Does time exist...

[djviscera]

I dont think there is such a thing as time. You cant stop time, you cant go back in time, you cant go foward in time. Even if time does exist how do we know which direction we are going in. Everything we know is 3 dimensional so why would time be linear. Either I am crazy and dont know what I am talking about or I need to go to sleep.

[tezza98]

time is the arrow of thought. if you dont htink then there is notime,\.if there is no time then you are inthe forth dimension. i seen it what did you see?

[djviscera]

the 4th dimension is very hard to explain with words, i saw it when i was on lsd and all i can say is that the possibilities for moving seem endless compared to the way we do things here.

[Keiji]

I dont think there is such a thing as time. You cant stop time, you cant go back in time, you cant go foward in time. Even if time does exist how do we know which direction we are going in. Everything we know is 3 dimensional so why would time be linear. Either I am crazy and dont know what I am talking about or I need to go to sleep.

You can go relatively (keyword) back or forward in time by accelerating to a fraction of the speed of light.

At the speed of light you will cease to age, which is why travelling at the speed of light is impossible as if you cease to age you would observe the rest of the world aging infinately in what seems to you to be zero time.

[Geosphere]

Time is something that prevents everything from happening all at once, which would just be too confusing.

It is our way of interpreting actions. Time measurement is purely imposed by man.

[elpenmaster]

i dont think that you can really go back or forth in time at all. if you accelerated really fast, everything else would just look like it was going slow, but you would be perceiving and aging slower. things would happen slower, as in over a londer period of time. it might take you 111 years to brush your teeth. not because time had changed, but because your existence had slowed down

[jinydu]

i dont think that you can really go back or forth in time at all. if you accelerated really fast, everything else would just look like it was going slow, but you would be perceiving and aging slower. things would happen slower, as in over a londer period of time. it might take you 111 years to brush your teeth. not because time had changed, but because your existence had slowed down

Actually, if you took a clock and measured how long it took you to brush your teeth, it would still be quite normal. You wouldn't notice anything. However, people in a different frame of reference might claim that it took you 111 years to brush your teeth. However, you would claim that THEY took 111 years to brush THEIR teeth. Remember, you do not observe yourself moving at almost the speed of light. You observe yourself as stationary, while the rest of the universe is moving backwards at almost the speed of light.

[mghtymoop]

time obviousely exists, whether it exists as we see it or not is of no consequence because the only thing that affects us is our interpretation of time itself. however under certian extreme conditions you could suggest that time does not exist. one possibility is within a 'wormhole' created by exotic matter as a shortcut through the 4th dimension to another point of the original 3d universe. this however becomes a little confusing when you see that within a single 3d universe not all points are at the same point in the 4th dimension but rather a little 'blurred' i wonder a what point you would be considered to be in a different time in the past or future if you travelled in this way and how large the 'blurring' is. another point at which time may not exist is a super light speed, because how can time possible get any slower than stopped but at above light speed you would have to assume that it does, perhaps travel through time could be reversed at these speeds but the relationship of the assymptote suggests that this is probably not so, because gravity for one would have to go above inifinate at this level and seeing that you cannot get any higher than infinate gravity it is probably so that time would not infact reverse but just become detroyed.

[jinydu]

Actually, if you observed someone travelling at faster than the speed of light, you would observe that they were going back in time, creating all sorts of problems.

But don't worry. Reaching the speed of light takes an infinite amount of energy, so we don't have to worry about this happening in real life.

[Geosphere]

Reaching the speed of light takes an infinite amount of energy

Sorry, I don't buy that. Too many problems with it.

[jinydu]

Its a simple application of Special Relativity (SR):

Relativistic Mass = Rest Mass * Gamma

As the velocity approaches the speed of light (relative to the observer), gamma approaches infinity. Hence, relativistic mass also approaches infinity. The kinetic energy of a body is given by

KE = (Relativistic Mass - Rest Mass)*(Speed of light)^2

Since Rest Mass and the Speed of Light is constant, the right-hand side approaches infinity as velocity approaches the Speed of Light. Therefore, kinetic energy approaches the speed of light. By the conservation of energy, an infinite amount of energy is needed at the beginning in order to gain this infinite amount of kinetic energy.

You might also try to reach the speed of light by "adding up" velocities. For example, you get into a rocket and fire up its engines until you reach 0.9c (where c is the speed of light) relative to the Earth. Then, you fire a secondary rocket forwards at 0.9c relative to you. You may think that observers on Earth view the secondary rocket as travelling at 0.9c + 0.9c = 1.8c. However, velocities don't add up so simply in SR. The correct expression is in fact:

(u+v)/(1+(u*v/c^2))

Hence, observers on Earth will observe the secondary rocket moving at about 0.9945c, still below the speed of light. If you are very persistent, you might try firing a tertiary rocket forwards from the secondary rocket at 0.9c (relative to the secondary rockeet). However, this still won't exceed the speed of light (relative to observers on Earth). Instead, observers on Earth will measure the speed of this tertiary rocket at about 0.999708c, closer to the speed of light, but still not there.

In General Relativity (GR), there are some mathematical solutions (such as wormholes) which make things more interesting. However, using wormholes isn't really travelling faster than the speed of light because a spaceship would still be travelling slower than light that passes through the wormhole. Furthermore, all supposed methods for travelling faster than light rely on at least one thing/technique that has not been proven to exist/be possible. For example, it is generally accepted that black holes do exist, but as far as I know, there is no evidence for white holes (the other end of the wormhole).

[Geosphere]

Doesn't mean I have to believe it.

[mghtymoop]

it doesn't take infinate energy to reach 3*10^6 m/s but it does to reach c due to relativity because c is always faster than the travelleler, why is it so have to beleive that reaching infinate speed requires infinate energy. you can only reach light speed where relativity doesn't work, only experment i've heard of where relativity doesn't work is at about 0 kelvin where the light was shone through a superdense laminar solid with alternative layers of flowing oil of high refractive index. light was slowed to walking pace

[jinydu]

As I understand, this does not mean that Relativity doesn't work in that situation.

The measured speed of light actually depends on the medium in which light travels. Light travels fastest in a vaccuum, slower in air, slower still in water, even slower in the superdense solid you're talking about. It IS possible to travel faster than light in mediums other than a vaccuum. The result is a phenomenon called Cerenkov Radiation when the particle exceeds the speed of light (somewhat analogous to a sonic boom for sound) in that medium. For more information about Cerenkov Radiation, please see http://www.fnal.gov/pub/inquiring/matte ... ction.html.

However, when Einstein talked about the speed of light in relativity, he meant the speed of light in a vaccuum. Hence, slowing down light by putting it in a dense medium does NOT violate the theory of relativity. If you were able to slow down light while it was still travelling through a vaccuum, that WOULD violate the theory of relativity.

In any case, on a microscopic level, light NEVER slows down (as far as I know). This is because most matter is really just empty space, with some sparse atoms. When a photon travels through matter, it occaisionally gets absorbed by a bound electron, causing the electron to move up to a higher energy level. A tiny fraction of a second later, the electron re-emits the photon and drops back down to its ground state. However, this process does take some time, increasing the amount of time needed for the photon to pass through the object. Since speed is just distance divided by time, this increase in time is measured as a decrease in the speed of light by macroscopic observers (like us). But in reality, the light was always travelling at the same speed, c. Its journey just took longer than usual because it got interrupted ("ran into traffic", if you like). Hence, the superdense solid you discussed doesn't actually decrease the speed of light. It just causes the photons to start and stop so many times that the journey takes much longer than usual.

[Aale de Winkel]

quite correct jinydu, reading your vaccuum point I just thought of what would happen if you created some kind of ring which would create some heavy gravity in its center (be aware currently merely a thought experiment) this would seem to slow down passing photons without violating relativity. However it would seem that way, since actually space would collapse in such a matter that the seemingly slowed down photon would tavel at c to a squeezed part of space.
This situation I thought of would make traveling at warp possible, however given the reasoning here I do think I have to reconcider this point, unless the Cerenkov Radiation situation (you mentioned) might be appliccable here, and one could travel through a "space-fold" faster then light does?
Too bad this has to stay a "thought experiment" currently, I don't know how one might construct a "star-gate" (a la Buck Rogers) described above

[jinydu]

Another important point is that, according to GR, gravity does NOT slow down light. Instead, when a photon escapes from a gravitational field, it loses energy by decreasing in frequency according to Planck's equation:

E = hf

where h is Planck's constant (6.626*10^-34 Js, if I remember correctly).

Thus, Cerenkov Radiation is impossible in a vaccuum, even in the prescence of a gravitational field.

[RQ]

As Aale de Winkel mentioned, Cerenkov radiation is released when a photon is slowed down by colliding with matter, and a particle (near it) could then travel faster than light (not c just the light there) and if it does, like a plane traveling faster than sound makes a boom, faint radiation is released from the particle, called Cerenkov radiation.

Oh and without time, in this universe, we wouldn't be sitting here talking about it if it weren't here.

[monkeymeister]

Time is basically change or the rate of change.

It cant exist within one "frame of existance" because it is continual.
If somehow time were to stop for millions of years then restart nobody would of have noticed the difference.

I dont think anybody claims to know for a fact that time is linear. Its just that our society is so bent on God. As a society we believe over time we progress along "God's plan" or something like that. And "God" in western societie's mind is omnipresent, all powerful and all knowing so he couldnt have a change of plans.

I however do not believe that time travels in one direction. To me time exists one every dimension or at least between the transition from one to another. Every moment is a 0 dimensional point. Over time/change the point grows into the only possibile direction it can change into which is a 2 point line. Now for the line to change it can either grow outward, staying a line. But ever since the first point changed it covered everything linearly so grow outward does not really provide change. The only possible change is for the line to bend or for a point to branch off from the line. With this change you get the second dimension...This can branch into the 3rd dimension and so on... The thing is though that every point has an infinite potential of direction and with each new dimension it gains another degree of inifinity. To prove time is linear one would have to prove each point in time only has one choice of change. I believe that we live in once linear tracked of time that our scientific laws govern, making it only possible for one result but in the begining of all this the laws that govern the universe today may not of been the same, creating alternate tracks of time that constantly intersect this one. Each intersection, i think, defines a point in time and i could gooooo ooooon annnd ooooon about this idea but its still in thinking

[jinydu]

Probably the least problematic scientific definition of time that I know of comes from entropy in thermodynamics.

Basically it says that as time increases, the total amount of disorder in the Universe increases. Thus, if the entropy of the Universe is higher at one moment than another, we say that it is more "forward" in time. However, this definition suffers from the fact that entropy doesn't always increase at a constant rate, making it difficult to define a constant unit of time.

Personally, I think that time is something that is probably best left undefined. Let's face it: Its impossible for everything to have a definition. Or to put it another way: Its impossible to construct a monolingual English dictionary that contains every root word in the English language, and doesn't contain any circular definitions. This is because any word can only be defined in terms of other words, which in turn must be defined by other words, etc. But eventually, this process must end because there are only a finite number of root words. Ultimately, some words must be assumed as understood, without a definition, so that more complex words can be defined in terms of these "assumed words." I have a similar idea about concepts like time. I don't think its possible to define time, unless you can think of a concept that's simpler and/or more fundamental; but I don't think any such concept exists.

[RQ]

Probably the least problematic scientific definition of time that I know of comes from entropy in thermodynamics.

Basically it says that as time increases, the total amount of disorder in the Universe increases. Thus, if the entropy of the Universe is higher at one moment than another, we say that it is more "forward" in time. However, this definition suffers from the fact that entropy doesn't always increase at a constant rate, making it difficult to define a constant unit of time.

Yes, although time is relative, to an observer at rest with respect to the Earth(since we are living on it) we can't measure natural time, thus we invented mechanical time which is the standard second measured by the Ceasum133 clock which as far as I know measures one second by the number of times it takes for it to get from a certain point to another, but natural time is relative, thus no clock can measure it with 100% accuracy with respect to any observer in any motion as Albert Einstein's theory of relativity says.
His theory has many practical applications such as in astronomy, trajectory of satellites and etc.

Let's face it: Its impossible for everything to have a definition. Or to put it another way: Its impossible to construct a monolingual English dictionary that contains every root word in the English language, and doesn't contain any circular definitions. This is because any word can only be defined in terms of other words, which in turn must be defined by other words, etc. But eventually, this process must end because there are only a finite number of root words. Ultimately, some words must be assumed as understood, without a definition, so that more complex words can be defined in terms of these "assumed words.

Babies don't read dictionaries, and are taught language because we have evolved to understand each other.

[monkeymeister]

Babies don't read dictionaries, and are taught language because we have evolved to understand each other.

All living things understand eachother to an extent.
We are the only ones that have a complex language.
But with our many languages there comes many problems. Babies dont read dictionaries but they to read their parents emotions and try to imitate them. Because every parent acts differently and use words in slightly different ways and how words are normally just generalizations of a number of thoughts we never can have exact defintions. But i dont see what this has to do with time... this thread is about if/how it exists.

[jinydu]

In that case, I would say that yes, time does exist becomes change exists (as we can observe). I will not try to define time, because I think that it is so fundamental that it cannot be defined in terms of simpler concepts. In any case, I think that everyone has an intuitive notion that time exists, that today is different from yesterday.

Also, monkeymeister, I am currently taking a Linguistics class, and one of the most well-established facts of linguistics is that children (and babies) do not just imitate their parents. They say many things that their parents would never say, such as "They drived to school" and "What do you think what's in there?" Furthermore, these errors are not random mistakes, because there are many possible (and sensible, if babies were really born as blank slates who always searched for the simplest rule) errors that children almost never make, such as "Does he be smiling?", "He didn't a few things." and "He ams going." Furthermore, experiments have demonstrated that babies already have a sense of some rules of grammar (In the example I was given, babies too young to speak at all are placed in front of two screens (one with Big Bird washing Cookie Monster, and the other with Cookie Monster washing Big Bird) while a recording says "Where's Cookie Monster washing Big Bird?" The baby almost always gets the right answer.) This, together with other evidence shows that babies are born with some knowledge of what is a possible language and what isn't (ex. no languages have random word orders or fail to distinguish between nouns and verbs). Of course, they still have to learn the particular facts of their particular language, which takes a several years.

[monkeymeister]

Any biology class would tell you the opposite. We are born with the ability to understand any language but only through learning does it become possible.

Why are the mistakes

children almost never make, such as "Does he be smiling?", "He didn't a few things." and "He ams going."

but they do make mistakes like

"They drived to school" and "What do you think what's in there?"

Babies to young to speak still have listened to other people speak. The only way to show we are born with the basic rules of language is if the experiment was done with babies never exposed to language or if they had to choose between different sentences in a language they are unfamiliar with.

[jinydu]

I didn't say that babies don't have to learn to speak a particular language, only that they are born with some knowledge about language and how to learn it.

For instance, babies at birth wouldn't know any words, but they would know that words combine to form phrases, which in turn form sentences. They would also know that there are different types of words: nouns, verbs, adjectives, etc. Of course, they would still have to learn facts that are specific to their language, such as "Does the object come before or after the verb?" and "Should I use double negatives?"

I think of it as sort of like getting a new computer. When you take it out of its box, it already has many universally desirable things (that is, things that every computer user wants), such as a CPU, a hard disk, an operating system, etc. But there are still many things you have to "teach" the computer so that it is well-suited for you in particular (ex. user accounts, passwords, your favorite programs, etc.)

[monkeymeister]

Exactly.
We were born with the basic template that all useable languages follow but the specific language is learned from our parents or other people surrounding us. And because everyone is surrouned by different people they learn the specifics of the laguage differently. The meaning of words are just specifics of a language and vary from person to person. Its not that a word like time or any other word is undefinable its just that as a society we can never agree upon anything.

[Geosphere]

All living things understand each other to an extent.

I've yet to see plankton communicate with a hedgehog.

[Rkyeun]

Understanding requires sentience, which is as-of-yet an unprovable term.
Thus one cannot state that all things understand one another. It is certainly more plausible to say that all things exchange information, or communicate. The plankton fed some whale that died and was eaten by a fish which was caught by a fishermen and turned into fertilizer to grow weed that fed a grasshopper that the hedgehog ate. The hedgehog doesn't have a clue that there was plankton involved, but sure enough some of the atoms from the plankton are in there. Understanding is not a prerequisite. Similarly, without understanding the computer or the infant can absorb commands and behaviors and spit them out on command. Your computer hasn't the slightest what this forum post is talking about, but it's certainly good at regurgitating the text to you.

You can definitely go forwards in time. Look! You did it! ...Oh, you did it again! Now wiggle your fingers about. They went forwards slightly faster! Going backwards is a bit trickier, since even in the smallest amount you would crush into yourself from the moment before. However there are a few theories that bear mentioning. The first is the large spinning mass method, which does work (kinda) but isn't useful. The second is merely a theory, has the potential to work safely, but is... quirky.

Before I can talk about it, though, you have to know what a light cone is. Starting at any point in time and space, extend a sphere outwards from that point at the speed of light. This is your observable universe, for all of time. At the beginning, only light immediately around the point has reached you. Later the sphere is larger, and even light from far away has had time to reach you.
The alternative to this is that light from far away that has had time to get to you is also visible. So it's not just a cone shape, but an hourglass. The further back the event occured, the farther away from you it can be and still see it. So this particular cone-shaped hypersolid might as well be the entire universe, because it's all you're ever gonna get to know. And I'm gonna try to illustrate it, but the forums might eat my white space.
\/ \/
/\ /\
Except that large spinning masses cause the cones to tilt. The cones will tilt in the direction of the rotation, which pulls things more strongly towards it due to its increased energy.
|/ |/
/| /|
If you get it too far over, the future end of one cone will connect to the past end of the other, just a sliver.
/ /
--/-- go through here --/--
/ /
From there you can go all the way around the spinning mass until you wind up in your own past.

Here's the problem. See that line where past touches future? You just made a black hole. This form of hole is called a ring singularity, because the center isn't dangerous. It's spinning so fast that the insides seperated from centrifugal force, and you now have an event horizon in the shape of a torus. It makes a good trampoline, but the point of past-meets-future is in the unreachable center circumference of the torus that you just phased out of existance. And it eats your large spinning mass, slowing down, and slowly closing back into a sphere.

The second method hasn't really been postulated as to how to generate it, but because location isn't energy content, it doesn't violate any conservation laws to suddenly teleport someplace else through directed quantum tunneling. The only catch is again the light cones. You can't timewarp to any time or space where you could have seen yourself. If you go back in time, you have to go far enough away in space that light from your timetraveled self wouldn't have reached you. So you can't send yourself any timetraveled messages or affect the past. And more disturbingly...
You can't go home again. You'll arrive with no way to aim at your old time and space, until you can observe it and set the coordinates. And by the time you can observe it... it's out of range. You'll vanish, and the world you knew will be forever lost. You can get back without missing a WHOLE lot of time though. You'll need a spaceship that can pull a hefty fraction of C, which will slow you down so you only age a miniscule amount during your trip, and you can land your ship a few minutes after your former self made the timewarp if you leave immediately. Sorry guys, not really counting as time travel. No past-editing allowed.