Speaker 1: Get in tech with technology with tech Stuff from stuff
Speaker 1: works dot com. Hey there, and welcome to tech Stuff.
Speaker 1: I'm your host, Jonathan Strickland. I'm an executive producer at
Speaker 1: how Stuff Works and I love all things tech. And
Speaker 1: on Christmas Day nineteen nineteen, Dr Robert N. Hall was
Speaker 1: born in New Haven, Connecticut. He would pass away on
Speaker 1: November seven, two thousand sixteen, at the age of nineties six.
Speaker 1: The New York Times would publish an obituary about Dr
Speaker 1: Hall on May tenth, two thousand eighteen, with the title
Speaker 1: Robert N. Hall, ninety six, whose inventions are everywhere? Is dead?
Speaker 1: What's so remarkable about this gentleman that necessitated an obituary
Speaker 1: in the New York Times nearly two years after he
Speaker 1: actually passed away? And I the late obituary anyway, Well,
Speaker 1: we're gonna learn about Dr Robert INN. Hall and his
Speaker 1: numerous inventions. Hall grew up in Connecticut, and when he
Speaker 1: was a boy, his uncle took him to a technical fair,
Speaker 1: kind of a science and engineering festival. His uncle considered
Speaker 1: himself something of an inventor, and he wanted to encourage
Speaker 1: Robert to explore topics of science and technology. And according
Speaker 1: to an interview that Dr Hall gave in two thousand four,
Speaker 1: he said, quote, he took me to a technology fair
Speaker 1: when I was a small boy in New Haven, Connecticut,
Speaker 1: and there were a lot of electrical exhibits. Bouncing steel
Speaker 1: ball bearings and tin can motors were spinning on a
Speaker 1: flat table stroboscopes. He got my attention. It seems like
Speaker 1: these were fascinating little things, and I would like to
Speaker 1: know how they worked. And he tried to explain them
Speaker 1: to me, and he showed me where to find books
Speaker 1: in the library. Later on, when I went to high school,
Speaker 1: my mom let me have a little laboratory in the bedroom,
Speaker 1: and I said, up a lot of experiments and see
Speaker 1: if I can duplicate a lot of these things. End quote.
Speaker 1: Hall continued his experiments and pursued his interest in the sciences.
Speaker 1: He initially focused on astronomy, which is a bit of
Speaker 1: a pun because he actually took it upon himself to
Speaker 1: build his own eight inch telescope, including grinding the mirrors himself.
Speaker 1: While in high school, he met with a recruiter for
Speaker 1: cal Tech or the California Technical Institute. This led to
Speaker 1: Hall taking some entrance exams for the school and he
Speaker 1: must have performed pretty well on those tests because he
Speaker 1: ended up with a scholarship to attend cal Tech. Hall
Speaker 1: studied science and engineering at school for three years, at
Speaker 1: which point he ran out of money and he had
Speaker 1: to take a year off to earn more. To finish
Speaker 1: out his studies. He got a job at lockeed Aircraft
Speaker 1: as a test engineer. This was just before the United
Speaker 1: States would be pulled into World War Two. After a
Speaker 1: year of working at Lockheed, he returned to cal Tech
Speaker 1: and finished out his studies, earning a degree in physics.
Speaker 1: Immediately upon graduation, he was recruited by GE that is,
Speaker 1: General Electric to come and work for them as a
Speaker 1: test engineer in Schenectady, New York. General Electric was the
Speaker 1: company that grew out of the merger of Thomas Edison's
Speaker 1: General Electric Company and the Thomas Houston Electric Company of Lynn, Massachusetts.
Speaker 1: Both Thomas Edison and Charles Coffin, who were the leaders
Speaker 1: of the two companies, had made numerous acquisitions in the
Speaker 1: late nineteenth century and grown their respective companies considerably. General
Speaker 1: Electric became a sizeable conglomerate the day it formed through
Speaker 1: this merger in the late eighteen nineties. In nineteen hundred,
Speaker 1: GE created its own industrial research laboratory. By the time
Speaker 1: Hall went to work for the company in nineteen forty two,
Speaker 1: GE was known for introducing several technological innovations. In nineteen
Speaker 1: thirty nine, g E showed off a solar power concept
Speaker 1: called the sun Motor at the nineteen nine World's Fair.
Speaker 1: The following year, also for the World's Fair, g E
Speaker 1: showed off a lightning generator which created enormous powerful sparks
Speaker 1: between giant pillars, and in nineteen forty one, the company
Speaker 1: had been instrumental in building the first US jet engine,
Speaker 1: called the one A. Paul got to work on magnetron's originally,
Speaker 1: and I mentioned magnetrons in recent episodes on Alfred Lee
Speaker 1: Loomis and the Loran System. A magnetron is essentially a
Speaker 1: microwave generator. Inside a magnetron is a cathode. This is
Speaker 1: where our electrons come from. You can think of it
Speaker 1: as an electron generator. And when you heat up this cathode,
Speaker 1: you pour energy into it and it begins to boil
Speaker 1: off or release electrons. Now, what you're actually doing is
Speaker 1: boosting the energy level of re electrons in the cathode
Speaker 1: and Finally they get enough energy to go out and
Speaker 1: find adventure in the great wide somewhere, assuming there's a
Speaker 1: positively charged material nearby for them to go to. So
Speaker 1: surrounding the cathode is an anode in the shape of
Speaker 1: a ring, and this ring has some sort of notches
Speaker 1: or or or alcoves carved into it. These are the
Speaker 1: so called cavities of a cavity magnetron. They're sometimes called
Speaker 1: resonant cavities. Now that's going to be important in just
Speaker 1: a second. So imagine the cathode is a stick, and
Speaker 1: there's a ring surrounding the stick, and the ring has
Speaker 1: these little alcoves or cavities inside of it. The anode
Speaker 1: has a lack of electrons, giving it a net positive charge. Now,
Speaker 1: if there were nothing else to a magnetron, if it
Speaker 1: was just the cathode and the anode, and you were
Speaker 1: to turn it on and start to heat up the
Speaker 1: cathode and boil off those electrons, the all actrons would
Speaker 1: just zip on over to the anode once they had
Speaker 1: enough energy to do so. But there's a bit more
Speaker 1: to a magnetron than that. A final piece of the
Speaker 1: magnetron is a magnet underneath the anode. This creates a
Speaker 1: magnetic field that is parallel to the cathode. So when
Speaker 1: you heat up that cathode, the electrons are moving through
Speaker 1: both an electrical field and a magnetic field. As the
Speaker 1: electrons zoom past the cavities in the anode, these little alcoves,
Speaker 1: they cause the cavities to resonate, and this resonation creates
Speaker 1: microwave radiation. The wavelength of the microwave is dependent upon
Speaker 1: the size and shape of the cavity. One source I
Speaker 1: looked at while researching this likened the resonating cavities to
Speaker 1: a musical instrument that you blow across. So, since I'm
Speaker 1: from the Deep South in the United States, I'm going
Speaker 1: to use a wonderful musical instrument that is beloved here
Speaker 1: in my home state, a good old jug. When you
Speaker 1: blow across the top of a jug, it produces a
Speaker 1: note that who, well, there's a resonating chamber here in
Speaker 1: the form of the jug. The same thing is true
Speaker 1: inside this anode. The cavities and the magnetron behave in
Speaker 1: a similar way. As the electrons zoom pass the opening
Speaker 1: to the cavities, they pass some of their energy along
Speaker 1: which resonates and generates microwave radiation instead of sound. Magnetrons
Speaker 1: also have something called a wave guide, which, as the
Speaker 1: name suggests, is the method for guiding the microwaves to
Speaker 1: emit outward from the magnetron. Then you can use the
Speaker 1: microwaves for whatever purpose you had intended, such as to
Speaker 1: create a maser sort of the microwave predecessor to the laser,
Speaker 1: or you could do it to create a microwave oven,
Speaker 1: or a power the power source, or rather the microwave
Speaker 1: source for radar equipment. Hall's work on magnetrons will become
Speaker 1: a major contributor to the development of the microwave oven
Speaker 1: at g E, which was led by another guy named
Speaker 1: Rudy Den. And I've talked a little bit about that too,
Speaker 1: About the almost accidental discovery of how a microwave source
Speaker 1: could be used as an oven. I believe it involved
Speaker 1: the melting of a chocolate bar in someone's pants pocket.
Speaker 1: Such is the majesty of electrical engineering. I have more
Speaker 1: to say about Dr Hall in just a second, but
Speaker 1: first let's take a quick break to thank our sponsor.
Speaker 1: Hall also got to work on crystal diodes. Diodes are
Speaker 1: an important element in circuitry as they allow electricity to
Speaker 1: flow only in one direction, so it's sort of like
Speaker 1: a traffic keeping mechanism for electricity. Diodes are a simple
Speaker 1: kind of semiconductor. Semiconductors, as the name suggests, can act
Speaker 1: as conductors under certain circumstances and insulators and other circumstances.
Speaker 1: And these semiconductor is consisted of different materials that have
Speaker 1: specific properties. And N type material has extra negatively charged
Speaker 1: particles or electrons. A P type material has positive charge,
Speaker 1: so it would have what people would refer to as
Speaker 1: electron holes. It has a positive acceptance for electrons. By
Speaker 1: sandwiching these two materials together, you can create a semiconductor,
Speaker 1: a material that will conduct electricity along one direction but
Speaker 1: stop it from the other. This would be a diode.
Speaker 1: So how does this work? Why does electricity go one
Speaker 1: way but not the other way? Well, imagine you have
Speaker 1: a battery hooked up to this semiconductor diode, and the
Speaker 1: battery has a negative side and a positive side, as
Speaker 1: does the diode. The battery serves up direct current, meaning
Speaker 1: that the electricity will only flow through this direct path
Speaker 1: from the negative side to the positive side. If you're
Speaker 1: talking about electrons. We're not talking about the crazy way
Speaker 1: of saying positive to negative, which is the way Benjamin
Speaker 1: Franklin would have wanted it. We're just gonna talk about
Speaker 1: electrons here. If you hook the negative end of the
Speaker 1: battery up to the N type side of the semiconductor,
Speaker 1: the electrons flowing from the battery essentially push other electrons
Speaker 1: across to the P type material on the other side
Speaker 1: of the semiconductor and comes through the other side to
Speaker 1: the positive contact on the battery, and you have the
Speaker 1: flow of electricity. It just continues from negative to positive.
Speaker 1: The positive holes in the P type are attracted to
Speaker 1: the negatively charged particles in the N type, and current
Speaker 1: flows in this direction. But if you were to flip
Speaker 1: the battery around so that the negative side of the
Speaker 1: battery connected to the P type side of the semiconductor,
Speaker 1: the incoming electrons from the battery would just end up
Speaker 1: hooking up with these positive holes on the P type side.
Speaker 1: No electricity would flow. The two charges would separate within
Speaker 1: the semiconductor material, and so you wouldn't be able to
Speaker 1: pass a current in between it. It would act as
Speaker 1: an insulator. Hall worked on technologies like these for about
Speaker 1: three or four years before being urged by his colleagues
Speaker 1: to continue his studies and earn a pH d. And
Speaker 1: so Hall returned to cal Tech and got back to work.
Speaker 1: He graduated in night with a doctorate in nuclear physics
Speaker 1: and then returned to ge just in time to hear
Speaker 1: about a new discovery coming out of Bell Labs. This
Speaker 1: was called the transistor, and it would change Hall's life.
Speaker 1: The transistor was a huge breakthrough and engineering. It could
Speaker 1: perform as a switch or as an amplifier. And as
Speaker 1: an amplifier, a transistor takes in a weak electric current
Speaker 1: in the input and produces a stronger electric current in
Speaker 1: the output. As a switch, the transistor can create a
Speaker 1: strong electric current to flow through part of the transistor
Speaker 1: as a weak electric current flows in from another part,
Speaker 1: so it switches on that stronger electric current. If you
Speaker 1: turn off the weak electric current, the strong electric current
Speaker 1: also turns off. Now, in the previous section I mentioned
Speaker 1: at a very high level how a diode works by
Speaker 1: pairing in type and P type material in a simple way.
Speaker 1: A transistor is similar, except you can think of it
Speaker 1: as even more like a sandwich. And there are different types.
Speaker 1: But let's take an N P N junction transistor as
Speaker 1: an example. So imagine you've got a bit of P
Speaker 1: type material, meaning positively charged, so it's got the electron
Speaker 1: holes in it, and it's sandwiched between two different N
Speaker 1: type material sections. So these are areas that have a
Speaker 1: negative charge on either side. So the middle is your
Speaker 1: P type. On left and right you've got your N type.
Speaker 1: Uh So in a circuit you would say it's N
Speaker 1: type P type N type. On one N type end
Speaker 1: you have the collector side. On the other N type
Speaker 1: end you have the emitter side, and connected to the
Speaker 1: P type material, you have the base, and it's all
Speaker 1: about that base. Now, if you were to a ply
Speaker 1: of voltage between the base and the emitter, it would
Speaker 1: cause current to flow from the base to the emitter. This,
Speaker 1: in turn would allow a stronger current to flow from
Speaker 1: the collector to the emitter. The transistor would take on
Speaker 1: the rolls of another older piece of technology, the vacuum tube.
Speaker 1: And I've talked a lot about vacuum tubes in recent episodes,
Speaker 1: so you can listen to those and learn more about them.
Speaker 1: But the thing to remember here is that the transistor
Speaker 1: had the potential to take the place of vacuum tubes
Speaker 1: and drastically reduce the size of electronics, not to mention
Speaker 1: cut back on the amount of heat they would produce.
Speaker 1: Hall began to look into transistors over at GE and
Speaker 1: began to experiment with creating high purity germanium through a
Speaker 1: process called fractional crystallization. Hall found that by freezing germanium
Speaker 1: into a crystal would push most of the impurities away
Speaker 1: from the crystalline structure that formed inside the solid germanium,
Speaker 1: and by doing this slowly across a sample of germ manium,
Speaker 1: you could effectively push the impurities onto one end, and
Speaker 1: thus you would have a doped end of your germanium
Speaker 1: crystal while you have high quality germanium. But this process
Speaker 1: was pretty slow. Hall found that his process would create
Speaker 1: germanium that was a crystal diode, so you'd have one
Speaker 1: end that would act as a P type material and
Speaker 1: the other end of the same crystal would act as
Speaker 1: an end type material. And he used arsenic to dope
Speaker 1: the germanium, meaning he was introducing an impurity on purpose
Speaker 1: to alter the structure of the material to make it
Speaker 1: an effective semiconductor. He also found out that this introduced
Speaker 1: boron to the material, which he found very interesting. His
Speaker 1: work would later become really important for power plants because
Speaker 1: the materials he was working with ended up being able
Speaker 1: to handle tremendous voltages, so they became very important in
Speaker 1: g S work with electricity generation. Hall's work with germanium
Speaker 1: lead him to develop technologies that were useful in the
Speaker 1: detection of gamma rays, something that was important both in
Speaker 1: nuclear physics and cosmology. Gamma rays are type of nuclear radiation.
Speaker 1: It's electromagnetic radiation that typically comes from the radioactive decay
Speaker 1: of nuclei, and it is made up of photons, with
Speaker 1: the highest observed photonic energy we've seen so far. They
Speaker 1: also are an ionizing type of radiation, meaning the energy
Speaker 1: from gamma rays can strip away electrons from other atoms.
Speaker 1: Ionizing radiation is potentially dangerous. It can cause cellular damage
Speaker 1: and potentially genetic damage to an organism subjected to them,
Speaker 1: not to mention increase the probability of cancer, so they're
Speaker 1: dangerous things. It's not as dangerous as alpha or beta waves,
Speaker 1: generally speaking, just because they didn't to pass right through
Speaker 1: stuff as opposed to getting absorbed. Really one area of
Speaker 1: focus Hall dedicated himself too. In the early nineteen fifties,
Speaker 1: was working on a semiconductor device capable of producing light,
Speaker 1: a light emitting diode, in other words. A decade later,
Speaker 1: a colleague suggested to Hall that he used semiconductors to
Speaker 1: make a laser. Now in the nineteen fifties, Charles hard
Speaker 1: Towns showed how through the use of stimulated missions of radiation,
Speaker 1: he could create a maser sort of the microwave variant
Speaker 1: of a laser. At In nineteen fifty nine, Gordon Gould
Speaker 1: published a paper suggesting it would be possible to create
Speaker 1: light amplification by stimulated emission of radiation or a laser.
Speaker 1: The basic idea is that you have to have some
Speaker 1: sort of lasing medium. We typically would use a gas
Speaker 1: or a crystal. Something like a ruby laser actually uses
Speaker 1: ruby crystals to do this. This is a material that
Speaker 1: will absorb energy, typically either light or heat than As
Speaker 1: it does so, the electrons and the material are excited
Speaker 1: to higher energy states than their normal rest state. Now,
Speaker 1: this cannot continue indefinitely, and eventually the electrons will decay
Speaker 1: to a lower energy state, and those electrons, when they
Speaker 1: returned to their nor will energy state have to get
Speaker 1: rid of that excess energy. You can't just pump energy
Speaker 1: into electron, push it to a higher energy state and
Speaker 1: then it comes back down without getting rid of that
Speaker 1: energy and has to admit it somehow. So they shed
Speaker 1: that excess energy in the form of photons or particles
Speaker 1: of light. Now those photons are not necessarily within the
Speaker 1: visible spectrum of light. You can create stuff like infrared lasers,
Speaker 1: for example, which are invisible to the naked eye. But
Speaker 1: the full technical details of lasers get way more complicated
Speaker 1: than this, But it's a pretty good basic explanation of
Speaker 1: what's going on and what Dr Hall was trying to achieve.
Speaker 1: Only he was trying to do it with semiconductors, which
Speaker 1: no one had done yet to that point. All the
Speaker 1: ones that had been used had used flash arc lamps
Speaker 1: and other big pieces of equipment, but not semiconductors. So
Speaker 1: how did he do it well. I'll talk a little
Speaker 1: bit about that in just a second, but first let's
Speaker 1: take another quick break to thank our sponsor. Now, the
Speaker 1: first functioning laser debut in nineteen sixty and was the
Speaker 1: work of Theodore H. Meiman at Hughes Research Laboratories, but
Speaker 1: early lasers did not use semiconductors. Hall would be pioneering
Speaker 1: new ground, and he himself was skeptical at first. He
Speaker 1: felt that optical efficiency of diodes was not nearly efficient
Speaker 1: or powerful enough. But Hall was intrigued and began to
Speaker 1: explore the possibilities, and as he researched lasers, he began
Speaker 1: to theorize away he might actually make a semiconductor injection
Speaker 1: based laser. He would need to create a gallium arsenid
Speaker 1: diode and have special mirrors to create this actual laser.
Speaker 1: And he went to his bosses and he had this request.
Speaker 1: He said, hey, can I make a team and work
Speaker 1: on this project. He had absolutely no practical application for lasers.
Speaker 1: He didn't think of anything that they could actually use
Speaker 1: whose lasers for. But he thought it would be quote
Speaker 1: fun to work on end quote, so he pitched it
Speaker 1: and his bosses were intrigued, so they signed off on
Speaker 1: his pet project and he got to work. After some
Speaker 1: intense research and development, Hall's small team of researchers produced
Speaker 1: a working laser using semiconductors, and they ran numerous tests.
Speaker 1: They refined their design, built a better model, and they
Speaker 1: wrote up their research. They published their work in a
Speaker 1: scientific journal. Meanwhile, at pretty much the same time, IBM
Speaker 1: announced it had created something that was almost but not
Speaker 1: quite a working laser. However, they were very close to
Speaker 1: having it ready to go, and in an unusual move,
Speaker 1: both IBM and Hall's team would be awarded a patent
Speaker 1: for the technology. Hall's friend Nick holland Niak built off
Speaker 1: of Hall's work, using diodes made from gallium arsenide phosphied
Speaker 1: in an attempt to create a light emitting diode that
Speaker 1: could emit light in the visible spectrum. So the laser
Speaker 1: that Hall had created was an infrared laser, it was
Speaker 1: not something that was visible, and he would make the
Speaker 1: first visible laser just a short while after. Hall's team
Speaker 1: demonstrated that semiconductor lasers were possible, but no one at
Speaker 1: this point knew what they would ever use lasers for,
Speaker 1: and at that time it was more about overcoming the
Speaker 1: engineering challenge and conducting various experiments to see what was possible.
Speaker 1: The lasers Hall made were primitive by today's standards. They
Speaker 1: would only operate in the temperature of liquid air, which
Speaker 1: means you had to cool them down to below negative
Speaker 1: one four point thirty five degrees celsius, the boiling point
Speaker 1: that's in between liquid nitrogen and liquid oxygen. That wouldn't
Speaker 1: make a very practical laser for most applications because imagine
Speaker 1: that you would have to carry around a laser pointer
Speaker 1: that must always be connected to a cooling device that
Speaker 1: kept everything at a ridiculously low temperature. It would be
Speaker 1: dangerous and inconvenient. In addition, Hall's team created a laser
Speaker 1: that worked in pulses. There was no real way to
Speaker 1: create a continuous laser using their approach. The team had
Speaker 1: made an enormous achievement, but would require the work of
Speaker 1: dozens more scientists and engineers to refine and improve designs
Speaker 1: to make lasers something that could find a use outside
Speaker 1: of laboratory demonstrations. As it turned out, the laser would
Speaker 1: have numerous applications. This was something the team didn't have
Speaker 1: to worry about while they were working on developing the laser,
Speaker 1: but one of the most important applications was in the
Speaker 1: field of fiber optics. A fiber optic cable is a
Speaker 1: conduit for light. It is constructed in such a way
Speaker 1: as to guide light down a pathway made out of
Speaker 1: glass without losing too much in the process, but it
Speaker 1: requires a light source with a very narrow focus. Lasers
Speaker 1: were the obvious solution to that problem. In addition, it
Speaker 1: wasn't difficult to insert patterns into laser light to represent information.
Speaker 1: This modulation made it possible to send information down a
Speaker 1: fiber optic line. Basically, the way it works is you
Speaker 1: have a computer system on one end. It takes data
Speaker 1: and then encodes that information in a way that can
Speaker 1: be transmitted via laser light down a fiber optic cable,
Speaker 1: so that data ends up modifying the laser light in
Speaker 1: some way. It might be in phase, it might be impulses,
Speaker 1: it might be lots of different ways, and the laser
Speaker 1: light then zaps down this fiber optic cable. It travels
Speaker 1: at the speed of light to its destination some other
Speaker 1: computers somewhere else, and a receiver ends up detecting the
Speaker 1: incoming laser message through the fiber optics. A decoder takes
Speaker 1: that signal and transforms it back into useful information that
Speaker 1: the computer can actually process. Haul's semiconductor laser made all
Speaker 1: of that possible. It's also the type of laser you
Speaker 1: might find in a CD layer, which my producer Tari
Speaker 1: would be very happy to hear about and her love
Speaker 1: of CDs. Another widespread application of semiconductor lasers is the
Speaker 1: barcode scanner. That's something we see in our day to
Speaker 1: day lives. Barcodes are great if you need a way
Speaker 1: to keep accurate inventory management. You just slap a barcode
Speaker 1: unique to the type of material you're working with, and
Speaker 1: you scan everything into a system to establish your inventory,
Speaker 1: and then you can scan it again whenever you need
Speaker 1: to give it away, to use something or to sell something.
Speaker 1: So let's go with a grocery store example, because I
Speaker 1: think it's something that we can all identify with. You
Speaker 1: walk it to your grocery store and you go in
Speaker 1: there to buy something real tasty. Let's say it's um
Speaker 1: spicy salsa. So you pick up a jar of your
Speaker 1: favorite brand. And by the way, and I'm being serious here,
Speaker 1: if you have a favorite brand of salsa, you need
Speaker 1: to tell me about it, because I am always on
Speaker 1: the lookout for a really good, flavorful spicy salsa. The
Speaker 1: hotter the better, but I wanted to taste good. Anyway,
Speaker 1: back to this example, more important stuff to talk about.
Speaker 1: You bring your jar of tasty salsa up to the
Speaker 1: front of the store. Maybe you go through the self
Speaker 1: checkout lane, maybe you get in lines so that a
Speaker 1: cashier does the checkout process, but either way you soon
Speaker 1: reach the point where the jar is going to be scanned.
Speaker 1: A barcode scanner uses light to shine onto a barcode,
Speaker 1: and frequently it's a laser light. Barcodes consist of a
Speaker 1: series of lines of varying with the actual vertical bars.
Speaker 1: Those lines represent a numeric code associated with the product.
Speaker 1: In this case, we're talking about salsa. So when the
Speaker 1: light shines on this barcode, the dark lines absorb some
Speaker 1: of that light. The white spaces between the dark lines
Speaker 1: reflect more of the light, and the barcode scanner isn't
Speaker 1: just emitting a laser light. There's also a photoelectric cell
Speaker 1: that detects the reflected light from a scan The cell
Speaker 1: creates a pattern of on off pulses that correspond to
Speaker 1: the bars in the barcode. This gets translated to the
Speaker 1: scanner circuits to a numeric code that corresponds with that
Speaker 1: specific product. So the salza's price pops up on the
Speaker 1: cashier and or the cash register, and the system registers
Speaker 1: that one unit of salsa is leaving the building, and
Speaker 1: that updates the inventory, and the whole process makes sales
Speaker 1: and inventory management easier now. Like I said, not all
Speaker 1: bar code scanners use lasers. Some use just led light,
Speaker 1: but most of the ones in high volume stores rely
Speaker 1: on lasers because they're reliable and their efficient. Hall ended
Speaker 1: up working on other stuff besides semiconductor lasers. He didn't
Speaker 1: just stop there. In the nineteen seventies, he worked on
Speaker 1: several research projects focused on photo voltaic technology as the
Speaker 1: United States was entering into an energy crisis at the time.
Speaker 1: Photo voltaic cells convert light into electricity directly, So there
Speaker 1: are a lot of different ways you could potentially generate
Speaker 1: electricity using light, and many of those are indirect methods,
Speaker 1: where you're using light to heat something up and using
Speaker 1: that heat to generate electricity in some way. But as
Speaker 1: I said, photo voltaics directly convert photons into electricity. Edmund Beckarel,
Speaker 1: a physicist in the nineteenth century, observed that certain materials
Speaker 1: would produce a small electric current if that material were
Speaker 1: exposed to light. Einstein himself wrote on the matter in
Speaker 1: nineteen o five, describing the nature of light and the
Speaker 1: photo electric effect. Bell Labs would build early photovoltaic technology
Speaker 1: in the nineteen fifties, and the Space Race in the
Speaker 1: nineteen sixties fueled more research and development, but by the
Speaker 1: nineteen seventies the work was focused on finding ways to
Speaker 1: alleviate the pressure of the energy crisis to actually use
Speaker 1: it for the general public and not just for very
Speaker 1: specific uses like the space race. A photo voltaic cell
Speaker 1: absorbs photons and emits electrons. Semiconductor material allows this to
Speaker 1: to turned into a useful electric current, which can be
Speaker 1: used to power all sorts of stuff or charge electric batteries.
Speaker 1: Hall would retire from General Electric in nineteen eighty seven,
Speaker 1: and his name is on more than forty patents. He
Speaker 1: won numerous awards, and he was inducted into the National
Speaker 1: Inventors Hall of Fame in nine. As I said at
Speaker 1: the top of the show, he passed away on November seven,
Speaker 1: twenty sixteen, at the age of ninety six. But I
Speaker 1: also said the New York Times, which had interviewed Hall
Speaker 1: back in two thousand twelve in preparation for his obituary,
Speaker 1: you know, the one he didn't need yet because he
Speaker 1: hadn't died yet. The death business is weird, guys, Anyway,
Speaker 1: The New York Times didn't hear of Hall's passing for
Speaker 1: nearly two years, only learning about his death when a
Speaker 1: researcher was updating that pre prepared obituary and seeing that
Speaker 1: now it's actually been nearly two years too late, And
Speaker 1: then they ran the obituary for a man who had
Speaker 1: been dead for nearly two years. Because this world is crazy,
Speaker 1: but tech Stuff salutes Dr Robert in Hall, whose work
Speaker 1: made things like fiber optics, CD players, and laser pointers possible,
Speaker 1: among numerous other things. His contributions to engineering were significant,
Speaker 1: and throughout his life he considered himself an experimental scientist,
Speaker 1: which is pretty darn cool. If you guys have suggestions
Speaker 1: for topics I should tackle in future episodes of tech Stuff.
Speaker 1: Maybe it's a technology or a company or a person
Speaker 1: in tech. Let me know. Maybe there's someone you would
Speaker 1: want me to interview or have on as a guest host.
Speaker 1: Send me an email. The addresses tech Stuff at how
Speaker 1: stuff works dot com, or drop me a line on
Speaker 1: Facebook or Twitter. The handle of both of those is
Speaker 1: tech stuff hs W. Remember to follow us on Instagram
Speaker 1: and you can go to twitch dot tv slash tech
Speaker 1: stuff to watch me record these shows live streaming over
Speaker 1: the internet, mistakes and all. You can also watch me
Speaker 1: yell at my producer for no good reason. I abuse
Speaker 1: use her every time we come into the studio. Thanks Torii,
Speaker 1: and I'll talk to you guys again really soon. For
Speaker 1: more on this and thousands of other topics. Is it
Speaker 1: how stuff works dot com