# If you're in a vehicle going the speed of light, what happens when you turn on the he **URL:** \ **Category:** Factual Questions\ **Created:** [February 26, 2006, 6:52am UTC](https://boards.straightdope.com/t/if-youre-in-a-vehicle-going-the-speed-of-light-what-happens-when-you-turn-on-the-he/346161 "2006-02-26T06:52:21Z")\ **Posts on this page:** 5\ **Page:** 2
**Author:** ![rbroome](https://avatars.discourse-cdn.com/v4/letter/r/838e76/32.png) [@rbroome](https://boards.straightdope.com/u/rbroome)\ **Post date:** [February 28, 2006, 2:12am UTC](https://boards.straightdope.com/t/if-youre-in-a-vehicle-going-the-speed-of-light-what-happens-when-you-turn-on-the-he/346161/21 "2006-02-28T02:12:02Z")
> [@Stranger On A Train](#): > > Your logic is impeccible. 😉 > > As for the OP’s question, let’s provide a more illustrative…er, illustration. Okay, so anyway, as various people have noted, no material object can equal or exceed the speed of light; if it did, it would become a supermassive singularity onto which the rest of the universe would crush. The benefit, of course, is that it would make the question posed to be a moot one (plus it would take care of the “security situation” which has caused me to be at work on a loverly Sunday afternoon), but since that interferes with my lunch plans we won’t go there, at least not until I’ve had a couple of beers. > > So you’re in a car going, let us say, 99% of **c** (the accepted symbol for speed of light.) Owing to vB code’s inability to cope with simple symbols or LaTex coding I’m just going to refer you to this site for the equations on [Lorentz contraction](http://ffden-2.phys.uaf.edu/212_fall2003.web.dir/Eddie_Trochim/Lorentztransform.htm), but suffice it to say that weird things happen when you are moving at this velocity–even weirder than the things that happen in a David Lynch movie, though typically with less blood. [Here](http://www.adamauton.com/warp/)’s a simulator that will show you the magnificent weirdness of what occurs. > > Anyway, getting away from the math, here’s what happens: When you’re moving faster (relative to another locus…let us say a photon emitted by your supercharged spacecar) time compresses, as do lengths (in your direction of motion), while lengths behind you stretch out. So the light in front of you (and behind you, and beside you) all appears to be moving at **c** , but the rest of the universe is aging rapidly. From an “objective” POV–someone “at rest” relative to you and your photons–you are aging very slowly, and the dash clock is counting seconds as if they are eons. The faster you go, the worse it gets, until your great-great-great-great-great-great-great-great-great-great grandchildren are having kids who don’t even look vaguely like you and sure as hell aren’t going to visit you at the hospital after you slam into a mislaid asteroid. > > So, if light appears to be moving the same speed regardless of the relative velocity of the observer…WTF? You have to account for differential energies (that is to say, the difference in momentum between an observer chasing his headlights and one content to let them fly away in front of him). How do you cope with this conundrum? You do it by accepting a change in the frequency (or reciprical wavelength) of light; when moving at relativistic speeds the light in front of you becomes (from your POV) a higher frequency, or “blueshifts”. Go fast enough and even visible light will shift into gamma ray range, which would be bad for you unless you are a cartoon superhero. The light behind you becomes “redshifted”; i.e. lower frequency (or longer wavelength), until it redshifts below visible, infrared, radio, and into invisibility. Light to the side makes a starbow, a spectrum of visible colors. That should keep the kids quietly entertained for at least a few minutes. > > If you could somehow manage to achieve **c** the movement of time, from your POV, would stop; you’d be unable to differentiate between tomorrow and next century. You couldn’t slow down (how’d you measure time rate of change without time?), and of course, you can’t speed up. A photon, like Paris Hilton, has no sense of its past, future, or surroundings; everything in its lifespan occurs as one long, drug-hazed blur between inception and terminus. In a sense, all particles are moving at **c** , but most devote their velocity along the time axis (which is a one-way street AFAWK), while photons move exclusively through space and only shift “sideways” by varying frequency. > > Trippy shit, eh? Now, let’s go catch _2001_ down at the Arclight, and lie down underneath the screen during the wormhole sequence. I think, with the assistance of a couple ounces of Jamacan Gold, that I might just be able to figure it all out this time. > > Stranger I can’t add much to Stranger’s excellent reply, especially the part about 2001, but I can point out yet another strange effect. As I understand it, as your speed increases, incoming light begins to bend. At speeds near c, you start to see around corners. Of course, not for long, but for a brief moment, you see both the front and sides of an object as you zoom past. Lots of strange things happen. Personally, I suggest just turning on the warp engine and jumping into subspace. Captain Kirk assures me everything works just fine there. 😃 ---
**Author:** ![Man\_With\_a\_Cat](https://avatars.discourse-cdn.com/v4/letter/m/cab0a1/32.png) [@Man\_With\_a\_Cat](https://boards.straightdope.com/u/Man_With_a_Cat)\ **Post date:** [February 28, 2006, 2:47am UTC](https://boards.straightdope.com/t/if-youre-in-a-vehicle-going-the-speed-of-light-what-happens-when-you-turn-on-the-he/346161/22 "2006-02-28T02:47:43Z")
> [@Otanx](#): > > Forget the headlights. You are missing the important question here. What happens when I turn on the windshield wipers. Which leads to another question. What the $%\* am I doing driving that fast in the rain? > > -Otanx Hopefully not tailgating, because your stopping distance suffers in the rain. ---
**Author:** ![VernWinterbottom](https://avatars.discourse-cdn.com/v4/letter/v/c67d28/32.png) [@VernWinterbottom](https://boards.straightdope.com/u/VernWinterbottom)\ **Post date:** [February 28, 2006, 3:10am UTC](https://boards.straightdope.com/t/if-youre-in-a-vehicle-going-the-speed-of-light-what-happens-when-you-turn-on-the-he/346161/23 "2006-02-28T03:10:03Z")
> [@littlegoetjen](#): > > If you’re in a vehicle going the speed of light, what happens when you turn on the headlights? It depends on whether or not you’re on a treadmill/conveyer belt. ---
**Author:** ![Rhubarb](https://avatars.discourse-cdn.com/v4/letter/r/59ef9b/32.png) [@Rhubarb](https://boards.straightdope.com/u/Rhubarb)\ **Post date:** [February 28, 2006, 4:14am UTC](https://boards.straightdope.com/t/if-youre-in-a-vehicle-going-the-speed-of-light-what-happens-when-you-turn-on-the-he/346161/24 "2006-02-28T04:14:20Z")
> [@Stranger On A Train](#): > > Trippy shit, eh? Now, let’s go catch 2001 down at the Arclight, and lie down underneath the screen during the wormhole sequence. I think, with the assistance of a couple ounces of Jamacan Gold, that I might just be able to figure it all out this time. Never mind the headlights, does the _ **cigarette lighter** _ still work? ---
**Author:** ![Stranger\_On\_A\_Train](https://avatars.discourse-cdn.com/v4/letter/s/13edae/32.png) [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)\ **Post date:** [February 28, 2006, 11:00pm UTC](https://boards.straightdope.com/t/if-youre-in-a-vehicle-going-the-speed-of-light-what-happens-when-you-turn-on-the-he/346161/25 "2006-02-28T23:00:00Z")
> [@Ring](#): > > No that’s not true. Velocity, no matter how high, has nothing to do with creating gravitating mass or the formation of a black hole. (This is one of the main reasons physicists dislike the concept of relativistic mass- it causes too much confusion.) You’re absolutely correct, and I should have known better, even for a toss-off comment. Clearly I need to review my relativistic physics. Hmm…I wonder if there’s some way I can wedge that into my increasingly diverse job description; “Examination of general relativistic effects upon sub-orbital boost-flight parameters…” It’s a hard sell, but if ABL can get a pass for so long, then surely I can convince someone of the necessity of this. > [@Ring](#): > > Gravitomagnetism is the only gravitational effect due to velocity (momentum). [Here](http://www.arxiv.org/PS_cache/gr-qc/pdf/0311/0311030.pdf)’s a primer (warning: PDF) on gravitoelectromagnetism, though owing to my aversion to E&M (difficult subject, terrible instructor) I can’t claim to follow the details. I should really sit down and work through the topic, though; it looks like fun, if not slightly painful, stuff. Stranger [Previous page](https://boards.straightdope.com/t/if-youre-in-a-vehicle-going-the-speed-of-light-what-happens-when-you-turn-on-the-he/346161.md?page=1)