Astrology vs Astronomy

Astrology vs Astronomy

Astrology vs Astronomy
Image Credits: Astronomy Lovers

Although astrology and astronomy are two very different fields of study, they are often confused due to similar names. It’s not surprising at all because these two concepts were inseparable, only a few short centuries ago.

Cultures across the world have always been fascinated by the stars and their patterns. Humanity has always wondered why the vast majority of them march in step with each other. Likewise, the individualistic streaks of some stars have been equally intriguing. This curiosity urged us to develop a field of study that could track their positions and figure out their significance.

In the past, the movement of stars was affiliated with certain supernatural effects. This gave birth to the field of astrology. Over time, the paradigm has shifted because the students of astronomy no longer attribute supernatural incidents to stars. Therefore, astrology and astronomy have become as far divorced from each other as is possible. But the similar-sounding names are there to stay, and now we’ve got astrophysics and cosmology too, to further muddy the waters.

Differences Between Astrology and Astronomy

Differences Between Astronomy and Astrology

Astrology and astronomy both study celestial objects, but they differ in their end-goals. Astronomy is concerned with tracking the motions and positions of the heavenly bodies and investigating their composition. On the other hand, astrology is about predicting the effects of the motions and positions of the heavenly bodies on people’s lives.

Astronomy is still enjoying the status of hard science, but the popularity of astrology has decreased immensely. According to Sky and Telescope, astrology has been regarded as a pseudoscience since the 1600s. This blow to its stature was brought about by Isaac Newton. He demonstrated that the same force that makes objects fall is responsible for the motion of celestial objects.

His findings demystified the motion of the heavenly bodies and created doubt about their supernatural effects on people. Additionally, the failure of astrologers to develop a scientific method to test their predictions was also harmful to astrology. On the other hand, astronomers were successful in establishing proper techniques to test their hypothesis. As a result, astrology was relegated from the world of sciences into the realm of mysticism.

Astrophysics vs Astronomy

Astrophysics determines the nature of celestial objects by using the principles of physics and chemistry. Astronomy gives us an overview of the composition of a heavenly body and deals more with its movement.

Astrophysics goes beyond that point and tries to explain how those objects came were formed. Likewise, it covers the evolution of celestial objects over time and predicts their ultimate fate. The topics (like dark matter,  gravitational waves, and background radiation) that are beyond astronomy fall within the domain of astrophysics.

Milestones in the History of Astrophysics

According to Secrets of the Universe, the foundation of astrophysics was first laid in the early 19th century. The discovery that the passage of white light through a prism produces a spectrum can be regarded as the first step.

Later on, it was later found that the phenomenon is caused by certain chemical elements absorbing certain frequencies of light. Since each element has its own unique signature spectrum, astrophysicists can determine the chemical composition of a given celestial object. They do so by analyzing the spectrum of light it produces.

Edward Charles Pickering

In 1885, Edward Charles Pickering (along with his team) categorized 400,000 stars into 7 classifications, based on their spectra. Their system is known as the Harvard Classification Scheme and remains in use to this day. In the 1920s, Arthur Eddington used Einstein’s mass-energy equivalence to demonstrate that stars generate energy by converting hydrogen into helium.

In 1925, Cecilia Payne hypothesized that hydrogen and helium are the major constituents of stars; that was later proved true. Moving forward, Karl Jansky found that certain celestial objects emit radio waves, in 1932. After a wait of almost 40 years, one such object was positively identified in close proximity to Cygnus X-1.

Cosmology vs Astronomy

Cosmology vs Astronomy

The primary difference between astronomy and cosmology is their way of observing the universe. Astronomy focuses on studying individual celestial objects while cosmology studies the universe as a whole. For instance, astronomers observed that various galaxies appear to be traveling outwards from a central location. Based on these observations, cosmologists theorized that the whole universe was created in one Big Bang and is continually expanding.

Cosmologists investigate the evolution of the entire universe and make educated guesses regarding its age and ultimate fate. Whether it will keep expanding forever or eventually burst like an over-inflated balloon. Alternatively, it can also stop expanding and shrink back into the nothingness that birthed it. The question of whether there is only one universe or an entire multiverse is also of interest to cosmologists.

Differentiation Astronomy

Differentiation Astronomy

Many people believe that astronomy is limited to studying the motions and positions of the heavenly bodies. However, that’s NOT true because it can also inform us about the composition of these celestial objects. One way in which astronomy can do this is by looking for differentiation.

Differentiation is a process by which the constituent elements and compounds of an impure substance separate to form distinct layers. The heaviest materials sink and the lighter ones rise to the surface. This phenomenon may be observed if one attempts to mix oil and water. This same process occurs in some celestial objects and evidence for it can be spotted with telescopes.

How were Celestial Objects Differentiated?

In the early stages of solar system development, debris slammed together and accreted into larger masses. During this process, its kinetic energy converted into thermal energy and the entire mass melted. Heavier compounds sank to the core whereas lighter ones rose to the surface under the effect of the object’s gravity. This allowed the heavenly body to become differentiated.

Evidence for differentiation can be spotted with telescopes due to the differences in reflectiveness between lighter and heavier compounds. The degree of differentiation of a given object can be determined by noting the incidence and expanse of light and dark areas on its surface.

If an object is differentiated, we know that it will have a layered structure. Likewise, it would’ve had a certain amount of mass to produce the gravitational effects required for differentiation to occur.


Astronomy has retained and certainly improved its stature as hard science in the last few centuries. On the other hand, astrology lost its place because it couldn’t back its predictions with scientific evidence. The popularity of the idea that the movement and positions of heavenly bodies affect people’s lives decreased immensely. Therefore, the term ‘pseudoscience’ was associated with astrology in the 1600s. 

Frequently Asked Questions (FAQs)

Q. What is the Zodiac?

A. The section of sky in which the Sun appears to be changes over the course of the year. This isn’t because the Sun itself is moving, rather it is due to the Earth’s movement around the Sun.

When the Earth moves forward in its orbit, different collections of stars are hidden from view. This is because our line of sight is obstructed by the Sun. This gives us twelve collections (constellations) that the Sun cycles through over the year. These are the constellations of the Zodiac.

Q. Isn’t there a 13th Zodiacal Constellation?

A. YES, there is a 13th constellation (Ophiuchus or “the Serpent Bearer”) that can be viewed in the sky. Some people claim that this constellation recently became visible due to the Earth’s wobbling about its axis. However, the fact is that Ophiuchus was positioned along the Sun’s path even when Ptolemy formalized his astrological system. He deliberately chose to ignore it and kept the number of constellations of the Zodiac to 12.

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