Lasers are tools that emit concentrated beams of visible light by stimulating electrons into emitting photons. The term is an acronym for light amplification by stimulated emission of radiation.
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This effect was predicted by Albert Einstein in 1917, and requires all excited electrons in a material to exist in the same excited metastable state within their atoms. Pumping all atoms through the same mechanism, such as electricity or flash lamps, can create this environment.
Although Theodore Maiman built the first working laser in 1960, Gordon Gould coined the term earlier. Charles Townes and Arthur Schawlow of Bell Labs filed a patent after Gould came up with the idea and name, but before Gould filed his patent.
Tattoos place ink below the skin's surface layers in packets too large for white blood cells to clear out. By breaking the ink into smaller pieces, the immune system, which is responsible for removing foreign matter, can process them.
Lasers are used when scanning groceries, printing documents or undergoing cosmetic procedures to enhance efficiency, precision and accuracy. Missile defense, targeting and optical communication systems have made using laser technology habitual in the military.
The fine-structure constant, α, which quantifies the strength of charge particle interactions, affects the pulses of light emitted by atoms as electrons move between energy levels. While time is tracked by counting these pulses, comparing the counts across clocks using different atoms reveals the value of α.
The sound made by an object when struck is its resonant frequency, which is the sound made when energy is dissipated. Providing energy at that frequency amplifies the vibrations, rather than allowing them to dissipate, which can deteriorate the object's structural integrity.
While photons possess energy, they also have momentum, which allows them to collide like billiard balls with other particles to slow them down and reduce their temperature. Using multiple lasers from different directions, particles can be cooled to less than one degree above absolute zero.
Launched in 2016, Breakthrough Starshot is a project to send gram-sized spacecraft to the nearest stars and their planets at 10% to 20% the speed of light after being accelerated by ground-based laser systems. The project requires orders of magnitude advancements to current technology.
At 96, Arthur Ashkin became the oldest person to win a Nobel Prize for showing how lasers can hold and measure objects, which has since been used to explore microbiological environments. The award was also given to Gérard Mourou and Donna Strickland for developing a method of creating optical pulses.
The Laser Interferometer Gravitational-Wave Observatory splits a laser and sends the two beams down 4-kilometer-long perpendicular tunnels, where they reflect off two mirrors. Passing gravitational waves warp space, causing the reflections to be out of sync when they meet.
Since the time our ancient human relatives began using stone tools to perform tasks, humans have harnessed scientific knowledge and new technologies to advance our ability to feed ourselves, increase our health, expand the boundaries of our knowledge, and much more. From artificial intelligence and quantum computing, to optimizing the human body in pursuit of a long and healthy life, and much more—learn about these topics and more with our smart-but-digestible overviews and expert-curated resources.