# Orbit Gravity

High\-school gravitation and orbital motion in a mission\-control room: Newton's law of gravitation, Newton's cannon, circular orbit speed, higher\-is\-slower and orbit transfers

By Numa

Topic: Space

[Open the interactive Jig](https://ask.jig.com/j/mcIkrVq09mkl)

## Transcript

### 1. Falling Around the World

The International Space Station is falling right now\. Gravity up there is still 88% as strong as on the ground\. But the station moves so fast that Earth's surface curves away as quickly as it drops, so it falls around the world every 93 minutes\.

The hologram runs 900 times faster than real time\. Drag outside it to look around\.

### 2. Gravity Pulls to the Centre

Let go of a probe and it falls straight toward Earth's centre, from any direction\. The orange arrow shows gravity's pull, which is four times stronger at half the distance\. Drag the probe around its ring and let go, or press Drop\.

### 3. Newton's Cannon

Isaac Newton imagined a cannon on a mountain above the air\. Each faster shot lands farther around the Earth\. At about 6\.9 km/s, the ground curves away as fast as the ball falls, and it never lands\. Set a speed and press Fire, or click the cannon\.

The mountain is drawn far taller than any real peak\.

### 4. An Orbit Is a Fall

Without gravity, the probe would coast off along the dashed line\. Gravity pulls it in by the orange gap, so it falls around Earth instead\. The heavy station gets pulled much harder but accelerates just the same, so the two fly side by side\.

Orbital speed depends on height, not on mass\.

### 5. Higher Is Slower

Gravity is weaker farther from Earth, so a higher orbit is slower\. The ISS flies low at 7\.66 km/s and laps Earth every 93 minutes\. GPS satellites fly much higher at 3\.87 km/s and take about 12 hours\. Count the laps\.

### 6. Fling a Satellite

Grab the satellite, pull back like a slingshot and let go\. A longer pull means a faster launch\. Too slow and it burns up in the air\. Too fast and it escapes Earth for good\. In between, it falls around the planet in an orbit\.

Your last three paths stay on the display so you can compare\.

### 7. Mission: Hold the Band

Put a satellite in an orbit that stays inside the green band for a full lap\. Launch it sideways, at right angles to gravity's pull, at about 5\.6 km/s\. That's the speed for a circular orbit at this height\.

### 8. Raise the Orbit

To climb, a satellite fires its engine in short burns\. Grab it as it circles, drag forward along its path and let go to fire\. The dashed path previews the new orbit\. Raise the high point to the gold ring, then burn again at the top to round it off\.