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Lightspeed and your headlights

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posted on Jul, 19 2004 @ 03:54 AM
I agree with Viendin and Freemason on this question.

Soothsayer, the problem is that in special relativity, the addition of velocities doesn't obey the galilean rule w = u + v, where w, u and v are vectors. In special relativity the addition of two velocities in the same direction is w = (u + v)/(1+uv/c^2). The addition of two velocities in exactly opposite directions is w = (u - v)/(1-uv/c^2). The general vector rule is a bit more complicated, but it is:
w = (u + (γ - 1)*(u.v)/v'^2*v-γv)/( γ*(1-u.v/c^2)^3, where . means the vector inner product.

posted on Jul, 19 2004 @ 04:09 AM
Look. Imagine the sun is a stationary object....It emits out light at 300,000km's sec (approximately). Now...Imagine the sun moving at the speed of light. And now imagine light being emited from the sun. Int hef orward direction light would be emiting out from the sun at 300,000km/s....but the sun is already moving in that direction at 300,000 km/s.

The speed of light is the speed of light,. Just ebcause it's ebing emitted from a moving object wont make light move any faster.

Just say the speed of light is exactly 300,000km/s
Now i have my car and am racing down the freeway at a whooping 1km/s...
The speed of light coming from my headlights wont be 300,001km/s, it will still be 300,000 km/s

posted on Jul, 19 2004 @ 05:51 PM
I understand what the others are saying, that the speed of light isn't affected by the motion of its source... with the example of the sun, light isn't traveling it's speed plus that of the speed of the sun... the speed of light is constant.

Likewise, an unmoving flashlight, its light travels the same speed as that of sun.

The speed of light, in other words, is uneffected by the speed of its source.

So, then, it does not matter what speed the car is going, for the headlights will still retain it's natural speed, constant to an unmoving source.

IE, if car is moving at the speed of light and turns on its lights, what will happen? The lights from the car will go on past the car, because its source speed is relative to the light (remember, others said it... light will travel it's speed no matter how fast the source moves).

posted on Jul, 19 2004 @ 06:12 PM
No no, you don't quite get it and I think the reason why is correct.

As you approach the speed of light, time slows down, at the speed of light time = zero.

This means that you will not have any time to have "head lights" beaming in front of you, you will have reached your destination instantly. To a person not going the speed of light, they will see just one light ray (you and your head light) but the ray of light will have different spectrums (yours being longer than the head light).

Something of that effect.

This is why I stated a conceptual example of .99 light speed.

To you the light travels light speed away from you, however, to an observer, you are going .99 the speed of light and the head light is going light speed, so the head light and you are not distancing yourselves as fast as you perceive.

This is because of time dilation.

You are going "slower" in time than the person who is stationary. So the person who is stationary is seeing you following fast behind your own head light.

You on the other hand, 1 second for you is 1 million years to that stationary observer.

So in your one second, you see the light travel as fast as light will travel in that one second if from a stationary source.

This is because the light has distanced itself from you not by 1 second, but by 1 million years compared with a stationary source.

This is why to you as the near-light speed traveller, you see the light travel the speed of light from you, even though you are nearly as fast as it.

At light speed, it does not matter because time = 0.

This is how it is different from Newtonian Physics (classical physics).

In classical physics, if you are travelling 10 miles an hour, and throw something 10 miles an hour, you see it travel from you at...10 miles an hour, not at 20 miles an hour.

However, with light, if you shine light off your car you do not see it going the speed of light minus your speed, C-100kmh for instance.

That is false, it is too fast for you to tell, but you see it going C, not C-100kmh.

The person who is not moving sees it going C.

And as I explained above this is because of "time dilation".

In a car, throwing a ball, you see it go the speed it is thrown, because you must subtract the speed at which you are "chasing it". Following it.

But if the ball were at light speed, and you were at .99 light speed, when you threw it, it would zip away from you at the speed of light. And in a few hours you would reach the destination of the ball where it stopped, only it will have been many years and you are many light years away from where you threw it?

I'm going in circles now, but does the concept make sense?


When you go .99C and you see your head light travel for a second, you see it move away for one year at the speed of light until it has gone 1 light year beyond your position. 1.0C

The stationary observer must watch your "car" chasing the head light at .99 speed of light, for a million years to see that same year of travel that you observe...but in that million years, the light of the head light, and your "car" will be exactly 1 light year apart in distance.

The miracle of time dilation.

1 million years and 1 year are incorrect approximations, the accurate comparison in time can be determined with the time dilation formula, which is in the 20th post given in this thread.

*EDIT* The time dilation formula is not given in the 20th post, it can be derived from it however, I have forgotten the formula off hand but I believe it is something like:

T = (1-(v/c)) Where T = time; v = velocity of observer; c = velocity of light.

I think that is the formula, though I think there is a square root going on or something, but basically, when you approach the speed of light time aproaches zero.

I would like someone well grounded in physics to determine whether or not this concept is accurate, half-accurate, or off-base.

[edit on 19-7-2004 by FreeMason]

posted on Jul, 20 2004 @ 01:34 AM
Freemason, the time dilation formula it t'=t*sqrt(1-v^2/c^2). 1 year at 0.99c for a stationary observer is about 0.141 year for the person moving.

posted on Jul, 20 2004 @ 07:45 AM
You would see the light coming out of your headlights at the speed of light. Observers outside the ship would see the light coming out of your headlights, at the speed of light. That might sound impossible, but according to relativity it is not. You know the speed and the distance. It is impossible for the speed to be the same for both the observer outside and inside the ship, unless either the distance or the time have changed. Light travels the same distance over time to all observers. Time cannot be the same for both observers if this happens.

That is kind of a rough, not so accurate look at it, but it gives you a good idea. I know probably 75 people gave this same description already. I just wanted to through my veiw of it out there.

posted on Jul, 21 2004 @ 02:20 AM
What about the Dopler effect? what if light speeds up when your traveling at light speed, and your in the future of light? would that light be altraviolet light? what if faster then that? would it be neon light?

or what if

it goes backwards, if your traveling at a speed of light with your lights on, would the headlights lights became a negative value? this resulting a Micro wave? or night vision? Im think of the Dopler effect is at play here.

posted on Jul, 21 2004 @ 03:39 AM

Originally posted by MDB101
What about the Dopler effect? what if light speeds up when your traveling at light speed, and your in the future of light? would that light be altraviolet light? what if faster then that? would it be neon light?

For the person travelling there is no doppler shift, because in his reference frame, he is not moving and the light is simply moving at c like it always does. If he couldn't see his surroundings, it would be impossible for him to figure out at what speed he was moving, according to relativity. If there was doppler shift in his reference frame, there is a preferred reference frame.

There is doppler shift, however, in our reference where he moves at 0.99c or even 1c. The formula of relativistic doppler shift is f = f0*sqrt( (1+ v/c*cos α
/(1 - v/c*cos α
) (source), where f is the shifted frequency, f0 the original frequency and alpha the amount of degrees between the velocity vector at the moment the light is released and the vector than connects the sender and the observer at the moment the light is released. v is positive if the sender is approaching. Now, to see the headlights, we have to be exactly in front of the sender, so alpha is 0: f = f0*sqrt( (1+ v/c)/(1 - v/c) ).

If the frequency is 5*10^14 Hz, which is orange light, with the sender moving at 0.99c relative towards the observer, the observer sees light with a frequency of 5*10^14*sqrt( (1+ 0.99)/(1 - 0.99) ) = 7,05*10^15, which is ultraviolet. At c, the equation breaks down and the light has infinite frequency.

posted on Jul, 25 2004 @ 10:36 PM
This isnt the same topic, but has to do with this topic, here it goes..

I was watching something on the discovery channel and an astronomer (whatever) said in the center of the milky way there is a group (or was a long time ago when the light we are seeing now left them) of stars swirling around at 3 million miles an hour.

I just thought Id say this because I read a post in this thread that said nothing can go faster than the speed of light.

posted on Jul, 25 2004 @ 10:41 PM
Nothing would happen. If you traveled at 50% lightspeed and turned on your headlights, you will see the headlights go at lightspeed. People on the ground would ALSO see the headlights go at lightspeed. That is the strange thing about light. The speed of light is the same no matter how fast you are traveling. It is absolute.

posted on Jul, 26 2004 @ 05:34 PM
3 million miles an hour is only 833.3 miles a second. Far from light speed which travels at 186,000 miles a second.

Now around super massive blackholes they have detected objects moving so close to the speed of light that the only possible way these groups of iron and other heavy elements could do so is if the space-fabric was being "pulled in" as a whirl-pool the fabric being water.


posted on Aug, 9 2004 @ 06:26 PM
I'd prefer watching it from a whole other perspective.
I'm talking about the direction time changes. I don't think that a second for you is a million years for an observer, i rather think that if you travel @ near-lightspeed, one second for an observer seems a million years for you... (not that much, maybe a dozen). Beacause, the way a photon sees the world, there is no time, just space (when time stops, time changes into space, much like the matrix effect). So if you travel at lightspeed, you don't travel thru time, but with time.

Someone talked about the infinite amount of energy needed to achieve near-lightspeed. Maybe you could equip a space engine with the necessary fuel, what about the human body? blood-circulation ? your blood will have to move faster than your body in order to be pumped back to your head. a human heart does not function with antimatter, so it will never have the energy to do so, so you would die long before you even approached light-speed.

As for the headlights, an observer wouldn't see a thing, you're moving far too fast, and the light you would simply be at light speed. many people try to see light as simple particles who have the same physic laws as any other object we know ( a baseball ? ). Big mistake, light is something..special, and doesn't obey any of the normal physic laws you know (an example? try to emprison light, put it in a box with mirrors). in some cases, light acts like particles (i.e. water) , in others like a wave (i.e. sound). so is it both or something else?

posted on Aug, 9 2004 @ 09:50 PM
I have asked this question all my life! An answer? I dont have one but have managed to puzzle quite a few people with this unanswerable question. Heres anoter one for you. If you put instant coffee in a microwave, would you go back in time? OR If you flush a toliet nort of the equator it spins clockwise, and counterclockwise south of the equator. So if you were on a ship that was sitting on the equator what would happen? Stuff that makes you scratch your head

posted on Aug, 9 2004 @ 10:17 PM

Originally posted by jrod8900

Still stumped on what would happen if you shone a light through the rear of the craft.

[edit on 18-7-2004 by jrod8900]

i think if you shown the lights from the back you would see a stream of light......its too hard for me to explain but i can think it in my see the stream because the headlights keeps emitting light............and the light is moving away from the ship.........ehhh whatever

maybe the water wont spin and just get sucked in by the toilet.......and it doesnt have to be a ship it can be a house right on the eqautor

[edit on 9-8-2004 by CookieMonster000]

posted on Aug, 13 2004 @ 09:48 PM
I posted the same question in another forum and I found this answer to be most plausible. Strangely its very simplistic.

The spacecraft cannot accelerate to the speed of light (c=300000000m/s). However, the lights would work in a normal fashion. Strangely enough, light always travels at speed c by any observer, no matter how fast they are moving. What differs is how fast they pass through time. So, if both spacecrafts are moving in opposite directions, one towards the sun and one away, BOTH observe the light to pass them at 300000000 meters per second, and both observe the light from the others' headlights to travel at the same speed. Light is also bent by gravitational fields. This is relativity.

posted on Aug, 15 2004 @ 06:58 AM
Ok....firstly what a cool example.....this isn't A question,this i think is THE question. Don't you just love how, like with Religious leaders, those at the forefront of thier field in science hang all thier hopes on a few facts to support a whole load of theories. See theories are a little like religion any dumb ass can come up with one, and to some extent PROVE it.....I liken these theories to my view on the 'Bible'.....SHOW me...CONVINCE me...when i see that your theory becomes FACT then i'll shut up with mine...or vice versa.....That said, its good to see so many people thinking about this really is a 'Headsplitter'.....I remember asking my Physics teacher the same question......the comments in class went on for the duration that we were there, approx 3 years.....and something that has stuck with me teacher a Dr Slater said something very bemusing about the books we were using, he said "let them guide you, but never forget they are not your master, because when we stop questioning one another, science will mean nothing".......And my own theory....'Course theres something faster than light......we just ain't found it yet'.

posted on Aug, 16 2004 @ 05:20 PM
In this month's Discover magazine (dedicated to Einstein), that Einstein had asked a similiar question, one that sounds rather interesting...

"What would you see in a mirror if you were traveling at the speed of light?"

Also, there are currently tests being preformed to see wether or not the speed of light is constant... there are plans to launch a satelite in 2007 to test this. Apparently, since gravity can effect the flow of light, they reason the speed should also be altered...

posted on Aug, 16 2004 @ 05:59 PM
I understand it can be confusing to many.

My 3 cents:

a) please read one of the previous posts which has the formula for the velocity transformation when changing reference frames. That's how our space-time works. Period.

b) it's pretty safe to assume that you can't travel faster than the speed of light

c) as somebody said, no matter what reference frame, light will be observed as traveling at same speed


posted on Aug, 17 2004 @ 10:54 PM
I signed in just for this topic.

Light does not have any mass to it so that means that "Light Speed" is simply that. Light travels no slower or faster then "Light Speed."

A stationary person would see the light at the same moment the vehicle traveling at "Light Speed" would pass. Because there is no mass to a photon, the example of throwing a ball from a moving car will not work to be in a relation.

The idea of the light "building up" is a possibility, I have no idea what affect photons will have in this instance. I would assume that the source would continue to produce photons and continue to build up energy in that area of the source.
Light shown behind a vehicle traveling at the speed of light would most likely also appear as a flash. For a human to see light it must be focused and reflect at different energy amounts thus becoming a color and intensity that we see. A vehicle traveling at "Light Speed" would pass and you would see the initial energy of the photons but would dissipate so fast that I do think that the light would be seen as a flash as the vehicle moves by.

The person that says that light speed = 0 time can not be more wrong. If that was true, light would instantly be seen when the source was turned on. Example: Light takes about 1 hour to reach Saturn from the Sun. Light speed is a measurable distance over a particular amount of time.

Sure, It has been proven that objects moving faster do travel slower in time, but why do so many people feel that "Light Speed" is the limit to absolute speed?

posted on Aug, 17 2004 @ 11:41 PM

Originally posted by DrpKeeGTZ

Sure, It has been proven that objects moving faster do travel slower in time, but why do so many people feel that "Light Speed" is the limit to absolute speed?

Light is visible. Light speed, is comprehendable. Anything faster just lies within the realm of imagination.

Originally posted by amantine

The speed of light is only the limit for objects and information. Space can expand faster than the speed of light because it is not an object and doesn't transfer information faster than the speed of light.

That makes sense because of E=mc^2

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