What If Light Was Really Slow? Again. 

The way you so nonchalantly say "So I programmed this super-difficult photon path visualizer with a dynamic POV." I'm impressed.

It really hurts to see such high-quality content get so few views

I never thought that "light shockwaves" were a thing. Mainly because you need a _really_ special approach (and idea) to even got to the point where they are non-instant. I love these videos ♥

In the Discworld novels, light travels very slowly, thus sunrises are describe as golden light moving across a landscape like honey. I wonder if you could visualize that with a basic 3D landscape and a sun slowly moving across the sky while also sending out sub-sonic photons.

This is fascinating. Those low light room simulations remind me of walking about the house in the dark / at night - my eyes only catching a dull grainy, gray image.

Seeing the light bouncing making shockwaves really changed how I understand Diffuse Lighting, wow, thank you! So cool

Really cool! I implemented a similar ray tracer for my graphics class, and now I don't have to make a video about it

I would really like to see this, but also with photons behaving as if they had newtonian gravity.

That channel is CRIMINALLY and ILLEGALLY underrated. Love that video. Take care bro

Controlling light could easily be the most broken power

This is actually fascinating. Thank you for putting the time into creating this video.

Thank you for making these. This video and your last one on the topic stand unmatched quality and explanation. Your previous one sits at the top of my all time favorite physics videos.

FINALLY I feel like I understand the whole space/time relativity thing. This is a very good way of illustrating it.

Those clips at the end really show how wave-like light appears at these speeds.

Fantastic work! Excellent explanation, and the visualizer is amazing. Got yourself another subscriber.

Dude amazing video! Really good explainations

So this is how we would experience light if we were cosmic giants. Love it

You would not, in fact, get a rainbow effect from traveling through the universe close to the speed of light. Most natural light sources, including the CMB, give off a thermal spectrum, not a single frequency, so you'd see "white" light at different color temperatures.

This video was an amazing thank you. I now kinda wana simulate and play around with this stuff myself

happy new year :)) pls keep making good content

I am so happy right now that i found your channel :)

love love love this kind of content !!!!

Incredible work. Thank you.

Correction on the space vs time diagram example: The thing that cannot go below zero is the proper time, which can be defined as dT^2=dt^2-dx^2/c^2. This is the time the moving object experience when moving in your frame of reference a dx distance over a period of time t. The negative sign means the speed of light is when the proper time interval is the lowest it can go without becoming a complex number, also equivalent to light not experiencing time(even though its time component in our coordinate system is non zero). The example has the right intuition but the math is a bit misleading The simulations are really nice though. I think there is an old youtube video where they film a pulse of light passing through a water filled cola bottle irl and it looks just like the example with the teapot.

Great content. 1000 times better then TV docus nowadays... 😁

The simulated living room environment is similar to my own. I have a flatscreen on top of a credenza with large stereo speakers on the sides of the TV, integrated such that they always provide the sound. No yucky TV speaker noises. My favorite part was at the end when you were showing the light source move around, pretty neat.

Looking forward to the sound video. I've been watching a lot of videos about sound diffraction and I'd love if you took a deep dive.

Thanks for bringing back that cool song at the intro ❤❤

I've had this exact thought before and wondered what it looked like and now finally have an answer

Thanks. This was mind bending and wonderful.

I'm mulling over the shape of the buildings, and I'm not convinced they would bend away from a moving observer under continuous lighting. Gonna go through a few scenarios 1) The observer is stationery, the world is dark, and the building glows for just a moment. Since the light is slow, the observer would see the building's glow rise start at eye level and then spread up and down, but mostly up. Shape clearly not affected. Just the latency of seeing the top of the building. When it reaches the observer, the light from the base is more recent, where the light from the top is older. 2) Observer is moving towards the building, the world is dark, building emits short glow. The glow would spread similarly, but more quickly, as the later light now has less distance to travel, as the observer has moved closer since the beginning of the pulse. So, the last bit of light would still be from the top of the tower, but at an angle of incident for the observer being closer. In other words, the observer would see the base of the building earlier and at a further lateral distance than the top of the building. In this scenario the shape may seem weird if we think of the shape of the pulse, but every part of the pulse shows the angle of the building based on the observer's location. Okay so 3) Observer is stationery, the world is lit continuously, but super slow. Since the light is continuous, the observer sees all heights of the building but from different times. So at an initial distance from the building, the observer sees the base reflecting 12:00 sunlight, the second story reflecting 10:00 am sunlight, and the top of the building reflecting sunrise. The light and coloring of the building will look wildly different from our world. Last scenario 4) Same as 3 but observer is moving towards the building. Much like 2 vs 1, while the observed originating light time shifts during movement, the angle of the light observed is still dependent of the position of the observer. So the observer should see a normally shaped building, but their movement changes which time of day the see each height of the building.

I would REALLY love to see a similar simulation with gravity-affected light

3:17 this reminds me how I wrapped my head around stellar abberaruon

Did you account for the travel time from the last bounce to the camera? Objects closer to the camera should appear faster

Beautiful video!

Thankful that people like you exist

In the next video, he will start talking years after the video started. Because his sound has to reach to the microphone and turn into electrical waves. Then since light speed is slow too, electricity is way slower too. So it will take a lot of time to reach us. Then of course it will be turned into sound again through our speakers. Get ready to watch the video muted a long time before his voice reaches you XD

Commenting for the algorithm: another great video, keep up the good work :)

Keep it up until your channel blows up like a supernova!

1:17 finally someone explained it in a way I _completely_ get it. Why did no-one mention this before?

This (pun intended) illuminated some things about light for me. I especially liked the depiction of the rays bouncing!

What if light was really fast? I think that'd be cool.

Video of the year!

Damn this is a cool explanation! This'll get more views in no time 😊

Awesome Work!

As you say about the video on sound... Have you ever wonder why the sound from a far away lightning stars low in volume and then progressively gets louder instead of starting out really low in the beginning? I always asked myself that but I couldn't get an answer for it. Though I guess it has to do with the bounces in the landscape as the soundwave cross the long distance.

Dope vid!

This reminds me of that Slow Mo Guys video "Filming the Speed of Light at 10 Trillion FPS" where they used insanely short pulses of laser light to visualise light passing through a scene.

Dude i thought this video would havw line 3mil views. You've gained a subscriber

this concept would make a great cave exploration game

I saw your previous video a while back, and both that one and this one are great stuff! I just wanted to let you know (and I know English isn't your native language and that's totally fine) that the word "causality" is pronounced "koz-ael-it-ee", like "cause-ality". It's not like the word "casual" (kaz-yew-all). "Causality" isn't "casuality". Just some constructive feedback, your videos are super awesome! I was just telling my oldest daughter on our way home from her school yesterday how I'd like to do a proper high-speed motion simulation that shows what light would appear like if we could move really fast, because everything I'd seen so far either just distorted space or warped the colors, but didn't seem to capture all of the actual effects that would take place. I think you beat me to it!

Your computer is on a whole nother level

This is awesome 👏

Now do what if light was soft and fluffy and a dog

2:00 Star trek and so on are "using" the concept of a warp drive and therefore are not moving through space but moving space itself to achieve faster than light travel

This is pretty cool.

24 subs? You deserve more

Yea Changing the speed of light is literally like trying to modify the code that already works, only to find out that everything broke and now you have millions of errors and a ton of bugs that's hard to catch

Cool got me subed

Awesome!!

great video

Damn, really cool!

Really cool. I know that probably took a lot of processing power, but maybe if you could outsource the rendering to a render farm, it’d be really cool to see that simulated with higher samples, and maybe run through a denoise algorithm.

Imagine how cool that would be implemented in Cycles render engine in Blender and combine it with Open Image Denoise to get rid of the noise. Those are free and open source btw, so that's not impossible at all.

what program are you using for these renders?

3:10 Light is a wave front, and the observed would determine light direction to be othogonal to the fronts, so this part of argument (as such) does not apply. The wave fronts actually do appear tilted due to the shift in simultaneity: waves further ahead are ahead in time. Interestingly the angle is just in accordance to this photon particle explanation.

Imagine headlights being dopler boosted into gamma ray wavelengths!

Hey looks like the algorithm has decided this is in fact a good video

Nice video 👍

With the lightstrip turned off at the end, were the LEDs all turned off exactly 'at the same time' as we understand it or did you factor the, uh... Speed of light as the information coming through the strip to /tell/ each LED to turn off? If the latter, where did the 'turn off' signal first appear, at the bottom? That was a bit unclear for me, would love this additional information.

killer visuals!

RU-vid compression did not like this video

Single-source sound wave in your video? can I think of it that way?

Nice video

So amazing

I'm gonna call that trade off of spatial speed and temporal speed the luminal compass. Magnitude doesn't change, but we can change direction (kinda).

since you said in the teapot part that light can only bounce so many times as it loses energy with each bounce, would that inturn infer as it loses energy it will change wavelength and inturn change color

How does this affect transparent material? Is the index of refraction more extreme? Do total internal reflections happen at a different angle? And would the sun be able to sustain fusion with the lesser energy resulting from the lower speed of light?

what you used to render this, looks AMAZING!!!

commenting for the algorithm, great video!

It is a god tier underrated YT

Strikingly similar to coming out of a ketamine trip.

I began wondering, what would a black hole look like if instead of relying on light, we could see the atoms' position in real-time? This should make it possible to see past the event horizon! Only problem is, how could this be simulated as realistically as possible?

Brillant!

youtube compression was not kind (this was a reference to how in one scene it went 'youtube compression be kind']

This is incredible. Thank you so much... I hope this gets to the whole world! Real Eyes Realize Real Lies

How about showing the photon trajectories from less distance or bounces to more? I think it would show beautiful and smooth shapes

My question is, how can light bounce or reflect? Why is it not absorbed by all materials thus absorbed or canceled out?

Fantastic

best vid today

"I hope that wasn't too difficult to understand." My man, good lord almighty, that was perhaps the most intuitive explanation of why we can't go faster than the speed of light, that I've ever seen demonstrated. Shut up.

Congrats you did ray tracing

it is (theoretically) possible to move faster than C if you move the space around you, as space has no speed limit. I wonder what that would look like.

sick!!!!

One small nitpick - near the beginning, you said “casuality” (like a casual outfit) instead of “causality” (like cause & effect). I’ve run into that issue before too

A follow up yay 🎉

just dodge all the light like a ninja and you won't be seen

The rainbow rings are awesome. Sci-fi should get on that

Do you think you could make like a really small game out of this? Even if it's really basic?

I wonder if something actually can travel faster than light. (Ignoring all laws that prevent it, of course.) What would that look like?