This article aims to debunk some of the biggest myths and misconceptions related to astronomy, from black holes to the dark side of the moon, the 12 zodiacal constellations, and more. So read on as we explore the Top 15 Common Astronomy Misconceptions:
1: Copernicus first suggested Earth revolves around Sun
Polish astronomer Copernicus (1473-1543) was not the first person to suggest that the Earth revolves around a stationary Sun, but he was the first to revive and elaborate on the heliocentric theory proposed by the early Greek astronomer Aristarchus of Samos (310BC–230BC). Unfortunately, Aristarchus’ heliocentric theory was rejected in favor of Aristotle’s common sense geocentric theory and, supported by religion, it remained the established belief for the next 16 centuries until the time of the Renaissance and Copernicus.
2: The Middle Ages thought the Earth was flat
In the sixth century BCE, ancient Greeks such as Pythagoras first suggested the world was round, and a century later no Greek thinker of any repute thought the Earth was anything but spherical. Eratosthenes (276–195 BCE) then calculated the Earth’s circumference (24,902 miles) to be roughly 24,662 miles and ever since Greek scientific knowledge of a round world has never faded from astronomy history.
3: Galileo invented the Telescope
In 1608, Dutch spectacle maker Hans Lippershey is generally credited for having invented the refracting telescope, which he was hoping to sell to the government for military use. On hearing of the new device, Galileo Galilei subsequently constructed and improved on the technology, and the following year became the first person to use the telescope for astronomy purposes.
4: Telescopes are constructed to produce magnification
The primary purpose of a telescope is to use a lens or mirror (aperture) to gather light and make extremely dim objects visible. Magnification is of only secondary importance as many objects in the night sky are already quite large but need the light-collecting capabilities of a telescope to create detailed images. If they were visible to the naked eye, for instance, the Orion Nebula would appear bigger than the Moon, or the Andromeda Galaxy (M31) six times the Moon’s width.
5: Total Eclipses of the Sun are rare
A solar eclipse occurs when a new moon passes between the Sun and Earth, and are usually defined as either total, partial, or annular. These natural phenomenona take place on average twice each year, but with the rarer total solar eclipses happening about once every 1.5 years. However, observing from one specific location on the Earth, there may be centuries between total solar eclipses.
6: The Dark Side of the Moon is in perpetual darkness
Just like any other moon or planet in our solar system, the Moon has a day and night cycle and spends around half its time in darkness and the other half lit up by the Sun. However, because the Moon‘s rotation matches that of the Earth, from our planet’s perspective we always end up seeing the same hemisphere of the Moon, with 41% of the Moon’s surface always hidden from view. Nevertheless, the dark side of the Moon is actually just its night side, and a better term for that region would be the Moon’s far side.
7: Mercury is the hottest Planet in the Solar System
In general the nearer a planet is to the Sun the hotter is its temperature. Nevertheless, Mercury (427c) has almost no atmosphere to hold onto its heat and so the planet is actually cooler than Venus (460c), whose thick carbon dioxide atmosphere acts as a blanket to trap in the sun’s heat.
8: The Outer Planets are Gas Giants
The outer planets are often referred to as the gas giants, but Jupiter, Saturn, Uranus, and Neptune would better be described as liquid worlds because as pressure increases, their extensive gaseous atmospheres are eventually compressed into liquid oceans of mostly hydrogen and helium. Hydrogen is further forced into a metallic state at these planets’ cores, accounting for the strong magnetic fields which surround all the outer planets.
9: Meteor, Meteoroid and Meteorite are the same thing
Meteoroid, meteor and meteorite are three of the most misused words in astronomy. Simply stated, a meteoroid is a piece of rock or iron debris floating about in space, which then becomes a meteor or shooting stars as it enters and burns up in Earth’s atmosphere. A durable enough meteor that is then able to reach the Earth’s surface without being vaporized is called a meteorite, and they are often covered with a dark, glassy layer called a fusion crust.
10: There are 12 Zodiacal Constellations
If the stars were visible in the daytime, the sun would appear to pass from one zodiac constellation to the next, completing one circle around the sky each year. In astrology, there are 12 signs of the zodiac each occupying an equal 30 degrees width of this ecliptic band, but in astronomy, the zodiac constellations are actually irregular in size and the sun passes through a 13th constellation known as Ophiuchus, the Serpent Holder.
11: The Big Dipper is a Constellation
Ursa Major is the most famous of all northern star constellations and is easily recognized by a remarkable arrangement of seven bright stars known as The Big Dipper or Plough. However, this clearly identifiable grouping of stars is actually known as an asterism, and The Big Dipper forms less than half the official constellation known as Ursa Major.
12: Polaris has always been the North Star
Polaris, the North Star, is aligned to the Earth’s axis of rotation such that when viewed from the North Pole it is found directly overhead. However, a wobble in the Earth’s rotation causes the direction where the axis points to slowly change over centuries with one complete precession cycle taking 26,000 years. Currently, Polaris in the constellation Ursa Minor is our North Star, but in 3000 BCE it was a star called Thuban in Draco. By 3000 AD, Gamma Cephei in the constellation Cepheus is expected to replace Polaris as the Pole star, followed by Iota Cephei around 5200 AD, and so on.
13: Alpha Centauri is the closest Star to the Sun
To the naked eye, the third brightest star in the night sky is Alpha Centauri located 4.37 light-years away in the constellation Centaurus. However, our nearest stellar neighbor is actually a binary system consisting of the stars Alpha Centauri A and B, as well as a red dwarf star called Proxima Centauri, which may or may not be gravitationally bound. In any case, Proxima Centauri is about 0.2 light-years closer than the other two making it the nearest star to Earth, although it is not visible without using a telescope.
14: Black Holes destroy everything
Black Holes do not suck everything in around them but actually have the same gravitational field in space as any other object of the same mass. Bodies can form a stable orbit around them, and things are more likely to just fall into them if they get too near to the black hole’s event horizon.
15: Our Universe is The Universe
To ancient astronomers, the solar system represented the entire universe and it wasn’t until 1923 that Edwin Hubble using a 60″ reflector telescope proved that our own Milky Way was an “island universe” and that there were countless separate galaxy systems outside of our own Milky Way. Later with the Big Bang theory, it became fashionable to think of our observable universe as everything, but more recently cosmologists are increasingly exploring the possibility we live in a multiverse containing various parallel universes.
As one theory goes, because the observable universe only extends as far as the 13.7 billion light-years it has expanded since the Big Bang, the space-time which exists beyond that distance can be thought of as its own separate universe with a multitude of universes then existing next to one other in a patchwork of different universes.