Question about the speed of light....

[Spec138]

Yet, if the Universe is not infinite but contained then from the perspective of the whole from outside would determine when something happened apart from the relative time it happened from within.

I'm don't think we have enough information to make that leap quite yet.

That makes no sense what-so-ever, a laser moving at c away from a craft moving just slower than c instead of seeing a relative separation speed instead see the laser move away from them an actual c...and the ship in front which is moving at just slower than c sees the laser moving at them at c? Then c isn't constant.

Again according to this 3 light waves each traveling at c would thus be seen moving away from each other at c thus making them move at c+c.

If this stuff was obvious we wouldn't have needed Einstein to come up with it

According to the Big Bang theory we should.

All the BBT says is that the universe seems to have been muchhhhhh closer in the past.

[AsburySkinsFan]

The ship will see the laser approach at the speed of light .... observers on the front ship and observers on the rear ship will not agree when the ship in front exploded.

That makes no sense what-so-ever, a laser moving at c away from a craft moving just slower than c instead of seeing a relative separation speed instead see the laser move away from them an actual c...and the ship in front which is moving at just slower than c sees the laser moving at them at c? Then c isn't constant.

Again according to this 3 light waves each traveling at c would thus be seen moving away from each other at c thus making them move at c+c.

---------- Post added April-14th-2011 at 02:14 AM ----------

I'm don't think we have enough information to make that leap quite yet.

According to the Big Bang theory we should.

---------- Post added April-14th-2011 at 02:19 AM ----------

All the BBT says is that the universe seems to have been muchhhhhh closer in the past.

And yet, time is dependent upon space which means that time is contained within space, which means that outside of the edge of the furthest reaches of space we reach the edge of time and thus should see things without the constraints of relativity of time and space.

Oh and quit answering my post in the post before I ask the question...it's freaking me out! LoL!!!

---------- Post added April-14th-2011 at 02:22 AM ----------

If this stuff was obvious we wouldn't have needed Einstein to come up with it

And yet you still didn't deny that according to you that light sees light move away at c thus making the light in front move at c+c.

[DCSaints_fan]

That makes no sense what-so-ever, a laser moving at c away from a craft moving just slower than c instead of seeing a relative separation speed instead see the laser move away from them an actual c...and the ship in front which is moving at just slower than c sees the laser moving at them at c? Then c isn't constant.

It really is ... (according to all the observations we have made thus far)

Again according to this 3 light waves each traveling at c would thus be seen moving away from each other at c thus making them move at c+c.

Not sure what you mean by this, did you mean two or more light waves travelling in opposite directions? They won't observe c+c, they will observe c.... velocities don't add like that when dealing with light or speeds close to c.

Yes it took me about a week for my brain to accept this way back in Intro to Modern Physics (wish I had more physics). However it is logical and consistent. The language we use when speaking about these situations often has alot of ambiguity and/or built-in assumptions ... e.g. when speaking about velocities, times, etc. you always have to keep in mind "according to which observer", since there is no preferred reference.

[Spec138]

And yet, time is dependent upon space which means that time is contained within space, which means that outside of the edge of the furthest reaches of space we reach the edge of time and thus should see things without the constraints of relativity of time and space.

Oh and quit answering my post in the post before I ask the question...it's freaking me out! LoL!!!

I would still say you're making quite a big leap there, we're still not 100% sure what time is AFAIK.

And yet you still didn't deny that according to you that light sees light move away at c thus making the light in front move at c+c.

The photon is a mass less particle that doesn't experience time, therefore it can't observe velocities.

[Ancalagon the Black]

Asbury, I think where you're confusing people is with your description of "takes months and years." You have to say from whose perspective - from the ship's perspective, it wouldn't be months, but from a "stationary" object, it would.

Also, the apparent contradiction isn't a contradiction. It's only a contradiction if you think of time and space/distance as "fixed" things.

---------- Post added April-14th-2011 at 04:52 PM ----------

[/color]

That's what I thought I was saying by "As far as I know sound always moves at the speed of sound relative to the medium it's traveling in" but I don't think it was very clear and I still might be mistaken. I was under the impression that the wave would be traveling at the speed of sound relative to the Concorde but if it left the Concorde it would slow down to the speed of sound relative to outside and just increase its frequency. How far off am I here? Maybe I don't understand what Hubbs was saying.

Sorry, Spec, I misread your post. I thought you were saying that the principle of special relativity applies to sound (as in "the speed of sound through a given medium is constant from any reference point," which isn't true). But that's not what you were saying. Apologies.

[DCSaints_fan]

In regards to sound, since sound requires a medium, its also going to be dependent on the medium itself. Its going to vary depending on the compositon of the gas, the temperature and pressure.

The same goes for light, which travels at different speeds depending on the medium. Light does not require a medium, however.

[Spec138]

Apologies.

No need Anyone with Bertrand in their sig is good in my book

[AsburySkinsFan]

It really is ... (according to all the observations we have made thus far)

Not sure what you mean by this, did you mean two or more light waves traveling in opposite directions? They won't observe c+c, they will observe c.... velocities don't add like that when dealing with light or speeds close to c.

Put it this way, the ship behind fires three laser beams in quick succession at the ship in front, if what you way is accurate then the second laser (L2) beam will observe the first laser beam (L1) moving away from it at c, but since L2 is already moving at c then that means L1 is observed by L2 as moving at c+c, otherwise it's as I was talking about L2 sees L1 as being static in front of it and L3 sees L2 in the same way.

Yes it took me about a week for my brain to accept this way back in Intro to Modern Physics (wish I had more physics). However it is logical and consistent. The language we use when speaking about these situations often has a lot of ambiguity and/or built-in assumptions ... e.g. when speaking about velocities, times, etc. you always have to keep in mind "according to which observer", since there is no preferred reference.

I know this, but it still is contradictory, because it's like saying that Tony Stewart passing Jimmy Johnson in the Daytona 500, Jimmy sees Tony passing him at 200mph when in reality Jimmy really only observes Tony passing him at about 3 or 4mph because they are already both moving at close to 200mph.

---------- Post added April-14th-2011 at 07:46 AM ----------

I would still say you're making quite a big leap there, we're still not 100% sure what time is AFAIK.

AFAIK?

The photon is a mass less particle that doesn't experience time, therefore it can't observe velocities.

And yet light also behaves as a wave that can be measured, which involves distance and time.

[Corcaigh]

I'm not reading this whole thread . . . But has anyone mentioned Cerenkov Radiation yet?

And the answer to the OP question requires an understanding of inertial reference frames. :cool:

[polywog999]

So with Special Relativity the light will catch the ship ahead a speed that is faster than light can travel?

The rocket from the car will actually travel faster than the rocket can travel?

The whole point of relativity is that the faster we travel the slower the light moves away from us thus slowing time relative to the viewer.

Sorry, Ash....this is incorrect. The speed of light, in a vacuum is the only constant in the universe. If you are traviling @ 99.99999 % of C and you turn on your headlights....you will still be able to clock C at 186,288,397 mps.

[AsburySkinsFan]

Sorry, Ash....this is incorrect. The speed of light, in a vacuum is the only constant in the universe. If you are traviling @ 99.99999 % of C and you turn on your headlights....you will still be able to clock C at 186,288,397 mps.

Never said you couldn't, just like Jimmy Johnson would be able to clock Tony Stewart passing him at 200mph, even though he is only relatively passing him at 2 or 3mph, I've never said that light slows, but only appears to have slowed. In the same way that catching up with a tsunami in the open ocean in an aircraft appears to slow the wave, but doesn't actually slow it, the speed of the wave is still assumed to be constant even though it's relative speed to the observer is not.

[polywog999]

Never said you couldn't, just like Jimmy Johnson would be able to clock Tony Stewart passing him at 200mph, even though he is only relatively passing him at 2 or 3mph, I've never said that light slows, but only appears to have slowed. In the same way that catching up with a tsunami in the open ocean in an aircraft appears to slow the wave, but doesn't actually slow it, the speed of the wave is still assumed to be constant even though it's relative speed to the observer is not.

Ash, If you are traveling at 99.9999% of C and YOU turn on YOUR lights, it will have the same measurement for all observers; you, the guy going in the opposite direction, and even a stationary object.

It's a strange paradox, indeed.

Remember, your own speed will be relative to the other spaceships or stationary points in space, even your own size will be relative, but not the speed of light. It is consistently measured at 186,288,397 mps.

[AsburySkinsFan]

Ash, If you are traveling at 99.9999% of C and YOU turn on YOUR lights, it will have the same measurement for all observers; you, the guy going in the opposite direction, and even a stationary object.

It's a strange paradox, indeed.

BTW it's c not C....I'll be darned if I'm not going to be right about something in this stinking thread!!

It still sounds absurd, because how can the lasers observe another laser as moving away when they are both traveling at c if c is actually constant. If c were constant then the net separation of L1, L2, and L3 would be zero, and be observed as such.

............ship 1......lasers @ c.........ship 2

..........I__O__.....--.....--.....--.........I__O__

position x............1LY......................x+1LY

where LY=light year

It will take the lasers 1LY to reach where ship 2 was when the shots were fired, so how will ship2 observe those lasers hitting it at c?

[polywog999]

BTW it's c not C....I'll be darned if I'm not going to be right about something in this stinking thread!!

You have bested me....I bow to you good sir!

:notworthy

---------- Post added April-14th-2011 at 08:41 AM ----------

BTW it's c not C....I'll be darned if I'm not going to be right about something in this stinking thread!!

It still sounds absurd, because how can the lasers observe another laser as moving away when they are both traveling at c if c is actually constant. If c were constant then the net separation of L1, L2, and L3 would be zero, and be observed as such.

ship 1......lasers @ c............ship 2

I__O__.....--.....--.....--.........I__O__

If you would be able to travel @ 99.9999% of c, you would appear to be going much slower by my stop watch. @ a certain speed, the faster you went, you would almost appear too stop. YOU would not notice this....you would not "see" me, however, because I would appear to move too fast for your eyes.That the "relativity" part.

[Spec138]

AFAIK?

As far as I know.

And yet light also behaves as a wave that can be measured, which involves distance and time.

This has nothing to do with its ability to observe. Particles without mass traveling at c experience no time, they would experience the "birth" and "death" of the universe simultaneously, and are therefore not a valid frame and don't fit into Einstein's Special Relativity. If you really wish to pursue this further you should study up on Lorentz Transformations and their properties at c. By definition the frame of reference you are trying to use is invalid in nature.

Also if you look a couple of pages back before you jumped in, I posted the formula for how vector addition actually works instead of the Galilean model of speed1+speed2=speed3

[dockeryfan]

I love when people with only tenuous knowledge at best, mock others for not knowing what they themselves do not know.

Only on a message board.

[PokerPacker]

In regards to sound, since sound requires a medium, its also going to be dependent on the medium itself. Its going to vary depending on the compositon of the gas, the temperature and pressure.

The same goes for light, which travels at different speeds depending on the medium. Light does not require a medium, however.

the speed of light, however, is dependent on the medium in which it travels. there's a reason Polywog specified the speed of light through a vacuum. when it passes through air or water, it slows down and creates the effect we know as refraction.

[AsburySkinsFan]

I love when people with only tenuous knowledge at best, mock others for not knowing what they themselves do not know.

Only on a message board.

When did this happen?

[DCSaints_fan]

I love when people with only tenuous knowledge at best, mock others for not knowing what they themselves do not know.

Only on a message board.

I haven't seen any mocking on this thread ... vigorous disagreement, yes, but no mocking.

[polywog999]

honorary_hog is lurking this thread....get out here and FACE me like a man!

[HOF44]

The Hog don't like discussing space/time, Big Bang Theory, or any relativistic talk. Make his head spin like shootin Absinthe!

[JMS]

Light is an entirely different than a spaceship. The spaceship would not impart any extra velocity to a light it produces. The speed of light is the speed of light. Just like if you had a bullhorn yelling from a supersonic jet fighter, your words, starting in the same location as the jet, would not just automatically be travelling Mach 2. People on the ground would not hear it any sooner than they hear the jet, because the speed does not impart any extra velocity to the sound either.

Which is not accurate... Even from a less than modern locamotive the perspective of sound changes when viewed from the stationary and from the moving train. Sound is governed by newtonian physics... light is special and different.

---------- Post added April-14th-2011 at 05:03 PM ----------

So how come you can talk to someone in front of you on a supersonic jet? If, hypothetically, a stationary person was able to float in the sky and also let an airplane pass through him, and someone yelled from the back of a Concorde right as it passed through the Floating Man, wouldn't the FM perceive the sound from the yeller to be moving faster than the plane itself, and therefore faster than the speed of sound?

That's because sound is governed not by Einstein's theory of relativity but rather by Galelao's postulate of relativity... Sound is not constant nore are their threashholds where matter traveling bellow the speeed of sound can not travel above the speed of sound.. obviously...

Light is an entirely different animal.

---------- Post added April-14th-2011 at 05:09 PM ----------

the speed of light, however, is dependent on the medium in which it travels. there's a reason Polywog specified the speed of light through a vacuum. when it passes through air or water, it slows down and creates the effect we know as refraction.

I don't think that's exactly accurate. Refraction is not light slowing down but rather light bending at different angles based on wavelengths of colored light angleing differently.... For example if you pass a white light beam into a prism it bends into it compoenents colors. It doesn't slow down. nor does one colored light travel any faster than another color.

---------- Post added April-14th-2011 at 05:14 PM ----------

That's what I thought I was saying by "As far as I know sound always moves at the speed of sound relative to the medium it's traveling in" but I don't think it was very clear and I still might be mistaken. I was under the impression that the wave would be traveling at the speed of sound relative to the Concorde but if it left the Concorde it would slow down to the speed of sound relative to outside and just increase its frequency. How far off am I here? Maybe I don't understand what Hubbs was saying.

Let me try one more time, So if you are standing on a train platform and the train passes you can hear a different sound as the train is approaching and as it is moving passed you. This is called the doppliger effect and it is because the speed of sound is not constant. Stationary people do not percieve moving sound to be a constant.

[Spec138]

Let me try one more time, So if you are standing on a train platform and the train passes you can hear a different sound as the train is approaching and as it is moving passed you. This is called the doppliger effect and it is because the speed of sound is not constant. Stationary people do not percieve moving sound to be a constant.

Light can doppler shift as well, does that mean light isn't constant speed?

Edit: Why do all my quotes point at ASF even though it's not his quote?!

[PokerPacker]

I don't think that's exactly accurate. Refraction is not light slowing down but rather light bending at different angles based on wavelengths of colored light angleing differently.... For example if you pass a white light beam into a prism it bends into it compoenents colors. It doesn't slow down. nor does one colored light travel any faster than another color.

Why do you think it bends? Because one side slows down before the other. If you have a car and one side gets stuck in the mud, that side will slow down while the other side attempts to go the same speed. The only way for both of those events to happen are for the car to turn towards its slower side so that side has a smaller radius thus has less arc-distance to travel than the other side. Same with light. it hits the medium at an angle and the result is that part of it slows quicker than the other part, bending the light.

Light can doppler shift as well, does that mean light isn't constant speed?

Edit: Why do all my quotes point at ASF even though it's not his quote?!

light experiences a doppler shift for the same reason sound does: because of the change of distance between observer and source. Less distance means it takes a different amount of time for the light to get there. Less distance equals less time. Less time = higher frequency. JMS's explanation of sound's dopplar shift isn't entirely accurate. Sound still travels at a constant speed.

[Spec138]

light experiences a doppler shift for the same reason sound does: because of the change of distance between observer and source. Less distance means it takes a different amount of time for the light to get there. Less distance equals less time. Less time = higher frequency. JMS's explanation of sound's dopplar shift isn't entirely accurate. Sound still travels at a constant speed.

I know that light doesn't change speed, that's why I asked him that, to make this point