Q: How much of a direct effect do planets and stars have on us? Is astrology reasonable or plausable?

Physicist: Of the four forces: gravity, electromagnetism, nuclear-strong, and nuclear-weak, only the first two, gravity and EM, affect things over distances (at least, over distances larger than an atomic nucleus).  So, if the planets and stars have any direct influence on us it should be by way of one or both of those forces.

Clearly, it’s a good time to be a Leo.  Sucks for you, Aquarius.

The Moon’s gravity famously causes the tides, but the Moon’s electric field is effectively zero (but very interestingly, not exactly zero), and its magnetic field is random, scattered, and nearly non-existent.

The effect of gravity is much, much stronger than the effect of magnetic fields, and even the effect of gravity between planets is tiny. The bulk of those tiny forces is off-set by the fact that the Earth is free to move and fall through space (during free-fall is the only time you don’t feel gravity). This leaves only the much weaker secondary “tidal effects“, so called because they’re responsible for the tides which, although seemingly impressive, require very little force (specifically, the difference in the strength of the Earth’s gravity over the half-dozen feet of the tides).

The Moon’s gravity causes tides, but effectively nothing else. The Sun’s gravity has about 40% of the Moon’s influence and Jupiter, which completely dwarfs the effects of all of the other planets combined, has about 1 two-hundred-thousandth of the Moon’s tidal effect.

More than that, the gravity and electromagnetic influence of planets isn’t terribly surgical. Either will just pull on you in a very uniform way. They don’t grab a few cells at a time and re-write you love life or change your mood. Probably. Point is, our understanding of the known forces of the universe preclude the idea of the planets and stars having any direct influence on people.

Now to be fair, not being able to fit something into the current model doesn’t immediately exclude it from the realm of possibility.  For example, way back in the day the science fluid dynamics was really good at explaining how things like air and water move, but also “proved” that nothing should be able to fly.  Another beautiful example was a conundrum faced by geologists around 1900.  They had buckets of evidence that the Earth was at least hundreds of millions of years old (the ones who turned out to be right thought that the Earth was substantially older), and yet a back-of-the-envelope calculation showed that during that time the interior of the Earth should have cooled so much that volcanoes and other geothermal nonsense should be absolutely impossible.

But of course a quick look around shows a world full of birds and volcanoes.  So if there’s something around (birds and volcanoes), it really makes no difference what the prevailing scientific theory says one way or the other. Because reality wins.  It’s even written into the science charter, line one: “reality wins”.
By the way, the “flying issue” was later solved by taking into account rotational flows and viscosity, and the “warm Earth problem” is resolved by taking into account radioactive decay (which hadn’t been discovered yet).

So the better question isn’t “can so-called ‘science’ explain astrological effects?” but instead “are there astrological effects?”. There has been a lot of research into astrological phenomena, but so far all of the results have been negative or unrepeatable (science talk for “this isn’t a thing”).  Since the 18th or 19th century the scientific community has pretty much stopped looking, but they were at it for a very long time. There aren’t many scientific papers that seriously investigate this sort of thing, partly because the results are well-known, and partly because the experiments involved are easy enough that they tend to show up in middle-school science fairs relatively often (this is also why there are no articles in Nature about baking soda and vinegar volcanoes).

For example, just take all of the astrological predictions out of a newspaper (pardon: website) and read them in a random order to someone else (this is called a “blind experiment”) and see which one is closest to being accurate. You’ll find that the “correct one” is selected about once out of every 12 trials.

Long story short; whatever affect other planets and stars may have on us individually is completely drowned out by local “noise” (like the gravity and EM field of a passing truck), and worse there doesn’t seem to be an effect that needs explaining.

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8 Responses to Q: How much of a direct effect do planets and stars have on us? Is astrology reasonable or plausable?

  1. One interesting aspect (for me) of what passes for Astrology nowadays is that, most of the time, it seems astrologers follow a very mechanical process: take a few numbers as input, cross reference some tables, provide some lines of text as output, done. And when it comes to newspaper astrological columns then, many times it seems not even that much work went into it, as the text has all appearances of having been random generated. So, yep, it appears even them have mostly given up.

    That said, I’d like to provide some point on what I see as a flawed take on the subject. You see, my formation is as a Philosopher, and when studying Classic, Medieval and Renascence philosophies, there’s no working around the need to obtain at least some theoretical understanding of Astrology, as those older thinkers used to take it into account or at least talk about it. And in so doing, one of the most interesting realizations at which one arrives is that the actual theoretical basis for Astrology had almost nothing to do with Physics. In fact, Physics entered the picture (and the discussion) more or less at the time it began showing its many awesome results, circa 17th century or so. Before that, however, nope, it’s nowhere to be seen. Furthermore, due to Physics not being part of it, it also wasn’t thought that the planets influenced people directly, and much less that such direct influence happened by way of some kind of energy field, force or the like, concepts that simply didn’t exist back then.

    So, what did Astrology (and astrologers) actually believe? In something called “analogy” (not to be confused with the literary concept). The notion was more or less this: given that the universe and you form a single whole, it comes that “you” equals “universe minus everything that isn’t you”, or, put another way, that there’s a correlation between whatever happens with you and whatever happens to everything else. So, if you could find a regularity “out there”, that would correspond to a regularity “in here”. And what are the only absolute regularities we find in a world otherwise completely random? The planetary movements. Thus, by studying the planetary movements then correlating the “analogous” internal movements they revealed with a person’s specific, individual characteristics, you’d be able to get some insights on her past and current standing, as well as on where she was going. It should be noted, in addition, that this study of a person’s individuality should be made in person, not by merely figuring where and when she was born, because any number of life facts, up to and including what you did in the morning, influenced how you were to interpreted the analogy. Furthermore, the kind of question Astrology was supposed to answer was quite concrete, on the level of “help me find my lost keys”, and the astrologer answering, after hearing the person’s problem and doing a few calculations, “hmm… this indicates it should be near something very humid – have you looked throughout your bathroom, or perhaps in your garden?”.

    IMHO, given that one’s forced to draw two conclusions:

    First, that astrologers of old would neither do nor think valid newspaper columns, as those most definitely aren’t individualized. They’d wholeheartedly agree that there’s too much noise for those to be valid, although not in terms of the physics of the thing, but on the huge amount of everything that happened to everyone everywhere since they’ve been born, rendering any such generalization null and void.

    Second, that even if astrology has merit (I’m agnostic on this), it’s hardly something that could be double blinded. At least, I cannot imagine how one would go about developing a test to deal with such a high level of non-mechanicity.

    In any case, for anyone studying historical aspects of anything before the Enlightenment, it’s a subject worth knowing about at least a little, as grasping its central concepts makes understanding the Middle Ages and earlier periods just that much easier. :)

  2. LarryD says:

    Actually, the quick answer is ‘yes, the Moon, Stars, the Sun etc’ do have an effect on us the point is the Interpretation that one gives.
    Take for example, two compatible people are sitting on a bench looking up the ‘wonderful’ starry sky. They look at each other and slowly their heads move toward each other. Well, it sure ‘ain’t’ the gravitaional pull of their heads that is doing the moving! Now, put the same two people on the same night on a bench on a busy sidewalk…would the same thing happen? I doubt it.
    Another example goes back to the Roman Emperor Constantine. He laid the foundations for Modern Day Christianity in the West yet this was all based on a falling object (maybe a meteorite) and HOW the Christian scribes, travelling with his army, persuaded the emperor to interpret the event.
    We have a ‘biological clock’ that works fine when undisturbed but taking a holiday in another country requires a little time for adjustment. Other things can affect this too, happiness, fear, worry and so on but ancients put special interpretations on those feelings when they occurred at certain times, Full Moon etc.
    As for a personal view, I am a Sagittarian (part man, part four legged animal, archer) and some of my traits are those suggested by astrology but others differ very much. Having said that, according to Buddhist I was born on the day relating to a horse and in the year of the horse and need to be free. My wife certainly didn’t like that interpretation…but we’re still married!

  3. Paul Czerner says:

    Until we can mathematically quantify emotions, will, and personality, we would have no way to measure and confirm or deny such celestial effects on living beings.

  4. Xerenarcy says:

    mmm no. have to agree with the article.

    as far as i am aware astrology (as opposed to numerology) relies on the position of celestial bodies at the time of your birth to establish links between said bodies and how they will influence you when they change positions as you age. that is objectively ludicrous to a physicist.

    humoring the notion, however, in a sense yes what you see in the sky can influence your decisions. but this is not a situation exclusive to astrology, but rather superstition in general – that things / events you observe with no conceivable proof of influence on you, will somehow influence your fortune (or others’) regardless because of the event itself is being brought to your (or someone’s) attention.

    to make my point clear, not all the planets, and their orbits, were known when astrology was formed (and re-invented many times in many cultures since). therefore if this was a physical effect, it would have seemed incomplete or inconsistent (relative to today’s astrology) until all the nearby celestial bodies were identified and studied.

    however, if the symbolical significance of the planet is what causes influence attributed to astrology, then it is back to superstition and culture that influences how we interpret what we see, that causes us to make conclusions which may or may not be consistent or correct. arguably because celestial bodies vary in composition, distance, time dilation and the solar system being a dynamic, evolving system in itself, there is no conceivable way it would have a varying effect on individual people that is consistent through the ages.


    try making waves on a beach or shining a laser / torch into the water; any beach leading to the oceans will do… try to influence one specific fish in the ocean somewhere with your actions, creature, anything. that is basically the scale of influence the article argues against being significant enough to be noticeable. under the circumstances to claim success would be textbook attribution bias.

  5. aaron says:

    Not looking for an astrological connection myself, I would have to say that in terms of celestial bodies having an influence on us I would have to point out that the tidal forces caused by the Moon’s (albeit weak) gravity have been cited as having been fundamental in the formation of early life in the Earth’s seas, and Jupiter’s gravity has meant that we have avoided much bombardment by meteors etc that could have had a devastating impact upon Earthlife (although a few may slip through the net – e.g. the K-T event).

  6. vernon vouga says:

    what about the direct connection between planet alignment and effects on broadcast electromagnetic waves?
    planets, at 0, 90, and 180 degrees of alignment to the plane of the solar system regularly affect broadcast signals… why?

  7. vernon vouga says:

    i also want to point out that we are walking talking examples of electromagnetic theory (not to mention quantum) to presume that the ancients had no idea what they were talking about, when they had calendars as well developed if not more developed than our own… is foolhardy and un-inquisitive, and un scientific. you look at all information, not just the bits that fit into a worldview you are comfortable contemplating.

  8. trin says:

    It’s solar radiation that affects the earth and each living thing on it, not the gravity of the sun – the entire approach of planetary gravity as proof against astrology is flawed. Now, obviously solar radiation extends as far as it is capable of doing without being impeded, the sun is a the center of our system and thus emits radiation in all directions which reaches and surrounds every planet, bounces around and becomes colored with some other energy in this way.

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