Would Headlights Work at Light Speed?

Would Headlights Work at Light Speed?

If you were driving at the speed of light and turned on your headlights, what would happen?
Twitter: http://www.twitter.com/tweetsauce
Instagram: http://www.instagram.com/electricpants
Sources and extras below!!

Thanks to Jude for asking me this question on twitter! https://twitter.com/stefanikj5/status/550865272895447041

“The Life of the Cosmos” by Lee Smolin: http://www.amazon.co.uk/The-Life-Cosmos-Lee-Smolin/dp/0195126645
“In Search of the Multiverse” by John Gribbin: http://www.amazon.co.uk/In-Search-Multiverse-John-Gribbin/dp/0141036117
“The Pig That Wants to be Eaten: by Julian Baggini: http://www.amazon.co.uk/The-Pig-That-Wants-Eaten/dp/1847081282

Relevant MinutePhysics videos:

light slowing down in glass: https://www.youtube.com/watch?v=FAivtXJOsiI
a different perspective from Sixty Symbols about light slowing down: https://www.youtube.com/watch?v=CiHN0ZWE5bk

Why is “c” the speed of light?


Car at light speed:


Light speed is the same in all inertial frames of reference:


Relativistic addition of velocities:


doppler shift:




Light speed and catching-up to light.



Other good relativity resources: http://newt.phys.unsw.edu.au/einsteinlight/

Light echo footage: http://www.spacetelescope.org/videos/heic0617a/

“fine-tuned” universe:


Irrational numbers: http://mathworld.wolfram.com/IrrationalNumber.html

a million digits of pi: http://www.piday.org/million/


Vsauce2: http://www.youtube.com/Vsauce2
Vsauce3: http://www.youtube.com/Vsauce3

animated drawings by Guy Larsen https://twitter.com/guylar
rocketship animation by Eric Langay https://twitter.com/ericlanglay

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20 Responses

  1. Áron Gáspár says:


  2. NormanconEVE says:

    can you call the universes under a multiverse concept… universes? Under
    the definition of a universe that would not work. Or would be just call
    them cosmos.

  3. Miguel Rodriguez Lopez says:

    That was one hell of a mind-fuck. Sorry for the expression hahahaha

  4. MrVat7 says:

    One more awesome video..Keep up Vsauce

  5. ThePettreable says:

    “Irrational Numbers” got me thinking… Will you make a video about
    Numbers? Why can you represent things with numbers and still make sence of
    things? WHY is 2 x 2=4? why do numbers add up? I mean.. Its “manmade”.. or
    at least discovered by man. I Cant come up with any numbers that didn’t add
    up because the numbers themselves couldn’t.. It’s always a case of the
    human brain making miscalculations. Or the manmade machines doing the same
    misstake as a resault of faulty coding and inperfect assembly.. Please! I
    need peace of mind! :O maybe im just stupid. I don’t know. Who would
    know?(getting too philosofical…)

  6. Disciple † says:

    In every video of yours i question my whole identity XD

  7. OemmeI says:

    But if you travel at the speed of light and point your flashlight into the
    direction you came from, will the photons move for the eyes of someone not
    moving at all? Or will the photons travel to the other direction, i.E.
    twice the speed of light?

  8. Ycylyon says:

    I find the idea of the proton having no perception of itself while still
    having an impact on reality from our point of view very intriguing.

  9. JuliusGeezer says:

    might try watching V sauce while high. would be better, its always awesome

  10. Kim André Moen Bjørkede says:

    What about getting a computer that can simulate a computer that is better
    than the computer you got. How about piracy of computers?

  11. KiddsockTV says:

    But we have to back up and ask, does a photon have mass?? We are still not
    sure about that. 

  12. me nefcanto says:

    You know what? you deserve that 8 million.

  13. Christopher Colwell says:

    Mind = blown. I still have trouble with the different speeds measuring time
    differently… I know it happens, just can’t quite wrap my mind around

  14. ActionTom says:

    Irrational numbers are bug in simulation.. maybe :D

  15. terrormike plays says:

    It’s just about the theory of relativity of einstein. Or am I wrong?

  16. Darkchylde50 says:

    Mine blown! Time is subjective based on your own speed while observing. Too
    much awesome! 

  17. Vultify says:

    mind blown

  18. Dave Bry says:

    9:20 – but in that universe you probably said something more like “the
    Earth has one sun” or “the Earth has three suns” then make a joke about the
    people in *that* universe being confused ;)

  19. Jerry Switzer says:

    #Great stuff….

  20. szpirogyra says:

    The best part after his videos is reading the comments sections…