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Scenario: A wormhole is created between Sol (earth) and a planet in Alpha Centauri. Travel through the wormhole appears instantaneous from the travelers perspective. However, the wormhole has a one year jump.

So, if you go to Alpha Centauri using the wormhole, you are 1 year in the future (relative to earth time). When you come back, you are 1 year in the past (relative to A-Cent). You can send two way communications through the wormhole, but if you send it directly between the star systems not using the wormhole (sol to A-Centauri or vise-versa), it will take the 4.5 or so lightyears before it's received. Standard interstellar travel (not using the wormhole) would take far longer.

Technology level: In this scenario, we can imagine technology levels being equivalent to today for the purposes of observing interstellar bodies (telescopes and so on).

My question is this: how would people detect the 1 year time jump?

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    $\begingroup$ This reads far more like a question about a plot detail of your world, than a question about building your world. Do you mean to ask how would people detect a 1 year time jump instead? $\endgroup$
    – sphennings
    Nov 16, 2021 at 3:25
  • $\begingroup$ Correct. Would they notice something is off possibly by observing space or through some other method. $\endgroup$
    – TehKaoZ
    Nov 16, 2021 at 3:26
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    $\begingroup$ Can you edit your question so that it's asking this much more on topic question. Comments on this site are ephemeral and should not be expected to last. Any critical information should be included in the question body. $\endgroup$
    – sphennings
    Nov 16, 2021 at 3:31
  • $\begingroup$ sure thing. Done. $\endgroup$
    – TehKaoZ
    Nov 16, 2021 at 3:33
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    $\begingroup$ What if the wormhole is actually preserving the proper time, and it's the speed of light that's asymmetric? SpOoOoOoOoOky! (asymmetric speed of light has been a topic of popular discussion since someone made a video about it) $\endgroup$
    – user253751
    Nov 16, 2021 at 12:37

9 Answers 9

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Alpha Centauri is a multiple star system

Particularly, its main components, Alpha Centauri A and Alpha Centauri B are orbiting each other with 80 years period. Assuming that wormhole jump was prepared with the the best science and astronomy available, it would be immediately clear that positions of the components A and B are off. Further investigation, probably involving Proxima Centauri as a slow clock hand, would reveal that the time difference is one year rather that 81 years or more.

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    $\begingroup$ The time difference can't be longer than the light-speed distance, otherwise Novikov self-consistency principle kicks in and destroys our little wormhole long before it has a chance to transmit anything. $\endgroup$ Nov 16, 2021 at 16:05
  • $\begingroup$ @John Dvorak this is assuming that travelers know exactly what kind of wormhole effect to expect. Unless they try to travel back through the wormhole, they can only see that they moved some time to the future. $\endgroup$
    – Alexander
    Nov 16, 2021 at 19:50
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    $\begingroup$ @JohnDvorak: That's not what the Novikov self-consistency principle says. $\endgroup$
    – Joshua
    Nov 16, 2021 at 20:10
  • $\begingroup$ This may be a dumb question to ask (since I don't much know about how star system work)... but what if wormhole was 80 year time jump? how would people notice? perhaps check other stars? $\endgroup$
    – Skye-AT
    Nov 17, 2021 at 5:21
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    $\begingroup$ @Skye-AT in this case the time jump would not be immediately clear. Relative positions of other stars (Proxima Centauri, Sun, Barnard's star etc.) would be just slightly off, and HDE 226868's answer would become the most relevant. $\endgroup$
    – Alexander
    Nov 17, 2021 at 6:34
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One way would be to look at how the positions of the stars have changed - not just their apparent positions in the sky, but their actual positions in three-dimensional space. Many stars, particularly nearby ones, exhibit significant proper motion; their movement through space changes where they are on the sky. You could therefore figure out that there's been a one-year time jump by the following:

  1. Pick a star that exhibits a high, easily-measured proper motion.
  2. Using some three-dimensional trigonometry, convert its position as seen from Earth before the jump to its position as seen from Alpha Centauri before the jump.
  3. Compare the calculated pre-jump Alpha Centauri position to the observed post-jump Alpha Centauri position. Using previous measurements of the star's motion, you can figure out the change in time based on the change in the position and its predicted apparent speed.

Barnard's Star would be a good choice, since its proper motion is extremely high as seen from Earth or Alpha Centauri, and the change in position over one year should be easy to detect.

I remember now that this was the same principle used in the Doctor Who episode "Heaven Sent" to determine that the Doctor was further in time than he thought, although it was made simpler because 1) the time distances were significantly larger and therefore the positional anomalies were visible to the naked eye, and 2) he's the Doctor.

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    $\begingroup$ It occurs to me that one of the high priority research goals if this could be done would be to set up a telescope at the far end for parallax measurements of distant objects - and of course you'd calibrate it on something close by. So you'd expect this to be spotted quite quickly even if you weren't looking for it... $\endgroup$
    – Andrew
    Nov 16, 2021 at 13:08
  • $\begingroup$ @Andrew True. I believe current parallax efforts are limited to a distance of 2 AU between measurements. Being able to set up a second station 4.38 LY away would be huge. $\endgroup$ Nov 17, 2021 at 20:26
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My experience of normal space transmissions from my origin once I reach my destination.

I know radio light takes 4.5 years to make the trip. On Earth there is a radio of someone counting the years, broadcast to AC. At year 10 on AC I hear the Earth voice saying "5.5". That broadcast left earth 4.5 years ago at the year 5.5 and has been travelling thru space.

Now at the year 10 I travel from Earth to AC via wormhole. If travel is instantaneous I should arrive, tune into Earth and hear "5.5" because it is the year 10. But nay! I hear "6.5". I am 1 year in the future from when I was on Earth. It is the year 11.

The same is true in reverse. Counting radio should be the same both ways. On the year 10 I go thru the wormhole from AC to Earth. AC radio should say "5.5". But it says "4.5". I am at the year 9.

This could be an accidental discovery while working out the engineering problems of detecting interstellar transmissions for an advanced SETI project.

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    $\begingroup$ But the it will be difficult to find a reason for doing this BEFORE noticing time is out of tune. $\endgroup$
    – trikPu
    Nov 16, 2021 at 14:54
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    $\begingroup$ @trikPu astronauts will like to listen to Earth's FM radios (highly unlikely I know - ignoring the ridiculously weak signal they produce - but bear with me). Based on the time delay they know what year's transmissions to expect. When the transmission is younger than expected, someone is bound to notice. $\endgroup$ Nov 16, 2021 at 15:42
  • $\begingroup$ @JohnDvorak - if people were following broadcast football from 4.5 years earlier and you arrived in year 9 with knowledge of the events from year 10, you could make a lot of money gambling. $\endgroup$
    – Willk
    Nov 16, 2021 at 15:54
  • $\begingroup$ @Willk pretty sure that loophole is going to be closed as soon as the wormhole exists. Time delay or not. The real question is - why not use the wormhole for all of our signal transmissions as it is million times easier and has no time delay, except for the obvious out of universe reasons? Subscription fees on Wormholenet, I'm thinking. $\endgroup$ Nov 16, 2021 at 15:59
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    $\begingroup$ Using a radio telescope to listen to old radio broadcast would be such a nerd thing to do. Utterly pointless, but sooo cool. $\endgroup$ Nov 17, 2021 at 8:40
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Pulsars

If you measure a set of regular pulsar signals they will have a set beat at a given point in space. If you know where you are to a reasonable degree of accuracy and can see the selected stars you can tell the time by the rhythm you see in the pulse of those stars. It's a clock and calendar that works anywhere in the universe. It's not perfect though, on a long enough timeline the beat does eventually loop. In fact if you aren't using a large enough sample set it loops quite regularly. So you could potentially have a time displacement that was exactly the length of the loop and think you hadn't taken any time at all to travel.

HDE's answer is simpler and works quite well if you're only dealing with Sol-Centauri. I needed a clock that worked far farther afield.

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    $\begingroup$ This. Observing pulsars would probably be one of the first scientific experiments they would do, as it allows precise positioning in space, both by timing and by angular location. When the timing is off but angular results are accurate, further experimentation will reveal the time travel truth. $\endgroup$
    – jpa
    Nov 17, 2021 at 10:49
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My question is this: how would people detect the 1 year time jump?

if you send it directly between the star systems not using the wormhole (sol to A-Centauri or vise-versa), it will take the 4.5 or so lightyears

This means that if I sit on the Sol side of the wormhole, and I send a signal through it, I would hear that signal again after 5.5 years (1 year due to wormhole, 4.5 years for normal travel from AC to Sol).

That will raise some eyebrows, as scientists will know AC is 4.5ly away.

When you come back, you are 1 year in the past (relative to A-Cent).

Furthermore, if you repeat the same experiment while sitting on the AC side of the wormhole, it will take 3.5 years to hear the signal again (-1 year due to wormhole, 4.5 years for normal travel from Sol to AC).

While the first test may have been shrugged off as some unexplained delay (e.g. the signal passed through some obstacle like a gas cloud at a speed lower than the speed of light), this second test would raise major eyebrows, as it seems to suggest that the signal traveled faster than the speed of light (4.5ly in 3.5 years), which is a big thing to discover and will not be shrugged off.

After that, further refined testing could be done to explain how this signal managed to reach back in only 3.5 years of time. There are several ways to do this: star positioning, elemental decay, some sort of permanent radio transmission which allows you to figure out what time it is (relative to the source of the transmission), celestial events that are observable from both Sol and AC and whose distance to both is known precisely, ...

These refined tests are very niche and not something you would naturally stumble upon, but the initial observation I mentioned is something that you could serendipitously stumble upon (e.g. if a certain event caused a very unique signal, and some random protagonist just happens to record the loopback after 3.5 years and then realizes it's only been 3.5 years since "the event", thus triggering them to contact others about their findings)

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Novas

Occasionally stars go boom. This is visible from a long way off. Adjusting for the fact that either Earth or AC is closer to the source is easily done.

Soon after astronomy takes off on AC, people will notice that the nova list is wrong.

Imagine this: In year X a Nova goes off uncomfortably close to Earth. Critical medical equipment malfunction, major internet disruptions etc.

This Nova is closer to Earth, so we know the wave front will hit AC later, year X+3.

Close to that date, scientists are preparing to open your wormhole. They realize the Nova wave front will do nasty things to the other end of the wormhole and probably make the whole thing collapse.

So, they wait until just after the critical date.

Everything is all good and nice, until eleven and a half months later...

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I would like to add that depending on the understanding of spacetime and wormhole physics in your story and the origin of the wormhole, you don't have to think about the problem that it would be unreasonable to measure your position in spacetime without apparent reason, which would then result in the detection of a time offset. The reason for that is pretty simple as given our understanding of it, we simply don't know for sure how time would pass for us in the wormhole relative to the outside and as well the endpoint of the wormhole will probably be unknown, so it would be quite natural to make the measurement locating you in space and as well compare this to the predicted location of stars relative to earth relative to the position entering the wormhole to detect your position in time.

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When you get to AC, you would turn on your radio or TV and tune in to an Earth station. You'd be seeing sports games from the wrong year, or the wrong season of your favorite TV show. Normally you'd be expecting 4.5 year old shows. Instead you'd be seeing 5.5 year old shows.

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In addition to the above Atomic clocks carried by vessels traveling back and forth to either system would reveal the discrepancy after each transition. A simple 'time check' i.e. comparing elapsed time on the ship that has just arrived with any other atomic clock in the Alpha C system would reveal that an extra year has elapsed.

Accurate clocks are essential for accurate navigation and in space there are always subtle relativistic effects to taken into account during space flight, even if its just in Earth orbit. In this case those effects would be amplified by the relative velocities of Sol and Alpha C and any acceleration/deceleration involved in the trip out to the wormhole from Earth and then again upon arrival at the other end so an accurate clock that can adjust for time dilation effects would be essential. And since even today atomic clocks are used in space craft and satellite navigation any crewed ship will almost certainly carry one.

Also (although its not mentioned) the problem would become apparent the moment the first probe or ship ever went through the wormhole. Scientist would be sitting on tenterhooks back home waiting for the first lot of data to arrive and wondering why it took exactly 2 years to get here. Any subsequent messages or probes would show exactly the same time delay. So it would probably be obvious before the first humans ever even set foot in the Alpha C system.

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  • $\begingroup$ How did any other atomic clock get to the Alpha C system? $\endgroup$
    – user253751
    Nov 16, 2021 at 12:36
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    $\begingroup$ An atomic clock would detect any relativistic effects experienced by a ship carrying the clock, (when compared to another clock it had been calibrated with) but how would the clock detect an instant timeslip? Why would probe data take two years to return to Earth? Data beamed back directly to Earth (not through the wormhole) would take an extra year to arrive (so 5.38 years instead of 4.38), but travel though the wormhole is instantaneous. Going back through the wormhole returns it to the time it left, regardless of direction (+1 year going to AC, -1 year returning from). $\endgroup$ Nov 16, 2021 at 14:23
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    $\begingroup$ Point (1) The scenario doesn't specify that this is the first trip to the system using the wormhole, just a/any trip! Point (2) You'd only detect the time difference by comparison to another separate clock that was already in the Alpha C system when you arrived. This in turn would have to be calibrated (ideally with the original clock back in Sol) independently of the wormhole i.e. via 'normal space'. So three clocks would be required. Your comparing 'your' travel time to two linked clocks 4.5 light years apart. And sorry I read the delay as being the same both ways i.e. 2 years. $\endgroup$
    – Mon
    Nov 16, 2021 at 23:33

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