For those of you that are already experts in physics and engineering, you will most likely find this blog a bit elementary for you. Nonetheless, I’m writing it because I routinely get asked questions similar to this one on a daily basis. Many see a bit of contradiction. For example, the stars in the sky are clearly very far away and millions of light-years and the visible and non-visible radiation still seem to make it all the way to us on earth, yet it seems that some radios die out quickly even when there aren’t any obstacles in the path.So the short answer is that all of these waves, unless they run into something and get absorbed or scattered will theoretically go on forever at the speed of light. However, it is important to look at the relative energy of these waves. One of the key laws to the world of physics is the conservation of energy. There is a fixed amount of energy in the universe - you can’t make more, you can’t get rid of it, but you can change it from one form to another. Of course for most of you, this will cement the fact that these electromagnetic waves, unless they run into something will go on forever. And while we know that there is lots of stuff out there in the universe, it sure appears that there is a whole lot of empty space. Obviously that doesn’t tell the whole story.
Drop a pebble into a pool of water, the wave will extend away from the point of impact in a nice circle. As the wave gets farther from the center, the circle obviously gets bigger. In getting bigger, the energy in the wave is spread out over an ever expanding area. For the sake of the discussion, we will assume there is no impact to due to external forces so the energy of the whole wave remains the same. If we had an infinitely large pond of perfectly still water with a constant depth, the wave resulting from the pebble would technically go on forever in all directions. However, in doing so the magnitude (e.g. size) of the wave would get smaller. Unfortunately, the stone in water example is only two-dimensional. Electro-magnetic waves operate in three dimensions so we need to extend the metaphor a bit.
When we look at an ideal radiator of electromagnetic waves, we need to think isotropically. This means waves extending out equally in all directions from a point (a.k.a. a sphere). A good example might be a star like our very own sun. Just like the circle in the water, the electromagnetic energy spreads as the wave gets farther away, just like the surface area of a sphere. From our basic geometry we know that the surface area of a sphere of radius r is 4πr2 ; hence as we get farther from the transmitter, the power in the waves get “stretched” accordingly meaning that the resulting strength of the signal at any point is INVERSELY proportional to the square of the distance (r) from the transmitter (1 / 4πr2). It gets very small, very quickly, but never really gets to zero. This is often referred to as an inverse square law - as you know, gravity also works this way.
From home enthusiasts to workers on the manufacturing floor, everyone's imagination is captured by the potential of 3D printing. Prototyping, spare parts creation, art delivery, human organ creation, and even mass product production are all being targeted as current and potential uses for the technology.
Solar and wind energy are becoming more viable as a source of energy on the electric grid. For decades, the major drawback to solar and wind was that they’re temperamental. A cloudy day kills solar and a still day renders the wind turbines useless. Automation tools, however, are providing a path to help these renewables become practical.
In honor of Earth Day, the National Security Agency has launched the STEM Recycling Challenge in Maryland schools to encourage kids to think about where the garbage they throw out every day actually goes. The agency has also introduced “Dunk,” a muscular blue cartoon recycling bin wearing shorts and sneakers.
Samsung's Galaxy line of smartphones used to fare quite well in the repairability department, but last year's flagship S5 model took a tumble, scoring a meh-inducing 5/10. Will the newly redesigned S6 lead us back into star-studded territory, or will we sink further into the depths of a repairability black hole?
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