[00:01] >> [music] >> really in your walls right now. To see blink, but just don't look away from the dot. Okay, ready? [music] Ooh, you will subscribe to the Curiosity Box. I'm just kidding. I'm not trying to
[00:16] hypnotize you, even though I could. What I'm going to do instead is switch this image back to natural colors. [music] You ready? Here it is. Ah, just kidding. just happened is called an afterimage, [music] and we still don't fully
[00:28] understand how they work. We do know that if you stare at something green, photoreceptors in your retina that are sensitive to green, that its green light falls on, will quickly adapt and become less sensitive to green light. Your
[00:41] brain expects this and isn't confused until the scene changes. At that point, adapted receptors will barely make it to your awareness. It's essentially inverse is left behind, which in [music] this case is magenta. That's a partial
[00:56] theory of afterimages, but there's more than just your photoreceptors involved, there, colors that are not falling on any photoreceptors, like [music] this spreading illusion, can still cause afterimages. J.H. Brown's Spectropia,
[01:12] first published in 1864, was the first book dedicated to afterimages and how a science of them may help explain otherwise inexplicable visions. Now, this is our restored high-contrast [music] edition, and it comes in the
[01:24] Camera Lucida, you can get this for free. And if you join us for an entire year up front, [music] you will get an extra for free. But here's the question: Are afterimages illusions or hallucinations?
[01:38] Well, typically illusion describes a misperception of something that is really there. Hallucination, on the other hand, describes perceiving something that isn't even there at all. Now, an afterimage that you see is not a
[01:51] you. So, for that reason, many philosophers consider afterimages hallucinations. Now, still others say, "No, no, no, it's an illusion." Um the aren't [music] there, but they were there. Okay, when you see an after
[02:05] image, you are seeing something from the past, but it's also an illusion because you're misperceiving its colors. [music] Okay, here's my take. I don't think it's time travel, but I do think it's an illusion. You see, the original natural
[02:17] in this image are really there. They make up the values of white in the photoreceptors have been adapted to their opposites, well, they'll filter inversion of the opposite, [music] which is the natural scene. In other words,
[02:32] the ghost you can see on your wall after staring at this image for a while was already in the light coming off of your wall. In the same way that Michelangelo's David was already in the block of marble before he started
[02:46] carving. [music] You can sculpt horrors out of the raw material around you. And that is what I call beautiful.