Stories
Slash Boxes
Comments

SoylentNews is people

posted by martyb on Saturday September 26 2020, @06:20AM   Printer-friendly
from the "Back-to-the-Future"-cannot-not-happen dept.

Young physicist 'squares the numbers' on time travel:

Paradox-free time travel is theoretically possible, according to the mathematical modelling of a prodigious University of Queensland undergraduate student.

Fourth-year Bachelor of Advanced Science (Honours) student Germain Tobar has been investigating the possibility of time travel, under the supervision of UQ physicist Dr Fabio Costa.

"Classical dynamics says if you know the state of a system at a particular time, this can tell us the entire history of the system," Mr Tobar said.

[...] "For example, if I know the current position and velocity of an object falling under the force of gravity, I can calculate where it will be at any time.

"However, Einstein's theory of general relativity predicts the existence of time loops or time travel -- where an event can be both in the past and future of itself -- theoretically turning the study of dynamics on its head."

[...] "I wondered: "is time travel mathematically possible?"

Mr Tobar and Dr Costa say they have found a way to "square the numbers" and Dr Costa said the calculations could have fascinating consequences for science.

"The maths checks out -- and the results are the stuff of science fiction," Dr Costa said.

[...] "Try as you might to create a paradox, the events will always adjust themselves, to avoid any inconsistency.

"The range of mathematical processes we discovered show that time travel with free will is logically possible in our universe without any paradox."

Journal Reference:
Germain Tobar, Fabio Costa. Reversible dynamics with closed time-like curves and freedom of choice - IOPscience, Classical and Quantum Gravity (DOI: 10.1088/1361-6382/aba4bc)


Original Submission

This discussion has been archived. No new comments can be posted.
Display Options Threshold/Breakthrough Mark All as Read Mark All as Unread
The Fine Print: The following comments are owned by whoever posted them. We are not responsible for them in any way.
(1)
  • (Score: 0) by Anonymous Coward on Saturday September 26 2020, @06:27AM (7 children)

    by Anonymous Coward on Saturday September 26 2020, @06:27AM (#1057134)

    One thing the old physicists can't stand is a smart-ass.

    • (Score: 3, Touché) by c0lo on Saturday September 26 2020, @06:56AM

      by c0lo (156) Subscriber Badge on Saturday September 26 2020, @06:56AM (#1057138) Journal

      Lucky him, he's into maths.

      --
      https://www.youtube.com/watch?v=aoFiw2jMy-0 https://soylentnews.org/~MichaelDavidCrawford
    • (Score: 0) by Anonymous Coward on Saturday September 26 2020, @09:11AM (5 children)

      by Anonymous Coward on Saturday September 26 2020, @09:11AM (#1057172)

      Tobar can just time travel to the past and fuck their mothers.

      • (Score: 2) by choose another one on Saturday September 26 2020, @10:42AM (4 children)

        by choose another one (515) Subscriber Badge on Saturday September 26 2020, @10:42AM (#1057195)

        I think the point of his work is not that he _can_, but that he already did...

        • (Score: 0) by Anonymous Coward on Saturday September 26 2020, @11:50AM

          by Anonymous Coward on Saturday September 26 2020, @11:50AM (#1057206)

          But if he already did, can he still decide not to?

        • (Score: 2) by sjames on Saturday September 26 2020, @04:14PM (2 children)

          by sjames (2882) on Saturday September 26 2020, @04:14PM (#1057298) Journal

          Time travel makes such a sash of tenses. I believe it should be: "He already will have" or is it "He already will had".

          • (Score: 2) by JoeMerchant on Saturday September 26 2020, @06:31PM

            by JoeMerchant (3937) on Saturday September 26 2020, @06:31PM (#1057335)

            I believe with time travel language will have to treat time as a 4th dimension and any meaningful descriptions of events involving departure from time's arrow will simple "be" or "is." He exists because he fucked his mother, not in the future or the past, he just did - see diagram for further clarification. Kind of like mechanical engineers have to resort to drawings to really communicate anything more complex than a part number in a catalog.

            --
            🌻🌻 [google.com]
          • (Score: 2) by hendrikboom on Monday September 28 2020, @02:07AM

            by hendrikboom (1125) Subscriber Badge on Monday September 28 2020, @02:07AM (#1057991) Homepage Journal

            Don't have done that!

  • (Score: 0) by Anonymous Coward on Saturday September 26 2020, @07:26AM (9 children)

    by Anonymous Coward on Saturday September 26 2020, @07:26AM (#1057146)
    Germain Tobar is quoted as saying:

    "Classical dynamics says if you know the state of a system at a particular time, this can tell us the entire history of the system," Mr Tobar said. [...] "For example, if I know the current position and velocity of an object falling under the force of gravity, I can calculate where it will be at any time.

    I don't think this is correct. For example, the dynamics of a 3-body system is inherently chaotic, and there is no known closed-form solution to the dynamics. It is possible to simulate the system dynamics, but it is not possible predict forwards or backwards "the entire history of the system" to calculate perfectly from a state of the system at any particular time to the state at a different time; perfect calculation of the state would require infinite precision measurements.

    • (Score: 3, Interesting) by Anonymous Coward on Saturday September 26 2020, @08:40AM

      by Anonymous Coward on Saturday September 26 2020, @08:40AM (#1057159)

      yes, infinite precision measurements is what they are talking about.

      there are differential equations for which
      1 a unique explicit solution exists (i.e. you can write it down and then compute it for arbirtrary times).
      2 a unique smooth solution is known to exist for any initial condition, but you cannot write it down as a simple expression you can compute.
      3 no unique smooth solutions exist (they do not have "unique" solutions in the intuitive sense).

      as far as mathematical proofs are concerned, a lot of the techniques valid for 1 are also valid for 2.
      but it is true that in practice measurement errors often mean that the distinction between 2 and 3 is less obvious.

      in the case of this work, it's pure math, so "measurement precision" does not apply and the closeness of 1 and 2 is relevant.

    • (Score: 3, Insightful) by shortscreen on Saturday September 26 2020, @09:34AM (6 children)

      by shortscreen (2252) on Saturday September 26 2020, @09:34AM (#1057182) Journal

      Doesn't quantum mechanics blow away the idea of purely deterministic physics? Even before you have to worry about whether two different past states could lead to the same future state?

      • (Score: 4, Insightful) by qzm on Saturday September 26 2020, @11:20AM (4 children)

        by qzm (3260) on Saturday September 26 2020, @11:20AM (#1057200)

        Yes, it does.

        This is not any form of physical proof, it is just mathematics navel gazing, with no actual impact on reality.

        Such classical physics has not been tied physical reality for a LONG time.

        • (Score: 0) by Anonymous Coward on Saturday September 26 2020, @11:42AM

          by Anonymous Coward on Saturday September 26 2020, @11:42AM (#1057204)

          Of course, but so started Einstein's theories and just about all modern physics. Does this but if math mean anything? Maybe one day we will find out. No need to be overly rude about it.

          By the way, do you know the author's name of that children's book series from a while back with a bear family that lived in a tree?

        • (Score: 2) by JoeMerchant on Saturday September 26 2020, @01:16PM (1 child)

          by JoeMerchant (3937) on Saturday September 26 2020, @01:16PM (#1057232)

          Classical physics explains a lot very well: Newton's apple, the orbital mechanics that interplanetary spacecraft use to plan trajectories, even some basic thermodynamics is well modeled while maintaining a blind eye to chaos.

          Classical physics is a huge step forward from: "The cannonball will obviously fall faster than a musketball due to its size." Of course, the cannonball does actually attract the earth to itself proportionally faster than the musketball does, but 10e-43 vs 10e-45 is hard to notice vs 1.0 plus chaotic noise on the order of 10e-20.

          --
          🌻🌻 [google.com]
          • (Score: 0) by Anonymous Coward on Saturday September 26 2020, @02:58PM

            by Anonymous Coward on Saturday September 26 2020, @02:58PM (#1057270)

            Classical physics is a huge step forward from: "The cannonball will obviously fall faster than a musketball due to its size." Of course, the cannonball does actually attract the earth to itself proportionally faster than the musketball does, but 10e-43 vs 10e-45 is hard to notice vs 1.0 plus chaotic noise on the order of 10e-20.

            Its a standard example in grade school that a cannonball and feather fall at the same rate.

            https://moon.nasa.gov/resources/331/the-apollo-15-hammer-feather-drop/ [nasa.gov]

        • (Score: 0) by Anonymous Coward on Saturday September 26 2020, @02:55PM

          by Anonymous Coward on Saturday September 26 2020, @02:55PM (#1057269)

          QM doesn't do any such thing. If I knew all the forces on a coin when it was flipped I could tell you whether it will land tails or heads every time. But in the absence of that info I can still say something useful by modelling it as a bernoulli trial with p = 0.5 and studying what sort of phenomena that entails. QM is like the latter.

          https://en.m.wikipedia.org/wiki/Bernoulli_trial [wikipedia.org]

          The problem with determinism is you need to know the state of the system with infinite precision to use it.

      • (Score: 2) by sjames on Saturday September 26 2020, @04:20PM

        by sjames (2882) on Saturday September 26 2020, @04:20PM (#1057301) Journal

        Yes, but this isn't physics, it's math. The question need not have anything to do with the real world. It doesn't ask any questions about what our reality permits, it asks if the question is even logical in the first place. That is, could any physics ever permit this?

    • (Score: 3, Insightful) by JoeMerchant on Saturday September 26 2020, @01:09PM

      by JoeMerchant (3937) on Saturday September 26 2020, @01:09PM (#1057229)

      Classical dynamics does not acknowledge chaos as an insurmountable barrier, classical dynamics just says: you're not calculating with enough precision. In this regard, classical dynamics has denial issues.

      --
      🌻🌻 [google.com]
  • (Score: 0) by Anonymous Coward on Saturday September 26 2020, @07:31AM (1 child)

    by Anonymous Coward on Saturday September 26 2020, @07:31AM (#1057148)

    How many dimensions your time has?

    • (Score: 1, Funny) by Anonymous Coward on Saturday September 26 2020, @09:28AM

      by Anonymous Coward on Saturday September 26 2020, @09:28AM (#1057179)

      42

  • (Score: 1, Touché) by Anonymous Coward on Saturday September 26 2020, @08:53AM (4 children)

    by Anonymous Coward on Saturday September 26 2020, @08:53AM (#1057165)

    In the, "Biff" timeline, he rules and the world is in chaos.

    I read somewhere the rich Biff was modeled after Trump.

    I believe that's the timeline we're in! How prophetic. We have Trump (rich Biff) for a leader and society is just swirling the drain.

    • (Score: 1, Touché) by Anonymous Coward on Saturday September 26 2020, @09:19AM (1 child)

      by Anonymous Coward on Saturday September 26 2020, @09:19AM (#1057175)

      Back to the Future Part 2 stopped examining the Rich Biff timeline at 1985. It never showed how awesome things became in the 2020s and 2030s. Keep America Great.

      • (Score: 2) by JoeMerchant on Saturday September 26 2020, @01:18PM

        by JoeMerchant (3937) on Saturday September 26 2020, @01:18PM (#1057233)

        Max Max is an awesome timeline, just not one we should aspire to - even if America is still the BEST in the world, as we are able to perceive it.

        --
        🌻🌻 [google.com]
    • (Score: 3, Interesting) by shortscreen on Saturday September 26 2020, @09:19AM (1 child)

      by shortscreen (2252) on Saturday September 26 2020, @09:19AM (#1057176) Journal

      Have you checked whether this is the timeline where your mom has fake boobs?

      • (Score: 1, Touché) by Anonymous Coward on Saturday September 26 2020, @09:40AM

        by Anonymous Coward on Saturday September 26 2020, @09:40AM (#1057185)

        Have you checked whether this is the timeline where your mom has fake boobs?

        We had sex during another timeline and all of us disappeared from the family photo.

  • (Score: 5, Informative) by choose another one on Saturday September 26 2020, @10:55AM (4 children)

    by choose another one (515) Subscriber Badge on Saturday September 26 2020, @10:55AM (#1057197)

    "For example, if I know the current position and velocity of an object"

    I think Heisenberg would like a word - I am pretty sure those are precisely the two things that you _cannot_ know simultaneously...

    • (Score: 2) by nostyle on Saturday September 26 2020, @02:41PM (2 children)

      by nostyle (11497) on Saturday September 26 2020, @02:41PM (#1057259) Journal

      Sorry to be pedantic, but the proper Heisenberg pair you are looking for is "position" and "momentum". And of course velocity has a lot to do with momentum, so you are not far off.

      • (Score: 0) by Anonymous Coward on Sunday September 27 2020, @09:33AM (1 child)

        by Anonymous Coward on Sunday September 27 2020, @09:33AM (#1057587)

        proper Heisenberg pair you are looking for is "position" and "momentum".

        To be pedantic, this is only because of MASSLESS particles. There you know that velocity is c, but you don't know momentum. For massive particles, it's good enough to say velocity and position since m0 is known. Also, you can just change this to analogous versions of uncertainty principle like you can't know the Energy and Time. Here's an explanation as an example,

        http://www.stat.physik.uni-potsdam.de/~pikovsky/teaching/stud_seminar/ajp_uncert_energy_time1.pdf [uni-potsdam.de]

        • (Score: 2) by nostyle on Sunday September 27 2020, @07:59PM

          by nostyle (11497) on Sunday September 27 2020, @07:59PM (#1057766) Journal

          > For massive particles, it's good enough to say velocity and position since m0 is known.

          Not exactly. You will have uncertainty in your measurement of velocity along with uncertainty in your measurement of mass. These uncertainties combine into your uncertainty in measuring momentum.

          Alternatively, you could design an experiment to directly measure momentum, but then you will need to sort the uncertainty of that measurement into uncertainties in your knowledge of mass and velocity.

          Also, given that pi is a transcendental number, I would conjecture that there is no physical quantity that you will ever know with infinite precision.

    • (Score: 0) by Anonymous Coward on Sunday September 27 2020, @03:41PM

      by Anonymous Coward on Sunday September 27 2020, @03:41PM (#1057638)

      Heisenberg is post-classical physics.

  • (Score: 0) by HammeredGlass on Saturday September 26 2020, @12:47PM (2 children)

    by HammeredGlass (12241) on Saturday September 26 2020, @12:47PM (#1057223)

    of time travel to begin with. There is no past or future existence everpresent(sic)for us to travel to and from.

    • (Score: 3, Interesting) by JoeMerchant on Saturday September 26 2020, @01:36PM

      by JoeMerchant (3937) on Saturday September 26 2020, @01:36PM (#1057236)

      There is no past or future existence everpresent

      That we can currently perceive...

      We already record (incredibly low fidelity) descriptions of the past, such is the nature of time's arrow.

      We already model (wildly speculative, often wrong, low fidelity) predictions of the future, and our models are improving with experience and practice.

      In a philosophical sense, we should be able to achieve "time travel to the future with return to the present" simply by improving our modeling and rendering capabilities. If you are satisfied with simple, low fidelity information we already do this with pretty good accuracy and precision for easy to predict phenomena: mix up cake batter, pour in a pan, place in an oven at 350 degrees: your batter will be transformed to a fluffy cake 30 minutes in the future, here's a picture.

      To extend that: for simple systems, we can rewind time to points in the past with our crude recordings, and even model forward from those historical points with altered decisions to play out: what-if scenarios. What-if the CIA had succeeded in killing Castro, what would have happened next?

      Of course, nothing we have achieved (so far) comes anywhere close to the complexity and fidelity of the universe we all appear to have a shared perception of, but... if you extrapolate our progress in audio-visual recording and replay from 150 years ago to 150,000 years in the future, people in that distant future may well be able to "time travel" forward and back as they please - what they won't be able to do is enter this timeline in which we are building the time travel capability, they will only be able to affect alternate universes which you may attempt to dismiss as fictional, but they may be unable to perceive as any less real than what we call reality.

      --
      🌻🌻 [google.com]
    • (Score: 0) by Anonymous Coward on Saturday September 26 2020, @03:06PM

      by Anonymous Coward on Saturday September 26 2020, @03:06PM (#1057273)

      Except maybe for this:

      "Observe, how thou art asleep in a dwelling, and its doors are barred; on a sudden thou findest thyself in a far-off city, which thou enterest without moving thy feet or wearying thy body; without using thine eyes, thou seest; without taxing thine ears, thou hearest; without a tongue, thou speakest. And perchance when ten years are gone, thou wilt witness in the outer world the very things thou hast dreamed tonight. "

  • (Score: 1) by MIRV888 on Saturday September 26 2020, @02:13PM (5 children)

    by MIRV888 (11376) on Saturday September 26 2020, @02:13PM (#1057245)

    So even if you traveled back in time and killed Hitler, another Hitler persona would come along and start WWII anyway?
    You are gonna have to show your work on that one.
    ;-)

    Fascinating article. Even as a purely academic / mathematical exercise, it's interesting that on paper the timeline goes back to a stable unaffected state.

    • (Score: 2) by JoeMerchant on Saturday September 26 2020, @03:50PM (2 children)

      by JoeMerchant (3937) on Saturday September 26 2020, @03:50PM (#1057287)

      Obviously, if you travel back in time and kill Hitler, that universe will proceed forward differently, although it might be astonishingly similar to the one we know after 100 years or so.

      Similarly, if you travel back in time and kill a butterfly on a remote Pacific island which previously served as food for one of a million bats that lived in a cave on the island, that universe too will proceed forward differently and it might be astonishingly different from the one we know.

      Chaotic divergence is, by definition, very difficult to predict, and the notion that "time cops" can do anything but flail about wildly hoping to achieve or avoid specific outcomes is... fantastic.

      Now, if you are talking about the "you" in one of these alternate universe/timelines, that "you" will be a result of the effects, large or small, of the differences in your past - if you even exist in that timeline. The ability for "you" in alternate universe/timelines to have any communication with "you" in this or another alternate universe/timeline is what remains absolute fictional speculation - perhaps OP's "math" has put forward another such speculation, but I doubt it stands up to experimental validation any better than a Hollywood script.

      --
      🌻🌻 [google.com]
      • (Score: 0) by Anonymous Coward on Saturday September 26 2020, @08:36PM (1 child)

        by Anonymous Coward on Saturday September 26 2020, @08:36PM (#1057367)

        I remember the words that my father told me on my wedding day: "If you ever travel back in time, don't step on anything, because even the tiniest change can alter the future in ways you can't imagine."

        • (Score: 2) by maxwell demon on Saturday September 26 2020, @10:10PM

          by maxwell demon (1608) on Saturday September 26 2020, @10:10PM (#1057393) Journal

          And of course, already on your first time travel you didn't follow that advice, and now we've got that COVID-19 epidemic, and moreover time travel hasn't even been invented in this timeline so we can't go back to fix it.

          --
          The Tao of math: The numbers you can count are not the real numbers.
    • (Score: 2) by sjames on Saturday September 26 2020, @05:51PM

      by sjames (2882) on Saturday September 26 2020, @05:51PM (#1057326) Journal

      Possibilities include:

      You shoot and miss, you get arrested and fail.

      You kill the wrong person.

      You kill Hitler and history re-writes your motivation. Now, you went back in time to get a part from the obscure clockmaker who made the antique clock you are obsessed with restoring to absolutely original condition. You kill Hitler in a traffic accident on your way to the clockmaker's shop.

      The real world physics doesn't permit it even though pure mathematics doesn't forbid it. Your time machine is incinerated with you inside. You are next seen in a form resembling Hawking radiation but nobody realizes it.

      The always friendly and reassuring Dr. Moon shows up and says "and then you didn't" and you find yourself sitting on the couch eating pizza and watching Doctor Who. You are momentarily confused but soon forget about it.

    • (Score: 0) by Anonymous Coward on Saturday September 26 2020, @10:29PM

      by Anonymous Coward on Saturday September 26 2020, @10:29PM (#1057394)

      You can't travel back in time and kill Hitler.

      That's the first thing everyone always tries. But Hitler didn't die. Why not?

      Because every time someone kills Hitler, what happens then is even worse than what Hitler did. So time travellers have dedicated teams in Hitler's era to stop people from killing him, usually by killing whoever is trying to kill Hitler. Sometimes they can go back in time themselves and make sure the ones trying to kill Hitler are never born, but that usually fucks things up there too, so just killing the killers is the safest way.

      I know it's nigh impossible to imagine something even worse than Hitler, but it's true nonetheless.

  • (Score: 2) by Mojibake Tengu on Saturday September 26 2020, @02:51PM (1 child)

    by Mojibake Tengu (8598) on Saturday September 26 2020, @02:51PM (#1057266) Journal

    The quadripartite operator from the paper is XOR.

    Consider this: in a digital world, you can transform any kind of digital object to any other digital object of the same size, with just xor operation. All you need to know is a result of xor of both objects as a magical value, and perform it logically atomic.

    In a digital paradigm, size of data represents virtual energy. I was dabbling into magic in a real world since I realized this simple fact, about 40 years ago.

    --
    Respect Authorities. Know your social status. Woke responsibly.
    • (Score: 0) by Anonymous Coward on Saturday September 26 2020, @04:38PM

      by Anonymous Coward on Saturday September 26 2020, @04:38PM (#1057307)

      You just blew my mind. Wait, no... sorry wrong post.

  • (Score: 1, Disagree) by oumuamua on Saturday September 26 2020, @04:51PM (6 children)

    by oumuamua (8401) on Saturday September 26 2020, @04:51PM (#1057309)

    how impossible is it?
    That even newer science fiction shows discount it. Those that do have time travel do it via the 'multiple-universe' loop hole. You don't go back in time, you go to another universe, the exact same as yours except for a time shift to the future or past.

    • (Score: 2) by JoeMerchant on Saturday September 26 2020, @06:24PM (3 children)

      by JoeMerchant (3937) on Saturday September 26 2020, @06:24PM (#1057333)

      That even newer science fiction shows discount it.

      Really? I can't seem to get away from time travel science fiction - if you strike off that, superpower humans, and talking aliens, there's hardly any new science fiction left.

      --
      🌻🌻 [google.com]
      • (Score: 2) by Grishnakh on Saturday September 26 2020, @07:50PM (2 children)

        by Grishnakh (2831) on Saturday September 26 2020, @07:50PM (#1057351)

        if you strike off that, superpower humans, and talking aliens, there's hardly any new science fiction left.

        There's been plenty of new sci-fi for the last 10-20 years. What do you think all those "zombie apocalypse" movies and shows are?

        You're probably lamenting the lack of what I call "spaceship sci-fi", which was commonplace back in the 80s. There hasn't been much of that; the biggest exception I can think of is the show "The Expanse" (which is fantastic BTW, I highly recommend it). There's a reason for this lack of spaceship sci-fi: back in the 80s, our society (at least in the US and the West in general) was very optimistic about the future. Sci-fi is, at its root, a statement about society's outlook on its own future. Back in the 80s, we had stuff like ST:TNG and various other movies showing humanity as a star-faring civilization in the future. That's mostly gone now, and for good reason: we've now realized that that's all a big pipe dream, and that our future is very bleak. Therefore, what we have now is mostly very pessimistic sci-fi, which is why have have shows like The Walking Dead, showing us what our future society is going to resemble.

        • (Score: 2) by JoeMerchant on Saturday September 26 2020, @11:17PM (1 child)

          by JoeMerchant (3937) on Saturday September 26 2020, @11:17PM (#1057416)

          Oh FFS, how are zombies not also superpowers out there with werewolves and vampires, and when did Medieval gore-horror-fantasy get a pass as "Science" fiction?

          Away was decent recent "spaceship" science fiction almost in the 2001 genre, along with The Martian, there have been a couple of others but mostly extreme low budget. I'm trying to remember the Mexican one with the "Island Utopia" (not) offshore... but, for each of those there are ten "Altered Carbon" style storylines polluted with superpowered humans and various immortal this and invincible that, generally following around actors / actresses in their late 20s-early 30s playing as if they are still in high school.

          --
          🌻🌻 [google.com]
          • (Score: 2) by Grishnakh on Monday September 28 2020, @01:30AM

            by Grishnakh (2831) on Monday September 28 2020, @01:30AM (#1057964)

            Oh FFS, how are zombies not also superpowers out there with werewolves and vampires

            This was addressed in "28 Days Later" back in 2001: they're created by a virus. Of course, they're not exactly brain-eating undead zombies, but they do turn violent and mindless. We already have something like this in nature now, called "rabies".

            Anyway, if you still think "The Walking Dead" or other zombie stuff just doesn't stick close enough to the laws of physics and biology, I can point you to tons of spaceship sci-fi that plays fast-and-loose with science too. FTL travel itself has long been controversial, but just look at all the sci-fi spaceships that have artificial gravity (not made by constant thrust or rotation); I'm not a physicist, but that actually seems even more in violation of the laws of physics as we know them than FTL travel. The simple truth is, most sci-fi makes serious errors with physics, usually as a plot device. Just look at the movie "The Martian" (and the book it's based on) which you mentioned: reportedly, the whole thing is actually pretty accurate with regard to physics, except the very opening scene, where a big dust storm causes Matt Damon to be stranded on Mars. Storms that violent are impossible on a planet with atmospheric pressure 1/200th of Earth's. But the author invented it anyway to create the story; I guess in reality Mars is so inert that there's no plausible scenario we can contrive where an astronaut would be left behind alive, with the crew somehow thinking he was dead. So it's a little hypocritical for you to call out The Martian as somehow more plausible than zombies.

            generally following around actors / actresses in their late 20s-early 30s playing as if they are still in high school.

            This is normal with Hollywood, and it's something you have to look past when you watch live-action movies/shows. For comparison, look at when they recast a character on a movie or TV show (such as when Kirstie Alley as Saavik in Star Trek II was replaced by Robin Curtis for ST:III, or Katie Holmes was replaced by Maggie Gyllenhaal after Batman Begins): some people complain, but generally most people just go with it, because you have to understand that making a live-action movie actually involves real people, and things don't always work perfectly: actors can't get free from other obligations to show up for a sequel on time, or the director just doesn't want to work with them because they were so awful in the last fillm. With stories about high schoolers, the reality is that people who are actually good at acting are almost always significantly older than that (they've at least gone to college for acting), and even if you could find enough teenage acting prodigies to star in your show, they already have busy lives and coordinating things to get them together in one place for shooting, and doing this reliably over the course of a TV series, is unrealistic. It's much easier to just get young-looking adults with proper acting training to do the job.

    • (Score: 0) by Anonymous Coward on Sunday September 27 2020, @09:36AM (1 child)

      by Anonymous Coward on Sunday September 27 2020, @09:36AM (#1057588)

      Time travel is impossible because it breaks causality. The hand-waving at mathematical loops is not a good solution, IMHO. We are already all traveling in time, but in one direction that cannot be altered. You want to alter it, go watch Human Centipede

      • (Score: 2) by hendrikboom on Monday September 28 2020, @02:10AM

        by hendrikboom (1125) Subscriber Badge on Monday September 28 2020, @02:10AM (#1057992) Homepage Journal

        Causality? Are we so sure there *is* causality? Seems to me the evidence for causality is at least as weak as the evidence against time travel.

  • (Score: 2) by Runaway1956 on Sunday September 27 2020, @12:06AM

    by Runaway1956 (2926) Subscriber Badge on Sunday September 27 2020, @12:06AM (#1057440) Journal

    Stability itself is nothing else than a more sluggish motion.

(1)