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Does the Venus Transit Cause Floods?

June 21, 2004

image of 1882 transit On June 8, 2004, Venus passed directly between the Earth and the Sun. From the Earth, it was like a mini-solar eclipse, with the black disk of Venus taking about six hours to slowly make its way across the Sun's bright face. I actually had a chance to see it, and it was a truly amazing sight.

But according to one Chinese scientist, it was even more amazing than that. Geng Guoqing, who works with the Special Committee on Natural Calamities Forecasting, a part of the China Geophysics Society, says that the Venus transit has an effect on the Earth. He wrote an article for the "Science and Technology Review" in which he claims that there is a "clear correlation" between transits of Venus and the flooding of the Yellow River!

I cannot find direct links to the article, unfortunately, so I have to rely on news reports of it (like here, here, and here). I will be careful and say that without reading his article, I cannot be sure of his methodology. However, as a scientist and someone who investigates claims like this, I must say I am extremely skeptical.

The news reports say he looked in historical records dating back 2187 years (the Chinese are known for keeping records a long time!), and found that the Yellow River flooded at the same time as the Venus transits. I suspect this is true. But just because two things happen at the same time does not mean they are related! So is Geng's finding meaningful?

I strongly suspect not. For one thing, the Yellow River floods all the time, and I mean all the time. It's nicknamed "China's Sorrow" for a reason! A quick google search revealed lots of history of the river. The Yellow River Flooding page, for example, says that since 602 BC, the river has flooded its levees more than 1500 times. That's a lot, more than once every other year! It also says major floods happened in 1194, 1642, 1855 AD; in none of these years was there a Venus transit.

Furthermore, according to this page from the China Daily, more than 70% of the floods occur between July and August. Due to the way the Earth's and Venus's orbits work out, transits can only occur in late May to early June, and late November to early December.

So clearly, the Yellow River can flood all on its lonesome, without Venus's help.

The other problem is causation. What could Venus do to cause such a flood?

image of transit from NASA's TRACE observatory In a phrase, not a lot. In the news articles, Geng speculates that perhaps Venus blocking the Sun's radiation might affect the river somehow. However, I'd say no way. During a transit, Venus blocks about 1/1000th (0.001, or 0.1%) of the Sun's light. That's a teeny weeny amount. You get a lot more coverage from clouds! Hey, maybe it's because Venus blocks the light before it gets to the Earth! Huh-uh. We'd see correlation between solar eclipses and flooding then, and no one has reported that. But maybe solar eclipses don't last long enough to see it! I still say no way. Think of it this way: every night, the bulk of the Earth itself blocks 100% of the Sun's light, and the Yellow River doesn't flood every night.

Maybe it's not radiation, but gravity! After all, during a transit, Venus has to be as close to the Earth as possible, since it's between us and the Sun. In fact, this is when Venus is closest, getting about 40 million kilometers (25 million miles) from the Earth. However, that's still a long way off, and its gravity is very weak. Its gravity is only 0.006 times that of the Moon's, and its tides are only 0.00005 of the Moon at that distance (I calculated this as part of my Planetary Alignment page). This is incredibly small. Remember too, the gravity from the Moon changes because the Moon orbits the Earth in an ellipse. Sometimes it is closer, and sometimes farther. The Moon's gravity changes by about 25% every two weeks! So adding Venus to that is a tiny effect, and cannot cause any real, measurable changes here on Earth.

My conclusion: Venus has nothing to do with the Yellow River flooding. The flooding happens far too often, while transits are relatively rare. Also, there is no clear (or even vague!) way that Venus could cause such an event.

My other conclusion: just because you read something in a newspaper quoting a scientist doesn't mean that it has anything to do with reality! Even scientists can be wrong.

©2008 Phil Plait. All Rights Reserved.

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