Understood, so you mean e.g. for that color perception example you quoted above, at t=t1, the colors registered by the receptors change from c1 to c2 where c1,c2 are only functions of position? Let me clarify my point: In physics, velocity is defined to be dx_i/dt that is change in position w.r.t. time. and speed is the magnitude of velocity. In daily life (i.e. not in rigorous physics context), we said something is in motion (relative to us) if it has a nonzero speed (relative to us). When I came across some camps in philosophy and in physics who said "time is an illusion" and "time is an emergent property", I am often puzzled on how to understand velocity (and other time dependent qualities such as acceleration, force etc.) since for these camps either i) Time is not a fundamental quality ii) Time does not exist Therefore this gives some questions: 1. How to understand velocity without the quality known as time? 2. http://en.wikipedia.org/wiki/Four-velocity, even for the case of four-velocity, it is "change in spacetime position/Four-position w.r.t. proper time" and http://en.wikipedia.org/wiki/Proper_time proper time is "time elasped between two events as measure by a clock that pass through the events". How to understand it if time is really an illusion? 3a. Causality, which is a basic foundation in the way we think and is also something concerned by physicist (since they will usually be alarmed whenever their models showed results that violates causality) is closely related to time. How can one regain the observation that events happens in sequence (causality) if time does not exist? 3b. Even if we said we can model causality w.r.t. entropy (No. of accessible microstates (configurations in phase space (hence things like energy and momentum is also being taken account of)) for a given macrostate (constraint of the system)) and using the 2nd law (entropy tends to increase in an isolate system until maximized), how can it explain the perception that entropy increase spontaneously as in such scenario there is no such thing as time. If entropy is a function of position (similar to the gradient example, although in fact, entropy can be a function of many qualities, this is used just to illustrate the point in the arugment) then how can it reproduce the observation that we perceive things increasing in entropy for a given point in the system? 3ci. Ok maybe 3b is a bit too verbose, but what I want to ask in Q3 is: How to reproduce the effect of "time elapsed" and "causality" if time does not exist? (since these two things are what part of our daily experience) 3cii. Similarly for the camps "time is not fundamental", how can other physical qualities work together to give an illusion of time (or even spacetime)? Footnote: The reason I sometimes get confused by such ideas that suggest time is not fundamental or even exist is I don't know how to understand things like velocity, force etc. without time, since they are all changes w.r.t. time. Do these qualities still meaningful in a world without time (I just hope I have convey my point clearly as I know this is difficult for me to describe/explain my question) Using the quote here, what we perceived as motion is actually the change in the warping of spacetime between reference frames? (i.e. say spacetime in reference frame 1 looks like this:AAA an spacetime in refernece frame 2 look like this: DCG (note these are not meant to be maths, they are just letters to show the idea of being different))
StateOfMind: From your Post #1 What do I call the variable which is used in most equations relating to physics, orbital mechanics, et cetera? A special word (EG: time) seems handier than duration which might not be an exact synonym in all contexts. Duration implies a time interval in some contexts rather than being a reference to a continuous variable. Your two examples seem a bit clumsy. Our current vocabulary would express the above as: ForrestDean: From your Post #3: Even if neither time nor space exists, we still need some terms to express our perception. Assigning values for (x, y, z, t) seems useful, even if not necessary, for specifying when & where an event occurred.
Definitely. Otherwise it would be a bit challenging to participate appropriately in this particular reality. We play the game, we all participate in this reality and play our part, just as actors use props on a stage. The "experiences" of our perceptions are real, but we're only experiencing an illusion - a fabrication of our Mind. "Time" and "space" are not absolute, and they have no basis in reality. They are nothing more than subjective experiences based solely upon our perception. So yeah, I can play the game. I can flow with whatever labels we choose to place on certain aspects of our experiential reality. I'll just have fun with it. Please Register or Log in to view the hidden image!
This kind of off-topic and on-topic at the same time. sciforums is a filter - the absurdity of it @Dinosaur: Yah my examples were a little bit forced. My intention wasn't to invent snappy alternatives but to examine what is in the box called "time". You're right, time, in the scientific usage, usually refers to a variable duration - but I mean, "duration" doesn't imply any particular unit of measurement either - and then it doesn't have all those pesky connotations of "past" and "future"; which, what is the nature of "past" and "future"? - I can't shake the feeling that this is a philosophical investigation rather than a physics problem, something more to do with the wiring of our brains than the nature of matter. This is off topic now but I'm just kind of amazed with the fact that I start a topic about this idle curiosity I had one day, and how various members of the sciforums community sort of pulled it towards their own agenda, as if it were this putty-like substrate with a lot of elasticity - ways I didn't expect or intend. It's a great example of entropy really. By the year 2030 this thread will have discussions about unicorns that are completely in context. At this point there's two or three serious side-discussions that branched from it, and for me to create quality responses to each of them would require me to quit my job and become a forum poster full-time (are there any openings??). Lot's of interesting reading though from thoughtful posters, wish I had more... time.. to help out with the growth. That's a good word for this btw... a "growth". Time will tell if this thread grows up to become a contributing member of the sciforums society. I personally hope it gets fast-tracked and becomes a child-star, reaching the height of sciforums fame and success before most other threads get to the freaking point already, only to encounter debilitating mental issues from having its childhood essentially stolen. It's something to shoot for.
Two paragraphs from Page 8 of the document cited by Forrest Dean in Post #15: Your POV might seem profound, but I disagree with it. Time is not meaningless: See Post #14, which provides an excellent POV for it. Modern physicists define the second in terms of the frequency of some atomic phenomenon, which makes it an objective & precise definition. The old definitions based on planetary orbits were useful until some time in the late 19th or early 20th century, after which modern physics needed a more precise definition for units of time. Concepts based on three spatial dimensions & time provide excellent models for dealing with modern physics, with distance & time treated as continuous variables. This model allows the use of Differential Geometry (a powerful tool) as the mathematics of General Relativity. Perhaps some quantum POV will become necessary in the future for dealing with quantum level phenomena. I doubt that we will ever require a fourth spacial coordinate for modeling physics, although there is a lot of mathematics relating to 4D (& higher) geometry. Knowledgeable people have known that the world is not flat for thousands of years. Sea faring cultures (Example: The Phoenicians, circa 1500 BC to circa 300 BC) knew it was not flat due to observing mountains and tall structures when approaching land. Similarly those on the land could see the topmost part of a ship prior to seeing the rest of it. Circa 200 BC a Greek scholar living in Egypt estimated the circumference of the Earth with about a 5% error. Note also the following from Wikipedia: Knowledgeable folks knew that our solar system is heliocentric for almost 500 years. Some comic once said: The above is expressed as humor, but has a lot of merit. BTW: Note that Classical Physics has been used for all of NASA’a activities until recently. The geosynchronous satellites used for our GPS technology requires General Relativity (& perhaps Special Relativity) corrections for the clock devices in the satellites. New theories of physics hardly ever replace the old theories when considering only the experiments and measurement precision on which the old theories were based.
Agreed. The whole premise of this thread is sheer nonsense! There are thousands of examples and one very clear one is that without allowing for time we NEVER could have placed a space probe within a million miles of some distant planet. To put it plainly, the concept that "Time is dead" is nothing but garbage.
I just posted this in another thread but its worth repeating here. "The constant mystification of something as empirically self-evident, and simple, as time is confounding." Take a step back, look at the evidence, and stop trying to squeeze it into what you want, or what you thought you knew.
How could we know how consistent the frequencies of atomic phenomena are? It's a bit like trying to lift the chair your sitting on, isn't it? The only way we could examine it's consistency would be to find another basis for time that's even more stable, and then examine it with that as our reference point. Of course we're back in the same predicament with that new reference point all over again. But atomic frequencies are precise enough for now, sure, with what the people of the year 2193 call our "caveman physics". I'm sure once we need more power for our rockets, or speed for our computers, the new hero will swoop in and save the day just in the nick of time, just like it always does. Science is busy looking for the boson so they can finally rest easy knowing the universe is essentially a bunch of legos, but it seems only the eastern-religious nutjobs are willing to explore the idea that the universe is continuous, making it theoretically infinite with no end to the rabbit hole, sorry dorothy. As much as my left-hemisphere wants everything to be a big sandbox I think a spinning hourglass is closer, as well as prettier and more poetically satisfying.
I agree with the OP. It's similar to what I said in a Time Explained thread. That's an old version, there are newer better ones kicking round the internet. I'm John Duffield by the way. And what I've said isn't some big idea of mind. The idea that "time is change" dates back to the ancient Greeks. Check out Epicurus. More and more people are coming out with this sort of stuff these days, which is good IMHO. I say that because I'm a "relativity guy" amateur who sticks close to Einstein. See A World Without Time: The Forgotten Legacy of Gödel and Einstein.
I was thinking about time and space, in terms of an animal's perception, for example a dog. Superimposed on their perception of time (time to eat) and space (location of the bone), the dog also has another or z-axis called scent. The dog uses space-time-scent as his coordinate system. Scent works with space-time to reveal additional aspects of location, directional vector, time sequence (tracking) and chemical composition from which he can infer food, prey or predator with respect to position and vector, in the past, present and future. The scent of the dog makes use of mass and atomic composition superimposed on space-time. How would this extra axis impact our perception of space-time? Or do humans separate space-time from mass properties (scent connected) because the latter has substance and the former is more of an imaginary grid that is defined by convention?
That is like biting the hand that fed you, and that is downright ungrateful. Ever heard of the word progress? You start basically at ground zero (man has zero understanding of existence) and you BUILD UNDERSTANDING on the foundation that you define. As time elapses understanding builds on previous understanding. In other words, you can't count to 10 unless you already counted to 7. And then you come along after you get to 10 (in year 2193) and laugh how primitive 7 was. (Rolls Eyes)
Getting back to the dog and using the coordinate system of scent-space-time, his approach is substance before abstraction. The scent is the trigger by which the space-time attributes appear as a secondary inference. The dog smells the tracks and he knows direction, time and distance. Putting chemical substance first makes sense since substance is the source of food or predictor, not time and space. From this I would infer space-time is more modern human and is an artifact of free will and choice. If you put substance last, this is useful for extrapolating outside and beyond nature, using science and engineering. We plan in space-time and then build. Space-time is useful but it is not natural to place substance as a secondary by-product. Or space-time allows one to contrive beyond natural reality into synthetic.
I mean, really, WTF are you trying to say? Sometimes it really seems like english is not your first language.
@Farsight It doesn't surprise me at all that people have come up with this idea many times before. The idea that time is change seems so self-evident that I'm surprised there's any debate. And I don't think there is, it's just we're not all using the same definitions from what I can tell. True. I've been realizing lately that more patience might benefit me. You're totally right though.
Stateofmind: I'd say there isn't much debate. But I'd also say there's a lot of "celebrity physicists" writing books about "the mystery of time" who don't want anybody raining on their parade. I wrote another essay recently here. Check out Amrit Sorli's From space-time to space-motion too.
