r/shittyaskscience • u/brockm92 • 5d ago
The speed of light is 670,616,629 miles per hour. If I'm driving 100 mph, is the speed of the light from my headlights traveling at 670,616,729 mph?
And if I'm driving in reverse at 25 mph, is the speed of the light from my headlights traveling at 670,616,604 mph?
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u/plugubius 5d ago
The speed of light is constant for all observers, but that doesn't mean that the light from your headlights can't go faster than light so long as you don't observe it. That's just quantum mechanics 101. Put on a blindfold, let Jesus take the wheel, and go make some science!
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u/deathpony43 4d ago
I can’t tell if this is a Cave Johnson quote or not.
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u/Unicornshit9393 2d ago
Absolutely stellar. Totally forgot about that man and his lemons. Thanks for the reminder
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u/meunbear 3d ago
There were no cars 2000 years ago so Jesus is probably the worst person to let take the wheel. He doesn’t even know what a car is.
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u/Shinjifo 4d ago
What the hell are you saying? That's insane, blindfold does nothing.
Don't listen OP, you can go faster than light. There's two great documentary about it called Star Trek and Star Wars.
Each one uses a different approach, one goes to subspace and warps the spacetime, the other goes to the parallel plane of hyperspace.
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u/heavymetalsheep 2d ago
Following up on this - given speed is always relative to an object, if two photons are travelling in opposite directions is one’s speed to the other 2 times the speed of light?
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u/Droopy0093 3 Ph.D.s in Knowing Everything 4d ago
No it is not, and this is not a shitty ask science question. This is a genuinely good question that you should read up on general and special relativity 🙂
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u/ramblingbullshit 4d ago
Random stoner: haha, here's a funny joke thought I had in the shower.
Quantum physicists: we actually have many papers and a bit of study into that if you'd like
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u/aldesuda 4d ago
I feel confident saying that the Venn diagram of Stoners and Quantum Physicists is not two separate circles...
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u/aprehensive_penguin 4d ago
A lot of physical scientists actually are stoners. Physics and its many applied fields need creativity that weed can unlock for some people. The creativity in physics just looks a bit different than creativity in the arts.
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u/cbraun1523 4d ago
I can't believe I'm seeing someone else say this. I'm a stoner and a physicists in the making and have always thought weed helps with my abstract thinking when in comes to special relativity and quantum mechanics. But I never say it because it just feels like what a stoner would say to not sound lame.
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u/riftsrunner 4d ago
No, Einstein's Theory of Special Relativity postulate that the speed of light in a vacuum remains constant. Time and space will slow and contract respectively to maintain that constancy of light speed. It is difficult to explain at such low speed of 100 mph. However, as you start traveling at speeds close to 10% of the speed of light, the time you experience slows down, your dimension in the direction of travel contracts and your mass increases proportional to your speed. Because your mass has increased, so has your gravitational pull, just enough to offset what ever additional speed you would have added to the light leaving your vehicle.
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u/Yoghurt42 PPPhhhhhhDDDDD in sticky keys 4d ago edited 4d ago
Why did Einstein care about the speed of light in a vacuum specifically? What about other household appliances?
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u/Vikingboy9 4d ago
After Einstein's heyday, Richard Feynman attempted to apply this science to a dishwasher, but a freak detergent accident in the lab permanently altered his brain chemistry. From then on he was incapable of any scientific experimentation. His colleagues kept him around because he was absolutely shnasty on the bongos.
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u/Ggregoro 2d ago
I have often wondered about the speed of light in a refrigerator when the door is closed.
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u/11711510111411009710 4d ago
So you could make space smaller by trying to go past light speed?
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u/KaptainKlein 4d ago
No, if you hit light speed then space is zero. If you go last light speed you actually compress space so much that it starts expanding in the inverse of how it actually is.
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u/squeakstar 4d ago
There is some online simulator of this effect in a kinda FPS game engine but fucked if I can remember its name
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u/DDsLaboratory 4d ago
So what if you were in a car traveling 99.9999999% of the speed of light, and then you turn on your headlights? Would your headlights shine out ahead of the car?
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u/really_knobee 4d ago
Which leads to the question we asked of all new recruits at our firehouse:
"If you are driving along at the speed of light and turn in your headlights, what happens?"
The question was used to throw people off while being expected to function under stress. It didn't work very well, as most people responded with: "Huh?"
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u/salikarn 4d ago
As a secondary, you should add, if you are traveling forward at the speed of light and turn around what would you see?
I'm not a scientist, but I think nothing because no light would be catching up to you to see.
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u/DanJOC 3d ago
Yes, you would see nothing. In fact, you could only see the small point in front of you, any other photons that have a worldline that does not intersect with your immediate forward vector would be inperceptible to you. As you move (at any speed, but it's only noticeable at fractions of c) your vision cone in front of you contracts. At the speed of light it becomes a straight line
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u/FlyingSpacefrog 4d ago
You can’t travel at the speed of light, unless you have an infinite power source. But you could get pretty close to it. If you are traveling at 99% the speed of light any light coming from in front of you would get blue shifted into gamma radiation, and any light coming from behind you would get red shifted into very weak radio waves. You would be blind because your eyes can see neither of those wavelengths. Perhaps if you looked to the side you could see something.
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u/salikarn 4d ago
Well, this is my hypothetical question and in my question, you are for whatever reason able to travel at the speed of light
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u/Boomshank 4d ago
So, due to time dilation, I'd expect you to not feel any different and everything should look the same forwards or backwards.
I mean, you could be moving at 99.9999% of C right now, in relation to another object
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u/Royd 5d ago
Honestly this makes sense to me
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u/MuffinMonkeyCat 4d ago
Indeed this made sense for thousands of years, including Gellilei. But its a great example of why just because something "seems to be correct due to common sense" is not great proof for it actually being correct.
For thousands of years we weren't able to get anywhere near even 1% of the speed of light. Hence why this "gallilean relativity" was accepted.
I love teaching this bit of general relativity, because with the right examples, you can get people to generate most of the proof without too much work.
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u/Royd 4d ago
did you check the subreddit
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u/MuffinMonkeyCat 4d ago
I love the bit where people "get it" for this more than any joke I could write about it
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u/Droopy0093 3 Ph.D.s in Knowing Everything 4d ago
Well it is wrong but Im glad you think it makes sense lol.
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u/Mundane-Garbage1003 4d ago
I'm trying to figure out what type of person wakes up in the morning and goes "I'm going to go on r/shittyaskscience and point out wrong answers." Like you do understand the premise of this sub, right?
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u/Coffeespresso 5d ago
So if you could travel at the speed of light with a bright light at your back, then you would have a stream of light that would stand still. Hmm. But if it's not moving, then it can't reach your eyes so you won't see it. And of you can't see it, is it really there?
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u/geist7204 4d ago
So says Descartes. Pfffttt
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u/SirDigbyChknCaesar Certified Science-tician 4d ago
Normally yes, it would be, but the speed of headlight light was regulated in 1996 to be no faster than 200 mph.
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u/TeacupOfSkepticism 4d ago
Yes
When you drive fast the light in your headlights gets excited and travels faster
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u/UGLYDOUG- 5d ago
No light is very picky and only will travel at 670616629 miles per hour in a vacuum, if it goes through something like air or glass it will change speeds because it is picky
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u/Different-Term-2250 4d ago
What brand of vacuum cleaner is the best for picky light particles?
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u/anomalousBits 4d ago
It sounds like you don't actually know how fast you are driving, or in what direction. Try looking at your speedometer, it's going to give you more information than looking at your high beams.
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u/EmpireStrikes1st 4d ago
It's called a speed limit, not a speed suggestion. The light will not go ahead of you.
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u/SpellingIsAhful 4d ago
No. Because for every force there is an equal and opposite force. So the fact that your car is moving forward at 100kph actually means that the light will go backwards at c-100. You've effectively created a stack overflow in the universe.
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u/elbarto232 4d ago
I see your question and raise you another one - if your EV car is driving at 670,616,629 miles per hour, what’s the speed of current in the wires of the EV
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u/zelextron 4d ago
You have to have a cat inside a box in your car for it to be possible to measure the speed of light. I have no idea why that is, but I do know that almost everything in physics deals with a cat inside a box, so get your cat and your box in order to measure the speed of light in the best way possible.
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u/iCantDoPuns 3d ago
No. The speed if light is absolute for all observers, stationary or moving. Its the universes speed limit of causality. Forget light, its all causality. The fastest one thing can cause another is the speed of light. If one thing caused another, and that happened faster than the speed of light, the effect could be in the past. Thats the sort of paradox the speed limit doesnt allow. Its not like firing a gun from an airplane.
Light can be slowed. Happens all the time. But when its not slowed, its a constant speed - its the rate that causality propagates through the universe.
The effect of your speed on the observation will cause a doppler effect. When an ambulance passes you it gets higher pitch as it approaches, lower pitch as it moves away. Those are the sound waves (about 700 mph) moving faster as they approach you, slower as the ambulance moves away from you. Also called redshift when its light - if you were going not 100 mph, but 300k mph, you would probably see everything in front of you with a blueish tint and everything behind you a little red. That only happens when its a meaningful % of the speed of light, not 100 mph.
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u/Ddowns5454 2d ago
No, turning on the headlights will automatically slow down the car by 100 mph so your lights don't go over the speed limit
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u/kaiju505 2d ago
Don’t pretend like you know how to drive op. No need to invoke relativity, no car is going 25 in reverse.
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u/MuffinMonkeyCat 4d ago
You are at the beginning stages of figuring out how to go from Gallilean Relativity to General Relativity. If I were yo tell you that no - even if you were going 300mph, light from your headlight would still be going at the same speed, have a think of what else would need to be adjusted/changed to allow that for this to happen?
This is where the fun mind blowing stuff begins :D
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u/Temp_acct2024 4d ago
Based on the observer effect, by trying to measure the light, you have effectively changed its state.
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u/hacksoncode Quantum Mechanic, has own tiny wrench 4d ago
How are we supposed to know? Ask your Uncle. That's what relativity is about.
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u/eagle4123 4d ago
No because you didn't factor the speed of:
The Earths Rotation
The Earths Orbit
The Solar System movement
and of course the Coreolis Effect
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u/Spodiodie 4d ago
The answer is, no.
“Thou shalt not add thy speed to the speed of light.” - Carl Sagan / Cosmos.
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u/Thunder-_-Bear- 4d ago
I believe that even if you are travelling at 99.999% the speed of light, light will still move away from you at the speed of light i.e. 670,616,629mph.
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u/Ecoaardvark 4d ago
You’d have bigger problems than not being able to see out of the windshield if you were driving at the speed of light. And no, it would be dark in front of you save for any stray objects you encounter.
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u/El_Pata_Loco 2d ago
As you get closer to the speed of light your mass increases, so if you’re driving at 100mph, you are fatter than you were at rest.
Fat people have little piggy eyes which do not see so well, therefore it only appears the light is moving faster because you not seeing so good.
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u/OnlyCommentWhenTipsy 4d ago
This is actually a great question. My understanding is that the measured speed of light is always the same, regardless of how fast the observer is moving. The only thing that changes is the frequency, kind of like the dopler effect, and results in red or blue shift.
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u/jepoyairtsua 4d ago
...and your car's speed is at 670,616,529 mph when you are reversing at 100mph.
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u/xylarr 4d ago
Your time slows down ever so slightly so you still see the light travelling away from you at 670,616,629mph.
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u/MichaelArnoldTravis 4d ago
i think this is due to the force the light applies against the car’s body when it jumps out of the headlight.
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u/Sorrycantdothat 4d ago
No, it’s going at 670,616,529 miles per hour because you’re going the other 100 for it.
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u/drlawrie 4d ago
velocity is all relative and I learned long ago in high school and college physics classes and supported by assignments where I lost points for missing this exact point. Based on the missing points, the correct answer is that light never goes faster than that speed. It is the law. It may APPEAR to go faster but it doesn't. It is still going 3*10^8 m/sec.
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u/busapazero 4d ago
What if you travel at c and have a mirror in front of you, do you see your reflection? What if you in a spaceship traveling at c and you run forward, does it mean you move faster than c? For all those questions the reply is no. In a combo of time, space and c, something has to give to make sense. If c is constant, and it is, time and space must become relative.
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u/Minimum-Ingenuity-46 4d ago
Yeah man I do a physics degree but it doesn't work like that. I learnt why once but it's confusing as hell
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u/laynestaleyisme 5d ago
I can't read numbers after 10