Gravity

To start our unit we wrote down what we know about gravity and what we want to know. We used sticky notes and stuck them onto a piece of paper. Hopefully, we can answer all the questions on our list! There are some good ones.

**Galileo Experiment** Next, we did a famous experiment that Galileo did at the Leaning Tower of Pisa. We talked about how this is probably a Myth, and how the story probably changed over time. But, it is still a good example of a good experiment. We dropped two items at the same time, made a guess, and then recorded what we thought was the real result. Here is our data:

__**Conclusions and Observations**__ - There were many sames - Objects falled at the same rate - The only objects that were different were feathers and pieces of paper - Those objects have air resistance - air resistance makes something fall slower (air friction) - all items fall at the same speed because gravity's power is the same on each object - F=M*A (newtons second law) - Gravity's power is a Constant; F=9.8056m/s(squared)

**Gizmo's Free Fall Tower**

- A vacuum is a place with no air; Like space - The thing you drop will keep accelerating until they hit something - In a vacuum everything will fall at the same speed - The graphs is constant - We saw a video of Dave Scott Apollo 15 commander dropping a hammer and a feather on the Moon and they fell at the same time! Emi!
 * Activity A - Free Fall in a Vacuum**


 * Activity B - Air Resistance**

- In air, every object has a point which is called terminal velocity, where it stops accelerating, - When objects fall through the air, they are pushed by a force called air resistance - At about 15m, the ping pong ball’s speed becomes 9m per second - A golf ball falls faster than a soccer ball because the golf ball has more mass Koichi

Jiwon
 * Activity C - Parachutes**
 * Gravity and air controls an object that is falling
 * A parachute won’t work in vacuum because there is no air in vacuum. Parachute needs air to pull the parachute up
 * The heavier the object the faster it falls with the parachute

__**Space**__

We brought our investigation out to space. It is easier to see how gravity works when we see really big things moving! On Earth, things are too small (balls, feathers, Eiffel Towers) compared to the Earth. In space, we can see planets and stars moving with each other because the size difference is closer.

__**Scale**__ To get an idea of how small we are, and how big the Universe is, check out this link and play with it. It is very cool! []

__**Satellites**__ Why doesn't it fall to the Earth? Or drift into space?

Isha - a satellite doesn't crash to earth because the speed is just right. It stays on orbit around the Earth. If the speed changes, then the orbit will change. if the speed increases, then it will fly off into space. If it decreases, it will fall down to Earth. This is because the gravity of Earth is pulling, but the speed is fighting against it.



__**The Tides**__ Jiwon - In real life the, the Moon is orbiting the sun. The gravity of the moon and the sun pulls the oceans. During Neap Tide, the gravity of the sun and moon are kind of balanced and the tides are small. During Spring Tides, the gravity of the moon and sun are pulling together, which is why the tides are big.



__**The Planets**__ We looked at the orbits of the planets (which is very different from spinning or rotation). Each planet has an orbit around the sun, which is an oval (or ellipse). The planets that are closest to the sun move faster, because the pull of gravity is stronger. The planets closer to the sun make a trip around the sun in less time. Therefore, a year (one trip around the sun) is different on different planets.

Here are some cool websites to visit:

//Planet Comparison// [] //Orbits Animation// [] //Your age on other planets// []

//Our Age of Different Planets (rounded)//
 * **Planets** || **YearsOld** || **DaysOld** ||
 * Mercury || 50 || 75 ||
 * Venus || 19 || 18 ||
 * Earth || 12 || 4448 ||
 * Mars || 6 || 4318 ||
 * Jupiter || 1 || 10849 ||
 * Saturn || 0.4 || 9885 ||
 * Uranus || 0.14 || 6178 ||
 * Neptune || 0.07 || 6639 ||
 * Pluto || 0.04 || 696 ||


 * Koichi** - I am 1 year old on Jupiter. I am so young because Jupiter spins quite fast, but it is orbiting vvvvvery slow. This is because Jupiter is far from the sun, so it orbits very slowly. For example, you are going to run a 500km track and the other person is going to run a 1km track. Both are circles, but who would win? Of course the person on the 1km track! This like space. But, this is because gravity (from the sun) is pulling Jupiter, but Jupiter is resisting it slowly.

**Emi** - For a very massive object like a planet, its own gravity forces it into the most compact shape, a sphere. Diagrams showing them as spheres are simply showing them as they really are.(Planets are not perfect circles, they are more like eggs.) Since gravity pulls everything to the center with the highest mass it becomes a circle.
 * How does gravity affect the shape of a planet? Why a sphere? **

**How does gravity affect the material of the planet?**
 * Koichi and Satoki** - The terrestrial planets are made of iron, rocks, etc. so it's very heavy. The sun pulls the heavy planets like Earth closer and the gas planets farther. Do you know why? For example, you can try to pull a table. It's heavy, but you can still pull it. Now try to pull a calculator with the same power when you pulled! It is too easy to pull the calculator! Same with the sun, it is easier to pull the terrestrial planets, and more difficult to pull the gas planets. Therefore, the gas planets are far away and the terrestrial planets are closer.

**How does gravity affect the temperature of the planet?** **Jiwon/Isha** - The reason why we have seasons is because the earth and other planets are orbiting the sun, and the planets are spinning around themselves. There are two movements happening. Half of the planet is facing the sun and half of them are not facing the sun, so if the other side is facing the sun side that means its day. When it’s not facing the sun it means its night. Gravity is responsible for the planets temperature because the gravity is pulling the planets near the sun. The spinning is day and night and the orbiting around the sun is causing the seasons.

__ **Albert Einstein and Special Relativity** __



Check out our lesson on Special Relativity. It was very cool!

Everything we see is history []

Here are some more links to cool videos about Special and General Relativity: [] (the train thought experiment) [] (PBS documentary about Newton Vs. Einstein) [] (PBS documentary about Albert Einstein) [] (Einstein's thought experiments) [] (A video from Carl Sagan about Time Dilation and travelling at the speed of light) [] (Carl Sagan; Gravity is WonderLand)

__**Gravity Podcast**__

To synthesize our understanding of Gravity, we made an O Gravity Podcast. Isha wrote the words to the song, and then Mr Messano helped with the piano. We recorded our song and then each took a different topic and wrote an explanation of it. Listen!

media type="file" key="O Gravity Podcast.mp3" width="240" height="20" [|O Gravity Podcast.mp3]

**Gravity Abstract Painting** This was our final project to do with Gravity. We did Art, and we tried to show our own personal understanding of gravity through an abstract painting.