The Way of Waves
With the exception of sending men to the Moon in the 20th Century (1969-1972), everything we know about the Universe beyond the Earth comes to us in the form of waves, and primarily the electromagnetic spectrum, or in other words, light waves. Even the information we get back from remote spacecraft that visit other worlds within our Solar System transmit that information back to us in the form of radio waves, the longest wave in the electromagnetic spectrum. Waves are a fundamental, or basic way that energy travels from one location to another.
1. Waves have a basic structure. Imagine you and a friend are playing with a jump rope. Draw a simple picture of you and a friend making a bunch of waves with a jump rope. Your rope should have evenly spaced “wiggles” as it moves up and down from you to your friend.
2. Now draw a straight line from the bottom of one of the wiggles to its top and label this amplitude (height of the wave). Now draw a straight line from the bottom (trough) of one of the wiggles to the bottom of the next wiggle and label this wavelength (self-explanatory). Frequency is how often a wiggle happens. Frequency is a measure of how many waves from trough to trough (or crest to crest) happen per second and is known as a hertz cycle (Hz). The height of a wave wiggle (amplitude) and how often they happen (frequency) is related to how much energy a wave has.
Waves that move along ropes and waves that move though water (tsunami!), the ground (earthquake!) or air (sound!) are travelling through a medium, or matter that carries the wave. But light, which also travels as a wave does not move through any medium. It just waves itself, which is a fundamental property of light that baffled scientists in the 19th Century and is still not completely understood today.
You learned that the Sun emits the full electromagnetic spectrum. The means that the Sun and other stars as well, emit light in a wide range of amplitudes, wavelengths and frequencies all at once or sometimes selectively. Because we have measured the properties (amplitude, wavelength and Hz) of the light waves that are emitted by all kinds of matter on Earth (Your body glows in infra-red waves, which is heat, even though you can’t see it!) we can analyze the electromagnetic spectrum of the Sun and stars and know what matter is emitting any and all particular light waves. Astronomers hooked up a type of etched glass to their telescopes (spectroscope) in the late 19th Century and were able to filter out all the different frequencies of light coming from the Sun and stars and found they had discovered a gold-mind of data! Now they knew what kind of matter (elements in the case of stars) that were inside the Sun and stars! A spectroscope is just a fancy prism if you know what those are. Or you may have seen a rainbow when raindrops bend the light from the Sun and split out all the different frequencies of white-light that we see as the colors of the visible part of the Sun’s electromagnetic spectrum. Recall that our eyes are tuned to see light in the nanometer range (that’s a billionth of a meter), but the Sun and stars carry frequencies of light from radio to gamma range even though our eyes aren’t tuned to see those particular waves. Recall also that light travels at 300,000 km/sec. (180,000 miles per second!!) so we can know about stars that are extremely far away from us. But don’t forget that it still, in some cases, took billions of years for that light to reach us, which is strong evidence for the ancient age of the Universe.
Finally, you may have heard the big hullabaloo about 7 earth-like (terrestrial or rocky inner world) exoplanets that were discovered a few years ago and announced in the news in February of 2017. With modern precision telescopes astronomers can measure the periodic (cyclical-timed ) dimming of the light around stars that indicates a planet is moving in front of the star. Using basic laws of gravity they can determine the mass and distance of the exoplanets from their parent star, and they can analyze the light spectrum from the parent star to determine how much energy falls on the planet. If the energy falling is similar to that we get from our Sun’s energy falling on Earth (Goldilocks Zone), scientists start to get excited about the possibilities of discovering a potentially habitable world. You might have even heard the misreport (I did) in some cases that liquid water was discovered on these exoplanets. But that was a mistake in reporting (no, it wasn’t fake news, just a misunderstanding). If we can very precisely analyze the light coming from the star through an exoplanets atmosphere (really hard to do, but possible as long as the exoplanet lies in a straight line from our eye to its parent star ) we can determine what makes up that atmosphere. We’d obviously love to find water vapor because that would indicate water was possibly evaporating from the surface of an ocean. And you have learned that where there is liquid water there is a good possibility that life might be there as well. Remember that simple life like microbes is far more likely than anything more complex, let alone intelligent life as found on Earth. In the next few years astronomers will have a new space telescope that will float free of the distortions of Earths atmosphere and will have a spectroscope on board. So they will have the ability to analyze these 7 exoplanets and possibly discover if they have an atmosphere and what constituent chemicals they might contain. Keep your fingers crossed, but keep in mind that these planets could be more like Mercury, Venus or Mars. Remember even though we call those planets terrestrial, Earth-like they are not. There’s so much that goes into the making of such a spectacular planet such is Earth. And heck, even if we do find water on these world, they are 40 light-years away. If you got into our fastest spacecraft and could carry enough supplies and be shielded from the dangers of space, you could expect to arrive in just under 1 million years! Better get a head-start now and hope they find water!
3. On a separate sheet of paper define the bold terms. Don’t staple it to this paper, just keep it behind this page in your binder and give it the same number.