Astrology is false.
Astrology: what it is and what does it claim?
Astrology is the belief that the position of the Sun, Moon and planets in the ecliptic during birth of a person influences via a mysterious force the character of a person, and can determine his future.
Astrology claims that there are 12 signs in the ecliptic or zodiac, and that the Sun, Moon and planets spends one month in each sign. The 12 signs and their dates, according to astrology, are as follows:
ARIES 20 March - 20 April
TAURUS 20 April - 21 May
GEMINI 21 May - 21 June
CANCER 21 June - 22 July
LEO 22 July - 23 August
VIRGO 23 August - 23 September
LIBRA 23 September - 23 October
SCORPIO 23 October - 22 November
SAGITTARIUS 22 November - 22 December
CAPRICORN 22 December - 20 January
AQUARIUS 20 January - 18 February
PISCES 18 February - 20 March
The Mysterious Force that governs our lives, according to astrology.
But what is this mysterious force that emanates from the stars and planets? From the Moon and the Sun? That has so much influence in our lives? If we listen to astrologers, we are looking at a force that is not influenced by distance or mass.
There are four fundamental forces in the universe: the weak interaction, the strong interaction, electromagnetism and gravity. We can discount the strong and weak interactions as they have no bearing in massive bodies, those forces are responsible for reactions and effects within the atoms, like decay and nuclear fission. We are left with two forces, gravity and electromagnetism.
Let's take a first look at electromagnetism. Immediately, we ran into the first problem: the planets are electrically neutral! There is no electricity coming from Mars or from Jupiter. And even if there was, the effect of electricity diminishes with distance. How about magnetic fields? The Sun's magnetic field is huge, and does influence the Solar System. However, not every planet has a magnetic field of the same strength, and again, the influence of magnetic fields diminish with distance.
We have eliminated electromagnetism.
How about the last force, gravity? Again, we ran into a major problem: gravity depends on mass and distance. the more massive an object is, the more gravity but the gravitational attraction is less and less the further away we are from the object. So, Mars does not exert the same gravitational influence as Jupiter does, and of course, the Sun is the most massive object in the Solar System.
Maybe there is another mysterious force out there, that influences our lives the way astrologers claim. If that were so, then scientists, especially astronomers, would have some evidence for this force. There would be some repeatable patterns, during births, or during major events, there would be something that scientists, actual scientists, would be able to measure. Even astrologers do not know what this mysterious force is!
The Constellations of the Ecliptic: 12 or 13?
Astrology is basing themselves into dividing the ecliptic into 12 equal parts. According to them, the apparent motions of the Sun and the major planets take equal times to traverse each sign.
First of all, there are 13 constellations in the ecliptic. There is also the constellation of Ophiucus. Have you ever known anyone whose star sign is Ophiucus? Let's look at the 13 constellations of the ecliptic, or more commonly known the Zodiac, and the actual times when the Sun is seen in that constellation:
ARIES 19 April - 14 May
TAURUS 14 May - 21 June
GEMINI 21 June - 21 July
CANCER 21 July - 11 August
LEO 11 August - 17 September
VIRGO 17 September - 31 October
LIBRA 31 October - 21 November
SCORPIO 21 November - 30 November
OPHIUCUS 30 November - 18 December
SAGITTARIUS 18 December - 21 January
CAPRICORN 21 January - 17 February
AQUARIUS 17 February - 13 March
PISCES 13 March - 20 April
Let's compare the two tables. What is the first thing that we notice? That the Sun does not move through each constellation in approximately a month as astrologers claim, but that the times the Sun needs to traverse each one, vary from 8 days to more than 40 days! And of course, there is a shift of at least one sign to where the Sun is compared with the astrological table.
This diversity is mainly due to a natural phenomenon called precession of the equinoxes. This phenomenon is due to the motion of the rotational axis of the Earth. Because of gravitational influences, the axis traces a cone every 26000 years. The astrological tables as astrologers now use them, were compiled about 2500 years ago, in Babylonia. During that time, the axis has rotated by about 36 degrees, so its orientation has changed, and as a consequence, so have the apparent motions of the Sun and the other planets in the ecliptic.
The above shows that every calculation that astrologers make is simply wrong, because they have not taken into account actual natural phenomena, like the precession of the equinoxes, nor the fact that each sign does not occupy an equal area in the ecliptic.
Some interesting facts about the Solar System, stars, constellations and more, that astrology fails to consider.
Let's get back to the Solar System. Astrology does include the 9 planets in their predictions... 9 planets? But the current planets of the Solar System are 8! Pluto is officially a dwarf planet like so many other Trans-Neptunian objects. There are a number of dwarf planets that have been discovered like Sedna and Eris. How about the asteroids between Jupiter and Mars? Shouldn't they exert an influence? How about some of the more massive moons of Jupiter like Europa? Or Saturn's moon Titan? How about Pluto's moon Charon? The comets? The objects in the Oort Cloud? But, no, astrology does not recognize those. Only the 9... err 8 planets and one dwarf planet, plus the Sun and the Moon.
What about before the discovery of Uranus, Neptune and Pluto? What did astrologers do, before the discovery of those objects? Didn't they notice that something was wrong with their calculations and natal charts? No, they did not. And that is more evidence that astrology is false. Uranus, Neptune and Pluto were discovered exactly because of their gravitational influences on the other planets. Minor gravitational wobbles allowed astronomers to calculate that there were more planets in the Solar System, to infer their positions and their mass as well.
Now, let's look at the night sky and the constellations. Imagine those constellations in 10.000 years from now (ten thousand). What do you see? If you are an astrologer, you see the exact same constellations in the exact same positions as today. If you are an astronomer, you cannot visualize the constellations.
The Sun and the stars in our galaxy orbit around the galactic centre. That means that even 2500 years ago the stars were not in the exact same positions as they are today, but have shifted, due to those motions. We cannot perceive this in our lifetimes because of the enormous distances and small velocity that both the Sun and the other stars have. The Sun needs about 225-250 thousand years to make a full orbit around the galactic centre.
Just look at Barnard's star which is a star that moves quite fast, and its movement can be seen from year to year:
Stars also have a limited lifespan. It is huge compared to a human's life, but as everything else they die. Some in huge explosions known as supernovae, some more quietly.
And so, constellations change in the night sky. Not as fast as a human's life, but slowly through the ages. Enough though, that since the time of Babylonians to today, there are perceptible changes in the night sky.
There is no force to account for the mysterious force of astrology. The Sun does not spend the same amount of time in each constellation. There are more objects in the Solar System than astrologers can and do "calculate" for. Astrology forgets the precession of the equinoxes, the actual motion of the Sun and the stars, that contribute to the constellations changing shape.
The conclusion is the same as the abstract: astrology is false.
- Plait, Phil (2002) Bad Astronomy (Chapter 21: Mars is in the Seventh House, but Venus Has Left the Building: Why Astrology Doesn't Work. pp 212-220) Wiley.
- Sagan, Carl (1996) The Demon Haunted World: Science as a Candle in the Dark (Chapter 17: The Marriage of Skepticism and Wonder, pp 302-304) Ballantine Books, New York