Cosmos Computed

The visible world around us is constantly changing. One second we may have the sun in our eyes, and another we're in a dark closet trying to find the light switch. Such fluctuations in brightness could have ended up being a serious problem for our vision if it weren't for a handy built-in feature: our eyes automatically adapt to the lighting conditions of the surrounding environment. Most people are well aware that their pupils change size to handle lighting conditions. A larger pupil admits more light and makes the scene brighter, while a smaller pupil admits less light and makes the scene dimmer. This mechanism is fast and effective, and is controlled by the brain stem, which acts autonomously - you don't even have to think about it. As useful as this type of adaptation may be, it has some limitations. For example, most artificial lighting is 20 times dimmer than the sun, while pupil dilation only brightens light by a factor of 4 (when compared with a fully constricted pu...

A bright star streaks across the sky, leaving behind a glowing trail that soon fades back into the blackness of the night sky, leaving no perceptible trace. A minute later, another streak appears; this one has faint hues of pink and orange. Each streak lasts only a couple seconds, but its quiet beauty is not easily forgotten. Maybe I could write a kid's book about it: Fast star, slow star Red star, blue star The sight I'm describing is called a meteor (as I'm sure you already know). Meteors have been observed for as long as humans have existed, and have been a mystery for almost as long. It didn't take long to figure out  that they occurred high in the atmosphere - in fact, the name "meteor" was originally used for any atmospheric event - but it wasn't until the 19th century that somebody finally realized what they actually were: small bits of space debris burning up as they fell through the sky. The question that naturally comes next: how does a meteor ge...

Here's a simple physics puzzle: suppose you're launching a model rocket. You want the rocket to go as high as possible. Is it better to design the rocket to: A. Use all of its fuel very quickly, and then use its momentum to travel high B. Use the fuel gradually over the whole duration of the flight In other words, what is the fuel consumption rate that will maximize the height of the flight path? For this problem, we can assume that the thrust is proportional to the fuel consumption rate. I'll try to post a solution to the problem in the future. New posts every month - subscribe for free !

Imagine the universe is filled with water. Instead of empty space, every inch of it contains pure water. No planets, no stars, only water. What happens? And what would happen if an air bubble formed? The answer to this question requires a basic understanding of gravity. Gravity is very important. It helps hold matter together, bends light, and distorts space-time (which, incidentally, is how it bends light). It also makes it possible to play football, and as Americans are big football fans, they would certainly agree that we couldn't live without it. Unfortunately, many Americans don't understand how gravity works. Admittedly, scientists haven't figured out a lot of things, but we do understand it well enough to make predictions and model physical events. One of the important things about gravity is that its strength is proportional to the inverse of the square of the distance. In other words, it gets weaker as you get farther away, based on the equation: F = c/d 2 where c ...

Near the end of last month, the moon passed entirely through Earth's shadow, resulting in a full lunar eclipse. The moon didn't completely black out, due to sunlight scattering through Earth's atmosphere. Instead, the moon had a dim reddish-brown glow. Of course, I took I lot of photos of this celestial phenomenon. I started taking photos during totality. I kept taking photos a couple times per minute, for a period of about 1.25 hours, until the moon was fully lit. My goal was to put the photos together, for an animation of the moon passing through the shadow of the Earth. "Fake" crescent One thing I thought was pretty neat was when the partial lighting of the moon formed a perfect crescent. The crescent looked a lot like the waning crescent phase of the moon, but there was something strange about it. It reminded me of the artificial images of the moon that you'll see when you use a star-mapping program. The reason is this: for a real crescent moon, the lighti...

The Perseid meteor shower is coming up! After midnight on Tuesday, and again on Wednesday, an observer under a dark sky may see up to 100 meteors per hour - an average of nearly 2 per minute. If you live in a city, the light pollution will wash out most of the meteors, so the countryside or mountains will be a much better place to watch them. Meteors start as small bits of material floating in space, usually dropped from comets that passed through the area. At this stage, they are called "meteoroids". When the earth passes through a cluster of these particles, they hit our atmosphere and burn up as meteors, and we have what's called a meteor shower. If you're looking up at the sky, and you see a streak of light zip a short distance and then disappear, this is a meteor. One of the best things about this particular shower is that the moon won't come out all night, so the sky will be darker than usual - making it possible to see more meteors than in most showers. If ...

212° F Let's play a little game. I'll list a bunch of possible actions. Each action will have 2 variations, (a) and (b). You choose either (a) or (b), depending on which would be safer (or less painful). Each of the questions will involve an oven hot enough to bake a cake (350° F), and a pot of boiling water (assume we're at sea level). So... would you rather: 1.     (a) Stick your hand in the oven     (b) Stick your hand in the boiling water   ... for a period of 10 seconds 2.     (a) Leave a fork in the oven     (b) Leave a fork in boiling water   ... for a period of 15 minutes. Then hold the fork tight with your bare hand. 3. Fill a jar to the top with cool tap water. Then:    (a) Place the jar in the oven    (b) Place the jar in the boiling water   ... for a specific, but unknown, period of time. Then remove the jar and put your hand in it. First see if you can figure these out yourself. They shouldn't be too...

This morning, New Horizons became the first spacecraft to make a flyby observation of the Pluto system. During the mission, the spacecraft captured the most detailed photographs of Pluto's surface we've ever had, and possibly ever will have. It also found many new properties including size, mass, atmosphere, and surface composition. In a period of a few hours, we discovered more about Pluto than we've found in the 85 years since Clyde Tombaugh captured its first photograph. Before After  (images credit: NASA) To complete this mission, the spacecraft flew for more than 9 years through the emptiness of space. This may sound like a long time, but it's actually amazingly quick. In fact, New Horizons set the record for the fastest speed at launch, and during the flyby, the spacecraft was moving at a rate of over 30,000 mph, or roughly 50 times the speed of sound. Picture an object twice as heavy as a grand piano moving 25 times faster than a bullet from a gun. Yikes. The man...

Monosodium glutamate, commonly abbreviated MSG, is a very common chemical used to enhance flavors in food. MSG works by activating the "umami" receptors on the tongue, effectively enhancing flavors and making food taste a lot better. This is similar to the way sodium chloride (table salt) works, but MSG is much more powerful, so sodium content can be reduced by adding MSG to food. For this reason, many food companies use MSG as a food additive. Despite these apparent advantages, most people would agree that MSG is unhealthy and should be avoided. Sensitive individuals even experience negative side effects after consuming food containing MSG. But what exactly is wrong with MSG? If a person is not MSG sensitive, is it okay for them to consume it in their food? Virtual model of monosodium glutamate Before answering these questions, it would be best to start with the molecular structure of MSG. Monosodium glutamate, also known as sodium glutamate, is an ionic compound with the f...

In the realm of science, there are many things which are not fully understood. The mechanism behind the formation of a snowflake crystal is one of these things. It would seem that something so common would have been completely figured out by this time; after all, scientists have even studied atoms, the building blocks of all matter in the universe. But no, snowflakes remain a mysterious subject. So what have we figured out about snowflakes so far? They form when water vapor condenses around an ice particle, and they form six sides due to the shape of an individual water molecule. But there's still a lot we don't know. This snowflake has definite, albeit slightly imperfect, symmetry. One problem with our current knowledge is that snowflakes tend to form six-sided shapes which are symmetrical . The odds of two snowflakes sharing the same pattern is unimaginably small, and yet the snowflake itself contains 6 copies of the same pattern. Why does each arm develop the same way? Scien...

About a week ago, I was finally able to observe the second solar eclipse of my life – a partial eclipse with a maximum coverage of about 50%. The only other eclipse I have observed was another  partial solar eclipse in May 2012 . A solar eclipse occurs when the moon casts its shadow on Earth's surface. From the point of view of an observer in the shadow, the moon covers the sun. It's not always obvious when a solar eclipse is happening; if the observer is in near the edge of the shadow, so the sun is only partly covered, it might not seem like anything unusual is happening. This was my situation during the eclipse last week. The moon only covered part of the sun, so when I told one of my friends that an eclipse was occurring, he hadn't even realized it. And I don't blame him. Actually, a few minutes earlier, I hadn't realized it either. I got the time mixed up, and didn't think the eclipse had begun yet. The sunlight was weaker than usual, but I assumed that was...

If time were stopped, would this falling pen look blurry to us? Time can be a very confusing subject. It has a past, a present, and a future, but the future keeps changing and the present is always moving, while the past grows larger. Although most people think they understand time, they often get confused when they try to describe it. To help visualize and understand time, many people compare it to a very familiar concept: a line. This line, called a timeline, represents time as a whole. The current moment, or the present, is a single point which moves smoothly along the timeline. The part of the timeline behind the point is the past, and the part ahead of the point represents the future. The whole timeline, including the moving point that represents the present, is considered exactly the same for everyone. Although this whole approach may be a useful way to represent time, it is actually inaccurate in describing time. First of all, the present does not have to be experienced in the s...

What is a vitamin? I don't mean the different types of vitamins or the shops where they can be bought. I mean, what makes something a vitamin? Perhaps a vitamin is only a useless chemical that serves no purpose, and is therefore called a vitamin to make it seem useful when it really isn't. I prefer to think of a vitamin, however, as an essential chemical that our body needs to grow and survive. Unfortunately, the former definition is sometimes the more accurate one; in fact, some of the vitamins being sold today do nothing good for the human body. One example of this is vitamin B 17 . Laetrile was named a vitamin in the 1900's when Ernst T. Krebs, Jr. wanted to get around the restrictions on drugs by selling laetrile as a nutritional supplement. Some say that Krebs was a medical doctor, but he never even got a doctoral degree, except for an honorary degree from a school not accredited to award advanced degrees. In reality, Krebs was just a chemist that wanted to make money....

I recently added a "Did You Know" app to the sidebar of my blog. The app randomly picks a math/science/technology fact from a list, and displays it. I had to write the app myself (with JavaScript and HTML), because Blogger doesn't have an app like that built-in, and even if it did, I like to have control over my things. To get technical: the data is stored on Firebase. The app reads the data from Firebase, and adds it all to an array. There is no way to tell how many items there are without reading all of them from Firebase. The app then looks at how many elements are in the array (call that number  a ) and then randomly chooses a number  b from 1 to a . It then takes the b th element from the array, and displays it. (I know, I didn't have to store them all in an array, but it's easier that way.) Because of the data storage method, I can add new facts very easily: I just have to go to Firebase and add the new fact to the database. Of course, my app updates as soo...

This candle was leaning over too far, so I propped it up with a folded piece of paper. In the cold, dark months of the year, candles are more than welcome. Not only do they give off a cozy light, but they also give off heat and warmth. The trouble is that candles cost money - not only for the candle itself, but also for the candle holder. So is there an alternative to buying candles? Minneola tangelos also work well. The answer is yes: make them yourself. That might sound tough at first, but it turns out that there's a really easy way to do it - all you need is an orange and some cooking oil. Here are the steps: 1. Cut into the peel on the orange. Try not to cut into the juicy flesh, because the juice could make the peel wet and cause it to have trouble lighting. Cut all the way around the orange. You might want to have a few extra oranges in case something goes wrong. 2. Remove the peel on the side opposite the stem. The wick will be on the stem side, so you need to keep that pa...