Light Speed: Fixed... or Relative? Exploring Einstein's Relativity

pheonix358
I have noticed that some questions are being avoided and the fundamental question is not answered.

So, taking two observer positions each on a photon of light traveling toward each other.

Are they not seeing the other photon traveling at twice the speed of light.

Theoretically there may be some small probability of photon-photon interaction, but the probability is so low that no such phenomenon has ever been observed. So we have no experimental verification that a photon can interact with, much less "observe" another photon.

So to make the question more practical, you can ask what an observer traveling at 99.99999% the speed of light would observe of a photon traveling toward him in the opposite direction. It is not 1.999999 times the speed of light, it is 1.0 times the speed of light.

This actually already has been explained to the OP's satisfaction, and is a result of space-time distortion due to relativistic effects. The photon is "blue-shifted" if it's traveling toward you. Since most photons in the universe come from sources traveling away from us, that's why they're all red-shifted, and many of them suggest the objects (galaxies) would now have a recessional velocity away from us greater than the speed of light.

I remember in high school going over the math of why the sound barrier could never be broken. Our science teacher was demonstrating how science can be manipulated.

There were a great many eminent scientists who held this view and yet, now, we know that the sound barrier is not a barrier.
P

Well, yes and no. Actually there IS a sound barrier which caused old propeller planes to have great problems with efficiency if they attempted to cross it. I never saw any such math claiming the sound barrier was unbreakable so you'd have to post a source for that for me to address it. maybe there was math showing that WWII era planes couldn't cross it, and generally they couldn't (unless maybe in a steep dive?), which would make that math more or less correct. And certainly people had to know that bullets broke the sound barrier, right?

Sound Barrier

The sound barrier, in aerodynamics, is the point at which an object moves from transonic to supersonic speed. The term, which occasionally has other meanings, came into use during World War II, when a number of aircraft started to encounter the effects of compressibility, a collection of several unrelated aerodynamic effects that "struck" their aircraft like an impediment to further acceleration.

So, the sound barrier is not entirely "fictional", it actually did impede further acceleration of planes not designed to cross it (swept wings in supersonic aircraft became part of the solution to this problem). As for the light barrier if I can call it that, a physicist has proposed a means to break it, called the Alcubierre drive. Unfortunately, nobody knows how to make one.

Arbitrageur

pheonix358
I have noticed that some questions are being avoided and the fundamental question is not answered.

So, taking two observer positions each on a photon of light traveling toward each other.

Are they not seeing the other photon traveling at twice the speed of light.

Theoretically there may be some small probability of photon-photon interaction, but the probability is so low that no such phenomenon has ever been observed. So we have no experimental verification that a photon can interact with, much less "observe" another photon.

So to make the question more practical, you can ask what an observer traveling at 99.99999% the speed of light would observe of a photon traveling toward him in the opposite direction. It is not 1.999999 times the speed of light, it is 1.0 times the speed of light.

This actually already has been explained to the OP's satisfaction, and is a result of space-time distortion due to relativistic effects. The photon is "blue-shifted" if it's traveling toward you. Since most photons in the universe come from sources traveling away from us, that's why they're all red-shifted, and many of them suggest the objects (galaxies) would now have a recessional velocity away from us greater than the speed of light.

I remember in high school going over the math of why the sound barrier could never be broken. Our science teacher was demonstrating how science can be manipulated.

There were a great many eminent scientists who held this view and yet, now, we know that the sound barrier is not a barrier.
P

Well, yes and no. Actually there IS a sound barrier which caused old propeller planes to have great problems with efficiency if they attempted to cross it. I never saw any such math claiming the sound barrier was unbreakable so you'd have to post a source for that for me to address it. maybe there was math showing that WWII era planes couldn't cross it, and generally they couldn't (unless maybe in a steep dive?), which would make that math more or less correct. And certainly people had to know that bullets broke the sound barrier, right?

Sound Barrier

The sound barrier, in aerodynamics, is the point at which an object moves from transonic to supersonic speed. The term, which occasionally has other meanings, came into use during World War II, when a number of aircraft started to encounter the effects of compressibility, a collection of several unrelated aerodynamic effects that "struck" their aircraft like an impediment to further acceleration.

So, the sound barrier is not entirely "fictional", it actually did impede further acceleration of planes not designed to cross it (swept wings in supersonic aircraft became part of the solution to this problem). As for the light barrier if I can call it that, a physicist has proposed a means to break it, called the Alcubierre drive. Unfortunately, nobody knows how to make one.

edit on 6-2-2014 by Arbitrageur because: clarification

Well you're not entirely correct there is on going research into warping space and well theres been some positive results. So though we dont know how to make one yet were getting closer and have seen some positive results. Though mind you still only minor fluctuations.

www.astrowatch.net...

Here is some of his research as well

www.ntrs.nasa.gov...

reply to post by dragonridr

I'm familiar with that, but I don't see much progress. The catch is this:

Dr White told the conference: “What is necessary to make the trick work is the presence of the ring around the space craft. It would have exotic matter or negative vacuum energy.

Exotic matter meaning you keep reducing the mass until it's below zero. As I said, nobody knows how to do that.

White cites negative vacuum energy observations have already been made (what we call dark energy) so there may be some future hope of a solution, and maybe he's right, but I don't see how that makes us any closer to developing a practical drive at this time, since we still don't even understand dark energy. I am glad to see a man of White's intelligence looking into it though.

dragonridr
reply to post by KrzYma

 

...And he lies to you right at the beginning Einstein tells you an object in motion is different than an object at rest....

well, you say what Einstein said is true and this guy is lying, this is reversible, depends what one believes.
Is relativity your believed truth ?

what about the second video I've posted, about the black holes ? are those arguments not enough ?

BTW, I was recently watching this video


I must say I love Dr. Susskind's lectures, I really do, as long as he says on Earth...
Now listen what he is saying about mark 22 min
he is theorizing about an experiment that starts with a tiny black hole... here comes the problem
black hole is, to they theory, is a very massive point. How the hell, sorry but, HOW THE HELL there can be a black hole in proton size ?? mathematically sure, but I say the equation is false.

this is not enough...
then... he is increasing the black hole by throwing photons at it so the black hole's entropy increases
so now you don't even need mass to make the black hole grow ??

I see you will argue with e=mc2
how about throwing photons on an photos, so much that you get a black hole...


ah, madness
This is all quark, blah blah listen to me and believe what I'm saying as you have no clue what I'm talking about, but I'm PhD so I am right !

bleh

Arbitrageur
reply to post by dragonridr

 

I'm familiar with that, but I don't see much progress. The catch is this:

Dr White told the conference: “What is necessary to make the trick work is the presence of the ring around the space craft. It would have exotic matter or negative vacuum energy.

Exotic matter meaning you keep reducing the mass until it's below zero. As I said, nobody knows how to do that.

White cites negative vacuum energy observations have already been made (what we call dark energy) so there may be some future hope of a solution, and maybe he's right, but I don't see how that makes us any closer to developing a practical drive at this time, since we still don't even understand dark energy. I am glad to see a man of White's intelligence looking into it though.

Call me an optimist but i give us 300 years and i figure will have figured it out by then. Once somethings known to be possible it usually just a matter of time.

reply to post by KrzYma

GargIndia made a suggestion that maybe we should stick to discussing things that are observable. We may have some differences of opinion but I think that's probably a good suggestion.

There is currently no known way to observe the interior of a black hole so discussion about the nature of the interior seems like somewhat of a derailment of the general discussion we've been having about observable evidence related to relativity.

dragonridr
Call me an optimist but i give us 300 years and i figure will have figured it out by then. Once somethings known to be possible it usually just a matter of time.

I'm a Star Trek fan so I'd like to see warp drives, and I do have some hope, but it doesn't seem just around the corner. A lot can happen in 300 years. I try to be open-minded to both possibilities:

-Warp drive may be possible
-Warp drive may not be possible

The hope in me wishes it's possible, but the skeptic in me says there's no guarantee it will be possible, so only time will tell.

Arbitrageur
reply to post by KrzYma

 

GargIndia made a suggestion that maybe we should stick to discussing things that are observable. We may have some differences of opinion but I think that's probably a good suggestion.

There is currently no known way to observe the interior of a black hole so discussion about the nature of the interior seems like somewhat of a derailment of the general discussion we've been having about observable evidence related to relativity.

dragonridr
Call me an optimist but i give us 300 years and i figure will have figured it out by then. Once somethings known to be possible it usually just a matter of time.

I'm a Star Trek fan so I'd like to see warp drives, and I do have some hope, but it doesn't seem just around the corner. A lot can happen in 300 years. I try to be open-minded to both possibilities:

-Warp drive may be possible
-Warp drive may not be possible

The hope in me wishes it's possible, but the skeptic in me says there's no guarantee it will be possible, so only time will tell.

edit on 6-2-2014 by Arbitrageur because: clarification

agree !

dragonridr
...
Call me an optimist but i give us 300 years and i figure will have figured it out by then. Once somethings known to be possible it usually just a matter of time.

If things go on like they do the last 100 years, there will be no human on Earth in 300 Years... sorry !

dragonridr
When i read it i think they didnt put the total path of the light beam obviously longer then 62 nano seconds.

I think I found a way to speculate about the nature of the typo. It's 60 feet, so you're right that path is roughly 310 times as long as 6cm.

dragonridr
Ok i found the NEC press release on the experiment but still no paper. But ill say CBS just read the labs press release so they got the idea generally i guess.

In the experiment, NEC scientists measured the time taken by a pulse of light to pass through a 6cm-long specially prepared chamber containing cesium gas*2. The 3-microsecond long pulse of light would normally take only 0.2 nanoseconds to pass through the chamber in a vacuum. But when passed through the specially prepared chamber, light emerged 62 nanoseconds earlier than it would have had it passed through the chamber in a vacuum. This unusual phenomenon is the result of "anomalous dispersion", an effect not seen in nature in transparent materials and is created by the non-natural thermal state of the cesium gas used in the chamber.

abcnews.go.com...

The pulse traveled 310 times the distance it would have covered if the chamber had contained a vacuum. ....
This produces an almost identical light pulse that exits the chamber and travels about 60 feet before the main part of the laser pulse finishes entering the chamber, Wang said.

So, 60 feet divided by 6cm is about 310 times the speed of light, as is 62 nanoseconds divided by 0.2 nanoseconds. It still sounds like backward time travel, though the article emphasizes information can't travel back in time so they are apparently aware of the implication.

Now this is of topic, sorry...

You guys surely remember the neutrino experiment on the Swiss Italian border ?
They have claimed the speed of light was broken by this experiment as the neutrinos travelled faster than light.
Later this was disclaimed to some errors or whatever.

I hear the argument how accurate scientists are, how the measurement is better and better.
Do you think those scientists have claimed to break the speed of light without being really sure about it ?

What happened next ?
unfortunately there was an error... was there ?
or maybe speed of light shall not be broken ?

my big problem with relativity and QM is the maths, this formulas are wrong !

"if there are 3 people in a room, and 5 people come out of this room, 2 people need to come in for the room to be empty"
3-5+2=0

But there is no negative energy. Energy is always positive. Even if one force cancel the other, the net force has doubled.

And once again, if gravity is an acting force, where does it come from? surely not from the mass, mass doesn't change, or is our Sun loosing mass ( Sun as it's claimed to be 99% the mass of solar system )

scientific woodoo

reply to post by KrzYma

I've done a lot of measurements and they always have things like bias and errors. Some are known and some are unknown. But even before the outcome of the neutrino experiment was determined, most people familiar with measurement error already suspected that. Why? Because it was a very small effect and it contradicted other more accurate measurements, like those of neutrinos from supernova 1987A, which didn't travel faster than light and would have arrived much earlier had they been traveling at the speed the CERN experiment implied. The speed of light is known pretty accurately, but the gravitational constant is harder to measure because it's such a weak force, and therefore has greater uncertainty.

reply to post by Arbitrageur



"We've sent photons to the moon in the Apollo reflector experiments, so all we'd need to do to measure the time and distance between photon impacts is to install separate detectors and a simple timing circuit, so photons from Earth impacting the moon are measurable, but that experiment hasn't been set up on the moon yet. It's kind of like predicting that replacing a bald tire with a new tire will allow you to drive a car further without a blowout. It's practically a tautology so there's not much point in even conducting such an experiment, when there's really no question about what the result will be. "

No, the experiment will fail even if built. You can place multiple sensors in a straight line (in the path of moving laser). Once you do that, you will find it does not work according to your theory.

"The other result where the experiment has already been done, we haven't found the paper. That's the one where dragonridr posted a summary of the paper earlier in the thread about light traveling faster than c through cesium, and Phage posted something about it possibly being a phase/group velocity type thing."

There are errors in the experiment. When you use a pulse, it has a duration. It is like a train. The front of the train will exit a bridge earlier than the rear of the train. This experiment has significant measurement errors.

I have said it earlier on another thread - a particle can move faster than light, and it happens all the time. However measuring the speed of a moving particle is an affair that your science has not figured out yet.

Arbitrageur

dragonridr
When i read it i think they didnt put the total path of the light beam obviously longer then 62 nano seconds.

I think I found a way to speculate about the nature of the typo. It's 60 feet, so you're right that path is roughly 310 times as long as 6cm.

dragonridr
Ok i found the NEC press release on the experiment but still no paper. But ill say CBS just read the labs press release so they got the idea generally i guess.

In the experiment, NEC scientists measured the time taken by a pulse of light to pass through a 6cm-long specially prepared chamber containing cesium gas*2. The 3-microsecond long pulse of light would normally take only 0.2 nanoseconds to pass through the chamber in a vacuum. But when passed through the specially prepared chamber, light emerged 62 nanoseconds earlier than it would have had it passed through the chamber in a vacuum. This unusual phenomenon is the result of "anomalous dispersion", an effect not seen in nature in transparent materials and is created by the non-natural thermal state of the cesium gas used in the chamber.

abcnews.go.com...

The pulse traveled 310 times the distance it would have covered if the chamber had contained a vacuum. ....
This produces an almost identical light pulse that exits the chamber and travels about 60 feet before the main part of the laser pulse finishes entering the chamber, Wang said.

So, 60 feet divided by 6cm is about 310 times the speed of light. It still sounds like backward time travel though.

edit on 6-2-2014 by Arbitrageur because: clarification

The more i think about it im sure were dealing with quantum tunneling it would give us the negative result in the experiment. The only other option would be the compression of the wave function indeed caused the energy to exceed the speed of light making it arrive earlier. But option number two im still skeptical and theres plenty of research with similar results involving quantum tunneling.

Arbitrageur
reply to post by KrzYma

 

I've done a lot of measurements and they always have things like bias and errors. Some are known and some are unknown. But even before the outcome of the neutrino experiment was determined, most people familiar with measurement error already suspected that. Why? Because it was a very small effect and it contradicted other more accurate measurements, like those of neutrinos from supernova 1987A, which didn't travel faster than light and would have arrived much earlier had they been traveling at the speed the CERN experiment implied. The speed of light is known pretty accurately, but the gravitational constant is harder to measure because it's such a weak force, and therefore has greater uncertainty.

This thread is becoming very complex.

Can we do it this way - one experiment (or scenario) is discussed at one time. Once a consensus is established, then the discussion moves to the next.

dragonridr
The more i think about it im sure were dealing with quantum tunneling it would give us the negative result in the experiment. The only other option would be the compression of the wave function indeed caused the energy to exceed the speed of light making it arrive earlier. But option number two im still skeptical and theres plenty of research with similar results involving quantum tunneling.

I found another source that more clearly states it's probably a group velocity thing than the source Phage posted implying the same thing:

Re: Did NEC-Princeton Labs conduct an experiment showing light to travel FTL?

Is the article talking about the group velocity or the phase velocity in the
experiment? The two velocities are blurred in the complex experiment conducted
at the NEC Princeton Laboratory. While the phase velocity may exceed the
speed of light, any useful information modulated on the wave generally travels at
the group velocity. Most scientists consider the group velocity to always be less
than the speed of light. The phase velocity is the velocity of the wave front of a
single, an undistorted sine wave at the frequency of interest. The reference book
Ramo et al states: “The group velocity is often referred to as the “velocity of
energy travel”. This concept has validity for many important cases, but is not
universally true.” Other scientists simply state the group velocity is the velocity
that useful information is transmitted. Recent experiments, such as the one
described in the article, blur the distinction between group velocity and phase
velocity and are the cause of many arguments between scientists and engineers.
Certainly the experiment in which the speed of light is slowed down to 38 miles
per hour is a remarkable achievement. However, exceeding the speed of light is
very suspect in view of Einstein’s Relativity Theory, which have held up
remarkably well for over 90 years. However, scientists must keep an open mind
on the subject and perhaps there are flaws in relativity, just as relativity showed
the flaws in Newton’s Laws of Motion.

He then goes on to discuss some phase velocity/group velocity issues in more detail and with examples, but anyone interested can read the rest of that link. It's not conclusive but it's interesting.

GargIndia
This thread is becoming very complex.

Can we do it this way - one experiment (or scenario) is discussed at one time. Once a consensus is established, then the discussion moves to the next.

That's a bit slow in my opinion, though I did agree with your suggestion to focus on observable things. The OP's question was answered around page 4 so naturally there's been some topic drift since then but this is still a speed of light topic which is at least somewhat related. I can walk and chew gum at the same time, but not while juggling 3 balls and replying to e-mails, so we all have our limits, but I think most people have a limit greater than one, especially for something as slow moving as a thread like this.

GargIndia
No, the experiment will fail even if built. You can place multiple sensors in a straight line (in the path of moving laser). Once you do that, you will find it does not work according to your theory.

Why do you say this; on what basis?

KrzYma
And once again, if gravity is an acting force, where does it come from? surely not from the mass, mass doesn't change, or is our Sun loosing mass ( Sun as it's claimed to be 99% the mass of solar system )

scientific woodoo

The sun converts about 600 million tons of hydrogen into 596 million tons of helium each second, so the sun is losing mass at the rate about 4 tons a second, but this isn't the source of gravity, it's the source of sunlight (and other EM radiation and energy from the sun). Gravity is just a force and it doesn't require mass loss. Why mass creates gravity is not fully understood, but it doesn't need to be to make observations and models based on them which make extremely accurate predictions. It would be nice to have a deeper understanding than we do though.

KrzYma
Now this is of topic, sorry...

You guys surely remember the neutrino experiment on the Swiss Italian border ?
They have claimed the speed of light was broken by this experiment as the neutrinos travelled faster than light.
Later this was disclaimed to some errors or whatever.

I hear the argument how accurate scientists are, how the measurement is better and better.
Do you think those scientists have claimed to break the speed of light without being really sure about it ?

What happened next ?
unfortunately there was an error... was there ?
or maybe speed of light shall not be broken ?

It was traced back to a faulty cable if i remeber they replaced it and re ran the experiment. and the anomaly disappeared.

my big problem with relativity and QM is the maths, this formulas are wrong !

"if there are 3 people in a room, and 5 people come out of this room, 2 people need to come in for the room to be empty"
3-5+2=0

Thats the great thing about science if there wrong someone will correct it such as your math here obviously that would send up red flags for people. If you want to look at a particular equations we can go over it i dont mind i do it all the time with grad students.

But there is no negative energy. Energy is always positive. Even if one force cancel the other, the net force has doubled.

Im afraid work done at cern disagrees with you.

And once again, if gravity is an acting force, where does it come from? surely not from the mass, mass doesn't change, or is our Sun loosing mass ( Sun as it's claimed to be 99% the mass of solar system )

scientific woodoo

Totally lost me on the sun im not sure you made any sense here i suspect it sounded better in you head.As far as mass and gravity yes the to are linked and thanks to Einstein we can link energy and mass. This is why Einstein didnt see mass as the cause of gravity but energy in a particular point in space time. This confuses alot of people but essentially the higher the energy the more it warps space time. This is what his field equations are all about.

Since you like videos heres a good start.

GargIndia

Arbitrageur
reply to post by KrzYma

 

I've done a lot of measurements and they always have things like bias and errors. Some are known and some are unknown. But even before the outcome of the neutrino experiment was determined, most people familiar with measurement error already suspected that. Why? Because it was a very small effect and it contradicted other more accurate measurements, like those of neutrinos from supernova 1987A, which didn't travel faster than light and would have arrived much earlier had they been traveling at the speed the CERN experiment implied. The speed of light is known pretty accurately, but the gravitational constant is harder to measure because it's such a weak force, and therefore has greater uncertainty.

This thread is becoming very complex.

Can we do it this way - one experiment (or scenario) is discussed at one time. Once a consensus is established, then the discussion moves to the next.

Ok what would you choose to discuss i believe you think relativity is wrong so which equation do you have a problem with and please no more videos i was kinda playing a cruel joke with the 2 hr video. Only grad students should endure that kind of pain.

reply to post by dragonridr


You can take the "cesium vapour" experiment that claims to propagate light so many times the actual speed of light first.

It is absolutely fine. Let us leave all other scenarios/experiments for a later date.

Please provide a link to the paper published on this experiment (not news items) and any other supporting documents that are available for public share.

Any discussion on a scientific experiment need the knowledge of experimental setup as well as data generated. So good information is necessary. Without that any discussion will not be a solid one or reach any conclusions.

Link between mass and energy
------------------------------------------

There is a problem with experiments. This problem is "containment".

When you run a nuclear reaction, the outcome is new matter (that you can measure) and some particles (which run away), and energy (which you can measure).

As I said earlier, the input and output of experiment need to be controlled. If not, you have a problem.


Gravity
----------

Gravity is a very mysterious force, so difficult to understand.
Just like other forces of nature (or God), this can put you in spin.
'Veda' says God is present everywhere, yet cannot be seen. God is present everywhere through His power called "Agni" which you can understand as energy.

This energy is acting on every particle in the Universe, and is responsible for the the structure and shape of the objects that you see.

Would you ever understand gravity with your methods? I have my doubts.
However you can benefit from God's bounty, as you already are. Humans can use the natural world for their advantage, if they learn and live in harmony.

GargIndia
Link between mass and energy
------------------------------------------

There is a problem with experiments. This problem is "containment".

When you run a nuclear reaction, the outcome is new matter (that you can measure) and some particles (which run away), and energy (which you can measure).

As I said earlier, the input and output of experiment need to be controlled. If not, you have a problem.

Ok lets start here nuclear reactions dont create matter they transform it to energy. Nothing can create or destroy something that doesnt already exist it can only be transformed. Kind of like vedics who believe god cant create or destroy a soul.

Gravity
----------

Gravity is a very mysterious force, so difficult to understand.
Just like other forces of nature (or God), this can put you in spin.
'Veda' says God is present everywhere, yet cannot be seen. God is present everywhere through His power called "Agni" which you can understand as energy.

Where gravity comes from we know its a curvature of space time. What we dont know is how mass causes this curvature in the first place we know there related we see that we want to know why.As far as God far be it from me to disprove a mans beliefs ill just say thats not an answer science would be willing to accept.

This energy is acting on every particle in the Universe, and is responsible for the the structure and shape of the objects that you see.

I agree energy and the conversion of energy is the key to the universe.

Would you ever understand gravity with your methods? I have my doubts.
However you can benefit from God's bounty, as you already are. Humans can use the natural world for their advantage, if they learn and live in harmony.

What methods would that be you lost me??? Do you mean observation and testing? See im glad you found something you can believe in but that doesnt make it true thats why its called faith. As far as living in harmony in a perfect world we could learn to live in harmony unfortunately we are far from perfect.So were destined to muddle through the best we can.