Ch2 - Astronomical Model
We live on the planet Earth, one of 8 planets of the Solar System. According to scientists, the Solar System is 4,6 billion years old. It has changed a lot during that time: its planets have changed their orbits and some of the small celestial bodies and cosmic dust disappeared.
The Sun is in the centre of the Solar System. It's the biggest and the brightest object in our sky. The Sun accounts for 99,86% of the mass of the solar system. The Sun produces massive amounts of energy because of hydrogen to helium conversion.
The Sun formed from a cloud of gas and dust and, like all stars, it changes constantly. Currently, it is in a phase known as the yellow dwarf. When the reserves of helium run out, which could happen in 5 billion years, the Sun will grow and consume the three nearest planets. It will become a red giant. After a next billion years, it will start to shrink and cool down, becoming first a white and then a black dwarf.
Nowadays it is common knowledge that all planets of the Solar System orbit the Sun. However, this heliocentric theory is relatively new. It was proposed by Nicolas Copernicus in XVI century in his book “On the Revolutions of the Heavenly Spheres”. Before it was officially acclaimed, his theory was criticized by supporters of the previous theory, who believed that the Earth was the centre of the universe and that all celestial bodies orbited the Earth. The heliocentric theory was so controversial that in 1616 the Catholic Church officially denunciated it as a danger to faith.
All planets of the Solar System move similarly. They all circle around the Sun counter-clockwise (as observed from the Sun’s north pole). The further from the Sun a planet is, the larger circle it has to complete. It also moves slower, because the Sun’s gravitational pull weakens.
All planets spin on their axis. This movement is also counter-clockwise. Venus is the only exception. Various theories claim that it was hit by a massive asteroid in the past, which changed its spinning direction.
One complete rotation of a planet on its axis is called a day. It can last a different time on different planets: on a gas giant, such as Jupiter, a day lasts only a few hours, while on Venus, one day is as long as 243 days on Earth.
One turn around the Sun is called a year.
The Earth’s movement around the Sun and inclination of its axis to the orbit result in changing light conditions throughout the yearly cycle. This results in many interesting phenomenons, such as changing of the seasons.
Planets of the Solar System can be divided into inner planets and outer planets. The inner planets are closer to the Sun and are terrestrial planets. Outer planets are gas giants and have visible rings.
Inner and outer planets are divided by an asteroid belt. Asteroids have various sizes: from practically microscopic to giants with a diameter of hundreds of kilometres. The number of planetoids in the belt is estimated at about 1,7 million.
The planet nearest to the Sun, Mercury, is also the smallest. Interestingly, it’s practically devoid of atmosphere, which is constantly being blown away by the solar wind that is very strong near the Sun.
The biggest planet of all in the Solar System is Jupiter. It is 2,5 times heavier than all the other planets put together. Also, it is covered in interesting swirls of clouds. The most visible one is the Great Red Spot, an ongoing storm that was probably first observed in 1655.
Most of the Solar System planets have moons. Jupiter has the most moons: 66. The only moonless planets are Mercury and Venus.
Moon is a celestial body orbiting a planet. There are about 173 moons in the Solar System.
Interestingly, only one side of the Moon can be observed from the Earth. The other side first became visible to people thanks to the photographs taken by cosmic probes.
The Solar System, although vast, is just a tiny part of the Universe. It is situated in the Milky Way, along with 200 billion of other stars.
Watching the night sky with a naked eye, we can spot about 3 to 4 thousands stars. The brightest of them all is Sirius, the second-brightest – Canopus. Alfa Centauri, which is the closest to us (after the Sun, of course) is only the third brightest star on our sky.
Build
To build this construction, you will need LEGO Education WeDo
Explore
The Astronomical Model shows how a satellite circulates around a planet. The Earth and the Moon move in a similar manner.
What is more, the construction also works as an astronomical clock.
Polish astronomer Nicolaus Copernicus was the first to discover that the Earth revolves arond the Sun and not the other way around.
The construction relies on a motor and a distance sensor.
1. The motor propels the entire system.
2. The hub powers the motor and the sensor, it also allows you to program the construction.
3. The sensor allows to count the number of rotations.
1. At the very center there is a star, like the Sun is at the center of the Solar System.
2. Around the star orbits a planet with one moon.
3. The moon orbits around the planet.
1. The mechanism responsible for the movement of the planet model is inside a sturdy case.
1. The motion is transferred from the motor through a worm gear.
Its ratio is 1:8, which means that the axle with the cogwheel rotates 8 times slower than the axle with the worm.
Moreover, the transmission changes the direction of rotation.
2. The second transmission is propelled by the wheel with 8 teeth meshed with the wheel with 24 teeth; therefore, the larger wheel rotates 3 times slower than the smaller one.
This mechanism is responsible for the movement of the satellite around the planet.
1. These four bushings are affixed to the case. They are immobile.
2. Thanks to the movement of the axle propelled by the motor, the pulley is set in motion by the rubber. This is an example of a belt transmission.
1. The other part of the mechanism responsible for the movement is the gear transmission.
2. The propulsion from the rotating pulley is transferred through the gears to the element, which supports the planet and its natural satellite model.
1. This is how the movement of a satellite around a planet looks like.
This is how the movement of a planet and its satellite around a star looks like.
When the entire model is on, these both movements are executed at the same time.
The mechanism responsible for this motion is composed of many elements working together.
1. By rotating, this axle sets in motion the beam with the models installed on it.
2. In this model, the circular motion of the planet is depicted by means of the "orbital" motion.
Program
Let's begin programming with the Start Block.
