Astrology vs. Astronomy: What's the Difference?

Astronomy and Astrology have a common history but are widely different fields today.
Christopher McFadden
astronomy versus astrologyNick Normal/Flickr

Astrology and Astronomy might sound very similar, but their differences are as distinct as chalk and cheese. One is a widely respected and studied field of science, whilst the other is widely considered the realm of superstition and fantasy.


But the two have a common history and were only fairly recently defined as separate disciplines. 

In the following article, we'll take a quick look at the similarities and differences between the two and explore their common ancestry. 

Why is astronomy a science and astrology not?

First of all, let's start with some definitions of the two. 

Astronomy is widely defined as: -

"The branch of science which deals with celestial objects, space, and the physical universe as a whole." - Oxford English Dictionary.

Astronomy is, in effect, the scientific study of everything on the larger astrological scale. 

Astrology, on the other hand, is widely defined as: -

"The study of the movements and relative positions of celestial bodies interpreted as having an influence on human affairs and the natural world." - Oxford English Dictionary.

Astrology can be thought of as the predecessor to true astronomy, but with more emphasis on heavenly bodies' influence on humans affairs and predicting future events. It was widely practiced by many ancient cultures and was of incalculable importance to the development of human reasoning and philosophy. 

astronomy versus astrology sky
Source: NASA

Notable amongst them were the ancient Egyptian and Babylonian civilizations. But it is very likely that forms of astrology have very deep roots indeed in human existence. 

Once upon a time, both fields were actually one and of the same thing. This all changed during the "Age of Reason" when astrology was rejected en masse as mere superstition. 

Astrology and astronomy were, more or less, united as a discipline right up to the 17th Century. Prior to this, especially during the late medieval period, astronomy was treated as the foundation upon which astrology operated. 

It wasn't until the 18th Century that the two fields started to become regarded as completely separate disciplines. 

It is for this reason that astronomy is, today, widely considered a true science whilst astrology has been relegated to the status of a form of divination and superstition, and a pseudoscience at best. 

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Whilst this distinction seems obvious to us today, it is important to understand astrology's importance in the story of mankind. Belief in such things pushed humanity forward to observe and contemplate the world outside of day to day mundane existence. 

It is, in a sense, one of the cornerstones of the development of human ingenuity. philosophy and cultural development. Whilst its utility as a means of prediction is long past its sell-by date, it should be cherished like an old family heirloom.

What is the difference between astronomy, astrology, and cosmology?

We have already explored the difference between astronomy and astrology, but what about cosmology?

Cosmology is widely defined as: -

"The science of the origin and development of the universe. Modern cosmology is dominated by the Big Bang theory, which brings together observational astronomy and particle physics." - Oxford English dictionary

astronomy versus astrology galaxy
Source: ESO/L. Calcada/WikimediaCommons

It is, in this sense, a subdiscipline of astronomy but a well defined and large one at that. 

Cosmology has gained a lot of impetus since the 20th Century and has led to some of the most fascinating insights into the universe at large. 

Prominent scientists the likes of Stephen Hawking, a beloved and missed British cosmologist, have pushed human understanding to its breaking point. But even his incredible work is not even the tip of the iceberg with regards to understanding the universe at large

Do astronomers believe in astrology?

To answer this effectively it is again necessary to define what is meant by belief.

To most, the common definition of belief is: -

"belief (in something/somebody) a strong feeling that something or someone exists or is true; confidence that something or someone is good or right" and/or;

"belief (that…) an opinion about something; something that you think is true" - Oxford English Dictionary

astronomy versus astrology giza
Many ancient civilizations were obsessed with the study of the 'heavens'. This has inspired the creation of some of the greatest works of art and architecture man has ever created. Source: George Sandys - 1610 Source: Wikimedia Commons

Whilst belief is usually associated with the realm of Religion, it can be argued that it is also true for scientists. Whilst practitioners of the former tend to use personal experience to justify a belief, the latter use data, peer review, and the scientific method to justify their 'beliefs'. 

But, the great utility of science is that it is able to adapt its 'beliefs' over time as new data emerge and techniques/tools to capture it. This leads to older, long-held to be true theories, and concepts to be completely abandoned in favor of better explanations for natural phenomena.  

In fact, Scientific study is littered with examples of completely wrong theories, like the "Aether" for example. 

And so, as we have seen, astronomy and astrology have some overlap and common shared history. In the sense that both disciplines observe and study the motion of celestial bodies, it can be said that it is true that astronomers 'believe' in astrology. 

But that is as far as the similarity ends. The vast, vast majority of astronomers, hands-down, reject the rest of astrology as having any real credibility. 

At least for now...

Is astrology a branch of astronomy?

Since astronomy is "the branch of science which deals with celestial objects, space and the physical universe as a whole", the simple answer is no. But as we have seen, the two disciplines share a common ancestry and some aspects of each do overlap. 

Both astronomy and astrology were once united in a single discipline whose history is probably as old as human civilization. Many ancient societies were completely obsessed with the motion of planets and other celestial bodies and it can be argued little has changed today.

Ancient Egypt and Babylon are notable examples of civilizations that placed a heavy emphasis on the study of the night's sky. But all civilizations throughout history have been completely enthralled in one sense or another about the 'heavens'. 

Today they are widely considered to be two completely separate fields altogether. Astronomy is the scientific study of the universe and everything in it, whilst astrology is a more esoteric, superstitious and generally pseudo-scientific practice. 

Today astrology is still widely practiced with forecasts about the future in the form of 'Star Sign' sections which are a common feature of many magazines and newspapers. Whilst many believe the veracity of such 'readings' many considers them pure superstition. 

In fact, the Barnum Effect, or Forer Effect, might explain why so many people take them seriously at all. 

To labor the point, the difference between them is very clear.

The former tends to look at the universe critically, whilst the latter tends to use observations of the universe as a means of divination of future events. They are, in no way, directly related to each other today.

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