Dark matter, dark energy; Unravelling cosmic mysteries | Vihaan Deshpande | TEDxRWA Youth

TL;DR

Dark matter keeps galaxies together, while dark energy drives the expansion of the universe.

Transcript

Transcriber: Tess Kayal Reviewer: Emma Gon Have you ever looked up to the night sky and thought about the countless things in the universe? I want you to think of all the planets, stars and even galaxies spread across the limitless cosmos. Can you believe that all that matter makes up just 5% of the total universe? And that the other 95% is made up... Read More

Key Insights

• 🕶️ Only 5% of the universe consists of visible matter, while the remaining 95% is made up of dark matter and dark energy.
• 🤩 Dark matter is crucial for galaxy stability, as it keeps stars in orbit around the galactic bulge.
• 👾 Dark energy powers the expansion of space, causing galaxies to move away from each other.
• 😃 The three possible scenarios for the fate of the universe are the Big Crunch, Big Freeze, and Big Rip.
• 🖐️ Dark energy, comprising 68% of the universe, plays a significant role in determining the most likely outcome for the future of the universe.
• 🕶️ Dark matter and dark energy are hidden gifts, as they have powerful impacts on the universe despite being unseen.
• 🕶️ The observation of rotation curves in galaxies provides evidence for the existence of dark matter.

Questions & Answers

Q: What is dark matter and why is it important?

Dark matter is a hidden mass that keeps galaxies together, comprising 27% of the universe. Its importance lies in stabilizing galaxies and preventing stars from being thrown out.

Q: How can dark energy help predict the universe's fate?

Dark energy, comprising around 68% of the universe, powers the expansion of space. It can lead to three possible scenarios: the Big Crunch, Big Freeze, or Big Rip, with the Big Freeze being the most likely outcome.

Q: How is dark matter different from dark energy?

Dark matter is invisible mass that holds galaxies together, while dark energy is a powerful force causing the expansion of space. They make up different proportions of the universe.

Q: Can dark matter and dark energy be observed or interacted with?

Both dark matter and dark energy cannot be seen or directly interacted with. They are invisible and hidden from sight.

Summary

In this video, Vihan Deshpande discusses the concept of dark matter and dark energy, and how they are essential in understanding the mysteries of the universe. He explains that dark matter is a hidden mass that keeps galaxies together, comprising 27% of the universe, while dark energy is a powerful force responsible for the expansion of space and makes up around 68% of the universe. They both play crucial roles in shaping the future of the universe.

Questions & Answers

Q: What is dark matter and why is it important?

Dark matter is an invisible mass that keeps galaxies together by exerting a gravitational force on stars within the galaxies. It is called "dark" because we cannot see or interact with it. Dark matter is essential as it comprises 27% of the total universe, playing a crucial role in maintaining the stability of galaxies.

Q: Why are the speeds of stars in galaxies different from what is predicted?

The speeds of stars in galaxies are evaluated using rotation curve graphs. According to the predicted speeds, stars closer to the center of the galaxy should be moving faster than those at the outer edges. However, the observed speeds of stars near the edge of galaxies are significantly higher than expected. This discrepancy suggests the presence of additional matter, known as dark matter, which exerts gravitational forces to keep the stars in place.

Q: How is dark matter represented in the analogy Vihan uses with the tennis balls?

In the analogy, the tennis balls represent stars near the edge of a galaxy, and Vihan represents the galaxy itself. When Vihan throws the tennis balls, it demonstrates how stars at the edge of the galaxy should be moving too fast and getting thrown out. However, since we observe stars staying in place in real galaxies, there must be additional mass, which we cannot see or interact with, keeping them there. This invisible mass is referred to as dark matter.

Q: What is dark energy and why is it significant?

Dark energy is a powerful force responsible for the expansion of space. It is the driving force behind the movement of galaxies away from each other. Dark energy comprises around 68% of the total universe. It is significant because it plays a crucial role in determining the future fate of the universe.

Q: How does dark energy affect the expansion of the universe?

Dark energy causes the expansion of space, which means that galaxies are moving away from each other at increasing speeds. It explains why the dots on Vihan's blown-up balloon (representing galaxies) are moving apart from each other. While the internal gravity within galaxies keeps them intact, the overall expansion of space occurs due to the powerful force of dark energy.

Q: What are the possible scenarios for the future of the universe, based on dark energy?

There are three possible scenarios for the future of the universe. The first is the Big Crunch, where gravity overcomes dark energy, resulting in the collapse of the universe into a single point called singularity. The second scenario is the Big Freeze, where the universe continues to expand, but at a slower rate, eventually reaching a state of heat death. The final and most unsettling scenario is the Big Rip, where dark energy dominates over gravity, leading to an accelerated expansion that rips apart planets, stars, galaxies, and even atoms. However, the most likely scenario is the Big Freeze, where the universe continues to expand without the ripping apart phenomenon.

Q: Why is dark energy important in predicting the fate of the universe?

Dark energy is crucial in predicting the fate of the universe because it determines the expansion rate of space. Depending on the balance between dark energy and gravity, different scenarios can occur, such as the Big Crunch, Big Freeze, or Big Rip. Understanding the role of dark energy helps scientists anticipate what is likely to happen in the future and how the universe will evolve.

Q: When is the Big Freeze expected to occur?

The scenario of the Big Freeze, where the universe continues to expand without ripping apart, is the most likely outcome for the future. However, it is not predicted to happen for billions of years, so there is no immediate need to worry about the eventual cold and dark fate of the universe.

Takeaways

Understanding the concepts of dark matter and dark energy is crucial in unraveling the mysteries of the universe. Dark matter is an invisible mass that keeps galaxies together, while dark energy is a powerful force driving the expansion of space. Dark matter comprises 27% of the universe, and dark energy accounts for 68%. These hidden gifts play a significant role in shaping the future of the universe. The most likely scenario is the Big Freeze, where the universe continues to expand without tearing apart for billions of years. Despite being unseen, dark matter and dark energy have powerful impacts on our universe, making them important subjects of study and exploration.

Summary & Key Takeaways

• Dark matter is an invisible mass that comprises 27% of the universe, keeping galaxies stable and preventing stars from being thrown out.

• Dark energy is a powerful force that makes up around 68% of the universe, causing the expansion of space and potentially determining the fate of the universe.

• The future scenarios for the universe include the Big Crunch, Big Freeze, and Big Rip, with the Big Freeze being the most likely outcome.