Subject: Travelling very fast with headlights

From: Chen Shapira <[email-masked]>
Date: Tue, 25 Oct 2005 22:49:53 +0200

Hi Hackers,

I saw the following question in a joke site:
What happens if you are driving at the speed of light and turn on your
headlights? 

Well, I'm not sure if you can turn on the headlights when you travel at the
speed of light, but what if you travel at half the speed of light? Suppose
that you do this in vacuum.
How will the light from the headlights look to you (from inside the car)?
How will it look to someone watching you from a non-moving point outside the
car?
How will things change when you go faster and get nearer to the speed of
light?

Any ideas? Perhaps pointers to books or sites that explain the whole thing
once and for all?

Thanks,
Chen

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From: Omer Zak <[email-masked]>
Date: Tue, 25 Oct 2005 22:53:43 +0200

Of no special order:
* Special theory of relativity.
* Doppler effect.
* Only photons and other massless elementary particles can travel at the
speed of light.  Reformulate the first question in terms of c-epsilon
instead of c.

-- 
Jara Cimrman.  A name to remember.
My own blog is at http://www.livejournal.com/users/tddpirate/

My opinions, as expressed in this E-mail message, are mine alone.
They do not represent the official policy of any organization with which
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From: Arik Baratz <[email-masked]>
Date: Wed, 26 Oct 2005 00:56:08 +0200

> Any ideas? Perhaps pointers to books or sites that explain the whole thing

http://math.ucr.edu/home/baez/physics/Relativity/SR/velocity.html

The short version is that the simple formula that v=v1+v1 doesn't work
for relatavistic speeds. Use the formula in my link instead.

-- Arik

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From: guy keren <[email-masked]>
Date: Wed, 26 Oct 2005 05:05:05 +0200 (IST)

> How will the light from the headlights look to you (from inside the car)?

you won't see the light at all - because in vacuum, there is nothing to
reflect this light back to you (it is moving away from you, after all, and
faster then you move).

-- 
guy

"For world domination - press 1,
 or dial 0, and please hold, for the creator." -- nob o. dy

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From: Beni Cherniavsky <[email-masked]>
Date: Wed, 26 Oct 2005 03:08:19 +0200

On Tue, 2005-10-25 at 22:49 +0200, Chen Shapira wrote:
> [snip details]

apt-get install lightspeed
http://lightspeed.sourceforge.net/

Not exactly what you asked but this is a nice simulator of many
relativistic effects.