This module explores the vastness of the universe, the forces that govern celestial bodies, and the way objects move in space. Understanding the correct units is crucial for describing and calculating astronomical phenomena.
Explore the cosmos through interactive simulations. Learn about gravity, orbits, and the structure of our universe.
This module explores the vastness of the universe, the forces that govern celestial bodies, and the way objects move in space. Understanding the correct units is crucial for describing and calculating astronomical phenomena.
The universe encompasses everything we know: all of space, time, matter, and energy. It is organised in a hierarchical structure:
Hover over planets for details. Drag to rotate view. Sizes and distances are not to scale — they are adjusted so you can see all planets.
Gravitational field strength (symbol g) measures the gravitational force per unit mass at a point. On Earth, g ≈ 9.8 N/kg.
The value of g depends on:
| Celestial Body | g (N/kg) | Compared to Earth |
|---|---|---|
| Earth | 9.8 | 1 (Reference) |
| Moon | 1.6 | About 1/6th |
| Mars | 3.7 | About 38% |
| Jupiter | 24.8 | About 2.5x |
| Venus | 8.9 | About 91% |
| Pluto | 0.6 | About 6% |
Your weight (W = m × g) changes on different planets, but your mass (amount of matter) stays the same.
Watch how the same ball falls at different rates depending on gravitational field strength. The stronger the gravity, the faster the ball accelerates.
Gravitational force is the fundamental attraction between any two objects with mass. It provides the centripetal force needed for orbital motion. Without gravity, objects would travel in straight lines.
Drag the eccentricity slider from 0 (circular, like planets) to 0.95 (highly elliptical, like comets). Notice how the orbiting body speeds up near the star and slows down far away — this is Kepler's Second Law in action!
For an object in a circular orbit, its speed is determined by the orbit's radius and how long one full orbit takes:
The Moon orbits Earth at an average radius of 384,000 km. Its orbital period is 27.3 days.
1. Convert: r = 3.84 × 10&sup8; m | T = 27.3 × 24 × 3600 = 2.36 × 10&sup6; s
2. v = (2 × π × 3.84 × 10&sup8;) / (2.36 × 10&sup6;) ≈ 1,022 m/s (≈ 1.02 km/s)
1. Our solar system is located within which galaxy?
2. If an astronaut has a mass of 70 kg on Earth, what is their mass on the Moon (g ≈ 1.6 N/kg)?
3. What is the primary reason comets have highly elliptical orbits?
4. A planet's orbital period decreases but its radius stays the same. What happens to its speed?
5. Jupiter's g is about 24.8 N/kg vs Earth's 9.8 N/kg. This is primarily because:
6. Which best describes the shape of most planetary orbits around the Sun?
7. A satellite orbits Earth at radius 7,000 km with a period of 97 minutes. What is its approximate orbital speed?