# Speed of light can be attained.

#### benzun_1999

You must have seen my topic "speed of can be arttained". I here in this thread am asking all of you a simple question: Can speed of light be attained.
I firmly feel it can be attained, all we need to know is when light acts as a particle and when it acts as a wave?

-benzun
All for god.

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#### meteor

No, the velocity of light is not attainable. Even going in the most expensive ultra-rapid rocket that you could imagine, you will notice that the velocity of light relative to you is always c.
You have to forget the idea that there's an absolute space

#### chroot

Staff Emeritus
Gold Member
Hey, cool... I turned on my flashlight and the light attained light speed very handily.

All kidding aside, the speed of light as a fundamental obstacle to motion has nothing at all to do with quantum mechanics. The wave-particle duality is a misnomer, anyway. The light does not behave sometimes as a wave or sometimes as a particle. It acts all the time as both. You can design experiments which our brains will identify as dealing with "particle quantities" like momentum, or experiments which our brains will identify as dealing with "wave quantities" like wavelength -- but there is really only one thing in the microscopic world, and it is neither wave nor particle, but a mixture of both concepts.

Also, you might like to know that, for a captain aboard a starship, there is absolutely no limit to how fast his speedometer can read. He can accelerate until, according to his watch, it takes him only fractions of a second to fly from star to star. He could fly across the galaxy in what would be minutes according to his watch. This may seem like faster than light travel to you, since you know that light takes 100,000 years to cross the galaxy. The trick is what his earth-bound buddies would see: they'd never see him going faster than light; instead, they'd see his watch running slow.

- Warren

#### quantum

I saw the title of your post and instantly got my hopes up, wishing you read on a science website somewhere that there is a new theory to contradict Einstein.

Einstein was a brilliant scientist who proved that all things that have mass cannot quite reach light speed. Damn Einstein for proving that and leaving us wishing there was someway we could!

#### chroot

Staff Emeritus
Gold Member
Originally posted by quantum
Einstein was a brilliant scientist who proved that all things that have mass cannot quite reach light speed. Damn Einstein for proving that and leaving us wishing there was someway we could!
Einstein never proved anything, and neither did any other physicist. Physics does not involve proof -- mathematics does. What Einstein did was to develop and publish a theory. The predictions of this theory have thus far agreed incredibly well with experimental results, but that does not mean that the theory has been proved. In a devil's-advocate kind of way, it just means we haven't found the right experiment yet.

Besides, everyone knows relativity is wrong -- it's not the whole story, because it isn't compatible with quantum mechanics. Something else -- string theory, loop quantum gravity, or something yet to be invented, will eventually amalgamate relativity and quantum theory. This new theory will supplant both its predecessors, including them as special cases of a larger generality. It is entirely possible that faster than light communication or travel will be possible in the framework of that new theory, though in all probability anything like that will be restricted to subatomic domains.

- Warren

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Dearly Missed
When you say relativity is not compatible with quantum mechanics, it is important to stress that it is General Relativity that has that problem (or Quantum Mechanics has that problem with respect to General Relativity).

Special Relativity has been built into quantum mechanics since Dirac. Including all that stuff about the speed of light.

#### chroot

Staff Emeritus
Gold Member
When you say relativity is not compatible with quantum mechanics, it is important to stress that it is General Relativity that has that problem (or Quantum Mechanics has that problem with respect to General Relativity).

Special Relativity has been built into quantum mechanics since Dirac. Including all that stuff about the speed of light.
Indeed.

- Warren

#### dumpy

I have to say that relativity is not wrong. Just as Newtonian mechanics isnt wrong. They are just models to help us predict things. Thats what physics is all about, models. Obviously relativity isnt always applicable, just like Newtons laws, but they are not wrong when applied correctly.

Most of physics is about making the correct approximation (or correct model) in order to get at the science. Most things are simply not solvable analyticaly without approximation. But we have got this far by knowing when we can approximate.

As pointed out, no theory will ever be right. There are two reasons for this:
1) it would only take one smart arse to design an experiment where the theory wasnt applicable.
2) they are not suposed to be right, just models of reality.

Staff Emeritus
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Dearly Missed
Granting that what you say is true in general, there has not been any reliable evidence yet to show that special relativity - the Lorentz transformations - is false. And the only evidence that it is a special case is, ta da! general relativity and its experimental evidence.

#### russ_watters

Mentor
Originally posted by dumpy
I have to say that relativity is not wrong.
"Incomplete" is the word I prefer. Too many people misinterpret it when the word "wrong" is used.

#### Hawkeye

There are no definite laws pertaining to the speed of light as people are always bringing up possible points that may be true. Until there is a theory everybody agrees upon, all things about light is just theoretical. For example, Einstein said that the speed of light was constant, but I believe in an issue of Discover, someone else believes that light is not constant. I however am a believer that the speed of light is constant and that Einstein was correct in stating that matter cannot achieve the speed of light.

#### chroot

Staff Emeritus
Gold Member
Originally posted by Hawkeye
There are no definite laws pertaining to the speed of light as people are always bringing up possible points that may be true. Until there is a theory everybody agrees upon, all things about light is just theoretical. For example, Einstein said that the speed of light was constant, but I believe in an issue of Discover, someone else believes that light is not constant. I however am a believer that the speed of light is constant and that Einstein was correct in stating that matter cannot achieve the speed of light.
While there are doubtless many theories out there, Einstein's relativity is the only one currently supported by a preponderance of experimental evidence and theoretical consistency.

- Warren

#### tinto_alencherry

ofcourse it is possible to attain speed of light with out caring much on when light turns its nature.
Dr. Tinto

#### benzun_1999

i feel.................

i might be crazy but i feel it is possible due to the following reason..........

light is always emmited at the 3*10^3 m/s so if they were particles they gould have a opposite fore according to newtons 3rd law which will make us reach that speed.

the universe is full of radiation so using it you can travel in the speed of light.

i might be crazy so if i am please correct me.

benzun
all for god

#### petmar

Re: i feel.................

Originally posted by benzun_1999
i might be crazy so if i am please correct me.
okay, i will... sorry...
according to relativity (both of them) time dialation occurs when you approach the speed of light. this means that &Delta;t->0. as &Delta;t/t->0, then force (F=ma=m(d/(t^2))also approaches 0.
since
lim(v->c)&Delta;t=0
and
lim(&Delta;t->0)F=0
then
lim(v->c)F=0
therefore
lim(v->c)&Delta;v=0
QED

#### petmar

as for the nature of light...

seems to me that the energy of light changes with time.
now, before you go denouncing this idea, listen... when light travels, it propagates as a wave. since this is true, this wave has maxima, minima, and zero-amplitude points (nodes). if that is true, then maybe the nodes are the points where photons are fully particles, the maxima and minima are the points where photons are fully wave phenomena, and the in-between parts are some inhomogeneous mixture of matter and energy.

tell me what you think.

#### chroot

Staff Emeritus
Gold Member
Re: Re: i feel.................

Originally posted by petmar
time dialation occurs when you approach the speed of light.
I'm sorry, but this is so sloppily said as to be entirely incorrect. Inside the helm of a spaceship moving at 0.999c with respect to the earth, the captain will notice absolutely nothing wrong. His pendulum clock will dutifully continue ticking at the same rate it always did.

- Warren

#### chroot

Staff Emeritus
Gold Member
Re: as for the nature of light...

Originally posted by petmar
when light travels, it propagates as a wave.... tell me what you think.
I think it's equally correct to say that light propagates as discrete particles called photons.

I further think that there is no distinction between "wave" and "particle" in the quantum realm -- there is only one kind of thing. This kind of thing is not found on macroscopic scales, however, so we have little experience with them, and constantly try to apply "wave" or "particle" properties to them -- rather improperly.

- Warren

#### kernelpenguin

If I understood correctly, then according to De Broglie every particle can behave like a wave. Everything has a wavelength.

wavelength = h / (m * v)

So you are a bit wrong there. This does happen in the macroscopic world, but the effects are so small that we don't even detect it

I'm still trying to grasp De Broglie's ideas fully here. Can an electron, if it behaves like a wave, (and it does inside an atom) cancel itself out of existance through wave interference? Or can it amplify itself? Wouldn't this contradict a certain law of thermodynamics?

#### chroot

Staff Emeritus
Gold Member
Originally posted by kernelpenguin
I'm still trying to grasp De Broglie's ideas fully here. Can an electron, if it behaves like a wave, (and it does inside an atom) cancel itself out of existance through wave interference? Or can it amplify itself? Wouldn't this contradict a certain law of thermodynamics?
Keep in mind that the "wave" of an electron is not really something in the electron waving about. What is waving is the probability density function that says where you are likely to find the electron when you look for it. Every such measurement will indicate an electron existing at one specific point in space; many such measurements will show a probability distribution.

Electrons certainly can interfere, diffract, and so on -- they can do everything photons do. If you fire electrons through two (very!) tiny slits in an opaque wall, the electrons' wavefunctions will interfere. A detector moving parallel to the wall will measure lots of electrons coming through in some places, and no electrons at all coming through in others.

- Warren

#### kernelpenguin

But can an electron end up in a feedback loop and amplify itself somehow? From what I've learned in physics (which is not much) then the orbit of an electron could be viewed as a one-dimensional line that turns back onto itself creating a finite loop where it propagates as a wave.

Isn't this the reason why Bohr's model of an atom says that an electron can only stably exist in specific distances from the nucleus? Because in any other position it would interfere with itself?

And whenever someone brings up probability, I always think of what Einstein once said: "God does not play dice." Although according to Schröedinger, it would be impossible to measure the exact position and speed of an electron, is it really because we can't measure the "position" or "speed" of a wave?

#### chroot

Staff Emeritus
Gold Member
Originally posted by kernelpenguin
But can an electron end up in a feedback loop and amplify itself somehow? From what I've learned in physics (which is not much) then the orbit of an electron could be viewed as a one-dimensional line that turns back onto itself creating a finite loop where it propagates as a wave.
This a very naive, schematic sort of view. The electron is obviously not a line.
Isn't this the reason why Bohr's model of an atom says that an electron can only stably exist in specific distances from the nucleus? Because in any other position it would interfere with itself?
This was Schrodinger's proposition.
And whenever someone brings up probability, I always think of what Einstein once said: "God does not play dice." Although according to Schröedinger, it would be impossible to measure the exact position and speed of an electron, is it really because we can't measure the "position" or "speed" of a wave?
It's position and momentum, not speed, that we can't measure simultaneously. A sharply-peaked wave packet has a well-defined position, but a poorly defined wavelength. A single-tone wave has a well-defined wavelength, but a poorly defined position.

- Warren

#### petmar

*nods in agreement*

http://www.scienceprof.com/thumbs/deBroglie.jpg
as you see here, as long as the end of the electron's proposed path uniformly matches its beginning, and has an integer number of nodes, it can be said to have a discrete wavelength. however, i fail to comprehend exactly how this bridges the gap between the probability of electron distribution, and the shapes of electron orbitals.
anyone want to fill me in on that?

#### benzun_1999

sorry to be late..........

before i begin i would ask you all forgiveness for my wrong statment.
to tell the truth i am just a school going student and i am not aware of so many things as you are aware of.

i feel that the photons are always present in a wave due to the following results obtained from the photoelectric effect:-

1) more the intensity of the light, that is more the photons(energy packets) the more the number of electrons jumping out.

intensity does not change the frequency so there fore there is less nodes, but still the number of electrons are more.

so i feel that the photons are not the nodes.

-benzun
All for God
If i am wrong correct me, just as you did before.

#### actinide244

in my mind, the speed of light can be attained despite what conventional physics may say. in a black hole, when the speed of light remains c but is sobordinate to gravity, on would think that the force of gravity applied to something, (theoretically having no limit given the resource) has the propensity for taking a body with mass beyond the speed of light.

what would happen to the mass is a different story.

as the story goes, this would be outlandish because of the fact that a blackhole's swallowed content would amass a great deal of momentum and mass would inevitable reap havvock. we have never seen evidence of any such occurance.

i am convinced, however, that speed is proportional to force and tro my novice mind, c is not a barrier, but is simply the speed of light.

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