Roger Penrose: Infinite Cycles of the Universe Punctuated by Big Bang Singularities | Summary and Q&A

April 1, 2020
Lex Fridman
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Roger Penrose: Infinite Cycles of the Universe Punctuated by Big Bang Singularities


The universe will go through exponential expansion, followed by the domination of black holes, and eventually reach a state of infinite coldness where only photons exist.

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Key Insights

  • 🌌 The universe is undergoing exponential expansion, driven by the cosmological constant. This expansion will make the universe increasingly boring in the future.
  • ⚫ Black holes play a significant role in the universe and will eventually engulf entire clusters of galaxies.
  • 🌬️ Eventually, black holes will evaporate, leaving behind a cold and empty universe.
  • 🌀 Infinity is a mathematical concept that can be seen as a boundary in different geometries. Photons can reach infinity as another place due to the principles of relativity.
  • 🕰️ Time can be measured precisely with clocks, which are equivalent to mass and frequency. Without mass, there are no clocks or space-time measurements.
  • 🌌 The remote future and the Big Bang appear different, but conformal scaling suggests they are nearly the same. Photons may even traverse between the two.
  • 🔭 Signals from previous eons, such as gravitational waves from black hole collisions, can reach the present eon, potentially allowing communication across different eons.
  • 👾 The Fermi paradox suggests that we may not have heard from extraterrestrial civilizations because we do not know how to look or interpret the signals they may be sending. However, looking for signals from successful civilizations that have overcome their challenges could be a new approach.


but word is the conformal cyclic cosmology of yeah we're starting to talk about something before yes that's singular a big and I was just thinking of myself how boring this universe is going to be you've got this exponential expansion this was discovered early in the in this century aged my dear 21st century people discovered that these supernovae ... Read More

Questions & Answers

Q: What is the role of black holes in the future of the universe?

Black holes will dominate the future universe by engulfing galaxies and clusters, growing larger until they eventually evaporate through Hawking's black hole evaporation.

Q: How does infinity manifest itself in the physical universe?

Infinity can be observed in different ways, such as in Euclidean and hyperbolic geometries, where it represents a boundary or a place beyond which there is no mass or measurement of space and time.

Q: Can information travel from one eon to another in a cyclical universe?

According to the theory presented, signals, such as gravitational waves released during black hole collisions, can travel from one eon to the next, suggesting the potential for communication between cycles.

Q: Why haven't we received signals from advanced civilizations if the universe cycles through eons?

The lack of signals from advanced civilizations could be due to our limited understanding and search methods, with the possibility that successful civilizations exist but have different ways of communication that we are unaware of.

Q: How does the concept of infinity relate to the expansion of the universe?

As the universe expands and approaches its infinite future, the concept of infinity becomes more prominent, both in terms of infinite coldness and the conformal structure of space-time.

The concept of infinity is intertwined with the expansion and future states of the universe. From hyperbolic geometry to the boundary of space-time, infinity plays a significant role in our understanding of the universe's behavior and potential communication between eons. However, due to our limited knowledge and search methods, we have yet to discover or interpret the signals that might exist from other civilizations.


This video discusses the concept of conformal cyclic cosmology, which suggests that the universe goes through cycles of expansion and contraction punctuated by the Big Bang. The speaker explains that as the universe expands, it becomes increasingly boring until eventually everything, including black holes, evaporates away. However, he proposes that in the remote future and the far past, there may exist signals that can be observed and potentially used for communication between different eons. This opens up possibilities for exploring the Fermi paradox and the potential existence of intelligent civilizations in the universe.

Questions & Answers

Q: How does the concept of conformal cyclic cosmology explain the expansion of the universe?

Conformal cyclic cosmology suggests that the universe experiences cycles of expansion and contraction. The speaker notes that early in the 21st century, it was discovered that the universe is currently undergoing an exponential expansion. This expansion is described as self-similar and is attributed to the presence of the cosmological constant, which was introduced by Einstein into his cosmology. While Einstein initially believed it to be a mistake, it turned out to be accurate.

Q: What happens as the universe continues to expand?

The speaker explains that as the universe continues to expand, it becomes increasingly boring. He suggests that black holes are the most interesting things in the universe, as they can engulf entire clusters of galaxies. However, even black holes eventually grow bigger and swallow up most of the matter in the universe. This process continues until the black holes start to evaporate due to Hawking's black hole evaporation, leading to their eventual disappearance.

Q: What happens after the black holes evaporate?

After the black holes evaporate, the universe becomes even more boring. The speaker describes it as getting colder and colder until there is nothing left, not even black holes. At this point, only photons remain in the universe. The photons, being massless particles, do not experience time in the same way as massive particles. They reach infinity without any experience of time, according to the principles of relativity.

Q: How does infinity manifest itself in our physical universe?

The speaker explains that infinity manifests itself in various ways in our physical universe. Although infinity may seem difficult to comprehend for non-mathematicians, mathematicians often deal with different types of infinities and become accustomed to the concept. One example of infinity is in Euclidean geometry, where it extends indefinitely. Other geometries, such as hyperbolic geometries, also incorporate infinity but with some differences. The speaker suggests that infinity can be thought of as the boundary of a structure, similar to the angels and devils in MC Escher's artwork.

Q: Can photons experience infinity in the same way humans perceive it?

The speaker states that photons, being massless particles, do not experience infinity as humans do. He explains that, due to the nature of photons and the principles of relativity, they can reach infinity without a sense of time or experience. From their perspective, infinity is just another place to travel to. He compares this idea to MC Escher's artwork, where the angels and devils approach the boundary of infinity. To photons, infinity is like a mathematical notion that represents a boundary rather than an actual place with something on the other side.

Q: How do mass and frequency relate to space and time?

The speaker discusses the equivalence between mass and energy, as described by Einstein's equation E = mc². He also mentions Max Planck's equation E = Hν, which relates energy and frequency. Combining the two, the speaker explains that mass and frequency are equivalent. He further explains that mass brings about precise clocks due to the scaling down of massive entities to atomic or nuclear clocks. The absence of mass means the absence of clocks, rulers, and a measure of the scale of space and time.

Q: How does conformal scaling affect space-time?

The speaker introduces the idea of conformal scaling, which allows for the representation of space-time with a focus on shape rather than scale. He explains that in the remote future, where massive entities lose their sense of scale, the conformal structure of space-time remains. This structure, similar to the angels and devils in MC Escher's work, maintains the same shape but can be scaled up or down. The speaker proposes that in the Big Bang and the remote future, although they appear different, conformal scaling can connect them, making them almost the same.

Q: Can information from previous eons be observed or accessed from our current eon?

The speaker suggests that signals from previous eons can indeed be observed in our current eon. He highlights the importance of black hole collisions as sources of energy in the form of gravitational waves that can traverse between eons. These signals offer the potential for communication or information exchange between different eons. This concept raises interesting questions about the Fermi paradox and the lack of contact with intelligent civilizations, as it opens the possibility of communication through different eons rather than just between neighboring civilizations.


This video introduces the concept of conformal cyclic cosmology, which proposes cyclical expansions and contractions of the universe. It explains how the universe becomes increasingly boring as it expands, ultimately leading to the evaporation of black holes and the eventual coldness of an empty universe. The idea of infinity is discussed, with comparisons to artwork by MC Escher. The speaker suggests that photons can reach infinity without experiencing time, and this notion is connected to conformal scaling in space-time. Additionally, the video explores the possibility of signals from previous eons being observed and the potential for communication between different eons. This challenges conventional thinking about the Fermi paradox and the search for extraterrestrial intelligence.

Summary & Key Takeaways

  • The universe is currently expanding exponentially due to the cosmological constant introduced by Einstein, which will lead to a future where black holes dominant and swallow up galaxies.

  • After the black holes evaporate, the universe will become cold and empty, with only photons remaining.

  • Infinity plays a role in various aspects of the universe, such as hyperbolic geometries and the boundary of space-time.

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