Science on This Day: December 19 | Personal Computers, the Speed of Light and Nuclear Electricity
December 19 provides a great opportunity to explore three very different areas of science and technology. In the 1970s, the Altair 8800 helped bring personal computing into the hands of hobbyists and aspiring programmers. Physicist Albert A. Michelson, born on this date in 1852, developed precision instruments that helped scientists measure the speed of light and investigate the nature of light itself. And just one day later, in 1951, a nuclear reactor in Idaho generated the first usable electricity from atomic fission.
These stories connect computer science, physics, engineering and energy production. They also offer a useful theme for middle and high school science lessons: scientific progress often comes from developing new tools, testing ideas carefully and finding practical ways to apply scientific knowledge.
December 19, 1974: The Altair 8800 helps launch the personal computing era
Imagine buying a computer that arrives as a kit, has no built-in screen or keyboard, and requires you to enter instructions using switches on its front panel. For many people today, that sounds more like an electronics project than a computer. Yet in the 1970s, machines such as the Altair 8800 helped make personal computing a realistic possibility for hobbyists and technology enthusiasts.
The Altair 8800 was developed by MITS, a small company based in Albuquerque, New Mexico. Its design was led by engineer Ed Roberts and centred on Intel's 8080 microprocessor. A microprocessor is a small electronic chip that carries out the processing instructions needed for a computer to operate. By building a computer around one of these chips, MITS could offer a machine that was much smaller and more affordable than many computers previously available.
The Altair's defining moment came with the January 1975 issue of Popular Electronics, which featured the computer on its cover. That issue went on sale in December 1974, helping explain why the Altair is associated with events around December 19. The computer's exact release date is described differently by some historical sources, but the magazine feature and the orders that followed were crucial to its success.
The basic Altair was sold as a kit for users to assemble. It did not come with the familiar keyboard and monitor arrangement we associate with computers today. Instead, users could enter binary instructions using switches on the front panel and read the output through lights. It was a machine that encouraged owners to experiment, understand the hardware and add components to extend its capabilities.
The computer attracted far more interest than MITS had initially anticipated. Its relatively low price and expandable design helped create a market for computers that individuals could own and develop themselves. Hobbyist groups and computer clubs began sharing ideas, software and hardware improvements. The Altair helped inspire a wider personal-computing movement that would soon include companies such as Apple and Commodore.
The Altair also played an important role in the history of Microsoft. Paul Allen and Bill Gates recognised that the machine needed accessible programming software. They developed a version of the BASIC programming language for the Altair, which became one of the company's earliest products. Their work helped demonstrate that the future of computing would depend not just on hardware, but also on the software people could use to make computers perform useful tasks.
The Altair was not the first computer designed for individual use, and it was certainly not as convenient as a modern laptop. Its importance was that it helped establish a commercially successful market for personal computers and encouraged a generation of people to learn how to programme and build their own technology.
Classroom connection: What makes a computer a computer?
The Altair is a useful starting point for exploring computer hardware and software. Students can investigate the roles of a processor, memory, input devices and output devices, then compare the Altair's switches and lights with the touchscreen and display of a modern phone.
A simple activity could involve representing numbers using binary. Students can use a sequence of 0s and 1s to represent a number, then investigate how computers use binary information to store and process data. Older students could explore how programming languages such as BASIC made computers more accessible by allowing people to write instructions without entering every machine-level command directly.
A discussion question to try is: Would you rather own a computer that is easy to use but difficult to modify, or one that is challenging to learn but allows you to change almost everything? This can lead to conversations about accessibility, flexibility and the relationship between technology and its users.
December 19, 1852: Albert A. Michelson is born
Albert Abraham Michelson was born on December 19, 1852, in Strelno, then part of Prussia and now in Poland. He became one of the most important experimental physicists of the late nineteenth and early twentieth centuries, particularly through his work on the measurement of light.
Light travels incredibly quickly. In a vacuum, its speed is approximately 299,792 kilometres per second. Measuring this speed accurately is not straightforward because light travels such a large distance in a very short time. Scientists therefore need carefully designed experiments and instruments capable of detecting extremely small differences.
Michelson became well known for improving methods of measuring the speed of light. He developed and refined optical instruments that allowed light to travel along controlled paths before being compared with itself. One of his most important contributions was the Michelson interferometer.
An interferometer works by splitting a beam of light into two separate paths. Mirrors direct the beams along different routes before they are brought back together. When the light waves recombine, they produce an interference pattern. Depending on how far each beam has travelled, the waves can reinforce or cancel one another. Even a very small change in the distance travelled can shift the pattern, allowing precise measurements to be made.
This technique became important well beyond measuring the speed of light. Interferometers are used in many areas of modern science and engineering, including astronomy, optical testing and the detection of extremely small changes in distance. The same broad principle of measuring tiny changes through interference is also used in gravitational-wave observatories, although these instruments are vastly more sophisticated than Michelson's original equipment.
Michelson is also remembered for the famous Michelson–Morley experiment, conducted with chemist Edward Morley in 1887. At the time, many physicists believed that light waves travelled through a hypothetical medium called the luminiferous aether. They thought that, just as sound waves require a medium such as air, light waves might require an invisible substance filling space.
The experiment was designed to test whether Earth's motion through this proposed aether would affect the measured speed of light in different directions. Michelson and Morley used an interferometer to compare light travelling along two perpendicular paths. If the expected effect existed, they anticipated detecting a change in the interference pattern as the apparatus was rotated.
They did not detect the expected change. This was a null result, meaning that the experiment failed to find the effect the researchers had predicted. Rather than being scientifically useless, the result became one of the most important experimental challenges to the aether hypothesis. It contributed to a wider shift in physics that eventually led to a new understanding of space, time and the behaviour of light.
It is worth avoiding the oversimplification that Michelson and Morley single-handedly disproved the aether or directly produced Einstein's theory of relativity. Their experiment was part of a longer process involving many scientists and theoretical developments. Einstein's special theory of relativity, published in 1905, provided a framework in which the results could be understood without the need for a luminiferous aether.
Michelson received the 1907 Nobel Prize in Physics for his optical precision instruments and the spectroscopic and metrological investigations carried out with them. He was the first American scientist to receive the Nobel Prize in Physics.
Classroom connection: When an experiment finds nothing
Michelson's work is an excellent way to introduce wave interference, precision measurement and the importance of experimental design. Students can investigate constructive and destructive interference using water waves, sound waves or simple simulations. They can then consider how an interference pattern can reveal a change that would otherwise be difficult to measure.
The Michelson–Morley experiment also provides a valuable discussion about unexpected results. Ask students: If an experiment does not produce the result scientists expected, has the experiment failed? They can consider whether the equipment worked, whether the measurements were sufficiently precise and whether the original explanation needs to be reconsidered.
This is an important part of understanding how science works. An experiment does not have to confirm a prediction to be useful. Sometimes a result that contradicts expectations provides the strongest reason to investigate an idea further.
December 20, 1951: A nuclear reactor generates electricity for the first time
The third event takes us from computers and optical instruments to one of the most important applications of nuclear physics: generating electricity.
On December 20, 1951, the Experimental Breeder Reactor I (EBR-I) in Idaho, United States, became the first nuclear power plant to produce usable electricity through atomic fission. Initially, the electricity generated was enough to light four 200-watt light bulbs. By the following day, the reactor was producing enough electricity to power the entire building.
This was a relatively small demonstration, but it marked an important milestone in the development of nuclear energy. Scientists had already demonstrated nuclear fission and investigated nuclear chain reactions. EBR-I showed that the energy released through fission could be converted into electricity.
Nuclear fission occurs when the nucleus of a heavy atom, such as uranium, splits into smaller nuclei. This process releases energy, along with additional neutrons. Under the right conditions, some of those neutrons can cause further fission reactions, creating a controlled chain reaction.
In a nuclear power station, the energy released through fission is used to heat a coolant. That heat can then be used to produce steam, which drives a turbine connected to an electrical generator. The generator converts mechanical energy into electrical energy.
EBR-I was an experimental breeder reactor. A breeder reactor is designed to produce more fissile material than it consumes under particular operating conditions. This was an important area of research because scientists were investigating how nuclear reactors might make more efficient use of nuclear fuel.
It is important to distinguish this 1951 achievement from the later development of large commercial nuclear power stations. EBR-I was an experimental reactor, not a modern electricity-generating station supplying power to a national grid. Its demonstration showed that electricity could be generated from nuclear fission and helped researchers investigate the technology further.
Nuclear energy has since become an important part of electricity production in several countries. It produces large amounts of electricity without directly releasing carbon dioxide from the fission process, although nuclear power also raises important questions about radioactive waste, safety, construction costs, fuel supply and the management of nuclear materials.
Classroom connection: Where does the energy go?
EBR-I provides a practical way to teach energy transformations. Students can trace the energy pathway in a nuclear power station:
Nuclear energy → thermal energy → kinetic energy of steam → mechanical energy in a turbine → electrical energy from a generator.
Ask students to identify where energy is transferred and transformed, and to explain the role of each component. This can be compared with a fossil-fuel power station, where chemical energy is released through combustion, or a wind turbine, which converts the kinetic energy of moving air into electrical energy.
For older students, the topic can lead into discussions about the advantages and disadvantages of different electricity-generation methods. Rather than asking students to decide whether nuclear power is simply good or bad, encourage them to compare reliability, emissions, waste, safety, land use and cost. This makes the activity a useful opportunity to combine scientific understanding with evidence-based argument.
Connecting the three events
At first glance, the Altair 8800, Michelson's interferometer and EBR-I might seem to have little in common. One helped launch the personal computing era, another transformed precision optical measurement, and the third demonstrated a new way of generating electricity.
However, all three illustrate how scientific knowledge can be turned into practical technology. The Altair depended on developments in microprocessors and electronics. Michelson's instruments used the wave properties of light to make measurements that had previously been extremely difficult. EBR-I applied knowledge of nuclear fission to demonstrate a new method of producing electrical energy.
These are useful examples for students because they show that science is not just a collection of facts and equations. It also involves designing equipment, testing ideas, solving engineering problems and considering how new technologies might be used.
My December Science on This Day resource set is designed to make these kinds of connections easier to bring into the classroom. It includes 132 STEM events across the 31 days of December, with an interactive HTML resource, editable presentation slides, a spreadsheet and a printable PDF. The HTML version allows teachers to filter events by date and subject, select items for classroom use and display them with discussion questions.
The slides are useful for introducing an event as a quick warm-up, while the spreadsheet
and PDF provide alternative ways to browse the calendar.
What else happened in science during December?
There are several more opportunities to connect science history with classroom topics as the month continues.
On December 21, 1968, Apollo 8 launched on the first crewed mission to travel to the Moon and enter lunar orbit. The mission is a great opportunity to explore orbital mechanics, rocket engineering, navigation and the challenges of human spaceflight. Students can investigate how spacecraft use gravity to travel between Earth and the Moon, and why reaching lunar orbit requires careful planning.
On December 24, 1968, astronaut William Anders took the famous Earthrise photograph during Apollo 8's journey around the Moon. The image shows Earth rising above the lunar horizon and has become one of the most recognisable photographs in the history of space exploration. It offers a useful connection to astronomy, photography, observation and the way scientific images can influence how people think about our planet.
On December 25, 2021, the James Webb Space Telescope launched from French Guiana aboard an Ariane 5 rocket. Webb was designed to observe the Universe primarily in infrared light, allowing astronomers to investigate distant galaxies, stars, planetary systems and objects hidden within clouds of dust. Its large segmented mirror and complex deployment in space make it an excellent example of modern engineering and international scientific collaboration.
If you are exploring space science with students, my free Jupiter's Moons resource set includes an infographic, slides, a podcast and a quiz. For a more substantial classroom activity, the Space Exploration reading comprehension resource provides a way to explore the science and technology behind space missions.
From the early days of personal computing to the precision measurement of light and the first electricity generated by a nuclear reactor, December 19 and 20 offer plenty of ways to connect scientific discoveries with the technologies students encounter today. These events are reminders that scientific progress often begins with a question, a carefully designed experiment or an idea that someone is willing to build and test.
Thanks for reading
Cheers and stay curious
Oliver - The Teaching Astrophysicist
