it can transfer momentum and hence has particle like properties.
So I don't tend to think in terms on internal structure or internal activity.
Post by: Bill S on 22/11/2017 18:51:46
Quote from: Colin
The photon is a travelling/propagating variation of the electromagnetic field, as such it will have a fundamental frequency and harmonics and hence has wavelike/pulselike properties. Because the varying fields can interact with certain materials eg dielectrics it can transfer momentum and hence has particle like properties.
So I don't tend to think in terms on internal structure or internal activity.
That makes sense to me, but seems to bring us back to the "not a wave...not a particle" idea.
Post by: Colin2B on 22/11/2017 23:28:45
That makes sense to me, but seems to bring us back to the "not a wave...not a particle" idea.I’m not sure it does.
The way I look at it is that sound waves can transfer momentum, but we never get into a discussion as to whether sound is a wave or particle. The reality is that with sound - as with other macro phenomena - the energy is effectively continuous and there is no value in considering quanta. That isn’t the case with atomic and sub atomic interactions, quanta become important, so if you are looking at light in the macro way (lots of photons) its best to treat it as a wave, but at the level of individual quanta it can be useful to do calculations as if it were a particle. But doing that doesn’t imply anything about the structure of light, the variations of E&B are very much a wave.
Post by: geordief on 23/11/2017 02:53:53
If you could travel say from earth to a point 1lightyear away, the faster you travelled the shorter the distance would appear – length contraction – so the less time you would spend getting there. However, someone on earth would measure the distance as one light year so conclude that time is dilated for you.So,for the sake of example if we discovered a promising exoplanet a thousand light years from Earth and were able to send a spacecraft in its direction at .99c with a nuclear family or two on board how much would they have aged by the time they reached their destination?**
I take it that ,if they returned to Earth it would be a little over 2000 years later....
**not so good at maths ...it wouldn't be 140 years would it ;-)
Post by: Kryptid on 23/11/2017 03:59:26
So,for the sake of example if we discovered a promising exoplanet a thousand light years from Earth and were able to send a spacecraft in its direction at .99c with a nuclear family or two on board how much would they have aged by the time they reached their destination?**
I take it that ,if they returned to Earth it would be a little over 2000 years later....
**not so good at maths ...it wouldn't be 140 years would it ;-)
http://www.emc2-explained.info/Dilation-Calc/#.WhZHYFWnHrc (http://www.emc2-explained.info/Dilation-Calc/#.WhZHYFWnHrc)
Post by: jeffreyH on 23/11/2017 06:19:21
If you could travel say from earth to a point 1lightyear away, the faster you travelled the shorter the distance would appear – length contraction – so the less time you would spend getting there. However, someone on earth would measure the distance as one light year so conclude that time is dilated for you.So,for the sake of example if we discovered a promising exoplanet a thousand light years from Earth and were able to send a spacecraft in its direction at .99c with a nuclear family or two on board how much would they have aged by the time they reached their destination?**
I take it that ,if they returned to Earth it would be a little over 2000 years later....
**not so good at maths ...it wouldn't be 140 years would it ;-)
Don't underestimate yourself.