Brian Greene and Adam Riess: The Accelerating Universe
World Science Festival・148 minutes read
World Science Festival hosts sessions with experts discussing breakthroughs in physics and cosmology, featuring Nobel laureate Adam Reese. Recent news includes experiments on dark matter, the universe's acceleration, and hot water freezing faster than cold water. The text delves into Einstein's theories, the expanding universe concept, Hubble's observations, and the discovery of the universe's acceleration, emphasizing the importance of persistence and precision in scientific discoveries.
Insights
- Einstein's cosmological constant aimed to maintain a static universe against the force of matter, creating a repulsive force countering gravity.
- Observations of cosmic microwave background radiation confirmed the universe's acceleration, challenging existing beliefs and theories.
- String theory proposes extra dimensions beyond everyday experience, potentially explaining dark energy as energy in unseen dimensions.
- The unification of gravity and electromagnetism in classical physics is possible through the least action principle.
- The brain forming in space from random particle motions, as in the Boltzmann brain hypothesis, raises skepticism about reality and theories like general relativity.
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Recent questions
What is the cosmological constant in physics?
The cosmological constant, also known as vacuum energy, is a term introduced by Albert Einstein to maintain a static universe against the attractive force of matter. It creates a repulsive force countering gravity's pull, allowing for a static universe. This concept has evolved to include dark energy, responsible for the acceleration of the universe's expansion, posing challenges due to its extremely small value.
How did Edwin Hubble's observations impact cosmology?
Edwin Hubble's observations in 1929 led to the realization that the universe was expanding, challenging previous beliefs in a steady-state model. This discovery prompted Einstein to acknowledge his error in introducing a cosmological term. The concept of the expanding universe contradicted the steady-state theory and supported the idea of a singularity and infinite space, raising questions about the universe's origin and expansion.
What is the significance of the discovery of dark energy?
The discovery of dark energy, responsible for the acceleration of the universe's expansion, led to a paradigm shift in cosmology. It challenged established theories and models, raising fundamental questions about the universe's structure and the nature of dark energy. Multiple independent methods, including observing supernovae, were used to confirm the acceleration, highlighting the importance of meticulous verification in scientific breakthroughs.
How did Saul Perlmutter's team contribute to cosmology?
Saul Perlmutter's team independently conducted experiments in 1998, discovering the acceleration of the universe's expansion. This unexpected finding, along with another team's results, led to a competitive environment driving the presentation of their findings at conferences. Despite initial skepticism, the alignment of results with existing knowledge eventually overcame backlash, solidifying the understanding of the universe's acceleration.
What is the role of string theory in physics?
String theory aims to unify quantum mechanics and gravity through vibrating strings, setting a minimum size for undulations in space fabric. It presents potential explanations for dark energy, linking it to energy in extra dimensions. While facing challenges in fully realizing its ideas, string theory has made progress in addressing long-standing questions and understanding black hole descriptions, offering a unique path to a quantum description of gravity.
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