Living in Minneapolis, I often ride my bike for exercise around the city lakes. The other day, while trying to get a ride in between rain showers, I was presented with a stunning rainbow. Actually, only a small portion of the arc was visible when I first saw it at Lake Harriet, but by the time I reached the west side of Lake Calhoun it had grown into a full blown double arced rainbow.
I stopped to admire it and regretted not having my camera with me because it was truly one of the best rainbows I had witnessed in a long time. A kid next to me, snapping a picture of it with his cell phone, wondered out loud, “How far away do you think that rainbow is?”
It was a good question and made me want to learn more about the atmospheric phenomenon.
Basically, rainbows are the result of sunlight being once reflected and twice refracted by raindrops. Certain conditions are required. First and foremost, the viewer needs to be located between the sun and rain clouds. A ray of sunlight enters an individual drop of water and is refracted (bent) as it enters, then reflected from the back of the drop, and refracted again as it exits the drop. The refractions cause the white sunlight to divide into separate colors. Each color refracts in slightly different amounts, red the least, and violet the most. A particular raindrop will reflect red light because it is positioned at just the right angle from your eye (42°). This is known as the “rainbow ray”. Another droplet located at a slightly different position will reflect blue light to your eye. Now multiply this by the innumerable suspended water droplets that make up a rain cloud, and you have a rainbow.
The main colors in a primary rainbow will have red at the top followed by orange, yellow, green, blue, indigo, and violet. An easy way to remember the order is to note that the first letter of each color spells out the name ROY G. BIV.
The rainbow I witnessed had a second, fainter rainbow just above the first. This is the result of some light being reflected twice, and at a higher angle. The colors in a secondary arc are reversed with red on the bottom and violet on top.
The inside of a rainbow is always brighter than the sky outside the arc. This is because other rays of light are reflected from individual raindrops at angles smaller than the rainbow ray. Since this scattered light is made up of all the other incidental colors the light inside the bow is white.
So, how far away is a rainbow? I’ll let you figure that out for yourselves. The answer may surprise you.
Tsunami warnings have been issued for Fiji and New Zealand after a earthquake of 7.8 magnitude shook the Pacific Ocean.
The quake's epicenter was about 153 miles off the coast of Tonga.
The Pacific Tsunami Warning Center issued the alert for Tonga, Niue, American Samoa, Samoa, Fiji, and Wallis-Futuna.
If a tsunami does occur, it could start to affect the islands by as early as 12:15pm (Minnesota time).
We'll post updates...
A comet is experiencing a spectacular break up as it swings around the sun. It will be at its closest on May 12th. Don't worry! It will be 30 times further away than the moon. Comets are mostly dirty ice. As the sun heats these slush balls they often break up. Even more spectacular is when an inner pocket of vapor bursts through the surface and acts like a rocket propelling that fragment in the opposite direction.
German astronomers Arnold Schwassmann and Arno Arthur Wachmann discovered this comet during a photographic search for asteroids in 1930, when the comet passed within 5.8 million miles of the Earth (only 24 times the Earth-Moon distance). The comet orbits the Sun every 5.4 years, but it was not seen again until 1979. Astronomers observed its initial breakup into four pieces that year. The comet was missed again in 1985 but has been observed every return since then.
NASA and the European Space agency have released new images from the Hubble Space Telescope showing the dramatic breakup of comet Schwassmann-Wachmann 3. The comet's nucleus has shattered into more than 33 pieces, and is likely to continue to disintegrate. They have even put several pictures together to create a movie of the breakup. Choose one from this page
A long time ago; far, far away, there might have been life on Mars.
Those are the conclusions researchers are coming to has they pull together data gathered from several space probes to the Red Planet over the past decade.
It all adds up to the possibility that Mars could have supported life during its first 1 billion years of existence. For the past 3.5 billion years, its conditions have been too harsh to sustain life as we know it. It became too cold and too dry for even the basic forms of live, microbes, to exist.
The findings of the research team were recently published in the journal Science. A team of international space experts has been studying the data gathered from various space missions.
In its first 600 million years, Mars likely had plenty of water, temperate weather and low acid levels. The research team has been able to figure that out by examining the oldest rocks they’ve found from the missions. Those rocks have been exposed on Mars’ surface due to erosion, cratering and large temblors.
Exactly were the water may have been on Mars is still up for debate. The research team keeps open the possibility that the planet’s surface never had large amounts of water covering it. Clay deposits, a key link to the presence of water on Mars, have been found beneath the planet’s surface. And the few exposed sections of clay may have been formed below the surface and later pushed up or exposed.
The tame first segment of the planet’s life was followed by 500 million years of great volcanic activity that filled the atmosphere with sulfur. Those particles fell back down in the form of sulfuric acid, while at the same time Mars began to lose its atmosphere. Then over the course of the next 300 million years, Mars got to its icy-cold, rusty-red look that it has still today.
All of this information is helping scientists plan where they want to send future Mars probes to get even more answers to these questions on Mars’ origins.
One of the random questions we often get at the Science Buzz is “why is the sky blue?”. A recent article published by the Columbia News Service addresses this question, along with nine others, in an article called How High is Your Science IQ? The article is a list of ten science facts every high school graduate should know. To get to the 10 facts the Columbia News Service asked Nobel Prize winners, institute heads, and teachers, “What is one science question every high school graduate should be able to answer?” The questions are good ones – how many can you get right? Check out the article and test yourself!
Oh, and if you want even more information on why the sky is blue, here is a good Wikipedia article on the subject.
Another planetary probe has achieved orbit around a planet in our solar system. Much like NASA’s Mars Reconnaissance Orbiter, the European Space Agency’s (ESA) Venus Express entered an elongated orbit of Venus yesterday. The probe will spend the next four weeks to refine its orbit from its current 9 day to a 24 hour polar orbit.
The Venus Express was launched on November 9, 2005 and once it has reached its goal orbit will begin exploring the Venusian atmosphere. The probe will study the atmosphere’s complex dynamics and chemistry, as well as the relationship between the atmosphere and the planet’s surface, which will provide clues about surface characteristics.
One aspect of the Venusian atmosphere that Venus Express will investigate is the incredible atmospheric vortices that rotate over Venus’ poles. The vortex over the North Pole, has an unusual “double eye” configuration and its origin and impact on the planet continue to be a mystery.
This will be the fourth ESA probe to achieve orbit around another celestial body. The ESA also operates the Mars Express (Mars), SMART-1 (the Moon), and is NASA’s partner on the Cassini-Huygens orbiter (Saturn). The ESA is also operating the Rosetta probe which is on its way to the comet 67P/Churyumov-Gerasimenko, which it will begin orbiting in 2014.
The stratovolcano Augustine is located in south central coastal Alaska, forming a circular island about 1,260 meters in height. Augustine has been erupting since January 2006, and is now color-coded “orange,” meaning further eruptions can occur at any time. Lava flow and rock falls are likely to continue for several weeks or months. The geologic record at Augustine indicates the volcano has been active for about 40,000 years. It experienced a very large eruption in 1883 that blew most of the volcano away, and has been rebuilding itself ever since. In 1986, it erupted and created an ash cloud over Anchorage, some 290 km away. Satellites actively monitor Augustine for changes in temperature and ash plumes. Check out this live web cam of the volcano.
In addition to volcanoes on the west coast of the continental U.S., there are over forty-one historically active volcanoes in Alaska, including thirty that are monitored in real time. Most of Alaska’s volcanic features fall along the Aleutian arc. These volcanoes form a neat line between Alaska and Russia because they fall along a plate boundary. The subduction of the Pacific Plate beneath the overlying North American plate is what creates these volcanoes—and multiple earthquakes as well!
No humans live close enough to Augustine to be threatened by eruptions. Ash clouds from the volcano, however, do pose a threat to air travel in the region. Volcanic ash not only makes it difficult to navigate; it can also damage moving parts of jet planes, cause clogs, and even trigger engine failure. Although no human life has been lost, many planes in the last two decades have suffered damage from volcanic ash while flying through the region.
The Mars Reconnaissance Orbiter (MRO) is scheduled to begin orbiting Mars on March 10th, seven months after leaving Earth on August 12, 2005.
Designed to study Mars in a low orbit, the MRO will have to make a tricky maneuver before the orbit is achieved. As the MRO approaches Mars, NASA expects to receive a signal around 3:24 Central time from the MRO indicating that it has turned its main thrusters forward and begun a 27-minute engine burn meant to slow the spacecraft down enough to allow Mars' gravity to capture it. The engine burn will end during a 30 minute window when the MRO is behind Mars and out of radio contact, so controllers will have some time to sit and worry. And there is good reason to worry. Past NASA missions sent to orbit Mars have had only a 65% success rate. If the engine burn is successful the MRO will be in a very elliptical 35-hour orbit. In order to get the MRO into the desired circular 2-hour low orbit it will continue to use Mars' atmosphere to slow it down. This process, called aerobraking, is also very tricky as Mars' atmosphere is unstable and can swell unpredictably. Current Mars orbiters in higher orbits will monitor the atmosphere to help keep the MRO at a safe and effective orbit.
Once the desired orbit is achieved, scientific operations can begin. The MRO carries six scientific instruments on board that are designed to collect more data than all of the previous Mars orbiters combined. Information on the weather, radar images of the surface and sub-surface, water sensors, and color images of the surface will be gathered to increase our overall understanding of Mars, as well as to help NASA select future landing sites for unmanned, and possibly manned, missions to the surface. The MRO is also designed to relay information from planned missions to the surface of the planet as well, including the Phoenix Mars Scout (set to land near the polar ice cap in 2008) and the Mars Science Laboratory (scheduled for launch in 2009).
A podcast about the mission is available from NASA. You can also check out where the MRO is now, check out a Quicktime movie about the process of just getting the MRO to this point, and more at the MRO page.
Personally, I think the Hubble Space Telescope is incredible — the images it captures fascinate me. These images of the Orion Nebula were just recently released, and if you're into images from space, or just think these are cool, visit the media site and look at the larger resolution and magnified images they have available there, as well as the detail images with description. The level of detail is amazing. Totally gets my imagination going. Here is the press release on the image as well.
Scientists at Rutgers University in New Jersey have discovered that the amount of oxygen in the Earth's atmosphere has more than doubled over the last 205 million years.
By studying samples of seafloor material going back millions of years, they determined that the atmosphere was only 10% oxygen during the time of the dinosaurs. It rose as high as 23% by 40 million years ago. (The air is 21% oxygen today.) That's about the time that really large mammals, like elephants and rhinos, started to emerge.
Oxygen levels may have affected the evolution of mammals. These warm-blooded creatures need three to six times as much oxygen as a reptile of the same size. The lack of oxygen may have prevented them from growing very large. But as oxygen levels increased, mammals could start getting bigger.