Time Travel... the fly in the ointment

[Keith&Co.]

A couple of authors have also worked with the idea of the expanding universe.
The universe, and everything in it, was smaller in the Before Time. So time travelers going backwards show up as giants, though they adapt over time. The laws of physics adjust the matter of their make-up to fit in. Time travelers going forwards a midgets or Lilliputians, until they adjust.

In Crichton's Timeline, the first thing the machine does is shrink travelers to the appropriate size for the time they're targeting.

 

[Earl IV]

We're all time travelling right now, at a rate of 1 second per second.

 

[barbos]

A couple of authors have also worked with the idea of the expanding universe.
The universe, and everything in it, was smaller in the Before Time. So time travelers going backwards show up as giants, though they adapt over time. The laws of physics adjust the matter of their make-up to fit in. Time travelers going forwards a midgets or Lilliputians, until they adjust.

In Crichton's Timeline, the first thing the machine does is shrink travelers to the appropriate size for the time they're targeting.

Universe is expanding, but people and other things in it are not, they stay the same size.
As for OP, time travel is impossible but if it were possible I am pretty sure they would be able to dial any position or rather any event in space-time history, or basically point to a material object and say 10 days ago near that object.

 

[PyramidHead]

As other posters have said, the problem isn't merely that the earth will have moved in its orbit around the sun, but the solar system will have moved relative to the galactic center, the galaxy relative to the local cluster, etc. etc. etc.

It could be resolved in science fiction stories by depicting the technology not so much as a time travel machine, but a machine that lets the user pick a set of space-time coordinates relative to some arbitrary point, and travel there via some kind of higher-dimensional transportation.

The movie Primer did it a little differently: the time machines were tethered to a specific isolated location (a coffin-like sealed box), and the user had to remain in that location for however long in the past he wanted to go. There would be no risk of ending up in deep space, since the time machine itself, and its contents, would always be in a storage unit in a warehouse on earth.

 

[Keith&Co.]

Universe is expanding, but people and other things in it are not, they stay the same size.

how do you know that for sure?
if everything in the universe were expanding, all our yardsticks would be expanding, too.

 

[barbos]

Universe is expanding, but people and other things in it are not, they stay the same size.

how do you know that for sure?
if everything in the universe were expanding, all our yardsticks would be expanding, too.

Size of yardstick depends on physical constants, and we are pretty sure they are not moving, because we can look at distant galaxies and see that laws of physics are the same.

 

[Keith&Co.]

how do you know that for sure?
if everything in the universe were expanding, all our yardsticks would be expanding, too.

Size of yardstick depends on physical constants, and we are pretty sure they are not moving, because we can look at distant galaxies and see that laws of physics are the same.

You're still using measurements inside the universe to tell if the universe is changing. If the constants aren't, but are changing consistently with everything else, how would you know?

 

[Peez]

I think that the old 'what happens if you kill your father/mother before you were conceived' problem is a bigger issue with backward time travel.

That and grammar.

Peez

Yes, but you can have the position problem even when you only have backwards communication.

I am not sure that communication would be any different. The example of 'killing your parents' is often expressed because the effect is so obvious to us, but any communication with the past could alter events and create a 'temporal paradox'. Even without any change in the past (something of a contradiction in terms, actually) that influences the 'temporal communication', there is arguably a logical problem if a single atom is changed in any way.

Peez

 

[Peez]

I think that the old 'what happens if you kill your father/mother before you were conceived' problem is a bigger issue with backward time travel.

That and grammar.

Peez

Yes, but you can have the position problem even when you only have backwards communication.

Anyhow, you did not address the grammatical issues.

One of the major problems encountered in time travel is not that of becoming your own father or mother. There is no problem in becoming your own father or mother that a broad-minded and well-adjusted family can't cope with. There is no problem with changing the course of history—the course of history does not change because it all fits together like a jigsaw. All the important changes have happened before the things they were supposed to change and it all sorts itself out in the end.

The major problem is simply one of grammar, and the main work to consult in this matter is Dr. Dan Streetmentioner's Time Traveler's Handbook of 1001 Tense Formations. It will tell you, for instance, how to describe something that was about to happen to you in the past before you avoided it by time-jumping forward two days in order to avoid it. The event will be descibed differently according to whether you are talking about it from the standpoint of your own natural time, from a time in the further future, or a time in the further past and is futher complicated by the possibility of conducting conversations while you are actually traveling from one time to another with the intention of becoming your own mother or father.

Most readers get as far as the Future Semiconditionally Modified Subinverted Plagal Past Subjunctive Intentional before giving up; and in fact in later aditions of the book all pages beyond this point have been left blank to save on printing costs.

The Hitchhiker's Guide to the Galaxy skips lightly over this tangle of academic abstraction, pausing only to note that the term "Future Perfect" has been abandoned since it was discovered not to be.

- from Restaurant at the End of the Universe (Chapter 15).

Peez

 

[barbos]

Size of yardstick depends on physical constants, and we are pretty sure they are not moving, because we can look at distant galaxies and see that laws of physics are the same.

You're still using measurements inside the universe to tell if the universe is changing. If the constants aren't, but are changing consistently with everything else, how would you know?

I can extend your logic further and speculate that we can't know anything for certain and Universe was created a second before I posted this post.
What you suggest is not testable.

We believe that rational and minimalistic interpretation of the available ultra-deep space observations is that constants are constant and physical laws have not been changing.

Also, in you scenario where everything expands proportionally we would not have been able to detect universe expansion at all.

 

[Loren Pechtel]

We're all time travelling right now, at a rate of 1 second per second.

I'd like to have a word with you about that.

--Einstein

 

[Shadowy Man]

In Crichton's Timeline, the first thing the machine does is shrink travelers to the appropriate size for the time they're targeting.

The physics in Timeline was so bad I nearly couldn't finish the book. I actually tossed it out of my hands after reading one bit of physics explanation; however, I don't recall what it was and I have no inclination to read it again to find out what it was.

Unlike some of Crichton's earlier books that I Liked, this book read like a movie script.

 

[Perspicuo]

I so wish I understood physics better.

For me, Star Trek level sci-fi suffices.

Time travel? All you have to do is swoosh your ship around a star and you're back 3 centuries. Just watch out for the flying scupltures of your shipmates and psychedelic swirls of color. Need to come back to your time? Swoosh your ship around the same star in the opposite direction!

See? Sciencing is easy.

 

[Bronzeage]

I so wish I understood physics better.

Better than what? Without a frame of reference, your desire is undefined.

 

[skepticalbip]

I so wish I understood physics better.

For me, Star Trek level sci-fi suffices.

Time travel? All you have to do is swoosh your ship around a star and you're back 3 centuries. Just watch out for the flying scupltures of your shipmates and psychedelic swirls of color. Need to come back to your time? Swoosh your ship around the same star in the opposite direction!

See? Sciencing is easy.

The swooshing around a star for time travel bothers me. However, I kinda like some of the Star Trek sci-fi too. Most of it they don’t try to explain. It is in the explanation that much of sci-fi fails. Star trek doesn’t try to explain warp drive, what a phaser is or how the stun setting works, the transporter, how power is extracted from dilithium crystals, etc. All simply work using future science so no one can dispute the explanation since there isn’t one.

H.G. Wells did the same in his “Time Machine”. The reader wasn’t worried about how it worked since no explanation was offered so the reader can focus on the story.

“Captain Gron settled into the helm’s custom seat and engaged the SLUTT* drive after setting the coordinates to 16 July 1943” is more satisfactory for me than reading a physics explanation of how time travel works that clearly contradicts physical laws.

*SLUTT – Sikorsky-Lockheed Universal Temporal Transport.

 

[Perspicuo]

For me, Star Trek level sci-fi suffices.

Time travel? All you have to do is swoosh your ship around a star and you're back 3 centuries. Just watch out for the flying scupltures of your shipmates and psychedelic swirls of color. Need to come back to your time? Swoosh your ship around the same star in the opposite direction!

See? Sciencing is easy.

The swooshing around a star for time travel bothers me. However, I kinda like some of the Star Trek sci-fi too. Most of it they don’t try to explain. It is in the explanation that much of sci-fi fails. Star trek doesn’t try to explain warp drive, what a phaser is or how the stun setting works, the transporter, how power is extracted from dilithium crystals, etc. All simply work using future science so no one can dispute the explanation since there isn’t one.

H.G. Wells did the same in his “Time Machine”. The reader wasn’t worried about how it worked since no explanation was offered so the reader can focus on the story.

“Captain Gron settled into the helm’s custom seat and engaged the SLUTT* drive after setting the coordinates to 16 July 1943” is more satisfactory for me than reading a physics explanation of how time travel works that clearly contradicts physical laws.

*SLUTT – Sikorsky-Lockheed Universal Temporal Transport.

Trek "engineering" is offered in order to give the feeling of that commode with nacelles actually moving through the galaxy. And it works, because apparently Star Trek tech manuals sell real well. Once they start wanting to know more, you know the illusion worked.

 

[Kharakov]

Well, at least Kip Thorne distanced himself from the pseudoscience in Interstellar:

The issue of time travel is one. There’s been a lot of research that’s been done on whether the laws of physics permit travel back in time or not, and we’ve got interesting results but no firm answers. In that area Chris made his own rule set, which we discussed at length when he described it to me early last year. And it’s a rule set for which I then could find a scientific rationale, but it was a rule set that was much less constrained by the laws of physics because we don’t understand the laws of physics in that domain yet!

Uhh... which reminds of bilby's fallacy.

 

[DBT]

Our time machine should be bound by gravity while it moves backward at whatever the set rate,

Ah, but the effect of gravity is acceleration per second per second. A time machine would change the value of a second, altering or removing gravity's affect on the time machine.

Time is relative anyway, gravity/warped space/time determining orbital mechanics, object and their trajectories, escape velocity, etc. If our proposed time machine is bound by gravity, it probably remains within the Earths gravity well at all times.

 

[Malintent]

For whatever reason, I was thinking about time travel. You hear about time travel, going from one time to another, but it occurred to me about one other thing, which I don't recall ever hearing about in a tv program. Time and space are linked, no?

So if one were to go back in time, wouldn't they be limited to when the position they are currently in, is relatively the same? IE, if you go back in time from your position, to six months ago, aren't you royally fucked as Earth is located on the other side of the sun? Heck, wouldn't just a minute put you in great danger as well?

Your issue is also your solution... If time and space are one fabric, then moving through time would also move you through space. Problem solved.

 

[untermensche]

Not a fly in the ointment.

The fly in the bowl of flies.

To return to the past implies the past is out there somewhere, every instant of it, just sitting there somehow waiting so that it can be returned to.

To return to the past is to bring matter that already existed in the past to the past. To create matter or perform some amazing magic with matter in other words.

It is a human fantasy and there is no physics to describe moving to the past.

What can we do to objects like humans?

We can apply forces to them or to something that contains them.

What force can we apply to push an object towards the past?