Cosmology and the arrow of time: Sean Carroll at TEDxCaltech
TEDx Talks・14 minutes read
The Universe is vast, containing a hundred billion galaxies, each with a hundred billion stars, expanding over time with the mystery of low entropy at its beginning. The future involves cooling off, stars becoming black holes, and ultimately empty space lasting forever, raising questions about our existence in the early stages rather than in the vast expanse of time.
Insights
- The Milky Way Galaxy, with a hundred billion stars, is just one of approximately a hundred billion galaxies in the observable Universe, highlighting the vast scale and complexity of the cosmos.
- The mystery of the Universe's low entropy at the beginning, as explained by Ludwig Boltzmann's work on entropy and the second law of thermodynamics, challenges cosmologists to unravel the nature and future of the Universe, including the implications of dark energy theory and the eventual cooling off leading to an eternity of empty space.
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Recent questions
How many stars are in the Milky Way Galaxy?
About a hundred billion stars.
How many galaxies are in the observable Universe?
Approximately a hundred billion galaxies.
What is the second law of thermodynamics?
Entropy quantifies randomness in a system.
What does dark energy theory explain?
The Universe's acceleration and perpetual expansion.
What is Boltzmann's multiverse theory?
Life exists in regions with low entropy.
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Summary
00:00
"The Universe: A Billion Stars Mystery"
- The Milky Way Galaxy contains about a hundred billion stars.
- When pointing a camera attached to the Hubble Space Telescope at a random part of the sky, it captures galaxies similar in size to the Milky Way, each with a hundred billion stars.
- There are approximately a hundred billion galaxies in the observable Universe.
- The Universe is expanding, with galaxies moving away from each other over time.
- The early Universe was very smooth, despite being dense and hot near the Big Bang.
- Ludwig Boltzmann's work on entropy quantifies randomness and explains the second law of thermodynamics.
- The Universe's low entropy at the beginning poses a mystery that cosmologists aim to solve.
- Dark energy theory explains the Universe's acceleration and its perpetual expansion.
- Empty space has a temperature, leading to thermal fluctuations even in the eternal Universe.
- Boltzmann's multiverse theory suggests that life exists in regions with low entropy, where fluctuations occasionally create organized structures like galaxies.
12:35
Eternal Universe: Entropy, Black Holes, Finite Events
- The Universe is not a fluctuation, and the early Universe had low entropy, leading to questions about its nature and future.
- The future of the Universe involves the eventual cooling off, stars turning into black holes, and the Universe eventually being left with empty space that lasts forever.
- Despite the Universe lasting essentially forever, there are only a finite number of possible events that can occur over a period of time equal to 10 to the 10 to the 120 years, prompting questions about why we exist in the early stages rather than in empty space.
