Summer solstice: it's worth celebrating

Today is June 21. It's summer solstice, the longest day of the year in the northern hemisphere.

For my birthday last May, I asked for a globe. I wanted to be able to illustrate solar-system phenomena to my kids, as well as show them the true geometry of our world. For example, the shortest path from Vancouver to England passes through the arctic circle.


A couple days ago, I pulled the blinds over the window, grabbed a lamp and my globe, and showed my 3 kids what summer solstice means, why it happens, and how it's linked to the seasons. It's the day when the earth's spin axis is maximally inclined toward the sun. Here's another - more technical - way of putting it. Imagine a line connecting the sun and the earth, passing right through the centre of each. Now draw another line along the earth's spin axis, also through the centre of the earth. Those two lines form an imaginary plane. Another imaginary plane is formed by the earth's orbit around the sun. A solstice occurs when those two planes are perpendicular.

You might have heard of the arctic circle, equator, and the tropics. These earth zones are all defined by the earth's tilt and are related to the solstice.


(Taken from this video.)
The tropics are the range around the equator, from 23.5^o north (Tropic of Cancer) to 23.5^o south (Tropic of Capricorn), where the sun is directly above at some time of the year. We never get that in Canada... we're not in the tropics. The closest we get is today, summer solstice.

Finally, here is a picture of Tricia on our honeymoon.


What the hell does that have to do with summer solstice, you ask? Notice that her shadow is directly below her. This picture was taken in Mexico right around the time of the summer solstice, the only time I've seen the sun directly overhead.

(And Trish isn't too hard on the eyes either. :-)

Unintentionally ironic

Though it makes me gag, I sometimes listen to the podcast "Intelligent Design The Future". Grammar hiccups aside, this podcast is simply a propaganda tool of the Discovery Institute. Their function... to help those who can't consolidate their religion with the theory of evolution, supplying fodder to suspend their disbelief long enough to die a believer. They combine muddy thinking with interviews of "scientists", philosophers, medical doctors -- anyone with perceived authority -- and agree that the theory of evolution is flawed, so the universe must be designed by God.

On the episode of Sept. 25, 2009, Bruce Chapman interviews "skeptic" David Berlinski. They proceed to pat each other on the back, congratulating themselves for being on the winning team. Then they whine about how creationists ID proponents are being bullied by the Darwinists. Berlinski likens it to the crumble of the geocentric worldview. The dominant worldview used to be that the earth was the centre of the universe, geocentrism. But people like Kepler and Gallileo proposed that the sun was the centre of our solar system, a view called heliocentrism. These poor scientists were victimized for their dissenting opinions. In Berlinski's analogy,

geocentrism	=	dominant evil bully	=	theory of evolution
heliocentrism	=	marginalized noble truth	=	intelligent design

His analogy is based on good versus evil. The evil geocentrists eventually lost the fight to the noble heliocentrists because the evidence overwhelmingly supports the idea that planets revolve around the sun. Thus, Berlinski's analogy concludes that evolution is evil, and ID is good.

But let me frame the analogy in a different way, based historical beliefs versus evidence. At the time, geocentrism was the historical view, but it gave way to heliocentrism because of the evidence. Intelligent design (a.k.a. creationism) was the historical view, but it gave way to the theory of evolution because of the evidence. In my analogy,

geocentrism	=	outdated historical view	=	intelligent design (creationism)
heliocentrism	=	view supported by evidence	=	evolution

The irony... Berlinksi's use of the analogy actually does shed some light on what's going on. In the podcast, he reminds us that Gallileo was persecuted by the CHURCH for his dissenting opinions. The take-home message: religion will do whatever it can to stifle dissension, even if it means denying evidence.