I have an item that you need to add to your Bucket List. I want to tell it in a little bit of a story format. It will be worth it though, I promise. It's involves Lasers and Holograms. Still with me? Great.
Back when I was at MIT, I took a class called Strobe Lab. This was one of the most popular classes at MIT, and you had to enter a lottery to get in. I managed to get in on my second try, which is pretty fortunate. I learned how to properly take pictures (what f-stops - or sometimes called f-numbers - and shutter speed are and how you use them to create different effects like blurring the background) and develop film (not colored film, although the principles are the same). The reason they taught us that was because the class was taught in a place called the Edgerton Center.
Doc Edgerton was a professor of electrical engineering who also loved to photograph life under the ocean where it is very dark. To do that, he converted an obscure laboratory device called a strobescope and tranformed it into something resembling the Strobe Light that you see today at raves and clubs. During World War 2, they used his invention to take photographs from spy planes over Berlin at night so that they could do it discreetly and not be shot down by anti-aircraft fire. A quick pulse of light was all you really needed, but it had to be extremely bright, and Edgerton's design did exactly that (he had an experiment called the exploding wire that he must have done while trying out different ways of refining the strobe light device).
He also started taking photographs of all kinds of cool things like bullets going through apples. You can see a lot of his fine work on the Edgerton Center website. We got to do a lot of those same experiments. My team got to fire bullets through doughnuts and cheese and then take high speed photographs of the event. It was really cool. Then we had to do a final project. Edgerton's milk drop photo is one of his most famous, so our team decided to do it in 3d. As a hologram.
I told you there'd be lasers
This is where the lasers come in folks. If you aren't familiar with how holograms work, well, I'm not going to detail it for you. I give you one word though: Physics. No, I'll give you a few more. I actually wrote a whole entire separate post about it if you are interested.
The short story is that you use lasers that are aimed towards the object you want to capture. The beam gets split along the way into two beams, both going through the recording medium (the film, but not your typical photographic film - the principle is somewhat close, but it works differently for holograms). One of the beams hits the object and scatters in all kinds of directions. Some of that light gets reflected back towards the recording medium, and it also overlaps with the other beam, creating an interference pattern that is then captured on the film. You see the image in the hologram by shining light of the same frequency as the lasers that created the hologram.
The entire process of capturing a hologram has to be done in complete darkness, as any additonal light would also create interference, and it would mess up your capture. So imagine this: three MIT grads in the dark, trying to take the recording medium out of a box, install it into some holders, then turning on the spigot that lets the milk out, firing a quick laser pulse, then taking the medium out of the holders and back into the box, all in complete darkness.
Suffice to say that it took a few practice runs to even get the feel of doing those steps, not actually firing the laser. When we did it the first time for real, when the lights came up, the milk had all run out. We didn't know whether it had lasted all the way until the laser pulse (it hadn't), and we wouldn't know until we developed the film (like regular photographic film, you need to apply something to it so that additional light can no longer modify it).
It took a few tries (and literally a few days because we could only do it a couple times and then we had to wait for the development), but we got it. I wish I had a way to show you what I saw when we got the final product. Our laser was green, so we had to use green light to see it. You looked through the medium and you could see the milk drop. The crown was perfect. You moved it around and the milk drop would shift around. The coolest part by far was the fact that if you looked at the milk that had already hit the platform, you could see a reflection in it. You moved it around and the reflection moved around. Hands down, the coolest thing I've ever done.
Now to the Bucket List!
Ghost (the platform I use to blog) informs me that I have hit almost 1000 words. It was a journey, but actually it was really fun. I got to talk about a famous MIT guy, a lab that was named in his honor (and I worked there one summer and my freshman advisor was the professor who ran it, Professor Kim Vandiver), the invention of the Strobe Light, how it got used during World War 2, how holograms work, and my personal experience creating a three dimensional holographic image of a famous photograph.
Why I asked you all here is to tell you this. The coolest hologram I ever saw was at the Museum of Science in Boston. They were hosting some holograms on loan from MIT. Those holograms are now available at the MIT Museum. Go there. The next time you are in Boston/Cambridge (it is literally in between the two), go see it. This is the hologram I'm talking about - someone made a YouTube video of it:
Add that to your bucket list. The video does a pretty good job of showing it to you, but you won't really believe it until you look at it with your own eyes.
Thanks for sticking with me. :)