Time Travel is Science Fiction

[Farsight]

I'm confident that, as Nimbus states, Koks is talking about the coordinate speed of light. Are you?

Yes. And get this: it is the speed of light. The speed of light at the ceiling is greater than the speed of light at the floor. If it wasn't, light wouldn't curve and your pencil wouldn't fall down. Have a read of what Irwin Shapiro said: "The proposed experiment was designed to verify the prediction that the speed of propagation of a light ray decreases as it passes through a region of decreasing gravitational potential". Have a read of Ned Wright’s Deflection and Delay of Light and clock this: "In a very real sense, the delay experienced by light passing a massive object is responsible for the deflection of the light”. Light doesn’t curve because spacetime is curved. Einstein never said that. It curves because the speed of light varies with position. Like a car veers when it encounters mud at the side of the road.

The issue isn't with the material you quote, but rather, your interpretation of it.

No it isn't. The issue is with what you've been taught. It's wrong. The locally-measured speed of light is constant because of a tautology*, wherein we use the local motion of light to define the second and the metre, which we then use to measure the local speed of light. Climb up to the ceiling and measure the speed of light, and you deem it to be 299,792,458 m/s. Do the same at the floor and again you deem it to be 299,792,458 m/s. But the seconds aren't the same, so the speeds aren't the same. And there is no time flowing though your optical clock, just light, moving. So when your clock goes slower it's because the light goes slower.

* See http://arxiv.org/abs/0705.4507 and note this: "The unit of time is defined by an oscillating system or the frequency of an atomic transition, and the unit of space is defined in terms of the distance travelled by light in the unit of time. We therefore have a situation akin to saying that the speed of light is “one light-year per year”, i.e. its constancy has become a tautology or a definition".

 

[Farsight]

The problem here is that when they were first introduced, there were no optical clocks. They (your parallel mirror light clocks) were and are not idealized optical clocks. One is an imaginary tool, used in hypotheticals, the other is real. One (the parall mirror light clock) does at least suggest that the speed of light is involved, the other involves the mechanics of an atom, as it affects the emission of photons... Not the speed of light. The NIST optical clocks do not measure the speed of light or depend on any change in c.

Yes they do. They work much the same as the Caesium clock used to define the second as 9192631770 periods of radiation. There isn't any time flowing through them. Instead it's light, moving. And electrons, but they're electromagnetic too. So it all comes down to the rate of electromagnetic propagation. Not the rate at which "time passes".

This is a complete misrepresentation of the facts. BTW did that particular reference provide any control, proving that those two optical clocks would function identically when side by side, rather than when located in different labs? And if so why does it take more than one atomic clock to come up with our standard of time?

It's no misrepresentation. One optical clock runs measurably slower than the other when it's only 30cm lower. And I don't care about clocks side-by-side. This is general relativity we're talking about. We all know that clocks run slower when they're lower. Only some of us don't know why.

Seems I have seen some NIST reference that demonstrates that even two otherwise identical optical clocks in the same room vary in their clock rate!

And again: an optical clock goes slower when its lower. Not because some magic invisible time flows slower, but because light moves slower. And what part of a curvature of rays of light can only occur when the speed of light varies with position don't you understand?

 

[Farsight]

Even your NIST optical clocks, clock rate can be affected by more than just location in a gravity well. Did your reference include controls for temperature differences or...

Stop clutching at straws. This is general relativity we're talking about. Clocks go slower when they're lower.

I accept the NIST clock reference as supporting the GR prediction that the two clocks would function differently at different locations in the earth's gravity well. What it does not prove is that the speed of light is anything other than c.

See above. I've given you the references and the quotes, and surely I've explained that there's no time flowing through those clocks, and that clocks clock up some kind of regular cyclical motion. How much more do you need? Or would you rather dismiss Einstein and the rest because you'd rather believe in time travel?

You make claims of fact about conditions that are not only beyond your ability to measure but are beyond mankind's current ability to measure and confirm.

I'm not doing this at all. We can measure time dilation. We can open up a clock and see that there's no time passing through it. We know that the second is the duration of 9192631770 periods of radiation. And we know what Einstien and Shapiro and Ned Wright and Don Koks said, don't we?

That is my biggest concern with your posts. Is the speed of light the same everywhere in the universe? I don't know.

Well I do, and the answer is no. It isn't even the same in the room you're in. If it was, your pencil wouldn't fall down.

All we can do is base what we believe on what we do know, which is that when we measure the speed of light we always get the same answer...

Duh! Because we use the local motion of light to define the second and the metre. Then we use them to measure the local speed of light. So of course we always get the same answer. This is why Magueijo and Moffat talked about a tautology.

And when we use that value as a constant, to interpret what we observe of the distant universe, the conclusions we reach seem to make sense, so until proven otherwise it works for me.

No it doesn't work for you. Because you do not really understand something until you can explain it to your Grandmother. And you can't explain how gravity works. But I can.

 

[billvon]

Yes they do. They work much the same as the Caesium clock used to define the second as 9192631770 periods of radiation. There isn't any time flowing through them. Instead it's light, moving.

No, there is no light moving. Cesium clocks do not measure the speed of light - they measure the frequency of the radiation produced by the transition transition between two ground states of cesium. (And, BTW, that frequency is not a light frequency.) Likewise, quartz oscillators, which show exactly the same time contraction as any other clock, use mechanical oscillation of an electrically excited crystal. All clocks are affected the same way, whether they use atomic, mechanical or light-based standards. Hence there is no interference with the mechanism by velocity, but a fundamental change in how rapidly time passes in that frame relative to another frame.

 

[paddoboy]

But woo, clocks are supposed to be measuring the flow of time? Only there ain't no time flowing through 'em? Read the OP, MotorDaddy. A clock is not some cosmic gas meter. But time travel is science fiction. And if there's anything you aren't clear on, ask me about it, and I'll clear it up.

Quite a childish inane analogy. You do not have the intestinal fortitude to admit to any of your false claims. Your house of cards that you have built would all come tumbling down if just one card was removed.
This is the way it is Farsight...Take note:
A clock has nothing to do with time, it just measures it's progress.
Time cannot be seen directly, felt directly or smelt at all. But most level headed people agree that it exists, and that is supported by expert professionals such as Hawking, Thorne, Sagan, Smolin, and Carroll. All are many rungs up the ladder of knoweldge, from you.
Time travel is in no way forbidden by the laws of physics and GR.
That is an undeniable fact.
Any sufficiently advanced civilisation, could achieve it....
Another undeniable fact.

I realise there are many things you are not clear on, and I also know there are many things you do not want to be clear on. That house of cards, together with your grossly over-inflated ego attests to that fact.

 

[paddoboy]

Well I do, and the answer is no. It isn't even the same in the room you're in. If it was, your pencil wouldn't fall down.

Well you dont...and the answer is that the speed of light is constant at "c"
So much for your silly "pencil"red herring.

No it doesn't work for you. Because you do not really understand something until you can explain it to your Grandmother. And you can't explain how gravity works. But I can.

I'm not sure if we have any Grandmothers on this forum, but I do know they would probably be laughing at your claims re time, time travel, and the constancy of the speed of light.
Yes, you are delusional.

 

[Farsight]

No, there is no light moving.

Yes there is. There's microwaves moving. That's light. See NIST:

Cesium clocks do not measure the speed of light

Yes, we know that.

they measure the frequency of the radiation produced by the transition transition between two ground states of cesium.

Not when they're defining the second they don't. Because to measure a frequency you need to have already defined the second.

(And, BTW, that frequency is not a light frequency.) Likewise, quartz oscillators, which show exactly the same time contraction as any other clock, use mechanical oscillation of an electrically excited crystal.

It's called the piezoelectric effect. The electric is as in electromagnetic.

All clocks are affected the same way, whether they use atomic, mechanical or light-based standards. Hence there is no interference with the mechanism by velocity, but a fundamental change in how rapidly time passes in that frame relative to another frame.

Whoosh! See that time passing inside that clock!

 

[billvon]

Yes there is. There's microwaves moving. That's light.

No, light isn't microwaves. It is light. It is defined as either visible light (400-800nm) or if you include UV and IR, 10nm to 1 000 000 nm. Microwaves are, by definition, longer wavelengths.

It's called the piezoelectric effect. The electric is as in electromagnetic.

It is mechanical; the frequency is set by the mechanical resonance of the structure. Spring clocks are similar. Their time is set by resonance of the mechanical systems within the timepiece.

Whoosh! See that time passing inside that clock!

Given that you did not understand how either atomic or quartz clocks work, you can perhaps be forgiven for having such a fundamental misunderstanding of how time passes differently in different reference frames.

 

[QuarkHead]

Because to measure a frequency you need to have already defined the second.

Why can't I measure the frequency of visible light by noting its colour? Why do I need time?

 

[OnlyMe]

Given that you did not understand how either atomic or quartz clocks work, you can perhaps be forgiven for having such a fundamental misunderstanding of how time passes differently in different reference frames.

Only should there be the possibility that his interpretation and understanding improve.....

 

[OnlyMe]

Farsight, both the second and the meter were defined before any standard involving light and distance or the ground state frequency of an atom, were adopted, as more accurate rulers.

This is an old argument. You have learned nothing since the last time....

 

[Farsight]

No, light isn't microwaves.

billvon: when we talk about light in physics, we don't just mean visible light.

the frequency is set by the mechanical resonance of the structure

which is set by the electromagnetic bonds in the crystal.

Given that you did not understand how either atomic or quartz clocks work, you can perhaps be forgiven for having such a fundamental misunderstanding of how time passes differently in different reference frames.

I understand them. And you should understand that a reference frame is an abstract thing, as is the passage of time.

Why can't I measure the frequency of visible light by noting its colour? Why do I need time?

Because frequency is defined as cycles per second. You can say the light is green, which is fair enough. But frequency is the reciprocal of time, so as soon as you say measure the frequency you've introduced time via the back door. By the by, there's a wrinkle with all this: when a photon descends, people say it's blueshifted. But you know full well that if you send a 511keV photon into a black hole, the black hole mass increases by 511keV/c². And since you know about conservation of energy and E=hf, you know that actually, the photon frequency didn't increase at all. It appears to be blueshifted when it's lower because you and your clocks go slower when you're lower. But it didn't change, you did.

 

[Farsight]

Farsight, both the second and the meter were defined before any standard involving light and distance or the ground state frequency of an atom, were adopted, as more accurate rulers. This is an old argument. You have learned nothing since the last time....

We've been through all that. Pay attention. The modern definitions are correct because they fit with relativity, because light and matter are "made of the same essence". See the Wiki article on gravitational time dilation for that.

 

[billvon]

billvon: when we talk about light in physics, we don't just mean visible light.

Right. You might mean UV and IR light as well. Which still isn't the same as microwaves. They are two different bands of the EM spectrum.

In physics, words mean things. You can't change them just to win an argument about your pet theory.

which is set by the electromagnetic bonds in the crystal.

Right - just as the frequency of a spring clock is set by the mechanical properties of the spring/balance, which in turn is mediated by the molecular structure of the spring. The resonance, in both cases, is mechanical.

I understand them.

Clearly, as shown by your mis-statements above, you did not. The question is - can you learn from your mistakes?

 

[Farsight]

I'm not making them billvon,. You are.

Now do excuse me, I'm off to bed.

 

[billvon]

I'm not making them billvon,. You are.

You incorrectly thought that atomic clocks used time-of-flight measurements rather than frequency measurements; you posted a picture to that effect and referred to them as "optical clocks."

You incorrectly thought that cesium atomic clocks used light frequencies instead of microwave frequencies.

You incorrectly thought that quartz resonators were based on electromagnetic resonance rather than mechanical resonance.

Now, everyone makes mistakes. The true measure of someone's intelligence is how they learn from their mistakes. Wise men learn from them and become wiser; fools deny that they make them and remain fools.

 

[paddoboy]

Now, everyone makes mistakes. The true measure of someone's intelligence is how they learn from their mistakes. Wise men learn from them and become wiser; fools deny that they make them and remain fools.

And we have had some doozies here of late...Farsight, constant-theorist and chinglu immediatley come to mind.

 

[OnlyMe]

billvon: when we talk about light in physics, we don't just mean visible light.

I'll go with billvon on this, but I would still like to know who the we in you statement is.

Every source I remember, or find in a Google search, refers to a range including IR, visible light and UV as light, then reverts to labeling x-rays, gamma rays and both radio and microwaves as EM radiation. I have always understood the word light as referring to a specific subset of the EM spectrum.

Pay attention!

 

[paddoboy]

Every source I remember, or find in a Google search, refers to a range including IR, visible light and UV as light, then reverts to labeling x-rays, gamma rays and both radio and microwaves as EM radiation. I have always understood the word light as referring to a specific subset of the EM spectrum.

Pay attention!

Ditto.

 

[Farsight]

I'll go with billvon on this, but I would still like to know who the we in you statement is.

People who have heard of things like the speed of light. Like, radio waves don't move "at the speed of EM radiation". Nobody says that. They say they move at the speed of light. Ditto for gamma waves.

Every source I remember, or find in a Google search, refers to a range including IR, visible light and UV as light, then reverts to labeling x-rays, gamma rays and both radio and microwaves as EM radiation. I have always understood the word light as referring to a specific subset of the EM spectrum. Pay attention!

The "visible" light is the giveaway.

You incorrectly thought that atomic clocks used time-of-flight measurements rather than frequency measurements; you posted a picture to that effect and referred to them as "optical clocks."

No, I correctly said you cannot refer to frequency when you're defining the second using the NIST caesium clock, because you count 9192631770 periods of the radiation to define the second, whereafter the frequency is 9192631770 Hz by definition.

You incorrectly thought that cesium atomic clocks used light frequencies instead of microwave frequencies.

No I didn't, because I've always said microwaves are light in the wider sense, which is why we talk about the speed of light, not the speed of microwaves.

You incorrectly thought that quartz resonators were based on electromagnetic resonance rather than mechanical resonance.

No I didn't, because the mechanical properties of the crystal are dictated by electromagnetic bonds.

Now, everyone makes mistakes. The true measure of someone's intelligence is how they learn from their mistakes. Wise men learn from them and become wiser; fools deny that they make them and remain fools.

Yep. And since you won't learn, and since you're being insincere, and you're trying to distract from the topic with false accusations, you're on ignore too.