Spectacular show to grace the Northern skies tonight.

Here in America, summer is coming to an end. The fall equinox will occur tonight, September 22nd, at 11:09pm EDT (9:09pm here in Boulder). The full moon that occurs closest to the first day of autumn is called a Harvest Moon, and this year we are getting a rare treat: a "Super Harvest" Moon on the same night as the equinox! Not only that, but both Jupiter and Uranus are near opposition this week, which means that they are positioned exactly opposite the sun in our sky. Jupiter appears to the naked eye as an extremely bright object next to the moon, and one can just as easily see Uranus with simple binoculars or a small telescope. Tonight, the two will appear just one degree apart, a phenomenon known as conjunction. Altogether, it's quite the exciting week for astronomers and stargazers alike.


Harvest Moon, Sept. 25th, 2007. Image courtesy of joiseyshowaa.
An equinox occurs twice each year, at the moment the sun passes directly over Earth's equator. It is commonly believed that on this date, the day and night are of equal length; however, this is not strictly true. In fact, for those observers away from the equator, there is always a slight excess of daytime on the equinox. The moment at which light hours are equal to dark hours is actually called the equilux. For most people on Earth, the equilux occurs just before the vernal equinox and just after the autumnal equinox.

Traditionally, the vernal equinox occurs around March 20th or 21st, while the autumnal equinox occurs around September 22nd or 23rd. In between the equinoxes, the Earth's axial tilt causes one hemisphere to receive more of the sun's energy than the other. In the Northern Hemisphere, we experience summer when our half of the globe is tilted toward the sun and winter when it is tilted away. At the equinoxes, however, the Earth is tilted in the direction of its orbit, rather than in the direction of the sun. This means observers at equal latitudes above and below the equator receive equal amounts of sunlight.


The Earth's tilt accounts for a seasonal climate in the mid-latitudes. Counterclockwise from top left: summer solstice, fall equinox, winter solstice, spring equinox.
Image courtesy of Tau'olunga.
So tonight, as the Earth shows its full-frontal glory to the sun, make sure to watch the evening unfold. The Harvest Moon will appear enormous on the eastern horizon, and the light from both sunset and moonrise will create a unique and rare kind of twilight. This eerie glow, together with Jupiter shining brightly just below the full moon, should create quite a memorable sight for stargazers on the northern half of the globe. Happy fall!

Hawking debunks "myth" of God.

Stephen Hawking is causing a stir. In a book excerpt published in tomorrow's Wall Street Journal, Hawking addresses the ever-controversial topic of science and religion. His take? The presence of a Creator is rendered completely unnecessary by modern science.

Hawking cites the so-called anthropic principle as the reason many people believe God must exist. The anthropic principle comes in two forms: the "weak" anthropic principle, which states that we developed on Earth because specific factors in our environment allowed us to do so, and the "strong" anthropic principle, which states that our existence as intelligent life-forms mandates the parameters inherent in the laws of nature themselves. For most, the weak anthropic principle is easily debunked. There are plenty of environments in the universe where intelligent life did not develop; we naturally find ourselves in one in which it did. This planet wasn't fine-tuned for the conditions of human life, human life was fine-tuned for this planet. Essentially, we are a statistic. Most people would agree with that in the context of the universe at large.

The controversial part of Hawking's statement, however, is his belief that the strong anthropic principle can be logically unravelled in the same way. The problem with the strong anthropic principle is that we have nothing to compare it to. As far as we are concerned, our universe is the only one. There are a variety of finely-tuned physical constraints inherent in the laws of physics, without which we would not exist. For instance, if gravity were any weaker, stars would never have formed in the early universe. Meanwhile, if gravity were stronger, our sun would have burned through all of its hydrogen already. Take your pick: the strength of the fundamental forces, the precise ratio of matter to antimatter, the stability of heavy elements like carbon, even the number of spatial dimensions in the universe; any of these is at the least, peculiar, and for some, explicit proof of God's existence.

But with the dawn of new cosmology - specifically evidence that points to the existence of multiple universes - Hawking believes that this principle too can be explained away. Just as there are many stars in our universe that are not orbited by planets, and many planets in our universe that are not hospitable to life, there are also many universes within our multiverse in which these physical parameters do have different values, and in which intelligent life was never able to form. Once again, we are a statistic. A Creator did not concoct a universe for our benefit; we evolved as a consequence of the specific universe we are in. Human life was inevitable, not essential. Or so Hawking believes.

First, let me say that I have no problem discussing science and religion in the same sentence. In fact, I think it can be extremely valuable. For my part, I know that science has profoundly affected and enriched my own spirituality. However, I don't think that Hawking's bold statement is going to do much to heal the schism between fundamentalist religion and modern science. There are altogether too many people who actually believe the Earth was created 6000 years ago, and who blatantly ignore scientific fact because they see it a contradiction of their own religious beliefs. Don't get me wrong - I'm a big believer in grey areas, but that is just absurd and ignorant. To be sure, a dialogue needs to be initiated, and a mutual one at that. Evolution absolutely needs to be taught in schools, but not at the expense of prayer or spiritual pride. Unfortunately, while I admire the conviction, I just don't think Hawkingism is going to win any new converts.

Of strings and things.

Imagine a tiny thread of material, so infinitesimal that it is more than a quadrillion times smaller than a proton (no matter who you ask). Now imagine that same tiny thread being present at the heart of every single particle that makes up every atom that makes up every bit of matter we can observe in the universe. Got that? Good. Now imagine that the identity of every subatomic particle is determined by the precise vibration pattern of the tiny strand of material within; that is, its precise vibration pattern... in ten dimensions. Welcome to the world of superstring theory, one of the most potent contenders for the long sought-after "Theory of Everything" that will combine general relativity and quantum mechanics into one, all-inclusive framework.


As always, xkcd cuts right to the heart of things.

Simply put, string theory elegantly exploits the physical principles of music; that is, plucking a string will generate a different sound, depending on the properties of the string and how hard it is plucked. Some variations of string theory predict that strings are open, with two endpoints, while others predict that strings are closed, like a loop. Either way, it is the specific modes of vibration, or excitations, of the string that give rise to different kinds of particles.

String theorists conceive of elementary particles as having a very small dimension of length, rather than being point particles with no length, width or height. It may seem like a simple change, but this assumption neatly does away with the problems scientists have always faced when trying to formulate a quantum theory of gravity. There is only one problem: scientists have had no way to test the predictions of string theory. Because strings are thought to be so incredibly small, particle accelerators would have to operate at astronomically high energies to probe deeply enough into the subatomic realm. We simply don't have the technology.


Not even CERN has the power to probe the mysteries of string theory.
Image courtesy of Image Editor.

But a new discovery by a researcher at Imperial College London might be about to change things. According to Professor Mike Duff, the math scientists use to apply string theory to black holes is exactly the same as the math that is used to describe quantum entanglement between three particles. In a paper published in this week's Physical Review Letters, Duff and his team of colleagues detail an experiment involving four entangled particles and predict the result based on the mathematics of string theory. If researchers can manage to carry out this experiment, and if the results agree with the team's predictions, string theory will finally have the experimental backing scientists have been seeking for decades.

Currently, there seems to be no practical connection between quantum entanglement and the string physics of black holes. Even Duff acknowledges that they are "unexpected and unrelated" areas of physics. Perhaps researchers are about to discover more than they bargained for. Or perhaps all of this is simply an odd, yet serendipitous, coincidence.