How to learn everything from nothingness | Alice Pisani | TEDxRoma

Key Concepts:

• Cosmology
• Cosmic Web
• Dark Energy
• Accelerated Expansion of the Universe
• Cosmic Voids
• Dark Matter
• General Relativity
• Galaxy Surveys

1. Introduction: The Quest to Understand the Universe

• The speaker discusses the ambitious goal of cosmology: to understand the universe's formation, composition (past and present), and future evolution.
• The vastness of space and time scales involved are emphasized, highlighting the challenge of studying the universe.
• Looking at light from distant stars and galaxies is described as looking back in time, using light as a "time machine."

2. The Cosmic Web and Galaxy Distribution

• Galaxies are described as massive collections of stars, forming a "huge star family."
• The universe is populated by hundreds of billions of galaxies arranged in a "Cosmic Web."
• The Cosmic Web acts as a skeleton where galaxies form.
• Modern data allows us to map the Cosmic Web and study the universe's evolution.

3. The Mystery of Dark Energy and Accelerated Expansion

• The universe is expanding, and surprisingly, this expansion is accelerating.
• This accelerated expansion is attributed to a mysterious component called "Dark Energy."
• Dark Energy is a placeholder for our ignorance, as its nature is unknown.
• It is hypothesized that Dark Energy stretches space, pushing galaxies farther apart.
• Alternative explanations for the accelerated expansion include modifications to the laws of general relativity.

4. Observational Efforts to Study Dark Energy

• Space missions (e.g., Euclid satellite, Nancy Grace Roman telescope) and ground telescopes (e.g., DESI survey, Vera Rubin Observatory) are being built to study Dark Energy.
• These telescopes are used to create maps of galaxies and study the universe's expansion and composition.

5. Shifting Focus to Cosmic Voids

• The speaker's research focuses on the "less luminous patches" and "dark spaces" between galaxies, known as Cosmic Voids.
• The idea is that sometimes, looking away from areas with a lot of information (galaxies) can reveal more about the universe.
• Cosmic Voids are described as "gigantic holes in the cosmic web" where very few galaxies reside.

6. The Rationale for Studying Cosmic Voids

• The widely accepted cosmological model states that the universe is composed of:
  • 5% ordinary matter
  • 26% dark matter
  • 69% dark energy
• Dark matter forms the skeleton for galaxies, so to understand Dark Energy, we need to look away from Dark Matter and galaxies.
• Cosmic Voids are dominated by Dark Energy, making them ideal locations to study it.
• Studying voids can also help determine if the laws of general relativity need to be modified.

7. Methodology: Counting and Measuring Cosmic Voids

• The number and sizes of voids depend on Dark Energy and when it started accelerating the universe's expansion.
• Dark Energy stretches space, making voids emptier, darker, and larger.
• By counting voids and measuring their sizes, we can determine when Dark Energy's effect began and if it changes over time.
• The composition and shape of voids are also linked to how they are observed in modern surveys.
• The process involves mapping the cosmic web, identifying voids, and studying their shapes and evolution.

8. The Timeliness of Void Research

• Only recently have telescopes become sensitive and powerful enough to explore large volumes of the sky and study voids in detail.
• Voids are described as a "true gold mine of information" that has been neglected.
• They offer novel information and go beyond traditional methods of analyzing galaxy distribution.

9. Overcoming Skepticism and Building a Research Community

• The speaker faced skepticism from other researchers regarding the use of voids to study Dark Energy.
• The speaker and collaborators persisted, convinced others to work together, and built a research community.
• The field has grown from a few researchers to over 100 worldwide.

10. Results and Future Prospects

• Over 6,000 voids have been discovered.
• Measurements from voids have allowed us to measure the amount of Dark Energy in the universe to the percent level, independently from other probes.
• The number of voids is expected to grow significantly in the coming years.
• Studying these "dark energy-dominated pockets" will help unveil the mystery of Dark Energy and its time evolution.

11. Conclusion: The Power of Looking in Unexpected Places

• Studying Cosmic Voids is a reminder that the best ideas can come from looking in quiet, dark, and unexpected places.
• By focusing on areas that others have overlooked, we can unlock the mysteries of the universe.

Notable Quotes:

• "Dark energy is only a placeholder for our ignorance as we have no clue about what it is."
• "Looking for emptiness is not looking for nothing it is looking where we should look now."

Technical Terms:

• Cosmology: The study of the origin, evolution, and structure of the universe.
• Cosmic Web: The large-scale structure of the universe, consisting of interconnected filaments and voids.
• Dark Energy: A mysterious form of energy that is thought to be responsible for the accelerated expansion of the universe.
• Accelerated Expansion: The increasing rate at which the universe is expanding.
• Cosmic Voids: Large, empty regions in the universe with very few galaxies.
• Dark Matter: A hypothetical form of matter that does not interact with light, but can be detected through its gravitational effects.
• General Relativity: Einstein's theory of gravity, which describes gravity as a curvature of spacetime.
• Galaxy Surveys: Systematic observations of galaxies to map their distribution and properties.