Lasers Defying Gravity

Science Insider

HOW LASERS WORK: "Laser" is an acronym for Light Amplification by Stimulated Emission of Radiation. It describes any device that creates and amplifies a narrow, focused beam of light whose photons are all traveling in the same direction, rather than emitting every which way at once. Lasers can be configured to emit many different colors in the spectrum, but each laser can emit only that one color. There are many different types of laser, but all of them have an empty cavity containing a lasing medium: either a crystal like ruby or garnet, or a gas or liquid. There are two mirrors on either end of the cavity, one of which is half-silvered, meaning that it will reflect some light and let some light through. In a laser, the atoms or molecules of the lasing medium are "pumped" by applying intense flashes of light or electricity. The end result is a sudden burst of so-called "coherent" light as all the atoms discharge in a rapid chain reaction.

WHAT IS GRAVITY? In the 17th century, Isaac Newton came up with the law of universal gravitation, but he couldn't explain the underlying mechanism behind gravity. In 1917, Albert Einstein proposed his theory of general relativity. This attributes the force of gravity to the unseen warping of the fabric of spacetime, caused by the presence of mass (or energy). The earth always travels in a straight line. The presence of the sun curves space and thus the earth appears to be moving in an elliptical orbit. Imagine a rubber sheet stretched out tightly. If a bowling ball is placed in the center, the ball's mass will cause a depression in the sheet. If you then place an apple on the edge of the sheet, it will roll down the slope towards the center. The depression can't be seen by someone looking straight down at the sheet from above, so it appears that the apple was pulled by an invisible force.

The Materials Research Society, the American Physical Society, and the Optical Society contributed to the information contained in the TV portion of this report.