This is an interesting thought experiment and it involves statistics and some figuring, so I welcome any of my smart friends or anybody who cares to think about it to chime in here.

Assume that sentient civilizations with the ability to transmit some form of radiant communications signals (radio, light, whatever) started appearing in our galaxy as early as 4.5 billion years ago (when the Earth was forming), and assume that they continue to appear (each on its own evolutionary trajectory) for another 4.5 billion years.  Further assume that over this timespan of 9 billion years a total of one million different intelligent civilizations begin transmitting radiant communications. After a random time period of 100 to 1000 years each civilization stops transmitting radiant signals, either because they move on to a better technology that does not require radiant communication (pretty much necessary for interstellar communications) or the civilization dies out.  Finally given that our galaxy's diameter is about 100,000 light years, assume that any of these civilizations when transmitting would be at some random distance from us which does not exceed 100,000 light years (yes I know that's a little big since we aren't at the very edge of the galaxy, but bear with me.)

Now, here we are, smack-dab in the middle of that timescale, halfway between year 1 and year 9 billion.  We turn an array of radio telescopes to the sky and listen in all directions simultaneously, constantly, for a period of 1,000 years.

Is our sky silent?  Or is it noisy?  With a million civilizations out there at some point or another, all sending signals out at different times, what are the chances we would hear none of them at all even if we listen for 1000 years?

I threw together a crude simulation last night to try and answer this question, and I have a result which you might find surprising, but I'm curious to know what other people think first.  Care to venture a guess?  Or perhaps create your own sim and see what results you get?  I'll post my results tomorrow.

8:07 PM EDT today, March 20, marks the Vernal Equinox and the official start of Spring 2007.  Today at that time the sun will pass over the equator from the southern hemisphere to the northern.   This is what you probably already know.

But I learned a couple of things today that I didn't know.  First is that "equinox" means "equal night", which makes sense because on the equinoxes the length of day and night are exactly equal.  Here in the northern hemisphere the days will continue to get longer until the Summer Solstice at 12:06 PM EDT on June 21, 2007.  Since the last Autumnal Equinox we in the northern hemisphere have been getting less direct light than the southern hemisphere.  As of 8:07 we will officially begin receiving more direct light than the southern hemisphere.

The other thing I should have known is that, for the southern hemisphere, this time will mark the Autumnal Equinox.  I mean, I was aware that the seasons of the south are the reverse of the seasons of the north, winter here summer there, fall here spring there, but it just never occurred to me that the solstices and equinoxes were similarly flipped.  Silly that should never have occurred to me.

Oh, one other little thing I learned is that "solstice" means "sun stands still".  Since the solstice marks when the sun stops moving north or south and reverses direction, that's a very sensible thing to call it.

Another interesting tidbit, apparently the great Sphinx of Egypt is oriented so that it exactly faces the sunrise on the morning of the Vernal Equinox.

Continuing in the vein of yesterday's post, I have a few more random thoughts to share...

Survivorman
Perhaps you've never seen this show, it's on The Science Channel (not to be confused with Discovery Channel or The Learning Channel).  I really enjoy it.  The premise is simple.  In each episode they take Les Stroud and dump him in the middle of nowhere with meagre supplies and about 50 pounds of camera equipment.  His only mission is to survive for seven days before the crew returns to pick him up.  He's not allowed to break down the camera equipment and use it for survival, and he does all the filming himself.  I can only imagine what an incredible amount of effort is involved in shooting himself walking past the camera or trudging off into the distance, only to have to return and get the camera.  This show strikes me as one James would enjoy.  I've seen this poor guy dumped in the arctic tundra, the swamps of Georgia, some desert out west somewhere, even one episode where he had to survive in a life raft at sea for seven days. You can order season 1 of the show on DVD if you are interested.  I discovered this show during my many days of bedrest over the last month or so.

North and West of the City...
I'm sick of this phrase.  I hear it all the time during weather reports, as in "2 to 5 inches of snow are expected in the Boston area, while areas North and West of the city could receive as much as a foot."  It's snowing today.  Unlike those in and south of the city, there's no rain following the storm here... it's just piling up.  Day before St. Patrick's day and the snow is just dumping down.  *sigh*

Cosmos and Carl
I miss Carl Sagan, and I loved Cosmos when I was a kid.  One of my best memories of childhood is sitting in the living room with my Dad watching Carl explain history, other dimensions, outer space, the doppler effect, and various other intriguing things.  Pat and I both talked recently of trying to find the Cosmos series on DVD to watch with Lynnea (though it might be too slow paced for her.)  Amazon has it, if you are interested.  One of my favorite segments of that series was when Carl explained what it would be like for two dimensional creatures to encounter a three dimensional one, as a way of explaining what a fourth dimension might be like, as a mechanism for explaining the concept of a curved universe as it relates to the big bang.  The two dimensional creatures were called "flatlanders" because they lived (appropriately enough) in Flatland.  I finally found that segment on YouTube, but it is included in a larger 10 minute video.  You can watch it here, the part about Flatland starts about 3 minutes in, after a discussion of Hubble's discovery that the universe was expanding.  In the next segment, Carl ties in the curved universe and questions about the existence of God.  It's slow paced but wonderfully done.  I really should pick that series up and watch it again as an adult--I've no doubt I'd learn more this time.

Destroying a Career
As you probably know, Valerie Plame testified today before House Oversight and Government Reform Committee and finally had a chance to speak out on her cover being blown by an administration with hopelessly misplaced priorities.  One of the saddest things about this, as far as I can see, is that her CIA career as a covert agent is basically over at this point.  That's got to be infuriating for her.  I can't imagine what that must be like.  From her testimony today:

..."My name and identity were carelessly and recklessly abused by senior officials in the White House and State Department. [...] I could no longer perform the work for which I had been highly trained." [...] Under questioning, Plame recounted feeling "like I had been hit in the gut" on the July 2003 morning when she saw a newspaper story by syndicated columnist Robert Novak identifying her...

Pace and the Unbagged Cat
Smooth one General, really smooth.  For those of you who haven't heard, the chairman of the Joint Chiefs of Staff, General Peter Pace, stepped in it on Tuesday by saying he supported the Pentagon's ban on gays serving openly in the military because homosexual acts are "immoral".  Way to go, dickhead.  There are thousands upon thousands of gay people serving in our great nation's military right now, many of them putting themselves in harm's way.  Thanks for telling them that they're a bunch of immoral perverts.  General Pace, for his part, has refused to apologize for the remarks, and has only gone as far as to say that he regrets making them.  I'll bet he does, but only because it is inconvenient for him now that the cat is out of the bag.  As far as offending the gay troops who've been valiantly serving over the last four years of this misguided war?  It's clear what Pace thinks of them.  I never understood the ban on gays in the military, and I understood don't-ask-don't-tell even less, except that it allows good soldiers to serve a country that needs them, regardless of their sexual orientation.  And the same people that screeched in 1993 that we couldn't let gays in are screeching today that we can't let gays serve openly, for the same stupid reasons--because it would cause a breakdown in unit cohesion on the battlefield.  What a bunch of bullshit.  I'm sorry but a guy brave enough to crawl across a battlefield under fire while trying to avoid landmines isn't going to be worrying if the guy behind him is checking out his ass.  Give me a goddamned break, PLEASE.  Here's a thought, I won't ask then next time something as stupid as that enters your mind, and you don't tell, okay? (As a sad but not unexpected sidenote, conservatives are leaping to the General's defense.)

Panda's Thumb has a post with links to YouTube videos of a lecture given by Neil deGrasse Tyson (an astrophysicist of some reknown).  It's worth watching.

It was interesting to see and hear Mr. Tyson speak with passion about discovery and the "spiritual" feeling that comes from looking out into the universe and coming to the realization how we are all connected to it and part of it.  Given how every atom in our bodies which is heavier that hydrogen was forged in the cores of stars, he notes "We're not just in the universe, the universe is in us."

Perhaps most wonderful to me, was to hear confirmation of my crackpot ideas about what "spiritual feelings" are and why atheists can have them coming from Mr. Tyson.

The speech is about 16 or so minutes long, but it is worth seeing.  I found Mr. Tyson's conviction and depth of feeling about our connection to the cosmos touching.  I think in some small way I know how he feels.  When I finally get home in the evening from work I can't resist looking up at the stars for at least a moment or two before I walk into the house.  And whenever I do I feel a kinship to those distant stars.

It's nice to know someone else does too...

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Here's a few science-related news stories that have caught my eye in recent days...   more »

Sorry friends, been busy these last few days. Here's a short recap of what's been going on in my life...   more »

Well the votes are in, and Pluto has gotten the axe as have the other new planets that originally were going to be included. Our solar system has eight planets. Pluto is reclassified as a "dwarf planet" along with Ceres and 2003 UB313...   more »