The Science of Light

While I spent my free time in Israel traveling and seeking out live music, I happily spent my weekdays interning at the Bloomfield Museum of Science in Jerusalem. The museum was founded by the Hebrew University of Jerusalem with the goal of inspiring an interest in science and engineering amongst the nation's younger generation. The reason for my summer travels and source of my living stipend, my internship at the museum was organized through MISTI (MIT International Science and Technology Initiatives), a collaboration between MIT and universities and companies in other countries around the world, offering students the opportunity to participate in internships abroad. MISTI brought 50 students to Israel this summer, scattered throughout the small country's urban centers. Surprisingly, I was the only one in Jerusalem.

The museum is located next to the Hebrew University's Givat Ram campus. It's a forty minute walk to the museum from my apartment, leaving from the cobblestone streets and restaurant-filled city center to cross Sacher Park and pass by the Knesset, the House of Representatives of the state of Israel.

Approaching Sacher park on my walk through the hills of Jerusalem.

The military guards stationed in front of the Knesset, touting automatic rifles, would often stop me and ask my destination. I generally found it amusing to remove my headphones to the question of "Do you have a gun?", but they obviously and necessarily take security very seriously.

In mid-August, as the protests were growing, I would often pass demonstrations in front of the Knesset. There are remarkable similarities between today's Occupy Wall Street movement and the camping protestors calling for social reform across Israel. After nearly three months of demonstrations across the country, the police only recently evicted protestors from the tent city on Rothschild Boulevard in Tel Aviv.

The science museum was a haven from Jerusalem's political and religious turmoil. With the goal to educate and inspire in the doctrine of science, the museum seemed to be a unifying force among its workers and visitors. Exhibits were presented in Hebrew, English and Arabic. Most of the tour guides were in their early to mid-twenties, out of the army and often studying in university. A few high school students worked there as well. In the basement workshop, a small team of engineers and mechanics had designed the museum's older exhibits, with themes of physics, electricity, optical illusions, communications technology, water purification and more.

Since the museum's founding, the same core team had constructed and maintained its exhibits, with the help of interns and community volunteers. It was no menial task to keep the exhibits up and running, while simultaneously developing new exhibitions 2-3 times a year. It was impressive to see the dedication and hard work invested in the weeks leading up to the opening of the museum's big summer exhibition, Innovations Inc. Highlighting Israel's technological innovation and expansive success in generating startup companies, the exhibit showed off recent inventions of a number of Israeli companies and sought to explain some of the tools necessary to innovate and think outside the box.

The exhibit went up in under two weeks.

It showcased Israeli innovation

and the social and cultural processes that drive entrepreneurship.

The project that I took on was part of the development of a future exhibition, set to open near the end 2011. The exhibition would be centered around the physics of light, and the vast array of technologies that utilize electromagnetic radiation. I explored the potential of using a photochromic dye to demonstrate simple characteristics of fluid dynamics.

Photochromism is a chemical's ability to undergo a reversible, light-induced change of color. A common example would be photochromic eyeglasses. Under ultraviolet radiation from the sun, the lenses change from translucent to shaded, but when taken out of the sun, the lenses return to their clear state. When a photochromic material is struck by the correct wavelength of light, the light's energy will excite the material's molecules into a new chemical structure. This new structure will absorb and reflect different portions of the electromagnetic spectrum, appearing to take on a different color. This new chemical structure is generally unstable, and the molecules will eventually revert back to their original form. High power intensity and tightly controlled wavelength make lasers the perfect toy for photochromic gadgets.

The museum had recently produced paint to print photochromic paper for use in a new exhibit they developed called Pendulight. Many science museums have a two-axis pendulum, drawing with a marker or pouring sand to trace the patterns of the swinging pendulum. The Pendulight uses a laser and this paper printed with a layer of photochromic dye to create a surface that can record the pendulum's arcs, simply fading after approximately 15 seconds.

The obvious next step in awesomeness is to take this reusable laser-writing technology and bringing it into the third dimension. Theoretically, with the right optics and chemistry know-how, you should be able to create a 3D display, using some sort of photochromic-dye-injected solid and an optics system capable of focusing a laser on the photochromic material at a specific x-y-z location.

This obviously exceeded my technical understanding of chemistry and optics (not to mention project budget). Instead, I researched methods of dissolving photochromic dyes in fluid, which could then be used as a novel method of showing fluid dynamics principles such as convective flow, turbulence and boundary layers.

Unfortunately, a large portion of my work simply confirmed what we had already feared; there is not (at least not yet) a known solvent, capable of dissolving photochromic dye while maintaining high-quality color-changing characteristics, that is not highly toxic and likely carcinogenic. This is not exactly attractive when developing an exhibit for a children's museum, and ultimately a lot of thought will need to be put into the safety features of the exhibit.

After experimenting with different color-changing dyes, I built a functional prototype to prove out the capabilities of this technology to intrigue the curious museum visitor. Here's a couple pictures of the setup and a clip in action.

Prototype of red photochromic fluid on spinning platform with laser wand.

Blue photochromic fluid rising in convection as a result of heating from the incident laser beam.

If you're somehow still enthralled by this phenomenon (I still am...planning to put up a photochromic wall in my apartment), here's a cool art exhibit at a museum in Japan utilizing photochromic fluid.