It's Professor Dave. I'm a cancer. What about you? After getting through all of the astronomy concepts in this series, we've found how

it's quite easy to put certain common beliefs into perspective, like our analysis of the flat-earth model that we just went over.

Are there any other concepts like this that ought to be investigated? I can think of one more.

A significant percentage of the global population believes in astrology, which is the notion that the positions of the planets and stars in the night sky have influence over events

that take place on Earth. According to Western astrology, the locations of the planets along the ecliptic and their

spatial relationship to the twelve constellations of the zodiac is not arbitrary, as science

would suggest. Their positions at your birth determine aspects of your personality, and their positions on any given day determine things that will happen to you.

Can this be true? Can the validity of this claim be tested? It absolutely can. Let's go through an examination of astrology now, and see if we can straighten this out

once and for all. This analysis will occur in two parts. Later, we will look at what's in charts and horoscopes, but first, let's see if

we can find a mechanism of action. Astrologers claim that the positions of celestial objects affect us.

If so, then how? Thousands of years ago, when these planets were regarded as gods, it may have sufficed

to simply say magic, or divine action, and then go about your day. But in the modern era, we have science.

We have instrumentation. We have the ability to learn all about the universe, so if there is something happening

here, we should be able to detect it, measure it, categorize it. So what kind of influence is being exerted by these planets and stars on the Earth and

the people on it? Well, let's see. There are four fundamental forces: the strong and weak nuclear forces, electromagnetism,

and gravity. The nuclear forces operate on the dimensions of an atomic nucleus, so those are out for sure.

Electromagnetism and gravity, on the other hand, have no limit in terms of distance,

so let's take a closer look at those. Keep in mind, we understand these two forces very well.

We have equations that allow us to calculate the magnitude of the electromagnetic force or gravitational force between two objects.

These equations are indisputable; they predict the behavior of objects down to extreme levels of precision, and with repeated, flawless accuracy.

These equations describe the universe. Now, if we try to plug in some numbers, like the masses of celestial objects and the distances

to them, we find that all the stars we see in the night sky are so incredibly far away,

that they just can't affect us. Even the nearby planets in our solar system have a very limited effect.

The abnormally powerful magnetic field of Jupiter has dramatically less influence on human beings than that of a toaster oven in the next room.

The gravity of these faraway objects pulls on us less than the car in your driveway. And not just by a little.

By several orders of magnitude. So, if either of these forces are proposed to be the mechanism by which astrology operates,

then case closed, it's bogus. The math doesn't lie. But that's not the only problem.

Even if the magnitude of these forces was significant enough to affect us, as is certainly true of the gravity exerted by the sun and the moon, and to a much lesser extent, Jupiter

and Saturn, due to their size and proximity, how can gravity dictate your personality at birth? How can gravity, the force of attraction between all matter, determine something as subtle

as your disposition? In the biology series, we learned about genetics and gene expression, so how can astrology

Fit with all of that? The answer is simple. It can't. Astrology predates biology.

It predates all of modern science by a long shot. And that's the point. Astrology is a collection of things that we thought of before we knew anything, in a time

when we thought the Earth was the center of the universe. But the retrograde motion of a planet is not a deity turning around in the sky.

It's just the visual effect of one planet passing another in their respective orbits. The signs of the zodiac don't actually mean anything.

They are just imaginary pictures we made up by playing connect the dots with stars that are strewn about at random.

We made water constellations to remind us about stormy seasons at sea, and Virgo with

her sheaf of grain to remind us of the harvest. These were simple mnemonic devices that had mystical connotations painted upon them by

ancient generations, who were seeking meaning in a universe without any. We have been replacing mysticism and pseudoscience with real science since the time of Galileo,

and astronomy is one such science. Of all the thousands of astronomers around the world, people who study planets and stars

for a living, there are precisely zero that believe in astrology. Just let that sink in for a moment.

Ten out of ten professional space scientists agree, astrology is not a thing. Once you learn enough science, the pseudoscience

Now let's say you're still not convinced. Perhaps you don't know about these equations and you don't trust scientists in the first place.

That's fair; we should be able to make up our own minds, so let's come at this from

a different angle. Let's say astrology is true. Let's say that the planets and stars do influence events on Earth, and we just can't

understand how. It is beyond our ability to comprehend the mechanism of action at this point in time.

If this were the case, astrologers should still be able to make predictions that correlate with reality.

If the positions of celestial objects are indeed relevant, we should be able to conduct experiments and collect evidence demonstrating this relevance.

Well, a wide variety of experiments have been done.

Some experiments have asked professional astrologers to match people to their natal charts based on their psychological profiles.

They never succeed in a statistically significant way, beyond what random chance would allow. If astrology were true, wouldn't people who study it be able to apply its tenets as consistently as scientists apply science?

Well, perhaps they are bad astrologers, one might say. They don't know what they're doing, so that doesn't prove anything.

Very well, then what if we gather huge amounts of data on certain sets of people? Some studies have taken hundreds of people, all born within a couple of minutes of each other,

who are now adults, and examined a wide variety of their characteristics: disposition, income, profession, relationship status, and dozens more.

The planets were in the same positions for the births of all these people, so there should be some similarity between them.

Something, anything. And yet, no trends can be found whatsoever for any of these traits and circumstances.

They are no more alike than any random assortment of people of similar age. Still too many variables, you say?

Unreliable reporting of time of birth, too much distance between the locations of birth… alright, no problem.

Let's get even more specific. Two people born within seconds of one another in the exact same location.

Fraternal twins. According to astrology, these children have precisely identical charts and should therefore

be essentially identical people. Same sky, same planets, same constellations, same location—everything is the same, so

They don't necessarily have the same chart. If you haven’t been convinced of anything yet, then no further study can be cited to

convince you, so use your personal experience. Go ahead and think of all the fraternal twins you have ever known.

Are they identical? All of them? Definitely not. Some are rather similar, and some couldn’t be more different.

Just like all siblings. But astrology would require that these similarities exist, without exception. That fraternal twins do not have precisely identical personalities is definitive proof

that astrology is false. Maybe you’re still not satisfied. Let’s say you don’t have a twin, and never knew any.

How can you verify things for yourself? Well, you have a sun sign, you have a natal chart, and horoscopes that should apply to you.

So what about individual horoscopes then? Studies have been performed whereby test subjects with birthdays scattered throughout the year

are given horoscopes, and are told that they are highly specific to their sign. High percentages of the subjects reported that their reading was very accurate and insightful,

despite the fact that everyone got exactly the same horoscope. How can the same horoscope apply to everyone?

It can’t. That defies what astrology proposes. We should all get different horoscopes and natal charts.

So how can everyone identify with the same one? That’s very easy to answer. Most horoscopes and charts are vague, listing more positive traits than negative ones.

Everyone wants to believe that they are compassionate, creative, intuitive, wise, or other such traits.

Even weaknesses listed are usually pretty easy to swallow, like overly trusting, or too humble, or having high standards for oneself, things that have a positive spin to them.

Most people will agree that they are these things even if they objectively are not. Furthermore, on any given day, look up your horoscope from ten different sources.

If astrology is true, they should all agree to an extent. But you can bet a lot of money that they will not.

Some will tell you to be careful with money; some will tell you to take a chance today.

Nothing said will mean much, and none of it will correlate. Horoscopes are just too vague to have any real meaning, as they do not predict things

as concretely as science does. Science says that if you throw this object at this angle and with this initial velocity,

according to this equation, it will land on this precise spot at this precise time. And lo and behold, it does, every single time.

The equation, therefore, must correlate with reality. Horoscopes do not say anything so falsifiable. If they said that today a man named Kyle Evans will ask you if you want half of his tuna

sandwich, and then a car horn will honk three times before you find a two-dollar bill under

a mailbox, and that highly specific event did indeed happen to every single person for whom that horoscope applies, then astrology would be in business.

But this is never the case. It's always something along the lines of: there will be an important opportunity.

Or, you will reconnect with someone. Or, you will have to make a decision today. These are things that apply to pretty much everyone, every day of their lives, and that's

what makes astrology a pseudoscience. It does not regularly make rigorously falsifiable claims, and when it does, they are immediately

falsified. Anyone being honest with themselves must admit that these results demonstrate that there is no validity to astrology.

When something makes falsifiable claims, which are then repeatedly falsified, that model must be rejected.

If someone asks you to think of a number from one to ten and then attempts to guess it,

claiming that they are psychic, if they then proceed to guess incorrectly many times in a row, we would conclude that they are not psychic.

This is how science works. For a theory to be valid, it must correlate existing data and make predictions.

If those predictions don't work out, the theory is discarded. So the fact that astrology has stuck around is due to confirmation bias, plain and simple.

If a psychic guesses your number only two out of seven times, they are not psychic; they just guessed correctly two times by chance, just like any of us might.

But if someone reads their horoscope every day, and two times this week it correlated vaguely with events, they may still believe in astrology if they use those two days to

confirm their bias and ignore the rest of the data. An equation that only predicts events two out of seven times is utterly useless in science,

as it can't have a reliable correlation with reality. Therefore, neither do horoscopes.

You can demonstrate this to yourself by comparing your experiences with others who have the same sun sign as you.

Try to objectively assess whether there is a correlation. If you're really serious, find someone born on the same day of the same year as you.

Even in the same region. The two of you would absolutely have to be dramatically similar, as the tenets of astrology

would apply to both of you. If the reality is anything less than this, astrology can't be true, because in order

Astrology: Fact or Fiction?

Welcome! I have a knack for explaining stuff and I want to share some knowledge with you.

I received a BA in chemistry from Carleton College, and performed graduate studies in both synthetic organic chemistry and science education at Cal State Northridge, receiving an MA in the latter. Prior to this I taught for about a decade in various high school and undergraduate settings, specializing in organic chemistry but also teaching general chemistry, physics, and biology.

This channel is for students at the high school and undergraduate level, but it is also for members of the general public who just want to know more about the world and how things work. My goal is to increase science literacy in our society, so please share these tutorials with anyone that you think might enjoy them. Happy learning!

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Astrology: Fact or Fiction?

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