Roger Penrose: "I had this strange feeling of elation"

TL;DR

Roger Penrose’s key breakthrough was the trapped surface, a geometric way to identify when gravitational collapse passes a point of no return without assuming perfect symmetry. His 1965 work established a theoretical basis for black holes, while his later cosmological proposal suggests that evaporated black holes from a previous aeon may have left detectable warm regions in the cosmic microwave background.

Transcript

hello hello this is adam smith speaking yes hello many many congratulations on the award of the nobel prize uh thank you so much it's much appreciated um how did the news actually reach you all a bit peculiar i'm not sure i want to go into it at all no i had a call from patrona who who received a message from the swedish academy and she wasn't sure... Read More

Key Insights

• A trapped surface is Penrose’s geometric characterization of the stage at which gravitational collapse has passed a point of no return. The concept avoids assuming perfect symmetry, which was crucial because earlier black-hole models depended on highly simplified, completely symmetrical conditions.
• The earlier collapse model is based on a 1939 paper by Oppenheimer and Schneider involving a pressureless dust cloud. Because dust has no pressure and the model is completely symmetrical, everything falls toward the center and produces a singular point resembling a black hole.
• Penrose’s collapse theorem is based on geometrical reasoning about four-dimensional space-time rather than directly solving highly complicated equations. He said that a strong visual understanding of space-time geometry was crucial and described himself as a visual thinker who generally thinks through pictures instead of equations.
• The trapped-surface idea came to Penrose while he was crossing a road with Ivor Robinson. After noticing an unexplained feeling of elation later that day, he mentally reviewed the day, recovered the idea formed during the crossing, and returned to his office to sketch the proof.
• Black holes are, in Penrose’s account, fundamental to the second law of thermodynamics because they contain by far the greatest entropy in the universe. He accepts Hawking’s conclusion that black holes eventually evaporate, including the largest black holes in the extremely remote future.
• Conformal cyclic cosmology is Penrose’s proposal that the universe’s remote future can morph into another big bang. Once people, matter, and ultimately physical means of measuring scale are gone, he argues that the universe effectively forgets its size and becomes the beginning of a new aeon.
• Hawking points are proposed regions in the cosmic microwave background carrying concentrated energy from black holes in a previous aeon. Penrose says their signals would spread during the first 380,000 years and appear as warmed regions roughly eight times the diameter of the Moon.
• The reported observational signal is found, according to Penrose and his collaborators, at the same locations in WMAP and Planck satellite data. Their paper claims 99.98 percent confidence that the six most significant points represent a real signal rather than random variation.

Questions & Answers

Q: How did Roger Penrose develop the trapped-surface idea?

Roger Penrose said the crucial idea arose while he was crossing a road with his friend Ivor Robinson. Their conversation paused as they watched for traffic, then resumed on the other side. After Robinson left, Penrose felt an unexplained sense of elation. By reviewing the day’s events, he recovered the idea, returned to his office, and sketched a proof of the collapse theorem.

Q: What is a trapped surface in Penrose’s black-hole theory?

A trapped surface is Penrose’s geometric characterization of when gravitational collapse has reached a point of no return. Its importance is that it does not require the collapsing system to have perfect symmetry. This allowed Penrose to construct a general argument about collapse without depending on the simplified symmetrical assumptions used in earlier theoretical models.

Q: Why were earlier black-hole collapse models considered unconvincing?

The earlier model Penrose discussed described the collapse of a dust cloud that had no pressure and was completely symmetrical. With no pressure to resist collapse and all material falling directly toward the center, a singular point followed naturally. Many physicists remained unconvinced that this outcome would persist in a general, nonsymmetrical situation rather than being an artifact of the model’s assumptions.

Q: How did geometry help Penrose study gravitational collapse?

Penrose approached collapse through space-time geometry instead of attempting to solve equations that were too complicated or imposing simple symmetry assumptions. He visualized the complete four-dimensional space-time and used geometrical reasoning to identify the trapped surface. This framework gave him a way to argue that collapse and singular behavior could occur under more general conditions.

Q: How does Roger Penrose connect black holes with entropy?

Penrose says black holes are fundamental to the second law of thermodynamics because the greatest entropy in the universe is located in them by an enormous factor. The second law says entropy, or randomness, increases with time. In his account, the eventual evaporation of black holes removes this concentrated entropy and helps establish the conditions connecting one cosmic aeon with another.

Q: What is Roger Penrose’s cyclic cosmology proposal?

Penrose proposes that the universe does not end with its remote exponential expansion. After people and matter disappear and black holes evaporate, the universe has no remaining physical means of establishing scale, so it effectively forgets how large it is. That scale-free future then morphs into the big bang of a new aeon, while our big bang emerged from the previous aeon.

Q: What are Hawking points in the cosmic microwave background?

Hawking points are proposed signatures of black holes that existed in the aeon before ours and later evaporated. Penrose says their concentrated energy passes into our aeon at individual points. Because nothing becomes visible until 380,000 years after the big bang, each signal spreads into a warmed region in the cosmic microwave background about eight times the diameter of the Moon.

Q: What evidence does Penrose give for black holes from a previous aeon?

Penrose says a paper written with Christoph Meissner, Pavel Nurowski, and Daniel An examined possible Hawking points in satellite observations. The six most significant points appeared in the same locations in both WMAP data and the more recent Planck data. The paper reported 99.98 percent confidence that the observed signal was real rather than random.

Summary

In this video, Adam Smith speaks about receiving the Nobel Prize and discusses his work on black holes. He shares how he came up with the idea of a collapse theorem for black holes and the significance of black holes in the second law of thermodynamics. Smith also talks about the visualization of black holes and his cosmology scheme. He concludes by mentioning his recent paper on the remnants of black holes in the previous eon and their presence in the current universe.

Questions & Answers

Q: How did the news of the Nobel Prize reach Adam Smith?

Adam Smith received a call from Patrona, who had received a message from the Swedish Academy. The communication was a bit peculiar as Patrona wasn't sure about the nature of the message. Smith was eventually informed about the award after a call back from the Swedish Academy.

Q: What were the initial observations and theoretical models of black holes?

In 1939, Oppenheimer and Schneider discussed a theoretical model of a collapse of a dust cloud, resembling a black hole. However, the model was not widely accepted due to the symmetrical nature and lack of pressure in the dust. Two Russian physicists, Lifshitz and Khalatnikov, published a paper suggesting that in the general case, singularities would not occur in black holes. Smith found their approach unconvincing and started thinking about the problem in a more geometrical way to produce his own arguments.

Q: Can Adam Smith share the story of how he had the crucial idea for the collapse theorem?

While crossing the road with his friend Ivor Robinson, Smith had a feeling of elation after reaching the other side and couldn't figure out why. He traced back his day's events and realized that the specific moment of crossing the street was when he had the idea of a trap surface, which formed the basis of his collapse theorem.

Q: Was Adam Smith able to identify the crossroads where he had the idea?

Smith has revisited the crossroads, but it has been ruined now, with new buildings at the other end of the road. He prefers not to disclose the exact location, as he hasn't had any good ideas revisiting that spot. However, he jokes that theoreticians might flock there for inspiration.

Q: How does Adam Smith feel about being portrayed in films like "The Theory of Everything"?

Smith finds it strange to be portrayed in films because he doesn't identify with the character presented. The concepts around black holes are captivating in popular imagination but don't necessarily align with the personal experiences of a physicist.

Q: Does Adam Smith visualize black holes? How does he think of them?

Yes, Smith visualizes black holes. He emphasizes the importance of understanding the four-dimensional space-time geometry rather than just three dimensions. As a visual thinker, he relies on mental images to comprehend the complex concepts of black holes.

Q: How are black holes related to the second law of thermodynamics?

Black holes play a crucial role in the second law of thermodynamics. They contribute to the universal increase in entropy and randomness over time. Smith has always been puzzled by the second law, and he explains that the majority of the universe's entropy is concentrated in black holes. According to Stephen Hawking, these black holes will eventually evaporate over extremely long periods.

Q: Can Adam Smith explain his cosmology scheme and the idea of the universe "forgetting" its size?

Smith proposes a cosmology scheme where the current universe, once devoid of all matter, forgets its size when observed from within. This idea seems crazy, but without any measurement reference, the universe effectively becomes the starting point for the next "eon" or iteration. Black holes from the previous eon would have evaporated, leaving behind remnants comprising a singularity or radiation. These remnants, referred to as "Hawking points," are believed to be observable regions in the sky and serve as evidence for Smith's cosmology scheme.

Q: How was the presence of Hawking points in the universe verified?

Smith collaborated with a group of colleagues and published a paper supported by data from the WMAP and Planck satellites. They claim that the regions in the sky, about eight times the size of the moon, show significant heating and are the remnants of black holes from the previous eon. The confidence level from the data is 99.98%, suggesting these signals are not random but real.

Q: How does Adam Smith view the connection between different universes in his cosmology scheme?

Smith presents a beautiful image of the previous universe leaving traces in the current universe, while the current universe might leave similar traces for the next one. It is an interconnected and continuous cycle of universes, which he refers to as "aeons." However, he doesn't elaborate further on the exact nature of this connection.

Takeaways

Adam Smith's groundbreaking work on black holes and his collapse theorem has earned him the Nobel Prize. He explains his thought process and the significance of black holes in the second law of thermodynamics. Smith visualizes black holes in terms of four-dimensional space-time geometry. He also shares his cosmology scheme, suggesting a connection between universes and presenting evidence for remnants of black holes. His ideas offer a unique and captivating perspective on the nature of the universe.

Summary & Key Takeaways

• Penrose received news of the 2020 Nobel Prize in Physics through a confused sequence of telephone calls. Discussing the recognized work, he traced it to ideas developed in 1964 after quasars had been observed and physicists were debating whether singularities would survive in realistic, nonsymmetrical gravitational collapse.

• Earlier collapse models used pressureless dust and complete symmetry, making a central singularity difficult to regard as physically general. Penrose approached the problem geometrically instead of trying to solve highly complicated equations. His trapped-surface concept characterized a point of no return without symmetry and enabled him to sketch a collapse theorem published in 1965.

• Penrose also connected black holes with entropy and described his cyclic cosmological proposal. After matter disappears and black holes evaporate, he argues that the universe loses its physical scale and becomes the next aeon’s big bang. He identified possible Hawking points in matching locations within WMAP and Planck satellite data.