Unless I misunderstood their explanation, I believe there are several inaccuracies in this video. Traveling toward or away from Earth would not change whether you saw into the past or future. If...
Unless I misunderstood their explanation, I believe there are several inaccuracies in this video.
Traveling toward or away from Earth would not change whether you saw into the past or future. If you travelled near the speed of light away from Earth, everyone on Earth is aging faster than you. Let's say they age 10 years and you age only 5. Then you turn around and travel back toward Earth nearing the speed of light - same thing. They age 10 more years while you age 5.
There is no way that we know of to travel back in time. You can only travel forward in time, either by approaching the speed of light or by increasing your proximity to something very massive.
The subtleties of how that works are fascinating, so I'm just gonna ramble for a minute: This is only true from Earth's frame of reference. From your frame of reference, you're stationary and the...
The subtleties of how that works are fascinating, so I'm just gonna ramble for a minute:
If you travelled near the speed of light away from Earth, everyone on Earth is aging faster than you
This is only true from Earth's frame of reference. From your frame of reference, you're stationary and the Earth is moving away from you, and it's everyone on Earth that ages slower, in other words: both of you perceive the other as ageing more slowly, because velocity is relative and so is time. At this point, there's no way to determine who is "right", because both frames are equally valid. Relativity!
And yet... when you get home, everyone on Earth has in fact aged more than you. So what happened? It's actually this part:
Then you turn around
The turning around is acceleration, and the acceleration is what dilates your own time more than that of everyone on Earth (similar to how gravity dilates time I guess). As you fire your boosters to turn around, only then do you perceive Earth's time to be speeding up, and by the time you arrive home you have experienced less time than what has passed by on Earth. Note as well, it's impossible to "compare" experience of time without one or both parties accelerating to come back together, since any form of communication will show the same effects as the light you're using to "see" the Earth age slower.
The implications are interesting: I see Earth as ageing slower but Earth sees me as ageing slower. That means the idea of simultaneity is relative: whether or not two events happened at the same time is a question with different answers depending on how fast you were going and in what direction. My old physics textbook illustrates this with an example of a treaty needing to be signed simultaneously by two diplomats on a train going near lightspeed.
I would suggest reading the sources, as I think the video graphics are rather confusing unless you already know what they're meant to depict. But in short, the first half of the video is arguing...
I would suggest reading the sources, as I think the video graphics are rather confusing unless you already know what they're meant to depict. But in short, the first half of the video is arguing for eternalism (which is fairly strongly motivated by special relativity), while the second half of the video argues for the growing block universe hypothesis (which is better aligned with our intuition but introduces its own problems).
No matter what your traveling forward in time relative to yourself (proper time). However if you somehow traveled faster than C, you would relative to other observers, appear in their past. Say I...
No matter what your traveling forward in time relative to yourself (proper time). However if you somehow traveled faster than C, you would relative to other observers, appear in their past. Say I stand next to you and leave you behind to travel next to the sun, who's light takes approximately 8 minutes to get to the earth, if I get there traveling faster than C, you might see me next to the sun within seconds of my departure, which would put me at about 8 minutes into your past.
This might not have to occur naturally either, you could start with a wormhole across two points in the same timeline and then 'just' shift one of the entrances relative to the other at some...
I've seen a few theories where time travel backward is possible if one end of a wormhole (also still a theory) is in the past and one end is in some future time.
This might not have to occur naturally either, you could start with a wormhole across two points in the same timeline and then 'just' shift one of the entrances relative to the other at some fraction of c. Not that my opinion on this subject matters in the slightest, but I kind of think that the paradoxes implicit in backwards time travel suggest it isn't possible. IANAP, but if wormholes exist maybe they're fixed relative to each other or something.
This is ... kind of incoherent. Obviously, different times cannot exist at the same time—that's a contradiction in terms. Different things are meant by 'same time' and 'different times', and if...
This is ... kind of incoherent. Obviously, different times cannot exist at the same time—that's a contradiction in terms. Different things are meant by 'same time' and 'different times', and if you actually define your terms properly instead of equivocating and appealing to intuition, then there isn't really any problem. Bonus points for conflating general and special relativity with classical relativity—the latter is much easier to understand and is also much, much older.
They also introduce the concept of 'magical internet' and then walk it back which, aside from being a weird pedagogical choice, doesn't really make any sense? I'm still trying to figure out what they meant by that. Our models aren't inconsistent with universally synchronised clocks; it's just that they aren't required and aren't really useful in understanding anything.
They are referring to an ansible, i.e. a hypothetical device allowing instantaneous communication along a line of simultaneity. If such a device were possible, then it would in fact be possible to...
They also introduce the concept of 'magical internet' and then walk it back which, aside from being a weird pedagogical choice, doesn't really make any sense?
They are referring to an ansible, i.e. a hypothetical device allowing instantaneous communication along a line of simultaneity. If such a device were possible, then it would in fact be possible to send messages into the past by exploiting the fact that different observers will generally have different lines of simultaneity.
The ansible forces someone to take seriously how strange the relativity of simultaneity is. For instance, it is technically possible that there is an alien on a space ship somewhere in the universe whom I am (in my reference frame) simultaneously vibing with, but in their reference frame the dinosaurs are still roaming the earth. This makes it impossibly tricky to define a "universal now" in an unambiguous matter.
I took this not as a real way to describe an experience that’s physically possible, but to give a theoretical god perspective. Maybe something we could measure in a perfect simulation of the universe.
I took this not as a real way to describe an experience that’s physically possible, but to give a theoretical god perspective. Maybe something we could measure in a perfect simulation of the universe.
This is not very clear, but it seems like what you are basically describing is dinosaurs being reflected off of the aliens' eyeballs and reaching your present-day self. Yes? That doesn't prevent...
it is technically possible that there is an alien on a space ship somewhere in the universe whom I am (in my reference frame) simultaneously vibing with, but in their reference frame the dinosaurs are still roaming the earth. This makes it impossibly tricky to define a "universal now" in an unambiguous matter.
This is not very clear, but it seems like what you are basically describing is dinosaurs being reflected off of the aliens' eyeballs and reaching your present-day self. Yes? That doesn't prevent us from making a universally synchronised clock. The dinosaurs lived 2n years ago; the aliens are n light years away; you observe them (with light) as they were n years ago; you communicate with them (with magic) as they are right now. (This is, again, not useful, but it is completely coherent.)
No, I'm referring to the relativity of simultaneity, which is always different from what you see (since things "seen" by an observer necessarily happened in their past). I would recommend you read...
No, I'm referring to the relativity of simultaneity, which is always different from what you see (since things "seen" by an observer necessarily happened in their past). I would recommend you read the wikipedia article for an introduction, but the rough idea is that two events cannot be simultaneous in different reference frames unless those reference frames are moving with 0 relative velocity. That means, for instance, if we're both stationary with respect to each other and both start our stopwatches at the "same" time in my/your reference frame, a third observer moving with a relative velocity with respect to us would measure -- but not necessarily see! -- that one of us actually started our stopwatch before the other.
If that sounds weird, it's because it is weird. It's one of the weirdest features of special relativity.
If you can make sense of this spacetime diagram, then you will grok the concept. In context of the previous example, the horizontal green line would represent our line of simultaneity, events A and B would represent our respective presses of the stopwatch, and the blue/red lines would represent the trajectories (vertical-ish lines) and lines of simultaneity (horizontal-ish lines) for different observers. For the red observer, A occurs before B; for the blue observer, the order is opposite.
None of that means that it would be inconsistent to have a universally synchronised clock. It just means that different observers may observe the 'same' event at different times.
None of that means that it would be inconsistent to have a universally synchronised clock. It just means that different observers may observe the 'same' event at different times.
It's weaker than instantaneous communication, but a necessary prerequisite for it—I was conflating the two a bit. It is a real time clock that anybody can check whenever they want to. If checking...
It's weaker than instantaneous communication, but a necessary prerequisite for it—I was conflating the two a bit. It is a real time clock that anybody can check whenever they want to. If checking the time causally precedes one observation, which causally precedes another observation, which causally precedes another checking of the time, then the second observed time will be after the first. Due to time dilation, the rate of the clock is not identical for all observers, but the observed relative rates are relativistically consistent. Instantaneous communication is communication where the universal time at which a message is received is the same as when it is sent.
Maybe @gpl can given a more satisfactory answer, but here's the rub -- there is no universal causal ordering for two events that are spacelike-separated. But your intuition is right to some...
Maybe @gpl can given a more satisfactory answer, but here's the rub -- there is no universal causal ordering for two events that are spacelike-separated. But your intuition is right to some extent: you must have universal causal ordering for timelike-separated events.
If I've understood that correctly, then your point is that there is not a unique universally synchronised clock. Which is true. Rather, there are many possible ones; and picking any one and adding...
If I've understood that correctly, then your point is that there is not a unique universally synchronised clock. Which is true. Rather, there are many possible ones; and picking any one and adding it as an axiom would not be inconsistent.
If I have not misunderstood what you mean, then no, that is not the case. There is no clock that can be synchronised for all observers in spacetime, as spacelike separated observers can disagree...
If I have not misunderstood what you mean, then no, that is not the case. There is no clock that can be synchronised for all observers in spacetime, as spacelike separated observers can disagree about the causal order of events. But you don't even need to worry about such causal ordering, really. It is impossible to globally synchronize clocks placed around a rotating ring, for example. Here is a discussion of that.
I think you might be using a slightly non-standard definition of synchronised, though, based on
Due to time dilation, the rate of the clock is not identical for all observers, but the observed relative rates are relativistically consistent.
If two observer's clocks disagree, we typically say they are not synchronized, despite that each observer can compute and understand the lack of synchronization relativistically.
I never said that universally synchronised clocks exist! I only said that they would not be inconsistent. To reiterate, the point I'm actually trying to make is that instantaneous communication...
I never said that universally synchronised clocks exist! I only said that they would not be inconsistent.
To reiterate, the point I'm actually trying to make is that instantaneous communication would not need to violate causality or permit communication backwards in time.
Defining instantaneous communication requires us to define a notion of universal simultaneity. It is possible to define universal simultaneity in a way that does not violate causality, and hence it is possible to define instantaneous communication in a way that does not violate causality. That's all. (As a secondary point, it is possible to reason about relativistic processes in terms of a universal clock—and that is what the stackoverflow question psi linked does in saying that one event happens at time t1 and another at time t2—though I think this is not very useful.)
spacelike separated observers can disagree about the causal order of events
Which is why I defined the clock in terms of observations, not events. (I originally wrote 'events', but quickly edited to 'observations', so if you saw the original version, sorry. In computer science they are called events.)
If two observer's clocks disagree
But they don't. The values don't. If I on monday send a letter to you saying 'it is now monday', and you receive the letter on friday, it's not that my calendar disagrees with yours; it's that the letter took four days to reach its destination. On the other hand, if I meet up with you in person then, while our positions coincide, we will be in perfect agreement about what day it is.
That the rates can be different is literally what time dilation is.
I think I understand what you are saying, and what you are saying is true: you can consistently define a relativistic theory in which there is a global notion of simultaneity. To do so you have to...
I think I understand what you are saying, and what you are saying is true: you can consistently define a relativistic theory in which there is a global notion of simultaneity. To do so you have to introduce a preferred frame S in which the clocks are synchronized, and where two events are considered simultaneous if they are simultaneous in S. This procedure does not use Einstein synchronization, which I think is where I was losing you before — I had assumed we were using that procedure. If you emit a pulse from point A at t_1, it reflects at B at $t_2$, and returns to A at $t_3$, then you can synchronize clocks by defining
t_2 = t_1 + f*(t_3-t_1)
The Einstein convention is to say f=1/2 but you can define a consistent theory with other values. These theories will have transformations other than Lorentz Transformations relating two frames, and will have an anisotropic speed of light in moving frames, but they are consistent. It is however not the standard relativistic theory. So I would say to summarize, you are correct that one can define a consistent relativistic theory with global simultaneity, but you cannot consistently define global simultaneity within "standard" relativity.
Ooh, now that is a fascinating point (as is the linked pdf). I'm vacillating between Reichenbach's proposal being absolutely brilliant and absolute nonsense. It's a lot to think about!
Ooh, now that is a fascinating point (as is the linked pdf). I'm vacillating between Reichenbach's proposal being absolutely brilliant and absolute nonsense. It's a lot to think about!
Yeah Reichenbach was an interesting guy. I knew this discussion had reminded me of something, and once I found that stack exchange answer it reminded me of The Direction of Time which I had...
Yeah Reichenbach was an interesting guy. I knew this discussion had reminded me of something, and once I found that stack exchange answer it reminded me of The Direction of Time which I had started a few years back but never finished. I'm half inclined to dig it back out and finish after all this discussion.
Well, by the textbook definition of simultaneity this is strictly impossible (unless the speed of light is infinite, at least). I am curious exactly what you mean by simultaneous, then? Can you...
Defining instantaneous communication requires us to define a notion of universal simultaneity.
Well, by the textbook definition of simultaneity this is strictly impossible (unless the speed of light is infinite, at least). I am curious exactly what you mean by simultaneous, then? Can you give me a simple example?
Again, this is about fictive mechanisms. Mechanisms that don't exist. The question is: is it possible to define them theoretically in a way that's consistent with the rest of our physics and...
Again, this is about fictive mechanisms. Mechanisms that don't exist. The question is: is it possible to define them theoretically in a way that's consistent with the rest of our physics and doesn't make anything go wrong (like letting us communicate backwards in time)?
Upthread, you linked a stackoverflow question that said 'suppose one event happens at t1, and another at t2'. What does that mean to you (if it's coherent)? What would it mean for t1 to equal t2?
Sure. By the standard construction, two events are simultaneous when, after having positioned yourself exactly equidistant from the two events, photons radiating outwards from both events would...
Upthread, you linked a stackoverflow question that said 'suppose one event happens at t1, and another at t2'. What does that mean to you (if it's coherent)? What would it mean for t1 to equal t2?
Sure. By the standard construction, two events are simultaneous when, after having positioned yourself exactly equidistant from the two events, photons radiating outwards from both events would hit your eyeballs at exactly the same time.
But I would emphasize that this can only occur in one frame.
But that definition is transitive, isn't it?—say observer 1 is equidistant from A and B, and observes them at the same time; and observer 2 is equidistant from B and C, and observes them at the...
But that definition is transitive, isn't it?—say observer 1 is equidistant from A and B, and observes them at the same time; and observer 2 is equidistant from B and C, and observes them at the same time; then A and C are also simultaneous.
In any case, what do you find problematic about defining instantaneous communication in terms of this definition of simultaneity?
not if observers 1 and 2 are moving at different velocities. Edit - Thinking about it more, you're essentially talking about some variation of Einstein's train. It is not transitive. The reason...
I think not if observers 1 and 2 are moving at different velocities.
Edit - Thinking about it more, you're essentially talking about some variation of Einstein's train. It is not transitive.
The reason it's not transitive is that light must appear to travel the same rate to all observers. If simultaneity were transitive, the moving observer must deduce that light moving the same direction moves faster than light moving the opposite direction. That's a contradiction.
So instead the moving observer sees the event ahead of him occurring after the event behind him, even though the stationary observer sees them simultaneously.
Einstein's train uses two events and two observers - but you can see the same inconsistency with your setup involving three events and two observers. Observer 1 sees event A and B as simultaneous, but sees event C after. Observer 2 sees events B and C as simultaneous, but sees event A after.
Critically: Observer 1 sees event A before event C, but observer 2 sees event A after event C.
Forgive the poor ascii art spacetime diagram; I hope it clarifies things. The arrows indicate direction of motion.
<--1-- --2-->
A C
B
This is identical to Einstein's train if you take events B and C to be the same event. Observer 1 is the stationary observer and observer 2 is the moving one.
In general, that's fine. We can still say that A, B, and C happen simultaneously in universal time. (It would only be a problem if the observers were equidistant from all three events, which...
Observer 1 sees event A before event C, but observer 2 sees event A after event C
In general, that's fine. We can still say that A, B, and C happen simultaneously in universal time. (It would only be a problem if the observers were equidistant from all three events, which they're not in your diagram.)
With respect to the specific problem—I'll consider Einstein's train since it's more fully fleshed out. At the point when the observer on the train observes the first lightning flash, their position has changed, and they're no longer equidistant from where the two lightning flashes originally occurred, so we would not expect the conditions for simultaneity to be satisfied.
The pertinent question is the position of the observer relative to the events at the point when the events are observed. Not at the point when they happened.
Edit: one easy way to see that velocity must be irrelevant is the following. Re ascii art diagram this time. Suppose we have additional observers 1' which is stationary and equidistant from A and B and 2' which is stationary and equidistant from B and C. If the position of 1 coincides with 1' at the point when it observes A and B, then of course 1 must observe the same thing as 1'. If the positions don't coincide, then we haven't satisfied the criteria for proving simultaneity. Ditto 2 and 2'.
There is probably some setup with three events at the corners of an equilateral triangle, and observers moving between the midpoints of the edges of that triangle, that demonstrates some issue. I...
There is probably some setup with three events at the corners of an equilateral triangle, and observers moving between the midpoints of the edges of that triangle, that demonstrates some issue. I don't think I'm clever enough to figure that out.
There's probably some simpler example still that demonstrates the issue but, again, I'm not clever enough.
In general, that's fine. We can still say that A, B, and C happen simultaneously in universal time.
Yes, all observers observe the events in different order due to their distance from the event; but each can also use the distance to the event to determine how far in the past it occurred. When they all do this, they disagree on the order of events, not just order of observation.
Also, the lines of simultaneity for each observer change to the same angle regardless of their position. They each deduce the same order of events from any location, and they always disagree. It only depends on their velocity.
... see that velocity must be irrelevant ...
Yes, I think I understand what you're saying now. Pick a certain reference frame as "universal", and require any other frame to first consider a boost into that "universal" reference frame to say whether two events are simultaneous. I guess that's consistent, and all observers must agree on "universal" simultaneity.
I'm not sure how useful it is to discount velocity in general though. And, the choice of "universal" frame is arbitrary, so the relativity of simultaneity is still a problem in the choice of universal frame. You just mandate all the observers do some extra work to be consistent after the fact.
Edit: I think I got how to show the problem. (A problem? I've confused myself at this point).
The pertinent question is the position of the observer relative to the events at the point when the events are observed. Not at the point when they happened.
Consider a variation of Einstein's train, where both observers observe the lightning strikes at the same time, in the same place, at the proper midpoint between the two strike locations.
To the moving observer, the strike ahead of them must have occurred before the strike behind them; but to the stationary observer, the strikes must have occurred simultaneously.
By the standard construction, two events are simultaneous when, after having positioned yourself exactly equidistant from the two events, photons radiating outwards from both events would hit your eyeballs at exactly the same time.
The problem with @psi's definition is that distances also depend on the chosen frame. Picking the midpoint between two arbitrary events requires first measuring the distance between the two events, and that requires first picking a reference frame where the events are simultaneous. That definition seems circular.
Of course, I meant when measuring in your own frame. I only meant to illustrate a setup that's easily envisioned. If you know where an event occurred (x_A) (as measured in your frame, i.e. no...
By the standard construction, two events are simultaneous when, after having positioned yourself exactly equidistant from the two events, photons radiating outwards from both events would hit your eyeballs at exactly the same time.
The problem with @psi's definition is that distances also depend on the chosen frame. Picking the midpoint between two arbitrary events requires first measuring the distance between the two events, and that requires first picking a reference frame where the events are simultaneous. That definition seems circular.
Of course, I meant when measuring in your own frame. I only meant to illustrate a setup that's easily envisioned. If you know where an event occurred (x_A) (as measured in your frame, i.e. no length contraction), then you know when it occurred (x_A / c ago). Assuming you observe both events at the same time, then checking simultaneity is as simple as checking whether x_A / c = x_B / c, i.e. whether x_A and x_B were equidistant from you.
If the two events were not equidistant from you and also staggered by a time dt (with A preceding B), then you verify simultaneity by checking whether x_A / c + dt = x_B / c . But notice that these calculations don't require appealing to the Lorentz transformations -- it's just a regular Galilean transform.
I'm a little confused then - in my variation of Einstein's train, where both observers observe the events at the same time and location, the moving observer still deduces the events are not...
I'm a little confused then - in my variation of Einstein's train, where both observers observe the events at the same time and location, the moving observer still deduces the events are not simultaneous by the formulas you listed.
Then the moving observer must also deduce that the strike ahead of them was farther away from them than the lightning strike behind them; since the light arrived at the same time but the events were not simultaneous. You can see this in the lengths of the two dotted blue lines on my diagram.
But the moving observer also detects both strikes exactly halfway along their journey between the sites of the two strike locations. It seems like a contradiction - how can the moving observer deduce they are closer to the strike behind them but also deduce they are at the midpoint between the two strikes?
Edit: No, I got it. For the moving observer: they are at the midpoint when they observe the events. When the events occurred (in the past) they were where they came from. Obviously. Because it occurred in the past.
Edit edit: an approximation of the Lorenz transform into the moving observer's frame. The scale is certainly wrong but I think the angles are right.
These diagrams look good to me. And yes, precisely -- in the second diagram (moving frame), the observer clearly isn't equidistant from both events despite observing both events simultaneously, so...
These diagrams look good to me. And yes, precisely -- in the second diagram (moving frame), the observer clearly isn't equidistant from both events despite observing both events simultaneously, so it's no surprise that they would conclude that the events were not simultaneous in their frame.
In the same frame, transitivity will work. But suppose you have events A & B equidistant in frame S, with observer S observing them at the same time; and suppose also you have events B & C...
In the same frame, transitivity will work. But suppose you have events A & B equidistant in frame S, with observer S observing them at the same time; and suppose also you have events B & C equidistant in frame S', with observer S' observing them at the same time; then in general, if you were to stand equidistant from A and C, there is no frame in which you could observe A and C at the same time. You can find a fuller explanation here.
If you wanted to accept this definition anyway, transitivity be damned, then you would get the paradox I explained before: it is possible for an alien to coincide with my line of simultaneity, while the alien's line of simultaneity coincides with some time before I was born. Using such a definition, you could connect every point in spacetime, i.e. form the block universe discussed in the video.
If you accept @gpl's proposal (introduce a preferred frame of reference and define simultaneity with respect to that frame), then you must also accept that the speed of light is not a universal constant but instead has some preferred direction. Intuition about (1) simultaneity and (2) the universality of the speed of light are not compatible.
Why do we need the speed of light to be universal? My understanding was that our models are consistent with a bias in the speed of light, and—in the absence of instantaneous communication—this...
Why do we need the speed of light to be universal? My understanding was that our models are consistent with a bias in the speed of light, and—in the absence of instantaneous communication—this bias is not something we can detect. If we can accept a universal clock, surely we can accept a universal reference frame :)—at any rate, it seems much more acceptable than loss of causality.
I will take a look at that paper tomorrow—bedtime for me now.
Here is the most approachable discussion I've found (cc @gpl in case they're interested also): Philosophical Significance of the Special Theory of Relativity: The Conventionality of Simultaneity...
Here is the most approachable discussion I've found (cc @gpl in case they're interested also):
As far as I can tell, it's impossible to measure the one-way speed of light (and at any rate, it would have no impact on the underlying physics), so there is no issue with using a non-standard synchrony.
Based on my understanding of the literature, you're more sympathetic to the anti-realist/conventionalist perspective, while I'm more sympathetic to the realist/non-conventionalist perspective. It seems like there are proponents of both viewpoints! Unfortunately the video takes the realist perspective for granted; it really would have benefited from discussing this issue instead of the growing block universe hypothesis, which strikes me as overly speculative and undersupported.
I'm not quite sure I really understand what you're suggesting, but let me dig into this proposal some: My point isn't that there are merely many possible choices for "instantaneous" communication...
I'm not quite sure I really understand what you're suggesting, but let me dig into this proposal some:
Instantaneous communication is communication where the universal time at which a message is received is the same as when it is sent.
My point isn't that there are merely many possible choices for "instantaneous" communication -- there are infinitely many ones, with each one being observer dependent. That was my hypothetical with the alien: if I could communicate instantaneously with an alien on a (moving) spaceship, then that alien wouldn't be able to communicate instantaneously with me (as we lie on different lines of simultaneity). Rather, they'd only be able to send messages into my future or past, depending on whether they're moving towards or away from me. Or put different: my "now" is necessarily different from their "now".
And this begets the quandary in the video: how do we make sense of this incongruity? If the alien is far enough away/moving fast enough, their "now" might occur before I was even born!
Even if two events are observed at the same time, that doesn't mean they happened at the same universal time. I explained my point a bit more here; perhaps that clarifies?
Even if two events are observed at the same time, that doesn't mean they happened at the same universal time. I explained my point a bit more here; perhaps that clarifies?
I'd been waffling on unsubscribing for Kurzgesagt for a while, and this video pushed me to finally do it. Lately it feels like they're doing more of these abstract theoretical concepts that don't...
I'd been waffling on unsubscribing for Kurzgesagt for a while, and this video pushed me to finally do it. Lately it feels like they're doing more of these abstract theoretical concepts that don't make any sense when you try to actually follow what they're talking about.
Not a scientist. I believe we're living in a simulation. Lightspeed is a clock speed (CPU clock speed) limitation of the simulation, either a physics limit imposed by the simulation itself, or...
Not a scientist.
I believe we're living in a simulation. Lightspeed is a clock speed (CPU clock speed) limitation of the simulation, either a physics limit imposed by the simulation itself, or something coded into it deliberately to make the simulation manageable.
I love time travel stories. But I like the ones where they go into consequences and multiple branches, loops and fate. Watching this video, trying to keep track of "if X is traveling here, and Y is traveling there, but Z is doing this other thing..." it felt like the intended audience is mathematicians and physicists. Which is fine, but for the rest of us I couldn't help but think drugs needed to be involved to have a chance at following what they were trying to explain. Drugs or a degree, and drugs are cheaper.
I just do. Things like lightspeed, and quantum mechanics. How can something just abruptly change once you've observed it, but before you do it's something else entirely. What we know about time,...
I just do.
Things like lightspeed, and quantum mechanics. How can something just abruptly change once you've observed it, but before you do it's something else entirely. What we know about time, especially when the theories about black holes and such are brought into it just seem like the kind of thing that would come up if a computer was running everything. System's overloaded, too much on screen at one moment; chug, chug, chug and time slows down.
I'm not a physicist. Some who are have written about the concept (simulation reality). And proposed theories, experiments, and proofs. Not that it makes any actual difference to me, probably not to you either, or really even to the scientists; but if you put me up against the wall and scream talk, I'm going with simulation. We're all just bits and bytes in some sentient something's constructed reality.
It's fun to think about what they think about how the sim is going. Like, when the world wars broke out, were they concerned, or amused, or intrigued? Did they see it as us wasting our simulated time, or as us finding brutally efficient ways to settle our differences (rather than what's mostly happened in the 60s through to now, where we spend decades yelling across borders with only occasional, limited spats of violence that resolve nothing that cause the yelling or the violence)?
What do they think about us exploring the simulation? Is there an Antarian office pool running? "Six quadrabits on them not proving it until 2300, at least; they haven't even found out what happens when you spin up a wormhole yet!" And Bob, who's always an Antarian optimist, is shaking his head and putting his money on us figuring it out by 2170.
It's just a theory. But so is relativity, or so I'm told.
Because you or something touched it so you could observe what it's doing, relevantly, light in the case you may be thinking of. Your opinion sounds analogous to God of the Gaps, you prescribe...
How can something just abruptly change once you've observed it, but before you do it's something else entirely
Because you or something touched it so you could observe what it's doing, relevantly, light in the case you may be thinking of. Your opinion sounds analogous to God of the Gaps, you prescribe whatever hasn't been explained so far by science to an agent of said simulation. As for your system overload analogy and lightspeed, while something I've thought about before as I'm just as guilty of using computing analogies, I just don't see how it's different than other physical laws we have in that regard. A universe wouldn't be a universe without basic physical limits and we wouldn't be to discuss it. Personally I find it interesting but in my limited reading, I haven't found the theory convincing.
The problem here is that you are designed and conditioned to think in terms of how the "human-sized" world works, and the building blocks of reality are not human sized. The apparent contradiction...
How can something just abruptly change once you've observed it, but before you do it's something else entirely.
The problem here is that you are designed and conditioned to think in terms of how the "human-sized" world works, and the building blocks of reality are not human sized.
The apparent contradiction disappears if you accept that your intuitions about how reality works are, at the most fundamental level, simply wrong, and that the human-sized world is a phenomenon that emerges from a fundamentally different set of rules.
Other people have made analogies for the collapse of the wave function, but I just want to clarify the word "theory" here. A scientific theory and the general English word theory aren't the same...
Other people have made analogies for the collapse of the wave function, but I just want to clarify the word "theory" here. A scientific theory and the general English word theory aren't the same thing. Here's a scientific theory:
A scientific theory is an explanation of an aspect of the natural world and universe that can be (or a fortiori, that has been) repeatedly tested and corroborated in accordance with the scientific method, using accepted protocols of observation, measurement, and evaluation of results. Where possible, some theories are tested under controlled conditions in an experiment.[1][2] In circumstances not amenable to experimental testing, theories are evaluated through principles of abductive reasoning. Established scientific theories have withstood rigorous scrutiny and embody scientific knowledge.
Other theories you might be familiar with are germ theory and atomic theory.
So you're right that it's "just" a theory. It's just that in science, theory is the highest possible thing a model can be. Thinking the world is a simulation isn't a theory, or even really a hypothesis. It's a reckon. Which is fine, I have many reckons myself. But they're not scientific theories, and neither is this. And if it's a position that you won't change your mind on them... well, that's just good old faith at that point.
Unless I misunderstood their explanation, I believe there are several inaccuracies in this video.
Traveling toward or away from Earth would not change whether you saw into the past or future. If you travelled near the speed of light away from Earth, everyone on Earth is aging faster than you. Let's say they age 10 years and you age only 5. Then you turn around and travel back toward Earth nearing the speed of light - same thing. They age 10 more years while you age 5.
There is no way that we know of to travel back in time. You can only travel forward in time, either by approaching the speed of light or by increasing your proximity to something very massive.
The subtleties of how that works are fascinating, so I'm just gonna ramble for a minute:
This is only true from Earth's frame of reference. From your frame of reference, you're stationary and the Earth is moving away from you, and it's everyone on Earth that ages slower, in other words: both of you perceive the other as ageing more slowly, because velocity is relative and so is time. At this point, there's no way to determine who is "right", because both frames are equally valid. Relativity!
And yet... when you get home, everyone on Earth has in fact aged more than you. So what happened? It's actually this part:
The turning around is acceleration, and the acceleration is what dilates your own time more than that of everyone on Earth (similar to how gravity dilates time I guess). As you fire your boosters to turn around, only then do you perceive Earth's time to be speeding up, and by the time you arrive home you have experienced less time than what has passed by on Earth. Note as well, it's impossible to "compare" experience of time without one or both parties accelerating to come back together, since any form of communication will show the same effects as the light you're using to "see" the Earth age slower.
The implications are interesting: I see Earth as ageing slower but Earth sees me as ageing slower. That means the idea of simultaneity is relative: whether or not two events happened at the same time is a question with different answers depending on how fast you were going and in what direction. My old physics textbook illustrates this with an example of a treaty needing to be signed simultaneously by two diplomats on a train going near lightspeed.
I would suggest reading the sources, as I think the video graphics are rather confusing unless you already know what they're meant to depict. But in short, the first half of the video is arguing for eternalism (which is fairly strongly motivated by special relativity), while the second half of the video argues for the growing block universe hypothesis (which is better aligned with our intuition but introduces its own problems).
No matter what your traveling forward in time relative to yourself (proper time). However if you somehow traveled faster than C, you would relative to other observers, appear in their past. Say I stand next to you and leave you behind to travel next to the sun, who's light takes approximately 8 minutes to get to the earth, if I get there traveling faster than C, you might see me next to the sun within seconds of my departure, which would put me at about 8 minutes into your past.
This might not have to occur naturally either, you could start with a wormhole across two points in the same timeline and then 'just' shift one of the entrances relative to the other at some fraction of c. Not that my opinion on this subject matters in the slightest, but I kind of think that the paradoxes implicit in backwards time travel suggest it isn't possible. IANAP, but if wormholes exist maybe they're fixed relative to each other or something.
This is ... kind of incoherent. Obviously, different times cannot exist at the same time—that's a contradiction in terms. Different things are meant by 'same time' and 'different times', and if you actually define your terms properly instead of equivocating and appealing to intuition, then there isn't really any problem. Bonus points for conflating general and special relativity with classical relativity—the latter is much easier to understand and is also much, much older.
They also introduce the concept of 'magical internet' and then walk it back which, aside from being a weird pedagogical choice, doesn't really make any sense? I'm still trying to figure out what they meant by that. Our models aren't inconsistent with universally synchronised clocks; it's just that they aren't required and aren't really useful in understanding anything.
They are referring to an ansible, i.e. a hypothetical device allowing instantaneous communication along a line of simultaneity. If such a device were possible, then it would in fact be possible to send messages into the past by exploiting the fact that different observers will generally have different lines of simultaneity.
The ansible forces someone to take seriously how strange the relativity of simultaneity is. For instance, it is technically possible that there is an alien on a space ship somewhere in the universe whom I am (in my reference frame) simultaneously vibing with, but in their reference frame the dinosaurs are still roaming the earth. This makes it impossibly tricky to define a "universal now" in an unambiguous matter.
I took this not as a real way to describe an experience that’s physically possible, but to give a theoretical god perspective. Maybe something we could measure in a perfect simulation of the universe.
This is not very clear, but it seems like what you are basically describing is dinosaurs being reflected off of the aliens' eyeballs and reaching your present-day self. Yes? That doesn't prevent us from making a universally synchronised clock. The dinosaurs lived 2n years ago; the aliens are n light years away; you observe them (with light) as they were n years ago; you communicate with them (with magic) as they are right now. (This is, again, not useful, but it is completely coherent.)
No, I'm referring to the relativity of simultaneity, which is always different from what you see (since things "seen" by an observer necessarily happened in their past). I would recommend you read the wikipedia article for an introduction, but the rough idea is that two events cannot be simultaneous in different reference frames unless those reference frames are moving with 0 relative velocity. That means, for instance, if we're both stationary with respect to each other and both start our stopwatches at the "same" time in my/your reference frame, a third observer moving with a relative velocity with respect to us would measure -- but not necessarily see! -- that one of us actually started our stopwatch before the other.
If that sounds weird, it's because it is weird. It's one of the weirdest features of special relativity.
If you can make sense of this spacetime diagram, then you will grok the concept. In context of the previous example, the horizontal green line would represent our line of simultaneity, events A and B would represent our respective presses of the stopwatch, and the blue/red lines would represent the trajectories (vertical-ish lines) and lines of simultaneity (horizontal-ish lines) for different observers. For the red observer, A occurs before B; for the blue observer, the order is opposite.
None of that means that it would be inconsistent to have a universally synchronised clock. It just means that different observers may observe the 'same' event at different times.
Just so we’re all on the same page, what is the definition of universally synchronized clock that you’re working with here?
It's weaker than instantaneous communication, but a necessary prerequisite for it—I was conflating the two a bit. It is a real time clock that anybody can check whenever they want to. If checking the time causally precedes one observation, which causally precedes another observation, which causally precedes another checking of the time, then the second observed time will be after the first. Due to time dilation, the rate of the clock is not identical for all observers, but the observed relative rates are relativistically consistent. Instantaneous communication is communication where the universal time at which a message is received is the same as when it is sent.
Maybe @gpl can given a more satisfactory answer, but here's the rub -- there is no universal causal ordering for two events that are spacelike-separated. But your intuition is right to some extent: you must have universal causal ordering for timelike-separated events.
If I've understood that correctly, then your point is that there is not a unique universally synchronised clock. Which is true. Rather, there are many possible ones; and picking any one and adding it as an axiom would not be inconsistent.
If I have not misunderstood what you mean, then no, that is not the case. There is no clock that can be synchronised for all observers in spacetime, as spacelike separated observers can disagree about the causal order of events. But you don't even need to worry about such causal ordering, really. It is impossible to globally synchronize clocks placed around a rotating ring, for example. Here is a discussion of that.
I think you might be using a slightly non-standard definition of synchronised, though, based on
If two observer's clocks disagree, we typically say they are not synchronized, despite that each observer can compute and understand the lack of synchronization relativistically.
I never said that universally synchronised clocks exist! I only said that they would not be inconsistent.
To reiterate, the point I'm actually trying to make is that instantaneous communication would not need to violate causality or permit communication backwards in time.
Defining instantaneous communication requires us to define a notion of universal simultaneity. It is possible to define universal simultaneity in a way that does not violate causality, and hence it is possible to define instantaneous communication in a way that does not violate causality. That's all. (As a secondary point, it is possible to reason about relativistic processes in terms of a universal clock—and that is what the stackoverflow question psi linked does in saying that one event happens at time t1 and another at time t2—though I think this is not very useful.)
Which is why I defined the clock in terms of observations, not events. (I originally wrote 'events', but quickly edited to 'observations', so if you saw the original version, sorry. In computer science they are called events.)
But they don't. The values don't. If I on monday send a letter to you saying 'it is now monday', and you receive the letter on friday, it's not that my calendar disagrees with yours; it's that the letter took four days to reach its destination. On the other hand, if I meet up with you in person then, while our positions coincide, we will be in perfect agreement about what day it is.
That the rates can be different is literally what time dilation is.
I think I understand what you are saying, and what you are saying is true: you can consistently define a relativistic theory in which there is a global notion of simultaneity. To do so you have to introduce a preferred frame S in which the clocks are synchronized, and where two events are considered simultaneous if they are simultaneous in S. This procedure does not use Einstein synchronization, which I think is where I was losing you before — I had assumed we were using that procedure. If you emit a pulse from point A at t_1, it reflects at B at $t_2$, and returns to A at $t_3$, then you can synchronize clocks by defining
t_2 = t_1 + f*(t_3-t_1)
The Einstein convention is to say f=1/2 but you can define a consistent theory with other values. These theories will have transformations other than Lorentz Transformations relating two frames, and will have an anisotropic speed of light in moving frames, but they are consistent. It is however not the standard relativistic theory. So I would say to summarize, you are correct that one can define a consistent relativistic theory with global simultaneity, but you cannot consistently define global simultaneity within "standard" relativity.
EDIT:
Here is a good stack exchange page discussing these notions a bit further
Ooh, now that is a fascinating point (as is the linked pdf). I'm vacillating between Reichenbach's proposal being absolutely brilliant and absolute nonsense. It's a lot to think about!
Yeah Reichenbach was an interesting guy. I knew this discussion had reminded me of something, and once I found that stack exchange answer it reminded me of The Direction of Time which I had started a few years back but never finished. I'm half inclined to dig it back out and finish after all this discussion.
Well, by the textbook definition of simultaneity this is strictly impossible (unless the speed of light is infinite, at least). I am curious exactly what you mean by simultaneous, then? Can you give me a simple example?
Again, this is about fictive mechanisms. Mechanisms that don't exist. The question is: is it possible to define them theoretically in a way that's consistent with the rest of our physics and doesn't make anything go wrong (like letting us communicate backwards in time)?
Upthread, you linked a stackoverflow question that said 'suppose one event happens at t1, and another at t2'. What does that mean to you (if it's coherent)? What would it mean for t1 to equal t2?
Sure. By the standard construction, two events are simultaneous when, after having positioned yourself exactly equidistant from the two events, photons radiating outwards from both events would hit your eyeballs at exactly the same time.
But I would emphasize that this can only occur in one frame.
But that definition is transitive, isn't it?—say observer 1 is equidistant from A and B, and observes them at the same time; and observer 2 is equidistant from B and C, and observes them at the same time; then A and C are also simultaneous.
In any case, what do you find problematic about defining instantaneous communication in terms of this definition of simultaneity?
I thinknot if observers 1 and 2 are moving at different velocities.Edit - Thinking about it more, you're essentially talking about some variation of Einstein's train. It is not transitive.
The reason it's not transitive is that light must appear to travel the same rate to all observers. If simultaneity were transitive, the moving observer must deduce that light moving the same direction moves faster than light moving the opposite direction. That's a contradiction.
So instead the moving observer sees the event ahead of him occurring after the event behind him, even though the stationary observer sees them simultaneously.
Einstein's train uses two events and two observers - but you can see the same inconsistency with your setup involving three events and two observers. Observer 1 sees event A and B as simultaneous, but sees event C after. Observer 2 sees events B and C as simultaneous, but sees event A after.
Critically: Observer 1 sees event A before event C, but observer 2 sees event A after event C.
Forgive the poor ascii art spacetime diagram; I hope it clarifies things. The arrows indicate direction of motion.
This is identical to Einstein's train if you take events B and C to be the same event. Observer 1 is the stationary observer and observer 2 is the moving one.
In general, that's fine. We can still say that A, B, and C happen simultaneously in universal time. (It would only be a problem if the observers were equidistant from all three events, which they're not in your diagram.)
With respect to the specific problem—I'll consider Einstein's train since it's more fully fleshed out. At the point when the observer on the train observes the first lightning flash, their position has changed, and they're no longer equidistant from where the two lightning flashes originally occurred, so we would not expect the conditions for simultaneity to be satisfied.
The pertinent question is the position of the observer relative to the events at the point when the events are observed. Not at the point when they happened.
Edit: one easy way to see that velocity must be irrelevant is the following. Re ascii art diagram this time. Suppose we have additional observers 1' which is stationary and equidistant from A and B and 2' which is stationary and equidistant from B and C. If the position of 1 coincides with 1' at the point when it observes A and B, then of course 1 must observe the same thing as 1'. If the positions don't coincide, then we haven't satisfied the criteria for proving simultaneity. Ditto 2 and 2'.
There is probably some setup with three events at the corners of an equilateral triangle, and observers moving between the midpoints of the edges of that triangle, that demonstrates some issue. I don't think I'm clever enough to figure that out.
There's probably some simpler example still that demonstrates the issue but, again, I'm not clever enough.
Yes, all observers observe the events in different order due to their distance from the event; but each can also use the distance to the event to determine how far in the past it occurred. When they all do this, they disagree on the order of events, not just order of observation.
Also, the lines of simultaneity for each observer change to the same angle regardless of their position. They each deduce the same order of events from any location, and they always disagree. It only depends on their velocity.
Yes, I think I understand what you're saying now. Pick a certain reference frame as "universal", and require any other frame to first consider a boost into that "universal" reference frame to say whether two events are simultaneous. I guess that's consistent, and all observers must agree on "universal" simultaneity.
I'm not sure how useful it is to discount velocity in general though. And, the choice of "universal" frame is arbitrary, so the relativity of simultaneity is still a problem in the choice of universal frame. You just mandate all the observers do some extra work to be consistent after the fact.
Edit: I think I got how to show the problem. (A problem? I've confused myself at this point).
Consider a variation of Einstein's train, where both observers observe the lightning strikes at the same time, in the same place, at the proper midpoint between the two strike locations.
To the moving observer, the strike ahead of them must have occurred before the strike behind them; but to the stationary observer, the strikes must have occurred simultaneously.
https://i.imgur.com/ci7c8g1.png
The problem with @psi's definition is that distances also depend on the chosen frame. Picking the midpoint between two arbitrary events requires first measuring the distance between the two events, and that requires first picking a reference frame where the events are simultaneous. That definition seems circular.
Of course, I meant when measuring in your own frame. I only meant to illustrate a setup that's easily envisioned. If you know where an event occurred (
x_A) (as measured in your frame, i.e. no length contraction), then you know when it occurred (x_A / cago). Assuming you observe both events at the same time, then checking simultaneity is as simple as checking whetherx_A / c = x_B / c, i.e. whetherx_Aandx_Bwere equidistant from you.If the two events were not equidistant from you and also staggered by a time
dt(with A preceding B), then you verify simultaneity by checking whetherx_A / c + dt = x_B / c. But notice that these calculations don't require appealing to the Lorentz transformations -- it's just a regular Galilean transform.I'm a little confused then - in my variation of Einstein's train, where both observers observe the events at the same time and location, the moving observer still deduces the events are not simultaneous by the formulas you listed.
Then the moving observer must also deduce that the strike ahead of them was farther away from them than the lightning strike behind them; since the light arrived at the same time but the events were not simultaneous. You can see this in the lengths of the two dotted blue lines on my diagram.
But the moving observer also detects both strikes exactly halfway along their journey between the sites of the two strike locations. It seems like a contradiction - how can the moving observer deduce they are closer to the strike behind them but also deduce they are at the midpoint between the two strikes?Edit: No, I got it. For the moving observer: they are at the midpoint when they observe the events. When the events occurred (in the past) they were where they came from. Obviously. Because it occurred in the past.
Edit edit: an approximation of the Lorenz transform into the moving observer's frame. The scale is certainly wrong but I think the angles are right.
https://i.imgur.com/gvD75WC.png
These diagrams look good to me. And yes, precisely -- in the second diagram (moving frame), the observer clearly isn't equidistant from both events despite observing both events simultaneously, so it's no surprise that they would conclude that the events were not simultaneous in their frame.
In the same frame, transitivity will work. But suppose you have events A & B equidistant in frame S, with observer S observing them at the same time; and suppose also you have events B & C equidistant in frame S', with observer S' observing them at the same time; then in general, if you were to stand equidistant from A and C, there is no frame in which you could observe A and C at the same time. You can find a fuller explanation here.
If you wanted to accept this definition anyway, transitivity be damned, then you would get the paradox I explained before: it is possible for an alien to coincide with my line of simultaneity, while the alien's line of simultaneity coincides with some time before I was born. Using such a definition, you could connect every point in spacetime, i.e. form the block universe discussed in the video.
If you accept @gpl's proposal (introduce a preferred frame of reference and define simultaneity with respect to that frame), then you must also accept that the speed of light is not a universal constant but instead has some preferred direction. Intuition about (1) simultaneity and (2) the universality of the speed of light are not compatible.
Why do we need the speed of light to be universal? My understanding was that our models are consistent with a bias in the speed of light, and—in the absence of instantaneous communication—this bias is not something we can detect. If we can accept a universal clock, surely we can accept a universal reference frame :)—at any rate, it seems much more acceptable than loss of causality.
I will take a look at that paper tomorrow—bedtime for me now.
Here is the most approachable discussion I've found (cc @gpl in case they're interested also):
As far as I can tell, it's impossible to measure the one-way speed of light (and at any rate, it would have no impact on the underlying physics), so there is no issue with using a non-standard synchrony.
Based on my understanding of the literature, you're more sympathetic to the anti-realist/conventionalist perspective, while I'm more sympathetic to the realist/non-conventionalist perspective. It seems like there are proponents of both viewpoints! Unfortunately the video takes the realist perspective for granted; it really would have benefited from discussing this issue instead of the growing block universe hypothesis, which strikes me as overly speculative and undersupported.
I'm not quite sure I really understand what you're suggesting, but let me dig into this proposal some:
My point isn't that there are merely many possible choices for "instantaneous" communication -- there are infinitely many ones, with each one being observer dependent. That was my hypothetical with the alien: if I could communicate instantaneously with an alien on a (moving) spaceship, then that alien wouldn't be able to communicate instantaneously with me (as we lie on different lines of simultaneity). Rather, they'd only be able to send messages into my future or past, depending on whether they're moving towards or away from me. Or put different: my "now" is necessarily different from their "now".
And this begets the quandary in the video: how do we make sense of this incongruity? If the alien is far enough away/moving fast enough, their "now" might occur before I was even born!
Even if two events are observed at the same time, that doesn't mean they happened at the same universal time. I explained my point a bit more here; perhaps that clarifies?
I'd been waffling on unsubscribing for Kurzgesagt for a while, and this video pushed me to finally do it. Lately it feels like they're doing more of these abstract theoretical concepts that don't make any sense when you try to actually follow what they're talking about.
Wouldn't a block universe basically qualify? All 3D slices co-exist in a 4D block. Each slice is a different "time".
Qualify as what?
As an idea you can write about on social media.
Just finished watching this video by Kurzgesagt - In a Nutshell and was curious about what people thought. How do you see time?
Not a scientist.
I believe we're living in a simulation. Lightspeed is a clock speed (CPU clock speed) limitation of the simulation, either a physics limit imposed by the simulation itself, or something coded into it deliberately to make the simulation manageable.
I love time travel stories. But I like the ones where they go into consequences and multiple branches, loops and fate. Watching this video, trying to keep track of "if X is traveling here, and Y is traveling there, but Z is doing this other thing..." it felt like the intended audience is mathematicians and physicists. Which is fine, but for the rest of us I couldn't help but think drugs needed to be involved to have a chance at following what they were trying to explain. Drugs or a degree, and drugs are cheaper.
I just do.
Things like lightspeed, and quantum mechanics. How can something just abruptly change once you've observed it, but before you do it's something else entirely. What we know about time, especially when the theories about black holes and such are brought into it just seem like the kind of thing that would come up if a computer was running everything. System's overloaded, too much on screen at one moment; chug, chug, chug and time slows down.
I'm not a physicist. Some who are have written about the concept (simulation reality). And proposed theories, experiments, and proofs. Not that it makes any actual difference to me, probably not to you either, or really even to the scientists; but if you put me up against the wall and scream talk, I'm going with simulation. We're all just bits and bytes in some sentient something's constructed reality.
It's fun to think about what they think about how the sim is going. Like, when the world wars broke out, were they concerned, or amused, or intrigued? Did they see it as us wasting our simulated time, or as us finding brutally efficient ways to settle our differences (rather than what's mostly happened in the 60s through to now, where we spend decades yelling across borders with only occasional, limited spats of violence that resolve nothing that cause the yelling or the violence)?
What do they think about us exploring the simulation? Is there an Antarian office pool running? "Six quadrabits on them not proving it until 2300, at least; they haven't even found out what happens when you spin up a wormhole yet!" And Bob, who's always an Antarian optimist, is shaking his head and putting his money on us figuring it out by 2170.
It's just a theory. But so is relativity, or so I'm told.
Because you or something touched it so you could observe what it's doing, relevantly, light in the case you may be thinking of. Your opinion sounds analogous to God of the Gaps, you prescribe whatever hasn't been explained so far by science to an agent of said simulation. As for your system overload analogy and lightspeed, while something I've thought about before as I'm just as guilty of using computing analogies, I just don't see how it's different than other physical laws we have in that regard. A universe wouldn't be a universe without basic physical limits and we wouldn't be to discuss it. Personally I find it interesting but in my limited reading, I haven't found the theory convincing.
The problem here is that you are designed and conditioned to think in terms of how the "human-sized" world works, and the building blocks of reality are not human sized.
The apparent contradiction disappears if you accept that your intuitions about how reality works are, at the most fundamental level, simply wrong, and that the human-sized world is a phenomenon that emerges from a fundamentally different set of rules.
Other people have made analogies for the collapse of the wave function, but I just want to clarify the word "theory" here. A scientific theory and the general English word theory aren't the same thing. Here's a scientific theory:
https://en.m.wikipedia.org/wiki/Scientific_theory
Other theories you might be familiar with are germ theory and atomic theory.
So you're right that it's "just" a theory. It's just that in science, theory is the highest possible thing a model can be. Thinking the world is a simulation isn't a theory, or even really a hypothesis. It's a reckon. Which is fine, I have many reckons myself. But they're not scientific theories, and neither is this. And if it's a position that you won't change your mind on them... well, that's just good old faith at that point.