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- Frank Makinson on How do we know light is electromagnetic radiation?
- 財布 日本 on Adam and Eve…and Steve: genetics as an evolutionary clock
- How do we know light is electromagnetic radiation? | A Posteriori on The inner life of lasers
- What’s below absolute zero? | A Posteriori on The inner life of lasers
- Andreas on Mind Reading: Theory of Mind
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Visible light lies on a spectrum of electromagnetic radiation sandwiched between longer wavelengths like radio waves, microwaves, and infrared light, and shorter wavelengths like ultraviolet light, x-rays, and gamma rays. But there’s nothing about our everyday experience with light that would lead us to believe it has anything to do with electromagnetic forces. Indeed, it came somewhat as a surprise in 1864 when Maxwell calculated the speed of theoretical electromagnetic waves and found that it was equal to the speed of light! What’s more, these waves hadn’t even been demonstrated to exist! What experimental evidence led 19th century physicists to conclude that light and electromagnetic radiation were in fact the same phenomenon? Continue reading
Two days ago, IBM released a video of a boy playing with a ball—well, a molecule. You might think a molecule is hard to catch, but the boy himself is only a millionth of an inch tall! Beyond making micro-cartoons, the tools developed to manipulate the placement of individual atoms could be used to build nanotechnology for medical, industrial, and computing purposes. Continue reading
Temperature is one of the most relatable quantities from physics; we plan our weekends, cook our food, and shop for clothes with temperature in mind. From high school we know that absolute zero, the temperature at which all superatomic motion ceases, is the coldest possible temperature. Would you be surprised to learn that some systems can achieve temperatures below absolute zero? Moreover, these systems tend to be extremely hot! This leads to some counterintuitive effects—like engines with efficiencies greater than 100% and negative pressure gases—that are often cited as violations of the laws of thermodynamics. Rather than breaking physics, such systems might hold the key to dark energy. Continue reading
From salt and sugar to precious gems, crystals are highly recognizable due to their angular shapes. But did you know that what defines a crystal is not their familiar macroscopic appearance, but is instead the periodicity of their molecular structure? An interesting consequence of periodicity is the crystallographic restriction theorem, which says that crystals can only form certain shapes: for example, there is no diamond in nature shaped like a dodecahedron. Continue reading
Consider this story: Two brothers, Mike and Matt, are sharing a new iPad. When they leave the house for school, they put the iPad in Mike’s drawer. Later on, while Matt is not around, Mike sneakily decides to move the iPad under the bed. When Matt comes back to find the iPad, will he look in the drawer or under the bed? Continue reading
Most of you are probably somewhat familiar with the kidney: it is a vital organ whose primary function is to remove waste from the blood (which is excreted in urine). I spent a bit of time today reading about how the kidney does this, which I’ll summarize here. Obviously, there are many more details than what I’m going to say, but this post should provide a good first approximation of the picture. Continue reading
For over 20 years, the Hubble Space Telescope has brought scientists a wealth of data and beautiful imagery of celestial objects near and far. It has been called “the single most important instrument ever made in astronomy.” With the 23rd anniversary of its launch date (April 24, 1990) fast approaching, we take a look at the design of its optics, scientific instruments, and steering system. Continue reading
Imagine the following scenario. You work for a company that employs 10,000 people, and assigns each employee a unique ID number between 1 and 10,000. You’re at work on Saturday and need to determine the ID number of your coworker John. Since it’s the weekend, John isn’t around to ask. However, you have access to the company database, which allows you to enter an ID and see the name of the corresponding employee (but, peculiarly, not vice versa). The database is rather slow, and can only process one query per second. Continue reading
Lasers are ubiquitous in modern life. They are in our DVD players, fiber optics, printers, pointers, and bar code scanners. They are used in industry, weaponry, medicine, spectroscopy, and physics labs. But what makes a laser a laser? In this post, I’ll explain what a laser is, how they work, and share a few facts about different lasers in use today. Continue reading