Paul Sen > Quotes

“This prediction was borne out in the late nineteenth century by the arrival of the internal combustion engine, a device that burns petrol or diesel to raise the air temperatures in its cylinders to well over 1,000°. Rudolf Diesel, who published his theories on how to build such an engine in 1893, was inspired by Carnot’s ideas.”
― 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

“at a healthy temperature of around 97°F, human bodies emit detectable infrared waves.”
― Paul Sen, Einstein's Fridge: How the Difference Between Hot and Cold Explains the Universe

“Of thermodynamics Einstein said, “It is the only physical theory of universal content, which I am convinced… will never be overthrown.”
― 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

“How could this be corrected? One way, Carnot argues, is to use atmospheric air as the substance that pushes the piston. Because air contains oxygen, fuel can burn and generate heat inside the cylinder and not in an external boiler as happens in a steam engine.”
― Paul Sen, Einstein's Fridge: How the Difference Between Hot and Cold Explains the Universe

“A like-minded group coalesced with the common mission of bringing the study of living organisms in line with existing research into the inanimate world. In modern terms, they wanted to show that living organisms obeyed the same mathematical, physical, and chemical laws as everything else. However, this approach put Helmholtz and his network in conflict with a large section of the European scientific community who felt such a synthesis of the animate and inanimate worlds was not possible. Many scientists of the day believed in vitalism, the idea that living organisms, in addition to the sustenance they received from food, water, air, and so on, also possessed a “vital,” life-giving force. While an organism was alive, this vital force controlled the physical and chemical processes that took place within it. Logically, therefore, when it died, that vital force disappeared, leaving the dead organism to decay as if it were inanimate. Helmholtz and his friends opposed this “vitalist” view and felt disproving it was a crucial step to putting biology on the same footing as physics and chemistry.”
― Paul Sen, Einstein's Fridge: How the Difference Between Hot and Cold Explains the Universe

“The laws of thermodynamics govern everything from the behavior of atoms to that of living cells, from the engines that power our world to the black hole at the center of our galaxy.”
― Paul Sen, Einstein's Fridge: How the Difference Between Hot and Cold Explains the Universe

“put another way, heat will always dissipate away from a hot region because after a period of random collisions the odds are stacked overwhelmingly in favor of that result. Entropy, by Boltzmann’s reasoning, is simply the number of indistinguishable ways the constituent parts of a system can be arranged. To say entropy increases in any given system is another way of saying that any given system evolves into ever-more-likely distributions or configurations. The second law of thermodynamics is true for the same reason that when a pack of cards arranged in suits is shuffled, it will end up jumbled. There are many more indistinguishable ways for the pack to be disordered than there are for it to end up ordered, and so shuffling takes it in that direction.”
― Paul Sen, Einstein's Fridge: How the Difference Between Hot and Cold Explains the Universe

“For Helmholtz, this type of analysis enabled very different-seeming phenomena—gravity, motion, electricity—to be related to each other quantitatively. Every type of energy has a “best possible” exchange rate into another form of energy, which is embedded in the laws of nature.”
― Paul Sen, Einstein's Fridge: How the Difference Between Hot and Cold Explains the Universe

“Thomson had discovered time’s arrow: it pointed irreversibly from a less dissipated past to a more dissipated future… and once that dissipation is complete, time ends. Thomson had turned a cooling iron bar into a metaphor for the universe. All change in the cosmos was due to pockets of concentrated heat dissipating.”
― Paul Sen, Einstein's Fridge: How the Difference Between Hot and Cold Explains the Universe

“These devices, the ancestors of modern refrigerators, used steam power to pump liquid ether through a coil of tubes that enclosed a chamber containing water. This turned into ice as the ether in the coil evaporated.”
― Paul Sen, Einstein's Fridge: How the Difference Between Hot and Cold Explains the Universe

“Increasing entropy is thus a measure of the decreasing usefulness of heat.”
― Paul Sen, Einstein's Fridge: How the Difference Between Hot and Cold Explains the Universe

“This discovery, way back in 1900, is heralded as the birth of quantum physics. The reason—Planck soon started referring to the chunks of energy absorbed and emitted by oscillating electrons as quanta.”
― Paul Sen, Einstein's Fridge: How the Difference Between Hot and Cold Explains the Universe

“Say disagreed. He considered colonialism to be unprofitable in the long run and instead regarded technological innovation as the key to Britain’s success.”
― Paul Sen, Einstein's Fridge: How the Difference Between Hot and Cold Explains the Universe

“At its heart are three concepts—energy, entropy, and temperature. Without an understanding of these and the laws they obey, all science—physics, chemistry, and biology—would be incoherent.”
― Paul Sen, Einstein's Fridge: How the Difference Between Hot and Cold Explains the Universe

“He reasons that if the flow of heat from a hot place to a cooler one can create motive power and raise a weight, then a machine can exist that does the opposite. In this machine, the motive power obtained from a falling weight will force heat to flow “uphill” from cool sink to hot furnace. There is a direct analogy with water mills and water pumps. The former uses the downward flow of water to produce motive power; the latter uses power to push water uphill.”
― Paul Sen, Einstein's Fridge: How the Difference Between Hot and Cold Explains the Universe

“In summary, to say the entropy of a system increases is to say the heat within it is becoming more widely dispersed.”
― Paul Sen, Einstein's Fridge: How the Difference Between Hot and Cold Explains the Universe

“This logic told Carnot that the real steam engines of his day had to be woefully wasteful. The hottest temperature the steam reached as it expanded and pushed a piston was, Carnot reckoned, a little over 160°C. The coldest it fell to as it condensed was around 40°C. That meant steam engines were extracting motive power from a temperature drop of around 120°C. But the temperature in the engine’s furnace in which the coal was burning was over 1,000°C, and that meant a much-larger temperature drop—of 900°C or more—was being wasted.”
― 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

“Back at the drawing board, Einstein and Szilard came up with their most imaginative idea—a device that worked like a conventional refrigerator, but which had a revolutionary compressor design. Remember this key component warms gaseous coolant and then pumps it into a condenser so it can then release the heat it has absorbed from the refrigerator’s cold interior to the outside air. Unlike a conventional compressor, which used spinning metal blades to work, the Einstein-Szilard device used a varying electromagnetic field, generated by an electric coil, to make liquid metal in a sealed cylinder move back and forth. This motion drove the compressor. The advantage from the safety perspective was that all the potentially dangerous substances—the refrigerator’s coolant and the liquid metal—were permanently contained within stainless steel pipes and cylinders. There was no seal that might become damaged and leak.”
― Paul Sen, Einstein's Fridge: How the Difference Between Hot and Cold Explains the Universe

“Maxwell estimated that these “electromagnetic” waves travel at about 300,000 kilometers per second. Lo and behold, that was remarkably close to measured estimates of the speed of light—too close to be a coincidence. It seemed highly unlikely that light “just happens” to move at the same speed as an electromagnetic wave; it seemed far more likely that light actually is an electromagnetic wave.”
― Paul Sen, Einstein's Fridge: How the Difference Between Hot and Cold Explains the Universe

“The initial temperature difference across the bar, instead of being turned into work, has become “dissipated” heat. It is no longer useful. Thomson stressed that in accordance with the law of energy conservation, no heat is destroyed; but by being distributed differently, by no longer being concentrated in one end of the bar, it has lost its potential to do work. An iron bar equalizing in temperature can therefore be regarded as a heat engine whose efficiency is zero.”
― Paul Sen, Einstein's Fridge: How the Difference Between Hot and Cold Explains the Universe

“Refrigerators, particularly in the domestic setting, exploit the physics of phase changes. Their coolants are chosen from volatile substances that boil at a low temperature of around 4°C. Behind the refrigerator’s inner wall is a network of pipes called an evaporator. The coolant evaporates inside it, sucking heat out of the device’s interior at a constant temperature of 4°C. But then, given that heat never flows spontaneously from cold to hot, how do you get the newly formed coolant gas, which is at a low temperature of 4°, to release its heat into surroundings that are much warmer, typically by 20°?”
― 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

“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

“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

“This “number of distributions” method of defining entropy extends its explanatory power far beyond the dissipation of heat. It readily explains many irreversible processes in nature. For example, air rushes out of an opened balloon, and never back in, because there are many more ways for the air particles to be spread out throughout the room than for them to be crammed inside the balloon. Similarly, there’s no way to stir milk in a cup of tea so it separates instead of mixing because there are many more ways for the milk particles to spread throughout the tea than to be concentrated in one spot.”
― Paul Sen, Einstein's Fridge: How the Difference Between Hot and Cold Explains the Universe

“By assuming that a gas consists of tiny lumps, molecules, that are in constant motion, Boltzmann had showed that its entropy will increase by chance alone. Einstein uses these arguments to show that the way the entropy of light changes can also be explained if it is considered, like a gas, to consist of discrete particles. Just as the air in the room you’re sitting in is made up of tiny particles, so, too, is the light that illuminates it. Having established the particulate nature of light with arguments that mirror Boltzmann’s statistical analysis of a gas, Einstein concludes his paper by showing how this idea can render hitherto unexplained optical behavior “readily understood.”
― Paul Sen, Einstein's Fridge: How the Difference Between Hot and Cold Explains the Universe

“Ludwig Boltzmann, one of the heroes of this story, put it this way: “It must be splendid to command millions of people in great national ventures, to lead a hundred thousand to victory in battle. But it seems to me greater still to discover fundamental truths in a very modest room with very modest means—truths that will still be foundations of human knowledge when the memory of these battles is painstakingly preserved only in the archives of the historian.”
― Paul Sen, Einstein's Fridge: How the Difference Between Hot and Cold Explains the Universe