"What would be good, though, would be for someone to call us back when the thinking leads to something, anything, that we can see or feel or sense or even understand—because all this astonishingly brilliant thought and science and learning and history, all these amazing stories, as far as I can tell, have no consequences at all. Our commonsense subjective understanding of time is as telling, as tyrannical, as it ever was. A century-plus of fervent speculation and analysis of time and time travel have led to exactly no outcomes. We are as stuck in the present, as irrevocably exiled from both past and future, as ever."
Einstein's time dilation has practical consequences: aside from being able to observe the slowdown in atomic clocks taken up in airplanes and the many consequences in astronomy, we also have GPS, which would not work without taking relativity into account. If GPS doesn't count as a 'consequence' or 'outcome' due to a non-traditional understanding of time, nothing does!
This is a relatively common misconception. The location calculation in GPS is independent of any time dilation between the GPS receiver and the satellites (as long as the satellites have roughly equal dilation), because the receiver clock is derived from the satellites' signals. This is also the reason why you need at least four satellites for a 3D fix, and three for a 2D fix - you are always deriving an additional unknown variable, time. (And this is also the reason why a GPS time receiver works with only one satellite: the position is locked when they are set up, after that they can work with 1+ satellites. More satellites will reduce errors, though.)
The time dilation is therefore only compensated so that you can use a GPS receiver as a very accurate, absolute clock.
Technically the fourth variable that a receiver solves for is the clock error in the receiver, not the actual time (though that then follows easily enough). The system of equations is only solvable because it is assumed that the clock error of the satellietes relative to each other is zero. I'm not convinced though that time dilation is the same for all the satellites, since they are not all in the same orbit.
Since the system works by determining signal delay between the satellite and the receiver and the signals move at (rougly) the speed of light, even an nanosecond error in time is already a 30 cm error in position. According to [0] the clock drift due to relativistic effects would be over 45000 nanoseconds per day. So keeping the clocks synchronized for all the satellites is crucial and relativistic corrections are super important for accurate positioning.
> According to [0] the clock drift due to relativistic effects would be over 45000 nanoseconds per day.
Between an uncorrected satellite and the receiver. This error is already removed through the fourth variable, only the average error of the satellites used for this remains (assuming perfect receiver etc.). So even if the satellites where not corrected the positioning error would not be "XY kilometers per day and climbing", the much smaller difference in time dilation between satellites would remain though.
The location calculation is completely dependent upon relativistic time dilation.
The Navistar satellites have an orbital speed of 8,750 MPH (more than 2 miles per second, relative to our earth surface frame), they are subject to a relativistic time dilation adjustment of -7201ns (slower than our earth surface frame). The location calculation cannot ignore that. The GPS signal (radio) takes on average 1 foot per nanosecond (perhaps a slightly bit more, but this is electromag radiation in a non-vacuum). If your receiver didn't account for this you would be more than a mile from your actual location. Relativity and its time dilation are required for any satellite based location system -- unless your satellites are at altitude of zero.
A pretty substantial flaw in the piece, almost enough to sink it, is the suggestion that Looper is somehow more worthy of calling out than Primer. Tsk... somebody sack the fact checkers...
It's a REALLY confusing film, but absolutely brilliant in the way that it shows just how confusing a world with time travel would be[1]. The way everything escalates in the latter half of the film is insane. For a "simple" explanation of the plot, see [2]. Since this analysis was done by a third party, it's obviously hard to be sure that this is fully correct, but it at least seems very close.
[1] For anyone able to observe the multiple time lines, obviously. :)
Imagine instead of living in an [array of time-frames], moving in one direction, i.e. time, in a single frame only, like a snapshot (even with the possibility to observe the whole [array of time-frames] at once). Would you have any words to describe it? I think all our mental models would just collapse.
Some people say time is just an illusion we use to process reallity as an [array of time-frames]. I think what you are looking for is a kind of enlightening which in this case would mean stepping out of the illusion of time. Some people reported to achieve this with meditation and/or psychodelics.
The closest existence I can think of is being trapped in a singularity. An observer would obviously see your body obliterated in mere seconds, but time would exponentially slow down on your end.
The basics for time travel start at CERN in about a year and end in 2034 with the first "time machine" built by GE. Too bad we can't post pictures or I'd show it to you.
I realize that time travel is not invented in my lifetime, if it had been I would have traveled back to tell myself to get out of tech stocks in 1999 :-)
The reason we can't go back in time is that time and information (and hence consciousness, which is made of information) are inextricably linked by quantum physics:
Your post explains why going back in time along the same path is pointless because you lose the information. But maybe we could take a different path (closed timelike curve) and keep the information.
"'There is no difference between Time and any of the three dimensions of Space except that our consciousness moves along it,' says the Traveller. That turned out, amazingly and counterintuitively, to be true. 'In surprisingly short order this notion would become part of the orthodoxy of theoretical physics,' says Gleick."
What? Spacetime does contain four dimensions, but the whole reason that time travel is fiction, rather than fact, is because the time dimension is different from the space dimensions.
You’re right that “There is no difference between Time and any of the three dimensions of Space [...]” is kind of misleading, but it’s only half wrong.
The special relativity story is more nuanced. There’s no single “time direction”. Which direction in spacetime looks like “time” vs. a mix of “space” and “time” movements vs. “space” depends on your reference frame.
Every “faster-than-light velocity vector” can be considered the direction of “time” for some observer, just as every “slower-than-light velocity vector” can be considered a direction in “space” for some observer. A vector like “the vector difference between the position of the earth now and the moon half a second in the future” (by our measurement) is, for some other reference frame, a pure movement in time. In just the same way, “the vector difference between the position of the earth now and the moon two seconds in the future” is a pure distance in space indicating simultaneous-in-time events, for some other reference frame.
Or perhaps we should even say that the “reference frames” and a split between space and time dimensions are an abstract concept that we impose on top of the 4-dimensional spacetime. We can work out all of our physics in a 4-dimensional context without explicitly splitting “space” from “time”. https://en.wikipedia.org/wiki/Spacetime_algebra#Spacetime_sp...
In just the same way, if you have a two-dimensional Euclidean plane with no externally imposed markers on it, there’s no inherent notion of “up” or “left” – those depend entirely on what kind of reference you pick. Imposing some specific coordinates is sometimes useful for understanding the geometry and solving particular problems, but itÍ’s in some ways arbitrary.
Reminds me of the final book in the Hitchhiker's Guide "trilogy". The advanced version of the Guide is calibrating itself so it can perform "reverse temporal engineering" on behalf of Ford.
It asks a series of questions, one of which makes no sense, and then says something like, "Oh, time travels in that direction for you."
I wonder. If the universe is deterministic, and nothing is random, then Time could be thought of as a vector whose values encompass all the properties of everything in existence and the direction of changes in each of them. If we knew all the "rules" that govern those changes and could make a simulation that captured the current state of everything, we could traverse back and forth along that vector (but probably not beyond the instant when that simulation was turned on, because then it would have to simulate itself...)
This was a prevalent idea in physics till quantum mechanics burst into the scene. I don't remember where I saw it, this the most convincing argument I heard regarding simulating future: Our universe is actually the most efficient computer that can simulate the future with our physical laws. Meaning, at any given time, it is not actually executing a pre-determined program, it is busy computing the future.
You don't really need quantum mechanics for this argument, though. Even in a non-quantum world, non-linear and, in particular, chaotic systems effectively prevent you from predicting the future. While you could do it in theory, in practice you would need do know every single variable very precisely because the outcome of chaotic systems can change drastically due to a small change in initial conditions (which is colloquially known as the butterfly effect). Quantum mechanics just makes this even harder or downright impossible (think of determining the exact values of the wave function or predicting the outcome of measurements). But even if we did know all the variables, we'd then still need to simulate every single atom to predict the future, so we'd basically be building another universe. So, you're right, in that sense the universe is the most efficient computer simulating our physical reality.
We can calculate things like if the moon is ever going to leave Earth's orbit and we can tell it was much closer to Earth in prehistoric times.
We can predict the future and recall the past, just not in a scale that is practical for our mundane lives. Personally, I think this is a humility lesson: in the grand scheme of things, the entire span of a human life is less than a tiny drop in the ocean of time.
Events are a stone being dropped into or skipped along the surface of that pond. The waves produced by the event are viewable from all angles. The actual event -the stone drop- occurs only once. The event is immutable, even though the ripples persist and are measurable.
We may eventually be able to view the ripples in more detail, and see past or future events. The events themselves though, are immutable. They've already occurred or have not occurred yet. The stone does not change. The interaction between stone and surface does not change. What changes is our ability to decipher data from that event, not the event itself.
Sure. Time is a mere environmentaly conditioned mental conception. No such phenomena exist. Only environmental and social conditioning. It could only be derived by an intelligent observer. No observer - no time. For a photon there is no time.
BTW, conversation laws are hinting to an illusory nature of time. Change of compound structures do exist and it is in everything we are able to observe. But the whole is unchanged, no matter what fancy theories or simulations would say.
Einstein's time dilation has practical consequences: aside from being able to observe the slowdown in atomic clocks taken up in airplanes and the many consequences in astronomy, we also have GPS, which would not work without taking relativity into account. If GPS doesn't count as a 'consequence' or 'outcome' due to a non-traditional understanding of time, nothing does!