Edwin Hubble, an American astronomer, made observations in the 1920s that led to the discovery of the expanding universe.

Hubble's Law states that the farther away a galaxy is, the faster it is moving away from us. This relationship is expressed mathematically as v = H0 * d, where v is the velocity of the galaxy, H0 is the Hubble constant, and d is the distance to the galaxy.

The Hubble constant is a measure of the expansion rate of the universe. It is currently estimated to be around 70 kilometers per second per megaparsec (km/s/Mpc). This means that for every megaparsec (3.26 million light-years) of distance between two galaxies, they are moving away from each other at a speed of 70 kilometers per second.

The Big Bang theory is the prevailing cosmological model for the universe from the earliest known periods through its present expansion and cooling. It is based on the observation that the universe is expanding and that the cosmic microwave background radiation is extraordinarily uniform.

The fate of the universe depends on the amount of matter and energy in it. If the universe contains enough matter, it will eventually stop expanding and begin to contract. However, if the universe contains too little matter, it will continue to expand forever.

The cosmic microwave background radiation (CMB) is the leftover radiation from the Big Bang, the event that is thought to have created the universe. The CMB is a faint glow of light that fills the entire universe and is a key piece of evidence for the Big Bang theory.

Dark energy is a mysterious force that is causing the universe to expand at an accelerating rate. It is one of the greatest mysteries in physics and is the subject of much research.

Dark matter is a type of matter that is invisible to telescopes. It is thought to make up about 27% of the universe, while ordinary matter makes up only about 5%.

The cosmological constant is a constant that is added to the equations of general relativity to account for dark energy. It is a very small number, but it has a significant impact on the expansion of the universe.

The shape of the universe is a subject of ongoing research. However, the current best estimate is that the universe is flat.

The age of the universe is estimated to be around 13.8 billion years.

The size of the universe is unknown, but it is thought to be infinite.

The future of the universe depends on the amount of matter and energy in it. If the universe contains enough matter, it will eventually stop expanding and begin to contract. However, if the universe contains too little matter, it will continue to expand forever.

The multiverse is a theory that there are many universes. There is no scientific evidence to support this theory, but it is a popular topic in science fiction and philosophy.

The anthropic principle is the principle that the universe is fine-tuned for life. This means that the universe has the right conditions for life to exist, even though the odds of this happening are very low.