Brian Sir, This is not fair. How can a girl have a beard ? (3:20)

What is confusing about the paradox is that if I see your clock run slower and you see my clock run slower how can one of us age faster than the other? Since the frames of reference appear symmetrical (I am moving in your frame of reference and you are moving in my frame of reference) how do you explain an age difference? So where is the asymmetry?

First off, I want to point out that whether acceleration is instantaneous or not doesn’t really matter for the analysis. What is important is who is doing the acceleration and the duration and size of the relative motion.

Suppose you go off in a spaceship and I stay back on earth. To make the analysis simple let’s assume you accelerate instantaneously to the speed of light (with respect to me), you stay at that same relative motion for half a year and then instantaneously decelerate so that you are stationary with respect to me, you stay that way for 5 seconds then instantaneously accelerate to the speed of light to travel back towards me.

Let’s see what you observe.

Since you are travelling at the speed of light you see my clock standing still. The ray of light sent out to you when the second hand om my clock moved (one second after you left) never catches up to you (until you decelerate). Only when you decelerate to stationary (with respect to me) after half a year do you see my clock suddenly start to tick exactly at the same rate that I see it tick. When, after 5 seconds you accelerate and travel back to Earth you see my clock tick at a much faster rate (twice as fast as what I observe to be exact) as you intercept the light rays counting off the seconds on my clock as each of those light rays are travelling shorter and shorter distances to reach you as you head back to Earth.

What do I observe when you stop (with respect to me) after half a year?

Nothing!! You will still se my clock standing still. In fact, you will see my clock stand still as long as the light rays sent when you are moving away from me are travelling to Earth. This is the missing asymmetry we needed! When you are half a light year away, it will take half a light year before those rays reach Earth (so in total a year after you left). Only after that half a year (so in total 1 year) will I see your clock suddenly start to tick at a (for me) normal rate. But only for 5 seconds because after half a light year and 5 seconds (after you stopped with respect to me) you will have landed back on Earth!

So summarising: you saw my clock stand still for half a year, run at the same rate that I saw my clock run for 5 seconds and then run twice as fast for half a year. Both you and I will have seen my clock measure off 1 year and 5 seconds. I however will only see that your clock has moved forward by 5 seconds when you land. You saw yourself take off, then suddenly see your clock tick for 5 seconds where your ship was a half light year from Earth, then land. Outside those 5 seconds you had no perception of time. Both you and I will have seen that my clock measure off 5 seconds.

If you have a problem with the perception of no time passing whatsoever you can replace light speed with 99.99% of light speed or in fact any other percentage you care to use. Then you will see some time pass on your clock outside the 5 seconds (however small).

This all sounds like a latency issue. Where does time dilation creep in? The answer is that whether I am moving away from you or towards you at light speed the light rays I send off also move at light speed to you due to the constancy of light supposition. In a Newton world those speeds (and the resulting analysis) would yield different results due to the effect of using a Newton based velocity addition instead of a relativistic velocity addition.

This is a bit more speculative but we could explain time dilation as saying when your clock slows you are packing more “physical time” between two clock ticks. Since speed = distance/time and thus distance = speed * time if I can pack more physical time in my time measurement then for any given speed I will have more physical distance. In my view, with Lorentz contraction there is no actual physical distance shortening it our metric (the physical length of a meter) that is changed due to a change in time. Meters are defined using time: the distance light travels in 1 second. If I change my duration of a second then clearly the distance measured will change too.

What is confusing about the paradox is that if I see your clock run slower and you see my clock run slower how can one of us age faster than the other? Since the frames of reference appear symmetrical (I am moving in your frame of reference and you are moving in my frame of reference) how do you explain an age difference? So where is the asymmetry?

First off, I want to point out that whether acceleration is instantaneous or not doesn’t really matter for the analysis. What is important is who is doing the acceleration and the duration and size of the relative motion.

Suppose you go off in a spaceship and I stay back on earth. To make the analysis simple let’s assume you accelerate instantaneously to the speed of light (with respect to me), you stay at that same relative motion for half a year and then instantaneously decelerate so that you are stationary with respect to me, you stay that way for 5 seconds then instantaneously accelerate to the speed of light to travel back towards me.

Let’s see what you observe.

Since you are travelling at the speed of light you see my clock standing still. The ray of light sent out to you when the second hand om my clock moved (one second after you left) never catches up to you (until you decelerate). Only when you decelerate to stationary (with respect to me) after half a year do you see my clock suddenly start to tick exactly at the same rate that I see it tick. When, after 5 seconds you accelerate and travel back to Earth you see my clock tick at a much faster rate (twice as fast as what I observe to be exact) as you intercept the light rays counting off the seconds on my clock as each of those light rays are travelling shorter and shorter distances to reach you as you head back to Earth.

What do I observe when you stop (with respect to me) after half a year?

Nothing!! I will still see your clock standing still. In fact, I will see your clock stand still as long as the light rays sent when you are moving away from me are travelling to Earth. This is the missing asymmetry we needed! When you are half a light year away, it will take half a light year before those rays reach Earth (so in total a year after you left). Only after that half a year (so in total 1 year) will I see your clock suddenly start to tick at a (for me) normal rate. But only for 5 seconds because after half a light year and 5 seconds (after you stopped with respect to me) you will have landed back on Earth!

So summarising: you saw my clock stand still for half a year, run at the same rate that I saw my clock run for 5 seconds and then run twice as fast for half a year. Both you and I will have seen my clock measure off 1 year and 5 seconds. I however will only see that your clock has moved forward by 5 seconds when you land. You saw yourself take off, then suddenly see your clock tick for 5 seconds where your ship was a half light year from Earth, then land. Outside those 5 seconds you had no perception of time. Both you and I will have seen that my clock measure off 5 seconds.

If you have a problem with the perception of no time passing whatsoever you can replace light speed with 99.99% of light speed or in fact any other percentage you care to use. Then you will see some time pass on your clock outside the 5 seconds (however small).

This all sounds like a latency issue. Where does time dilation creep in? The answer is that whether I am moving away from you or towards you at light speed the light rays I send off also move at light speed to you due to the constancy of light supposition. In a Newton world those speeds (and the resulting analysis) would yield different results due to the effect of using a Newton based velocity addition instead of a relativistic velocity addition.

This is a bit more speculative but we could explain time dilation as saying when your clock slows you are packing more “physical time” between two clock ticks. Since speed = distance/time and thus distance = speed * time if I can pack more physical time in my time measurement then for any given speed I will have more physical distance. In my view, with Lorentz contraction there is no actual physical distance shortening it our metric (the physical length of a meter) that is changed due to a change in time. Meters are defined using time: the distance light travels in 1 second. If I change my duration of a second then clearly the distance measured will change too.

What is confusing about the paradox is that if I see your clock run slower and you see my clock run slower how can one of us age faster than the other? Since the frames of reference appear symmetrical (I am moving in your frame of reference and you are moving in my frame of reference) how do you explain an age difference? So where is the asymmetry?

First off, I want to point out that whether acceleration is instantaneous or not doesn’t really matter for the analysis. What is important is who is doing the acceleration and the duration and size of the relative motion.

Suppose you go off in a spaceship and I stay back on earth. To make the analysis simple let’s assume you accelerate instantaneously to the speed of light (with respect to me), you stay at that same relative motion for half a year and then instantaneously decelerate so that you are stationary with respect to me, you stay that way for 5 seconds then instantaneously accelerate to the speed of light to travel back towards me.

Let’s see what you observe.

Since you are travelling at the speed of light you see my clock standing still. The ray of light sent out to you when the second hand om my clock moved (one second after you left) never catches up to you (until you decelerate). Only when you decelerate to stationary (with respect to me) after half a year do you see my clock suddenly start to tick exactly at the same rate that I see it tick. When, after 5 seconds you accelerate and travel back to Earth you see my clock tick at a much faster rate (twice as fast as what I observe to be exact) as you intercept the light rays counting off the seconds on my clock as each of those light rays are travelling shorter and shorter distances to reach you as you head back to Earth.

What do I observe when you stop (with respect to me) after half a year?

Nothing!! I will still see your clock standing still. In fact, I will see your clock stand still as long as there are light rays are travelling to Earth that you sent while moving away from me. This is the missing asymmetry we needed! When you are half a light year away, it will take half a light year before those rays reach Earth (so in total a year after you left). Only after that half a year (so in total 1 year) will I see your clock suddenly start to tick at a (for me) normal rate. But only for 5 seconds because after half a light year and 5 seconds (after you stopped with respect to me) you will have landed back on Earth!

So summarising: you saw my clock stand still for half a year, run at the same rate that I saw my clock run for 5 seconds and then run twice as fast for half a year. Both you and I will have seen my clock measure off 1 year and 5 seconds. I however will only see that your clock has moved forward by 5 seconds when you land. You saw yourself take off, then suddenly see your clock tick for 5 seconds where your ship was a half light year from Earth, then land. Outside those 5 seconds you had no perception of time. Both you and I will have seen that my clock measure off 5 seconds.

If you have a problem with the perception of no time passing whatsoever you can replace light speed with 99.99% of light speed or in fact any other percentage you care to use. Then you will see some time pass on your clock outside the 5 seconds (however small).

This all sounds like a latency issue. Where does time dilation creep in? The answer is that whether I am moving away from you or towards you at light speed the light rays I send off also move at light speed to you due to the constancy of light supposition. In a Newton world those speeds (and the resulting analysis) would yield different results due to the effect of using a Newton based velocity addition instead of a relativistic velocity addition.

This is a bit more speculative but we could explain time dilation as saying when your clock slows you are packing more “physical time” between two clock ticks. Since speed = distance/time and thus distance = speed * time if I can pack more physical time in my time measurement then for any given speed I will have more physical distance. In my view, with Lorentz contraction there is no actual physical distance shortening it our metric (the physical length of a meter) that is changed due to a change in time. Meters are defined using time: the distance light travels in 1 second. If I change my duration of a second then clearly the distance measured will change too.

What is confusing about the paradox is that if I see your clock run slower and you see my clock run slower how can one of us age faster than the other? Since the frames of reference appear symmetrical (I am moving in your frame of reference and you are moving in my frame of reference) how do you explain an age difference? So where is the asymmetry?

First off, I want to point out that whether acceleration is instantaneous or not doesn’t really matter for the analysis. What is important is who is doing the acceleration and the duration and size of the relative motion.

Suppose you go off in a spaceship and I stay back on earth. To make the analysis simple let’s assume you accelerate instantaneously to the speed of light (with respect to me), you stay at that same relative motion for half a year and then instantaneously decelerate so that you are stationary with respect to me, you stay that way for 5 seconds then instantaneously accelerate to the speed of light to travel back towards me.

Let’s see what you observe.

Since you are travelling at the speed of light you see my clock standing still. The ray of light sent out to you when the second hand om my clock moved (one second after you left) never catches up to you (until you decelerate). Only when you decelerate to stationary (with respect to me) after half a year do you see my clock suddenly start to tick exactly at the same rate that I see it tick. When, after 5 seconds you accelerate and travel back to Earth you see my clock tick at a much faster rate (twice as fast as what I observe to be exact) as you intercept the light rays counting off the seconds on my clock as each of those light rays are travelling shorter and shorter distances to reach you as you head back to Earth.

What do I observe when you stop (with respect to me) after half a year?

Nothing!! I will still see your clock standing still. In fact, I will see your clock stand still as long as there are light rays are travelling to Earth that you sent while moving away from me. This is the missing asymmetry we needed! When you are half a light year away, it will take half a light year before those rays reach Earth (so in total a year after you left). Only after that half a year (so in total 1 year) will I see your clock suddenly start to tick at a (for me) normal rate. But only for 5 seconds because after half a light year and 5 seconds (after you stopped with respect to me) you will have landed back on Earth!

So summarising: you saw my clock stand still for half a year, run at the same rate that I saw my clock run for 5 seconds and then run twice as fast for half a year. Both you and I will have seen my clock measure off 1 year and 5 seconds. I however will only see that your clock has moved forward by 5 seconds when you land. You saw yourself take off, then suddenly see your clock tick for 5 seconds where your ship was a half light year from Earth, then land. Outside those 5 seconds you had no perception of time. Both you and I will have seen that my clock measure off 5 seconds.

If you have a problem with the perception of no time passing whatsoever you can replace light speed with 99.99% of light speed or in fact any other percentage you care to use. Then you will see some time pass on your clock outside the 5 seconds (however small).

This all sounds like a latency issue. Where does time dilation creep in? The answer is that whether I am moving away from you or towards you at light speed the light rays I send off also move at light speed to you due to the constancy of light supposition. In a Newton world those speeds (and the resulting analysis) would yield different results due to the effect of using a Newton based velocity addition instead of a relativistic velocity addition.

This is a bit more speculative but we could explain time dilation as saying when your clock slows you are packing more “physical time” between two clock ticks. Since speed = distance/time and thus distance = speed * time if I can pack more physical time in my time measurement then for any given speed I will have more physical distance. In my view, with Lorentz contraction there is no actual physical distance shortening, it is our metric (the physical length of a meter) that is changed due to a change in time. Meters are defined using time: the distance light travels in 1/299 792 458 of a second second. If I change my duration of a second then clearly the distance measured will change too.

What is confusing about the paradox is that if I see your clock run slower and you see my clock run slower how can one of us age faster than the other? Since the frames of reference appear symmetrical (I am moving in your frame of reference and you are moving in my frame of reference) how do you explain an age difference? So where is the asymmetry?

First off, I want to point out that whether acceleration is instantaneous or not doesn’t really matter for the analysis. What is important is who is doing the acceleration and the duration and size of the relative motion.

Suppose you go off in a spaceship and I stay back on earth. To make the analysis simple let’s assume you accelerate instantaneously to the speed of light (with respect to me), you stay at that same relative motion for half a year and then instantaneously decelerate so that you are stationary with respect to me, you stay that way for 5 seconds then instantaneously accelerate to the speed of light to travel back towards me.

Let’s see what you observe.

Since you are travelling at the speed of light you see my clock standing still. The ray of light sent out to you when the second hand om my clock moved (one second after you left) never catches up to you (until you decelerate). Only when you decelerate to stationary (with respect to me) after half a year do you see my clock suddenly start to tick exactly at the same rate that I see it tick. When, after 5 seconds you accelerate and travel back to Earth you see my clock tick at a much faster rate (twice as fast as what I observe to be exact) as you intercept the light rays counting off the seconds on my clock as each of those light rays are travelling shorter and shorter distances to reach you as you head back to Earth.

What do I observe when you stop (with respect to me) after half a year?

Nothing!! I will still see your clock standing still. In fact, I will see your clock stand still as long as there are light rays are travelling to Earth that you sent while moving away from me. This is the missing asymmetry we needed! When you are half a light year away, it will take half a light year before those rays reach Earth (so in total a year after you left). Only after that half a year (so in total 1 year) will I see your clock suddenly start to tick at a (for me) normal rate. But only for 5 seconds because after half a light year and 5 seconds (after you stopped with respect to me) you will have landed back on Earth!

So summarising: you saw my clock stand still for half a year, run at the same rate that I saw my clock run for 5 seconds and then run twice as fast for half a year. Both you and I will have seen my clock measure off 1 year and 5 seconds. I however will only see that your clock has moved forward by 5 seconds when you land. You saw yourself take off, then suddenly see your clock tick for 5 seconds where your ship was a half light year from Earth, then land. Outside those 5 seconds you had no perception of time. Both you and I will have seen that my clock measure off 5 seconds.

If you have a problem with the perception of no time passing whatsoever you can replace light speed with 99.99% of light speed or in fact any other percentage you care to use. Then you will see some time pass on your clock outside the 5 seconds (however small).

This all sounds like a latency issue. Where does time dilation creep in? The answer is that whether I am moving away from you or towards you at light speed the light rays I send off also move at light speed to you due to the constancy of light supposition. In a Newton world those speeds (and the resulting analysis) would yield different results due to the effect of using a Newton based velocity addition instead of a relativistic velocity addition.

This is a bit more speculative but we could explain time dilation as saying when your clock slows you are packing more “physical time” between two clock ticks. Since speed = distance/time and thus distance = speed * time if I can pack more physical time in my time measurement then for any given speed I will have more physical distance. In my view, with Lorentz contraction there is no actual physical distance shortening, it is our metric (the physical length of a meter) that is changed due to a change in time. Meters are defined using time: the distance light travels in 1/299 792 458 of a second second. If I change my duration of a second then clearly the physical distance measured will change too.

Worst case scenarios involve guesstimations when out of Wifi range.

Twins of age become of different age due to travelling under spacetime transformations.

I want to be the observer in the ship, I’ve always wanted to travel through time, but wait, I’m already traveling through time. In fact I’ve already traveled 63yrs. into the future.