Unique VisitorsIn preparation for an Ancient Astronomy course I'll be teaching in the fall, I thought I'd put together a series of posts on the movements of the Moon. The first one will appear tomorrow.
Wednesday, July 13, 2011
Haven't posted for a while...
I haven't posted for the past week since I've been busy with two online courses which just started (in addition to working around the house, a little hiking, etc.).
In preparation for an Ancient Astronomy course I'll be teaching in the fall, I thought I'd put together a series of posts on the movements of the Moon. The first one will appear tomorrow.
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In preparation for an Ancient Astronomy course I'll be teaching in the fall, I thought I'd put together a series of posts on the movements of the Moon. The first one will appear tomorrow.
Tuesday, July 5, 2011
Geocentrism refuses to die for some religious loons
The Chicago Tribune had a story yesterday about a group of religious loons (Catholic, this time) who just can't come to grips with reality (Some Catholics seek to counter Galileo).
You know what? They're correct. Hell, they don't even go far enough! There are many Biblical verses that clearly support a flat, geocentric Earth supported on pillars - here's a list. This is the real Biblical cosmology that should be supported by all Bible-believing Christians:
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If you don't believe this, you're just a heathen in the fast-lane straight to Hell.
You know what? They're correct. Hell, they don't even go far enough! There are many Biblical verses that clearly support a flat, geocentric Earth supported on pillars - here's a list. This is the real Biblical cosmology that should be supported by all Bible-believing Christians:
If you don't believe this, you're just a heathen in the fast-lane straight to Hell.
Monday, July 4, 2011
Happy Aphelion
Yes, I know, everyone else celebrates the 4th of July. Don't get me wrong, I'm a huge fan of the freedoms our Constitution and independence gave us, but there's something else that's notable today.
So, why is it so much hotter today than it will be in early January? Because the difference in the Earth's position from the Sun between aphelion and perihelion is only about 3% and not really enough to have much of an effect on the amount of insolation (incoming solar radiation) reaching the Earth. If it were the reason for the seasons, the Northern and Southern Hemispheres would both have summer in January and winter in July.
The real reason for the seasons is the 23.5° tilt of the Earth's axis. The Northern Hemisphere is tilted toward the Sun on the June solstice giving us more direct sunlight and more hours of sunlight. In the Southern Hemisphere, they're tilted away from the Sun so it's their winter On the December solstice, we're tilted away from the Sun so we have less direct sunlight (it comes in at a lower angle) and less hours of sunlight. The equinoxes, of course, are the half-way points between the solstices.
As we start to move closer and closer to the Sun over the next six months, the Earth will also begin to speed up in its orbital path - all part of Johannes Kepler's Three Laws of Planetary Motion - the subject of another post!
Today, July 4, at 1500 UTC (11:00 am EDT), the Earth will be at aphelion in its elliptical orbit around the Sun. We're 152,097,700 km (94,509,130 miles) from the Sun today. Perihelion, when the Earth is closest to the Sun (peri is Greek for "next to" and helios is the Greek word for the Sun), will occur on January 5, 2012 at 0100 UTC. At that time, we'll be only 147,098,070 km (91,402,500 miles) from the Sun. This is a difference of about 5 million km (3 million miles).
Image from Starts With a Bang
So, why is it so much hotter today than it will be in early January? Because the difference in the Earth's position from the Sun between aphelion and perihelion is only about 3% and not really enough to have much of an effect on the amount of insolation (incoming solar radiation) reaching the Earth. If it were the reason for the seasons, the Northern and Southern Hemispheres would both have summer in January and winter in July.
The real reason for the seasons is the 23.5° tilt of the Earth's axis. The Northern Hemisphere is tilted toward the Sun on the June solstice giving us more direct sunlight and more hours of sunlight. In the Southern Hemisphere, they're tilted away from the Sun so it's their winter On the December solstice, we're tilted away from the Sun so we have less direct sunlight (it comes in at a lower angle) and less hours of sunlight. The equinoxes, of course, are the half-way points between the solstices.
As we start to move closer and closer to the Sun over the next six months, the Earth will also begin to speed up in its orbital path - all part of Johannes Kepler's Three Laws of Planetary Motion - the subject of another post!
Friday, July 1, 2011
New Nabro Images
New images of Nabro volcano in Eritrea (see my previous post) from the Advanced Land Imager (ALI) on the Earth Observing-1 (EO-1) satellite. The gas and ash cloud has died down a bit allowing a much better view of the volcano and resultant lava flow.
The top image shows the area in visible and infrared light. The IR indicates heat energy so the vent and hot lava shows up especially well. Contrast this with the bottom image in natural light in which it's more difficult to see where the hottest material is still flowing.
Since there are no geologists on the ground here (at least that we know of), there is some interest as to the magma composition. Volcanologist Erik Klemetti has tried to use these satellite images to work this out given how far the magma moved over several days and calculating its viscosity (different magma compositions have different viscosities).
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