Breaking the Sound Barrier, With Your Head

Felix Baumgartner is making his final preparations for a record-breaking, supersonic skydive from a little less than 23 miles above New Mexico’s desert surface.  The jump is currently scheduled for Tuesday, October 9th.

Reports are that he will be going directly to Disneyworld after landing.

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Shine On Harvest Moon

Folks of a certain age (which includes yours truly) grew up singing “Shine On Harvest Moon” along with Mitch Miller and his bouncing ball.  On You Tube, a wonderful and humorous version of this song is sung by none other than Oliver Hardy, with Stan Laurel soft shoeing in accompaniment.

More to the science of it, the Harvest Moon is defined as the moon closest to the autumnal equinox.  This moon just occurred the night of September 30th, and was captured, by a Chicago Tribune photographer, framing the statue on the top of the old Montgomery Ward’s administration building.  As a child, my dad comically deceived us into thinking the statue was that of a monkey, hence “Monkey Wards”.

My understanding of the Harvest Moon is that it was used by farmers to extend their harvest past sundown.  In any event, the moon lies low to the horizon, and so looks large, because of the moon illusion.  Further, the moon looks yellowish and gauzy, because it shines more directly through the atmosphere of the eastern horizon.

Why is the Harvest Moon so low in the sky when it rises?  The answer is that the Moon and the Sun both track the ecliptic, and thus the full moon is “two seasons advanced” in angular declination relative to the current location of the Sun.  Since the Sun is shining over the equator on the autumnal equinox, the full moon will have a corresponding zero declination over the eastern horizon at sunset (6 PM standard time).

I hope you enjoy the You Tube video as much as I did.  Click on the picture to learn how it was taken.

 

Does our sun have an “evil” twin?

Does our sun have an “evil” twin?

Richard Muller, a scientist at the Lawrence Berkeley National Laboratory thinks so.

Since astronomers estimate that 60 to 70% of the stars in our Milky Way Galaxy reside in a double star system, it is more likely than not that our sun also has a companion star.

Muller sites that paleontologists have noticed that mass extinctions on earth have occurred regularly every 26 million years, and he hypothesizes that a dim red dwarf star, named “Nemesis”, about 1/10 the mass of the sun disturbs the orbits of the Oort cloud comets as it goes through it in its 26 million year orbit around our sun, hurling thousands of comets per year toward the inner solar system for about one million year span on each orbit. Eventually, one or more of them hits earth causing a mass extinction. He estimates that Nemesis will return in 10 million years. Other evidence includes the discovery of another planet named “Sedna” in 2003 by Michael Brown of Caltech which resides in a region where astronomers think no planet should exist since it is three times farther from the sun than Pluto in a very elliptical orbit. What pulled it out this far?

So what is the average distance of Nemesis’ orbit around our sun? Using Kepler’s third law, (period2 = semi-major axis3), Muller thinks that Nemesis’ average distance from the sun is 1 light year.

Is anyone looking for Nemesis? The answer is yes. NASA is using an orbiting wide field infrared telescope explorer called “WISE” in its hunt for the evil twin. So far, no luck.

However, something is disturbing the Oort Cloud comets right now. Evidence shows that a disproportionate number of comets is coming from one region of our sky now.

George Tanyk

Astronomy Instructor

Are Real Numbers Real?

Something that has annoyed me for some time is the idea of taking limits as delta x or delta t go to zero.  This is only physically real if space and time are continuously variable (possible to be divided an infinite number of times).

While it is true that physicists have not been able to detect a “grain” to space or time (better, spacetime), with space and time showing no quantized characteristics down to 10 to the minus 18 cm, and 10 to the minus 28 sec respectively, nevertheless, logically, it seems obvious that they are both quantized.

Further, as Paul Davies notes in his book “The Cosmic Jackpot”, if our universe can hold only a finite number of bits, how can the universe quantum mechanically compute so-called real numbers?  He quotes Gregory Chaitlin, of IBM, who says: “Why should I believe in a real number if I can’t calculate it, if I can’t prove what it’s bits are, and if I can’t even refer to it?…The real line looks more or more like a Swiss cheese.”

Food for thought (pun intended).

Blinding Lights, Losing Light

If you had the misfortune of driving west at sunset this last Saturday, September 22, then you experienced one of the notable characteristics of equinox days, namely that the Sun sets due west (cardinal west) for everyone on Earth.

Another interesting characteristic of equinox days is that the length of day is roughly 12 hours for everyone on Earth.  This is because the Sun is shining directly over (is zenially shining over) the equator.  This means that the terminator of the Sun’s light on Earth goes directly through the north and south poles of our beloved planet.  So everyone, rotating on their latitude circles, experiences 12 hours of sunshine, and 12 hours of twilight and night.

Because the Sun is shining directly over the equator, we see it descending due west, regardless of where we are on Earth.  Here in Chicago, pointing to the Sun at sunset means pointing to a point on the equator 180 degrees west longitude (aka the international date line).  Looking on the globe, this is around Howland island, where Amelia Earhart’s plane went down.

Put another way, when we Chicagoans point west, we are not really pointing along the latitude circle we live on: instead we are pointing along a great circle arc from Chicago to Howland island.

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Because of Mr. Kepler’s second law of planetary motion, we know the Earth is moving faster through its orbit as we approach Winter Solstice (when Earth is roughly closest to the Sun), so concomitantly, we expect to lose quite a bit of time per day.

And losing time we are.  Right now we are losing 2 minutes and 47 seconds per day.  Since September 1st (the first day of meteorological Fall, a mere 3 weeks ago), we have lost an astounding 57 minutes of direct sunshine.  By the time Winter Solstice arrives (December 21), we will be down to the depressing amount of 9 hours and 7 minutes of direct sunshine.

One consolation: the amount of indirect lighting (twilight) stays the same year round, as it is a function of latitude only.  So we always have about 30 minutes of civil twilight in the morning(aka dawn), and 30 minutes of civil twilight in the evening (aka dusk).

Oddly, every day is an equinox day for people who live on the equator.  Their dawn and dusk twilight times are only 17 minutes each.

One last equinox observation: on an equinox day, you can “see” your latitude with the setting Sun.  The angle the Sun’s celestial path makes with due west and a line vertically upward from it is your latitude.

Click on the image to learn more.

To view sunrise and sunset times for Chicago year round, click here.