## What does the Friedmann equation tell us?

“The first Friedmann equation describes how, based on what is in the universe, its expansion rate will change over time. If you want to know where the Universe came from and where it’s headed, all you need to measure is how it is expanding today and what is in it. This equation allows you to predict the rest!”

### What assumptions did Friedmann make while solving Einstein’s equations for general relativity?

Friedmann and Lemaître adopted Einstein’s assumption of spatial homogeneity and isotropy (the cosmological principle). They rejected, however, his assumption of time independence and considered both positively curved spaces (“closed” universes) as well as negatively curved spaces (“open” universes).

#### How is the Friedmann equation used to determine the age of the universe?

The Friedmann equation includes the Hubble constant to give a much more accurate age of the universe. In this equation, G is the gravitational constant = 6.67*10-11Nm2/kg2, ρr is the radiation density of the universe, ρm is the matter density of the universe, and ρd is the dark energy density of the universe.

**What is the equation for the expansion of the universe?**

we associate electromagnetism, Newtonian gravitation, special relativity and quantum physics. The formula toc=h/moc expresses the electro-gravitational field bound to M2VP . Protons ( M2VP ) represent the stable particles of matter of the expanding universe. They move in every given direction at a speed less than c.

**What is the most famous equation ever?**

Einstein’s E=mc² is the world’s most famous equation. Simple as that. It is short, it is elegant, and it describes a phenomenon so crucial that everyone should know about it.

## What is the most important theorem in the universe?

The Pythagorean Theorem is arguably the most famous statement in mathematics, and the fourth most beautiful equation.

### What is the greatest equation?

What is the longest equation in the world? According to Sciencealert, the longest math equation contains around 200 terabytes of text. Called the Boolean Pythagorean Triples problem, it was first proposed by California-based mathematician Ronald Graham, back in the 1980s.

#### Is our universe de Sitter?

Within these theories, we find the conditions for the existence of a de Sitter critical point in a universe filled by matter, radiation and a Horndeski scalar. Therefore, if a de Sitter fixed point exists within these models, our Universe will eventually evolve into a de Sitter space.

**What is the density of matter in the universe?**

The expansion rate we see today indicates that the critical density of the Universe is about 9×10-27 kg m-3. This density, however, is the total density of both matter and energy.

**How to simplify the Friedmann equation in physics?**

We are free to simplify this term by introducing a new space-time constant that we will call − k so the Friedmann equation becomes: (11.1) ( a ˙ a) 2 = 8 π G ρ 3 − k a 2. In general relativity this constant, k, is the same as the curvature constant in the FRW invariant distance equation.

## How are the Friedmann equations of gravitation derived?

Friedmann equations. They were first derived by Alexander Friedmann in 1922 from Einstein’s field equations of gravitation for the Friedmann–Lemaître–Robertson–Walker metric and a perfect fluid with a given mass density and pressure . The equations for negative spatial curvature were given by Friedmann in 1924.

### How is the Friedmann equation related to Hubble’s law?

Assume the universe is filled with a fluid with mass density ρ, that is flowing in a manner consistent with Hubble’s law. Consider a test particle of mass m a distance a ( t) ℓ away from the origin of the coordinate system, that moves along with the fluid; i.e., all of its motion relative to the origin is due to the changing of the scale factor.

#### Which is the density parameter in the Friedmann equation?

The density parameter, Ω {\\displaystyle \\Omega } , is defined as the ratio of the actual (or observed) density ρ {\\displaystyle \\rho } to the critical density ρ c {\\displaystyle \\rho _{c}} of the Friedmann universe.