Re the "realness" of time,

I used to think of 4D spacetime as an artificial construct that made some kind of math easier to process. Then I read the following article that explains why the speed of light can't be exceeded:

http://www.reddit.com/r/askscience/comments/fjwkh/why_exactly_can_nothing_go_faster_than_the_speed/c1gh4x7

When you look at it that way, time is a very real dimension and in a sense, when at rest, we travel through time at the speed of light. If that sounds weird, you didn't read the article.

It's one of the best things I've ever found on the internet.

Re the "realness" of time,

I used to think of 4D spacetime as an artificial construct that made some kind of math easier to process. Then I read the following article that explains why the speed of light can't be exceeded:

http://www.reddit.com/r/askscience/comments/fjwkh/why_exactly_can_nothing_go_faster_than_the_speed/c1gh4x7

When you look at it that way, time is a very real dimension and in a sense, when at rest, we travel through it at the speed of light. If that sounds weird, you didn't read the article.

It's one of the best things I've ever found on the internet.

Ah, but what would time be then? Still a matter of man's perception. It doesn't sound weird to me at all, but knowing the fact that if a human were to travel close to the speed of light compared to a man in "normal" time, their perceptions of the passage of time would be based upon their perception. For example, the person traveling near the speed of light would see time pass by "normally" whereas thousands or even millions of years could go by to the man in "normal" time in the same perception.

How do we reconcile the differences in perception if time is a real dimension? It's not like an inch in the second dimension is different to observers in the third dimension. So how can time be different in the fourth dimension to observers in the third?

Time only makes sense as a logical construct to support the idea of the higher dimensions above it because each layer must fold through the layer above to reach a point of infinity, but we have thus far not made any observation that makes this true. It's a construct that attempts to help "pretty" our view of the Universe and the reality around us so that it all makes sense.

[Edit] Speaking of fun stuff on the internet, I've really enjoyed these videos, even though they support your idea of time being a real dimension:

https://www.youtube.com/watch?v=JkxieS-6WuA - Imagining the Tenth Dimension part 1
https://www.youtube.com/watch?v=JkxieS-6WuA - Imagingin the Tenth Dimension part 2

[Edit 2] It is important to note, however, that this is considered fringe science and not mainstream. Even the article you linked to used far too much oversimplification to convey a complex concept to a layman. I don't think this person's teachings will be making it into the next physics class to unify general relativity and quantum physics into one pretty little theory anytime soon.

Re the "realness" of time,

I used to think of 4D spacetime as an artificial construct that made some kind of math easier to process. Then I read the following article that explains why the speed of light can't be exceeded:

http://www.reddit.com/r/askscience/comments/fjwkh/why_exactly_can_nothing_go_faster_than_the_speed/c1gh4x7

When you look at it that way, time is a very real dimension and in a sense, when at rest, we travel through time at the speed of light. If that sounds weird, you didn't read the article.

It's one of the best things I've ever found on the internet.

I prefer to think of the universe in terms of points of quantum information.
Planck units derived from 5 universal physical constants.
The maximal transfer of quantum states between orthogonal points of adjacent Planck volumes occurs within a Planck unit of time.
By derivation this maximal transfer is equal to the speed of light in 4D.
M theory posits 11 dimensions, hinting at greater complexity.
A higher dimensional translation of 4D quantum state information might well be possible resulting in instantaneous travel to anywhere&anytime in the universe.
Wormholes R Us.

More sci-fi Gooba Gabba.

Dr. Eric Korpela is an astronomer, which implies he might have some background in physics. It would be interesting to hear his well-educated view on this topic.

If only there was a way to get him to post here!

If only there was a way to get him to post here!

A wise person leaves the speculation to the amateurs.

Ah, but what would time be then? Still a matter of man's perception. It doesn't sound weird to me at all, but knowing the fact that if a human were to travel close to the speed of light compared to a man in "normal" time, their perceptions of the passage of time would be based upon their perception. For example, the person traveling near the speed of light would see time pass by "normally" whereas thousands or even millions of years could go by to the man in "normal" time in the same perception.

*Both* of your observers would see the other's time ticking slower. There is no "normal" time, there is the clock speed of observer A and the clock speed of observer B, they are different and depend on which frame of reference you choose, A or B. It's relative as in relativity.

I know what you are thinking, you are thinking "huh?" How can both clocks be slower than the other? Doesn't that mean they would both be older than the other, a paradox?

The paradox is resolved by general relativity, because when one of them *turns around* and travels back to the other, the mere act of turning around imposes an asymmetry that causes one to be older than the other when they come back together. So at least it's not physically impossible even if weird.

Ah, but what would time be then? Still a matter of man's perception. It doesn't sound weird to me at all, but knowing the fact that if a human were to travel close to the speed of light compared to a man in "normal" time, their perceptions of the passage of time would be based upon their perception. For example, the person traveling near the speed of light would see time pass by "normally" whereas thousands or even millions of years could go by to the man in "normal" time in the same perception.

*Both* of your observers would see the other's time ticking slower. There is no "normal" time, there is the clock speed of observer A and the clock speed of observer B, they are different and depend on which frame of reference you choose, A or B. It's relative as in relativity.

Both clocks cannot tick slower. I agree that it is all relative to your frame or reference, but for Observer A time would appear the same and Observer B would appear to be moving so slow as if motion weren't happening. To Observer B time would appear the same and Observer A would be moving so fast that his physical shape would nearly elongate itself in a blurred stretch (much as we view a beam of light from our relative view of time). To each Observer time would appear to remain in the same constant, linear direction as when they started. This explains why Observer A seems to remain the same age and Observer B has aged many years (if they continue to exist at all).

I'm sure we both recognize the effect I'm describing is time dilation as stated in the theory of special relativity.

I know what you are thinking, you are thinking "huh?" How can both clocks be slower than the other? Doesn't that mean they would both be older than the other, a paradox?

The paradox is resolved by general relativity, because when one of them *turns around* and travels back to the other, the mere act of turning around imposes an asymmetry that causes one to be older than the other when they come back together. So at least it's not physically impossible even if weird.

Observer A returning to Observer B after having traveled close to the speed of light, as you correctly state, would have aged differently, suggesting time does not move at a linear rate for both observers. This lack of a constant rate implies a measurement that sort of "bends" in meaning based upon the observer, which is true regardless if Observer A turns around or not.

This begs the further question of: if time were a real dimension, how does one travel in the opposite direction? You can't simply move near the speed of light in reverse as you're simply heading, for example, South while facing North. In every other dimension we know of, travel is possible in both directions. Why is it suggested that one can only move forward in the fourth dimension? I suppose you could theorize a sort of "negative light" that allows you to travel into the past, but now we're really getting into the sci-fi.

Both clocks cannot tick slower. I agree that it is all relative to your frame or reference, but for Observer A time would move faster and Observer B time would move slower. This explains why Observer A seems to remain the same age and Observer B has aged many years (if they continue to exist at all).

I'm afraid that's not exactly right. For both observers, the time perceived in their inertial frame ticks normally. The clocks they see through telescopes in the other's *different* inertial frame tick slower. Both can indeed be slower, that is the crux of the Twin Paradox.

Both clocks cannot tick slower. I agree that it is all relative to your frame or reference, but for Observer A time would move faster and Observer B time would move slower. This explains why Observer A seems to remain the same age and Observer B has aged many years (if they continue to exist at all).

I'm afraid that's not exactly right. For both observers, the time perceived in their inertial frame ticks normally. The clocks they see through telescopes in the other's *different* inertial frame tick slower. Both can indeed be slower, that is the crux of the Twin Paradox.

Hmmm... that link seems to suggest (not to be offensive) that your application of time dilation is the naive one:

This result appears puzzling because each twin sees the other twin as traveling, and so, according to a naive application of time dilation, each should paradoxically find the other to have aged more slowly.

When in reality (using the example given in the thought experiment), the Space Twin hasn't aged while the Earth Twin is much older. This seems to confirm my application of time dilation in that for Observer A time, while appearing to move at a "normal" rate from his frame of reference, is actually moving much faster than Observer B, who would appear to be frozen.

Likewise for Observer B time would appear to be moving at a linear ("normal") rate while his frame of reference would see Observer A moving so fast as to become a blur effect.

If the clocks ticked slower for both Observers, they both would appear to age more slowly as suggested in the naive application of time dilation.



[Edit] Ah, I see the paradox you mention now later in the article. I'm confused why it explains that the Earth Twin gets a slowed signal at 1/3 the speed of the transmitter. What would the observation be if the transmitter sent an image at the full speed of the transmitter? Wouldn't it be sort of a blurred image?

At any rate, none of this seems to explain to me how time actually exists. We know that interesting effects can happen when you approach the speed of light, but it is all still based on relative observation, meaning that time doesn't appear to have any consistent linear constant. It simply means that an arbitrary unit of measurement is different for all observers given different velocities. Nor does it answer my question above about going backward in time (to the past) if time were a physical dimension.

I was just talking about the situation where two observers are in non-accelerated motion relative to each other, in that case each sees the other's clock as moving slower.

When one of them undergoes acceleration, their frame becomes non-inertial and the symmetry is broken.

I think the point is that there is no such thing as normal or universal time because there is no absolute frame of reference that is "at rest" with respect to everything else. It is always relative.

Two observers in relative motion with each other (each could think of themselves as being the one who is at rest, with equal validity) do not even agree with what "now" means. See "Relativity of Simultaneity."

The lack of absolute frame of reference might be a leading factor in the prevailing thought that time is sort of a quasi-dimension and not really a complete physical dimension in our traditional understanding of the term.

But thanks for the Twin Paradox thought experiment. I really enjoyed learning new things.

as time ceases to exist, at the event horizon.

Thought of that a lot. How can time cease to exist? Practically whole the functionality of the Universe is based on time. Time is one of the pillars of existence. If time ceases to exist then all would be, how would I call it, static? (but you'd still exist)

Actually, time, also known as the fourth dimension, is a man made construct that we can't prove exists, probably by the very nature of our existence. We only seem tangentially aware of time because we have the ability to retain a memory of the past, so we assume a future exists as well.

This is why, at least in physics classes that teach M-theory or string theory, anything above the third dimension is unproven and not confirmed to exist. We theoretically know of 10 possible dimensions with time only be considered a quasi-dimension.

But when you look at your clock, it tells time. That's reality. You can see the clock ticking, 'time' evolves

[edit]very sceptical about that string theory though...

Who made that clock? Was it man made or found in nature? What is 1 second based upon that has something comparable found in nature other than a random, arbitrary measurement made by man?

Everything we know is made by us, or is at least created in our mind

Does that include the planets and the stars? Other life forms?

Of course not but I'm talking about our perception. Everything, as we know it, is a product of our perception, creations of our mind...

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rOZZ
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A wise person leaves the speculation to the amateurs

Agreed

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rOZZ
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Does that include the planets and the stars? Other life forms?

Of course not but I'm talking about our perception. Everything, as we know it, is a product of our perception, creations of our mind...

Not all things exist purely because of our perception. Otherwise that would imply that if we didn't exist, the Universe wouldn't exist, which is not strictly true (but it does fall into the "If a tree falls in the forest and no one is there to hear it, does it make a sound?" - physics say yes it does).

There is a physical, materialistic reality that we are slowly discovering around us. Time may or may not be one of those things. While it seems to be true that time "allows" things to happen from a point to another point (e.g. present to future, past to present, or past to future), it would seem that time only has a singular direction that we can directly perceive and experience. So far, the other three dimensions allow us to travel in all directions, so that begs the question: is time a real dimension? Or is it something else?

Some discussions about Black Holes with the Astronomer Royal, Martin John Rees, Baron Rees of Ludlow, OM Kt FRS, to give him his full title. If you can access them, that might not be possible outside the UK. These clips are extra's to this months edition of the Sky at Night, so are up to date.

Sky at Night - Clips

That was a really good interview. Shame the main program is nowhere near long enough to include such 'outtakes'. That blew my lunchbreak!

Well worth going through all the clips. Very well presented and explained in a very easy going yet still very accurate way. Excellent.

They're there for just 6 days and counting...


Keep searchin',
Martin

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... So far, the other three dimensions allow us to travel in all directions, so that begs the question: is time a real dimension? Or is it something else?

Is "time" perhaps not 'directly real' but instead a second or third order effect?

In an analogous way to how we have magnetism for a constant flow of electrical charge, and electromagnetic radiation for an accelerated electric charge?...


The one-way "arrow of time" is quite an asymmetric conundrum!

Keep searchin',
Martin

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See new freedom: Mageia Linux
Take a look for yourself: Linux Format
The Future is what We all make IT (GPLv3)

So what is the definition or meaning of a dimension then?

In our world there is supposed to be three dimensions. Where is it stated that time is the fourth dimension? Do we perhaps know of even more dimensions, like 11?

Certainly, gravity bends light which is supposed to be particles (photons). In the same way, gravity also is able to bend (or warp) time.

Also let us not forget that black holes are still exotic objects in space. You are more likely to end up on the surface of a white dwarf or a neutron star.

is time a real dimension? Or is it something else?

Found an interesting article on that matter:

http://www.dailygalaxy.com/my_weblog/2011/04/spacetime-has-no-time-dimension-new-theory-claims-that-time-is-not-the-4th-dimension.html

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rOZZ
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Re the "realness" of time,

I used to think of 4D spacetime as an artificial construct that made some kind of math easier to process. Then I read the following article that explains why the speed of light can't be exceeded:

http://www.reddit.com/r/askscience/comments/fjwkh/why_exactly_can_nothing_go_faster_than_the_speed/c1gh4x7

When you look at it that way, time is a very real dimension and in a sense...

That gives rather a good explanation. Still best to read the entire article but the crucial bit to run along with is:

When you sit there at apparent rest, you're really careening toward the future at top speed. But when you get up to put the kettle on, you change your direction of motion through spacetime, but not your speed of motion through spacetime. So as you move through space a bit more quickly, you find yourself moving through time a bit more slowly.

... you have to give up some of your motion toward the future, since the four-velocity arrow can only rotate and never stretch or shrink.

This is the origin of the famous "time dilation" effect everybody talks about when they discuss special relativity. If you're moving through space, then you're not moving through time as fast as you would be if you were sitting still. Your clock will tick slower than the clock of a person who isn't moving.

It's one of the best things I've ever found on the internet.

That is certainly one of the better and more direct descriptions.


Good find thanks!

Keep searchin',
Martin

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See new freedom: Mageia Linux
Take a look for yourself: Linux Format
The Future is what We all make IT (GPLv3)

This is the origin of the famous "time dilation" effect everybody talks about when they discuss special relativity. If you're moving through space, then you're not moving through time as fast as you would be if you were sitting still. Your clock will tick slower than the clock of a person who isn't moving.

And this has been proved with atomic clocks has it? I think it has but not sure.

The Hafele and Keating Experiment.

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