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A Thought Experiment And Challenge I Have Come Up With.


Grundles

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You have just invented the world's first time machine however this time machine can only go forward in time by huge amounts. You test the machine for the first time and realise that the "time travelled" indicator does not work. When you eventually stop at some unknown point in the future you are greeted by a futuristic race of intelligent beings. This race, upon your arrival, engineer a translator and you are able to converse with them with all the language you know and all the gestures and signs of emotion. You haven't taken anything with you apart from the clothes you are wearing and a time machine with some minor faults.

 

​In this future they use a different calendar. All records of previous calendars, previous earth maps and everything you ever knew in the past has been destroyed by father time and the futuristic race had no ideas and no clues that the human race ever existed.

 

How would you be able to tell them what period of time you are from and how could you find out how far into the future you have travelled?

 

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Welcome to hypography, Grundles :)

 

I was going to say something about comparing the position of distinct stars in the old and new night sky, or the spectrum of the Sun, or the size of the disk of the Moon, but as I only have the cloths on my back and the faulty one-way time machine, unless I have an eidetic memory, or the time machine has an good astronomy database, I wouldn’t have the needed old data to compare to the new.

 

If my futuristic hosts are good at microbiology, I’d have them look at my DNA. If they or some other animal existant or for which they have preserved samples are descended from humans, or at least have a fairly recent common ancestor with us, they ought to be able to make a good estimate about when I lived, based on our genetic distance.

 

If some mass-extinction has entirely erased us from the biological world, they’d at least be able to tell I was from far off in space or time. If they are good paleontologists, they might be able to match me with the gross or genetic fossil record, and date me that way.

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Yes at first so was thinking of ideas such as measuring the length of a day using the method of radioactive decay used in atomic clocks. If you had a watch they would be able to estimate fairly closely the length of a day in our time as compared to theirs and work out how far in the future you have travelled.

 

However this does have it's problems. What if when you reach the future the earth had already become tidally locked to the sun... then you can at least say that you have travelled far enough into the future that this will have happened but you couldn't say how much further past that point you are. Or possibly a large meteorite may have hit the earth at some point and threw the time of a day way off what it used to be and in this case this method will be worse than useless.

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Yes at first so was thinking of ideas such as measuring the length of a day using the method of radioactive decay used in atomic clocks. If you had a watch they would be able to estimate fairly closely the length of a day in our time as compared to theirs and work out how far in the future you have travelled.

I haven’t memorized the definition of the second “the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium 133 atom”, that a 2016 day is about 86400.002 seconds (I know the 24*60*60=86400 part, or course, but don’t remember the 0.002), or that the length of day has been increasing by roughly 1 hr per 250,000,000 years (0.000016 s/yr). So, since I didn’t get to bring a copy of the internet or a general science textbook with me, I’d have to hope my hosts knew this, so all I’d have to say is “back when I’m from, days were 86400 seconds long”, and they could figure out the rest. Even if they’re advanced enough to have atomic clocks, I worry that the “9,192,631,770 hyperfine 133Cs” definition would be as lost as all the other artifacts of my culture, like my language.

 

Or possibly a large meteorite may have hit the earth at some point and threw the time of a day way off what it used to be and in this case this method will be worse than useless.

True.

 

What if when you reach the future the earth had already become tidally locked to the sun... then you can at least say that you have travelled far enough into the future that this will have happened but you couldn't say how much further past that point you are.

I do remember that the Earth won’t be tidally locked to the Sun, except in an uncertain scenario of it surviving the Sun’s red giant phase, about 5,000,000,000 to 8,000,000,000 years from now. The main reason its rotation is slowing is that it’s slowly tidally locking with the Moon, a process that won’t complete before the red giant Sun, which likely will burn the Earth and the Moon to atoms.

 

If I’ve traveled more than 1,000,000,000 years into the future, and assuming nobody’s done a superengineering Earth-moving project, it’d be pretty easy to give a rough estimate of my age. If the Earth’s Venus-like, or a waterless desert, it’s been over 1,000,000,000 years. If the Sun looks like this

225px-Red_giant_sunrise_6_billion_years.

it’s been around 5,000,000,000. In either case, my time machine better have enough life-support – insulation, cooling, and oxygen – to keep me alive ‘til I’m rescued.

 

If I’ve only traveled a few 1,000 or 1,000,000 years into the future, I’d have to have precise astronomy data, which isn’t allowed according to the original question.

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Yes precise astronomy data isn't what you packed for the test run as you didn't expect to get stuck in the future (in this hypothetical universe you are not a very forward thinking person, which I'm sure is not at all true in our real universe).

 

I do see your point about knowing the exact time of a second in relation to caesium decay, I hadn't thought of that as I thought perhaps you could measure my watch for two full rotations of the hour hand and measure the decay of caesium to find out the length of a day in our time using a universal standard of time. This could then be compared. Obviously the more accurate my watch the more accurate the result but as you pointed out, earth is slowing at an incredibly slow rate and this leaves huge room for error, and if I'm only a few thousand years in ton the future then the measurement would be so fine it is likely to be completely undetectable.

 

I didn't know that the earth won't become tidally locked to the sun. I read in an astronomy journal that it will. However a quick internet search throws up conflicting articles. This is something I'm definitely going to look into further. Perhaps when I do more research on this topic I may be able to come up with a solution to my problem that satisfies every possible scenario. ...bar death upon arrival into the future.

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I do see your point about knowing the exact time of a second in relation to caesium decay, I hadn't thought of that as I thought perhaps you could measure my watch for two full rotations of the hour hand and measure the decay of caesium to find out the length of a day in our time using a universal standard of time.

Hey, that cheating! You said all I have are the cloths I’m wearing and the presumably useless time machine – you didn’s say I was wearing a watch!

 

If I get to take a watch, it would be easy to tell my hosts “the days were about 86400 seconds long when I come from, and here’s a gadget that shows how long a ‘second’ is”, and let them figure out the rest.

 

The typical watch clock is considered accurate it if’s ±15 s/month (about 6/1,000,000) so my hosts should be able to measure my temporal origin with a precision of about 10,000,000 years or so.

 

This is still a lot less precise than if I knew the magic atomic clock definition of the second, 9,192,631,770. If they knew this, they should be able to locate me with a precision of about 200 years.

 

If I brought along more than my dumb clothing and a useless time machine, I think I can claim that I may well have brought a good chunk of useful science data with me. The “watch” I actually carry, and presumably would have on me as I carelessly hop into my time machine of one-way doom for its maiden test voyage, isn’t just an electronic clock but a smartphone, which has a cache of web pages I’ve recently viewed. Since I’m presumably some sort of* time scientist, I think there’s a good chance that history might include a reference to something about atomic clocks and the second including the magic “9,192,631,770 133Cs hyperfine transitions”. Better yet, if I accidentally or intentionally took a picture of the night sky, a decent astronomer from the future should be able to figure out when I’m from changes in the arrangement of the stars. Even with a low-quality phone camera, that would be good enough for about 1,000 year temporal location precision.

 

(Source: watching the pixels change while moving the slider in this super-cool browser app :) )

 

* I’m imagining a scene something like this:

(Senior scientists to person wearing a office/industrial vacuum cleaner): Hey, Eduardo, isn’t it? How would you like to help us with a little testing? (points to TIME MACHINE)

(Eduardo, after some wary glances at scientists and nearest door): I’m just paid to clean the place, man. I’m not allowed to touch the equipment. Insurance, you know.

Senior scientist: Damn!

(turns to assistant, who’s likewise looking nervous and checking out the door): Hey, how about that IT guy – Craig I think it was. Can you call him?

(Assistant, relieved, makes call)

(Craig, entering): You called, sir? That thing’s not having trouble again, is it?

(Senior scientist): Craig! We’re ready for a “lights on” test of the gadget, but are having trouble matching the mission requirements to the skillsets of our core team members, when I remembered that thing you fixed for us last week. We were all impressed with your outside-the-box thinking and flexibility, and were thinking that’s exactly what the mission needs. All you need to do is sit in the cockpit. (gestures to TIME MACHINE) It’s programmed for a minimal excursion, 120 seconds dwell time, then return to +5 seconds from instant of departure. In the unlikely event of a problem, we’re confident you’ll be able to handle it – when have you ever failed to solve a problem?

(Craig, grinning and preening): Why sure, sir! This is such a great honor, I can’t believe it!

(walks to and sits down in TIME MACHINE, scientists confer, countdown begins...)

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Haha yeah I did cheat a little bit. With a watch, smartphone, reams of astronomical data and an idetic memory, this problem would be very easy to solve. It's just one idea I had. What science forum would this be if we didn't ask what the outcome could be under different circumstances? And until me, or somebody else, comes up with a comprehensive solution to the original problem that would work in every possible scenario, then why not throw a few extra bits in for fun and to get the thinking going? :) . A lot of questions have been solved (and even more arising) by asking "what if?".

 

I found your last post very amusing. That conversation is one I could easily imagine observing in my own workplace. I would probably be the person sent on a one-way trip to my doom.

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  • 2 months later...

You have just invented the world's first time machine however this time machine can only go forward in time by huge amounts. You test the machine for the first time and realise that the "time travelled" indicator does not work. When you eventually stop at some unknown point in the future you are greeted by a futuristic race of intelligent beings. This race, upon your arrival, engineer a translator and you are able to converse with them with all the language you know and all the gestures and signs of emotion. You haven't taken anything with you apart from the clothes you are wearing and a time machine with some minor faults.

 

​In this future they use a different calendar. All records of previous calendars, previous earth maps and everything you ever knew in the past has been destroyed by father time and the futuristic race had no ideas and no clues that the human race ever existed.

 

How would you be able to tell them what period of time you are from and how could you find out how far into the future you have travelled?

You couldn't .

 

All information about where you are from is erased.

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