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Sky Lights: Confused About Your Direction?
Discover Magazine ^ | 9-2006 | Bob Berman

Posted on 08/20/2006 11:12:01 AM PDT by blam

Sky Lights: Confused About Your Direction?

If you lack a sense of personal trajectory, astronomers can help.

By Bob Berman

DISCOVER Vol. 27 No. 09 | September 2006 | Space

Throughout most of history, humanity hasn't had a clue about where it's going. The idea that we're all being whisked through space aboard a spinning Earth was alien even to brilliant thinkers like Aristotle and Pythagoras. The first to argue that our planet is in motion was Heracleides, who in 350 B.C. maintained that Earth turns on an axis. A century later, Aristarchus of Samos earned a lot of laughs for saying that we go around the sun, not the other way round.

Not until the Renaissance did educated people accept that Earth rotates daily, spinning us all steadily eastward. If you've got a calculator handy, you can quickly determine your speed: Multiply the cosine of your latitude by 1,038. For instance, if you live in Denver, latitude 40, punch in "40," hit the cosine key, and multiply. Answer: 795 miles per hour. You are breaking the sound barrier just by sitting on your couch.

That's only the beginning of your astronomical movements. As Earth orbits the sun, it plows through space at 18.5 miles per second, or about 67,000 mph. At sunrise, the direction of Earth's travel is pretty close to straight overhead. The velocity is not constant, though, because Earth follows an elliptical path and accelerates as it moves closer to the sun. Counterintuitively, the top speed occurs in early January, the minimum in July.

Nearly a century ago, American astronomer Harlow Shapley enlarged the perspective on our motion. He discovered that we're not sitting at the center of our galaxy, the Milky Way. Instead, we're about two-thirds of the way to the edge, making a huge loop around the galactic core every 250 million years or so. Astronomers before Shapley had already determined that the sun and its planets are moving toward the constellation Hercules at about 12 miles per second. Today we know that this is just a sideways drift superimposed on our main forward speed around the Milky Way—a brisk 144 miles per second, about one-thousandth the speed of light. That motion carries us toward the bright star Deneb, which is high overhead this month. We will be where Deneb is now, 1,600 light-years away, in a million and a half years.

Still, we're not finished. Our entire galaxy rushes toward the Andromeda galaxy at 80 miles per second. Zoom out farther and our local group of galaxies is yanked toward "the Great Attractor," a mysterious concentration of mass beyond the constellation Virgo. Even big telescopes can't really spot the source of the pull.

On the largest scale, everything is flying apart, a cosmic divorce dictated by the expansion of the universe in all directions. Measuring the exact value of that expansion yields hints about whether the universe will keep growing forever or will someday halt and then contract. Current studies say the expansion rate is around 14 miles per second for each million light-years of distance. Alien astronomers in a galaxy 100 million light-years away would see us whizzing in the opposite direction at 1,400 miles per second.

Or are they moving away from us? The usual interpretation is that the space between us is increasing, so everybody is moving and yet nobody is actually moving. That's another way of saying that there is no center to the Big Bang. It happened everywhere and nowhere. Perhaps all we can say for sure is that we've come a long way, yet we're still going nowhere—fast.


TOPICS: News/Current Events
KEYWORDS: about; astronomy; confused; direction; lights; sky; your
I'm getting motion sickness.
1 posted on 08/20/2006 11:12:04 AM PDT by blam
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To: blam
Perhaps all we can say for sure is that we've come a long way, yet we're still going nowhere—fast.

Now that's some pretty good word-herding.

2 posted on 08/20/2006 11:14:22 AM PDT by capt. norm (Bumper Sticker: Honk if you've never seen an Uzi shoot from a car window.)
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To: Molly Pitcher; kayak

ping


3 posted on 08/20/2006 11:17:15 AM PDT by lysie ("Lowering the price to be paid by aggressors virtually guarantees more aggression." Dr. Sowell)
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To: blam

Is this the Big Bong theory?


4 posted on 08/20/2006 11:20:47 AM PDT by outofsalt ("If History teaches us anything it's that history rarely teaches us anything")
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To: lysie

Thanks for the ping ... I think ... ;-)


5 posted on 08/20/2006 11:26:53 AM PDT by kayak (Praying for MozartLover's son, Jemian's son, all our military, and our President every day!)
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To: kayak
Going nowhere in a hurry. Story of my life.

/johnny

6 posted on 08/20/2006 11:33:16 AM PDT by JRandomFreeper (I'm a SysAdmin again. Kneel now and arise quickly to get to your tasks.)
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To: blam
mysterious concentration of mass


7 posted on 08/20/2006 11:35:33 AM PDT by P.O.E.
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To: blam

My head is spinning. It's a good thing the NASCAR race at Michigan is about to start. Still, an interesting read.


8 posted on 08/20/2006 11:37:29 AM PDT by FlingWingFlyer (Want to "feel safer?" Elect DemocRATS and then stick your head in the sand.- The DNC)
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To: blam

How soon before We run into something or visa versa??


9 posted on 08/20/2006 11:37:47 AM PDT by wolfcreek (You can spit in our tacos and you can rape our dogs but, you can't take away our freedom!)
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To: blam

I'm.....gonna.....puke


10 posted on 08/20/2006 11:38:55 AM PDT by driftdiver
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To: blam
Sky Lights: Confused About Your Direction?

Nah. Always choose Velux.

11 posted on 08/20/2006 11:41:36 AM PDT by RGSpincich
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To: blam
Earth rotates daily, spinning us all steadily eastward. If you've got a calculator handy, you can quickly determine your speed: Multiply the cosine of your latitude by 1,038.

For today's math refresher, work out how this reltionship is derived.

Hints: the circumference of the earth at the equator is 24,900 miles, by definition, a day is one revolution, no more, no less; Smartass astronomers need not get pickiyunish here...

Since there are 24 hours in a day, and 360 degrees, exactly, you can see that dividing 360 by 24 gives you exactly 15 degrees, the distance the surface of the earth travels in one hour.

But where did the 1038 come from? and where does the cosine come in?
Your latitude is the position of your city on the earth's surface, measured in degrees, from the equator.

12 posted on 08/20/2006 11:55:52 AM PDT by Publius6961 (MSM: Israelis are killed by rockets; Lebanese are killed by Israelis.)
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To: blam

Sky Lights: Confused About Your Direction?

Nah - I pretty much stick to the Right, has worked well for me up to now.


13 posted on 08/20/2006 12:07:13 PM PDT by ASOC (The phrase "What if" or "If only" are for children.)
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To: blam

I know you think you understood what I said. But what you think you heard is not what I meant. . . . I think.


14 posted on 08/20/2006 12:28:40 PM PDT by Quix (LET GOD ARISE AND HIS ENEMIES BE SCATTERED. LET ISRAEL CALL ON GOD AS THEIRS! & ISLAM FLUSH ITSELF)
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To: blam

Yet we each of us remain in the center of the universe.


15 posted on 08/20/2006 12:33:00 PM PDT by RightWhale (Repeal the law of the excluded middle)
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To: RightWhale

Me too. I expect to hear "Cyber Akhbar" during all suicide bombing from now on.


16 posted on 08/20/2006 12:38:13 PM PDT by Cyber Liberty (You try 355 days of sunshine per year and tell me how much you like it.)
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To: blam

Just remember: the Moon appears to be smaller than the Earth, but it is also farther away....


17 posted on 08/20/2006 1:12:02 PM PDT by Zman
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To: blam
According to the World Almanac, Deneb is twice as far away (3230 light years), so we can relax...it's going to take a lot longer before we get there. Anyway chances are Deneb will have moved so we aren't likely to hit it.

Deneb is tied for 19th-brightest star as seen from the earth (not counting the sun), but it's much further away than any of the other first- or second-magnitude stars, so it's much brighter than any of them.

18 posted on 08/20/2006 1:53:16 PM PDT by Verginius Rufus (Mega biblion, mega kakon (A big book is a big evil)--Callimachus of Cyrene , c. 250 B.C.)
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To: blam

Fortunately the human body has adapted to all this motion. However, the consumption of alcohol lowers your resistance to all the motion. So if you want to get an idea as to how it feels to be spinning in space, have a few stiff drinks until you can no longer stand upright. Then lie down on your bed and enjoy the sensation of hurtling through space in several different directions at once.


19 posted on 08/20/2006 1:58:52 PM PDT by SamAdams76 (I am a big fan of urban sprawl but I wish there were more sidewalks)
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To: SamAdams76
Fortunately the human body has adapted to all this motion.

So if it stopped would we all fall over?

20 posted on 08/20/2006 2:01:51 PM PDT by freedumb2003 (I LIKE you! When I am Ruler of Earth, yours will be a quick and painless death)
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To: SamAdams76
"Then lie down on your bed and enjoy the sensation of hurtling through space in several different directions at once. "

Been there and done that numerous times. I don't do that anymore though.

21 posted on 08/20/2006 3:13:56 PM PDT by blam
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To: blam
Thanks, blam! No doubt, this will come in handy -- sooner or later... '-)
22 posted on 08/20/2006 6:13:14 PM PDT by TXnMA ("Allah": Satan's current alias...)
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To: Publius6961
The 360 degrees and the 15 degrees per hour are more complications than are needed.

The 1038 is just 24,900 divided by 24. On the equator, you travel 24,900 miles in a day (since that is the earth's circumference), and there are 24 hours in a day. So you travel 24,900/24 == 1038 miles in an hour.

23 posted on 08/20/2006 6:35:05 PM PDT by ThePythonicCow (We are but Seekers of Truth, not the Source.)
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