This is much too close to being a personal attack for this forum. Please be careful about tone and personal vitriol in IMHO. No warning issued.
RickJay
Moderator
I’m down as a “Probably Not” (I’d prefer a solid “maybe”). It’s quite likely we don’t understand the laws of physics as well as we think we do - but even if we don’t, that doesn’t mean that the correct laws of physics don’t also prohibit useful things like time travel and FTL.
The opinion he drew may have reflected ignorance, but the fact he stated was absolutely true.
Many things were impossible until we developed the tools to observe and analyze them.
AM radio signals have existed on Earth as long as there has been lightning. It wasn’t until the 1860’s that J.C. Maxwell created a new era of physics when he unified magnetism, electricity and light. Maxwell’s four laws of electrodynamics (“Maxwell’s Equations”) eventually led to electric power, radios, and television.
It wasn’t until 1894 that Guglielmo Marconi demonstrated the first practical radio transmitter/receiver.
Not a real fan of Wikipedia, but cite.
It is the ultimate hubris to state that because we can’t formulate how it can be done now therefore no one ever will.
I agree that time travel backwards is extremely unlikely due to the previously mentioned lack of people showing up out of time. Unless you also posit that the Time Patrol is exceptionally excellent at their jobs.
FTL, I’m less convinced of it’s impossibility. There’s just too much math and science left to do.
I feel that our body of knowledge has crossed a boundary. It used to be we said something was impossible because we don’t understand how it worked. Now when we say something is impossible it’s generally because we do understand how it works.
There are whole fields of speculative technology where we don’t know how to do things: artificial intelligence, fusion power, genetic engineering, nanotechnology, programmable matter, etc. But people aren’t saying they’re impossible.
But people are saying faster-than-light travel and time travel are impossible. And they’re not speaking out of ignorance. They’re saying we now understand these things well enough to know they are impossible.
Unless you had time travel that could only travel back to the time when the machine exists.
The wormhole accelerated to relativistic speeds trick (your chronologists will hate this) is once such example.
We don’t need FLT in order to spread out across the galaxy. I like your optimism that we are destined to get off this rock though.
Problem with that is that you are essentially invoking a new universe that has you appear within it at your preferred space-time destination.
Now you have the Transporter problem. Not such a big deal if you don’t care about continuity of consciousness and multiverse cloning, but it still gets a bit weird. Especially the part where you confirm that you have created your copy in a new universe, and now in order to complete the transport, you have to disintegrate yourself.
As our knowledge of the universe is refined, I suspect we will only find more ways of answering “No” to the question of FTL and time travel.
All proposed ways involve using forces we do not know how to control and matter we don’t think that exists, and then relies on math to hold up under conditions that it has never been tested in.
We have few technologies that nature did not demonstrate to us first. We have refined them and made them our own, but we did so after seeing it done, and finding a way to emulate it.
If we do find a way of creating temporal clones using time machines, I see no reason to disintegrate the original. Just get used to the fact that you now exist in more than one instance.
If you could create a wormhole back into the past, you would need to invoke one of two models.
1/ Either your actions in the past would be confined to one single timeline of eventm the one which has already happened; this is so-called Novikov consistency, and it means you really don’t have any free will. If you are trying to change the past,it can’t be done.
2/ Alternately you go back through the wormhole and find you can change the past, but this creates a completely new timeline with different events. The interesting thing to me is that (assuming you kept the connecting wormhole open) you can still travel back to the original timeline through that hole. In effect, you have created a wormhole that connects between parallel universes, each with its own history. Create some more wormholes, and you have a transport network that connects to a plethora of different histories. It is entirely possible to encounter different versions of yourself in each timeline. No-one has to be disintegrated; although once you get to know yourself better you might get the urge to commit murder. Or is it suicide?
Science often progresses from speculative theory to provable theory to practical applications (although not always in that order). I still have hope for a practical infinite improbability drive.
That particular method of time travel means that you do not exist in this universe in more than one instance. It means that there is another universe that has a you in it.
That doesn’t do you much good. You didn’t travel anywhere, and you don’t get to experience whatever it is that you wanted to experience by traveling time, someone else does.
The disintegrate yourself part is just the running joke about the last step of the transporter.
And that follows the two different conjectures as to the nature of time. The first assumes that time is a static thing, eternally existing in the past and the future. We experience now only because we are beings embedded in space time who are experience now. The second it that now only exists now, and that all other times are malleable.
I don’t know if physics will ever answer the question of which universe we live in, I lean towards the first.
Either way, though, the past is defined as having a lower entropy than the future, and I suspect that as we learn more about the universe, the second law of thermodynamics will be key in putting the final nail in the coffin of time travel. You cannot move to a time of lower entropy.
As long as the increasing entropy rule is followed, there may be some loophole that lets us get around the speed of light (though I doubt it), but you would never be able to travel into the past, as that is an uphill battle with entropy.
I would have voted for “almost certainly not”, if that had been an option.
Wondermark first came to my attention a couple of weeks ago and that is one of my favorite strips so far. I’ve bookmarked the dead tree versions for the next time my wife and kids are asking what I want for my birthday.
I understand what you’re saying and to some extent agree. But I could hop on my timeship and have almost exactly the same conversation with some highly educated scholars over tea and scones in 1700.
Like my 17th century scholars, they have reached their conclusions based on the data they have available. We’ll just have to see what the next century uncovers. My kids will anyway. I’m only good for another 50 years or so.
Ultimately, my hope that it is possible is no more damaging to to you than your belief that it is impossible is to me so we can amicably agree to disagree.
The analogy I use is about yelling.
Challenge Archimedes to invent a device that allows a man yelling in Athens to be heard in Thebes. Archimedes, brilliant as he was, might be able to prove conclusively that that’s impossible: examine the human vocal cords, test the loudest shouter you can find with the keenest ear you can find, measure the distance over which the listener can hear the shout, compare that to the distance between Athens and Thebes, and then modify for the largest theoretical megaphone. Absolutely impossible for a man shouting in Athens to be heard in Thebes.
Ask him if a man whispering in Athens could be heard by a man on the other side of the planet, and he’d likely punch you for wasting his time.
Archimedes didn’t know about telephones.
Using today’s technology, no: I don’t think we’ll ever create a fuel-burning engine that can propel mass through space faster than light travels through space.
But I don’t know what we’ll invent instead. I don’t know what equivalent of the telephone we’ll invent to solve the equivalent of being heard across great distances.
There may not be a solution to the problem, but I’m not gonna bet on that.
My simple way of looking at it is that special relativity tells us a lot more than placing an upper bound on the speed of matter or information. It defines the fundamental nature of space and time, and in particular, the fact that any two points separated in space are also separated in time, and the separation in time is defined by the speed of light.
A photon experiences no time. A photon emerging from the sun and impinging on the six eyeballs of an alien astronomer 1000 light-years away took 1000 earth years to get there from our frame of reference, but it was instantaneous from the photon’s frame of reference. You can’t get from “A” to “B” faster than “instantly” in proper time. If you try to work out the time dilation factor (the Lorentz factor) for a clock observed with relative velocity v, it involves the term SQRT(1-(v[sup]2[/sup]/c[sup]2[/sup])). If v is greater than c, you’re now dealing with an imaginary number, the square root of a negative. You can, if you like, pervert the equation so that the Lorentz factor is negative, and the observer sees the clock running backwards.
This leads to the following highly scientific analysis: 
*“There was a young lady named Bright,
Who could travel much faster than light;
She departed one day
In a relative way,
And returned on the previous night.” *
My contention is that no wormhole “shortcut”, Alcubierre drive, or anything else is going to change this fundamental nature of spacetime. If you were to travel from point A to point B faster than light, no matter how you did it, unless our understanding of special relativity is extremely flawed, it appears that you would arrive in the past. Furthermore, if you returned the same way, you would arrive before you left. I can accept that there is a great deal that science doesn’t know about the universe, some of it likely very fundamental, but I’m skeptical that the reversal of causality – of cause and effect – is one of them.
^^^ This.
I checked “probably” because our understanding of science could conceivably be inadequate in some way that we don’t realize… but that’s unlikely.
In the case of time travel, the concept doesn’t make sense once we think of time as a dimension. In science fiction “time travel” is where someone continues to have linear experience but gets repositioned into the past or the future. It’s that “continues to have linear experience” that makes it look absolutely impossible. It requires time itself to have two behaviors, one for the backdrop-universe in which the time traveler is traveling and a different one for the time traveler. I tend to view the four-dimensional universe as a latticework structure of events; if you slide the slider to 1847, you’re looking at the state-of-universe as it was in 1847 and “you” (the potential time traveler) are nonexistent at that coordinate. To move you to it, the whole structure has to change so that now you do exist there, but if that happened, there’s no reason to think you-the-experiencing-conscious-person would experience 1847 as taking place after 2025 when you get into your time-travel apparatus.
I had a co-worker who smoked. I got into a conversation with her one time about smoking. She explained that some people believe that smoking was bad for you and some don’t believe that smoking is bad for you. And she said she was one of the people who didn’t believe it so she smoked.
You can probably see the problem in her reasoning. Science is about facts not beliefs. Smoking is bad for you even if you don’t believe in the science.
On the subjects of faster-than-light travel and time travel, you’re right; your belief or disbelief will probably never have any effects on me or anyone else. But on other issues like climate change and Covid19 and vaccination, we’ve seen how some people who feel that science is just a matter of opinion that you can take or leave cause problems for the rest of us.
I suspect time travel into the future will absolutely be a thing. TT to the past & FTL, probably not.
And this will be blaring on the stereo.
:flees:
The Alcubierre metric and the family of Kerr-type metrics are all solutions to the Einstein field equations of general relativity. There is no paradox or conflict with relativity physics as we know it, although whether they are physically realizable is another question entirely; I suspect the answer is “no”, and certainly not without introducing new particles or effective field theories that allow for an understanding of how to directly manipulate spacetime in order to achieve the extreme gradients required. There is also nothing in relativity theory that prohibits exiting the universe as we know it and reentering in another locale via some kind of extra-dimensional space although there is also zero observational evidence or theoretical underpinning for this common contrivance of science fiction.
Causality and locality are purely assumptions and ones that even a casual understanding of quantum mechanics casts into doubt on a fundamental level. We know that one or both of these basic axioms does not work at the level of quantum interactions, although whether we can use that to send even information (much less objects or people) beyond the intersecting lightcones of different reference frames is another question entirely.
All special relativity says about the motion of objects is that there are no privileged frames of reference, that the speed of massless particles like photons is exactly c, and that all objects have to move at some rate through spacetime that totals up to c, with objects that have mass having some spatial component of velocity that is somewhat less than c in any reference frame. Of course, there are many objects in space that have a distance much greater than would be allowed by the speed of light–most of the visible universe, in fact–because spacetime itself is expanding, and presumably more that has an apparent velocity away from us that exceeds c, although we cannot see the light from that part of the universe for obvious reasons. So, not only is it possible to travel (effectively) faster than light, we have observational evidence for it. What we do not have is a good explanation for why this is happening (beyond the label of “dark energy”) or how or even if we could create such an effect ourselves.
Stranger
I posted the following on FB several months back.
What refutes science
- Better science
What doesn’t refute science
- Your feelings
- Your religion
- Your favorite politician
- Your half-baked opinion after watching two YouTube videos
I’ve only stated a hope that someone cooks up some better math/science that says FTL can work.