Time Frame: an article by GF Willmetts.
Something that has always been gotten wrong in most science fiction is the belief that even faster-than-light brings different worlds into the same time frame. That is events happening in the new world at the same time as in the world you came from, within maybe a few months, not decades or centuries different. I’ll qualify the opening sentence ‘most’ as there has to be some SF author who has taken that into account. I mean, Joe Haldeman’s ‘The Forever War’ has its military returning to Earth on furlough years into the future each time they come home. I can’t think of any other examples, although I suspect the reason other writers haven’t done this is because they think he has copyright on the idea when, in fact, it’s accurate scientific knowledge, as I will explain. Rather contradictory, most SF writers and SF TV series and films have chosen the impossible route simply because they can ignore people ageing at home base and where their spacecraft go. How else can an off-world problem have a contemporary, albeit set in the future, solution for all to see?
The main problem comes with the speed of light. As a spacecraft approaches it, the lives of the crew will happen slower than outside because of time dilation. If they had a twin on board and returned, the twin at home, assuming he was still alive, would be much older. However, I gave some thought to doing it, and if you include the time it would take to accelerate and decelerate, the differences in ages might actually be a lot closer than the original theory suggests. Reality likes to be tidy. The twin brother at home could still have died, though, depending on how far the round trip went.
The problem, as popularised by the original ‘Star Trek,’ is going from star system to star system, and no matter the length of their five-year mission, their activities stayed within the same timeline, or the likes of the ‘Menagerie’ two-parter wouldn’t have appeared in order. Starfleet’s and other alien species warp drives not only distorted distance but also must have had some effect on time, or they had to calculate when using them. When you take that into account, time travel into the distant past becomes easy for the likes of the Enterprise, who use the slingshot to increase their velocity. The real problem is the structural damage to the spacecraft as well as returning to their present without messing up the past. Unless their involvement needed to be fulfilled earlier.
Despite being fictional, it highlights the challenges of adhering to the same time frame and achieving this objective. Faster-than-light depends on Einstein’s equation: E=MC² Energy = Mass x speed of light² Time doesn’t really enter into it. If it did, then there would be a whole different level of physics. It shows the kind of energy needed to arrive there, not the time it takes. Even if you applied integral calculus, all you would know is what happened in an instance. The information isn’t particularly beneficial.
I ended up doing some deep thinking about this topic. Once FTL can be achieved, then you would have to consider how fast you can go. Alpha Centauri is 4.37 light-years away. Assuming you could get acceleration up to cruising FTL speed while in the solar system and had the means to decelerate on arrival, that would be little time, just over a year, for the crew but at least 4 years for people at home. All well and good, but as pointed out, the deceleration would take a lot of time, and you would have to do that halfway through the trip, so the crew would be slowly ageing from there on. If you multiplied up how much faster than light you could travel, you would be decelerating as you leave the solar system for an even longer distance. Then you have to take into account how long the spacecraft would stay there before completing the round trip. It’s easy to account for over 20 years for Earth and a lot less for the astronaut crew. Perhaps not too practical for local space star systems but useful for those much further away, assuming you take into account the expanding universe. Of course, we must assume that there would be nothing to impede the spacecraft, and you can hardly predict that because the light we receive is so in the past. Space is mostly empty, but you can’t predict rogue planets, singularities, space debris, etc. getting in the way.
There is still the assumption that the near speed of light is possible, let alone exceeding it. If the latter is feasible, we must estimate the number of times we can surpass the speed of light, provided we have the necessary energy. Time in the spacecraft would still go at its own speed, albeit much slower than the outside reality. A round trip would still have a younger crew arriving back on Earth because of time dilation. Anyone older than 40 on Earth might not even be alive when they return.
In many respects, acceleration can be measured, and fuel can be conserved by relying on planetary slingshots. Declaration is a lot harder. Obeying Newton’s laws of motion, once a speed is reached, the spacecraft will continue at said speed until stopped. Therein lies the problem. Just how do you decelerate from near light speed to speeds far faster? The faster you go, the longer it will take to slow down, let alone stop.
It’s here I spent the most time. You can go near the speed of light or even ten times as fast; the same problem exists. The only things big enough to attempt a reverse slingshot are large stars or singularities, and you would have to go around them a lot to slow down. At those speeds, the spaceship is more likely to go through them than orbit around them. Of course, we don’t know how a black hole would react or how a robust spacecraft would survive. It makes the reverse slingshot used in the 1984 film ‘2010: The Year We Made Contact’ look tiny in comparison. Again, no one has used it in any other SF film or book as far as I can see because they think it belongs solely there and is not a general scientific solution.
I’ve said in the past once the highest speed has been reached, keep it until halfway there and then fire the engines in reverse. This doesn’t necessarily mean flipping the spacecraft over, just a difference in design with the living section on top capable of turning its floor in the opposite direction. Saying that, one still has to wonder if organics can survive that kind of g-force unless it’s a slow acceleration, although having the entire spacecraft rotating would probably be better to have some sort of conventional gravity for the crew. Already, I’ve worked out some sort of credible design, but it doesn’t mean its crew will be any better for it. Without that manysupplies, especially for over a decade each way, hibernation might be a necessity, assuming those in hibernation aren’t crushed. There are still issues related to construction, size, and a new understanding of physics that need to be addressed in order to achieve such speed.
Rather oddly, you’re looking for information online, and you need to select the right words for the information, especially as my first attempt said that time was the same inside the rocket and on Earth when it’s an established fact that the nearer you approach light speed, time onboard the spacecraft slows down because of time dilation. As such, the two groups would differ in time, and if they went faster than light for a period, the crew would probably cease to age, so the time frame would change. There would have to be a new level of physics if time could be used in the equations to get back in the same time frame, but that would be time travel, and, as far as we know so far, you can’t go backwards in time yet.
Entropy is the level of any system falling apart and not being able to be put back together. I put some thought into this, and short of breaking out of our reality, there aren’t any other options to go backwards in time. We still have no proof of the existence of hyperspace, and even if there was, there would be no proof you could pop out of it in an earlier time. If there was no time movement, we wouldn’t be able to move. Neither would any material object, including a spacecraft. You would be effectively entering a starship graveyard if time froze there. It’s also unlikely that entropy could work in reverse, or you would quickly revert to ova and sperm and death, or rather pre-birth. Quite what would happen to the spacecraft is anybody’s guess. Conceivably, you might go back in time, but the limitation would be your own lifetime. Quite how that would work with a multiple-aged crew is anybody’s guess, and there are probably works of science fiction exploring it. Popping in and out of hyperspace, no matter how briefly, is no guarantee that you could jump out in an earlier time period, so arriving in the same time frame doesn’t seem likely. The same problem would also apply to communication. I doubt if Ursula Le Guin’s communication device, ansible, would be any faster, and even if it was, you would still have to have a receiver in the right position to gather the message.
Throughout all these options, it still comes down to having an appropriate energy source, and there we have no options currently available. Without that, it’s unlikely any long-distance spacecraft could get back in the future, let alone in the same time frame that they left in.
One would hope it would be some sort of elusive fission drive if you wanted unlimited amounts of energy, but that’s still beyond us at this time. Is it possible an extraterrestrial species could have a better power source? Possibly, if they are much older than ourselves, giving them time to experiment. The thing is, if they only had the same tools and physics rules as ourselves, then it’s unlikely. They might have to rely on generation spaceships and take their families with them. At least they would all age at the same rate.
As a lesson to science fiction writers, if you do have a solution to the time frame problem, don’t take it for granted that it’s solvable. Hard SF writers would work within the problem; you would need to have some sort of credible solution to look practical..
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