### The solar system and the universe

• #### Beam to Moon (Ratios and Proportions)

Apply ratios and proportions to find the weight of a person on the moon (or on another planet). Weigh an object on Earth and on the moon and weigh the person on Earth. Then set up and solve the proportion of the Earth weights to the moon weights.

• #### Beam to Moon (Ratios and Proportions)

Apply ratios and proportions to find the weight of a person on the moon (or on another planet). Weigh an object on Earth and on the moon and weigh the person on Earth. Then set up and solve the proportion of the Earth weights to the moon weights.

• #### Comparing Earth and Venus

Observe the motions of Venus and Earth as the planets move around the Sun. Measure the length of a day and a year on Earth and Venus, and compare the length of a solar day to the length of a sidereal day.

• #### Gravitational Force

Drag two objects around and observe the gravitational force between them as their positions change. The mass of each object can be adjusted, and the gravitational force is displayed both as vectors and numerically.

• #### H-R Diagram

A collection of stars visible from Earth can be arranged and classified based on their color, temperature, luminosity, radius, and mass. This can be done using one or two-dimensional plots, including a Hertzsprung-Russell diagram of luminosity vs. temperature.

• #### Orbital Motion - Kepler's Laws

Learn Kepler's three laws of planetary motion by examining the orbit of a planet around a star. The initial position, velocity, and mass of the planet can be varied as well as the mass of the star. The foci and centers of orbits can be displayed and compared to the location of the star. The area swept out by the planet in a given time period can be measured, and data on orbital radii and periods can be plotted in several ways.

• #### Solar System Explorer

Survey the solar system, observing the length of a year and the orbital path of each object. The positions of the eight official planets are displayed, as well as one dwarf planet, Pluto. Learn about Kepler's Laws and how planets are classified.

• #### Star Spectra

Analyze the spectra of a variety of stars. Determine the elements that are represented in each spectrum, and use this information to infer the temperature and classification of the star. Look for unusual features such as redshifted stars, nebulae, and stars with large planets.