Bad Science

Ever wondered why the Moon is bigger when it's near the horizon? (Atmospheric refraction, right?) Or why water swirls round sinks clockwise in the northern hemisphere (or is that anti-clockwise)? Or why you can stand an egg on end during an equinox?

Well, these are all myths. I get a lot of questions here -- which I'm always glad to get, and try to answer -- and a surprising number of them refer to these old stories. This is largely the fault of the media, who, unfortunately, often reproduce them without research or even thought. Fortunately, a real astronomer (unlike me), Phil Plait, has created the excellent Bad Astronomy website, which deals with these stories and many, many, more. I highly recommend it -- it's very entertaining reading.

Meantime, here's my take on some of the Bad Science issues that seem to keep coming up.

The Young Earth

Elsewhere in this site I make the bold and controversial statement that the Sun is billions of years old. Actually, I didn't think that it was particularly bold or controversial, until I got taken to task by some people who think that the Earth is much younger than that -- on the order of thousands of years, not billions.

I've put together my view on why I think the conventional scientific outlook is the correct one. I've tried to touch on some of the main areas supporting this view, and the result is big enough to warrant its own page.

Expanding Moons

If you look at the Moon as it rises or sets -- particularly the full Moon -- you'll see that the Moon is much larger when it is close to the horizon than when it is high in the sky. Like me, you may have been taught in school that this is due to the refraction of the Earth's atmosphere; when the Moon is low, you are looking at it through more of the atmosphere, so it is magnified more.

Nice theory -- but untrue. The Moon is the same size, regardless of how high it is; the apparent change in size is just an optical illusion. This illusion is remarkably persuasive, but you can easily prove for yourself that it's false -- take two photos of the Moon, one when it is low and huge-looking, and one when it is up in the sky and relatively tiny. Use the same camera, lens, zoom settings, etc. Then measure the photos -- you will find that the two moons are the same size.

The reason why this illusion is so effective is actually very subtle. The Bad Astronomy page can point you to some good explanations, though. But optical illusion or not, an eclipsed Moon close to the horizon should still look spectacular! Just don't expect your photos of it to be as good as the illusion.

Eggs on End

Lots of people know that you can stand an egg on its end during the equinox. Stands to reason, dunnit?

Are you kidding? Why on earth would the balancing ability of an egg be affected by the position of the Earth in its orbit? And why eggs in particular? This daft story overwhelmingly fails the common sense test. I'll let the Bad Astronomy page tell you why this egg is rotten.

Swirling Water

Lots of visitors to equatorial regions have seen -- in exchange for money -- a demonstration of the old story that water swirls down plugholes anti-clockwise in the northern hemisphere, clockwise in the southern. Apparently, this effect can be demonstrated within yards of the equator.

This is an interesting myth, in that it is based on reality -- in fact, in a very abstract and theoretical sense, it's essentially true. But does this force really affect the water in your sink?

Let's try a little quantification here. The coriolis effect, as it's known, is caused by the Earth rotating under the observer. Yes, it's a real effect, but it is most noticeable (by far) at the poles, where the Earth is spinning under the observer; not at the equator, where the Earth is going sideways under the observer (putting it crudely).

This effect also affects a pendulum, if it is set up to eliminate outside interference -- ie. a Focault's pendulum. Set up a free-swinging pendulum at the north or south pole, and you will notice that the line of the pendulum's swing turns around once in a day. (Specifically, a sidereal day -- 23 hours, 56 minutes, 4.06 seconds.) Given that water swirling around a bowl probably does one rotation in a couple of seconds, how much of the water's motion is due to the coriolis effect? The answer is very little -- in fact, almost none.

It gets worse the farther you are from the pole; and closer to the equator, the effect diminishes very rapidly indeed. Within a mile of the equator, the pendulum would rotate once in 82 thousand hours -- an almost undetectable effect! Within ten yards of the equator, it would take 50 million hours for the pendulum to complete one rotation; and right on the equator, the effect is absolutely nonexistant. The effect of this on a bowl of water anywhere near the equator is effectively zero. The demonstrations people see of this (in exchange for tips) are simply faked. My congratulations to the fakers for so cunningly depriving tourists of a little cash -- and for using genuine physics as the basis for doing this!

Once more, don't take my word for this -- the Bad Astronomy page has more perspective on this -- including how to conduct your own faked demonstration!

Planetary Alignments

One rather pathetic story that surfaces every few years is that a "planetary alignment" will cause an immense gravitational pull on the Earth, which will knock it out of its orbit and then tear it apart by tidal forces. Sounds a bit scary, doesn't it?

Of course, the minutest portion of common sense would allow any remotely intelligent being to see this for what it is. Apart from the fact that the gravitational influence of the planets on the Earth is microscopic (it's quite easy to calculate), you may have noticed that many of these predictions have come and gone recently, and yet the Earth is still here. (You can confirm this by checking for a big, round Earthy thing directly under your feet. It's about 8,000 miles across, so quite hard to miss.) In fact, the Earth has been here for billions of years; these so-called "alignments" (they're usually pretty vague) come and go relatively often, and the Earth has survived them all so far.

A more astrologically-inspired alignment -- the "Grand Cross" -- coincided with the total solar eclipse of August 11, 1999; this was apparently an event of huge astrological significance, although I couldn't find any clear description of what the significance actually was. Maybe it was just generally Significant.

BBC: Armageddon....Again

In this case, the Sun and moon were directly opposite Uranus (well, almost) and at right angles (nearly) to the line from Saturn to Mars. This heralded the end of the world, or things chugging on as always, depending. I should point out, though, that with 9 planets and the Sun and Moon going around all the time, cross formations are pretty common. Looking at the diagram, you'll see that this one doesn't line up perfectly, although it's pretty close. Anyway, nothing of any outstanding significance happened, as far as I could see.

The Bad Astronomy pages have much more detail about the myths of planetary alignments.

Astrology

You may have guessed that I'm not particularly into this astrology and superstition stuff. But then I was born on 28 November, which makes me a Scorpio, and Scorpios don't believe in astrology...

Looking at that date, you might be thinking I've got that wrong, but no, it's all the astrologers in the world who have it wrong -- when I was born, the Sun was in Scorpius, not Sagittarius (or maybe it was in Ophiuchus, depending on how you look at it). The Bad Astronomy Zodiac page has more.

One more thought about astrology -- on September 11, 2001, an unprecedentedly traumatic event occurred which was witnessed within a space of a few hours by a huge proportion of the world's population. Billions of people were profoundly affected in an emotional shockwave which encompassed the entire world. The world's largest superpower was shaken to its foundations -- and thousands of people died. If astrology is good for anything at all, how come no-one saw that coming?