As expected there was no disaster on May 5th, 2000, due to the planetary alignment. No polar ice shift, cataclismic eathquakes, or giant tidal waves. There will be other alignments and unusual planetary configurations from time to time in the future, and no doubt some people will claim dire consequences based on prophesy or strange theories.

The Solar System has been doing its thing for millions of years based on the rules of gravitation. Physical effects are caused by physical forces, and when a prediction is made based on prophesy but science doesn't back it up, you can bet the prediction will fail. In this particular case, any good high school physics student should have been able to figure out that the forces exerted on the Earth during this alignment would be nothing out of the ordinary and, in fact, be less than occur quite commonly.

I think it's reckless and harmful for some people to needlessly frighten the public with predictions about catastrophes whithout bothering to consult someone who could perform these simple calculations. Some even profitted by selling books and survivalist supplies, which I think is particularly shameful. We have enough to worry about in our lives without being afraid about catastrophes that can easily be proven won't happen.

The short answer is that there will be no unusual forces exerted by the planets on that day, and this planetary configuration won't cause any sort of disaster. Below I've detailed why and given some links to related sites.

I had heard rumors of a conjunction of the planets, also called The Grand Alignment, that is supposed to happen on May 5th of the year 2000, and that there would be disasterous consequences on Earth from the summed gravitational forces. Possible disasters included earthquakes, shifts in continental crust, and movement of the polar icecap causing tremendous tidal waves the world over. This sounded pretty unlikely, so I looked into it to see what was really going on. Here is what I discovered:

Apparently, this occurance was featured in the TV show Millenium and mentioned in one called Prophesies of the Millenium that aired on FOX. A group or company called The Survival Center has a web page devoted to this dire occurance, complete with a number of books for sale. Might as well make a few bucks before the the final catastrophe.

The graphic above shows the locations of the inner six planets on May 5th of the year 2000. It comes from a wonderful astronomy program called Skyglobe. The outer three planets aren't shown. Pluto is far down and to the left of the Earth and Uranus and Neptune are both down and to the right. The alignment isn't perfect, especially for Mars, but it isn't too bad. The Moon, not shown, is pretty well lined up between Earth and the Sun.

As far as having an affect on Earth, the absolute gravitational force from another body in space isn't really important. It's the tidal effect that makes a difference. Take for example the Moon and Earth. The Moon has a certain over-all pull on Earth, which can be calculated by assuming Earth is all smashed down to a point at its center. In actuality, the Moon pulls harder than that on the side of Earth closest to it and less hard on the opposite side. It's this differential in gravitational force that causes the tides. It also causes a minor deformation of Earth itself.

The force of gravity is inversely proportional to the square of the distance between two bodies. This means that at twice the distance the force is reduced to one fourth. Because the tidal force exerted on one body by another is the difference between the gravitational force at the close side and at the far side of the body, it is inversely proportional to the cube of the distance. Thus, at twice the distance, the tidal force is reduced to one eighth.

The closeness between the two bodies is much more important than their masses in contributing to the tidal force. For example, the force of gravity exerted by the Sun on Earth is about 180 times as great as that exerted by the Moon, yet the Moon causes a greater tidal effect because it is so much closer. Another way of thinking about this is to remember that the diameter of Earth is a much larger proportion of the distance to the Moon that it is to the Sun, so the differential gravitational force will be a larger proportion of the total gravitational force. To see why the Moon always faces us with the same side and why it is gradually moving away from Earth, take a look at Phil Plait's explanation.

The tidal effects caused by the Sun and Moon are not constant. Our orbit around the Sun is an ellipse as is the orbit of the Moon around Earth. This means that the distance between Earth and the Sun varies throughout the year and that the distance from the Earth to the Moon varies over each time it orbits us, which takes about 28 days. When the Moon is closest to the Earth (perigee) during its orbit, the tidal forces are stronger on Earth and when it's farther away (apogee) they are weaker. The same is true for the tidal forces from the Sun as we orbit it. Earth also causes tidal effects on the Sun and Moon, but that's not germaine to the matter at hand.

Now back to the situation on May 5, 2000. I made some calculations to find the tidal forces and the absolute gravitational forces exerted by each of these bodies in the positions shown. To simplify the work I assumed that they were exactly lined up, which they aren't quite, and I used each planet's average distance from the Sun. The differences these assumptions make in the results are very minor. I computed the gravitational forces as they would affect a 1 kilogram object on Earth. The planetary data came from a NASA site on the solar system.

Conclusion

What I discovered was that the tidal forces exerted on Earth from the five planets on the other side of the Sun are vastly smaller than those exerted by the Moon or the Sun. In fact, with the planets in the position they will be in on the big day, the largest tidal force from one of them will be from Jupiter, and it is about one five hundred thousandth the size of the tidal force exerted by the Moon on an average day! The difference in tidal force exerted by the Moon at apogee and perigee is about one hundred seventy thousand times larger than the total tidal force exerted by Jupiter when its on the opposite side of the Sun. Another way of looking at it is that the Moon is about 42,000 km closer to us at perigee than when it's at apogee. On the average, the tidal force caused by Jupiter when it's on the other side of the Sun is equal to the increased tidal force caused by the Moon moving one quarter of a kilometer closer to us. We are much less affected by the tidal forces exerted by these planets when they are on the other side of the Sun, regardless of their alignment.

The following table contains data about the gravitational forces, tidal and absolute, affecting Earth on that not-so-fateful day. For comparison purposes I've included data for the Sun and Moon when they are closest and farthest away from Earth. Note that distances are given in kilometers, but to calculate the force in Newtons, meters must be used. The tidal force is the difference ingravitational force exerted on a 1 kilogram mass on the side of Earth closest to the planet and on the side farthest away.

The following standard formulas and definitions were used:

I have found some other sites that deal with this same issue. Phil Plait describes why this alignment is nothing to worry about along with a different way of looking at the numbers. He deals with the absolute gravitational attractions. Brian Monson has some graphics showing the position of the planets on that day as well as some data on fairly recent alignments that didn't cause the end of the world. Frank Reed has graphed the individual and cumulative gravitational influence on Earth from Venus, Mars, Jupiter, and Saturn. It's a very information-rich picture showing that the influence on May 5, 2000 is much smaller than at other times.

There is a web-based orrery that will generate a picture of the planets' locations on any date.

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