Astronomical Concepts – Week 2

The main topics this week were the solar system, gravity and the tidal effect. I have previously written on my blog about the solar system so for this entry I will just write about gravity and the tidal effect.

The two main theories of gravity come from Isaac Newton and Albert Einstein, both are used today, both are brilliant and vastly different. Gravity is one of the 4 main forces of nature, it works on grand scales, the great sculpture of the universe. Our Milky Way galaxy is locked in a gravitational embrace with Andromeda and in a few billion years the two galaxies will collide, just one example of the power of gravity. It holds galaxies together over billions of kilometres.

Gravity is the weakest of the four forces, yet it is so influential. The four fundamental forces of nature are gravity, weak, strong and electromagnetic. Well gravity is by far the weakest, certainly it is very weak here on Earth, but out there in the universe it is quite different. Stand on a planet more massive than ours and you would quickly notice the immense power of gravity. Stand on a neutron star and you would be ripped apart very quickly.

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Newton realised that when objects fall to the Earth their must be a force acting on the object, reaching up and pulling it down. He stated that the force of gravity is always attractive, and affects everything with mass. Newton was also able to show that objects with different masses fall at the same rate because an object’s acceleration due to the force of gravity depends only on the mass of the object pulling it, such as a planet.

Newton’s cannon was a thought experiment that demonstrated his theory further. He imagined firing a cannon ball from the top of a mountain. Without the force of gravity acting on the cannon ball it would simply travel in a straight line. If gravity is present then the cannon ball’s path will depend on its speed. If it is slow moving it will fall down to the surface, if it is travelling fast enough it will go into orbit around the planet and if it reaches the escape velocity it will leave the orbit all togehter.

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Einstein has a different approach. Einstein says that gravity is not a force but rather a property of space-time geometry. Objects in space, such as planets around a star are all attempting to travel in a straight line through space but that the curvature of the fabric of space means objects are constantly falling towards the mass exerting gravity. Einstein says when you are falling around an object you have cancelled out gravity. Astronauts on the International Space Station are weightless because they are continuously falling to Earth. There is gravity where they are, they are travelling at a speed to stay in orbit around the Earth. The astronauts are continually falling to the Earth but they never reach it, that is why they’re weightless. Being weightless means you are in free fall. When you are in free fall you cancel out gravity. Einstein’s elevator thought experiment explains his theory in more detail, read about it here.

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Tidal forces are significant across our solar system. Here on Earth we experience tidal effects thanks to the moon. The Earth experiences two high tides, one on the side of the Earth closest to the moon as the moon pulls the water towards it and on the opposite side as the moon pulls the Earth away from it.

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An extreme case of tidal forces in the solar system is the heating of the moon Io around Jupiter. Jupiter is very massive so the effects on Io are huge,  Jupiter pulls Io inwards and the other moons away from Io pull it the other way, causing Io to distort in shape. This constant change results in lots of friction which in turn drives strong volcanic activity on the surface of Io. Io is the most volcanically active body in the solar system and its surface is constantly changing with large dark spots on the surface caused by collapsed volcanoes.

Our moon is also tidally locked, meaning we see the same side of the moon all the time. It spins once on its axis as long as it takes it to orbit the Earth once, so we always see the same face. The constant tugging from the Earth on the moon has caused this locking to happen.

So what is gravity?

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Can’t wait for week 3 – the outer planets.

Exploring the Heavens – Week 3

The topic for this week was ‘The Characteristics of the Solar System’. The main items covered were the formation of the solar system, the planets and other celestial bodies such as comets and asteroids.

Due to being ill this week I attended the Thursday class instead of my usual Tuesday class, but the format was exactly the same. Paul’s 3D presentation was fantastic as it put us right in the middle of the solar system and we could experience it from many different angles and points of view, which really helped in developing our understanding of how it all works.

One of the main themes throughout this course has been the ‘ecliptic’ – a plane on which all the planets sit and orbit the Sun. Our solar system consists of our star – the Sun – an object which dominates our neighbourhood, consisting of 99% of the mass and also gravitationally. The 8 planets and countless comets and asteroids all belong to the Sun. The unit by which we measure the distance of the planets from the Sun is called an astronomical unit, and the Earth is 1 AU from the Sun (approx. 150m km). It is possible that the distances of all the planets from the Sun can be explained with a mathematical formula that proves they are not just random distances.

A sidereal period is the time it takes a planet to orbit the sun. The further the planet from the Sun the greater the period. Kepler’s third law – the law of periods – found a simple relationship between the distance and the period. The ratio of the average distance from the Sun cubed to the period squared is the same constant value for all planets.

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His equation:

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Our best guess at how our solar system was formed is called the Solar Nebula theory. Any theory has to explain the characteristics of our system:

  1. The order of the orbits of planets
  2. The categories of planets – terrestrial and jovian
  3. The amount of comets and asteroids
  4. Anomalies

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  1. Our solar system formed from the gravitational collapse of a large cloud of gas and dust
  2. As the cloud collapses, conservation of energy, momentum and angular momentum flatten it out into a disk
  3. The diffuse clouds end up as a spinning disk of gas and dust with the young protosun at the middle
  4. The spinning disk is hotter at the centre and colder on the outside, so closer in are more material of rock and iron, further out more hydrogen compounds such as methane, explaining the makeup of our planets
  5. Finally the Sun ignites and releases a strong solar wind to clear away the remaining dust other material. We are left with the planets we have now

We talked about all of the planets and their characteristics. When we were outside looking up we could clearly see Jupiter and Mars on the ecliptic. The signs of the Zodiac pass through the ecliptic. This is a good way to find a planet!

The synodic period is the time it takes for a planet to return to the same angle with respect to the Sun. The synodic period for Mars is 780 days for it to move from opposition to opposition. Prior to opposition is when the planets move in retrograde motion.

We had an amazing view of the Moon tonight through a telescope on the balcony at the observatory. This was my first time viewing the Moon through a telescope and it looked amazing, we could see so much detail. I can only imagine the view from the Moon looking back at Earth.

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The Moon has a sidereal period (orbit) of 27.3 days and appears to go through its phases every 29.5 days (synodic period). The basis for our month. The phases of the Moon are due to the changing appearance relative to the Sun, however, we only ever see one side of the Moon as it has been locked in its orbit, due to the tidal effect from Earth.

The Moon is the major force behind tides on Earth. The gravity of the moon pulls the water  up towards it, creating an uneven distribution. The Earth and moon orbit a common centre of mass, located close to the surface of the Earth. As the Earth rotates on its axis each point on the surface is subjected to a sequence of high and low tides every 6 hours. These tides are also causing the moon to slowly drift further away from Earth at 3.7 cm per century.

Finally, we talked about eclipses, both solar and lunar. Paul said that we should all try to make it to a total solar eclipse, when the moon obscures the Sun. This happens when the 3 bodies are in exact alignment, which happens every 6 months or so. This phenomenon is possible because the Sun and Moon look the same size in the sky. The Sun is approx. 400x larger than the moon but is is 400x times further away, hence a total eclipse of the Sun is possible. Very few places on Earth will see a total eclipse due to the precision needed to make this happen.

Next week… The Stars!

Year 5, MARS & STEM in Term 1

What an awesome term of STEM we had in year 5! The main objectives were to learn about the planet Mars, space missions to Mars, the role of NASA and the Jet Propulsion Laboratory and the people that work there, discover if humans could live on Mars and what life would be like there.

So, lots of talk about lots of my favourite things: space, Mars, NASA/JPL, Adam Steltzner, The Martian, amazing technology, science and engineering, really inspiring stuff.

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As well as the main learning objectives I had planned at the start of the course, some extra opportunities arose to fit into the busy schedule to enhance the course further. March 14 was Pi Day and I planned a special lesson with help from a great resource I found from the NASA website called Planet Pi. I adapted the lesson slightly for year 5 and they coped with some new and tough maths admirably. This lesson highlighted how NASA scientists use Maths in their jobs to learn about planets and other celestial bodies. I explained the maths and formulae clearly and used some great visuals to help the girls understand the maths and why it was needed. I loved the example of using Pi to explore a planet, this was such a great lesson!

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Another great lesson we had this term, and which was a complete and unexpected surprise was the Skype with Andrea Boyd, an engineer with the European Space Agency. Andrea lives in Germany and was good enough to stay up late at night to speak to all of year 5 at 9am Sydney time. Andrea spoke about her education and career in the space industry, which was very interesting and inspiring for our young girls. Our students prepared some great questions to ask Andrea about space, the International Space Station, astronauts and more. Our girls did a great job, were beautifully behaved, very polite and engaged with this brilliant, young, Australian woman. We learnt so much about space and how astronauts live and work on the ISS. This was a really exciting lesson which everyone enjoyed! Big thanks go to Jackie Slaviero, founder of One Giant Leap Australia, for putting me in contact with Andrea and then for sending me an amazing pack of goodies from NASA.

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The students seemed to love our STEM lessons this term. Space is such an interesting, exciting and inspiring topic for young and old, and I was so pleased with how they engaged. I love the questions they ask, they are so curious and what to learn everything. As well as learning about Mars we learnt about black holes, the Earth and Moon, the ISS, the speed of light, galaxies and more. We could quite easily study space for the whole year, and I gladly would.

Next term… students continue their STEM journey to Mars when they work in engineering groups to design and build their own Mars rover, based on the Mars Science Laboratory (MSL), aka Curiosity. Curiosity has been a common theme throughout the term and I talked a lot about it when I talked about JPL engineer and EDL team leader for Curiosity, Adam Steltzner, a really inspiring speaker.

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His TED talk ‘How Curiosity changed my life, and I changed Hers’ is one of my favourites.

We also looked at rover facts and a great video called ‘7 minutes of terror’ which details how the rover made it from the top of the Mars atmosphere travelling at 30,000 mph to the surface travelling at a few mph in just 7 minutes. Another must-see video!

Like I said, I could teach this topic all year and not get bored! I used this video for an Edpuzzle.com which included some questions about the EDL of Curiosity. A great resource for incorporating video into classes.

Students produced some wonderful work including ‘Selling Mars: selling land on Mars’ advertisements and a ‘NASA profile’ of an inspiring NASA scientist they found from the website We Are The Martians.

So next term… engineering groups, specific roles for each girl in the group, designing and making a Mars rover, making wheels and incorporating LittleBits electronics to make the rover move, engineering guide with project milestones, evaluations, presentations, creativity, teamwork and fun!

Let’s hope ours will look better than this one!

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