jump to navigation

Telling Time by the Stars October 31, 2006

Posted by ionicflux in Portals.
add a comment

star.pngHowever, learning how to do it is educational. It teaches you a few things about the constellations, and a few things about spherical geometry.

The task requires more skill than you might think. I just checked with google and found a googol of sites that describe what I call the “standard hokey” technique — namely the one that depends 100% on the “pointer” stars: Alpha and Beta Ursae Majoris (Dubhe and Merak). This has the slight problem that it doesn’t work. It has apparently been devised by people who spend too much time looking at star-charts and not enough time looking at the real sky. It works OK at, say, 10PM in late April, when the pointers are high overhead, but it gives the wrong answer 3 months later and/or 6 hours later (because of spherical geometry) and it gives no answer at all 6 months and/or 12 hours later (because you’ll have trouble seeing the pointers).

Typical charts of the circumpolar stars use a polar projection, which doesn’t accurately portray how things actually look. Suppose you are standing at latitude 40 degrees North, and the 0-hour circle (marked by e.g. Beta Cassiopeiae) is overhead. That does not mean that the 18-hour circle (marked by e.g. Gamma Draconis) is a horizontal line 40 degrees above the horizon. It is locally horizontal near the pole, but then it dips quite markedly. If you extend it far enough it dives through the western horizon. Gamma Draconis is halfway along the great-circle route from the pole to the horizon, so its elevation above the northwestern horizon is less than 3/4ths of the elevation of the (since the sine of 45 degrees is 0.7).

I’ve found several on-line star-chart generation sites that get this wrong, but I’ve been unable to find one that gets it right. Can anybody recommend something that works?

Anyway, here is how I do it. This is just a quick overview; you will have to fill in many details on your own. This only deals with the northern temperate latitudes. Also note that tradeoffs have been made between convenience and accuracy: there are simpler methods that are grossly inaccurate, and more-accurate methods that are more complex (using equatorial rather than circumpolar stars).

  1. Memorize four landmarks (skymarks?)
    • The 0-hour circle. This is marked by Beta Cassiopeiae (Caph) which is the star at the bright end of the W, the end with the acute angle. Continuing along, we also have Alpha Andromedae (Alpheratz) and Gamma Pegasi (Algenib) which together constitute the trailing (eastern) edge of the Great Square — hard to miss.
    • The 6-hour circle. This is marked by Delta Aurigae, Beta Aurigae (Menkalinan), and Theta Aurigae.
    • The 12-hour circle. This is marked by point halfway between Delta and Gamma Ursae Majoris, the two non-pointer stars in the bowl of the Big Dipper. (The pointer stars are excellent markers for the 11-hour circle.)
    • The 18-hour circle. This is marked by Chi, Phi, Xi, and Gamma Draconis, the hind feet, chin, and nose (Eltanin) of the Dragon.

    Also remember that the 12-hour circle is the continuation of the 0-hour circle, and that the 18-hour circle is the continuation of the 6-hour circle.

  2. The 12-hour circle is overhead at midnight at the spring equinox. The 18-hour circle is overhead 6 hours later, and/or 3 months later in the year. And so forth. This gives you four “primary” reference pictures, where one of these four circles is overhead.
  3. You can then construct four “secondary” reference pictures, halfway between the primaries. These correspond to the situation where the primary circles form a giant V shape that is symmetrical with respect to the vertical. Do not try to judge the angle that the circles form relative to horizontal, because the perception of horizontal is distorted by the spherical geometry. The perception of vertical is OK, and the perception of symmetry is OK. Anything else you need can be judged by interpolation between the symmetrical picture and the vertical picture.
  4. As you face north, the great clock in the sky rotates counterclockwise1. It moves counterclockwise as you get later in the night or later in the year. The time-of-year contribution is 2 hours per month, or a half hour per week.
  5. Therefore: Suppose it is March 22nd. If you see the 12-hour circle is past vertical, 1/3rd of the way to the symmetrical V position, it must be 1:00 AM. If it is two weeks later in the year, the same picture is only 12:00 midnight (standard time); the advancement is explained by being later in the year, not later at night.
  6. Correct for daylight savings time. If DST is in effect, humans say it is one hour later than the stars say it is.
  7. Correct for longitude. This could be a half hour either way if you are near the edge of your timezone. The correction is zero if you are in the middle of your timezone.
Advertisements

A Thousand Days on Mars October 30, 2006

Posted by ionicflux in Gadgets, Science.
add a comment

spirit_rover_impression.jpg

From the start — from the day the first of the two Mars rovers safely landed there in 2004 — Steve Squyres has been warning that their time was limited.

At some point a computer would crash, or a circuit would give out, and one rover or the other would die.

It hasn’t happened. The two robotic rovers were supposed to last for 90 “sols,” or Martian days. As of today, Spirit, the first rover, has survived 1,000 sols.

“It’s pretty amazing, actually,” said Justin Maki, the lead imaging scientist for the rover project. “The rover’s basically in good health, especially considering its age.”

Big Bang theory saved October 29, 2006

Posted by ionicflux in Discovery, Science.
add a comment

An apparent discrepancy in the Big Bang theory of the universe’s evolution has been reconciled by astrophysicists examining the movement of gases in stars.

bigbang.jpg

Professor John Lattanzio from Monash’s School of Mathematical Sciences and Director of the Centre for Stellar and Planetary Astrophysics said the confusion surrounding the Big Bang revolved around the amount of the gas Helium 3 in the universe.

“The Big Bang theory predicts a certain amount of Helium 3 in the universe,” Professor Lattanzio said. “The trouble is, low mass stars (about one to two times the size of our sun) also make Helium 3 as a side product of burning the hydrogen in their cores.

“It’s been thought that when the star becomes a giant it mixes the helium 3 to its surface and, near the end of its life, spews the helium 3 into space just before it becomes a planetary nebula.

“But there are inconsistencies with the amount of Helium 3 predicted to be in the universe and the amount that’s actually there; there’s much less than expected.”

Some scientists have theorised that the rapid rotation of low mass stars destroys the helium 3 they produce. But computer models that have included this rotation, while showing some destruction of helium 3, have not been able to reconcile the Big Bang theory.

Professor Lattanzio, in collaboration with Dr Peter Eggleton and Dr David Dearborn from the Lawrence Livermore National Laboratories in the US, ran 3D computer models of a red giant’s life on some of the world’s fastest computers to investigate whether there was some sort of gaseous mixing occurring in stars that destroyed Helium 3.

Their findings have been published in today’s issue of the international journal Science.

Near the end of a star’s life there is a ‘core flash’ and it was at around this time that the computer models revealed a small instability in the movement of the gases in the star. “When we looked at this in 3D we found this hydrodynamic instability caused mixing and destroyed the helium 3 so that none was released into space,” Professor Lattanzio said.

“This apparent problem with the Big Bang has been solved – the helium 3 in the universe comes from the Big Bang and low mass stars, although they produce helium 3, do not release any into the universe because they destroy it.”

The missing secrets of Nikola Tesla October 28, 2006

Posted by ionicflux in People, Science.
add a comment

Bio-Shirt Monitors Athletes October 27, 2006

Posted by ionicflux in Gadgets, Sports.
add a comment

bioshirt.jpgBio-Shirts, developed by Korea’s state-backed Electronics and Telecommunications Research Institute, were introduced last week at the National Sports Festival. The shirts are designed to monitor various physiological parameters so elite athletes don’t push themselves too hard. Several sprinters tried out the Bio-Shirts.

The Bio-Shirt has two parts; a specially designed lightweight shirt and a monitoring system that weighs just 20 grams including the battery. The battery life will be prolonged to cover the average running time of amateur marathon runners—about five hours.

“Next year, people wearing Bio-Shirt will be able to know their temperatures, heart rates and speeds while running on a real-time basis using a wristwatch-type miniature computer enabled by Bluetooth,” said development team leader Kim Seung-hwan. “When any of the three data types hits a ceiling configured in advance, a warning sign will let marathoners know it is time to stop running and take a rest,” Kim said.

The shirt can also be used as a non-invasive ambulatory monitoring system for medical patients.

The Bio-Shirt is in part the realization of the heartshirt, one of science fiction writer Rudy Rucker’s ideas from his 1988 novel “Wetware”:

Della’s first present was an imipolex sweatshirt called a heartshirt?The heartshirt was an even dark blue, except for a few staticky red spots drifting about. “It can feel your heartbeat … look.” Sure enough there was a big red spot on the plastic shirt just over her heart, a spot that spread out into an expanding ring that moved on over her shoulders and down to her sleeves.

Curry may keep elderly minds sharp October 26, 2006

Posted by ionicflux in People.
add a comment

curry.jpg

A diet containing curry may help protect the aging brain, according a study of elderly Asians in which increased curry consumption was associated with better cognitive performance on standard tests.

Curcumin, found in the curry spice turmeric, possesses potent antioxidant and anti-inflammatory properties.

It’s known that long-term users of anti-inflammatory drugs have a reduced risk of developing Alzheimer’s disease, although these agents can have harmful effects in the stomach, liver and kidney, limiting their use in the elderly.

Antioxidants, such as vitamin E, have been shown to protect neurons in lab experiments but have had limited success in alleviating cognitive decline in patients with mild-to-moderate dementia.

In their study, Dr. Tze-Pin Ng from National University of Singapore and colleagues compared scores on the Mini-Mental State Exam (MMSE) for three categories of regular curry consumption in 1,010 nondemented Asians who were between 60 and 93 years old in 2003.

Most of the study subjects consumed curry at least occasionally (once every 6 months), 43 percent ate curry at least often or very often (between monthly and daily) while 16 percent said they never or rarely ate curry.

Reuters

Einstein’s Twin Paradox October 25, 2006

Posted by ionicflux in Science.
add a comment

einstein_big.jpg

March 22, 2006: Consider a pair of brothers, identical twins. One gets a job as an astronaut and rockets into deep space. The other stays on Earth. When the traveling twin returns home, he discovers he’s younger than his brother.

This is Einstein’s Twin Paradox, and although it sounds strange, it is absolutely true. The theory of relativity tells us that the faster you travel through space, the slower you travel through time. Rocketing to Alpha Centauri—warp 9, please—is a good way to stay young.

Or is it?

Some researchers are beginning to believe that space travel could have the opposite effect. It could make you prematurely old.

Two plus two make five October 24, 2006

Posted by ionicflux in People.
add a comment

business_math.jpgThe phrase “two plus two make five” (or “2 + 2 = 5”) is sometimes used as a succinct and vivid representation of an illogical statement, especially one made and maintained to suit an ideological agenda.

Its common use originates from its inclusion in George Orwell’s Nineteen Eighty-Four (Part Three, Chapter Two), where it is contrasted with the true, mathematical phrase “two plus two make four.” Orwell’s protagonist, Winston Smith, uses the phrase to wonder if the State might declare “two plus two makes five” as a fact; he ponders that, if everybody believes in it, does that make it true? Smith writes, “Freedom is the freedom to say that two plus two make four. If that is granted, all else follows.” Later in the novel, Smith attempts to use doublethink to teach himself that the statement “2 + 2 = 5” is true, or at least as true as any other answer one could come up with.

Tallest Men In The World October 23, 2006

Posted by ionicflux in People.
add a comment

Two tallest men in the world. One lives in Mongolia and his height is 236.1 cm and he is the tallest man in the world according to the Guinness Book of World Records. The other one is a Ukrainian and he height is 253 cm but not yet registered by Guinness books.

 

tall01.jpg

 

 

tall02.jpg

tall04.jpg

The Whereabouts of Dr. Einstein’s Brain October 22, 2006

Posted by ionicflux in People.
add a comment

brain.jpgDr. Albert Einstein died on April 18, 1955 at Princeton Hospital in Trenton, New Jersey. In accordance with his wishes, he was cremated without ceremony on the same day, and his ashes scattered at an undisclosed location. But the body that arrived at the cremation oven was not quite complete… it was lacking its brain.That’s because Einstein’s brain was sitting in a jar of formaldehyde in Dr. Thomas Harvey’s office. Dr. Harvey was the pathologist who performed Einstein’s autopsy, and while doing so, he removed and kept the brain for his own study. Some say that Einstein volunteered his brain for research, but the executor of his estate denies this, saying that it was Einstein’s son Hans who made the decision to have it preserved. But the press soon learned that Einstein’s brain had been set aside for study, and antagonized Einstein’s family with unwanted attention.