Light speed...

[swansont]

Hey, this is confusing. So does that mean that If I travel at +0.6C and someone else travels at-0.6C (sign conventions), then we both will see light at C. Now if there's a stationary observer, won't he see light at 1+0.6=1.6C ??? And will mine and the other fellow's relative velocity be 0.6C+0.6C=1.2C. Or is there another formula at high speeds like swanson said.

 

The observers would see light at c, but of different frequencies. They would never measure another observer's speed as exceeding c; once you start moving fast you find that speeds don't add linearly (we just don't see it at small speeds). Your two observers would see each other moving at about 0.88c. See here

[Pinch Paxton]

Everybody wants this (and quantum mechanics) to "make sense." Sorry. nature behaves differently at small scales and high speeds. Leave your "every-day behavior" expectations at the door.

 

unless of course the theories are wrong causing the quantum mechanics to appear not to make sense. My quantum mechanics make sense, but I do not agree with everything that I read.

 

Pincho.

[swansont]

unless of course the theories are wrong causing the quantum mechanics to appear not to make sense. My quantum mechanics make sense' date=' but I do not agree with everything that I read.

 

Pincho.[/quote']

 

Relativity and QM have a few years of history of actually working.

 

What is "your" QM?

[Sayonara]

Don't ask.

 

He thinks whatever he can imagine is 'as likely as' the latest models.

[Crash]

Just thinking would light have momentum, should do cause of that guys experiment with the moving thing in the vacuum. then p=mv

pt=pi+pf =(m.c)+(m.c)......does this mean that light has different mass's? for different energies?

[ski_power]

Ok, I understood swansont. Silly me.

 

Crash, Aren't light particles massless? Or are you talking of relativistic mass?

[swansont]

Just thinking would light have momentum' date=' should do cause of that guys experiment with the moving thing in the vacuum. then p=mv

pt=pi+pf =(m.c)+(m.c)......does this mean that light has different mass's? for different energies?[/quote']

 

The momentum of a photon is E/c. Which means you can scatter photons off of atoms and change their momentum, which is the basis for laser cooling and trapping (Nobel prize in 1997 for Chu, Phillips and Cohen-Tannoudji)

[ski_power]

Laser cooling

That's the process to create a Bose-Einstein Condensate right? Followed by evaporative cooling.

[swansont]

That's the process to create a Bose-Einstein Condensate right? Followed by evaporative cooling.

 

Yes, although laser cooling can do lots of other things - lots of investigations into gases where the atoms move slowly. Cold collisions, atomic clocks, trapping radioactives for nuclear investigations, atom optics (atoms moving slowly have an appreciable deBroglie wavelength)

 

Here is a list of labs around the world that do atom traps. Fairly complete for research labs, I expect, but there are undoubtedly a few omissions.

 

This is a fun java applet that demonstrates evaporative cooling.

[Guest wallac]

If you manage to travel within speed of light you would become moving black hole. Every observation of light speed and what would happend with "OUR" time if we could travel that fast depends of referent system we are using during observation. That's the key. Time and space are not dependable vars. They simply exist in the way we can see them. Light speed is speed of information that is connecting events in space. Every one have to understand that infinity is still growing biger and smaller in two directions +inf and -inf and it never stop moving biger and smaller until becoms equal in some point.

[Dave]

If you manage to travel within speed of light you would become moving black hole. Every observation of light speed and what would happend with "OUR" time if we could travel that fast depends of referent system we are using during observation. That's the key. Time and space are not dependable vars. They simply exist in the way we can see them. Light speed is speed of information that is connecting events in space. Every one have to understand that infinity is still growing biger and smaller in two directions +inf and -inf and it never stop moving biger and smaller until becoms equal in some point.

 

I won't even begin to point out the flaws in this post. But nevermind

[Guest wallac]

I forgot to mention that I red all of that somewhere and it make sense to me.However you are right about lack of possibility being true everythig I wrote. An interesting theory could be good inspiration or way for right one.

[Crash]

http://www.cnn.com/2000/TECH/space/07/20/speed.of.light.ap/

[swansont]

[url']http://www.cnn.com/2000/TECH/space/07/20/speed.of.light.ap/[/url]

 

This is called anomalous dispersion. No violations of causality occurred.

[SockCymbal]

so no one here understands the answer to the my main question in this thread?

[Guest The Don]

I've obviously missed something with all this, but if one accelerates anything continuously, surely light speed will eventually be reached.

And what on earth has time got to do with it???

We measure by a static tick of the clock hand not some fanciful theorem.

 

by not applying a mathematical principle it seems possible???

[Thales]

Special relativity is more than a fanciful theorem. Its the way of the world we live in. First learn it inside out and then question it. I know your probably not still around SockCymbol but it has to do with length contraction and time dialation of which, without reading the whole thread, an explaination has been attempted (i would hope).

 

People have been trying to find violations of relativity since Einstien thought it up. The fact that not one of those supposed violations has stood the test of time when the theory itself still stand says alot for it validity.

 

The Don: As you accelerate something close to light it gets heavier and heavier and it takes more energy to accelerate it. It would take an infinite amount of energy to accelerate and object with mass to the speed of light.

[Aeschylus]

To paraphrase Bernard Schultz in his book 'A First Course in General Relativty': Special relativity is probably the most tested theories in physics, as it is tested everyday under the most rigorous scientific conditons in particle accelerators around the world.

[Aeschylus]

unless of course the theories are wrong causing the quantum mechanics to appear not to make sense. My quantum mechanics make sense' date=' but I do not agree with everything that I read.

 

Pincho.[/quote']

 

Special relatvity and quantum mechanics are comp0letely compatible and I do not believe anyoone has ever thought otherwise. Schroedinger formulated the fundmantal equation of quantum mechnaics in 1925, only one year later in 1926 was the Klein-Gordon equation formulated (initially rejected due to negative proabilty densities, but it didn't take long for phycists to relaize that tyey could be interpreted in a physical meaningful way) and three years later in 1938 the Dirac equation was formulated (which can be seen as perhaps the true birth of relatvstic 'quantum mechanics'). So you see that quantum mechnaics and relativstic 'quantum mechanics' have been around for just about the same period of time, which is not suprsing given that QM is partly based on SR.

[5614]

you can be traveling .9999 the speed of light....and it will still be moving C away from you

 

no it wont, if you speed up, light still travels at the same speed, your speed does not effect the speed of light around you.

 

but if you go .1 more...it will instantly stop.

 

(a) this is impossible

(b) however, if you were, theoretically, light would not stop, it would still travel at C, its just you would be travelling at C + 1, therefore it would be like overtaking a car;

if car A is doing 70mph and i overtake them at 90mph, car A doesnt stop, it keeps going, just slower than me.

it is the same if you went faster than light, which would result in you going back in time. [remember post (a) though!]

[Aeschylus]

no it wont, if you speed up, light still travels at the same speed, your speed does not effect the speed of light around you.

 

No light always travels at c to all inertial observers so whether you speed up or slow down light is still travelling at c in your MCIF (momentarily comoving inertial frame). Remeber- relativty is all about, well, relativty- there is no absolute frame of refernce to define an absolute speed.

 

Of course the light could be moving towards you at c tho'.

 

 

 

(a) this is impossible

(b) however, if you were, theoretically, light would not stop, it would still travel at C, its just you would be travelling at C + 1, therefore it would be like overtaking a car;

if car A is doing 70mph and i overtake them at 90mph, car A doesnt stop, it keeps going, just slower than me.

it is the same if you went faster than light, which would result in you going back in time. [remember post (a) though!]

 

a) correct, all objects with real mass must travel at speeds < c in any inertial frame and objects moving at c do not have MCIFs so we cannot talkabout thier refernce frames.

 

b) You cannot overtake light, because at whatever speed your travelling in some inertial frmae, in your own MCIF light is always travelling at c. Also we cannot say theoretically what would happen as the barrier totravelling at light speed and defing MCIFs for objects moving at lightspeed is theoretical itself.

[5614]

No light always travels at c to all inertial observers so whether you speed up or slow down light is still travelling at c in your MCIF (momentarily comoving inertial frame). Remeber- relativty is all about' date=' well, relativty- there is no absolute frame of refernce to define an absolute speed.

 

Of course the light could be moving towards you at c tho'.[/quote']

 

so are you saying that if i was travelling at C minus 1 mph then if i turned on a light, the light would travel faster than C?

 

You cannot overtake light, because at whatever speed your travelling in some inertial frmae, in your own MCIF light is always travelling at c. Also we cannot say theoretically what would happen as the barrier totravelling at light speed and defing MCIFs for objects moving at lightspeed is theoretical itself.

i know, i was saying theoretically, if you were travelling at C+1, i did say remember that it was impossible

[Aeschylus]

so are you saying that if i was travelling at C minus 1 mph then if i turned on a light, the light would travel faster than C?

 

I assume your using SI units (as for convience c is usually taken as 1 in natural units in special relativity). If you are travelling with a constantvelocity of m,magnitude 0.99999 c in some inertial frame and you turned on the lights, from th epoint of view of an observer in that frame the light would travel at c relative to them. BUT importantly from your point of view the light would travel at c relative to your ship.

 

 

i know, i was saying theoretically, if you were travelling at C+1, i did say remember that it was impossible

 

No, what I'm saying is you can't even say theortically what would happen.

[cooper267]

If nothing can travle faster than the speed of light then why can't light escape out of a black hole? , wouldn't that mean that the gravity was pulling the light faster than it can travle?

?and would in fact mean that light was travleing faster than itself................

 

and if black holes can keep light from escapeing how is that possiable if light has no mass? , wouldn't that mean it had mass to keep it from escapeing?

 

i don't believe for a second that there is a cosmic speed limit , just like it was said that no one would break the sound bearier , but hey guess what we did , the same with the speed of light bearier , and someone did get music to travle 5 times the speed of light , thats what a article i got said and it was boardcast all over the science channle , so how was that possiable , since the fastest thing we have to measure it is light........

but i think the theory is half thought , but then again this is only and opion...............

 

sorry about type o's , little drunk.................

 

I mean really lets use common sense here everything thats was ever said to be impossiable was broken so then why does there have to be a beairer on anything , in a universe of an infinity of possibilites.......

[swansont]

i don't believe for a second that there is a cosmic speed limit , just like it was said that no one would break the sound bearier , but hey guess what we did , the same with the speed of light bearier , and someone did get music to travle 5 times the speed of light , thats what a article i got said and it was boardcast all over the science channle , so how was that possiable , since the fastest thing we have to measure it is light........

but i think the theory is half thought , but then again this is only and opion...............

 

Sorry if this sounds overly blunt but ... this is science; opinions mean bunk. The half-thought stuff here is not the theory, which has been around for 100 years and continually tested throughout that time.

 

I suggest reading up on special and general relativity, and not rely so much on stuff that was broadcast all over the internet and science channel, since little details tend to get lost. The experiment to which you refer was another example of anomalous dispersion, to which I linked previously.

 

The basic stuff, like "why can't light escape a black hole" is easily googled or searched on these boards. Arrogance like "I don't believe for a second," along with the breach of decorum of five posts (and admittedly drunken ones at that) where one could have sufficed doesn't really motivate anyone to answer your questions.