Monthly Archives: June 2016

Why Is The Sky Blue?

Ever heard that the sky is blue because it’s reflecting Earth’s water? It’s a myth! If the sky was just mirroring the planet below, it would be brown in Utah. The real reason for our atmosphere’s hue has its roots in a more fundamental question: how do we see the world around us?

Spectrum

The electromagnetic spectrum. Credit: Florida Atlantic University

Human eyes are living light detectors. Color is just our brain’s code for incoming energy level. We call the most energetic light we can see “purple” and the least energetic “red”.

Our built-in biological cameras have a quirk: when confronted with a mixture of colors all at once, they’re overstimulated. Our eyes can’t resolve a blend of energy levels into individual signals, so our visual processing system defines a new category, which we call “white”. The sun’s radiation appears white before it reaches Earth, but it’s really a combination of many colors.

SunFromISS

The sun & Earth as seen from the ISS. Since sunlight hasn’t been scattered by the atmosphere on its way to the camera, it appears white. Credit: NASA

As white sunlight enters the atmosphere, the transition from empty space to air affects each of its components differently. Blue-violet light is bounced around the most drastically by air molecules in its path. From our perspective on Earth’s surface, scattered blue radiation fills the sky. Lower-energy light, which we interpret as the colors red through green, travels more directly downward to our eyes. We interpret this smaller combination — white minus blue-violet — as pale yellow.

Rayleigh-Scattering

Image courtesy of the City University of New York

As sunlight travels farther through the atmosphere, it’s more thoroughly scattered. At sunset, when rays travel sideways through a thick slice of air instead of straight down, we see more of the spectrum spread out across the sky. The leftover light traveling directly to us is mostly red and orange, which explains the sun’s ruddy appearance as it sets.

Screen Shot 2016-05-27 at 10.00.14 AM

Sunset from AstroCamp

Written By: Caela Barry

DIY Science: Make an Egg Bounce

What do egg shells, coral reefs, and human bones have in common? They’re all made of calcium carbonate! This brittle mineral compound dissolves in acid. Try submerging an egg in white vinegar (a mild acid) for 24 hours, changing the vinegar, then continuing to soak the egg for about a week. What do you observe?

RubberEgg

The egg shell completely dissolves! This reaction between calcium carbonate and acid is a lot of fun in the lab, but it causes serious problems in the real world. Seashells, the homes of many aquatic creatures, are made of calcium carbonate, too. When excess carbon dioxide in the atmosphere diffuses into the sea, it reacts with water to form carbonic acid. Organisms made of calcium compounds slowly dissolve in its presence.

Acidification

Image courtesy of www.oceanacidification.org.uk

According to NOAA research, if acidification continues to occur as projected, coral will be dissolving faster than it can regrow by the end of the 21st century. Coral is a key component of many marine ecosystems; an estimated one million ocean species depend on it as part of their habitat.

Written By: Caela Barry

What’s So Special about the North Star?

The most famous star in the night sky is undoubtedly the North Star, also known as Polaris. It isn’t the brightest or most spectacular looking star, but it is nevertheless very important. Let’s take a look at why!

The image above shows the north star in the Idyllwild sky. As we know, the Earth is spinning. This is what causes the sun to rise and set and the stars to move across the sky. It is also tilted,  which gives us our seasons. If we were to draw a line through the axis that the Earth spins around, and then extend it over 300 light years past the North Pole, it would go right to the North Star!

Screen Shot 2016-06-06 at 8.56.38 AM

The motion of stars around Polaris from AstroCamp. Careful examination reveals that the North Star does move a tiny bit over the course of a night!

Because of this, it stays almost exactly in that spot in the sky all  night and all day, and thanks to its perch high above the North Pole, it always points the way North! This is really important for navigation, especially in the days before GPS devices, but it gets better!  If you were standing on the equator, Polaris would appear to be right at the horizon. From the North Pole, it would appear to be straight overhead. This means that using its height in the sky can do more than just point out the direction, it can also tell you where you are on the Earth!

north star

This shows how to find your location on the surface of the Earth using the position of Polaris. Image Credit: Fort Worth Astronomical Society

latitude

Interestingly enough, there isn’t a “South Star” because just by chance, there isn’t a bright enough star right above the South Pole! However, that won’t necessarily be like that forever! When a top spins on a tabletop, the end of it will move in a circle. This is known as precession. The Earth is basically a giant top in space, and it behaves the same way! This means that the North and South Poles won’t always point towards to the same spot in the sky! Over the course of 26,000 years, this will cause the North Star to change from Polaris to several other stars and back again.

 

Precession_animation_small_new

The Precession of Earth’s axis will cause the North Star to change from Polaris to other stars over the course of 26,000 years. Image credit: Wikipedia user Tfr000

Written By: Scott Alton

Survival Skills: Science Style

Light travels incredibly fast. In a vacuum, it speeds along at nearly six trillion miles per hour. Ever notice how your feet look distorted when you wade in the water, or how a straw seems to be cut in half where it enters a full glass? When light travels through a medium, it slows down. When a collection of light rays crosses from one material to another (from water into air, for instance), the change in speed warps the image.

StrawSmall

This warping effect can appear random, as in the case of rippling water, or it can be well-organized. We often take advantage of light’s transition between air and glass, for example, to bend images in a useful way. A magnifying glass works by taking a small image and spreading it out over a large area. What happens when you use it backwards– put a large cross-section of light in, then focus it down to a tiny point?

SunBurn

Try this with the sun as a light source on a warm day, and you’ll find that the visible light and heat at the focus point are intense enough to burn wood!

Written By: Caela Barry

WELCOME TO OUR ASTROCAMP BLOG

We would like to thank you for visiting our blog. AstroCamp is a hands-on physical science program with an emphasis on astronomy and space exploration. Our classes and activities are designed to inspire students toward future success in their academic and personal pursuits. This blog is intended to provide you with up-to-date news and information about our camp programs, as well as current science and astronomical happenings. This blog has been created by our staff who have at least a Bachelors Degree in Physics or Astronomy, however it is not uncommon for them to have a Masters Degree or PhD. We encourage you to also follow us on Facebook, Instagram, Google+, Twitter, and Vine to see even more of our interesting science, space and astronomy information. Feel free to leave comments, questions, or share our blog with others. Please visit www.astrocampschool.org for additional information. Happy Reading!

Categories

Archives

Tags