Lene Hau: The woman who stopped light

Much of the scientific community believes Dr. Lene Hau’s achievements are so remarkable that she will win a Nobel Prize. The Harvard professor accomplished something that Einstein said was theoretically possible, but which most scientists didn’t believe could actually be done. In short, Dr. Lene Hau stopped light. And, as if that weren’t enough, she started it up again. She literally trapped a beam of light and then released it, putting the brakes on a form of energy that travels at a speed of 186,000 miles per second, forcing it to cease moving and subsequently allowing it to rev up again and continue. This Danish-born physicist has rocked our world—in a very good way.

Although practical applications are still relatively far off, even the word “revolutionary” seems mild when considering the possibilities that Dr. Hau has opened up. She has set the stage for ground-breaking advances in every sort of existing technology, especially communications, and is no doubt lighting the path to undreamed of new technologies.

Lasers, Mirrors and “Optical Molasses”

To understand the mind-boggling nature of Dr. Hau’s amazing feat, we have to oversimplify quite a bit: Say that a glass window allows light to pass, a brick wall absorbs it and a mirror reflects it back. What Dr. Hau did was to find a substance she has called “optical molasses,” a type of matter that would trap light rather than let it do one of the three things above.

That type of matter is called a Bose-Einstein condensate. To create this condensate, she invented a method for cooling sodium atoms—the same atoms that make up ordinary table salt—to a few degrees above absolute zero, a temperature so cold it doesn’t exist in nature, not even in outer space.

From there, again enormously oversimplifying, she devised an ingenious and highly complex apparatus based on lasers and mirrors designed to counterbalance, control, amplify and attenuate each another in order to enable the functioning of her delicate, finely-tuned system.

Dr. Hau describes her first step as slowing a beam of light to the “speed of a passenger train.” She then went on to slow it to that of a “bicycle.” Ultimately, she was rewarded with a history-making triumph: She stopped a beam of light and then allowed it to start moving again. Such simple words belie the earth-shattering implications of her successful experiment.

To give just one example of an eventual application, light can be manipulated, or “poked, prodded and squished,” as Dr. Hau likes to say. Light is what carries the information along fiber optic cables and can only transmit as much and as fast as the cable allows. Imagine if the cables were no longer necessary. Many of today’s infrastructure needs would disappear. The phrase “at the speed of light” would no longer be hyperbole. This is just one of a multitude of potential ways in which this brilliant physicist’s work will change the world.

Stopping Light Wasn’t the Only Headline

Once Dr. Hau’s research began to bear fruit it also came to be known that this extraordinary woman--who already had an international reputation in her field before she even began to think about stopping light--was originally refused funding. The world’s jaw dropped.

She had applied to the National Science Foundation for a grant but was told that her background as theoretician had not prepared her for the extremely complicated nature of the experiments she wanted to perform. The Foundation’s negative response brought up a longstanding and sometimes controversial division in science. Very roughly speaking, there are theoreticians, aka idea people, scientists who worked with pencil, paper and slide rulers in the old days and now work with computers. Then there are experimentalists, scientists who design the experiments to test the hypotheses of the theoreticians, which may look good on paper but which must also pass the reality test. Putting people into boxes with labels may sometimes be a practical necessity, but it’s a system that doesn’t leave room for geniuses like Dr. Lene Hau, whose varied and brilliant talents won’t fit into any one box. As a person of drive and passion would be expected to do, Dr. Hau simply went elsewhere for funds and a private organization gave them to her. The rest is history.

Physics Needs Diversity

Another question raised by Dr. Hau’s pioneering work is: “Why are there so few women physicists?” There are a multitude of possible answers, but Dr. Hau’s response to one interviewer certainly makes a very good case for gender diversity and diversity of all kinds. 

Many men—I shouldn't just say men, many women, many people—have a hard time dealing with different backgrounds, different points of view. Personally, I don't particularly want to have clones of myself running around. That's pretty boring. Sometime I’ll think I’ve figured something out and that I have the perfect argument. Then somebody who has also thought about it brings up an objection and I say to myself, ‘Oh, I hadn't even considered that.’
For Women in Science

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