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Does time really exist?
Chaos Punk
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I got a call at the office tonight that my copy of Daniel Falk's book, "In Search of Time: The history; physics, and philosophy of time", had arrived fedex today. I've been pretty excited to read the book, since some things about time are kind of perplexing to me. Felt like it would be a good day to ask the PA their take on it.....
Does time really exist?
(1) If time does not exist, then how to we explain recovery from wounds, hangovers, pain? Adaptation?
(2) If time does exist, then at what rate does it move? What is the duration of time?
Here is the present time paradox that I thought was interesting:
If there is neither past, nor present, nor future, then what is there?
Does time really exist?
(1) If time does not exist, then how to we explain recovery from wounds, hangovers, pain? Adaptation?
(2) If time does exist, then at what rate does it move? What is the duration of time?
Here is the present time paradox that I thought was interesting:
The past and the future do not exist; they are not there, in the world. Perhaps the past once existed, and perhaps its effects can still be seen in the world today, but the past doesn’t exist now; if it exists now, then where is it? And perhaps the future will exist one day, but it doesn’t exist yet; again, if it exists now, then where is it? The past and the future clearly do not exist; the universe consists only of the gap between them, the present.
How large is the gap between the past and the future? What is the duration of the present? A minute? A second? A nano-second?
Clearly the present does not last as long as a minute. A minute consists of different temporal parts. First comes its beginning, then its middle, and then its end. Each of its parts occurs at a different time. If its beginning is present then its middle and end are future. If its middle is present, then its beginning is past and its end is future. If its end is present then its beginning and middle are past. If the present lasted as long as a minute then it would consist of past, present, and future elements, but that would be absurd; the present must be wholly present.
The same, though, could be said if the present were of shorter duration, lasting only a second, or even only a nano-second. In either case, the present would have temporal parts: a beginning, a middle, and an end. If its beginning were present then its middle and end would be future. If its middle were present, then its beginning would be past and its end would be future. If its end were present then its beginning and middle would be past. If the present has any duration at all then it consists of past, present, and future elements, but that, as I said before, would be absurd.
The present, then, has no duration; there is no gap between the past and the future. It has already been seen, though, that to say that something has no duration is to say that it does not exist. The present, then, like the past and the future, does not exist.
How large is the gap between the past and the future? What is the duration of the present? A minute? A second? A nano-second?
Clearly the present does not last as long as a minute. A minute consists of different temporal parts. First comes its beginning, then its middle, and then its end. Each of its parts occurs at a different time. If its beginning is present then its middle and end are future. If its middle is present, then its beginning is past and its end is future. If its end is present then its beginning and middle are past. If the present lasted as long as a minute then it would consist of past, present, and future elements, but that would be absurd; the present must be wholly present.
The same, though, could be said if the present were of shorter duration, lasting only a second, or even only a nano-second. In either case, the present would have temporal parts: a beginning, a middle, and an end. If its beginning were present then its middle and end would be future. If its middle were present, then its beginning would be past and its end would be future. If its end were present then its beginning and middle would be past. If the present has any duration at all then it consists of past, present, and future elements, but that, as I said before, would be absurd.
The present, then, has no duration; there is no gap between the past and the future. It has already been seen, though, that to say that something has no duration is to say that it does not exist. The present, then, like the past and the future, does not exist.
If there is neither past, nor present, nor future, then what is there?
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Cantor would like to have a word with you.
I dare not risk talking about the article in more depth until I have read it 500 times, at which point I will understand it or have gone mad.
From an engineer's perspective: Time is relative, which makes it incredibly difficult to measure and synchronize when you need sufficient amounts of accuracy (for high values of "sufficient").
General relativity: Clocks higher up in a gravity well (e.g. on sattelites) tick faster than ones lower down. By "clocks tick faster" I mean "time itself is actually moving faster when you are in a weaker gravitational field". So if you need precise time synchronization with a satellite, this needs to be accounted for, or you will get drift. And this doesn't just affect sattelites! The network of atomic clocks that measures "official time" (UTC) needed to get skewed by a few (astonishingly small) fractions of a second because some were in buildings higher above sea level than others. Yeah, the difference in gravitational strength due to elevation differences at different universities was enough to desynchronize the only somewhat objective measure of time we have on this planet.
Special relativity makes things extra fun: a moving clock will tick slower than a non-moving one (assuming that you're the "non-moving" reference frame here). So if your satellite is not geosynchronous (The NavStar GPS constellation, for example, is not!) then you need to account for this as well.
Then there's regular old non-relativity inaccuracy. At least those atomic clocks are more accurate than the finicky bullshit that we call "the Earth's rotation". Leap seconds? Ha!
Then, for smaller values of "sufficient", you end up with stuff like all the bullshit that your computer clock goes through to sync to an NTP server. One-way transmission time is essentially impossible to pin down so it needs to figure out averages of round-trip time, but there's all sorts of nondeterministic delays along the stack from your Internet connection to the real-time clock on your computer. When it's not synchronized, it will drift, startlingly badly. (I've seen computers that would lose several milliseconds per second. That's kind of serious when you need to figure out what sensor got what signal first, or who bought a thousand shares of FOO before selling them to someone else and at what price, or what have you.) End result: you can have two computers in the same room and you can't do better than about ten microseconds of skew without resorting to "exotic hardware" or "not running your software in an 'operating system'"
So, yeah, time is bullshit. Fuck this whole "time" thing.
also:
"Time does not exist. Only the illusion of memories exist."
*Bonus points to whoever knows the reference without searching.
Time absolutely exists.
Time is a measurement. It is not unlike space. At what rate does time move? I dunno. Pick a point in space - how big is it? Is it a foot long? An inch long? No, dude, shut up, it's a point, it doesn't have a size. And the "present" doesn't have a "duration". The past no longer exists in the same sense that I am no longer in my bedroom after I've gotten up and walked to the damn bathroom to take a whiz.
Time is a car that is moving along, and we are all in the car. No matter how you romanticize it, that's about how exciting time is. It's a long road trip in a beige sedan from some fucking Hertz and the only radio station you can get is easy-listening from the early nineties. And also the car smells vaguely of old cheese because the last guy who took the universe for a joy ride spilled nachos all over the Local Cluster.
Only Zuul.
I'm not sure that I know what this means. My understanding is that time is part of the system for measuring things. We don't usually ask questions like, "At what rate does length change?" Without actually measuring the length of something.
Perhaps I'm misinterpreting quantum theory, but I believe you can consider the "present" to be one string long.
I think the term you're looking for is Planck time.
Is that based on string theory? Because I'm pretty sure string theory is still considered unprovable hokum, unless something has changed really recently.
edit: Ah, Planck time makes more sense. Still, I don't think time being quantized necessarily means that the present has a length. The present is still just a discrete point on the timeline, and points don't have width by definition.
Sounds a lot like this to me:
http://en.wikipedia.org/wiki/Zeno%27s_paradoxes#Achilles_and_the_tortoise
As nothing can travel faster than light, the smallest measurable amount of time is the amount of time that light takes to travel one Planck length. And I don't mean that "it's really hard to build a machine that detects the difference." I mean that there is no difference in a moving object's (or a photon's) location if measured twice within a single unit of Planck time.
http://en.wikipedia.org/wiki/Planck_length
http://en.wikipedia.org/wiki/Planck_time
So the present does have a duration.
Hack.
Not time travel.
rate of change of time = dt/dt = 1
duration = integral from 0 to t dt = t
i'm not just being dismissive, they're meaningless questions
you're asking to measure a quantity relative to itself, which makes no sense. It's different when you're talking about relative rates of the passage of time in relativity because it's comparing time in one frame to time in another, or dt'/dt (so two different things).
Sort of, yeah.
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I am ignoring a lot of your post, but I feel other people covered it much better.
This stuck out to me because you invoked biology, and while I may not know physics very well, I at least know biology.
Time, as far as I can tell, is a measure of change or movement relative to the universe*. The way I see it, there is a reason whenever someone "freezes time" in science fiction, everything physically stops- there is no way to measure time without measuring it relative to some change in an object (be it distance, energy level, excitation state, or what have you).
If I remember correctly, some really famous guy explained this much better than I did....what was his name?
.....
Anyway, what really got me was the word "adaptation", which I think is where the stumbling block for you is. 'Time' definitely exists, but what we call "time" and how we define it A. may not be correct yet and B. are definitely human concepts superimposed over natural forces in an attempt to explain them.
Similar to evolution (going with this because "adaptation" is a much bigger fish) it is a thing that happens and we are doing our best to try and describe "time". But also like evolution, the way we talk about time is only a human understanding of the phenomena- it may not accurately model or describe the phenomena fully, but that doesn't mean the phenomena doesn't exist.
This is key- you can come up with all sorts of paradoxes and mind benders and tautologies and crazy logic when you start really probing at the idea (especially if one starts off on false premises) but that doesn't mean that time doesn't exist. Rather, it may mean that we need to restructure the way we view time, but this isn't really new, and from what I understand has happened before.
Anyway, kind of rambling a bit- I will let the physicists take over.
*the universe or something. Please correct any errors you find in here physicists and you will earn one free "Arch corrects your biology without judgement"
I'm not sure what you're getting at, but you could stick someone in a dark room and they would still "know" that time is passing -- they just wouldn't have any reference as to how much.
Of course.
Unless, and this is crazy, they used literally any other method than looking outside.
I mean, you realize some people never see light, right? They manage to tell time without needing it explained to them.
Exactly, the passage of time can be completely internalized and doesn't require any outside source to mark it's occurance. If someone was literally floating in a complete void with complete sensory depravation but that person still existed and was alive then they could mark the passage of time based on another measurement such as their thoughts. As they think and move from one thought to the next they would preceive time. An example being, "back earlier when i was thinking of Pizza but after I wondered what Mila Kunis tastes like.
They could also just count either in their head or aloud and whether their tempo was consistent or not it would still give them reference points to measure the passage of time by.
Yes? That is my point. As long as you have a way of organizing a series of events there is time. Even if you had no physical senses at all, your mind would create it's own local time.
Arch,
https://www.youtube.com/watch?v=t_goGR39m2k
You mean time?
Yeah, I always get annoyed when people talk about time as if it's a dimension in any way similar to the three spatial dimensions. And whenever one bring up the concept of 4+ spatial dimensions people always chime in with "But I thought time was the fourth dimension?"
No, it isn't.
It's a temporal dimension that combined with the three spatial dimensions become spacetime - even in the name you should see that it is a wholly separate thing.
When people start using "dimensions" as some sort if generic catch-all phrase for various phenomena in this universe it probably just result in more confusion for your average joe. A great example of this is that silly video where they're trying to explain 10 dimensions and where each next dimension is just some concept such as alternative realities or "infinity" and putting it in the same category as the three spatial dimensions without much logic.
No. Also, Yes.
Or, rather, in long-form, if light didn't exist in the universe and something so completely analogous to light that we may as well just call it light also did not exist then the universe as we know it would not exist. The entire structure and function of the universe is absolutely and irrevocably dependent upon the existence of electromagnetism. Light, by any definition, is electromagnetism. The universe without electromagnetism would be so utterly different from ours that almost any question you'd care to pose in the frame of our universe would have to be approached completely differently in an EM-less one.
We would be completely unable to detect the passage of anything in an EM-less world because all of our sensory functions are based on EM interactions. Some hypothetical measuring device that exists without a reliance upon EM for its structural integrity and function and which is able to measure strong, weak, or gravitational interactions, however, would be entirely able to detect the passage of time in a lightless world.
2)
A Planck <unit> is not 'the smallest <unit> in the universe'. It is entirely possible to have durations and distances below the Planck scale. It is, however, impossible to measure them. Planck's constant is a term which appears frequently in any calculation involving quantum-scale effects. This is due to the Heisenberg Uncertainty Relation between non-commutative operators acting on quantum systems.
Any transition between a state P and a state P' of some quantum system can be described as the action of one or more 'operators' on the state P. So, in braket notation:
X|P> = |P'>
the X is the operator. Hermitian operators have various mathematical properties, but the important bit is that their eigenvalues are real, which works out to mean that the expectation value for a Hermitian operator is nearly always an observable quantity (position, energy, momentum, etc). So, for instance, the expectation value <p|X|p> with X the translation operator is the position of the particle p. Non-commutative operators are Hermitian or not (it's not important to the commutativity) and have a commutator [X,Y] =/= 0, where
[X,Y] = XY - YX
more or less.
Heisenberg's uncertainty relation, in terms of operators, says that, for certain non-commutative operators, [X,Y] ~>= ih-bar
Where i is the imaginary number i and h-bar is planck's constant over 2pi
The most common and well-known uncertainty relation is position-momentum, [x,p]. Stated another way,
dX*dP >= ih-bar
says that the uncertainty in position times the uncertainty in momentum is greater than or equal to a fixed quantity. Meaning that
dX >= ih-bar/dP
or that the smaller the uncertainty in momentum (dP), the greater the uncertainty in position (dX). The fixed constant of proportionality for the minimum ratio of dP to dX is h - Planck's constant. The absolute closest that you can ever measure the position of a thing to is equal to h*(i/2pi). At this point the momentum uncertainty spans the range from zero to infinity. This distance is a 'Planck length'. Things can happen inside the distance expressed this way, and frequently do, but we can never measure them with certainty. Does that mean they don't really happen? I dunno; it's philosophy.
A less well-known uncertainty relation is the 'Energy-Time' one. It so happens that [E,t] >= ih-bar as well, meaning that dE*dt is a quantity with a fixed minimum proportionality. Or, you can't know very exactly how much energy a system has without letting the time over which you measure it get a little fuzzy.
The problem with Energy-Time uncertainty is that the time operator, t, does not correspond to any observable quantity. Or, rather, it doesn't correspond to a quantity inherent to the system. You can't measure an electron and say how much time it has in it. Or at what time it exists. You can measure it and get a time-delta; a span of time which has elapsed. This is entirely different from other operators, leading many people to believe that time is not a proper quality of systems and that our time evolution operator is actually exposing some more fundamental underlying property. What that is, if there is one, we have no idea.
The closest we can get to saying anything really fundamental about time is that entropy over time always increases. Except that there are a class of materials wherein one can actually carry out a reversible cycle involving a net zero entropic change, effectively moving the surface backward in time (if you're using entropy of the system as your clock).
td;dr: Time as a physical thing probably doesn't exist, but it certainly appears to exist and in almost every application this is good enough.
Ah I see, I misinterpreted it on account of it being a ridiculous question.
CptHamilton answered it better than me though.
Although I don't feel that a thing without any ability to sense whatsoever would develop the concept of time. I mean, what's going to be the useful aspect of that? What exactly are your thoughts? " " forever? I mean with literally no senses at all there's simply nothing to separate now from then, or even life from death.
I couldn't have said most of that on my own and I can't argue about any of it or understand where some of it is coming from, but I can follow and accept all of it and understand what it means so now I wish I had a bigger background in physics.
Thanks. At last my degrees are useful for something!
A more interesting question about time and our perception of it: are we, as a species, capable of actually observing the 'present'?
There are fundamental delays in our sensory apparatus. Hearing, for instance, has minimum response times built into various stages of the pathway between your ear drum and the acoustic processing centers of your brain. I want to say that there's some nerve center or something named after an octopus that has a response time measured in the hundreds of milliseconds, but I may be misremembering the one colloquium I went to about human sensitivity to frequency shifts several years ago. I know there's something in your head that's slow, at any rate.
Given that it takes time for signals to reach the parts of your brain that can think about them and that there are further delays for you to actually do any thinking (it takes significantly longer for you to realize a pot is hot, for instance, than it does for your body to react and pull away from the hot pot), are we ever sensing the present world? Or are we always considering events that have already entered our short term memory buffer, somewhere between milliseconds and full seconds ago?
I'm not sure that it realy matters, but I think it's neat to think about.
Critical Failures - Havenhold Campaign • August St. Cloud (Human Ranger)
In that sense it's true that we're never sensing "the present" as popularly conceived, because all the sensory input we have has taken a non-zero amount of time to get to us, in addition to the time our brains spends processing and whatnot.
But more than that, we have to remember that Special Relativity pretty much kills the notion of simultaneity entirely. Even if you try to extrapolate backwards from what you see and hear to determine the precise moment that something really happened, the fact is that when it happened depends on what reference frame you use, and two things happening at the same time for you could be happening seconds or minutes or years apart for some other viewer.
So no, we're not seeing "the present", but more importantly there isn't a single "the present" to consider. In order to really order events properly, you need to incorporate spatial dimensions into your figuring, and basically speak in terms of "this happened at these coordinates in spacetime according to this reference frame."
Reminds me of a Dr. Bronner's bottle.