Einstein's Fridge Quotes

“Thus Tyndall made it clear as long ago as the 1860s that human industrial activity could affect the climate. That is why, as early as 1917, Alexander Graham Bell, the great technologist and inventor of the telephone, was advocating the use of solar power to mitigate the possible dangers of unabated burning of fossil fuels.”
― Paul Sen, Einstein's Fridge: How the Difference Between Hot and Cold Explains the Universe

“So, in summary, plants use the Gibbs free energy in sunlight to turn water and carbon dioxide into carbohydrates that contain some of the original solar free energy, while releasing oxygen. Animals access the Gibbs free energy trapped in carbohydrates to live and, by so doing, recombine the carbon in the carbohydrates with atmospheric oxygen to emit carbon dioxide and water. Scientists have now accounted for every single transfer of Gibbs free energy in all the chemical processes that occur in plants and animals and overall. A beautiful symmetry is at work here. Plants take in 2,870 kilojoules of solar free energy to make 180 grams of glucose (a typical carbohydrate). An animal that eats 180 grams of glucose releases exactly 2,870 kilojoules of free energy, eventually breathing out carbon dioxide.”
― Paul Sen, Einstein's Fridge: How the Difference Between Hot and Cold Explains the Universe

“The idea that the same amount of heat causes a greater change of entropy in a cold place than a hot one can seem strange. But consider this as an analogy: A noisy, crowded pub is next to a quiet library. Five rowdy people leave the pub. The din drops but by an indiscernible amount. The five stumble into the library. The noisiness there increases noticeably. When a group of raucous people enter a quiet place, the increase in disruption there is much greater than its fall in the boisterous place from which they came.”
― Paul Sen, Einstein's Fridge: How the Difference Between Hot and Cold Explains the Universe

“As Stephen Hawking wrote, “We are just an advanced breed of monkeys on a minor planet of a very average star. But we can understand the Universe. That makes us something very special.”
― Paul Sen, Einstein's Fridge: How the Difference Between Hot and Cold Explains the Universe

“It’s as if our universe is “an inside-out black hole.” Instead of stuff flowing inward across a one-way boundary never to be seen again, stuff is flowing outward across a one-way boundary never to be seen again. That means that, like the event horizon surrounding a black hole, there is an event horizon around our universe. The denouement of this argument? Just as all the information needed to describe everything that’s fallen into a black hole is encoded on the surface of its event horizon, it could be that all the information needed to describe everything that exists in our universe is encoded on the two-dimensional surface of the horizon that surrounds it. That would suggest that the three-dimensional universe that we perceive is an illusion. It’s just the way we experience the real two-dimensional universe. The universe we see is like a hologram, a three-dimensional shadow of a two-dimensional reality.”
― Paul Sen, Einstein's Fridge: How the Difference Between Hot and Cold Explains the Universe

“This has led physicists to compare the event horizon of a black hole to a hologram. These are two-dimensional surfaces that contain all the information needed to generate a complete three-dimensional image. These aren’t like the 3D images one sees in the cinema, which create an illusion of three dimensions. One can walk in a circle around a hologram of an object and it will appear as if one is walking in a circle around the actual three-dimensional object. Yet all the information needed to create the image is stored on a flat piece of film. This so-called holographic principle has led physicists to suggest that the two-dimensional information on the black hole’s event horizon is in a sense more “real” than the three-dimensional stuff that has fallen into it because the event horizon is still accessible to our part of the universe while whatever has fallen in is lost forever. And the conclusion this brings us to is even more extraordinary: it could be that all the information that describes our universe is stored on the two-dimensional surface shell that surrounds it.”
― Paul Sen, Einstein's Fridge: How the Difference Between Hot and Cold Explains the Universe

“Hawking and Bekenstein had shown that the three great ideas of modern physics—general relativity, quantum mechanics, and thermodynamics—work in harmony. For these reasons, black hole entropy and radiation have come to dominate contemporary physics as scientists search for a so-called grand unified theory, the Holy Grail of a single principle that explains nature—the world, the universe, everything—at its most fundamental level.”
― Paul Sen, Einstein's Fridge: How the Difference Between Hot and Cold Explains the Universe

“Hawking surmised that on and just outside the event horizon of black hole this “cancelling out” is disrupted. The extreme curvature of space and time here means some of the negative energy created is torn away from the positive energy that it normally would have annihilated. This positive energy, having survived, is free to radiate away from the black hole. The negative energy falls into it. And because it’s negative energy, it has the effect of making the black hole less massive. To an outside observer, it appears as if the black hole is “evaporating,” slowly shrinking as it emits energy—this is what is referred to as “Hawking radiation.”
― Paul Sen, Einstein's Fridge: How the Difference Between Hot and Cold Explains the Universe

“vacuum energy.” As the name implies, far from being inert, the vacuum is seething with activity. At any instant, bursts of energy appear from nowhere by borrowing equivalent bursts of energy from a tiny instant in the future. Mostly, we are unaware of these fluctuations because the positive burst of energy that appears at one instant is cancelled out by the negative burst that immediately follows it. Negative energy is a strange concept, but it does exist! These energy bursts can appear in many forms. They can appear as particles, such as electrons and positrons, and as photons of electromagnetic energy.”
― Paul Sen, Einstein's Fridge: How the Difference Between Hot and Cold Explains the Universe

“I was afraid that if Bekenstein found out about it, he would use it as a further argument to support his ideas about the entropy of black holes, which I still did not like.” But the more Hawking worked, the more he seemed to be proving Bekenstein right. Not only did black holes radiate heat, but they did so by exactly the amount required if the area of their event horizons was indeed a measure of their entropy. By early 1974, Hawking had developed this work into a fully fledged theory. It led to his now-famous discovery that “Hawking radiation” leaks out of all black holes.”
― Paul Sen, Einstein's Fridge: How the Difference Between Hot and Cold Explains the Universe

“Entropy increases the energy content of the black hole, increasing both its mass and the size of its event horizon. Bekenstein’s argument? Whenever the entropy of a black hole increases, so does the area of its event horizon. In other words, the area of the event horizon of a black hole was not an analogy for entropy, it was a direct measure of its entropy. In Bekenstein’s view, this saved the universal applicability of the second law of thermodynamics. The entropy of the universe always increases, even when things fall into black holes, because the entropy lost from the space outside the event horizon is made up for by an increase in the surface area of the event horizon. Bekenstein called this the generalized second law of thermodynamics, or GSL.”
― Paul Sen, Einstein's Fridge: How the Difference Between Hot and Cold Explains the Universe

“imagine a box full of hot gas, which, of course, has entropy. Now, let’s drop the box past the event horizon of a black hole. Because nothing can come back from across the event horizon, the box has crossed a point of no return and is thus no longer part of our universe. Both the box of gas and the entropy associated with it have disappeared from our universe. But that means that the entropy of our universe has gone down, which directly contradicts the second law of thermodynamics.”
― Paul Sen, Einstein's Fridge: How the Difference Between Hot and Cold Explains the Universe

“The only way for the gas to have zero entropy would be if its molecules were fixed and motionless. But by definition that would also mean their temperature was absolute zero. The point is, if molecules have entropy, they are moving, and they therefore have a temperature. By this reasoning, for a black hole to have entropy, it must, like a gas, have a temperature. And that in turn means that it must radiate heat. But this appears impossible because nothing, including heat, can escape the event horizon.”
― Paul Sen, Einstein's Fridge: How the Difference Between Hot and Cold Explains the Universe

“All objects, from stars and planets to passing spaceships, can fall into a black hole, adding to its mass. As this happens, its pull on the flow of the space around it increases. Therefore, the speed of the “space flow” reaches light speed at a greater distance from the center of a black hole as its mass goes up. The radius of the event horizon grows. But nothing can fall out of a black hole and reduce its mass. Therefore the radius of its event horizon cannot shrink. Hawking spotted an uncanny similarity between this behavior and the behavior of entropy. Both event horizons and entropy never decrease.”
― Paul Sen, Einstein's Fridge: How the Difference Between Hot and Cold Explains the Universe

“So what’s the relevance of this drain hole to a black hole? The analogy works, roughly, as follows: The drain hole sucking water toward it is equivalent to the singularity at the center of a black hole sucking space toward it. Just as water starts to flow faster than the speed of sound at a circle around the center of the drain hole, so too, there is a spherical surface around the singularity at the center of a black hole at which the speed of the flow of space exceeds the speed of light—yes, think here of empty space as you would a flowing liquid. Because no objects or signals in our universe can move through space faster than the speed of light, everything within this spherical surface is doomed to stay within it. Just as Bob could not go back across the sonic boundary because he could not swim faster than the speed at which the water is flowing inward, so, too, anything within the spherical surface around the singularity cannot go back across it.”
― Paul Sen, Einstein's Fridge: How the Difference Between Hot and Cold Explains the Universe

“So the key idea to general relativity is that Newtonian gravity is an illusion. We think the earth is pulling us down with a force. It isn’t. Its mass has curved space in such a way that a straight line in this curved space leads toward the earth’s center.”
― Paul Sen, Einstein's Fridge: How the Difference Between Hot and Cold Explains the Universe

“Some critics claim that scientists, in their desire to explain everything, reduce the wonders of the universe to little more than equations and chemical reactions. To which I say, stand on a beach one day and look at the waves and the patterns of sand dunes through the fingers of your hand. Consider that all these phenomena are connected by the same underlying principles of nature. Consider that all these beautiful patterns emerge from the dissipation of free energy and all start as tiny imperfections.”
― Paul Sen, Einstein's Fridge: How the Difference Between Hot and Cold Explains the Universe

“Turing turned these pessimistic associations on their head, arguing that dissipation didn’t solely cause decay, but could create structure and form. Under certain conditions, he suggested, as certain substances diffuse and spread out, they self-organize into patterned structures. These pattern-creating substances he named morphogens, arguing that as they diffuse through the cells of an embryo, they also shape that embryo.”
― Paul Sen, Einstein's Fridge: How the Difference Between Hot and Cold Explains the Universe

“as a first step, Turing decided to investigate a simplified version of another biological process to see if it could be explained by the actions of a simple chemical “circuit.” His goal was to demonstrate that complex biological behavior could derive from, what deep down, are simple processes.”
― Paul Sen, Einstein's Fridge: How the Difference Between Hot and Cold Explains the Universe

“The paper in Mind demonstrates Turing’s long-term interest in the following question: If “dumb” electrical circuits in a computer could perform mathematical tasks previously only carried out by human minds, was it possible that similar “dumb” processes ultimately underpinned all the ways those minds worked? Though, of course, the components in a brain’s circuit would be interacting chemicals in nerve cells rather than electrical valves and relays.”
― Paul Sen, Einstein's Fridge: How the Difference Between Hot and Cold Explains the Universe

“By measuring how rapidly the cells reproduce and how much energy they consume, they estimate an E. coli uses ten thousand times less energy to process a bit of information than the transistors used in most human-built information-processing devices.”
― Paul Sen, Einstein's Fridge: How the Difference Between Hot and Cold Explains the Universe

“In principle could we build a machine that could think without increasing the entropy of the universe? No, albeit with one caveat. There is an intriguing possibility that if a computer could be built that didn’t need to erase data, it wouldn’t dissipate energy.”
― Paul Sen, Einstein's Fridge: How the Difference Between Hot and Cold Explains the Universe

“This amount is a fundamental limit set by the laws of physics, as fundamental as the law that tells us nothing can travel faster than light. Today it’s called the Landauer limit, and it tells us that however good the technology we create to process bits, once we start erasing those bits, we will make the environment a little warmer.”
― Paul Sen, Einstein's Fridge: How the Difference Between Hot and Cold Explains the Universe

“Szilard emphatically states that this can’t happen for the following reason: The act of measurement by which the demon determines the molecule’s position must cause an increase in entropy that compensates for any decrease in entropy caused as the piston does work.”
― Paul Sen, Einstein's Fridge: How the Difference Between Hot and Cold Explains the Universe

“Is Szilard, with his thought experiment, suggesting that information can do the opposite, overcoming the second law of thermodynamics and turning warm air at a constant temperature into useful work? Such a system would reduce the entropy of the universe because this “free” work could be used to force heat to flow the “wrong” way from cold to hot.”
― Paul Sen, Einstein's Fridge: How the Difference Between Hot and Cold Explains the Universe

“This contradicts the second law of thermodynamics by implying that we wouldn’t need heat to flow from hot to cold to do useful work. With “Szilard’s demon,” we could obtain power from any volume of gas, even if it was at a constant temperature throughout. Indeed, if enough of these “Szilard demons” were unleashed, we could generate all the electricity we needed from the air in the earth’s atmosphere! It seems possible to construct “a perpetual-motion machine,” as Szilard puts it, simply if “one permits an intelligent being to intervene in a thermodynamic system.”
― Paul Sen, Einstein's Fridge: How the Difference Between Hot and Cold Explains the Universe

“He argues later in the same letter to Tait that, yes, if we could detect and exploit the movements of individual molecules, we could reverse the second law. But in reality, such observations would be impossible to achieve. Or as he puts it, “We can’t, not being clever enough.”
― Paul Sen, Einstein's Fridge: How the Difference Between Hot and Cold Explains the Universe

“This understanding of information entropy and redundancy is why we can build the data networks. Take services such as YouTube or Netflix that hold and distribute huge files of video information. These companies reduce the number of bits that make up these files to be as close to their Shannon entropy as possible. This is called compression, and if it weren’t done, the files’ sizes would be too large for our networks. The companies that maintain these networks then add digital redundancy to the compressed files to protect them from noise. These extra bits are a sophisticated electronic version of spelling out a word for clarity over a distorted phone call.”
― Paul Sen, Einstein's Fridge: How the Difference Between Hot and Cold Explains the Universe

“Because the formula he derived for measuring the average number of bits needed to encode a piece of information looked almost exactly like Ludwig Boltzmann and Josiah Willard Gibbs’s formula for calculating entropy in thermodynamics. Here’s Shannon’s equation for calculating the size of any given piece of information: H = –Σi pi logb pi And here’s one way of stating Boltzmann’s equation for calculating the entropy of any given system: S = –kB Σi pi ln pi These two equations don’t just look similar; they’re effectively the same. Shortly after deriving his equation, Shannon pointed the similarity out to John von Neumann, then widely considered the world’s best mathematician. Von Neumann shrugged, suggesting that Shannon call his measure of the number of bits needed to carry a piece of information information entropy on the grounds that no one really understood thermodynamic entropy either.”
― Paul Sen, Einstein's Fridge: How the Difference Between Hot and Cold Explains the Universe

“they didn’t reduce noise levels so much as raise the strength of signals so they were no longer swamped. In both cases, engineers were pumping more energy into the system to overcome the waste of most of it.”
― Paul Sen, Einstein's Fridge: How the Difference Between Hot and Cold Explains the Universe