A femtometer (fm), also known as a fermi, is an extremely tiny unit of measurement used to express even smaller distances than a picometer. It is equal to one quadrillionth of a meter, which is 0.000000000000001 meters or 1 × 10^-15 meters. The prefix "femto" denotes a factor of 10^-15 in the International System of Units (SI).
Femtometers are typically used in the field of nuclear physics and particle physics to describe the sizes and distances involved in atomic nuclei and subatomic particles. The nucleus of an atom, for example, is on the order of a few femtometers in diameter. In high-energy physics experiments and discussions about fundamental particles like protons, neutrons, and quarks, femtometers are a relevant unit of measurement due to the incredibly small scales involved.
The average distance from Earth to the Sun is about 149.6 million kilometers (or approximately 93 million miles). This distance is often referred to as an astronomical unit (AU), which is a standard unit of measurement used in astronomy to describe distances within our solar system. An astronomical unit is defined as the average distance between the Earth and the Sun.
It's important to note that the Earth's orbit around the Sun is not a perfect circle but rather an ellipse, so the distance between Earth and the Sun varies slightly throughout the year. The value given here represents the average distance. The closest point in Earth's orbit to the Sun is called perihelion, while the farthest point is called aphelion. Perihelion occurs around early January, and aphelion occurs around early July. At perihelion, Earth is approximately 147.1 million kilometers (about 91.4 million miles) from the Sun, while at aphelion, it is about 152.1 million kilometers (around 94.5 million miles) away.