Seeing the Invisible: SLOW MOTION Schlieren Imaging

Seeing the Invisible: SLOW MOTION Schlieren Imaging


If there were a portal through which you could see all of the invisible air currents, temperature gradients and differences in pressure and composition of air, then this is what it would look like to strike a match. This is helium being squeezed out of a balloon. You could see the warm air rising off your hands. The invisible vapors of isopropyl alcohol and a plume of ejected material when you sneeze. This is the setup for how I made those shots over here I have a 40 centimeter diameter concave parabolic mirror normally this would be used to make a telescope but if it form, just a tiny piece of a big spherical shell Right? A giant spherical mirror that we’re inside then the center of that mirror would be right here And that’s where I’ve placed this led it’s three millimeter But I try to make the light source even smaller by painting it with some black nail polish so, we try to approximate a point source of light there now that light spreads out in all directions, and it bounces off the mirror and reflects back Almost to exactly the point where the light is you can see that the light converges to a point right there Now I’ve offset the light just a little bit so that this light will pass straight through and into the lens of my camera So right here, I position this razor blade, so it cuts off about half the light passing through This setup allows you to see tiny variations in what is in front of the mirror For example when you have hot gases coming off of a candle Well, you can see that because as the reflected light from the led Passes through this column of hot air, it changes directions ever so slightly that is it refracts and the reason for that is because the Refractive index of hot air is different from the refractive index of the cooler air Around it now refractive index is a measure of how fast light travels through a medium Relative to its speed in a vacuum So for air the value is pretty close to 1 but hotter air actually has a lower index of refraction in this case the difference in refractive index is incredibly tiny and so we don’t notice the deflection of the light but with this setup It actually makes a difference because some of the light that would have passed over this razor blade Instead gets deflected down and gets blocked and that forms a darker spot on the image Similarly some light that would have hit the razor blade is instead deflected over it creating a brighter spot on the image and that is how this works, so you can see the heat rising off your head and You can see your breath And you can see the cold air poured out of [a] cup of ice But temperature is not the only thing that affects the refractive index different materials [different] substances They have different refractive indices for example the butane in a lighter obviously we can’t see that It’s coming out right now, but the camera can even before the lighter is lit light also refracts when it passes through a bubble and the amount depends on the thickness of that bubble film This technique is known as Schlieren based on the German word [flir] which means streak and it was first observed in 1665 by Robert Hooke who was using Two candles and some lenses then in the 19th century they used this method to try to find defects and the glass used to make Lenses and more recently people have used Schlieren to study Aerodynamics and fluid flow because it allows you to see those pressure differences in temperature gradients So [you] can look at [shockwaves] and differences in the composition of gases So when you watch the lighting of this match you’re seeing heat generated from Friction Igniting phosphorus which in turn generates more heat and begins the reaction between sulfur and potassium Chlorate which releases sulfur dioxide which you can also see And you can see my breath as I blow [out] the flame [I] Am so excited that I got this set up to work So if you can think [of] anything that would look really cool in Schlieren, then let me know in the comments And I will try [to] make [it] happen, and if you’re new to this channel, [we’ll] click here to subscribe I’ve got some awesome videos coming up very soon

100 thoughts on “Seeing the Invisible: SLOW MOTION Schlieren Imaging

  1. how about relighting an extinguished candle relighting from a flame placed in the rising vapors of the wax, like when you have a lit match or other flame source and blow out a candle then put the flame above the wick and the flame jumps to the wick relighting the candle.

  2. You explain at about 2:00 if the mirror were spherical the center would be where you have the light source. I think, if the mirror is spherical you’d put the light source (and razor and camera) at 1 focal length, but for parabolic mirrors you put the light at 2 focal lengths for the same effect, with the added advantage of increased contrast because of the extra distance for the light divergence to be doubled.

  3. but why the mirror? If the light converges back to one point why not just point the light onto the cameralens?

  4. I'm curious if its possible to use a big Schlieren mirror to capture a full person in view? since we give off heat, I'm curious if it can capture a Shaolin monk who is circulating his chi to specific points of his body? if chi is real would we see more heat from that spot?

  5. I happen to have three telescopes sitting idle. An 8", a 12", and a 16". Have a canon 60D with magic lantern installed, I think it will now shoot raw video. Does anyone know if the optical tube housing the mirror is an issue? I can remove the corrector and secondary mirror, but the tube is a fork mount and would make a nice way to aim the mirror. Is anyone attempting this with a SCT telescope?

  6. I got the 40cm diameter of the mirror and I can guess the focal length, but it would be great if you'd cite that # as your setup delivers such optimal results.

  7. Hi.. can you please guide me towards building my own setup. I mean with the specifics of a Mirror and other. Requisites. It is for my research purposes. Thermal cAm is not quite cheap. So, Schlieren just might help me. Will be waiting for your Reply. Thanks.
    Bdw.. Subscribed a d updates .
    Awesome work. ?

  8. Does anyone know which was the method used by Robert Hooke? (in 1665 with two candels and some lenses as said in the video) Thanks a lot!

  9. Would you please tell me where do I get that mirror?
    I find 40cm diameter and 68cm focal length concave mirror. However, I need at least 1.5 meter focal length.
    If you know please leave a comment please.
    @veritasium
    @xXJTXx

  10. CAN IT DETECT A HIGH PRESSURE AIR IN A BALLOON PASSING BETWEEN THE CAMERA AND THE MIRROR IN TOTAL DARKNESS?

  11. We are doing schlieren for shock waves visualisation . It would be helpful if u can share the camera settings

  12. If you wonder why you get a spike of views on this video, it's this: https://www.nasa.gov/centers/armstrong/features/supersonic-shockwave-interaction.html

  13. A rotating object movings through something dense like oxygen.. or even tungsten hexafluoride! It would be interesting to visualize the Magnus effect..

  14. Discovered in 1665……. Whaaaa? So i guess it's plausible german scientists actually made ufo's back in wwII.

  15. Have you tried or have you knowledge about use of the Schlieren Imaging principle in the SWIR band (0.9 to 1.7microns)?

  16. Hi

    Veritasium

    @5.48, May I use this frame as a cover art for my album? credits to you and advertisement on my album and songs is what I can offer.
    Thanks let me know.

  17. Please, I have seen tries, buy my dream was to see all the different electromagnetic fields around us. Wifi, 3g, Radio, FM, VHF, so on. This one is hard.

  18. @veritasium I accidentally found one in my laundry room! Check my channel, I don't want to link here for spam's sake.

  19. Awesome! But be careful with telescope mirrors guys, they are beautiful and dangerous. Keep it away from the sun!!

  20. Does anyone know where I can find a large concave mirror like the one in the video?? It will be helpful thxs !

  21. Awesome videos.
    Could you add some technical details about the light source and the mirror used in your Schlieren setup?

  22. I dont really think a speaker will work. This isn't detecting movement of air, just difference in the temperature of air. The sound waves moving around dont increase or decrease in temperature so you wont be able to see them

  23. please make a detailed tutorial about how to setup this at home and how to set the camera, at what settings, and just everything else
    please, I want to make this myself

  24. You can actually see some schlieren with your unaided eye. If you leave a car out in the Sun with its windows up for a prolonged period of time and then open one of the car doors on the side facing the Sun, you can see the schlieren effect on the car seat as the heat trapped within the car escapes.

  25. Awesome video M8 . I found this clip looking for another video I watched a few years back but can't find now . The person had a special camera that filmed all the different invisible Fumes the eye could not see he walked the streets filming and just about everything gave off invisible fumes . I'd never seen anything like it it was insane but I don't know what the name of it was and can't find it anywhere . Do you of your subscribers know how I can find it I would be very Grateful for any help Thank you .

  26. This must be the best example of fluid dynamics in the sense that every part of universe is in constant motion, the stronger replacing the weaker.

    Even space is made of matter that fills in the space by moving all the time.
    What I am trying to say is that fluid dynamics is not about fluids only, but gases and solid masses also are governed by the rules of motion.

  27. I'd like to see the difference in heat coming of the top of your head before and after eating spicy buffalo wings.
    ?

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