Different Models of the Universe

Before the telescope was invented, ancient astronomers only used their unaided eyes to observe the sky and the stars. Eventually, they created models of the universe. Here are some astronomers who constructed their own models of the universe. 

Geocentric Model- Believed that Earth was at the center of the universe. Here are some models that are geocentric model.

1. Eudoxus of Cnidus

(Eudoxus's geocentric model of the universe:

 Earth surrounded by concentric spheres)

According to Eudoxus's Model, the universe was composed of Earth, five other planets that are visible with the unaided eye (Mercury, Venus, Mars, Jupiter, and Saturn), sun, moon and motionless stars which were enclosed in spheres. Earth was motionless at the center of the universe. Each of the five other planets was enclosed in four concentric circles. The sun and moon were each enclosed in three concentric spheres. Lastly, the group of motionless stars lay in the outermost sphere. 

FACT:

Eudoxus was a Greek philosopher, astronomer,and mathematician. He was considered the first astronomer to explain the retrograde motion of the planets in the sky.

2. Aristotle

(Aristotle's model of the universe)

Aristotle's model showed that the universe was spherical and finite. Just like Eudoxus, he perceived Earth was at he center of the universe and was stationary. He believed so because Earth is too big to move; it could not move.

He believed that Earth was composed of four elements- earth, water, air, and fire. He further described that each ring was in physical contact with one another.

FACT:

Aristotle was a Greek philosopher who wrote about many subjects and made a number of important contributions to science based ones such as physics, biology, anatomy, geology and zoology. 

3. Claudius Ptolemaeus (Ptolemy)

(Ptolemy's model of the universe)

In his model, it is assumed that Earth was at the center of the universe, while the other celestial bodies revolved around Earth in perfect circles with constant velocity.

(A closer look at Ptolemaic's model of the universe)

Ptolemy assumed that the planets revolved on epicycles (small spheres) which move around the deferent (larger spheres).The center of the deferent is called the eccentic. Ptolemy did next was to "move Earth from its original position to a position below the center of the system that is still inside the deferent. 

4. Tycho BraheIn Brahe's model of the universe, called the Tychonic system, Earth was at the center and the sun and the moon around it, and all the other planets orbited the sun. 

Fact:
Tycho Brahe was a Danish astronomer who also made planetary observations. He observed the sky night after night using the most accurate instruments he could find.








Heliocentric Model- Believed that the sun was at the center of the universe. Here are some models that are heliocentric model.

1. Aristarchus of Samos

Aristarchus proposed that the sun and the fixed stars were at rest, while earth revolved around the sun in a circular path.

He wrote a book entitled On the Sizes and Distances of the Sun and the Moon. In this book, Aristarchus calculated the distances from Earth by estimating the relative angles of the moon and the sun from Earth. He had 3 assumptions:(a)Earth was spherical (b)It is far from the sun (c)Moon passes through the Earth's shadow when they align.


FACT:

Aristarchus was a Greek astronomer who made the first attempt to create a heliocentric model.

2. Nicolaus Copernicus

Copernicus strongly believed in the heliocentric model because there were loopholes in the Ptolemic model in nterms of predicting the positions of the planets. In Copernicus's model, it could be concluded that (a)heavenly bodies exhibited constant circular and perpetual motion along their epicycles, (b) the sun was at the center of the universe, and (c) the order of the planets from the sun is Mercury, Venus, Earth (and moon), Mars, Jupiter, Saturn, and beyond the planets were the fixed stars.
FACT:Copernicus, a Polish astronomer, revived the heliocentric model of Aristarchus. He was hesitant to publish his findings because he was afraid of condemnation. It took him long time to publish his work. His works were published a year ago before his death. 

About the Blog

                                                         

The Panda Astronaut

Everybody wants to be an astronaut right? Everybody wants to explore and travel outside this earth. With this blog, we will give you the experience to be an astronaut and be in space! We will give you information about the solar system and facts about different planets. 


A special thanks to my ABM classmates and most especially to my beautiful Physical Science teacher Ms. Juliet Tilan. 

Planets

M E R C U R Y

Mercury is the smallest planet in our solar system. It’s just a little bigger than Earth’s moon. It is the closest planet to the sun, but it’s actually not the hottest. Venus is hotter.

Along with Venus, Earth, and Mars, Mercury is one of the rocky planets. It has a solid surface that is covered with craters. It has a thin atmosphere, and it doesn’t have any moons. Mercury likes to keep things simple.

This small planet spins around slowly compared to Earth, so one day lasts a long time. Mercury takes 59 Earth days to make one full rotation. A year on Mercury goes by fast. Because it’s the closest planet to the sun, it doesn’t take very long to go all the way around. It completes one revolution around the sun in just 88 Earth days. If you lived on Mercury, you’d have a birthday every three months!

(This is Mercury's northern horizon as seen by
the MESSENGER spacecraft during its third flyby.)

A day on Mercury is not like a day here on Earth. For us, the sun rises and sets each and every day. Because Mercury has a slow spin and short year, it takes a long time for the sun to rise and set there. Mercury only has one sunrise every 180 Earth days! 

(Retrieved from: https://spaceplace.nasa.gov/all-about-mercury/en/)

V E N U S

Venus is the second planet from the sun, is named for the Roman goddess of love and beauty. The planet — the only planet named after a female — may have been named for the most beautiful deity of her pantheon because it shone the brightest of the five planets known to ancient astronomers.

In ancient times, Venus was often thought to be two different stars, the evening star and the morning star — that is, the ones that first appeared at sunset and sunrise.

(Venus in close up)

Venus is the hottest world in the solar system. Although Venus is not the planet closest to the sun, its dense atmosphere traps heat in a runaway version of the greenhouse effect that warms Earth. As a result, temperatures on Venus reach 870 degrees Fahrenheit (465 degrees Celsius), more than hot enough to melt lead. Probes that scientists have landed there have survived only a few hours before being destroyed. 

(Retrieved from: http://www.space.com/44-venus-second-planet-from-the-sun-brightest-planet-in-solar-system.html)

E A R T H

Earth is a rocky, terrestrial planet. It has a solid and active surface with mountains, valleys, canyons, plains and so much more. Earth is special because it is an ocean planet. Water covers 70% of Earth's surface. It is the only planet in our solar system that supports life.

A day on earth lasts a little a little under 24 hours. One year on earth lasts 365. 25 days. That extra 0. 25 extra means every four hours we need to add one day in our calendar. We call it a leap day (in a leap year).

(This Apollo 11 picture taken by an astronaut in 1969
shows the Earth rising over the moon.)

The earth's atmosphere is made mostly of nitrogen and has plenty of

oxygen for us to breathe. The atmosphere also protects us from incoming meteoroids, most of which break up in our atmosphere before they can strike the surface as meteorites.

(Retrieved from:https://spaceplace.nasa.gov/all-about-earth/en/)

M A R S

( NASA's Mars Exploration Rover Opportunity took this picture
with its panoramic camera near "Solander Point" on Mars.)

Mars is a cold desert world. It is half the size of Earth. Mars is sometimes called the Red Planet because of the rusty iron in the ground. It has 2 moons: Phobos and Deimos.

Like Earth, Mars has seasons, polar ice caps, volcanoes, canyons, and weather. It has a very thin atmosphere made of carbon dioxide, nitrogen, and argon.

There are signs of ancient floods on Mars, but now water mostly exists in icy dirt and thin clouds. On some Martian hillsides, there is evidence of liquid salty water in the ground.

Scientists want to know if Mars may have had living things in the past. They also want to know if Mars could support life now or in the future. We have sent 20 spacecraft to visit Mars and Mars is the planet that we've sent rovers too. They drive around Mars, taking pictures and measurements.

(Retrieved from: https://spaceplace.nasa.gov/all-about-mars/en/)

J U P I T E R

Jupiter is the biggest planet in our solar system. It's similar to a star, but it never got big enough to start burning. It is covered in swirling cloud stripes. It has big storms like the Great Red Spot, which has been going for hundreds of years. Jupiter is a gas giant and doesn't have a solid surface, but it may have a solid inner core about the size of Earth. Jupiter also has rings, but they're too faint to see very well.

(This picture taken by Voyager 2 shows the Great Red Spot.)

Jupiter is a gas giant. It's made mostly of Hydrogen and Helium. It also have a thick atmosphere. One day on Jupiter goes by in just 10 hours and one year in Jupiter is the same as 11.8 Earth years. 

(Retrieved from: https://spaceplace.nasa.gov/all-about-jupiter/en/)

S A T U R N 

Saturn isn’t the only planet to have rings, but it definitely has the most beautiful ones. The rings we see are made of groups of tiny ringlets that surround Saturn. They’re made of chunks of ice and rock. Like Jupiter, Saturn is mostly a ball of hydrogen and helium.When Galileo Galilei saw Saturn through a telescope in the 1600s, he wasn't sure what he was seeing. At first he thought he was looking

(The Cassini spacecraft took this picture of Saturn's
rings. You can see the grey and tan colors.)

at three planets, or a planet with handles. Now we know those "handles" turned out to be the rings of Saturn.

One day on Saturn lasts 10.7 hours and one year on Saturn is the same as 29.5 earth years. Saturn has 53 moons. It also has 9 unconfirmed moon we need to learn more about. 

(Retrieved from: https://spaceplace.nasa.gov/all-about-saturn/en/_)

U R A N U S

Uranus was discovered bin 1781 by William Herschel in Great Britain. Uranus is made of water, methane, and ammonia fluids above a small rocky center. Its atmosphere is made of hydrogen and helium like Jupiter and Saturn, but it also has methane. The methane makes Uranus blue.


Uranus also has faint rings. The inner rings are narrow and dark. The outer rings are brightly colored and easier to see. Like Venus, Uranus rotates in the opposite direction as most other planets. And unlike any other planet, Uranus rotates on its side.

(This picture shows Uranus surrounded by its four major rings and
by 10 of its moons. This image has colors added to show the
different altitudes and thicknesses of clouds in the atmosphere.)

One day on Uranus lasts a little over 17 hours and one year on Uranus is the same as 84 earth years. It has 27 moons. 

(Retrieved from: https://spaceplace.nasa.gov/all-about-uranus/en/

N E P T U N E

Neptune is dark, cold, and very windy. It's the last of the planets in our solar system. It's more than 30 times as far from the sun as Earth is. Neptune is very similar to Uranus. It's made of a thick soup of water, ammonia, and methane over an Earth-sized solid center. Its atmosphere is made of hydrogen, helium, and methane. The methane gives Neptune the same blue color as Uranus. Neptune has six rings, but they're very hard to see.One day in Neptune goes by 16 hours and Neptune has such a long

(Clouds streak across Neptune.)

journey around the sun it takes 164 earth hours to go around once. It was discovered in 1864 by Urbain Le Verrier, John Couch Adams and Johann Gale. Only Voyager 2 has visited Neptune.

(Retrieved from: https://spaceplace.nasa.gov/all-about-neptune/en/)  

New Planet Discovered!

7 new Earth-like exoplanets discovered, NASA announces

(Retrieved from: http://www.foxnews.com/science/2017/02/22/7-new-earth-like-exoplanets-discovered-nasa-announces.html)

Talk about lucky number seven. Astronomers have discovered not one, not two, but seven Earth-sized planets orbiting a star called TRAPPIST-1.

What’s more, three of them are in the habitable zone— the happy place where liquid water can exist on the surface of rocky planets, as it’s not too hot or cold. (Although liquid water could potentially exist on any of the seven, NASA said, it likes the odds on those three best.) The space agency calls the discovery of the fascinating solar system record-breaking.

 
“The discovery gives us a hint that finding a second Earth is not just a matter of if, but when,” Thomas Zurbuchen, associate administrator of the Science Mission Directorate at NASA Headquarters, said at a news conference announcing the discovery.

Zurbuchen called it a "major step forward" towards the goal of answering the very big question: Is there life on other worlds?

The discovery "is very promising for the search for life beyond our solar system,” Michael Gillon, astronomer at the University of Liege in Belgium, added during the press conference.

This is the first time astronomers have found so many Earth-sized planets circling the same sun.

Since the seven planets orbit the star-- which is roughly 40 light years away-- fairly close to each other, the view from one planet would reveal other planets to look as big, if not bigger, than the way we see the moon from Earth. 

“If you were on the surface of one of these planets, you would have a wonderful view [of] the other planets,” Gillon said, adding that they would be much more than just "dots of light" in the sky, as we see other planets, like Venus, from our home planet.

(The planets “e,” “f,” and “g” — marked in green are directly in the “habitable zone” of this star system.)

Observing the Outerspace

Observing without the Telescope

Telescope is very essential in studying Astronomy. Telescope was invented by Hanz Lippershey, a lens maker from Germany. But before the telescope was invented, many phenomena were already observed and recorded. Here are some of them:

• Pleiades star cluster- also known as the Seven Sisters or M45 is visible from virtually every place that humanity inhabits Earth’s globe. It can be seen from as far north as the north pole, and farther south than the southernmost tip of South America. It looks like a tiny misty dipper of stars. Once this star appears in the sky, the Incas mark this as the start of their year.

(The Pleiades – aka the Seven Sisters – captured by Greg Hogan in Kathleen, Georgia on October 31, 2016.)

• Constellations- Across cultures, ancient civilizations saw different patterns and shapes in the constellations. Ancient Egyptians considered the constellations as representations for their gods. Ancient people have also used the constellations to determine when to plant and harvest crops. It also helped in navigation.

   

(Different types of constellations)

• First sight of Venus- In Mayan culture, the position of Venus was used as a basis in deciding whether to start a battle against another tribe.

(A platform used by the Mayans to observed the planet Venus)

Observing with the Telescope

Galileo Galileo was the first to use the telescope to observe astronomical phenomena in 1609. Galileo's use of telescope of astronomical purposes caused paradigms to shift. Here are some of Galileo's discoveries with the aid of the telescope:

(Galileo's drawing of phases of the moon)

• Lunar craters- Galileo confirmed that there were mountains on the moon. He found the "surface of the moon to be not smooth, even and perfectly spherical,...,but on the contrary, to be uneven, rough, and crowded with depressions and bulges. And it is like the face of the earth itself, which is marked here and there with chains of mountains and depths of valleys." He calculated the heights of the mountains by measuring the lengths of their shadows and applying geometry. 

• Moons of Jupiter- In 1610, Galileo saw Jupiter accomplished by four seemingly fixed "stars". These stars were later on identified as the moons of Jupiter. Today these four moons are known as the Galilean satellites; Io, Europa, Ganymede and Callisto.

  

  (Galileo's drawing of the moons of Jupiter of successive nights)

• Phases of Venus- Using his telescope, Galileo found that Venus went through phases, just like our Moon. But, the nature of these phases could only be explained by Venus going around the Sun, not the Earth. Galileo concluded that Venus must travel around the Sun, passing at times behind and beyond it, rather than revolving directly around the Earth. Galileo's observations of the phases of Venus virtually proved that the Earth was not the center of the universe. It was this assertion which most angered the Church leaders of the time. 

• Sunspots- These are dark spots on the sun which are relatively colder than the other areas in the sun. Galileo was one of the first astronomers to observe this phenomenon. He was who proved mathematically that these spots are indeed on the sun's surface. 

(Sunspots drawn by Galileo)