What this covers
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“We don't have enough knowledge to precisely calculate what is going to happen, and so we assign probabilities to it, which reflects our ignorance of the situation.”
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What do snowflakes, glowing street lamps, and Einstein’s “crazy” idea have in common? Physicist Brian Cox unwinds the surprising origins of quantum mechanics—the theory that shattered classical physics and redefined our understanding of reality.
From Kepler’s insight in a 17th-century snowstorm to Planck’s revolutionary leap in 1900, Cox traces how curiosity and confusion gave rise to the most baffling theory in science.
00:00:00 Part 1: The power of quantum mechanics 00:00:24 What are considered the earliest glimpses of quantum mechanics? 00:06:39 How did Einstein's work on the photoelectric effect impact science? 00:12:17 How does quantum physics conflict with classical theory? 00:17:11 What is the double-slit experiment? 00:26:25 Why is it important that we seek to solve the mysteries of quantum physics? 00:33:30 Part 2: The fundamental measurements of nature 00:45:15 What kinds of insights does the Planck scale reveal? 00:52:15 Where does our comprehension of scale break down? 01:01:30 Part 3: The frontiers of the future 01:10:21 How can humanity influence the universe?
Read the video transcript ► https://bigthink.com/series/full-interview/brian-cox-full-interview/?utm_source=youtube&utm_medium=video&utm_campaign=youtube_description
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---------------------------------------------------------------------------------- About Brian Cox:
Brian Cox obtained a first class honors degree in physics from the University of Manchester in 1995 and in 1998 a Ph.D. in High Energy Particle Physics at the DESY laboratory in Hamburg. He is now Professor of Particle Physics at the University of Manchester, The Royal Society Professor for Public Engagement in Science and a Fellow of the Royal Society.
Brian is widely recognized as the foremost communicator for all things scientific, having presented a number of highly acclaimed science programs for the BBC watched by billions internationally including ‘Adventures in Space and Time’ (2021), ‘Universe’ (2021), ‘The Planets’ (2018), ‘Forces of Nature’ (2016), ‘Human Universe’ (2014), ‘Wonders of Life’ (2012), ‘Wonders of the Universe’ (2011) and ‘Wonders of the Solar System’ (2010).
As an author, Brian has also sold over a million books worldwide including ‘Black Holes’, ‘Universal: A Guide to the Cosmos’, ‘Quantum Universe’ and ‘Why Does E=mc2?’ with co-author Professor Jeffrey Forshaw. He has set several world records for his sell-out live tours, including his most recent tour Horizons which has taken in venues across the globe.
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Brian Cox argues that quantum mechanics reveals a profoundly counterintuitive but well-defined reality underlying everyday experience, and understanding its fundamental scales and principles is essential as we develop quantum technologies and expand civilization into space.
- Quantum mechanics is not merely mathematical convenience but describes real physical behavior (superposition, entanglement, wave-particle duality)
- Fundamental constants (Planck's constant, speed of light, gravitational constant) define measurable scales like the Planck length that determine physical limits and structures across the universe
- Life and civilization, while physically insignificant, may eventually influence cosmic-scale structures if they persist long enough and develop sufficient technological power
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Quantum probabilities are fundamentally intrinsic to the theory itself and describe the nature of reality, not merely the incompleteness of human knowledge; this contrasts with classical probabilities (like 'a 50% chance of rain tomorrow') which reflect epistemic uncertainty about an underlying determined state.
“usually we'd say, well, there's a 50% chance it's gonna rain tomorrow. Why do we say that? Why would we say such a thing? It's because we have incomplete knowledge of the system, in this case, of the weather... we don't have enough knowledge to make, to precisely calculate what is going to happen, and so we assign probabilities to it, which that reflects our ignorance of the situation. The key difference in quantum theory is that these probabilities are fundamental. They are fundamental to the description of nature. So it is not the case that if we have an electron in some kind of configuration, then our theory predicts probabilities because we don't quite know exactly how this thing is configured. The probabilities are intrinsic to theory itself.”
Planck's own written reference for Einstein years after the 1905 photoelectric paper stated that 'Einstein's belief in the reality of photons should not be held against him,' indicating the intellectual difficulty the physics community had accepting that light truly comes in discrete packets.
“there's a very famous letter of reference that Planck wrote for Einstein years later. It was in the 1910s, I think. So for six, seven, eight years later, recommending him for a position for an award. And Planck said that Einstein's belief in the reality of photons should not be held against him, and this is years after the 1905 paper.”
Johannes Kepler's 1610 book 'On the Six-Cornered Snowflake' demonstrates insight into the relationship between observed symmetry in nature and underlying building blocks, foreshadowing modern understanding that the six-fold symmetry of snowflakes arises from the geometry of the water molecule (H₂O) and the way electrons are arranged around oxygen and hydrogen atoms.
“There's a beautiful book by Johannes Kepler...called 'On the Six-Cornered Snowflake'...he essentially says that it must be something to do with the building blocks. There must be some underlying reason why nature has this symmetry...We now know it's to do with the water molecule, so the shape of the water molecule, H2O. Two hydrogens bonded to an oxygen...which you can calculate now from quantum mechanics and the way that electrons are arranged around the oxygen and the hydrogen”
Planck himself did not initially believe his quantization hypothesis was physically real, regarding it instead as a calculational device, likely related to how matter oscillates rather than being a property of light itself.
“he didn't really at the time think that it was, he thought it was a calculational device.”
In quantum mechanics, unlike classical probability which reflects incomplete knowledge of a system, probabilities are fundamental to the description of nature itself; they are not a measure of ignorance but an intrinsic feature of quantum theory, arising even when complete information about a quantum system is available.
“The key difference in quantum theory is that these probabilities are fundamental. They are fundamental to the description of nature. So it is not the case that if we have an electron in some kind of configuration, then our theory predicts probabilities because we don't quite know exactly how this thing is configured. The probabilities are intrinsic to theory itself. And pretty much all of the intellectual challenges and the confusion around quantum mechanics comes from that very simple property.”
Human perception and intuition for distance scales break down around scales larger than those experienced in terrestrial travel (roughly 100 miles to a few thousand miles); as distances grow to astronomical scales (millions to billions of light-years), they become inconceivable.
“I think it's quite difficult to even picture... 100 miles you can picture, 'cause you can take a train ride, or a few thousand miles you can picture because you can get on an aircraft and fly across the Atlantic... when you get much bigger than that, we don't experience those distances anymore... when we start to talk about distances that are much larger than distances that we might travel on the surface of the earth, then I think our feel for those distances begins to break down.”
There are not different rules of physics in the subatomic quantum world versus the macroscopic world of common sense; it is well-understood how the macroscopic world emerges from quantum mechanical behavior at small scales.
“I think it's important to say that there aren't different rules of the game in the subatomic world and the world that we observe, this world of common sense, let's say, that we perceive. There aren't different rules. And it's pretty well understood, I would say it's well understood how the world that we see emerges from this rather strange but well-defined behavior that we see in the subatomic world.”
The maximum mass that matter can support against gravitational collapse via quantum mechanical electron degeneracy pressure (the Chandrasekhar limit) is approximately 1.4 times the solar mass, demonstrating a deep connection between quantum mechanics, gravity, and observable stellar properties.
“If you do that calculation, you find that the maximum mass of a star, which is just a lump of matter held up by this process is 1.4 times the mass of our sun... it's astonishing calculation... we've used quantum mechanics and we've used the strength of gravity... Chandrasekhar did this magnificent calculation... Turns out when you do the calculation that roughly speaking, that number, the Chandrasekhar limit is the Planck mass cubed divided by the proton mass squared.”
Life has already transformed Earth over billions of years: photosynthesis created the oxygen-rich atmosphere; civilization has visibly transformed Earth's surface, visible at night from space with city lights; therefore life is not inherently cosmically insignificant.
“its atmosphere is the product of life. It's got oxygen in it in high concentration. It would not have that without photosynthesis... our civilization has sculpted the surface of the Earth. You see it, if you look at the Earth from space, you don't just see oceans, you don't just see a kind of common or garden planet. On the night side of the planet, you see our civilization.”
The rules of quantum mechanics apply at both the subatomic scale and the macroscopic scale we observe; the emergence of classical behavior from quantum mechanics is well-understood, and there are not different physical rules governing the two scales.
“I think it's important to say that there aren't different rules of the game in the subatomic world and the world that we observe, this world of common sense, let's say, that we perceive. There aren't different rules. And it's pretty well understood...how the world that we see emerges from this rather strange but well-defined behavior that we see in the subatomic world.”
A 100-qubit system has 2^100 possible combinations and states that must be described, a number far exceeding the atoms in the observable universe, yet such systems are conceivable to build, revealing the vast computational power hidden in quantum entanglement and superposition.
“We are talking about building quantum computers now in which we have 100, 200, 300 qubits all in principle entangled together. The number of possible descriptions of that system then, you have numbers that describe it, there are 100. It's two to the power 100 different configurations, and any mixture of those things that are states of the system.”
Planck's reference letter for Einstein in the 1910s (years after Einstein's 1905 photoelectric paper) cautioned that 'Einstein's belief in the reality of photons should not be held against him,' indicating that the physics community of that era found the notion that light truly consists of particles to be controversial and counterintuitive.
“there's a very famous letter of reference that Planck wrote for Einstein years later. It was in the 1910s, I think. So for six, seven, eight years later, recommending him for a position for an award. And Planck said that Einstein's belief in the reality of photons should not be held against him, and this is years after the 1905 paper.”
The ratio in size between the Planck length and a living cell (observable under a microscope) equals the ratio between a proton and the solar system, illustrating that the Planck length is unimaginably small on any conceivable scale.
“If you take a proton and expand it to the size of our solar system, so imagine that, the nucleus of a hydrogen atom, and you imagine expanding that to the size of our solar system, out to the orbit of Neptune, then something that's the Planck length would extend or expand to let's say a virus or a living cell... the ratio in size between the Planck length and a cell, which we can just about under a microscope, is the same ratio as a proton to the solar system.”
Kepler's 1610 book 'On the Six-Cornered Snowflake' demonstrates early insight into how underlying building blocks of matter determine macroscopic symmetries in nature; the six-fold symmetry of snowflakes arises from the shape of the water molecule (H₂O), which can now be calculated from quantum mechanics and the arrangement of electrons around oxygen and hydrogen.
“There's a beautiful book that Kepler wrote in 1610 called 'On the Six-Cornered Snowflake,' which to me really illustrates the genius of Kepler... he noticed that whilst they're all different, there is a similarity to them. There's some things, a sameness, a sixness to them, some kind of symmetry that they all exhibit... he essentially says that it must be something to do with the building blocks... We now know it's to do with the water molecule, so the shape of the water molecule, H2O. Two hydrogens bonded to an oxygen in a very famous shape.”
An interstellar civilization expanding to populate the entire Milky Way galaxy is not forbidden by the laws of physics; nothing in physics prevents such expansion.
“Imagine our civilization expands to the stars, and becomes an interstellar civilization. Imagine our civilization populates the entire galaxy. There's nothing in the laws of physics that prevent that.”
Feynman's path integral method for calculating the probability of finding a particle at a detection screen involves assigning a complex number (picturable as a clock hand with direction and length) to every possible path the particle can take, summing all these clock faces, and using the squared length of the resultant hand as the probability; this mathematical prescription gives the correct experimental answer but leaves open the question of whether it represents reality.
“you can assign, calculate what's called a complex number for every route that the particle, the electron can take from gun through the slits to the screen...A complex number...can be pictured as a little clock face...you can calculate how those clock faces kind of evolve and change and spin around...every point on the screen, you have to take them all, every possible path to that point and just add them up. And the length of the clock hand gives you the probability to find the electron there...You just do that, you calculate it, and you get the right answer.”
As space becomes industrialized and crowded, there will be competition for orbital real estate and potential physical conflicts between satellites; management frameworks (such as air-traffic-control-like avoidance systems) do not yet exist but will be needed.
“when you start to move outwards to a new frontier, then the frontier can become crowded. You can have competition for the real estate. You can, you need some way of managing conflicts between, by which I mean conflict, physical conflicts between the satellites. What happens if someone's satellite comes close to another satellite? How do you manage that? Do you allocate particular orbits? Or do you say that we're gonna have some framework like air traffic control, where you have an avoidance system that everybody agrees on... That framework is not yet there.”
Quantum technologies—particularly quantum computers—are now being developed that rely on quantum mechanical properties like superposition and entanglement, making the interpretation of quantum mechanics no longer merely philosophical but practically important.
“now we have an increasing number of quantum technologies that are really based on this behavior, quantum computers being a good example... we're using that behavior now in technologies, and so it really does become an important theory to try to understand.”
Asteroid mining could provide access to vast resource quantities that would eliminate the artificial scarcity of resources on Earth, potentially transforming civilization by reducing competition for limited resources and allowing expansion without environmental damage.
“one of the biggest problems we face and have faced historically on Earth is competition for resources... if you have the infrastructure to begin to move outwards, for example, to the near Earth asteroids, then what you find is that resources are no longer limited in any reasonable sense. There are vast amounts of resources out there in space that we will have access to within the next decade or so, or certainly few decades... that begins to transform the way that we think about our civilization... there's a tremendous opportunity there to grow our civilization crucially, without further damaging the planet that most of us will live on for the foreseeable future.”
The Planck length appears to be fundamentally important to the structure of the universe because: (1) black hole entropy (calculated by Jacob Bekenstein in the 1970s) equals the surface area of a black hole's event horizon measured in square Planck lengths, suggesting information storage in spacetime is quantized at the Planck scale; (2) attempting to observe something smaller than the Planck length requires such high-energy photons that they would collapse into a black hole, preventing further resolution.
“How important is it? Well, let me give you some examples of the Planck length. So it turns out that if you ask a question, how much information in bits is stored inside a black hole, right?... in a calculation that was done by Jacob Bekenstein in the 1970s, it turns out that the entropy of a black hole, which is the amount of information hidden within it, is equal to the surface area of the event horizon of a black hole in square Planck lengths... So let's say we want to make an observation of some very small thing. So how do you observe something that's very small? Well, one way to do it is shine a light on it... the smaller the wavelength of the light, the higher the energy of the photons... What happens if you try to approach something that's a Planck length? You get so much energy in there that what you do is you form a black hole, and then you put more energy in, you try to see what's going on and the black hole grows.”
The Planck length (10^-35 meters) may not be absolutely fundamental; if extra dimensions exist in the universe (as suggested by some theories), the apparent strength of gravity could change at higher energies, meaning the Planck length could be larger than currently measured.
“There are theories, and we test these theories at places like the Large Hadron Collider, for example. There are theories where, as an example, there are extra dimensions in the universe... If there are extra dimensions in the universe, then you find that you can... see those extra dimensions, energies just around the energies that we collide particles at the Large Hadron Collider, then the explanation for why gravity is so weak... would change at those higher energies. It might mean that this Planck scale would drop, and so the Planck length would expand.”
Quantum computers can potentially carry out computations that no conceivable classical computer could complete within the lifetime of the universe because of the vast configurational space of entangled qubits.
“they can carry out computations that no conceivable classical computer could make within the lifetime of the universe, because of this tremendous freedom in the description of the structure of the system.”
Quantum technologies like quantum computers are now making quantum mechanics a practically important theory to understand, not merely a philosophical curiosity, because these technologies rely on quantum behavior like superposition and entanglement to perform computations that classical computers cannot.
“now we have an increasing number of quantum technologies that are really based on this behavior, quantum computers being a good example...we're using that behavior now in technologies, and so it really does become an important theory to try to understand.”
Human civilization has visibly transformed Earth's surface; viewing Earth from space at night reveals artificial lighting, showing that human civilization has become a geological-scale force reshaping the planet.
“and obviously now, our civilization has sculpted the surface of the Earth. You see it, if you look at the Earth from space, you don't just see oceans, you don't just see a kind of common or garden planet. On the night side of the planet, you see our civilization.”
Earth's atmosphere is a product of life; it would not contain high concentrations of oxygen without photosynthesis, demonstrating that life has already transformed a planetary system at scale.
“if you look at the Earth, its atmosphere is the product of life. It's got oxygen in it in high concentration. It would not have that without photosynthesis.”
Max Planck's 1900 proposal that hot objects emit light only in discrete packets (later called photons) rather than continuously across all wavelengths was a revolutionary leap that resolved the incorrect calculations of radiation from hot objects, introducing Planck's constant (h) as a fundamental constant of nature relating the energy of a light packet to its frequency through the equation E = hf.
“in 1900, Max Planck made a revolutionary proposal...he famously came up with the idea that a hot object only emits light in little packets, which subsequently we came to know as photons...the relationship of the energy of the little packets, the photon as we would now call it, to the frequency of the light is E = hf, where f is the frequency of the light, E is the energy of the packet, and h is this new constant of nature that we now know as Planck's constant.”
A qubit is a quantum system (such as an electron's spin) that can exist in a superposition of two states (analogous to heads and tails on a quantum coin), allowing it to be a combination like 30% heads and 70% tails, or any mixture thereof, which is a perfectly legitimate physical description.
“a quantum coin could indeed have the property that it would be heads or tails. But the difference between quantum mechanics and classical theory is that an object like a coin, a quantum coin can also be in what we call a super position of heads and tails...it can be in a state where it could be 30% heads and 70% tails, or 40% heads and 60% tails, or any combination, any mixture of heads and tails.”
The path integral formulation is a very simple prescription that produces correct experimental predictions, but the question of what it means—whether it merely represents calculational mathematics or whether electrons truly explore every possible route, including implausible ones like going to Andromeda and back—remains unresolved.
“the problem comes when you say, well, what does it mean? Does it really mean? Is it just calculational? Is this just mathematics? Or does it really mean that the electron explores every possible route? And by that, I mean every possible route. You might consider it going to the Andromeda galaxy and back, right? Every possible route on its journey from when it's emitted to when it's detected.”
The ideas of quantum mechanics are profoundly counterintuitive, and it took decades from the turn of the 20th century for a coherent theory to emerge, arguably in the 1920s, not because the mathematics is particularly difficult but because the conceptual framework conflicts with intuition.
“it's not so mathematically difficult, at least in an introductory presentation, but the ideas themselves are profoundly counterintuitive. And that's why it took, it wasn't the mathematics really, that's why it took decades from these early glimpses of quantum theory at the turn of the 20th century for a coherent theory to emerge, arguably in the 1920s.”
Units of measurement based on human body proportions (feet, meters, inches) reflect biology and Earth's gravity rather than fundamental properties of nature, so Max Planck developed a system of fundamental units based on universal constants (speed of light, gravitational strength, Planck's constant) that would be meaningful to any civilization regardless of their physical form.
“a meter might be, you know, the length of this kind of length, and a foot is kind of that kind of length... they're based on biology really... But of course, the history of physics tells us... we then begin to understand that there are things that are much bigger than us and much smaller than us... is the meter, for example, which is based on a property of the length of my arm, or the length of my foot or whatever it is, is that really, is that fundamental? Well, the answer is no... But it doesn't tell you anything profound or deep about the deep structure of the universe... Max Planck, so of Planck's constant fame and quantum mechanics fame, came up with a system of units, right? So a way of saying, well, what are the fundamental quantities as far as we can tell that really tell us something about the structure of nature?”
Jacob Bekenstein's 1970s calculation shows that the entropy (information content) of a black hole equals the surface area of its event horizon measured in square Planck lengths, revealing that the Planck length fundamentally relates to information and entropy.
“in a calculation that was done by Jacob Bekenstein in the 1970s, it turns out that the entropy of a black hole, which is the amount of information hidden within it, is equal to the surface area of the event horizon of a black hole in square Planck lengths. That's astonishing result.”
Even today, the interpretation of what quantum theory is telling us about the nature of reality itself is not universally agreed upon among physicists.
“even today, the interpretation of what theory is telling us about the nature of reality itself is not universally agreed upon.”
When trying to observe something very small, shining light with increasingly small wavelength requires photons with increasingly high energy; approaching the Planck length, the photon energy becomes so large that it forms a black hole, creating a fundamental resolution limit beyond which structure cannot be observed.
“The smaller this thing is, the smaller the wavelength of the light that I've gotta shine on it...the smaller the wavelength of the light, the higher the energy of the photons...What happens if you try to approach something that's a Planck length? You get so much energy in there that what you do is you form a black hole, and then you put more energy in, you try to see what's going on and the black hole grows...you get to a point which is around the Planck length in size where you can't, in principle, try to resolve the structure of this thing.”
We are entering an era of space exploration characterized by reusable rockets (SpaceX, Blue Origin), which make access to Earth orbit cheaper than ever before, enabling the industrialization of near-Earth space.
“because we have reusable rockets. So SpaceX, now Blue Origin, have reusable rockets, which means that access to earth orbit is cheap, or at least cheaper than it's ever been before. So we are industrializing the space above our heads just a few hundred miles above our heads at an ever increasing rate.”
Microgravity environments enable manufacturing advantages for certain applications (crystal growth, semiconductor production), suggesting material science and bioscience applications may benefit from on-orbit manufacturing as space infrastructure develops.
“we know, for example, so already from our experience on the International Space Station that sort of development of new drugs, for example, or development of new ways of building semiconductors, for example, silicon wafers and so on. Lots of experiments have been done that suggests that there might be an advantage to on orbit manufacturing... growing crystals and so on, which might be useful.”
The appropriate measure of time for an intelligent civilization might be the time it takes to process one bit of information, rather than conventional time measurements.
“what's the appropriate measure of time for a intelligent being? It's really, I think fundamentally, it should be considered, you should think of it as the time it takes to process one bit of information.”
In a Bell state where two electrons are separated (one on Earth, one on Pluto), measurement of one electron as 'up' instantaneously determines that the other must be 'down,' which troubled Einstein because it appeared that something was instantaneously changing across cosmic distances, not merely our knowledge of the system.
“So let's say I take one of these electrons and I separate them... I take one to let's say to Pluto and leave one on planet Earth... if I make a measurement of that one, if I say, well, okay, I know what that is, it's up, the other one has to be down... it would appear that something is instantaneously changing, and it's not just your knowledge of the system that's instantaneously changing, it would seem that the system itself is instantly configuring itself when you make some measurement.”
In the double-slit experiment, individual electrons sent one at a time through two slits still produce an interference pattern on a detection screen, indicating that each electron must somehow explore both paths (in some sense) and interfere with itself.
“you still get that pattern if you send one particle at a time through the slits. So it is, and let me use my language carefully, I was gonna say it is as if the electron can somehow explore both paths, just like a wave can, and then interfere with itself to control where it lands on the screen.”
Despite Einstein's objections to nonlocality in entanglement, experimental tests (for which a Nobel Prize was awarded) have shown that there is nothing hidden in the entangled system—this is genuinely how the system behaves.
“as far as we can tell that, and a Nobel Prize was awarded for some of this research a few years ago, then no, there's nothing hidden there. This is the way that the system is.”
The Planck length is calculated as the square root of (Planck's constant times gravitational constant divided by the cube of the speed of light), resulting in approximately 10^-35 meters.
“I could take Planck's constant, multiply it by the strength of gravity, and divide it by the cube of the speed of light, and then take the square root of the whole thing. So it's hG divided by C cubed, square root... it's a tiny length... about 10 to the minus 35 meters, point nought, nought, nought, nought, nought, nought, with 35 noughts one of a meter.”
The Planck length is a derived quantity calculated from fundamental constants (hG/c³)^(1/2) and equals approximately 10^-35 meters; it represents a length scale at which quantum gravitational effects become significant and space-time itself may exhibit quantum properties.
“I could take Planck's constant, multiply it by the strength of gravity, and divide it by the cube of the speed of light, and then take the square root of the whole thing. So it's hG divided by C cubed, square root. You'll find that that has...it has the dimensions of meters, and it's a tiny length. It's about 10 to the minus 35 meters.”
A white dwarf star is a remnant of stellar collapse where nuclear fusion has ceased; electrons are forced close together and quantum mechanical effects (Heisenberg uncertainty principle and Pauli exclusion principle) cause them to jiggle, creating pressure that holds the star up against gravity.
“as you try to, this star's collapsing and all the electrons are getting pushed together and closer and closer together. They try to avoid each other, which is another fundamental property of quantum mechanics called the exclusion principle...the electrons are getting confined, and so they jiggle faster. The uncertainty on their momentum is faster and faster...That jiggling is like a temperature in the sense it creates a pressure which can hold the star up.”
Eventually, a star exhausts its nuclear fuel and begins to collapse again; the question is whether it collapses without limit (becoming a black hole) or whether some other quantum mechanical property of matter can hold it up.
“the star doesn't have an infinite amount of fuel in its core... ultimately, will run out of fuel and it will begin to collapse again... When there's no more nuclear fusion can occur in the core, what happens to the star? Does it just collapse without limit? Which would be a black hole, as we now understand it. Or is there something else that can hold it up, some other property of matter?”
Quantum entanglement (described mathematically as a Bell state like 'up,down + down,up') is a state where two particles are correlated such that measuring one particle instantaneously determines the state of the other, even if separated across space; this bothered Einstein because it appears to violate local realism, but experiments confirm that no hidden variables explain the correlation.
“if I say, well, okay, I know what that is, it's up, the other one has to be down...This is called quantum entanglement. And the reason it bothered Einstein and others is it would appear that something is instantaneously changing...it turns out that as far as we can tell that, and a Nobel Prize was awarded for some of this research a few years ago, then no, there's nothing hidden there. This is the way that the system is.”
In the double slit experiment, when electrons are fired one at a time through two slits, they still produce an interference pattern on the detection screen, indicating that each individual electron must in some sense explore both possible paths simultaneously, not merely that we have incomplete knowledge of which path it took.
“you still get that pattern if you send one particle at a time through the slits...I was gonna say it is as if the electron can somehow explore both paths, just like a wave can, and then interfere with itself to control where it lands on the screen. As if is something that people might object to. Many physicists would say, no, it does...the electron must, in some sense, explore all routes on the way from the electron gun through the slits to the screen.”
Extra dimensions in the universe, either compactified at small scales or as extended sheets, could change how gravity's strength appears at high energies, potentially making the Planck scale larger than currently measured.
“There are theories where, as an example, there are extra dimensions in the universe... If there are extra dimensions in the universe, then you find that you can, let's say that they would, that you could see those extra dimensions, energies just around the energies that we collide particles at the Large Hadron Collider, then the explanation for why gravity is so weak... would change at those higher energies. It might mean that this Planck scale would drop, and so the Planck length would expand”
Mining near-Earth asteroids could provide vast amounts of resources, shifting civilization from resource scarcity to abundance and potentially transforming the basis of economic competition, reducing conflict and environmental stress on Earth.
“if you have the infrastructure to begin to move outwards, for example, to the near Earth asteroids, then what you find is that resources are no longer limited in any reasonable sense...But if you have access to the near Earth asteroids, then what you find is that resources are no longer limited in any reasonable sense. There are vast amounts of resources out there in space...But if you have access to the near Earth asteroids, then what you find is that resources are no longer limited in any reasonable sense. There are vast amounts of resources out there in space that we will have access to within the next decade or so, or certainly few decades.”
Research on the International Space Station has suggested possible advantages to on-orbit manufacturing in microgravity, particularly for developing new drugs, semiconductors, and crystals, opening possibilities for material science and bioscience applications.
“already from our experience on the International Space Station that sort of development of new drugs, for example, or development of new ways of building semiconductors...Lots of experiments have been done that suggests that there might be an advantage to on orbit manufacturing. So it's in a microgravity environment of certain things, growing crystals and so on, which might be useful.”
Physically, humans are insignificant specks of dust orbiting an ordinary star in one galaxy among 2 trillion, yet humans may still be remarkably valuable if intelligent civilizations are rare, because civilization may be the only way that collections of atoms can think, do science, and bring meaning to an otherwise meaningless universe.
“we're little specks of just a collection of atoms on one mote of dust, orbiting around one little star in 400 billion stars in one galaxy, amongst 2 trillion galaxies... clearly it is true, we are physically insignificant. So I've tended in the past to focus arguments... on what does it mean to live these finite fragile lives in this infinite universe?... notwithstanding our physical insignificance, we may be remarkably valuable because the number of civilizations on the average in a particular galaxy... might be less than one on the average. Many galaxies may not even have civilizations in them. If that is the case... we would be remarkably valuable... because we would be perhaps the only place in the Milky Way galaxy where collections of atoms have come together that can think, and do science, and have conversations like this, in a very real sense, bring meaning to an otherwise meaningless galaxy.”
Cox emphasizes the Omega Point cosmology is highly speculative and he is not advocating for it as true, but finds it intellectually valuable because it demonstrates that life's cosmic insignificance is not necessarily inevitable.
“I emphasize this is complete, you know, it's beyond speculative, so I'm not advocating for this position that that's the way that nature is. But it's really interesting, it was really interesting to me to just think about it. The point, I think, the key point, which is interesting, is that it's not necessarily the case that life remains insignificant on a cosmic scale.”
We have a responsibility to the cosmos itself because we are a product of 13.8 billion years of cosmic evolution and might be a very rare and special product, even though we will only be here for a small amount of time on cosmic timescales.
“if that's the case, we have a responsibility to the cosmos itself because, you know, we're a product of 13.8 billion years of cosmic evolution, but we might be a very rare and special product. But we might only be here for a small amount of time. The Sun will only be here for a small amount of time in cosmic timescales...”
The central challenge in managing emerging technologies (space, artificial intelligence, quantum computing) is building adequate regulatory frameworks; historically, humanity is poor at addressing global challenges cooperatively.
“The challenges, as with all new technologies... come when we try to build the regulatory framework... challenges about the management of space, or the management of artificial intelligence, or the management of the power of potentially quantum computers, I think ultimately are global challenges. And we are very bad historically at facing global challenges together.”
A sufficiently advanced civilization could theoretically achieve technological mastery at multiple scales: building cities on Mars, terraforming Mars, traveling to moons of Jupiter or Saturn, reaching the edge of the solar system, and even (purely theoretically) affecting the lifetime of the Sun.
“We could imagine building cities on Mars. We could imagine in physics, pure physics terms, terraforming Mars, turning it into a habitable world. We could imagine going to the moons of Jupiter or Saturn. We could imagine going to the edge of the solar system. You could even, could you imagine technology in a million years, let's say, that would allow us to begin to affect the lifetime of the Sun?”
Reflecting on humanity's physical insignificance (atoms on a mote of dust orbiting one star among billions in a galaxy among trillions), it is natural to conclude that humans don't matter, but this inference may be incorrect.
“When we contemplate the size and the scale of the universe...we're little specks of just a collection of atoms on one mote of dust, orbiting around one little star in 400 billion stars in one galaxy, amongst 2 trillion galaxies, in a small patch of a potentially infinite universe. So clearly it is true, we are physically insignificant. So...it is very natural for us to tend to come to the conclusion that we don't matter at all. And it is true in some sense, just physically what are we?”
The Chandrasekhar limit calculation exemplifies a beautiful piece of physics: it shows that the maximum mass of collapsing matter held up by quantum mechanical effects depends only on fundamental properties of the universe (strength of gravity, Planck's constant, speed of light) and is independent of details about stellar composition.
“I find it profoundly important. It's a beautiful, beautiful result, because what we're saying is that you can calculate the maximum mass of a load of stuff that can hold itself up through this quantum mechanical process. And it just depends on these fundamental properties of the universe...that's it. So it's a very, very beautiful calculation.”
David Deutsch and earlier Barrow & Tipler in 'The Anthropic Cosmological Principle' argue that life need not remain eternally insignificant on cosmic scales; intelligent life could, through technological advancement, influence larger structures from planets to solar systems to galaxies.
“I was reading a book, it's a very old book now by David Deutsch, who is one of the greats, one of the founders of quantum computing... And he made a point, which I had heard before actually in a book called 'The Anthropic Cosmological Principle' by John Barrow and Frank Tipler... David Deutsch, and Barrow and Tipler pointed out that it's not necessarily the case that life will always be a spec, right? Something that's very valuable and local in the universe, but doesn't make much difference on a cosmic scale. It's not necessarily the case, because you can imagine... that life could play a central role in the far future of the universe.”
We are experiencing a revolution in space access due to the development of reusable rockets by SpaceX and Blue Origin, making access to Earth orbit cheap and enabling the beginning of a space-faring civilization.
“we are now, I think, on the verge of becoming a space fairing civilization, in the truest sense of the word...because now we have reusable rockets. So SpaceX, now Blue Origin, have reusable rockets, which means that access to earth orbit is cheap, or at least cheaper than it's ever been before.”
If human civilization is rare, then humanity may have a responsibility to the cosmos itself, since we are a product of 13.8 billion years of cosmic evolution and may be a rare and special outcome of that process.
“if that's the case, we have a responsibility to the cosmos itself because, you know, we're a product of 13.8 billion years of cosmic evolution, but we might be a very rare and special product.”
As space access becomes commercialized, new problems emerge: competition for orbital real estate, potential collisions between satellites, and lack of international coordination mechanisms; air-traffic-control-like frameworks are needed but difficult to establish across different national interests.
“when you start to move outwards to a new frontier, then the frontier can become crowded...What happens if someone's satellite comes close to another satellite? How do you manage that? Do you allocate particular orbits? Or do you say that we're gonna have some framework like air traffic control...That framework is not yet there...it's a challenge, because, of course, it's always a challenge when different countries and different commercial interests...are trying to flesh out agreements.”
David Deutsch and earlier thinkers (John Barrow and Frank Tipler) pointed out that life need not remain insignificant; it is not necessarily the case that civilizations will always be small and locally confined rather than cosmically influential.
“I found, it happened to me recently. I was reading a book...by David Deutsch...And he made a point, which I had heard before actually in a book called 'The Anthropic Cosmological Principle' by John Barrow and Frank Tipler...But David Deutsch...and Barrow and Tipler pointed out that it's not necessarily the case that life will always be a spec, right? Something that's very valuable and local in the universe, but doesn't make much difference on a cosmic scale.”
If a proton were expanded to the size of our solar system (to Neptune's orbit), something the size of a Planck length would expand to the size of a virus or living cell, illustrating that the ratio between Planck length and a cellular nucleus is the same as the ratio between a proton and a solar system.
“if you take a proton and expand it to the size of our solar system, so imagine that, the nucleus of a hydrogen atom, and you imagine expanding that to the size of our solar system, out to the orbit of Neptune, then something that's the Planck length would extend or expand to let's say a virus or a living cell. So the ratio in size between the Planck length and a cell...is the same ratio as a proton to the solar system.”
On timescales of millions to billions of years, an expanding civilization with advancing knowledge could potentially influence stellar lifetime and, over cosmic timescales, could theoretically become powerful enough to affect the universe's fundamental fate.
“You could even, could you imagine technology in a million years, let's say, that would allow us to begin to affect the lifetime of the Sun? Could you imagine that? In physics terms, according to laws of physics, I suppose you could...And then you go a million years, 2 million years, 3 million years, 10 million years, a billion years into the future, imagine that our civilization expands to the stars, and becomes an interstellar civilization. Imagine our civilization populates the entire galaxy. There's nothing in the laws of physics that prevent that.”
Space expansion allows civilization to grow without further damaging the Earth, the planet most people will live on for the foreseeable future, making space exploration existentially important for human wellbeing and environmental protection.
“I think there's a tremendous opportunity there to grow our civilization crucially, without further damaging the planet that most of us will live on for the foreseeable future. And that's why, for me, I'm ultimately optimistic about those steps that we are making into space.”
Satellite technology (navigation, communications, weather forecasting, climate observation) has been essential to modern civilization for decades, but accessibility to low Earth orbit has historically been expensive, limiting applications and development.
“Of course, it's been very important to us for many years, decades in fact. So satellite navigation, communications, weather forecasting, earth observation, climate observation, and so on. The observation of Earth from Earth orbit has been part of our lives, whether we think about it or not, for quite some time. But now, because we have the technology to access it cheaply...”
Quantum mechanics grew out of attempts to describe the structure of matter—atoms and molecules—though their structure was unknown in 1900 and only became clear later with the discovery of the atomic nucleus.
“quantum mechanics is, I suppose, grew out of an attempt to describe matter, the structure of matter to understand atoms and molecules. Although it's worth saying that atoms and molecules in the way we conceive of them today were not known to exist, or the structure of them was not known in 1900.”
Observable universe radius is roughly 46 billion light-years, but this is not the edge of the universe; the universe likely extends beyond what we can observe, and may be infinite in extent, making claims about the universe's total size impossible to verify given current knowledge.
“Even that, so you might say, well, the universe is then, the radius of the universe is, what, 92 billion light years or so. It isn't because we know, we know that there's more universe beyond that. That's just as far as we can see. The universe, for all we know, and given the accuracy of our measurements at the moment might be infinite in extent.”
Satellite technology has been crucial for decades: GPS navigation, communications, weather forecasting, Earth observation, and climate monitoring all depend on satellites in orbit, and low-cost access is accelerating these capabilities.
“satellite navigation, communications, weather forecasting, earth observation, climate observation, and so on. The observation of Earth from Earth orbit has been part of our lives... for quite some time... because we have the technology to access it cheaply, I think we are seeing a revolution.”
Quantum mechanics grew out of an attempt to describe the structure of matter, specifically atoms and molecules, though the structure of atoms was not known to exist in 1900.
“quantum mechanics is, I suppose, grew out of an attempt to describe matter, the structure of matter to understand atoms and molecules. Although it's worth saying that atoms and molecules in the way we conceive of them today were not known to exist, or the structure of them was not known in 1900.”
Cox is ultimately optimistic about humanity's steps into space because cheaper access to orbit appears to be happening faster than he previously imagined—he would not have expected such rapid rocket reusability advances 20 years ago.
“I mean, I would not have imagined, I think, if you went back 20 years that we would be, we would have so many rockets flying, and coming back to the Earth again, and then flying again. Perhaps within my lifetime, but certainly at this point in the 21st century. So I think it's exciting...”
The most distant observable galaxies detected by instruments like the James Webb Space Telescope show light that has traveled for over 13 billion years, from when the universe was much younger, mapping cosmic history.
“We've measured galaxies now out to close to the edge of the observable universe with instruments like the James Webb Space Telescope, from which the light has journeyed for over 13 billion years to reach us.”
A light year is the distance light travels in one year at 186,000 miles per second, and the nearest star (Proxima Centauri) is about four light years away.
“Four times further than that, you get to the nearest star, the Proximus Centura, the Alpha Centauri system. That's about four light years away or so. So that's inconceivable. Light traveling 186,000 miles a second, 186,000 miles a second, four years to the nearest star.”
Planck's constant (h) is a fundamental constant of nature that appears in the relationship E = hf (energy equals Planck's constant times frequency), linking the energy of a light packet (photon) to its frequency.
“the fundamental constant of nature that we associate with quantum mechanics, now known as Planck's constant, appears in the calculation... Planck found he was able to describe the experimental data if he assumed that light is emitted in little packets, and the relationship of the energy of the little packets, the photon as we would now call it, to the frequency of the light is E = hf, where f is the frequency of the light, E is the energy of the packet, and h is this new constant of nature that we now know as Planck's constant.”
Max Planck's 1900 proposal that hot objects emit light in discrete packets (photons) rather than continuously across all wavelengths was a revolutionary leap that solved the calculation problem for blackbody radiation; Planck initially conceived this as a mathematical trick rather than a description of physical reality.
“In 1900, Max Planck made a revolutionary proposal... he famously came up with the idea that a hot object only emits light in little packets, which subsequently we came to know as photons... he didn't really at the time think that it was, he thought it was a calculational device.”
A quantum object (such as an electron) can exist in a superposition of states—for example, a quantum coin can be in a state where it is simultaneously 30% heads and 70% tails or any other mixture—rather than having a definite classical state.
“a quantum coin could indeed have the property that it would be heads or tails. But the difference between quantum mechanics and classical theory is that an object like a coin, a quantum coin can also be in what we call a super position of heads and tails. So that means that it can be in a state where it is, let's say, if we observe the thing, we'll talk about that a bit later, but it can be in a state where it could be 30% heads and 70% tails, or 40% heads and 60% tails, or any combination, any mixture of heads and tails.”
The standard quantum mechanical calculation method involves assigning a complex number (picturable as a clock face with magnitude and angle) to every possible path a particle can take; summing these over all paths and taking the squared magnitude gives the probability to find the particle at any point on the detection screen.
“you can assign, calculate what's called a complex number for every route that the particle, the electron can take from gun through the slits to the screen... A complex number, for those that don't know about complex numbers, can be pictured as a little clock face. So a complex number has a clock hand, there's a length of the clock hand, and there's the time on the clock face... you calculate how those clock faces kind of evolve and change and spin around from the moment the electron's emitted to the moment it hits the screen. And the prescription is very simple. You can calculate what those clock faces look like, what those complex numbers are, and every point on the screen, you have to take them all, every possible path to that point and just add them up. And the length of the clock hand gives you the probability to find the electron there.”
In a two-qubit entangled system, there are 4 possible combinations (up-down, down-up, up-up, down-down); for a three-qubit system there are 8; for an n-qubit system there are 2^n possible configurations that all represent valid quantum states.
“So there are, you've got these two things, which can be up or down. There are four possible combinations of that system... For a three qubit system, you think about it, ups and downs, you'll find out there are eight possible combinations... For four qubits, then it's two to the power four, there's 16 possible combinations.”
The double-slit experiment is the single best encapsulation of all the properties and 'weirdness' of the quantum world, and the best description of it is freely available in the Feynman Lectures on Physics volume three, first chapter.
“If you look at pretty much any book on quantum mechanics, there is one experiment which you can describe... It's called the double slit experiment... I'll strongly recommend, I think it's almost universally accepted, the best description of the double slit experiment is freely available. It's in the Feynman Lectures, volume three, first chapter.”
The speed of light is a fundamental constant of nature: everything massless travels at this speed, nothing with mass can accelerate to reach it, and it represents a universal speed limit derived from the geometry of spacetime.
“the speed of light... although we can talk about what it is in meters per second, or miles per hour, or whatever it is, it is a property of the universe. Everything that is massless travels at the speed of light, this speed, whatever it is. And if you have any mass at all, you cannot travel, you cannot accelerate to this speed, a universal speed limit.”
Newton's gravitational constant measures the strength of the gravitational force between objects or, in Einstein's theory, how matter and energy distort the fabric of spacetime.
“the strength of the gravitational force... in Einstein's theory, a deeper description, how does a particular amount of matter or energy distort the fabric of the universe? The number that tells you about that is Newton's gravitational constant, which was first measured back in the 1780s, 1790s.”
Planck's constant represents a fundamental limit on how accurately we can simultaneously know the position and momentum of a particle: the product of position uncertainty and momentum uncertainty must be greater than Planck's constant.
“there's a fundamental limit on how accurately we can know the position of a particle and the momentum of a particle. You can't know them both with absolute precision. There's a fundamental limit, and it's around about Planck's constant... the uncertainty on the measurement of the position of something multiplied by the uncertainty on the measurement of the momentum of something is always has to be greater than Planck's constant.”
A star is material (mainly hydrogen and helium) that collapses under its own gravity, heating the core until nuclear fusion reactions commence, which release energy creating pressure that holds up the star—a balance between gravitational collapse and fusion-driven pressure.
“a star is some material, it's mainly hydrogen and helium collapsing under its own gravity... gravity is trying to squash this thing down... the core heats up... the hydrogen and the helium is wriggling around very fast, and ultimately you switch on nuclear fusion reactions in the core... the fusion reactions... release energy, which creates a pressure, which holds the star up. So the star's a balancing act.”
The Sun is 93 million miles (1 AU) from Earth; a passenger aircraft flying around the Sun's diameter (about 100 times Earth's radius) would take roughly a year, illustrating the Sun's vast scale relative to human-built objects.
“the so-called astronomical unit, 93 million miles... You can fit a million Earths inside the Sun... The radius is something like 100 times the radius of the Earth... it'd take something like months, I think something like a year to fly around the sun in a passenger aircraft.”
The Andromeda galaxy, visible to the naked eye on dark nights, is our nearest large galactic neighbor at 2.5 million light years away, appearing on the sky as a disc roughly the size of the full moon despite this distance because it is extremely large.
“our nearest neighboring large galaxy. It's called the Andromeda galaxy... That galaxy is two and a half million light years away... you can see it with the naked eye because it's so big... it's about the diameter of a full moon on the sky, and that's two and a half million light years away, because it's a big thing.”
Carl Sagan's metaphor that humanity is taking 'first steps out into the cosmic ocean' and 'the water seems inviting' captures the opportunity and excitement of space expansion as a natural extension of human exploration.
“as the great Carl Sagan said, we're beginning to take our first steps out into the cosmic ocean. And I always remember, and he said, 'The water seems inviting.'”
The nearest star, Proxima Centauri, is about 4 light-years away; light traveling at 186,000 miles per second takes 4 years to traverse this distance, and comprehending such distances is inconceivable for the human mind.
“Four times further than that, you get to the nearest star, the Proximus Centura, the Alpha Centauri system. That's about four light years away or so. So that's inconceivable. Light traveling 186,000 miles a second, 186,000 miles a second, four years to the nearest star.”
The speed of light is a property of the universe defining a universal speed limit; no massless object travels faster than light and no massive object can be accelerated to light speed, reflecting something deep about the geometry of spacetime.
“the speed of light...Everything that is massless travels at the speed of light, this speed, whatever it is. And if you have any mass at all, you cannot travel, you cannot accelerate to this speed, a universal speed limit. So it's something deep about the property of the universe.”
Historical units of measurement like the meter and foot are ultimately based on human biology and evolutionary history (related to arm length, foot size, and the gravitational and cellular constraints of Earth), rather than reflecting fundamental properties of the universe.
“historically they're based on properties of the human body, so they're based on biology really. So a meter might be, you know, the length of this kind of length, and a foot is kind of that kind of length...It tells us about biology on earth, and how we've evolved on this planet, and how big cells are ultimately, I suppose, and how many cells you need to make an intelligent multicellular being like a human, based on the fact that we live on this planet with this particular gravitational force.”
Newton's gravitational constant (G) measures the strength of the gravitational force between objects of particular mass, or in Einstein's theory, how matter and energy distort the fabric of spacetime.
“the strength of the gravitational force. So what is the force between two objects of a particular mass? Or in Einstein's theory, a deeper description, how does a particular amount of matter or energy distort the fabric of the universe? The number that tells you about that is Newton's gravitational constant.”
Planck's constant sets a fundamental limit on the precision with which one can simultaneously know the position and momentum of a particle; the product of position uncertainty and momentum uncertainty must be greater than Planck's constant (Heisenberg's uncertainty principle).
“there's a fundamental limit on how accurately we can know the position of a particle and the momentum of a particle. You can't know them both with absolute precision. There's a fundamental limit, and it's around about Planck's constant...the uncertainty on the measurement of the position of something multiplied by the uncertainty on the measurement of the momentum of something is always has to be greater than Planck's constant.”
The Sun's diameter is approximately 100 times Earth's radius, such that if one flew around it in a passenger aircraft, the journey would take on the order of a year, demonstrating how difficult it is to comprehend the size of even modest stellar objects.
“The radius is something like 100 times the radius of the Earth...If you got in a passenger aircraft...you can fly from London to New York, you know, how long that is, a few thousand miles. What does that diameter of the Sun mean? Well, it'd take something like months, I think something like a year to fly around the sun in a passenger aircraft.”
Carl Sagan noted that humanity is taking first steps into the cosmic ocean and 'the water seems inviting,' suggesting tremendous opportunity in space exploration and expansion.
“as the great Carl Sagan said, we're beginning to take our first steps out into the cosmic ocean. And I always remember, and he said, 'The water seems inviting.' So it's a tremendous opportunity.”
If civilization continues advancing and understanding deepens regarding quantum gravity and spacetime structure, entirely new powers might become available that we cannot currently conceive.
“imagine that our civilization starts to understand the quantum theory of gravity, we start to understand how space time works. Imagine if we start to glimpse some underlying structure in reality that gives us power that we've not yet dreamed of. Who knows in a billion years?”
The observable universe extends to approximately 46 billion light-years in radius (the comoving distance to the cosmic microwave background), but this is not the edge of the universe—the universe may extend far beyond what we can observe and could be infinite.
“where is that place now? The place that emitted that photon from the cosmic microwave background radiation, that came across the universe for 13.8 billion years into our detectors, where is it now? 'Cause the universe has been expanding. You get an answer, which is something like 46 billion light years away now... And even that, so you might say, well, the universe is then, the radius of the universe is, what, 92 billion light years or so. It isn't because we know, we know that there's more universe beyond that. That's just as far as we can see. The universe, for all we know, and given the accuracy of our measurements at the moment might be infinite in extent.”
The Milky Way galaxy contains between 200 and 400 billion stars and is about 100,000 light years across, a typical size for a large galaxy.
“the Milky Way galaxy... Somewhere between 200 and 400 billion suns in the Milky Way galaxy, about 100 thousand light years across. And that's a fairly typical size for a large galaxy.”
Voyager 1 is now over 150 AU from Earth (150 times Earth-Sun distance), with light taking over 22 hours to reach it, representing the most distant human-created object in communication with us, though it barely marks the edge of the Oort Cloud.
“the most distant object that we created, we built, the Voyager 1 spacecraft is now well over 150 astronomical units from the Earth... It takes light over 22 hours to reach it... that's just about, by some definition, the edge of our solar system.”
The Voyager 1 spacecraft is now over 150 astronomical units from Earth, and light takes over 22 hours to reach it; it is near the edge of the solar system but not at the true edge (which extends to the Oort Cloud, perhaps a light-year out based on the Sun's gravitational influence).
“the most distant object that we created, we built, the Voyager 1 spacecraft is now well over 150 astronomical units from the Earth...it takes light over 22 hours to reach it...by some definition, the edge of our solar system. Although actually, if you talk in terms of these icy objects in what's called the Kuiper belt and the Oort Cloud, it's really not the edge of our solar system at all. We think that that extends maybe a light year out into the universe.”
The Milky Way galaxy contains between 200 and 400 billion stars and is approximately 100,000 light-years across, making it a fairly typical size for a large galaxy; light requires 100,000 years to traverse it at 186,000 miles per second.
“a galaxy then, the Milky Way galaxy...Somewhere between 200 and 400 billion suns in the Milky Way galaxy, about 100 thousand light years across. And that's a fairly typical size for a large galaxy. One galaxy, one island of stars, 100 thousand years for light to cross it at 186,000 miles per second.”
The cosmic microwave background radiation is light emitted 380,000 years after the Big Bang that has been traveling for 13.8 billion years to reach Earth; though emitted from a region much closer, that region is now approximately 46 billion light-years away due to cosmic expansion.
“the cosmic microwave background radiation is light that was emitted 380,000 years after the Big Bang...that's been traveling for 13.8 billion years or so across the universe to reach us...if you ask the question, where is that place now?...where is it now? 'Cause the universe has been expanding. You get an answer, which is something like 46 billion light years away now, 46 billion.”
Cox emphasizes that the Omega Point cosmology and related ideas are highly speculative and beyond current evidence, and he is not advocating for them as true descriptions of nature, but rather noting that they represent intellectually interesting possibilities about life's potential cosmic role.
“Now, I emphasize this is complete, you know, it's beyond speculative, so I'm not advocating for this position that that's the way that nature is. But it's really interesting, it was really interesting to me to just think about it.”
Reading David Deutsch's work on quantum computing reminded Cox of ideas from Barrow and Tipler's 'The Anthropic Cosmological Principle,' which had influenced him as an undergraduate, showing how engagement with others' ideas can reshape one's thinking.
“I found, it happened to me recently. I was reading a book... by David Deutsch... And he made a point, which I had heard before actually in a book called 'The Anthropic Cosmological Principle' by John Barrow and Frank Tipler... which was a huge influence on me when I was an undergraduate physicist, so I couldn't believe I'd forgotten this point.”
Cox is ultimately optimistic about humanity's expansion into space and doubts he would have imagined 20 years ago that we would have numerous rockets flying and returning to Earth repeatedly for reuse.
“I'm ultimately optimistic about those steps that we are making into space... I mean, I would not have imagined, I think, if you went back 20 years that we would be, we would have so many rockets flying, and coming back to the Earth again, and then flying again.”
Our sense of distance breaks down for scales much larger than distances we can travel on Earth; while we can conceive of hundreds of miles by car travel, the intuitive grasp fails for distances of millions or billions of miles across space.
“when we start to talk about distances that are much larger than distances that we might travel on the surface of the earth, then I think our feel for those distances begins to break down...a few thousand miles you can picture because you can get on an aircraft and fly across the Atlantic.”