Barry Barish: Gravitational Waves and the Most Precise Device Ever Built | Lex Fridman Podcast #213 | Summary and Q&A

August 23, 2021
Lex Fridman Podcast
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Barry Barish: Gravitational Waves and the Most Precise Device Ever Built | Lex Fridman Podcast #213


LIGO, the Laser Interferometer Gravitational-Wave Observatory, is the most precise measurement device ever built, designed to detect minuscule gravitational waves caused by cataclysmic events in the universe.

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Questions & Answers

Q: How does LIGO detect gravitational waves?

LIGO uses an interferometer, which splits a laser beam and measures the difference in time it takes for the beams to return, allowing it to detect the distortion of space-time caused by gravitational waves.

Q: What is the significance of LIGO's measurement capabilities?

LIGO's incredible precision allows scientists to observe the most violent and cataclysmic events in the universe that occur millions of light-years away, providing valuable insights into our understanding of the cosmos.

Q: How did LIGO overcome engineering challenges, such as isolating from earth's motion?

LIGO tackled engineering challenges by using shock absorbers and active cancellation mechanisms to isolate and minimize vibrations caused by the movement of the Earth, ensuring accurate gravitational wave detection.

Q: What is the size of the distortion LIGO aims to measure, and how is it achieved?

LIGO aims to measure distortions as small as one part in 10^21, which is approximately 1/1000th the size of a proton. This is achieved using a complex system of high vacuum chambers, lasers, mirrors, and sensitive detectors, all meticulously designed to capture these minute fluctuations in space-time.

Q: How does LIGO contribute to our understanding of the universe?

By detecting and studying gravitational waves, LIGO allows scientists to explore phenomena such as black hole mergers and neutron star collisions, shedding light on the nature of gravity, the behavior of matter under extreme conditions, and confirming predictions made by Einstein's theory of general relativity.

Q: What were some of the biggest challenges faced by LIGO in its development?

One major challenge was the creation of a massive high vacuum system capable of isolating LIGO's sensitive instruments from external noise. Detecting and fixing potential leaks in the vacuum system was also a significant concern due to the enormous size of the LIGO apparatus.


In this conversation, theoretical physicist Barry Barish discusses his curiosity-driven approach to science and the importance of nurturing curiosity in education. He also delves into the concept of gravitational waves and their detection, as well as the challenges and potential implications of these waves.

Questions & Answers

Q: What are some early questions in math and physics that sparked Barry Barish's curiosity?

Barry Barish recalls asking his father why ice floats on water and being intrigued by the fact that his father couldn't answer the question. This childhood experience taught him the value of curiosity and the importance of finding answers through research and asking good questions.

Q: Is there advice or insights on how to nurture curiosity?

According to Barry Barish, it is crucial for parents and educators to recognize and encourage curiosity in children. Rather than discouraging their endless questions, curiosity should be seen as a positive trait. It is a quality that scientists possess and one that should be nurtured in all individuals.

Q: Can Barry Barish recall any other questions from his high school or college days that sparked his curiosity?

Barry Barish admits that he wasn't initially interested in science until college. However, he remembers being curious about what happens to water when it rains and how it dries up on pavements. He was particularly fascinated by the transformation of gases like hydrogen and oxygen into the liquid form of water.

Q: Did Barry Barish look up to the stars and wonder about the universe similarly to his childhood curiosity about ice floating on water?

Yes, Barry Barish believes that most people are in awe and curious about the universe. The endless mysteries and unknowns fascinate us, although the more we learn, the more we realize how little we know. Exploring the universe and its questions, such as dark matter and dark energy, is a universal human curiosity.

Q: What are some questions about the universe that fill Barry Barish with curiosity?

Barry Barish mentions that the questions that pique his curiosity lie within the realms of dark matter and dark energy. These areas have been the focus of his research, especially in understanding how these mysteries that make up the majority of the universe can be explained and detected.

Q: Do the answers to these questions about dark matter and dark energy have potential implications?

Yes, understanding dark matter and dark energy could potentially change how we perceive gravity and other phenomena in the universe. It may lead to a deeper understanding of sources of gravity such as black holes and their complex interactions within the universe.

Q: Could the complexity of finding answers to questions about dark matter and dark energy imply that the solutions are also intricate?

Barry Barish has a hopeful perspective that many seeming complexities in science can be explained in simple terms once they are truly understood. While we currently lack the answers to questions about dark matter and dark energy, future discoveries may reveal that the solutions are, in fact, simple.

Q: Would these answers about dark matter and dark energy change how we see other sources of gravity in the universe, such as black holes?

It is conceivable that understanding dark matter and dark energy could alter our understanding of black holes and how they interact with other parts of the universe. The specific nature and behavior of black holes, including their origin and mass, are still areas of ongoing research and understanding.

Q: How did Enrico Fermi inspire Barry Barish?

Enrico Fermi was a physicist known for his experimental work and contributions to fields like beta decay and fission. Barry Barish admires Fermi for being both an experimentalist and a theorist. He was impressed by Fermi's ability to solve complex problems and make significant discoveries in nuclear physics.

Q: Why is Enrico Fermi considered the architect of the nuclear age, and does it trouble Barry Barish that some of Fermi's work led to destructive weapons?

Enrico Fermi's work in nuclear physics, including his involvement in the creation of the atomic bomb, earned him the title of the architect of the nuclear age. While Fermi's contributions were significant, Barry Barish acknowledges that the nuclear bomb and its devastating effects are tragic. It is not a legacy he would want for himself, and he recognizes the broader consequences of scientific progress.

Q: Did Enrico Fermi become cynical about the human species in light of his work with the atomic bomb?

Barry Barish speculates that Fermi's experiences working on the atomic bomb and witnessing its destructive power might have influenced his perception of the human species. He suggests that the pursuit of knowledge and scientific advancements can have unintended consequences, highlighting the importance of responsible scientific exploration.

Q: What is the Fermi paradox, and how does it relate to the existence of alien civilizations?

The Fermi paradox questions the apparent absence of evidence for other alien civilizations, despite the high probability of their existence based on statistical models. Barry Barish explains that the paradox originated from a conversation between Enrico Fermi and others contemplating the lack of clear signs of extraterrestrial life. The paradox raises the question of why we haven't encountered evidence of other intelligent civilizations in the vast universe.

Q: Could gravitational waves be used for communication between advanced civilizations?

Barry Barish believes that the limitations imposed by the speed of light and electromagnetic-based communication make it challenging for us to detect or utilize gravitational waves for efficient communication. While we currently lack knowledge of alternative communication methods, Barry Barish acknowledges that there may be different scientific approaches and possibilities that we have not discovered yet.

Q: How are gravitational waves generated, and why are they challenging to detect?

Gravitational waves are generated by objects that possess a quadrupole moment, such as two massive objects orbiting each other, like the Earth around the Sun or black holes. However, the challenge lies in the fact that gravitational waves are incredibly weak. To detect them, we need sources that are stronger than what we can produce in our laboratories.

Q: Can Barry Barish explain what it feels like to ride a gravitational wave?

Barry Barish describes that the experience of a gravitational wave passing through objects is similar to the effect of funhouse mirrors. Just as these mirrors can distort and change the perceived size and shape of a reflection, gravitational waves cause distortions in space and time as they pass through objects. However, these effects are incredibly small due to the stiffness of space-time itself.

Q: Does Barry Barish consider the philosophical implications of general relativity, specifically the bending of space-time?

Barry Barish acknowledges the mind-blowing nature of the bending of space-time and the philosophical questions that arise from it. However, he mainly focuses on the scientific aspects and the understanding of gravitational waves rather than delving deeply into the philosophical implications of general relativity.

Q: How does Barry Barish think humans have evolved to exist in a universe with gravitational waves?

Barry Barish expresses the belief that humans have likely evolved to exist in a universe where gravitational waves are not a significant factor in their everyday lives. The small distortions caused by gravitational waves are not noticeable in our ordinary experiences, allowing us to navigate and function in the physical world without much disruption.

Q: How is the detection of gravitational waves relevant to everyday life?

Barry Barish explains that while the detection of gravitational waves is not directly relevant to everyday life, it contributes to scientific progress and expands our understanding of the universe. It opens up new avenues for exploration and may provide insights into celestial phenomena such as black holes, affecting how we perceive the universe as a whole.


Barry Barish highlights the importance of curiosity and the need to nurture it in education. He emphasizes that curiosity is a valuable human quality that drives scientific progress, and discouraging it can hinder intellectual growth. Additionally, the conversation explores the concept of gravitational waves and their detection, shedding light on the mysteries of the universe and the challenges involved in studying and understanding them.

Summary & Key Takeaways

  • LIGO is an incredibly precise measurement device designed to detect gravitational waves caused by violent events in the universe.

  • Gravity-based measurements are ten thousand times smaller than the width of a proton, making LIGO's detection capability a marvel of human engineering.

  • Gravitational-wave detection is achieved through an interferometer, which uses laser beams and mirrors to measure the distortion of space-time caused by these waves.

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