As I head down the rabbit hole of my own bias, I hope to explain why the laser (Light Amplification by Stimulated Emission of Radiation) is so important. I am a practicing laser physicist, and have already given short arguments for why science in general is important and why physics specifically is important. Now, why is the laser important, and why is it something special? The answer to this lies in what light is exactly and how it interacts with the world around us, and exactly what a laser allows us to do. The unique qualities of a laser make it the most important tool for advanced scientific discovery outside of the computer.
I have often heard the declaration “A lab is not a real lab unless it has a laser!” I may not go that far just so I don’t offend anyone, but I certainly agree with the sentiment at least for the physical sciences. Since the invention and rapid advancement of the laser in the 1960s, they have spread to all sciences (not just the study of light, optics) to help study materials and samples of all kinds, and to make precise measurements.
Most laser light is in the optical frequency range, which is the same range of colors (different frequencies are seen as different colors by our eyes) that we see every day. And even the laser light outside of the visible range is usually only just outside of it (infrared and ultraviolet, like what the Predator sees). This is not an accident. We see these ranges of colors because they are what come from the sun, and we evolved to see the light that is most relevant. They come from the sun because they are related to the temperature of the sun. The reason that most lasers produce light in the same range is because the sources of lasers are usually some type of atom or molecule (either in a gas or most commonly in a crystal). The laser material, the atom or molecule in whatever form, relaxes from an excited state when stimulated and produces more light than what came in.
Because of how lasers work, being produced from excited states of atoms or molecules, they also are uniquely suited to study atoms and molecules. We use the light from lasers to probe all different types of new atoms, molecules, materials, biological samples, etc. to learn more about their structure, properties, and behavior in all types of interesting states and configurations. This is why well outside of a lab that is actually studying light, scientists use laser light as a tool for their own research.
Another property of laser light is that the wavelengths are usually somewhere around 1 micrometer (a human hair is around 100 micrometers wide, so think 100 times smaller than that). This wavelength is the distance between the peak of each oscillation of the ‘wave’ that makes up the light. This is such a small distance, smaller than most rulers of course, that scientists can use light to make measurements of physical sizes and distances to a much higher precision than ever before. Not only that, but scientists can also measure frequency and time with laser light, to incredible accuracy. Many of you have heard of the recent, Nobel Prize winning, discovery of gravity waves by LIGO. Well, the L in LIGO stands for laser, since the detection of the incredibly small changes in distance over mile-long arms of the LIGO machines is measured by a laser.
One more ability of lasers has to do with what light actually is. Light is not only something that we can see, but it is also a fundamental part of the laws of physics. Light is made up of photons, the same particle that is responsible for the electromagnetic force, that together form electromagnetic waves. These electromagnetic waves, of which laser light is a certain form, can exert forces on particles. Basically, laser light can exert force on electrons just like the voltage in all of our wall sockets causes electrons to travel through our cables and power all of our devices. However, laser light can do this in a very special way. Laser light can cool atoms, and can manipulate and accelerate particles, atoms, and molecules in a variety of ways. There is even something called ‘optical tweezers’ where you can trap (‘hold’) and move microscopic objects with laser light.
Because of these special properties of light and especially laser light, the laser has become an incredible workhorse of the scientific world. I wouldn’t say myself that a lab is not a lab without a laser, but at least most of the cool labs do have lasers.