What is Time

[Particle]

Also another thing is that measurements represent multiple objects relevant to each other. Properties and objects are singular thus more tangable concepts. They are two differnet concepts that get too mixed up all the time.

 

[Parkre]

Particle

your 24 hour per day == 1 cycle.

time
----- == no units
time

and remember time is relative


your time is a measurement of an objects velocity isn't quite correct either. It's more of desciption of the position/velocity/orientation/spin/etc compared to the original position/velocity/orientation/spin/etc. ie "it took six hours for the blossom to bloom from completely closed."


MY QUESTION:

has it been determined whether or not time IS a fourth dimension?? or is still just a relative measurement by which we observe things?

 

[Titan]

Here's another aspect of time i don't believe was mentioned. It breaks down like this.

Space and Time are intertwined.

The Universe is expanding.

Therefore, as the universe expands, time moves in a forward direction. If, in some part of the universe space-time is contracting, time would be moving backwards relative to the expanding time reference.

This has been theorized many times, but a few years ago a physics professor at Clarkson University mathematically proved it.

That makes my head hurt without knowing any of the math.

 

[Parkre]

Titan

but what you are saying is that we wouldn't know if time is travelling backwards because we (humans) can only percieve time as travelling forward, right?

 

[Titan]

Originally posted by: Parkre
Titan

but what you are saying is that we wouldn't know if time is travelling backwards because we (humans) can only percieve time as travelling forward, right?

I honestly don't know, I'd need to look it up again. I do remember the part in the Superman I movie where he can't stop both rockets in time to save Lois Lane and he flies backwards around the earth a gagillion times to go back in time and save her.

In all seriousness, I think if the universe started collapsing, time may reverse. I'm not positive. If you accept that we are part of the entropy, and our space and time are intertwined, our lives may reverse. As to wether or not we would notice, or even survive is a complete mystery. We haven't been around long enough to examine the properties of a collapsing universe.

 

[Woodchuck2000]

Originally posted by: Titan
Here's another aspect of time i don't believe was mentioned. It breaks down like this.

Space and Time are intertwined.

The Universe is expanding.

Therefore, as the universe expands, time moves in a forward direction. If, in some part of the universe space-time is contracting, time would be moving backwards relative to the expanding time reference.

This has been theorized many times, but a few years ago a physics professor at Clarkson University mathematically proved it.

That makes my head hurt without knowing any of the math.

That's simply not true. "Time" moving "Forward" is not a natrual consequence of the expansion of the universe. I've never heard it theorised before, let alone proven. It's simply a logical non-sequitur.

Parkre - asking if time is a fourth dimension is really a redundant question as we have no easy way to define it. It's impossible to linguistically define time as the concept is fairly axiomatic as far as we're concerned. We can define time as a fourth dimension with a great deal of success in most areas of Physics, so to all intents and purposes the answer is yes, we can't prove it though.

 

[Parkre]

Originally posted by: Woodchuck2000

Originally posted by: Titan
Here's another aspect of time i don't believe was mentioned. It breaks down like this.

Space and Time are intertwined.

The Universe is expanding.

Therefore, as the universe expands, time moves in a forward direction. If, in some part of the universe space-time is contracting, time would be moving backwards relative to the expanding time reference.

This has been theorized many times, but a few years ago a physics professor at Clarkson University mathematically proved it.

That makes my head hurt without knowing any of the math.

That's simply not true. "Time" moving "Forward" is not a natrual consequence of the expansion of the universe. I've never heard it theorised before, let alone proven. It's simply a logical non-sequitur.

Parkre - asking if time is a fourth dimension is really a redundant question as we have no easy way to define it. It's impossible to linguistically define time as the concept is fairly axiomatic as far as we're concerned. We can define time as a fourth dimension with a great deal of success in most areas of Physics, so to all intents and purposes the answer is yes, we can't prove it though.

Thanks, that was exactly the the answer I was looking for.

 

[Woodchuck2000]

Originally posted by: DrPizza
Here's a wonderful related question: is time continuous? Or does time move forward in discrete (albeit very small) steps.


edit: note - I'm not even sure if there's an answer for this... I remember the question being postulated before, and a discussion of Planck time, etc. What I'm trying to remember is if
a) there is an answer for this or
b) if it is even possible to know if there is an answer to this

I was under the impression that Planck time is the smallest interval we can use before quantum effects begin to dominate - effectively the time a photon takes to travel a Planck length. Anything below that is meaningless outside of very tricky quantum-mechanical calculations.

I would be tempted to suggest that there's no way to know for certain whether there's an answer because our knowledge is entirely subjective. That starts hitting philosophical constraints though rather than physical ones.

I would be tempted to suggest that actually discretising time would lead to some very funny results in certain parts of physics - while time may be practically discrete if you make the denominator small enough, I personally doubt that it is actually discrete.

 

[Titan]

Originally posted by: Woodchuck2000
That's simply not true. "Time" moving "Forward" is not a natrual consequence of the expansion of the universe. I've never heard it theorised before, let alone proven. It's simply a logical non-sequitur.

You sound very certain unless I am mistaken, can you provide solid proof that this is an impossible idea?

I managed to remember the name of the provessor, search for "LS Schulman" who has done much research on "Time Arrows" the relation of thermodynamics, electromagnetism, and time.

I found a link to the abstract of the article I recalled from 1999, but you need to sign up to see the whole article.

http://prola.aps.org/abstract/PRL/v83/i26/p5419_1

A model in which two weakly coupled systems maintain opposite running thermodynamic arrows of time is exhibited. Each experiences its own retarded electromagnetic interaction and can be seen by the other. The possibility of opposite-arrow systems at stellar distances is explored and a relation to dark matter suggested.

 

[Particle]

Originally posted by: Parkre
Particle

your 24 hour per day == 1 cycle.

time
----- == no units
time

and remember time is relative


your time is a measurement of an objects velocity isn't quite correct either. It's more of desciption of the position/velocity/orientation/spin/etc compared to the original position/velocity/orientation/spin/etc. ie "it took six hours for the blossom to bloom from completely closed."

C'mon your not going to get all ultra technical on me now, are you I am definitely in need of a refresher. I am looking at things way too 2 dimensional lately. I have been doing computer science for a long time and just jumped into Physics recently.

 

[Future Shock]

Originally posted by: mjia
No one really nows how many dimensions exist. String theory proposes 11 dimensions, but can't be proven.

You can't classify 'things' as having different dimensions. If you accept theories like general relativity or string theory, then it mean that all matter at the subatomic level, exist in multiple dimensions.

11 dimensions? According to the Superstring Website, there are either 10, or 26...depending upon your choice of superstring theory.

Future Shock

 

[mjia]

There was actually a second version of string theory proposed in the mid 1990 that supports an 11-dimensional universe. As far as I know, this is still the lastest model.

 

[Titan]

found some more stuff about time arrows if you want to make your head hurt.

http://en.wikipedia.org/wiki/Arrow_of_time

 

[Parkre]

Originally posted by: Titan
found some more stuff about time arrows if you want to make your head hurt.

http://en.wikipedia.org/wiki/Arrow_of_time

I love to make my head hurt!!