Explore the Kepler's Laws of Planetary Motion
Change orbit size and shape, see equal-area sectors and check the period–distance law. Free, no signup, runs in your browser.
- Free to use
- No signup
- Nothing to install
- Runs in your browser
Illustration. Open the tool for the real thing.
See it in action
The Kepler's Laws of Planetary Motion with sample data entered and the result showing.
What is the Kepler's Laws of Planetary Motion?
Change orbit size and shape, see equal-area sectors and check the period–distance law. It runs in your browser, so a change to a setting or a drag on an object shows up at once.
Kepler's laws are still used to plan satellite orbits and find exoplanets.
3 steps to your result
Open the tool and follow along. Nothing to install.
What you get
Orbits are ellipses with the star at one focus.
A line to the star sweeps equal areas in equal times.
T² is proportional to a³.
Set e = 0.9 and watch the speed.
Double a and check the period.
Turn on equal areas.
Used for
Pick one to see how it fits.
Earth & Space learners
Astronomy and earth-science students, and teachers who need a visual model to explain what is happening in the sky.
Try it freeTeachers
For teachers: project the Kepler's Laws of Planetary Motion on the board, let students predict the result, then run it together and test this: Double a and check the period. For students: change one thing at a time and write down what changes.
Try it freeHow it compares
A plain look at this tool next to the usual alternative.
| This simulation | Textbook diagram | |
|---|---|---|
| Interactive | Drag, tap and change settings | Fixed picture |
| Install | Nothing to install | Not needed |
| Cost | Free to use | Depends on the book |
Questions people ask
What is Kepler's second law?
The line from the star to the planet sweeps out equal areas in equal times, so the planet speeds up near the star.
What is eccentricity?
A number from 0 (circle) to 1 that says how stretched an ellipse is.
Is the Kepler's Laws of Planetary Motion free to use?
Yes. The Kepler's Laws of Planetary Motion is free, needs no signup or download and runs in your web browser. It is part of the Earth & Space group of AZRS simulations.
Does the Kepler's Laws of Planetary Motion work on a phone or tablet?
Yes. The Kepler's Laws of Planetary Motion takes touch input as well as mouse input, so you can use its 8 adjustable settings with a finger. A larger screen makes the controls and graphs easier to read.
How do I use the Kepler's Laws of Planetary Motion?
1. In the Kepler's Laws of Planetary Motion, use the controls to change Law, Semi-major axis a, Eccentricity e, Star mass, Number of period divisions, and more. The simulation reacts instantly. 2. In the Kepler's Laws of Planetary Motion, pick an option such as Full lab, 1st law: ellipse, 2nd law: equal areas, 3rd law: T² ∝ a³ to switch modes or load an example. 3. In the Kepler's Laws of Planetary Motion, press "Restart orbit", "Clear path" to start, reset or change what is happening. 4. Start with this experiment: Set e = 0.9 and watch the speed. Drag any glowing handle, object or slider with your mouse or finger and the Kepler's Laws of Planetary Motion responds in real time. 5. Change one setting at a time and watch which readout moves, then compare it with this idea: Orbits are ellipses with the star at one focus.
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Try the Kepler's Laws of Planetary Motion now
Change orbit size and shape, see equal-area sectors and check the period–distance law. Free to use.
Try it free