21 December 2007

Planetarium Software?

On the off chance that someone following this blog has an answer for this, I'm looking for planetarium software for an online class I am developing for Fall 2008.

Minimum Qualifications
  1. Cheap, or free with a good textbook

  2. Works on Windows XP and Mac OSX.4

  3. Ground can turn on and off

  4. RA/Dec coordinates

  5. Alt/Az coordinates

  6. Sun and all planets

  7. Messier objects

  8. Ecliptic line

  9. Effectively infinite time in the past and future

  10. Asterisms ("constellation" connect-the-dots drawings)

  11. Constellation borders (outlines)

  12. I can learn it with a user's manual and/or FAQs

  13. Students can learn simple tasks with hand-holding

Preferred Qualifications
  1. Free

  2. Works on Vista and all other platforms

  3. NGC and other deep-sky objects

  4. Images of objects

  5. Ability to move forward in 1-day increments without showing intervening time, so as to demonstrate
    1. the analemma,
    2. which constellation the Sun is in throughout the year,
    3. which constellations are visible at night throughout the year,
    4. the motion of the planets relative to the Sun, and
    5. the motion of planets relative to the sky.

  6. Ability to move forward in other time increments, such as a year

  7. Precession

  8. Ability to lock on an object (such as the Sun or Moon) while progressing time

  9. Easy to learn

FWIW, Google Sky fails Minimum #9, Starry Night Pro 3.1 passes Minimum #1b but fails Minimum #2 and may fail others since I can't run it to find out, Starry Night Pro 6.2 fails Minimum 1, I suspect The Sky 6 fails Minimum 1 but I haven't done enough research to be sure, and Stellarium appears to fail Preferred 6. Some combination of Stellarium and Google Sky appears to be what I'm going to have to deal with at this point.

X-posted a few places

Asteroid 2007 WD5

Among all the hype about how asteroid 2007 WD5 has a 1 in 75 chance of hitting Mars on January 30 everyone's missing what I think is the most exciting part. According to NASA/JPL simulations it passed closed enough to Earth in early-/mid-October that our planet's own gravity is probably what actually slung it into Mars's path.

You know what's even more exciting?

We didn't discover it until November.

Science Songs

I collect science songs so I can play them for my students - sure they're college age, but who doesn't appreciate a couple F-bombs about fractals?

For the younger crowd, here's some clean ones that teach you science in 5-minute chunks. Included among them is the original version of "Why Does the Sun Shine?" (popularized by They Might Be Giants).

19 December 2007

Chocolate, Caffeine, and Theobromine - Oh My!

Branching from a different discussion about migraines, dehydration, and caffeine, I wanted to look up whether caffeine was dehydrating - I knew it was a diuretic, but I wanted to know if it more directly dehydrated. And then I got sidetracked by an article about a parrot dieing from chocolate overdose. So rather than having any sort of coherent picture for you today, I present you with some snippits of facts about chocolate, caffeine, and theobromine.

  • "In healthy adults, caffeine's half-life is approximately 3–4 hours. In women taking oral contraceptives this is increased to 5–10 hours" [Wikipedia, original source] In other words, caffeine affects women on the Pill for twice as long as it does for most other adults, but it probably affects people not on the Pill more quickly and more strongly.

  • Caffeine on its own is a stimulant in the body. Caffeine metabolizes in the liver into three different other chemicals - most becomes paraxanthine (84%, takes fat out of storage and into the bloodstream, raising blood sugar levels, and sugar is a stimulant), theobromine (12%, diuretic and a stimulant, is present in chocolate and is why most people mistakenly think that chocolate has lots of caffeine), and theophylline (4%, a good asthma treatment, but in much higher concentrations than produced by caffeine metabolism, also raises blood pressure). Each of these by products appears to be created by removing a CH_3 from caffeine and replacing it with a Hydrogen, the only question is which one gets removed; each of them has further stimulant effects. [Wikipedia: Caffeine, Theobromine]

  • Chocolate contains both caffeine and theobromine, but significantly more theobromine, and only about as much caffeine as a cup of decaf coffee. Theobromine is often confused with caffeine however, and the media does not distinguish between the two, so the misconception that chocolate is a significant source of caffeine continues to perpetuate.

  • One of the ways caffeine works is that it "competes" with adenosine, so that it essentially stops adenosine from working. Adenosine is a depressant in the human nervous system, and its presence is related to the need for sleep; its lack means that dopamine instead begins to dominate - and dopamine is a stimulant, increasing heart rate and blood pressure.

  • In humans, theobromine has less of an effect on the nervous system than does caffeine, but has more of an effect on the heart. In addition, theobromine relaxes smooth muscles (ones that act involuntarily), such as dilating blood vessels (and thereby decreasing blood pressure) and bronchial tubes in the lungs (possibly explaining why I've always felt that caffeinated beverages help when I'm feeling allergic, as I also have allergy-triggered asthma).

  • For reasons unclear to me, most animals (including dogs, cats, and birds) process theobromine more slowly than humans, with the result that it affects them more strongly, leading to theobromine poisoning. Do NOT feed your pets any of your leftover holiday chocolates. It could be the last thing they eat.

Well, that's a bunch of disorganized facts for you. :-P I warn you of two things though, (1) "damnit Jim, I'm a doctor not an engineer!" I'm a astrophysicist, not a biologist, so it's possible I'm understanding some of this wrong; and (2) since I'm not on the clock, I used Wikipedia as my primary (nearly only) source rather than peer-reviewed journals, or even authoritative/reputable news sources, and as we all know, Wikipedia's biggest strength and weakness is that anyone can edit it. If you wish to contradict or clarify anything I mentioned here, I'd appreciate a concise quote from another source, as well as a link to it - I'm looking to learn! :)

ETA: Another link here to birds and theobromine.

15 December 2007

First steps of US on Global Warming

After a week of heated argument (and "boos") with other countries in Bali, US Under Secretary of State for Democracy and Global Affairs Paula Dobriansky finally agreed to an amended compromise statement. According to the NY Times,

The agreement notes the need for "urgency" in addressing climate change and recognizes that "deep cuts in global emissions will be required." Still, it does not bind the United States or any country to commitments on reducing greenhouse pollution.


The EU wanted an agreement to require developed countries to cut their emissions by 25 to 40 percent of 1990 levels by 2020. The United States opposes those targets, along with Japan and Canada. The latest draft of the agreement removes the specific figures and instead, in a footnote, references the scientific study that supports them.


The US and the EU earlier agreed that industrialised countries would not set firm emissions targets at this stage. The "Bali roadmap" initiates a two-year process of negotiations designed to agree a new set of emissions targets to replace those in the Kyoto Protocol.
The document coming out of the meeting, the "Bali roadmap", contains text on emissions cuts, the transfer of clean technology to developing countries, halting deforestation and helping poorer nations protect their economies and societies against impacts of climate change such as rising sea levels and falling crop yields. The roadmap sets the parameters and aims for a further set of negotiations to be finalised by the 2009 UN climate conference, to be held in Denmark.

So as far as I can tell, this is again an agreement with no teeth. The US has agreed to no tangible results whatsoever. It's progress in that we've agreed that Something Needs To Be Done and therefore are acknowledging that global warming is taking place, but all we've agreed to so far is to continue talking. Well, better that than nothing.

14 December 2007

Fluorescing cats

Everyone's been up in arms about these cloned "glowing" cats and how they're horribly eerie because they glow. Well, I have to tell you they're not eerie at all because they're not really glowing, they're fluorescing!

"Glowing" is when the object stores up light energy and releases it later in the dark. "Fluorescing" is when the object absorbs light of one form (usually UV) and immediately releases it in a different form (usually visible light). These cats would be no fun at all unless you have a UV light source. Most "blacklights" are both UV and some visible violet, but the professional ones used in that photo are only UV, and so that's why it looks like there's no light at all; if they turned off their UV light the cats would immediately go dark, just like normal cats. If you don't use a blacklight regularly, you wouldn't see anything weird about the cats at all.

There now, don't you feel better about dropping a fortune on one of these cats once they become commercially available?

ETA: Here's a video about them on CNN, that shows their faces fluorescing (it appears it's only the skin that does it, not the fur), and explains why it's medically usful.

09 December 2007

Asteroid Deflection

I find it intriguing that the best ways to deflect an asteroid from a collision with Earth always involve the Sun's light. NY Times reports on a new (to me) idea of sending a swarm of small spaceships with parabolic mirrors. These mirrors would focus sunlight on one spot on the surface of the asteroid - much like a child using a magnifying glass to focus sunlight on an ant. And just like the ant starts smoking, the spot on the asteroid would start vaporizing, and the gases coming off the asteroid would act as a rocket to push it away from its current trajectory. One benefit of this method that the Times points out is the only difference between a small and a large asteroid is how many mirror ships you send.

My favorite oddball technique is still painting half the asteroid reflective, and half absorptive - the dark side would absorb the momentum of photons from the Sun, while the light side would reflect them, and it would act like a single vane of a radiometer and the trajectory would be changed. The drawbacks to this method are that if the asteroid is spinning the trajectory change would be less, or erratic since the direction of thrust would be continually changing - and pretty much everything spins some. And painting it of course is a pain in the butt.

The mirror ships method has another advantage now that I've mentioned direction of thrust changing - the spot on the asteroid that they aim at can be changed. If the asteroid is spinning, the mirror ships can still always point at the side away from the Sun, for example. If you need to make adjustments to its trajectory, like it's moving a bit too fast, aim for the front side, and when it's going a bit to slow, aim for the back side.