The Colony ship returns

[mindlight]

A Colony ship is sent out from the earth and travels very fast to a new colony world, where it unloads settlers. Assuming these settlers are successful at creating a working colony the colony ship then immediately returns to earth. The whole distance there and back was 20 light-years. On its return, due to the nearness they were traveling to the speed of light, the crew discovers that history has moved on 5000 years but in their experience, they have only been away for 40 years (20 years there and 20 years back) and have only aged 40 years over the whole journey.

If the colony sends 1 message a year to the colony ship from the moment it is established how many messages will there be in its inbox when it makes it home to earth?

How did you work that out? Could you also tell me how fast the ship must have been traveling?

 

[AV1611VET]

If the colony sends 1 message a year to the colony ship from the moment it is established how many messages will there be in its inbox when it makes it home to earth?

None.

Hillary Clinton deleted them all.

 

[Shemjaza]

A Colony ship is sent out from the earth and travels very fast to a new colony world, where it unloads settlers. Assuming these settlers are successful at creating a working colony the colony ship then immediately returns to earth. The whole distance there and back was 20 light-years. On its return, due to the nearness they were traveling to the speed of light, the crew discovers that history has moved on 5000 years but in their experience, they have only been away for 40 years (20 years there and 20 years back) and have only aged 40 years over the whole journey.

If the colony sends 1 message a year to the colony ship from the moment it is established how many messages will there be in its inbox when it makes it home to earth?

How did you work that out? Could you also tell me how fast the ship must have been traveling?

I don't really understand the thought experiment.

You say they were travelling at the speed of light, but also say 5000 years pass while they were on their journey?

If the ship could travel very near the speed of light, then only 40ish years would pass on Earth and 20ish years since the colony was founded. However from the crew's persepctive a lot less than 40 years would have passed... so assuming they can't receive messages while at speed they would have 20 messages waiting for them.

 

[Neogaia777]

A Colony ship is sent out from the earth and travels very fast to a new colony world, where it unloads settlers. Assuming these settlers are successful at creating a working colony the colony ship then immediately returns to earth. The whole distance there and back was 20 light-years. On its return, due to the nearness they were traveling to the speed of light, the crew discovers that history has moved on 5000 years but in their experience, they have only been away for 40 years (20 years there and 20 years back) and have only aged 40 years over the whole journey.

If the colony sends 1 message a year to the colony ship from the moment it is established how many messages will there be in its inbox when it makes it home to earth?

How did you work that out? Could you also tell me how fast the ship must have been traveling?

Well, it would have been at half light speed, and I'm not sure how much time would have been slowed down for them at that speed, as it starts out to be "very little", and "not that much or drastic" at first, but then grows exponentially, and to even eventually infinitely, (supposedly), at very near to, or at, the exact speed of light exactly, etc...

If they could travel through a portal or some kind of hole in space though, they may be able to overcome the whole time dilation issue, or time slowing down for them issue/thing entirely though, etc, in which case time would not slow down for them, and they would arrive back at earth 40 years later, and with 40 years having passed for both of them, regardless, etc...

But without doing that, you have to consider that if time does slow down enough for them to have 5,000 years having passed on earth when they get back, then would they really have been moving any faster, or maybe just a whole heck of a lot slower maybe, seeing as time would have slowed down very much drastically for them, etc...?

But, then again, I guess that's relativity for you folks, etc...?

God Bless!

 

[mindlight]

I don't really understand the thought experiment.

You say they were travelling at the speed of light, but also say 5000 years pass while they were on their journey?

If the ship could travel very near the speed of light, then only 40ish years would pass on Earth and 20ish years since the colony was founded. However from the crew's persepctive a lot less than 40 years would have passed... so assuming they can't receive messages while at speed they would have 20 messages waiting for them.

So you are saying if they only travelled 40 light years then the maximum number of messages traveling at the speed of light would be 20.

Well, it would have been at half light speed, and I'm not sure how much time would have been slowed down for them at that speed, as it starts out to be "very little", and "not that much or drastic" at first, but then grows exponentially, and to even eventually infinitely, (supposedly), at very near to, or at, the exact speed of light exactly, etc...

If they could travel through a portal or some kind of hole in space though, they may be able to overcome the whole time dilation issue, or time slowing down for them issue/thing entirely though, etc, in which case time would not slow down for them, and they would arrive back at earth 40 years later, and with 40 years having passed for both of them, regardless, etc...

But without doing that, you have to consider that if time does slow down enough for them to have 5,000 years having passed on earth when they get back, then would they really have been moving any faster, or maybe just a whole heck of a lot slower maybe, seeing as time would have slowed down very much drastically for them, etc...?

But, then again, I guess that's relativity folks, etc...?

God Bless!

Yes, you are traveling at half-light speed. The clock paradox dictates that my experience of time, the faster I get, slows down relative to a person who remains at rest. So even though the crew felt they were only away for 40 years the time may have been much longer. If there is a formula for this then I guess someone will point out that my 5000-year shift into the future cannot be true. But whatever the actual number it must be more than 40 years if the time dilation effect of relativity is real. But for someone in the new colony sending emails, they send one every year at the speed of light. Now if the crew experiences only a 20-year return journey but find the time is much greater on earth then would they also have more than 20 emails even though the emails traveled twice as fast as them with no time dilation.

 

[Neogaia777]

So you are saying if they only travelled 40 light years then the maximum number of messages traveling at the speed of light would be 20.


Yes, you are traveling at half-light speed. The clock paradox dictates that my experience of time, the faster I get, slows down relative to a person who remains at rest. So even though the crew felt they were only away for 40 years the time may have been much longer. If there is a formula for this then I guess someone will point out that my 5000-year shift into the future cannot be true. But whatever the actual number it must be more than 40 years if the time dilation effect of relativity is real. But for someone in the new colony sending emails, they send one every year at the speed of light. Now if the crew experiences only a 20-year return journey but find the time is much greater on earth then would they also have more than 20 emails even though the emails traveled twice as fast as them with no time dilation.

Again, and like I just said, that's relativity for you folks, etc...

Because would it only be the people inside the ship that would experience time slowing down for them, or would it also be the ship also, etc...?

People have been trying to solve and/or resolve this for a very long time, and I don't think anyone is really any closer to fully solving or resolving it yet, etc...

The only real solution is to be able to open up a hole in space or something, or finding some other way somehow of overcoming the effects/affects of time dilation/theory of relativity at very high speeds that are at or are very near to the speed of light, etc...

God Bless!

 

[keith99]

If the distance is 20 light years each way and the ship was traveling at near light speed both ways the time as measured on earth is 40 years. As measured on the ship months at most, depending on just what is meant by near light speed.

 

[Neogaia777]

As measured on the ship months at most, depending on just what is meant by near light speed.

Because time slowed down very drastically for them, and perhaps the ship, etc.

So would they really be traveling any faster, etc...?

Because that's relativity for you, etc.

God Bless!

 

[Neogaia777]

Because time slowed down very drastically for them, and perhaps the ship, etc.

So would they really be traveling any faster, etc...?

Because that's relativity for you, etc.

God Bless!

But since matter and/or physical material starts to lose it's cohesion through normal space at those speeds, then the ship, and the people, would probably fly apart, and/or lose it's/their structural integrity/material cohesion at those speeds anyway, so it's probably a mute point, etc, but I guess some still do like the mental exercise sometimes still though, etc...

But it's really not all that complicated, but just unsolvable/unresolvable right now, so...?

God Bless!

 

[Neogaia777]

But since matter and/or physical material starts to lose it's cohesion through normal space at those speeds, then the ship, and the people, would probably fly apart, and/or lose it's/their structural integrity/material cohesion at those speeds anyway, so it's probably a mute point, etc, but I guess some still do like the mental exercise sometimes still though, etc...

But it's really not all that complicated, but just unsolvable/unresolvable right now, so...?

God Bless!

And not to mention also all the normal matter and material with any kind of mass becoming super-heated at those speeds which is part of the reason for the loss of cohesion also, etc...

Forgot to mention that also, etc...

God Bless!

 

[sjastro]

This is a problem which involves half the twin paradox without the journey towards the colony planet.
Assuming the round trip is symmetrical we can calculate the velocity of the colony ship using the special relativity time dilation formula.

∆t = ∆τ/√(1 - v²/c²)

∆t = 5000 years and is the coordinate time or time taken for the round trip.
∆τ = 40 years and is the proper time that elapses on the colony ship.
c is the speed of light and v is the velocity of the colony ship.

Solving for v gives v = 0.99968c.

Since the colony ship is moving away from the colony on its return to Earth, the clocks on the ship and colony recede from each other and the frequency of their signals is reduced from the proper frequency by the Doppler effect.

In this case the Doppler factor is √[(c-v)/(c+v)] = √[(c-0.99968c)/(c+0.99968c)] = 1/250.
Hence for every year a signal is sent from the colony it takes 250 years on the ship.
Since the time taken for the ship to return home is 2500 years it will receive 10 messages during its trip back to Earth.

 

[Neogaia777]

This is a problem which involves half the twin paradox without the journey towards the colony planet.
Assuming the round trip is symmetrical we can calculate the velocity of the colony ship using the special relativity time dilation formula.

∆t = ∆τ/√(1 - v²/c²)

∆t = 5000 years and is the coordinate time or time taken for the round trip.
∆τ = 40 years and is the proper time that elapses on the colony ship.
c is the speed of light and v is the velocity of the colony ship.

Solving for v gives v = 0.99968c.

Since the colony ship is moving away from the colony on its return to Earth, the clocks on the ship and colony recede from each other and the frequency of their signals is reduced from the proper frequency by the Doppler effect.

In this case the Doppler factor is √[(c-v)/(c+v)] = √[(c-0.99968)/(c+0.99968)] = 1/250.
Hence for every year a signal is sent from the colony it takes 250 years on the ship.
Since the time taken for the ship to return home is 2500 years it will receive 10 messages during its trip back to Earth.

But would that be because time actually slowed down for the colony ship...?

Or not, etc...?

Or maybe only just the people in it...?

Or what, etc...?

God Bless!

 

[Neogaia777]

But would that be because time actually slowed down for the colony ship...?

Or not, etc...?

Or maybe only just the people in it...?

Or what, etc...?

God Bless!

@sjastro

Or, IOW's, if time actually slowed down drastically for the ship, would that have also affected it's travel through space, etc...?

Because to me it seems like a kind of paradox right now, etc...?

Or am I wrong about that maybe, etc...?

God Bless!

 

[Neogaia777]

Or, IOW's, if time actually slowed down drastically for the ship, would that have also affected it's travel through space, etc...?

Because to me it seems like a kind of paradox right now, etc...?

Or am I wrong about that maybe, etc...?

God Bless!

@sjastro

Or maybe say, at half the speed of light or something, it might just only very very slightly slow it's travel through space, but not nearly enough to make a huge difference or something like that, and probably not even close to that, or hardly even at all, etc, but then maybe say, as you approach speeds much faster than that, or speeds much closer to the speed of light, or light speed, if it were possible, etc, (explained earlier, etc) it would only then start to affect it so much, or to the point maybe, where there would really might maybe be no point maybe, in even trying to go that fast, because it would actually slow the ship at that point instead of it be actually making it go faster, or speeding it up at that point maybe, or something like that maybe, etc...?

I don't know...? Is there a formula or equation for that maybe...? Because I'm not so good at math right now at this point in my life right now, etc...?

But, am I right, or am I wrong maybe...?

Because I'd really like to know if there is an answer, etc...?

God Bless!

 

[Maria Billingsley]

A Colony ship is sent out from the earth and travels very fast to a new colony world, where it unloads settlers. Assuming these settlers are successful at creating a working colony the colony ship then immediately returns to earth. The whole distance there and back was 20 light-years. On its return, due to the nearness they were traveling to the speed of light, the crew discovers that history has moved on 5000 years but in their experience, they have only been away for 40 years (20 years there and 20 years back) and have only aged 40 years over the whole journey.

If the colony sends 1 message a year to the colony ship from the moment it is established how many messages will there be in its inbox when it makes it home to earth?

How did you work that out? Could you also tell me how fast the ship must have been traveling?

I'm very bad at math so I'll take the common sense route.
No such thing as years when traveling like this. No aging will occur because
they would be in stasis. Nothing can travel the speed of light but light itself so a worm hole would need to be discovered then maybe 20 up and 20 back would have a chance. And that would be in real time.

 

[sjastro]

@Neogaia777

Answering your questions collectively one of the great misunderstandings in relativity is what is actually meant when time slows down.
Your proper time whether it be your biological clock or your wristwatch doesn't slow down irrespective of how fast you are travelling.
It dispels the idea of near immortality when travelling close to the speed of light.

Time is relative to the motion of the observer and can be explained by the muon experiment.
Muons are short lived particles formed due to collisions between cosmic rays and the upper atmosphere.
Without taking relativity into account the survival rate of muons reaching the ground is around 0.3 per million due to its short half-life of 1.56 microseconds.

Experimentally the survival rate is 49,000 per million.
Since muons are travelling close to the speed of light this can be explained through time dilation.
This would suggest the muon's half life increases as a result of time slowing down which is incorrect.

The experiment can be explained by looking at the problem from the Earth's frame of reference and the muon's frame of reference.

In the Earth's frame of reference the muon's clock undergoes time dilation which is it's coordinate time.
In the muon's frame of reference however the distance the muon travels is length contracted resulting in more muons reaching the surface because its travels a shorter distance, not because its proper time is dilated.
Both the Earth frame and muon frame observers agree on the experimental value, based on time dilation in the Earth's frame and length contraction in the muon's frame.

 

[Neogaia777]

I'm very bad at math so I'll take the common sense route.
No such thing as years when traveling like this. No aging will occur because
they would be in stasis. Nothing can travel the speed of light but light itself so a worm hole would need to be discovered then maybe 20 up and 20 back would have a chance. And that would be in real time.

A way would have to be discovered to negate the effects that traveling through normal space-time has on matter, or physical material as we know it/them right now, then things would be in normal real time, etc...

Or, IOW's, however long it took you travel there, and/or get back, would be the same time elapsed equally and normally for everyone, etc...

Both when you arrived at your destination, and when you got back from your original point of origin, etc...

Be that years, or days, or hours, or minutes, etc...

Or IOW's however long it took you to get there and get back, and adding to that any time you spent there, etc, would be the same amount of time elapsed from the place you left when you got back, etc...

Theoretically anyway, because we still don't know what kind of effect something like that would have on any of us, or our ship, as we traveled through it, etc, because we don't even know if anything like that even exists yet, etc...

All very highly theoretical still, etc, but, "in theory" anyway, etc, time should maybe be normal, or should maybe elapse normally and equally for everyone as you traveled "that way" through it, etc...

"In theory" anyway, etc...

God Bless!

 

[Neogaia777]

@Neogaia777

Answering your questions collectively one of the great misunderstandings in relativity is what is actually meant when time slows down.
Your proper time whether it be your biological clock or your wristwatch doesn't slow down irrespective of how fast you are travelling.
It dispels the idea of near immortality when travelling close to the speed of light.

Time is relative to the motion of the observer and can be explained by the muon experiment.
Muons are short lived particles formed due to collisions between cosmic rays and the upper atmosphere.
Without taking relativity into account the survival rate of muons reaching the ground is around 0.3 per million due to its short half-life of 1.56 microseconds.

Experimentally the survival rate is 49,000 per million.
Since muons are travelling close to the speed of light this can be explained through time dilation.
This would suggest the muon's half life increases as a result of time slowing down which is incorrect.

The experiment can be explained by looking at the problem from the Earth's frame of reference and the muon's frame of reference.

In the Earth's frame of reference the muon's clock undergoes time dilation which is it's coordinate time.
In the muon's frame of reference however the distance the muon travels is length contracted resulting in more muons reaching the surface because its travels a shorter distance, not because its proper time is dilated.
Both the Earth frame and muon frame observers agree on the experimental value, based on time dilation in the Earth's frame and length contraction in the muon's frame.

But I thought time was supposed to freeze for the/an object at the exact speed of light, etc...?

So doesn't that mean it also slows down also as you get very close to it, etc...?

Or am I wrong about that, etc...?

God Bless!

 

[Neogaia777]

But I thought time was supposed to freeze for the object at the exact speed of light, etc...?

So doesn't that mean it it also slows down also as you get very close to it, etc...?

Or am I wrong about that, etc...?

God Bless!

@sjastro

And nobody is talking about "immortality" here, etc, lol... It's just that I thought Einstiens theory of general relativity suggested that time quite literally stops for an object at the exact speed of light, etc...?

Or am I wrong about that, etc...?

God Bless!

 

[FrumiousBandersnatch]

A Colony ship is sent out from the earth and travels very fast to a new colony world, where it unloads settlers. Assuming these settlers are successful at creating a working colony the colony ship then immediately returns to earth. The whole distance there and back was 20 light-years. On its return, due to the nearness they were traveling to the speed of light, the crew discovers that history has moved on 5000 years but in their experience, they have only been away for 40 years (20 years there and 20 years back) and have only aged 40 years over the whole journey.

If the colony sends 1 message a year to the colony ship from the moment it is established how many messages will there be in its inbox when it makes it home to earth?

How did you work that out? Could you also tell me how fast the ship must have been traveling?

It's not clear to me how far the round trip is - 20 ly or 40 ly?

Also, I'm not sure the maths works - if it's 20 light-years there and back (10 light-years out and 10 light-years back), then at 5g acceleration (reaching 0.999c at each mid-point), elapsed time on Earth would be nearly 21 years and the elapsed time on the ship would be around 3 years.

If it's 40 light-years there and back (20 light-years out and 20 light-years back) then at 5g the elapsed time on Earth would be a little under 41 years and the elapsed time on the ship would be a little over 3.5 years.