I'm sorry to have to give you this post instead of any of the science posts I promised about two months ago. Life got busy and hasn't slowed down one bit.
Around Thanksgiving, I realized that the work I had to do for classes was getting a lot more demanding than it had been for the rest of the semester. I had finals coming up. I had a homework assignment to grade two days before my first exam. I was supposed to have four exams (one for each class) in that week, but decent portion of the mid-Atlantic coast got hit by a blizzard that Friday. Two of my finals were snowed out. I took one as a take-home the day after it was supposed to be administered, but I'm taking the other on the university's official make-up date: tomorrow.
In the time between then, I took a class during my three weeks of winter break to fulfill a general requirement, but the most time consuming thing was starting up a research project. Don't get me wrong, it was time consuming because I loved it (and still do--I plan to work on it until I graduate).
The final for my winter course was a week ago, and then I started spring term this Monday. I got to listen to my friends, who had returned to campus only a day or so before, complaining about how their winter break felt so short, when I had basically been working straight through since the start of fall.
I'm taking six classes this term for a total of 16 credits. Four are astronomy, two are physics. I'm still grading for the non-majors astronomy class. I'm applying for summer research at observatories and universities across the US, and all the applications are due within the next two weeks.
I'd say that life has gotten in the way of writing, but it hasn't. Life has gotten in the way of research.
I've greatly enjoyed Xanga, and while I'm not shutting down my site (that would be silly--it costs me nothing to leave it sit here indefinitely), I can't say when will be the next time I'll really be around. I apologize to everyone for starting the scientific misconceptions series and not finishing it, and especially to the people who added me as a friend back in November/December when I was still promising posts. I'd like to continue writing, but I don't see myself having the time for it.
Looks like it's time for another short break. I haven't posted in nearly a week and don't anticipate being able to post much over the next three, which are the last two weeks of classes and one of finals. I had intended on writing something over Thanksgiving, but was pretty backlogged with work (two homework assignments and one test to grade) so I didn't even get a chance to finish my own homework.
I may get a chance to post a few times in the next three weeks, but I doubt I'll be able to add anything to my Scientific Misconceptions series. On that topic, the next post will be entitled "It's only a theory!" and will basically address the scientific process and clarify the terms we use (such as the difference between a theory and a hypothesis).
If you'd like to see anything specifically addressed, leave a comment or send a message.
There is a new Symphony of Science video online! This one features Carl Sagan, Richard Dawkins, Michio Kaku, and Robert Jastrow, and is just as fantastic as the first two. MP3 downloads are available at the Symphony of Science website.
We must ask ourselves We who are so proud of our accomplishments What is our place in the cosmic perspective of life?
The Leonid meteor shower will reach its peak tonight at 5 pm EDT when Earth passes through the densest part of the debris stream left by Comet Tempel-Tuttle.
Comet Tempel-Tuttle passes close to the Sun every 33 years, leaving a trail of meteoroids (objects 10-6 to 10 m across), which Earth encounters every November. It has been 11 years since Tempel-Tuttle last made its appearance in the inner Solar System.
A meteor is a meteoroid that has entered Earth's atmosphere (it gets called a meteorite if is survives its trip all the way to the ground). This meteor shower gets its name from the constellation Leo, which is in the portion of the sky where the meteors appear to originate. Predictions for this year's even vary considerably, from NASA's 20-30 per hour in the US and 200-300 per hour in Asia to estimates of 500 per hour at its maximum.
To see this meteor shower, simply look up for a few minutes! If possible, get to a sparsely populated area--light pollution can be a great annoyance for observing. Luckily, we will have a new Moon, so its reflected light won't interfere at all. Though the map below may look like bad news for those of us on the East Coast, there are still dark skies to be found. Just download one of the high-resolution maps linked at the bottom of the page and find a dark location near you.
When polled, "What causes Earth's seasons?", a large percentage of the people asked would respond that it is our varying distance from the Sun. While Earth does go between 147 million kilometers away at its closest point and 152 million kilometers away at its farthest point, this is not a significant variation. In fact, the northern hemisphere is experiencing summer when the Earth is at its farthest point from the Sun.
This misconception often comes from over-exaggerated diagrams of Earth's orbit, showing it as an elongated ellipse:
Earth's orbit, if viewed from above, would appear circular. The amount that Earth's orbit deviates from circular, called eccentricity, is very small--so small that we can't perceive the difference.
But what does cause the seasons?
The seasons are due to the fact that Earth's spin axis (also called the axis of rotation) is tilted 23.5 degrees to the ecliptic. The Earth orbits the Sun in a plane--think of a flat sheet of paper with Earth's orbit traced out on it, and the Sun drawn in very near the center of the orbit. This plane is called the ecliptic. If the Earth were to have no tilt at all, its spin axis would point straight up out of our plane, perpendicular to the ecliptic. Our tilt is measured in relation to this perpendicular.
Our planet's tilt affects how much sunlight different portions of the globe get at different times of the year. The first day of spring and fall is referred to as an equinox (from Latin, equal + night) because the day and night both have the exact same length at all points on the globe. The Sun's rays are hitting the equator from directly overheard.
The first day of summer and winter is referred to as a solstice and is respectively the longest and the shortest day of the year.
So why should this cause a difference in temperature? The answer involves simple geometry. Sunlight coming from directly overhead has to heat a smaller area than the same amount of sunlight hitting the surface of the Earth indirectly (at an angle). The surface receiving direct sunlight heats up more than the surface receiving indirect sunlight, making it warmer. The surface receiving indirect sunlight is relatively cooler.
direct sunlight (left) compared to indirect sunlight (right)
The idea of seasons caused by varying distance is in no way far-fetched, though. Mars, which has some Earth-like characteristics, with a 24.6 hour day and a 25.2 degree tilt, also has a far more eccentric orbit--about 8 times as eccentric as Earth's orbit! Instead of our small variation of 5 million km between closest and farthest point, Mars has a variation of almost 60 million km. This large difference is far more important to Mars' season than its tilt.
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