Measurement

1. We can tell how far away a celestial object is by looking at its size in the sky.

We can't tell how far away a celestial object is just by looking at it. Large objects that are far away will appear small, and small objects that are close to Earth can appear large. The Sun and Moon appear to be about the same size in our sky. In reality, the more-distant Sun is much bigger than the Moon.

2. Weight and mass are the same.

Weight and mass are not the same. Mass is a measure of a body's resistance to changes in its state of motion, which depends on the amount of matter it contains. Weight is the force of gravity exerted on a body due to its mass and its location near another, more massive object. A person can be weightless but cannot be without mass.