Brady Haran, YouTuber extraordinaire, recently returned from a trip to the European Southern Observatory in Chile. He talks about all six days on his blog, so I won't mentioned everything he did. But I did watch the first video he posted from there on his channel Deep Sky Videos - The Green Flash!
I have to confess that I did not know that there was a actual green flash phenomenon. I thought it was something created by Disney for Pirates of the Caribbean: At World's End. Turns out that it's real and it makes a lot of sense when you think about it. As the sun approaches the horizon it has to pass through more atmosphere. This added air acts like a lens that distorts the light. Consequently it creates an illusion of the edge of the sun separating and turning green. I dug around and found a good resource on green flashes by Andrew Young. It's really a cool thing that I would love to see it for myself.
Learning about the green flash got me thinking about other natural phenomenon. St. Elmo's fire came next to mind.
Returning to the sun for a minute, I've heard of Sundogs before and even seen them and so wanted to make mention of them here.
Similar to an after effect of a lens flare, sundogs are the result of when light from the sun is broken up by before it gets to your eye. In a lens flare the light source is scattered as it passes through the lens. With sundogs the light is split by ice crystals in the air. The reason why sundogs don't show up every time it's cold enough for ice to form is that the crystals must be aligned so as to be horizontal to the viewing angle. Because of the specificity of the crystals, it produces a very distinct effect, two (or sometimes more) "phantom suns" that are equal distances from the sun. The same crystals also can form a halo around the sun in the same fashion. Again, this phenomenon generally occurs when the sun is near the horizon. The website Atmospheric Optics has some excellent photos and explanations about different visual phenomenon.
While rarely a mystery, I want to mention the Aurora borealis and Aurora australis. The northern (and southern) lights are a result of solar radiation hitting the upper atmosphere. They can be a variety of colors and are a common subject of photos. They've been studies extensively and there is lots of information you can find about them. I mention them here because I actually had a chance to see the lights while at my parents house in northern Utah. They were a faint green glow in the northeast sky, but while not being spectacular it was a great novelty. I don't have a bucket list, but if I did "see the northern lights" would have been on it.
I'll end with an occurrence that I've seen a time or two and, like the green flash, is due to the atmosphere. There are all kinds of things that can make the moon look different colors, including particles in the air (from fires, industry, etc), as well as the moon's light coming through thick layers of atmosphere (such as moon rise and moon set). I had to share this from Wiki Answers as I was doing research on this - The answer someone's question of "Why is the moon red?" Answer: "It is NOT." I've never considered Wiki Answers as credible research - Now I really don't trust them. The most established change in the moon's color is during a lunar eclipse. Red moons come from sun light reflecting off of the moon and shining through the Earth's shadow. Earth's shadow has a reddish tint to it because our atmosphere bends light around it, the red light being the most penetrating and thus infusing the shadow while the blues and greens (and other hues) scatter out. So that is why during a lunar eclipse the moon will look red. I like this description from NASA about what it would look like if you were in a spaceship in the shadow of the Earth...
I have to confess that I did not know that there was a actual green flash phenomenon. I thought it was something created by Disney for Pirates of the Caribbean: At World's End. Turns out that it's real and it makes a lot of sense when you think about it. As the sun approaches the horizon it has to pass through more atmosphere. This added air acts like a lens that distorts the light. Consequently it creates an illusion of the edge of the sun separating and turning green. I dug around and found a good resource on green flashes by Andrew Young. It's really a cool thing that I would love to see it for myself.
Learning about the green flash got me thinking about other natural phenomenon. St. Elmo's fire came next to mind.
I first heard about it from watching a version of Moby Dick.The teacher explained that the crazy blue fire on the mast wasn't magic but rather a natural occurrence. Similar to light night it is when air is ionized during a storm (often at the end of it). It tends to collect on surfaces that discharge easily - pointed objects being a chief culprit. A perfect example of how the process works is a neon light. They both operate under the same principles of ionization. The cool thing is that ionized air is basically a plasma. And if you remember my post on the states of matter you know that plasmas are really cool. So, if it looks like your plane is burning on the wings, you might be looking at the slowest lightning you can see.
Lightning is also a pretty cool occurrence when you really think about it. I won't look too closely at it, but I will link to KXCD's blog when he answered a whole bunch of questions about it. I will also share an awesome video that you may or may not have seen before. (filmed by Tom A. Warner)
While rarely a mystery, I want to mention the Aurora borealis and Aurora australis. The northern (and southern) lights are a result of solar radiation hitting the upper atmosphere. They can be a variety of colors and are a common subject of photos. They've been studies extensively and there is lots of information you can find about them. I mention them here because I actually had a chance to see the lights while at my parents house in northern Utah. They were a faint green glow in the northeast sky, but while not being spectacular it was a great novelty. I don't have a bucket list, but if I did "see the northern lights" would have been on it.
I'll end with an occurrence that I've seen a time or two and, like the green flash, is due to the atmosphere. There are all kinds of things that can make the moon look different colors, including particles in the air (from fires, industry, etc), as well as the moon's light coming through thick layers of atmosphere (such as moon rise and moon set). I had to share this from Wiki Answers as I was doing research on this - The answer someone's question of "Why is the moon red?" Answer: "It is NOT." I've never considered Wiki Answers as credible research - Now I really don't trust them. The most established change in the moon's color is during a lunar eclipse. Red moons come from sun light reflecting off of the moon and shining through the Earth's shadow. Earth's shadow has a reddish tint to it because our atmosphere bends light around it, the red light being the most penetrating and thus infusing the shadow while the blues and greens (and other hues) scatter out. So that is why during a lunar eclipse the moon will look red. I like this description from NASA about what it would look like if you were in a spaceship in the shadow of the Earth...
The view from your cockpit window is Earth's nightside, the dark half of our planet opposite the sun. But it's not completely dark! All around Earth's limb, the atmosphere glows red. What you're seeing is every sunrise and sunset on Earth -- all at once. This ring of light shines into Earth's shadow, breaking the utter darkness you might expect to find there. Turn off the cockpit lights. There's a lovely red glow.Rather poetic don't you think?
No comments:
Post a Comment