What’s That Bright Star in the Sky?

What’s That Bright Star in the Sky?

Every few months a bright star appears in the sky. Sometimes it’s off to the East, bright in the morning before the Sun rises. Other times, you can see it in the West right after the Sun sets.

Experienced stargazers know this isn’t a star at all, of course, it’s Venus. That horrible twin planet, surrounded by a toxic choking atmosphere of superheated carbon dioxide. For a while it becomes the fourth brightest object in the sky: after the Sun, Moon and the International Space Station, if you can believe it.

In dark skies, Venus gets so bright you can even read a book to it.

Inexperienced stargazers, however, suddenly notice this super bright star in the sky. How come they never noticed it before? Was it always right next to the Moon like that? And that’s when the UFO calls to 911 start up.

Credit: nosha (CC BY-SA 2.0)

I know none of them are going to be watching this video. But for everyone else, even mildly interested in the science here, let’s dig into the orbit of Venus, how we finally figured out what that thing is, how you can observe the planet, and some cool tricks Venus can do.

We’ve written several articles on what planet Venus actually is, and why it sucks so much. You know, a runaway greenhouse effect giving the planet 90 times the Earth’s atmospheric pressure at the surface. It’s a 462-degree furnace, anywhere you go, with a rain of sulfuric acid.

A radar view of Venus taken by the Magellan spacecraft, with some gaps filled in by the Pioneer Venus orbiter. Credit: NASA/JPL

Nope, we’re not going to talk about visiting that place. Instead, we’re just going to talk about looking at it from afar, and how it changed our whole understanding about our place in the Solar System.

Venus is, of course, the second planet from the Sun. But for the vast majority of human history, nobody really understood what it was. It’s easy to see in the sky, even if you live in one of the most light polluted cities on Earth.

Ancient civilizations tried to grapple with what they were looking at, and of course, they assumed there was something supernatural going on. Probably dark and vengeful gods wandering through the heavens, staring down at us with their beady eyes. Judging, always judging. Some civilizations figured out that it’s a single object, while others believed they were looking at two separate entities.

The Ancient Greeks, for example, called the morning edition of Venus Phosphoros, the “Bringer of Light”, and they called the evening star Hesperos, the, uh, “Star of the Evening”. Then they realized it was a single object, and upgraded it to Aphrodite, the goddess of love. The Romans turned that into Venus, and the name stuck.

Heliocentric Model
Andreas Cellarius’s illustration of the Copernican system, from the Harmonia Macrocosmica (1708). Credit: Public Domain

The ancient astronomers assumed the Earth was the center of the Universe, and all the planets and even the Sun and stars revolved around us. but Nicholas Copernicus worked out the true nature of the Solar System in the early 16th century. The Sun was at the center of the Solar System, and all planets, including Earth, orbited around it.

It was a cool story, and nicely fit the motions of the planets, however, the best evidence came almost a century later when Galileo turned his first crude telescope to Venus and realized that the planet goes through phases, just like the Moon. In fact, with a small telescope, you can confirm this all for yourself.

Each of the planets orbit the Sun. Mercury and Venus orbit closer to the Sun, then Earth, then the rest of the planets. When we observe Venus, we look inwards, down towards the Sun. When we see the rest of the planets, we’re looking outward, away from the Sun.

The best analogy is a car race. If you’re in the stands watching those cars go around and around, you’re turning your head back and forth as the cars pointlessly circle in front of you. But to see cars in the ring road around the racetrack, you’ll need to look all the way round you. Make sense?

 

The orbits of Earth and Venus around the Sun. Credit: Universe Sandbox ²

Here’s a simplified version of the Solar System, with just the Earth, Venus, and the Sun. Earth, as you probably know, takes just over 365 days to go around the Sun, while Venus only takes 225 days to complete an orbit.

Which means that Venus completes more than 3 orbits every time Earth completes 2. Which means that we’re always seeing Venus from different angles compared to the Sun.

Sometimes it’s on the same side of the Sun as us. Other times it’s on the opposite. And sometimes Venus is on one side of the Sun, or the other. For about 9 and a half months, Venus is the evening star, brightening to its maximum, and then it spends another 9 and a half months as the morning star.

When all three are lined up, astronomers call that a conjunction. It’s a superior conjunction if Venus is on the opposite side of the Sun, and an inferior conjunction if it’s between us and the Sun.

When Venus is on either side, we measure its elongation, eastern or western. Because Venus orbits close to the Sun, the absolute maximum it can get is 47-degrees elongation. Make a triangle, where you point one line at the Sun, and another line at Venus, the angle of this triangle can’t get any bigger than 47-degrees.

And this is why we always see Venus relatively close to the Sun in the sky. There are 360 total degrees you can look, but Venus never leaves 90 of them.

The phases of Venus. Credit: Statis Kalyvas – VT-2004 programme

Now, onto the phases. Just like the Moon, when Venus is in between us and the Sun, then all the light is falling on the far side of Venus. The side facing towards the Sun, but facing away from us. Of course, Venus is also hidden by the glare of the Sun, which means we really can’t even see it. The opposite happens when it’s on the other side of the Sun. It would be fully illuminated from our perspective. Too bad we can’t see it in all that glare.

But when Venus is on either side, this is when we can finally see it. As our perspective changes, we’re seeing more and more of the planet illuminated, and less in shadow. We see phases. We can see a crescent Venus, or a quarter Venus, or a gibbous Venus.

When Venus is almost fully illuminated, it’s actually at its dimmest because it’s so far away. Then as it moves higher and higher in the sky, we see less of it illuminated, but more overall surface area, so it gets brighter. The point of maximum brightness, when it’s blazing brighter than almost any other object in the sky is when the greatest amount of surface area of Venus is visible to us. Astronomers call this the greatest illuminated extent.

Venus is beautiful in the evening right now as I’m recording this video. We won’t see it this bright in the evening sky until August 2017, and then March, 2020. So, get out and enjoy it while you can.

When Venus passes directly in front of the Sun, that’s a planetary transit. The last time it happened was back in 2012, and before that, 2004. Unfortunately, the next transit of Venus won’t happen until 2117. I’m sure I’ll be still around, living it up in my robot body.

You’d might wonder why they don’t line up every time Venus passes between the Earth and the Sun. That’s because both Earth and Venus are slightly tilted in their orbits. Sometimes we see Venus above the Sun when it’s directly across from us, other times it’s below the Sun. It’s only after more than 100 years they directly line up again.

 

A planetary transit of Venus. Credit: NASA/Goddard Space Flight Center/SDO

It turns out that transits of Venus gave us some of the most valuable discoveries in human history.

Today we know that the Sun is approximately 150 million kilometers away. But for the longest time we had no idea how far away the planets are. We know how far away everything is in proportion to everything else, but not in absolute terms.

In 1663, the Scottish mathematician James Gregory calculated that by making very precise measurements of the transits of Venus or Mercury, you could use trigonometry to figure out the actual distance from the Earth to the Sun. The famed astronomer Edumund Halley did even more detailed calculations and suggesedt places on the Earth to make measurements from.

It wasn’t until the 1700s that astronomers got organized enough to make worldwide measurements during a transit of Venus.

Astronomers tried to observe the Venus transit of 1761, but the weather conditions were pretty bad. In the 1769 transit, however, astronomers were sent to various corners of the globe. In Canada, Norway and the South Pacific. Nations fighting each other allowed astronomers safe passage through on ships through the warzone.

All of the observers made 4 observations: when Venus was touching the edge of the Sun, when it was fully inside, when it had touched the other side, and when it was fully out.

By combining all these measurements across the Earth, astronomers calculated that the distance from the Earth to the Sun was 93,726,900 English miles. The most accurate number we have today is 92,955,000 miles, or about 150 million kilometers. They were only off by about 1%. Not bad.

Once we knew the distance from the Earth to the Sun, we could calculate the distance to the other planets, even to other stars.  All thanks to Venus.

Venus is one of the most dependable companions we have in the night sky. Sure, it’s a hellish death world, but from our perspective here on Earth, it’s really cool to look at. Don’t miss the next opportunity to see Venus with your own eyeballs. And if you can, get your hands on a telescope and see the planet going through its phases. You won’t regret it.

Did you get a chance to see the last transit of Venus, back in 2012? Give me the details of your experience in the comments.

What Is The Geocentric Model Of The Universe?

The Geocentric View of the Solar System

During the many thousand years that human beings have been looking up at the stars, our concept of what the Universe looks like has changed dramatically. At one time, the magi and sages of the world believed that the Universe consisted of a flat Earth (or a square one, a zigarrut, etc.) surrounded by the Sun, the Moon, and the stars. Over time, ancient astronomers became aware that some stars did not move like the rest, and began to understand that these too were planets.

In time, we also began to understand that the Earth was indeed round, and came up with rationalized explanations for the behavior of other celestial bodies. And by classical antiquity, scientists had formulated ideas on how the motion of the planets occurred, and how all the heavenly orbs fit together. This gave rise to the Geocentric model of the universe, a now-defunct model that explained how the Sun, Moon, and firmament circled around our planet.

Continue reading “What Is The Geocentric Model Of The Universe?”

What Is The Heliocentric Model Of The Universe?

Heliocentric Model

The Scientific Revolution, which took place in the 16th and 17th centuries, was a time of unprecedented learning and discovery. During this period, the foundations of modern science were laid, thanks to breakthroughs in the fields of physics, mathematics, chemistry, biology, and astronomy. And when it comes to astronomy, the most influential scholar was definitely Nicolaus Copernicus, the man credited with the creation of the Heliocentric model of the Universe.

Based on ongoing observations of the motions of the planets, as well as previous theories from classical antiquity and the Islamic World, Copernicus’ proposed a model of the Universe where the Earth, the planets and the stars all revolved around the Sun. In so doing, he resolved the mathematical problems and inconsistencies arising out of the classic geocentric model and laid the foundations for modern astronomy.

While Copernicus was not the first to propose a model of the Solar System in which the Earth and planets revolved around the Sun, his model of a heliocentric universe was both novel and timely. For one, it came at a time when European astronomers were struggling to resolve the mathematical and observational problems that arose out of the then-accepted Ptolemaic model of the Universe, a geocentric model proposed in the 2nd century CE.

In addition, Copernicus’ model was the first astronomical system that offered a complete and detailed account of how the Universe worked. Not only did his model resolves issues arising out of the Ptolemaic system, it offered a simplified view of the universe that did away with complicated mathematical devices that were needed for the geocentric model to work. And with time, the model gained influential proponents who contributed to it becoming the accepted convention of astronomy.

The Geocentric View of the Solar System
An illustration of the Ptolemaic geocentric system by Portuguese cosmographer and cartographer Bartolomeu Velho, 1568. Credit: Bibliothèque Nationale, Paris

The Ptolemaic (Geocentric) Model:

The geocentric model, in which planet Earth is the center of the Universe and is circled by the Sun and all the planets, had been the accepted cosmological model since ancient times. By late antiquity, this model had come to be formalized by ancient Greek and Roman astronomers, such as Aristotle (384 – 322 BCE) – who’s theories on physics became the basis for the motion of the planets – and Ptolemy (ca. 100 – ca.?170 CE), who proposed the mathematical solutions.

The geocentric model essentially came down to two common observations. First of all, to ancient astronomers, the stars, the Sun, and the planets appeared to revolve around the Earth on daily basis. Second, from the perspective of the Earth-bound observer, the Earth did not appear to move, making it a fixed point in space.

The belief that the Earth was spherical, which became an accepted fact by the 3rd century BCE, was incorporated into this system. As such, by the time of Aristotle, the geocentric model of the universe became one where the Earth, Sun and all the planets were spheres, and where the Sun, planets and stars all moved in perfect circular motions.

However, it was not until Egyptian-Greek astronomer Claudius Ptolemaeus (aka. Ptolemy) released his treatise Almagest in the 2nd century BCE that the details became standardized. Drawing on centuries of astronomical traditions, ranging from Babylonian to modern times, Ptolemy argued that the Earth was in the center of the universe and the stars were all at a modest distance from the center of the universe.

About every two years, however, the Earth passes Mars as they orbit around the Sun. Credit: NASA
The planet Mars, undergoing “retrograde motion” – a phenomena where it appears to be moving backwards in the sky – in late 2009 and early 2010. Credit: NASA

Each planet in this system is also moved by a system of two spheres – a deferent and an epicycle. The deferent is a circle whose center point is removed from the Earth, which was used to account for the differences in the lengths of the seasons. The epicycle is embedded in the deferent sphere, acting as a sort of “wheel within a wheel”. The purpose of he epicycle was to account for retrograde motion, where planets in the sky appear to be slowing down, moving backwards, and then moving forward again.

Unfortunately, these explanations did not account for all the observed behaviors of the planets. Most noticeably, the size of a planet’s retrograde loop (especially Mars) were sometimes smaller, and larger, than expected. To alleviate the problem, Ptolemy developed the equant – a geometrical tool located near the center of a planet’s orbit that causes it to move at a uniform angular speed.

To an observer standing at this point, a planet’s epicycle would always appear to move at uniform speed, whereas it would appear to be moving at non-uniform speed from all other locations.While this system remained the accepted cosmological model within the Roman, Medieval European and Islamic worlds for over a thousand years, it was unwieldy by modern standards.

However, it did manage to predict planetary motions with a fair degree of accuracy, and was used to prepare astrological and astronomical charts for the next 1500 years. By the 16th century, this model was gradually superseded by the heliocentric model of the universe, as espoused by Copernicus, and then Galileo and Kepler.

Picture of George Trebizond's Latin translation of Almagest. Credit: Public Domain.
Picture of George Trebizond’s Latin translation of Almagest. Credit: Public Domain

The Copernican (Heliocentric) Model:

In the 16th century, Nicolaus Copernicus began devising his version of the heliocentric model. Like others before him, Copernicus built on the work of Greek astronomer Atistarchus, as well as paying homage to the Maragha school and several notable philosophers from the Islamic world (see below). By the early 16th century, Copernicus summarized his ideas in a short treatise titled Commentariolus (“Little Commentary”).

By 1514, Copernicus began circulating copies amongst his friends, many of whom were fellow astronomers and scholars. This forty-page manuscript described his ideas about the heliocentric hypothesis, which was based on seven general principles. These principles stated that:

  • Celestial bodies do not all revolve around a single point
  • The center of Earth is the center of the lunar sphere—the orbit of the moon around Earth
  • All the spheres rotate around the Sun, which is near the center of the Universe
  • The distance between Earth and the Sun is an insignificant fraction of the distance from Earth and Sun to the stars, so parallax is not observed in the stars
  • The stars are immovable – their apparent daily motion is caused by the daily rotation of Earth
  • Earth is moved in a sphere around the Sun, causing the apparent annual migration of the Sun. Earth has more than one motion
  • Earth’s orbital motion around the Sun causes the seeming reverse in direction of the motions of the planets

Thereafter he continued gathering data for a more detailed work, and by 1532, he had come close to completing the manuscript of his magnum opus – De revolutionibus orbium coelestium (On the Revolutions of the Heavenly Spheres). In it, he advanced his seven major arguments, but in more detailed form and with detailed computations to back them up.

A comparison of the geocentric and heliocentric models of the universe. Credit: history.ucsb.edu
A comparison of the geocentric and heliocentric models of the universe. Credit: history.ucsb.edu

By placing the orbits of Mercury and Venus between the  Earth and the Sun, Copernicus was able to account for changes in their appearances. In short, when they are on the far side of the Sun, relative to Earth, they appear smaller but full. When they are on the same side of the Sun as the Earth, they appear larger and “horned” (crescent-shaped).

It also explained the retrograde motion of planets like Mars and Jupiter by showing that Earth astronomers do not have a fixed frame of reference but a moving one. This further explained how Mars and Jupiter could appear significantly larger at certain times than at others. In essence, they are significantly closer to Earth when at opposition than when they are at conjunction.

However, due to fears that the publication of his theories would lead to condemnation from the church (as well as, perhaps, worries that his theory presented some scientific flaws) he withheld his research until a year before he died. It was only in 1542, when he was near death, that he sent his treatise to Nuremberg to be published.

Historical Antecedents:

As already noted, Copernicus was not the first to advocate a heliocentric view of the Universe, and his model was based on the work of several previous astronomers. The first recorded examples of this are traced to classical antiquity, when Aristarchus of Samos (ca. 310 – 230 BCE) published writings that contained references which were cited by his contemporaries (such as Archimedes).

Aristarchus's 3rd century BC calculations on the relative sizes of, from left, the Sun, Earth and Moon. Credit: Wikipedia Commons
Aristarchus’s 3rd century BC calculations on the relative sizes of, from left, the Sun, Earth and Moon. Credit: Wikipedia Commons

In his treatise The Sand Reckoner, Archimedes described another work by Aristarchus in which he advanced an alternative hypothesis of the heliocentric model. As he explained:

Now you are aware that ‘universe’ is the name given by most astronomers to the sphere whose center is the center of the earth and whose radius is equal to the straight line between the center of the sun and the center of the earth. This is the common account… as you have heard from astronomers. But Aristarchus of Samos brought out a book consisting of some hypotheses, in which the premises lead to the result that the universe is many times greater than that now so called. His hypotheses are that the fixed stars and the sun remain unmoved, that the earth revolves about the sun in the circumference of a circle, the sun lying in the middle of the orbit, and that the sphere of the fixed stars, situated about the same center as the sun, is so great that the circle in which he supposes the earth to revolve bears such a proportion to the distance of the fixed stars as the center of the sphere bears to its surface.

This gave rise to the notion that there should be an observable parallax with the “fixed stars” (i.e an observed movement of the stars relative to each other as the Earth moved around the Sun). According to Archimedes, Aristarchus claimed that the stars were much farther away than commonly believed, and this was the reason for no discernible parallax.

The only other philosopher from antiquity who’s writings on heliocentrism have survived is Seleucis of Seleucia (ca. 190 – 150 BCE). A Hellenistic astronomer who lived in the Near-Eastern Seleucid empire, Seleucus was a proponent of the heliocentric system of Aristarchus, and is said to have proved the heliocentric theory.

According to contemporary sources, Seleucus may have done this by determining the constants of the geocentric model and applying them to a heliocentric theory, as well as computing planetary positions (possibly using trigonometric methods). Alternatively, his explanation may have involved the phenomenon of tides, which he supposedly theorized to be related to the influence of the Moon and the revolution of the Earth around the Earth-Moon ‘center of mass’.

In the 5th century CE, Roman philosopher Martianus Capella of Carthage expressed an opinion that the planets Venus and Mercury revolved around the Sun, as a way of explaining the discrepancies in their appearances. Capella’s model was discussed in the Early Middle Ages by various anonymous 9th-century commentators, and Copernicus mentions him as an influence on his own work.

During the Late Middle Ages, Bishop Nicole Oresme (ca. 1320-1325 to 1382 CE) discussed the possibility that the Earth rotated on its axis. In his 1440 treatise De Docta Ignorantia (On Learned Ignorance) Cardinal Nicholas of Cusa (1401 – 1464 CE) asked whether there was any reason to assert that the Sun (or any other point) was the center of the universe.

Indian astronomers and cosmologists also hinted at the possibility of a heliocentric universe during late antiquity and the Middle Ages. In 499 CE, Indian astronomer Aaryabhata published his magnum opus Aryabhatiya, in which he proposed a model where the Earth was spinning on its axis and the periods of the planets were given with respect to the Sun. He also accurately calculated the periods of the planets, times of the solar and lunar eclipses, and the motion of the Moon.

Ibn al-Shatir's model for the appearances of Mercury, showing the multiplication of epicycles using the Tusi couple, thus eliminating the Ptolemaic eccentrics and equant. Credit: Wikipedia Commons
Ibn al-Shatir’s model for the appearances of Mercury, showing the multiplication of epicycles using the Tusi couple, thus eliminating the Ptolemaic eccentrics and equant. Credit: Wikipedia Commons

In the 15th century, Nilakantha Somayaji published the Aryabhatiyabhasya, which was a commentary on Aryabhata’s Aryabhatiya. In it, he developed a computational system for a partially heliocentric planetary model, in which the planets orbit the Sun, which in turn orbits the Earth. In the Tantrasangraha (1500), he revised the mathematics of his planetary system further and incorporated the Earth’s rotation on its axis.

Also, the heliocentric model of the universe had proponents in the medieval Islamic world, many of whom would go on to inspire Copernicus. Prior to the 10th century, the Ptolemaic model of the universe was the accepted standard to astronomers in the West and Central Asia. However, in time, manuscripts began to appear that questioned several of its precepts.

For instance, the 10th-century Iranian astronomer Abu Sa’id al-Sijzi contradicted the Ptolemaic model by asserting that the Earth revolved on its axis, thus explaining the apparent diurnal cycle and the rotation of the stars relative to Earth. In the early 11th century, Egyptian-Arab astronomer Alhazen wrote a critique entitled Doubts on Ptolemy (ca. 1028) in which he criticized many aspects of his model.

Entrance to the observatory of Ulug'Beg (now Museum) in Samarkand (Uzbekistan). Credit: WIkipedia Commons/Sigismund von Dobschütz
Entrance to the observatory of Ulug’Beg in Samarkand (Uzbekistan). Credit: Wikipedia Commons/Sigismund von Dobschütz

Around the same time, Iranian philosopher Abu Rayhan Biruni  973 – 1048) discussed the possibility of Earth rotating about its own axis and around the Sun – though he considered this a philosophical issue and not a mathematical one. At the Maragha and the Ulugh Beg (aka. Samarkand) Observatory, the Earth’s rotation was discussed by several generations of astronomers between the 13th and 15th centuries, and many of the arguments and evidence put forward resembled those used by Copernicus.

Impact of the Heliocentric Model:

Despite his fears about his arguments producing scorn and controversy, the publication of Copernicu’s theories resulted in only mild condemnation from religious authorities. Over time, many religious scholars tried to argue against his model. But within a few generation’s time, Copernicus’ theory became more widespread and accepted, and gained many influential defenders in the meantime.

These included Galileo Galilei (1564-1642), who’s investigations of the heavens using the telescope allowed him to resolve what were seen as flaws in the heliocentric model, as well as discovering aspects about the heavens that supported heliocentrism. For example, Galileo discovered moons orbiting Jupiter, Sunspots, and the imperfections on the Moon’s surface – all of which helped to undermine the notion that the planets were perfect orbs, rather than planets similar to Earth. While Galileo’s advocacy of Copernicus’ theories resulted in his house arrest, others soon followed.

German mathematician and astronomer Johannes Kepler (1571-1630) also helped to refine the heliocentric model with his introduction of elliptical orbits. Prior to this, the heliocentric model still made use of circular orbits, which did not explain why planets orbited the Sun at different speeds at different times. By showing how the planet’s sped up while at certain points in their orbits, and slowed down in others, Kepler resolved this.

In addition, Copernicus’ theory about the Earth being capable of motion would go on to inspire a rethinking of the entire field of physics. Whereas previous ideas of motion depended on an outside force to instigate and maintain it (i.e. wind pushing a sail) Copernicus’ theories helped to inspire the concepts of gravity and inertia. These ideas would be articulated by Sir Isaac Newton, who’s Principia formed the basis of modern physics and astronomy.

Although its progress was slow, the heliocentric model eventually replaced the geocentric model. In the end, the impact of its introduction was nothing short of a revolutionary. Henceforth, humanity’s understanding of the universe and our place in it would be forever changed.

We have written many interesting articles on the heliocentric model here at Universe Today. For starters, here’s Galileo Returns to the Vatican and The Earth Goes Around the Sun, Who Was Nicolaus Copernicus? and What is the Difference Between the Geocentric and Heliocentric Models?

For more information on heliocentrism, take a look at these articles from NASA on Copernicus or the center of the galaxy.

Astronomy Cast also has an episode on the subject, titled Episode 77: Where is the Center of the Universe and Episode 302: Planetary Motion in the Sky.

Who Was Nicolaus Copernicus?

When it comes to understanding our place in the universe, few scientists have had more of an impact than Nicolaus Copernicus. The creator of the Copernican Model of the universe (aka. heliocentrism), his discovery that the Earth and other planets revolved the Sun triggered an intellectual revolution that would have far-reaching consequences.

In addition to playing a major part in the Scientific Revolution of the 17th and 18th centuries, his ideas changed the way people looked at the heavens, the planets, and would have a profound influence over men like Johannes Kepler, Galileo Galilei, Sir Isaac Newton and many others. In short, the “Copernican Revolution” helped to usher in the era of modern science.

Copernicus’ Early Life:

Copernicus was born on February 19th, 1473 in the city of Torun (Thorn) in the Crown of the Kingdom of Poland. The youngest of four children to a well-to-do merchant family, Copernicus and his siblings were raised in the Catholic faith and had many strong ties to the Church.

His older brother Andreas would go on to become an Augustinian canon, while his sister, Barbara, became a Benedictine nun and (in her final years) the prioress of a convent. Only his sister Katharina ever married and had children, which Copernicus looked after until the day he died. Copernicus himself never married or had any children of his own.

Nicolaus Copernicus portrait from Town Hall in Torun (Thorn), 1580. Credit: frombork.art.pl
Nicolaus Copernicus portrait from Town Hall in Torun (Thorn), 1580. Credit: frombork.art.pl

Born in a predominately Germanic city and province, Copernicus acquired fluency in both German and Polish at a young age, and would go on to learn Greek and Italian during the course of his education. Given that it was the language of academia in his time, as well as the Catholic Church and the Polish royal court, Copernicus also became fluent in Latin, which the majority of his surviving works are written in.

Copernicus’ Education:

In 1483, Copernicus’ father (whom he was named after) died, whereupon his maternal uncle, Lucas Watzenrode the Younger, began to oversee his education and career. Given the connections he maintained with Poland’s leading intellectual figures, Watzenrode would ensure that Copernicus had  great deal of exposure to some of the intellectual figures of his time.

Although little information on his early childhood is available, Copernicus’ biographers believe that his uncle sent him to St. John’ School in Torun, where he himself had been a master. Later, it is believed that he attended the Cathedral School at Wloclawek (located 60 km south-east Torun on the Vistula River), which prepared pupils for entrance to the University of Krakow – Watzenrode’s own Alma mater.

In 1491, Copernicus began his studies in the Department of Arts at the University of Krakow. However, he quickly became fascinated by astronomy, thanks to his exposure to many contemporary philosophers who taught or were associated with the Krakow School of Mathematics and Astrology, which was in its heyday at the time.

A comparison of the geocentric and heliocentric models of the universe. Credit: history.ucsb.edu
A comparison of the geocentric and heliocentric models of the universe. Credit: history.ucsb.edu

Copernicus’ studies provided him with a thorough grounding in mathematical-astronomical knowledge, as well as the philosophy and natural-science writings of Aristotle, Euclid, and various humanist writers. It was while at Krakow that Copernicus began collecting a large library on astronomy, and where he began his analysis of the logical contradictions in the two most popular systems of astronomy.

These models – Aristotle’s theory of homocentric spheres, and Ptolemy’s mechanism of eccentrics and epicycles – were both geocentric in nature. Consistent with classical astronomy and physics, they espoused that the Earth was at the center of the universe, and that the Sun, the Moon, the other planets, and the stars all revolved around it.

Before earning a degree, Copernicus left Krakow (ca. 1495) to travel to the court of his uncle Watzenrode in Warmia, a province in northern Poland. Having been elevated to the position of Prince-Bishop of Warmia in 1489, his uncle sought to place Copernicus in the Warmia canonry. However, Copernicus’ installation was delayed, which prompted his uncle to send him and his brother to study in Italy to further their ecclesiastic careers.

In 1497, Copernicus arrived in Bologna and began studying at the Bologna University of Jurists’. While there, he studied canon law, but devoted himself primarily to the study of the humanities and astronomy. It was also while at Bologna that he met the famous astronomer Domenico Maria Novara da Ferrara and became his disciple and assistant.

The Geocentric View of the Solar System
An illustration of the Ptolemaic geocentric system by Portuguese cosmographer and cartographer Bartolomeu Velho, 1568. Credit: bnf.fr

Over time, Copernicus’ began to feel a growing sense of doubt towards the Aristotelian and Ptolemaic models of the universe. These included the problematic explanations arising from the inconsistent motion of the planets (i.e. retrograde motion, equants, deferents and epicycles), and the fact that Mars and Jupiter appeared to be larger in the night sky at certain times than at others.

Hoping to resolve this, Copernicus used his time at the university to study Greek and Latin authors (i.e. Pythagoras, Cicero, Pliny the Elder, Plutarch, Heraclides and Plato) as well as the fragments of historic information the university had on ancient astronomical, cosmological and calendar systems – which included other (predominantly Greek and Arab) heliocentric theories.

In 1501, Copernicus moved to Padua, ostensibly to study medicine as part of his ecclesiastical career. Just as he had done at Bologna, Copernicus carried out his appointed studies, but remained committed to his own astronomical research. Between 1501 and 1503, he continued to study ancient Greek texts; and it is believed that it was at this time that his ideas for a new system of astronomy – whereby the Earth itself moved – finally crystallized.

The Copernican Model (aka. Heliocentrism):

In 1503, having finally earned his doctorate in canon law, Copernicus returned to Warmia where he would spend the remaining 40 years of his life. By 1514, he began making his Commentariolus (“Little Commentary”) available for his friends to read. This forty-page manuscript described his ideas about the heliocentric hypothesis, which was based on seven general principles.

These seven principles stated that: Celestial bodies do not all revolve around a single point; the center of Earth is the center of the lunar sphere—the orbit of the moon around Earth; all the spheres rotate around the Sun, which is near the center of the Universe; the distance between Earth and the Sun is an insignificant fraction of the distance from Earth and Sun to the stars, so parallax is not observed in the stars; the stars are immovable – their apparent daily motion is caused by the daily rotation of Earth; Earth is moved in a sphere around the Sun, causing the apparent annual migration of the Sun; Earth has more than one motion; and Earth’s orbital motion around the Sun causes the seeming reverse in direction of the motions of the planets.

Heliocentric Model
Andreas Cellarius’s illustration of the Copernican system, from the Harmonia Macrocosmica (1708). Credit: Public Domain

Thereafter he continued gathering data for a more detailed work, and by 1532, he had come close to completing the manuscript of his magnum opus – De revolutionibus orbium coelestium (On the Revolutions of the Heavenly Spheres). In it, he advanced his seven major arguments, but in more detailed form and with detailed computations to back them up.

However, due to fears that the publication of his theories would lead to condemnation from the church (as well as, perhaps, worries that his theory presented some scientific flaws) he withheld his research until a year before he died. It was only in 1542, when he was near death, that he sent his treatise to Nuremberg to be published.

Copernicus’ Death:

Towards the end of 1542, Copernicus suffered from a brain hemorrhage or stroke which left him paralyzed. On May 24th, 1543, he died at the age of 70 and was reportedly buried in the Frombork Cathedral in Frombork, Poland. It is said that on the day of his death, May 24th 1543 at the age of 70, he was presented with an advance copy of his book, which he smiled upon before passing away.

In 2005, an archaeological team conducted a scan of the floor of Frombork Cathedral, declaring that they had found Copernicus’ remains. Afterwards, a forensic expert from the Polish Police Central Forensic Laboratory used the unearthed skull to reconstruct a face that closely resembled Copernicus’ features. The expert also determined that the skull belonged to a man who had died around age 70 – Copernicus’ age at the time of his death.

These findings were backed up in 2008 when a comparative DNA analysis was made from both the remains and two hairs found in a book Copernicus was known to have owned (Calendarium Romanum Magnum, by Johannes Stoeffler). The DNA results were a match, proving that Copernicus’ body had indeed been found.

Copernicus' 2010 grave in Frombork Cathedral, acknowledging him as the father of heiocentirsm.Credit:
Copernicus’ 2010 grave in Frombork Cathedral, acknowledging him as a church canon and the father of heliocentricism. Credit: Wikipedia/Holger Weinandt

On May 22nd, 2010, Copernicus was given a second funeral in a Mass led by Józef Kowalczyk, the former papal nuncio to Poland and newly named Primate of Poland. Copernicus’ remains were reburied in the same spot in Frombork Cathedral, and a black granite tombstone (shown above) now identifies him as the founder of the heliocentric theory and also a church canon. The tombstone bears a representation of Copernicus’ model of the solar system – a golden sun encircled by six of the planets.

Copernicus’ Legacy:

Despite his fears about his arguments producing scorn and controversy, the publication of his theories resulted in only mild condemnation from religious authorities. Over time, many religious scholars tried to argue against his model, using a combination of Biblical canon, Aristotelian philosophy, Ptolemaic astronomy, and then-accepted notions of physics to discredit the idea that the Earth itself would be capable of motion.

However, within a few generation’s time, Copernicus’ theory became more widespread and accepted, and gained many influential defenders in the meantime. These included Galileo Galilei (1564-1642), who’s investigations of the heavens using the telescope allowed him to resolve what were seen at the time as flaws in the heliocentric model.

These included the relative changes in the appearances of Mars and Jupiter when they are in opposition vs. conjunction to the Earth. Whereas they appear larger to the naked eye than Copernicus’ model suggested they should, Galileo proved that this is an illusion caused by the behavior of light at a distance, and can be resolved with a telescope.

1973 Federal Republic of Germany 5-mark silver coin commemorating 500th anniversary of Copernicus' birth. Credit: Wikipedia/Berlin-George
1973 Federal Republic of Germany 5-mark silver coin commemorating 500th anniversary of Copernicus’ birth. Credit: Wikipedia/Berlin-George

Through the use of the telescope, Galileo also discovered moons orbiting Jupiter, Sunspots, and the imperfections on the Moon’s surface, all of which helped to undermine the notion that the planets were perfect orbs, rather than planets similar to Earth. While Galileo’s advocacy of Copernicus’ theories resulted in his house arrest, others soon followed.

German mathematician and astronomer Johannes Kepler (1571-1630) also helped to refine the heliocentric model with his introduction of elliptical orbits. Prior to this, the heliocentric model still made use of circular orbits, which did not explain why planets orbited the Sun at different speeds at different times. By showing how the planet’s sped up while at certain points in their orbits, and slowed down in others, Kepler resolved this.

In addition, Copernicus’ theory about the Earth being capable of motion would go on to inspire a rethinking of the entire field of physics. Whereas previous ideas of motion depended on an outside force to instigate and maintain it (i.e. wind pushing a sail) Copernicus’ theories helped to inspire the concepts of gravity and inertia. These ideas would be articulated by Sir Isaac Newton, who’s Principia formed the basis of modern physics and astronomy.

Today, Copernicus is honored (along with Johannes Kepler) by the liturgical calendar of the Episcopal Church (USA) with a feast day on May 23rd. In 2009, the discoverers of chemical element 112 (which had previously been named ununbium) proposed that the International Union of Pure and Applied Chemistry rename it copernicum (Cn) – which they did in 2011.

Crater Copernicus on the Moon. Mosaic of photos by Lunar Reconnaissance Orbiter, . Credit: NASA/LRO
Mosaic image of the Copernicus Crater on the Moon, taken by the Lunar Reconnaissance Orbiter, . Credit: NASA/LRO

In 1973, on the 500th anniversary of his birthday, the Federal Republic of Germany (aka. West Germany) issued a 5 Mark silver coin (shown above) that bore Copernicus’ name and a representation of the heliocentric universe on one side.

In August of 1972, the Copernicus – an Orbiting Astronomical Observatory created by NASA and the UK’s Science Research Council – was launched to conduct space-based observations. Originally designated OAO-3, the satellite was renamed in 1973 in time for the 500th anniversary of Copernicus’ birth. Operating until February of 1981, Copernicus proved to be the most successful of the OAO missions, providing extensive X-ray and ultraviolet information on stars and discovering several long-period pulsars.

Two craters, one located on the Moon, the other on Mars, are named in Copernicus’ honor. The European Commission and the European Space Agency (ESA) is currently conducting the Copernicus Program. Formerly known as Global Monitoring for Environment and Security (GMES), this program aims at achieving an autonomous, multi-level operational Earth observatory.

On February 19th, 2013, the world celebrated the 540th anniversary of Copernicus’ birthday. Even now, almost five and a half centuries later, he is considered one of the greatest astronomers and scientific minds that ever lived. In addition to revolutionizing the fields of physics, astronomy, and our very concept of the laws of motion, the tradition of modern science itself owes a great debt to this noble scholar who placed the truth above all else.

Universe Today has many interesting articles on ancient astronomy, such as What is the Difference Between the Geocentric and Heliocentric Models of the Solar System.

For more information, you should check out Nicolaus Copernicus, the biography of Nicolaus Copernicus, and Planetary Motion: The History of an Idea That Launched the Scientific Revolution.

Astronomy Cast has an episode on Episode 338: Copernicus.

Sources:

What is the Moon’s Real Name?

We call it the Moon, but… what’s its real name? You know, the name that scientists call the Moon.

As of 2015, there are 146 official moons in the Solar System, and then another 27 provisional moons, who are still waiting on the status of their application. All official moons have names after gods or Shakespeare characters. Names like Callisto, Titan, or Prometheus. But there’s one moon in the Solar System with a super boring name… the one you’re most familiar with: Moon.

But come on, that’s such a boring name. Clearly that’s just its common name. So what’s the Moon’s real name? Its scientific name. The neato cool name. Like Krelon, Krona, Avron or Mua’Dib.

Are you ready for this? The answer is: The Moon. Here’s some hand-waving and excuse making. Really, this is our own damn fault. Until Galileo first turned his telescope to the skies in 1610, and realized that Jupiter had tiny spots of light orbiting around it, astronomers had no idea other planets had moons.

Humans have been around for a few hundred thousand years, and the Moon was a familiar object in the sky. We’ve only had evidence of other moons for a little over 400 years. We didn’t collectively understand the Earth was a planet until Copernicus developed the heliocentric model of the Solar System.

We still have a little trouble with that, even though we’re firing a probe directly at the Sun. We didn’t give into the idea that the Sun was a star until recently. Giordano Bruno proposed the idea in 1590 and we burned him at the stake for suggesting it. Seriously, I can’t stare at this any longer. Yes, we’re awful. I’m going to talk about “the Moon” again.

Scientists classify the Moon as a natural satellite. Somehow this helps distinguish it from the artificial satellites we’ve been launching for the last 60 years.

High resolution photo map of the moon's far side imaged by NASA's Lunar Reconnaissance Orbiter. Mare Moscoviense lies at upper left and Tsiolkovsky at lower left. Click for a hi res image. Credit: NASA
High resolution photo map of the moon’s far side imaged by NASA’s Lunar Reconnaissance Orbiter. Credit: NASA

What about terms like “Luna”? That’s Latin for Moon. It’s not an official title or scientific term, but ooh, fancy. Latin.

If you want to make sure people know you’re talking about “The Moon” and not “a moon”, it’s all about capitalization. Put a capital “M” in front of “oon” and you’re good to go.

The name of our solar system? It’s the Solar System (again, capitalized). Our galaxy? The Galaxy with a capital G. The universe? Capital U Universe.

What about the Sun? Isn’t it “sol”? That’s just the Latin word for “sun”. Helios? Greek God version of the Sun.

If we ever discover that we’re really living in a multiverse, we’ll need to give those other universes names. And people will wonder what the actual official title is for the Universe. I’ll make another video when that happens, I promise.

The official advice from the International Astronomical Union, who are the people you’re still mad at about Pluto, is that the capitalization is what makes the definition.

Supermoon through the clouds on September 9, 2014. Credit and copyright: scul-001 on Flickr.
Supermoon through the clouds on September 9, 2014. Credit and copyright: scul-001 on Flickr.

Not everyone in the world adheres to the capitalization so carefully, which can tend to some confusion. Are we talking about the sun or the Sun? As someone who writes space articles, let me assure you, messing this up will light up the comments section with “Which is better Deep Space 9 vs. Voyager” level of shrill all caps screaming.

Calling it “the Moon” is kind of boring, but that’s only because scientific discovery has pushed our understanding of the Universe so far out. It’s amazing to think that we’ve discovered so many other moons in the Solar System, and soon, we’ll find them around other stars.

So, for now it’s The Universe. When we find others, this one will still be THE Capital-U Universe and the new ones will be Nimoy and Sagan and Clarke.

Why don’t we give the Moon a new name. Something with a little more razzle-dazzle. Make your suggestions in the comments below. Alternately, suggest a fancy Latin name of “Guide to Space”, I’ve got dibs on “Aether Libris”.

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What Is The Difference Between the Geocentric and Heliocentric Models of the Solar System?

The Solar System. Image Credit: NASA

What does our Solar System really look like? If we were to somehow fly ourselves above the plane where the Sun and the planets are, what would we see in the center of the Solar System? The answer took a while for astronomers to figure out, leading to a debate between what is known as the geocentric (Earth-centered) model and the heliocentric (Sun-centered model).

The ancients understood that there were certain bright points that would appear to move among the background stars. While who exactly discovered the “naked-eye” planets (the planets you can see without a telescope) is lost in antiquity, we do know that cultures all over the world spotted them.

The ancient Greeks, for example, considered the planets to include Mercury, Venus, Mars, Jupiter and Saturn — as well as the Moon and the Sun. The Earth was in the center of it all (geocentric), with these planets revolving around it. So important did this become in culture that the days of the week were named after the gods, represented by these seven moving points of light.

All the same, not every Greek believed that the Earth was in the middle. Aristarchus of Samos, according to NASA, was the first known person to say that the Sun was in the center of the universe. He proposed this in the third century BCE. The idea never really caught on, and lay dormant (as far as we can tell) for several centuries.

Earth is at the center of this model of the universe created by Bartolomeu Velho, a Portuguese cartographer, in 1568. Credit: NASA/Bibliothèque Nationale, Paris
Earth is at the center of this model of the universe created by Bartolomeu Velho, a Portuguese cartographer, in 1568. Credit: NASA/Bibliothèque Nationale, Paris

Because European scholars relied on Greek sources for their education, for centuries most people followed the teachings of Aristotle and Ptolemy, according to the Galileo Project at Rice University. But there were some things that didn’t make sense. For example, Mars occasionally appeared to move backward with respect to the stars before moving forward again. Ptolemy and others explained this using a system called epicycles, which had the planets moving in little circles within their greater orbits.

But by the fifteen and sixteenth centuries, astronomers in Europe were facing other problems, the project added. Eclipse tables were becoming inaccurate, sailors needed to keep track of their position when sailing out of sight of land (which led to a new method to measure longitude, based partly on accurate timepieces), and the calendar dating from the time of Julius Caesar (44 BCE) no longer was accurate in describing the equinox — a problem for officials concerned with the timing of religious holidays, primarily Easter. (The timing problem was later solved by resetting the calendar and instituting more scientifically rigorous leap years.)

While two 15th-century astronomers (Georg Peurbach and Johannes Regiomontanus) had already consulted the Greek texts for scientific errors, the project continued, it was Nicolaus Copernicus who took that understanding and applied it to astronomy. His observations would revolutionize our thinking of the world.

Retrograde motion of Mars. Image credit: NASA
Retrograde motion of Mars. Image credit: NASA

Published in 1543, Copernicus’ De Revolutionibus Orbium Coelestium (On the Revolutions of the Heavenly Bodies) outlined the heliocentric universe similar to what we know today. Among his ideas, according to Encyclopedia Britannica, was that the planets’ orbits should be plotted with respect to the “fixed point” Sun, that the Earth itself is a planet that turns on an axis, and that when the axis changes directions with respect to the stars, this causes the North Pole star to change over time (which is now known as the precession of the equinoxes.)

Putting the Sun at the center of our Solar System, other astronomers began to realize, simplified the orbits for the planets. And it helped explain what was so weird about Mars. The reason it backs up in the sky is the Earth has a smaller orbit than Mars. When Earth passes by Mars in its orbit, the planet appears to go backwards. Then when Earth finishes the pass, Mars appears to move forwards again.

Other supports for heliocentrism began to emerge as well. Johannes Kepler’s rules of motions of the planets (based on work from him and Tycho Brahe) are based on the heliocentric model. And in Isaac Newton’s Principia, the scientist described how the motions happen: a force called gravity, which appears to be “inversely proportional to the square of the distance between objects”, according to the University of Wisconsin-Madison.

Artist's conception of the Kepler Space Telescope. Credit: NASA/JPL-Caltech
Artist’s conception of the Kepler Space Telescope. Credit: NASA/JPL-Caltech

Newton’s gravity theory was later supplanted by that of Albert Einstein, who in the early 20th century proposed that gravity is instead a warping of space-time by massive objects. That said, heliocentric calculations guide spacecraft in their orbits today and the model is the best way to describe how the Sun, planets and other objects move.

Universe Today has articles on both the heliocentric model and the geocentric model, and Astronomy Cast has an episode on the center of the universe.

Watch Live: Next-Gen Environment Satellite Aims For Space

UPDATE, APRIL 4: The satellite safely made it into space! Watch the launch replay and successful satellite separation here.

Just in case you aren’t already in French Guiana, here’s your chance to watch a European environment radar satellite take a rocket ride. Tune into the webcast above to see Sentinel-1A’s launch. If the schedule holds, the launch will be at 5:02 p.m. EDT (9:02 p.m. UTC) on April 3, 2014. Watch live above!

ESA heralds Sentinel-1 as a “new era in Earth observation” because the satellite duo (yes, it will be eventually two satellites) will vastly improve their ability to send out information on natural disasters and quick-moving Earth observation events. Sentinel-1 will in fact be the first of a satellite series feeding into the same information system.

Once the second half of the duo launches in 2016, Sentinel-1 will have a wide swath of geographical coverage, could go to the same areas quickly, and would send data out quickly. Repeatable and rapid Earth observations will bring data quickly into the hands of the authorities who could make decisions about evacuations and other things. 

This information will be fed into Copernicus, a new system that will co-ordinate all of the Sentinel satellites for users to gain information.

“The Sentinels will provide a unique set of observations, starting with the all-weather, day and night radar images from Sentinel-1 to be used for land and ocean services,” ESA stated in an explanation about Copernicus.

“Sentinel-2 will deliver high-resolution optical images for land services and Sentinel-3 will provide data for services relevant to the ocean and land. Sentinel-4 and Sentinel-5 will provide data for atmospheric composition monitoring from geostationary and polar orbits, respectively.”

And here are a few of the other applications ESA foresees it would be useful for: sea-ice measurements, looking for oil spills, tracking ships, flagging land with “motion risks” and also doing mapping for the forestry industry.

As far as the webcast, there’s a schedule of speeches and events beforehand at the European Space Agency’s space operations center in Darmstadt, Germany. Be sure to tune in a bit earlier at 3:30 p.m. EST (7:30 p.m. UTC) to see the ceremonies.

Source: European Space Agency

Who Discovered Jupiter?

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Jupiter is one of the 5 planets visible with the unaided eye. That means you can go out on a clear night, when Jupiter is up in the sky, and see it with your own eyes. No telescope is necessary. In fact, it’s one of the brightest objects in the sky. When Jupiter is there, it’s hard not to see it. So it’s kind of hard to wonder who discovered Jupiter, since humans would have known about it for tens of thousands of years.

Ancient astronomers didn’t have telescopes, but they knew there was something strange about the planets. They tracked the motion of the planets with incredible accuracy and believed that they were somehow associated with gods in their mythologies. Jupiter is named after the Roman god, thought to be the head of the gods; he’s the same as Zeus in Greek mythology.

Perhaps a better question might be, who discovered Jupiter the planet. In other words, when did astronomers realize that Jupiter was really a planet. That discovery happened when astronomers realized that the Earth was really just a planet as well, orbiting the Sun in the Solar System. The new model for the Solar System was developed by Nicolaus Copernicus in the 16th century. By placing the Sun at the center of the Solar System, Copernicus developed a model that better explained the motions of the planets as they moved through the sky.

This model was confirmed when Galileo pointed his first rudimentary telescope at Jupiter. What he saw was the disk of Jupiter and the 4 largest moons orbiting the planet. Since all the heavenly bodies were thought to orbit the Earth, it was thought to be impossible for objects to orbit one another.

Once astronomers knew that Jupiter was a planet, and they had better telescopes to study it, the exploration of Jupiter could really begin. Better and better images were taken of the planet, and more moons and even rings were discovered orbiting the planet.

And then in the space age, the first spacecraft were sent to explore Jupiter. The first spacecraft to arrive at Jupiter was NASA’s Pioneer 10 in 1973, followed by Pioneer 11 a few months later. These spacecraft returned images of Jupiter’s swirling cloud tops, discovered more about its composition, and revealed features of its moons.

We have written many articles about the discovery of planets in the Solar System. Here’s an article about the discovery of Uranus, and another about the discovery of Neptune.

You can also learn more about Jupiter from NASA’s Solar System Exploration Guide to Jupiter.

We have also recorded an episode of Astronomy Cast all about Jupiter. Listen to it here, Episode 56: Jupiter.

Reference:
NASA