Challenge on Special Relativity

Beja

Beja

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A car is travelling towards point B with the speed of light. The driver turns the lights on.. Which one arrives @ point B first, the car or the light?
 
I try:
They arrive together at the same time.
 
Turning on the lights is not possible because car and driver are pure energy, driving at speed of light.
 
The time that turns on the light has already arrived, the hand is slow.
 
It depends on how far is point B at the time the experiment begins.
If it's closer than speed_of_light * time_needed-to_turn_on_lights, the car arrives first
If it's equal or farther than formula above they arrive together
 
udg said:
If it's closer than speed_of_light * time_needed-to_turn_on_lights, the car arrives first
Click to expand...

Since it is all an unrealistic assumption, let us suppose also that the time spent to turn the lights on is equal to zero; despite this, the car would arrive first, because the light from the headlights, before reaching the maximum speed, will have to start from zero and accelerate, even if it did so in billionths of a second.


[However I walk, so I don't care at all :p]
 
LucaMs said:
because the light from the headlights, before reaching the maximum speed, will have to start from zero and accelerate
Click to expand...
Not so. I believe that photons, being mass-less, always travel at the speed of light of whatever material they are traveling in and cannot travel slower than this.
 
Last edited:
Light doesn't accelerate. It always moves at the "speed of light" (c).

Not 100% accurate but the interesting thing about the light speed is that it is constant and is not affected by relative movement. Two observers moving in different directions will measure the same speed.
Instead of the velocity being changed based on the observers movement, the time changes between them (based on the simple S = V * T formula).
This is all that I remember from my Physics II course...
 
Beja said:
A car is travelling towards point B with the speed of light. The driver turns the lights on.. Which one arrives @ point B first, the car or the light?
Click to expand...
Both at the same time. The speed of light is the maximum speed. Well ..... for now.
 
This Is almost the same as another situation:
A fly enter a train. The train during its voyage achieves a top speed of 300km/h... The fly has a top speed of 2500m/h...
What's the actual speed of the fly?...
The question is "incomplete", as we can give at least 2 answers, both right and wrong at the same time...
Absolute ground speed will always be 2500m/h, however, relative speed to ground would then the the sum of the two...
Same applies to the car... The headlight light will always arrive before the car, if of "finishing line point of view"
 
The answer depends on where the observer is.. If it's the driver then he will see the light velocity is C (speed of light) and the light will arrive before his car. But if the observer is watching outside the car then he will see both, the car and the light travelling with the same velocity. And guess what! Both observers are correct!
 
I would like to "observe" your brain, Beja

(I'm kidding, you know, I respect you!

Both statements are correct!
 
If they put their headlights on then it it's safe to assume their rear lights would also come on.

Would their rear light leave a trail of red light as the light would be in effect stationary?
 
we see everything because of light
if everything is moving at the speed of light
then relatively everything is standing still
so nobody or thing gets anywhere
and everything is going nowhere
after all light is a reflective property
so the car and the headlights are going the other way

that's all I remember from my Fine Art course with einstein

Oh the headlights never come on : they're going at the car's speed.....o_O
 
LucaMs said:
Since it is all an unrealistic assumption, let us suppose also that the time spent to turn the lights on is equal to zero; despite this, the car would arrive first, because the light from the headlights, before reaching the maximum speed, will have to start from zero and accelerate, even if it did so in billionths of a second.


[However I walk, so I don't care at all :p]
Click to expand...
Sorry but light does not accelerate. It's always traveling at the speed of light.

(Studied physics at university)
 
Cableguy said:
A fly enter a train. The train during its voyage achieves a top speed of 300km/h... The fly has a top speed of 2500m/h...
Click to expand...

yes, but then, why doesn't the fly go SPLATT on the windscreen?

Ohm :oops: that's a new question, I should have started a new thread ..............:D
 
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