When reports about a meteor make headline news in Los Angeles, it’s time to pay attention. In fact, anything that isn’t associated with a high-speed car chase or the latest celebrity DUI is usually worth paying attention to (take it from me, it doesn’t happen very often). But tonight, local news stations are reporting excited eyewitness accounts of a daytime meteor that ripped through the skies above Nevada and California on Sunday morning.
According to NBC News 4, the daylight meteor was spotted after 8 a.m. PST as it traveled from northern Nevada to California. Eyewitness accounts of the streaking light accompanied by a sonic boom flooded in from Lake Tahoe, El Dorado County, Placer County, Tuolumne County, Amador County and Nevada County.
Equinox means “equal night” in Latin, capturing the idea that daytime and nighttime are equal lengths everywhere on the planet. That is true of the Sun’s presence above the horizon, though it does not account for twilight, when the Sun’s rays extend from beyond the horizon to illuminate our gas-filled atmosphere.
Credit: NASA EUMETSAT; image from March 20, 2011
Saturday’s Lunar Eclipse Will Include ‘Impossible’ Sight
This year’s second total lunar eclipse on Saturday (Dec. 10) will offer a rare chance to see a strange celestial sight traditionally thought impossible.
The moon passes through the southern part of the Earth’s shadow, with totality beginning at 6:06 a.m. PST and lasting 51 minutes. [Total Eclipse of the Moon (Infographic)]
For most places in the United States and Canada, there will be a chance to observe an unusual effect, one that celestial geometry seems to dictate can’t happen. The little-used name for this effect is a “selenelion” (or “selenehelion”) and occurs when both the sun and the eclipsed moon can be seen at the same time.
But wait! How is this possible? When we have a lunar eclipse, the sun, Earth and moon are in a geometrically straight line in space, with the Earth in the middle. So if the sun is above the horizon, the moon must be below the horizon and completely out of sight (or vice versa).
And indeed, during a lunar eclipse, the sun and moon are exactly 180 degrees apart in the sky; so in a perfect alignment like this (a “syzygy”) such an observation would seem impossible.
But it is atmospheric refraction that makes a selenelion possible.
Atmospheric refraction causes astronomical objects to appear higher in the sky than they are in reality.
For example: when you see the sun sitting on the horizon, it is not there really. It’s actually below the edge of the horizon, but our atmosphere acts like a lens and bends the sun’s image just above the horizon, allowing us to see it.
This effect actually lengthens the amount of daylight for several minutes or more each day; we end up seeing the sun for a few minutes in the morning before it has actually risen and for a few extra minutes in the evening after it actually already has set.
The same holds true with the moon, as well.
As a consequence of this atmospheric trick, for many localities there will be an unusual chance to observe a senelion firsthand with Saturday morning’s shadowy event. There will be a short window of roughly 1-to-6 minutes (depending on your location) when you may be able to simultaneously spot the sun rising in the east-southeast and the eclipsed full moon setting in the west-northwest.
We have walked on the moon, sent rovers to Mars, and discovered planets light-years away. But the farthest we have ventured inside our own planet—the 7.6-mile-deep Kola Superdeep Borehole in the Russian Arctic—got us only 0.4 percent of the way to the core. The inner earth has been terra incognita, until now.
Using technologies analogous to medical CAT scans, geologists are virtually peeling back our planet’s outer layers and exposing its internal life in exquisite, three-dimensional detail. To create this big-picture view, University of Southern California geophysicist Thorsten Becker used seismic tomography, which tracks waves produced by earthquakes as they travel around and through the earth. The model reveals the structure of the mantle—the thick shell of hot, compressed rock that lies between the crust and the core. The mantle, which makes up more than four-fifths of the earth’s volume, is energized by radioactive heating within it and by the molten iron outer core below it. “As the core gives off heat,” Becker says, “the mantle convects, moving sluggishly, like a pot of boiling honey.” That slow churning, in turn, drags the crust with it.
Seismic waves move through relatively hot regions (red) more slowly and cold regions (blue) more quickly than through the rest of the mantle. By measuring the motions of those waves, Becker was able to create this thermal map, with the sphere in the middle showing the temperature at the deepest point of the mantle. (Lumps delineate the temperature anomalies; gold arrows denote how quickly different regions of the mantle and crust are moving, with the longest indicating four inches a year.) “Mantle convections drive plate tectonics,” Becker says. “So if we want to understand anything that happens on the surface geologically, from mountain-building to earthquakes, we need to understand the deep movements of the mantle.”
Morning Sun on the Gulf of Mexico
In this photo taken from the Apollo 7 spacecraft, the morning sun glimmers on the Gulf of Mexico and the Atlantic Ocean.
This is a real image taken by the robotic spacecraft Cassini of Saturn eclipsing the sun (via).
Amazing. There is a little blue dot on the left side of the image just above the bright main rings. That is Earth, approximately a billion miles away.
Not psychology related, just an incredible image. Click for high resolution to see Earth.
Incredibly Colourful Magnified Grains of Sand
Viewed at an astounding magnification of over 250 times, tiny grains of sand are surprisingly colorful and extremely unique. Each piece is either a fragment of crystals, spiral fragments of shells or crumbs of volcanic rock.
To see these incredible images, Dr. Gary Greenberg goes through a painstakingly lengthy process. First he takes many photos from different points of focus. Then, he combines them using software to produce one spectacular image.
“It is incredible to think when you are walking on the beach you are standing on these tiny treasures,” says Greenberg.”