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Here on Earth, we hear about the environmental problems that littering can cause. What about littering in space? The problem may not seem very important because, frankly, we don’t spend much time in space (if any) compared to on Earth. Also, space is quite a vast space, for lack of a better word, and it seems very insignificant to have some debris let loose from a spacecraft. However, the “space junk” problem is getting worse as time goes on (debris from several space vehicles does add up), and as long as nobody does anything about it, the problem has the potential to become a major hinderance to space travel and research.

A model of space debris populations around Earth.

What kinds of problems could debris in space cause? They travel at speeds on the order of tens of thousands of miles per hour, which means that debris of any shape, size, and form will be destructive if it collides with a satellite or space shuttle. Collisions with space debris isn’t unheard of. Also, they could delay space launches if it is known that a large cloud of debris is hovering directly over the launch pad.

Space debris comes from a variety of sources. Nuts and bolts could become loose and float away from spacecraft during normal operation. When rocket stages (or segments) separate in space, they release debris. Also, in-space collisions between satellites, while rare, will create large-sized debris – the same goes for intentional spacecraft destruction, such as the Chinese anti-satellite test that was conducted a few years ago. Some of these events unleashes several thousand pieces of debris, most of which are tiny (less than an inch in size) and are much more difficult to track than larger-sized debris.

Over the past few decades, scientists and engineers have brainstormed possible solutions to decreasing space litter. However, all of the ideas have been technologically and/or economically infeasible. This could change as time goes on, especially as technology advances and/or the cost of launching a vehicle into space decreases. One possible solution is launching a garbage-collecting spacecraft to do just that, but what to do with the collected garbage is a problem. Another solution is somehow colliding objects with the orbiting debris in an effort to reduce their energy enough so that they fall into the Earth’s atmosphere (due to gravity) and burn up, but no one has thought of a feasible means to do that.

(Image from Wikipedia)

Categories: In the News, Science, Uncategorized
Tags: Environment, Litter, Space, Unsolved
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One of the most revolutionary kitchen tools we have today was accidentally discovered and then invented in the 1940s and ’50s. The microwave oven, whose origins has nothing to do with cooking, dates back to World War II. According to IdeaFinder.com:

During World War II, two scientists invented the magnetron, a tube that produces microwaves. Installing magnetrons in Britain’s radar system, the microwaves were able to spot Nazi warplanes on their way to bomb the British Isles…. The idea of using microwave energy to cook food was accidentally discovered by Percy LeBaron Spencer of the Raytheon Company when he found that radar waves had melted a candy bar in his pocket. Experiments showed that microwave heating could raise the internal temperature of many foods far more rapidly than a conventional oven.

So, what exactly is a microwave, and are microwave ovens safe? We’ll need to consider the electromagnetic spectrum, something you’ve probably seen in your high school physics and chemistry classes.

The Electromagnetic Spectrum

Put simply, a “micro”-wave is a “small” wave that is on the order of 1 centimeter, not on the order of 1 micrometer, as the name would suggest. That is, these waves have wavelengths of about 1 centimeter. (A centimeter, or cm, is 1E-2 m.) When we compare this with visible light, which is on the order between 1E-6 and 1E-7, we see that microwaves are longer than visible light. If we remember that speed of light = (frequency of the wave)*(wavelength of the wave), where the speed of light is about 2.9979E8 m/s, then we can see that frequency is inversely proportional to the wavelength. What this means is microwaves travel at a lower frequency than visible light. (Frequency is measured in cycles per second, or Hertz.)

Again, from IdeaFinder.com:

[Microwaves] are found in the non-ionizing portion of the energy spectrum, between radio waves and visible light. “Non-ionizing” means that microwaves do not detach charged particles and produce atoms with an unbalanced plus or minus charge. Microwaves can therefore safely produce heat and not cause food to become radioactive.

Now, let’s take a look at a few practical things about microwave ovens, like why radiation doesn’t escape into the kitchen, or is it safe to stop the microwave and reach in to grab the piping hot HotPocket about eat it right away? If you notice that there is a metal mesh screen in the door of the microwave. The side of the holes, on the order of half a centimeter or so, allows the physically smaller visible light waves to pass through but prevents the “larger” microwaves from leaving the microwave oven (remember that light waves are orders of magnitude smaller than microwaves). Also, you don’t need to worry about residual microwave radiation from the microwave oven because these waves always travel at the speed of light and will have been absorbed into your food long before it gets a chance to escape and hit you in the face.

More information on the history of the microwave oven can be found at Gallawa.com. Image from ScienceProg.

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Tags: Cooking, Microwave, Oven, Waves
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Sometimes engineers and scientists are faced with a problem that is not easily solvable with an algorithm that leads to a definite answer. Perhaps the problem is very complex and has many components to it, or the inputs to the problem are not constant and could vary. When faced with a situation like this, Monte Carlo simulation is the way to go.

The basic gist of how Monte Carlo simulations work is that you randomly select inputs, perform calculations on the randomly-selected inputs, and collect the outputs. This process is repeated several times (perhaps thousands, tens of thousands, or even more! As with any statistical sample, the more, the better), and in the end, all the outputs are gathered together and analyzed. To randomly select inputs, you’ll need to specify boundaries for which inputs can be selected from. A statistical model can help with this, such as a Gaussian distribution, which is a fancy term for the familiar “bell curve.” As for the aggregated outputs, statistical analysis would make sense in order to make sense of thousands of data sets. Basically, statistics is a useful tool that compliments the Monte Carlo technique. Also, generally computers are used to perform a Monte Carlo simulation due to the large number of repetitive calculations required.

This is what a bell curve looks like.

Monte Carlo simulations can be used in space sciences. For example, if one wants to analyze the risk of failure of a spacecraft in orbit, one can perform a Monte Carlo simulation with random inputs for how the spacecraft begins its orbit (speed, physical orientation, etc.), since that state cannot be predetermined accurately and instead can be modeled statistically. Then, the laws of orbital mechanics can be applied to the inputs to produce outputs that can be analyzed later. A more simple example of where the Monte Carlo method is used is the classic game of Battleship. Initially, a player would randomly guess locations for where a battleship is located. After the player scores a hit, the player would follow an algorithm (guess points that are in line with the hit) to sink the battleship (the outcome).

(Image from Wikipedia)

Categories: Science, Uncategorized
Tags: Monte Carlo, Simulation, Statistics
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