What about the speed of an electron? How fast does it go?

The speed of an electron depends on several factors, such as its energy level, its electric field, its magnetic field, and its interaction with other particles. There is no simple answer to this question, but I can give you some examples.

One example is the speed of an electron in an atom. An atom consists of a nucleus surrounded by electrons orbiting around it in different shells or levels. Each level has a certain energy associated with it. The higher the energy level, the faster the electron moves. The lowest energy level, called the ground state, has an electron speed of about 2,200 kilometers per second. That's about 7,000 times faster than a car on a highway.

The highest energy level, called the ionization energy, is the energy required to remove an electron from the atom completely. This depends on the type of atom, but for hydrogen, the simplest atom, it is about 13.6 electron volts. This corresponds to an electron speed of about 3,600 kilometers per second. That's about 11,000 times faster than a car on a highway.

What if the electron is not in an atom? What if it's free?

Another example is the speed of an electron in a vacuum. A vacuum is a space with no matter or radiation in it. In a vacuum, an electron can move at any speed, depending on its energy. The higher the energy, the faster it moves. But there is a limit to how fast it can go. It can never exceed the speed of light in a vacuum, which is about 300,000 kilometers per second. That's about 1 billion times faster than a car on a highway.

How can an electron have any energy in a vacuum? Where does it come from?

One way to give an electron energy in a vacuum is to accelerate it with an electric field. An electric field is a force that acts on charged particles, like electrons and protons. By applying a voltage difference between two points in a vacuum, we can create an electric field that pushes or pulls the electrons towards one point or another. The greater the voltage difference, the greater the electric field, and the greater the acceleration of the electrons.

For example, in a cathode ray tube, which is an old type of television or computer monitor, electrons are emitted from a metal filament and accelerated by a high voltage towards a phosphor screen. The electrons hit the screen and produce light and images. The voltage applied to the cathode ray tube can be up to 30 kilovolts, which gives the electrons an energy of about 30 kiloelectron volts. This corresponds to an electron speed of about 280,000 kilometers per second. That's about 93% of the speed of light in a vacuum.

You can apply more voltage and give them more energy, but you can't make them go faster than the speed of light in a vacuum. That's because as they approach the speed of light, their mass increases and their length contracts according to Einstein's theory of relativity. This makes them harder to accelerate and requires more energy to do so. As they get closer and closer to the speed of light, their mass approaches infinity and their length approaches zero. To reach the speed of light exactly, they would need infinite energy and have zero length. This is impossible.

Nothing with mass can go faster than the speed of light in a vacuum. But there are some things that have no mass, like photons or light particles. They always travel at the speed of light in a vacuum, regardless of their energy or frequency or wavelength or color. Photons are faster than electrons in a vacuum. But not necessarily in other media, like air or water or glass. In these media, photons slow down due to their interaction with atoms and molecules. Electrons can also slow down due to their interaction with atoms and molecules or other electrons or magnetic fields or radiation.

Who wins in a race between photons and electrons?

It depends on where they are racing and how they are racing and what kind of photons and electrons they are racing with. There is no simple answer to this question either.