What is Dark Energy and what does it have to do with Einstein?

TL;DR

Observations of distant supernovae revealed that the expansion of the universe is not slowing down, but rather speeding up due to the presence of dark energy.

Transcript

in 1998 the community of physicists received a shock the shock is two teams of astronomers had figured out through observations of distant supernovae that the expansion of the universe which everybody knew about since Hubble in 1929 that the expansion of the universe was not slowing down as everybody expected but it was speeding up it was going fas... Read More

Key Insights

• ⏮️ Observations of distant supernovae revealed that the expansion of the universe is accelerating, contrary to previous expectations.
• 👾 The presence of dark energy, a diffuse energy that fills space, is responsible for the accelerated expansion.
• 🪡 Albert Einstein's discarded concept, the cosmological constant, is now needed to explain the accelerated expansion.
• 🫷 Dark energy produces a repulsive version of gravity, pushing galaxies apart.
• ⚾ The accelerated expansion of the universe challenges common intuitions based on gravity.
• ↩️ Einstein's "greatest blunder" turned out to be a necessary concept for understanding the universe.
• 🕶️ The discovery of dark energy highlights the complexity and mystery of the universe.

Questions & Answers

Q: Why did people initially expect the expansion of the universe to slow down?

The common belief was that the mutual gravitational attraction between galaxies would gradually slow down the expansion over time, similar to how Earth's gravity slows down a thrown apple.

Q: How did observations of distant supernovae challenge this belief?

Astronomers found that the galaxies were actually moving away from each other faster and faster over time, indicating an accelerated expansion.

Q: How does dark energy explain the accelerated expansion?

Dark energy, according to Einstein's general theory of relativity, creates a repulsive version of gravity that pushes galaxies apart, causing the accelerated expansion.

Q: Why did Einstein introduce the cosmological constant in 1917?

Initially, Einstein introduced the cosmological constant as a counteracting force to the attractive pull of gravity, aiming for a static universe. He was unaware of the expansion of space at that time.

Summary & Key Takeaways

• In 1998, astronomers discovered that the expansion of the universe was accelerating, contrary to previous expectations.

• This acceleration is attributed to the presence of dark energy, a diffuse energy that fills space and produces a repulsive version of gravity.

• Albert Einstein had introduced a similar concept called the cosmological constant in 1917, but discarded it as a mistake. However, its reintroduction became necessary to explain the accelerated expansion.