What Is Light?

  • Published: 15 October 2015
  • We are so used to some things that we stopped wondering about them. Like light. What is light? Some kind of wavy thing, right? Kind of.

    Short bonus video for the people waiting for new stuff.

    Support us on Patreon so we can make more videos (and get cool stuff in return): https://www.patreon.com/Kurzgesagt?ty=h

    Steady: https://steadyhq.com/de/kurzgesagt
    Merchandise:  https://shop.kurzgesagt.org
    Newsletter: http://eepurl.com/cRUQxz
    Facebook: http://bit.ly/1NB6U5O
    Twitter: http://bit.ly/2DDeT83
    Instagram: http://bit.ly/2DEN7r3
    Discord: https://discord.gg/cB7ycdv

    The Voice of Kurzgesagt:
    Steve Taylor: http://voice-pool.com/en/english/

    Music by:


    Phiroze Dalal, T0T0S, Ryan OHoro, Kay Brinkmann, A La Mode, Marcelo Fernandes de Souza Filho, Vince, Thomas Shiels, Tom Wardrop, Shawn Marincas, Pontus Attåsen, Paul, Horacio Medina, Jim Yang, Arnav Guleria, Clemens, Robert McKone, Tahseen Mushtaque, Todd Binkley, Jochen, Vahur S, Matthew von der Ahe, Thomas Russell, Erick, Vivek Kotecha, Nils Caspar, Holger Fassel, Artur Szczypta, Jeff Fellows, Daniel Duffee, Konstantin Shabashov, Jackson R Hanna, Tim drake, Pascal de Reuck, Mike Galles, ByeongWook Lee, Guus Ketelings, Franko Papić, Thalia, Narat Suchartsunthorn, Lorenz Zahn, Brian Aparicio, Jörg Vogelsang, Rashed Ali, Darwin Ranzone, Tyler Thornton, Bernat Unanue, David Pfister, Ash Patel, Han Saini, Ute Moll, Vrm Vee Are Em, Ioanna Bischinioti, Jenny Zhou, Vince Babbra, Dan Cortes, Matt K

    What is light?

    Help us caption & translate this video!


Comments • 6 452

  • Kurzgesagt – In a Nutshell

    There's brand new stuff in the Kurzgesagt Merch Shop. Check it out here: shop.kurzgesagt.org

    • The White Stickfigure
      The White Stickfigure  5 days back

      Kurzgesagt pls do a video on the speed of darkness...

    • Sandesh Sookun
      Sandesh Sookun  3 weeks back

      out of curiosity, what was the topic of the video that you guys had to scrap?

    • DS Negi
      DS Negi  2 months back

      Light travel without medium cause it has photons and energy to carry it. Am I right. Please reply.

    • Doom2exe
      Doom2exe  3 months back

      By far one of best channel on YouTube keep up great work guys

    • chandan baidya
      chandan baidya  5 months back

      Do light loose it's speed at any point of time
      Actually after watching videos have a idea about space travel we can definitely move faster than light need your expert advice and guide
      Waiting for response

  • 3D
    3D  2 days back

    Thanks for the subtitles in kannada... Thank you

    • Cat Bot
      Cat Bot  2 days back


      • Pushpak Aggarwal
        Pushpak Aggarwal  3 days back

        If the light coming from anything is what we see... Can we see big bang too? If we some how make a telescope or something so powerful to see billions of light years far away...

        • MeunomeHD !
          MeunomeHD !  4 days back

          scientists: Nothing can travel faster than light
          Quantum particles: I'm gonna end those men's whole careers

          • ice cream RULES!
            ice cream RULES!  4 days back

            Kurzgesagt: This image is a lie.

            Me: My life is a lie...

            • anoop dagar
              anoop dagar  5 days back

              Me :Ted ed is the best
              In a nutshell: hold my beer

            • Neal Boonyarit
              Neal Boonyarit  6 days back

              What I light? Baby don't Kurz me, don't Kurz me, no more.

              • offkey
                offkey  7 days back

                didnt got the answer out of this video...

                • Neil Dickman
                  Neil Dickman  1 weeks back

                  Why when light is made it is immediately going so fast

                  • Cerberusan Lin
                    Cerberusan Lin  1 weeks back

                    ...I have a question? Is the shadow a kind of light or just a reflection of visible light?

                    • Cerberusan Lin
                      Cerberusan Lin  1 weeks back

                      @Occam's Razor Awww... probably understands, but most of the substances that absorb light are black. So I feel like a kind of material that can accept light, like the Carbon Nanotube can absorb 99.9% of visible light. Whether the absorbed light energy is converted into heat energy, if it can absorb 100%, it will not burn directly...

                    • Occam's Razor
                      Occam's Razor  1 weeks back

                      A shadow is when light from a luminous body (probably the sun) is blocked by a non-transparent object. So a shadow isn't a kind of light or a reflection of visible light but the absence of light, which we see as black. Although you are kinda right with the reflection thing. Some light still bounces off the object in shadow and into our eyes (thats why we see details instead of pitch black when we look at a shadow). I may be wrong here but I believe that this light bounces in from others sources onto the shadowed object then into your eye.

                  • Youp_ Dijk
                    Youp_ Dijk  2 weeks back

                    Sometimes I think the universe is a super intelligent human that has made it really hard for us to understand them. He's probably just trolling around or smt haha

                    • Carlo Pagani
                      Carlo Pagani  2 weeks back

                      Does light look different if ur the size of a very small bacteria or hydrogen atom?

                      • Sora. CDJapan.
                        Sora. CDJapan.  2 weeks back

                        Is that dva from overwatch

                        • Flamebuster32
                          Flamebuster32  2 weeks back

                          But is light lit?

                          • Mohammad Aman
                            Mohammad Aman  2 weeks back

                            Love you Kurzgesagt... Great video indeed

                            • Rafael Camargo Urango
                              Rafael Camargo Urango  2 weeks back

                              I heard "loight" at the beginning, is this British accent right?

                              • Divinest Beats
                                Divinest Beats  2 weeks back

                                Let THERE BE LIGHT

                                • nineball039
                                  nineball039  6 days back

                                  ... and matches were invented.

                              • VAK
                                VAK  2 weeks back

                                Yeah but..

                                *_What is Love?_*

                                _Baby don’t hurt me, don’t hurt me no more_

                                • Lazar Dookie
                                  Lazar Dookie  3 weeks back

                                  Me: WHAT DOES LIFE MEAN?
                                  Kurzgesagt:*Drops the mic*

                                  • Random Gaming
                                    Random Gaming  3 weeks back

                                    Better than school

                                    • nineball039
                                      nineball039  6 days back

                                      In school you have to do the math too.

                                  • Mister Slovenia
                                    Mister Slovenia  3 weeks back

                                    How does it work?

                                    • Adonan the Stoic
                                      Adonan the Stoic  3 weeks back

                                      Alright, so I just looked up the whole, "light can be destroyed" thing. It turns out the energy it carries can't be destroyed, but the photon can when it changes from one form to another. By that logic, can't we say that matter can be created or destroyed when it changes form, either through fusion/fission or phase?

                                      • ofek10
                                        ofek10  5 days back

                                        @Adonan the Stoic But these can't be measured

                                      • Adonan the Stoic
                                        Adonan the Stoic  5 days back

                                        @ofek10 Actually, that reminds me of virtual particles. Those pop in and out of existence all the time.

                                      • Adonan the Stoic
                                        Adonan the Stoic  3 weeks back

                                        @ofek10 Well that's eye opening. Thank you for sharing.

                                      • ofek10
                                        ofek10  3 weeks back

                                        Well, yes and no. First of all, lets start with the "no" part:
                                        When a photon is destroyed, the energy most of the time goes to an electron. Meaning you had before the process energy in the electromagnetic field and an electron, and then there is no photon but the electron gets excited. The photon really was destroyed. In matter, taking 4 hydrogen atoms and fusing them into a helium atom doesn't really count as creating matter, just rearranging the elementary matter particles.

                                        BUT, in beta decays, matter is created (for example if you start with a neutron and an electron is emitted, that electron wasn't there earlier). And when an electron and a positron collide they annihilate leaving only photons. So the "yes" is that we already know about processes where matter is created and destroyed but it's not the same thing that you thought.

                                    • Seagull
                                      Seagull  3 weeks back

                                      I don't understand anything he just said but I know something and I'm not sure what it is.

                                      • JD - 05WL - Credit Valley PS (1653)

                                        What is light...

                                        Baby don’t hurt me, don’t hurt me, no more...

                                        • I Dont Know
                                          I Dont Know  3 weeks back

                                          Can someone explain how light carries information... like when light hits a strawberry.. does it block out all light but the red part of the spectrum? IDKKK and if it its true then why does blue and green light get blocked out when light hits the strawberry

                                          • ofek10
                                            ofek10  3 weeks back

                                            Light carrying information usually is something talked about in communication, but understand that's not your question. If I understand correctly, you're asking what is the origin of absorption spectra, right? If so, the answer is related to the energy levels of molecules - it turns out that electrons mostly absorb light of a specific color when gaining a certain amount of energy. Because molecules don't allow the electron to absorb any amount of energy it wants (quantum mechanics is to blame for this), the electron will only absorb "allowed" colors. This depends on the molecule, so you get some stuff absorb strongly in the yellow/green/blue part of the spectrum like strawberries and other stuff absorb different colors.

                                        • Khaki Man
                                          Khaki Man  3 weeks back

                                          Imagine being one of the 1.4k people to DISLIKE a video about light. LMAO

                                          • Apple Pine
                                            Apple Pine  3 weeks back

                                            damit ich es einmal gesagt habe: was ist eine welle? eine mathematische funktion! f(x) = sin x

                                            • Aleksandra Sulenta
                                              Aleksandra Sulenta  3 weeks back

                                              Light is what scares edgey teens

                                              • Lewin Wu
                                                Lewin Wu  3 weeks back

                                                So this is a dumb question but what happens when the wavelength or the frequency approaches infinity?

                                                • ofek10
                                                  ofek10  3 weeks back

                                                  What kind of answer are you expecting? If the wavelength approaches infinity then the wavelength approaches infinity :) . Technically correct, but I'm guessing that's not what your asking.

                                              • 로빈히
                                                로빈히  3 weeks back

                                                여기 한글자막 찰지게 잘해놨네

                                                • Ron Watson
                                                  Ron Watson  3 weeks back

                                                  Here's a few thoughts that make me realize that we just don't know.

                                                  1. If you were to have an intersection where an intense amount of light flowed through directly crossing the path of a small fragile amount of light such as starlight, why is the starlight not just blown away by the intense amount of light that it had to pass through? I don't think light is a thing and yet....

                                                  2. Starlight moves through a vacuum, which has nothing in it, not even atoms. To prove that point, the Voyager 1 has been moving at 60,000 km/h for forty years through space and doesn't seem to be slowing down from friction. So light must be a something if it travels through space where there is nothing else because something has to move through this vacuum in order for it to land on our eyes.

                                                  3. And yet light can damage your eyes if it's too intense so it must be a something, and yet there is nothing material that can accelerate up to this kind of speed instantaneously. Okay, enough of this, I'm turning out the light and going to bed.

                                                  • Benjesus
                                                    Benjesus  3 weeks back

                                                    What is light?

                                                    Baby don’t hurt me
                                                    Don’t hurt me
                                                    No more

                                                    • Murat Senol
                                                      Murat Senol  3 weeks back

                                                      I never see a correct illustration of elecromagnetic waves.

                                                      One of them is the derivative of the other. They should be 90 degrees phase shifted, meaning when one is zero the other is at its peak.

                                                      If they were both zero at the same time, that would mean 0 energy, and it would just stop existing.

                                                      • ofek10
                                                        ofek10  3 weeks back

                                                        Actually no, in a plane wave the're in phase. The spatial derivative of one is the temporal derivative so when you calculate it you see that they are in phase. There are points that the energy density is 0, but that's ok.

                                                    • Daniel bernat
                                                      Daniel bernat  3 weeks back

                                                      guys if photons have no mass how do they exist ? i need answers

                                                      • ofek10
                                                        ofek10  3 weeks back

                                                        Light is just a wave in a field. It's like talking about the mass of water waves in the ocean. Maybe the water has mass, but what is the mass of a water wave? Moreover, Light is a wave in the electromagnetic field, how would you talk about a mass of such thing?

                                                    • Ck lemri
                                                      Ck lemri  3 weeks back

                                                      aliens do exist, they just have a different wavelength in the EM spectrum, thats why we cant see them

                                                      • Jayden Bell
                                                        Jayden Bell  4 weeks back

                                                        Woooahah. Does anybody else feel that this video was narrated too quickly?

                                                        • jarrod lutes
                                                          jarrod lutes  4 weeks back

                                                          This is why I failed science I could not follow a damn thing he said.

                                                          • xXJarvis7Xx
                                                            xXJarvis7Xx  4 weeks back

                                                            "What is Light?"

                                                            Light : *I...AM JUSTICE*

                                                            • Biednymaniek
                                                              Biednymaniek  4 weeks back

                                                              Clar it 😑 i have enought 🙄 take an offer

                                                              • David Zamudio Dominguez
                                                                David Zamudio Dominguez  1 months back

                                                                Por qué hay personas que le otorgan "no me gusta" a estos videos educativos?? Creo nunca lo sabremos 🤷🏽‍♂️
                                                                Por mi parte, excelentes videos y saludos desde Tehuacán, México

                                                                • Yusuf Ali
                                                                  Yusuf Ali  1 months back

                                                                  I am commerce Student

                                                                  • Mr Bluntforce T
                                                                    Mr Bluntforce T  1 months back

                                                                    A little over 200 years ago it was claimed that your lungs would burst if you were to move over 60 mp/h in an some open Carriage.Later they said that the speed of sound was the ultimate speed limit,and now its ligtspeed thats max; why ?! I know the `Physics` behind it but they know far from everything and much of their theories are, well- theories and is often wrong just like Medical science is often wrong, not to mention `increased understanding of psychyatry` etc etc

                                                                    • ofek10
                                                                      ofek10  3 weeks back

                                                                      Do you have any reference stating scientists from 200 years ago claimed that the speed of sound is the speed limit of the universe? Because I always read papers claiming the exact opposite, that they didn't know that there is a speed limit.

                                                                  • David Sia
                                                                    David Sia  1 months back

                                                                    If light is 300,000 km/s, so it needs 2 secs to reach 600,000km?

                                                                  • dragonwarrior1820
                                                                    dragonwarrior1820  1 months back

                                                                    lightma balls

                                                                    • The Dweeb
                                                                      The Dweeb  1 months back

                                                                      What's interesting is how 100 years or more from now scientists will look at this video and laugh at how primative the world must have been during our time. They will be so much more advanced

                                                                      • Dakila Lozano
                                                                        Dakila Lozano  1 months back

                                                                        i wanna know know know
                                                                        *WHAT IS LIGHT*
                                                                        I WANNA KNOW! 🎶🎶

                                                                        • TurtleBoi TheGod
                                                                          TurtleBoi TheGod  1 months back

                                                                          Baby don’t hurt me