Dark energy and dark matter are two mysterious parts of our universe that play important roles in how it expands. Let’s make this easier to understand:

Dark Matter

• What is it? Dark matter makes up about 27% of the universe. Unlike regular matter, dark matter doesn’t give off or take in light, so we can’t see it.
• How does it work? Think of dark matter as a kind of cosmic glue. It helps hold galaxies together. The gravitational pull from dark matter helps galaxies form and group together in the way we see them today.

Dark Energy

• What is it? Dark energy makes up about 68% of the universe. It’s believed to be a type of energy that spreads throughout all of space and is causing the universe to expand faster.
• Cosmological Constant: The famous scientist Einstein talked about something called a "cosmological constant" in his equations. Many scientists think that dark energy is related to this idea.

Expansion of the Universe

• Getting Faster: Scientists have looked at distant supernovae and cosmic microwave background radiation and found that the universe isn’t just getting bigger; it’s expanding even faster because of dark energy.
• Math to Explain It: There’s a math relationship that shows this idea using equations called Friedmann equations. One of these equations looks like this:

$$H^2 = \frac{8\pi G}{3} \rho - \frac{k}{a^2} + \frac{\Lambda}{3}$$

In this equation:

• $H$ is the Hubble parameter (how fast the universe is expanding),
• $\rho$ is about how much matter there is,
• $k$ means the shape of space,
• $\Lambda$ is the cosmological constant that relates to dark energy.

In Summary

Dark matter helps to create structures in the universe, while dark energy helps it to expand. Both are important for us to understand how our universe works.