This collection gathers David MacKay’s own words from his books Sustainable Energy – Without the Hot Air and Information Theory, Inference, and Learning Algorithms. — Sustainable Energy - Without the Hot Air (David MacKay, free edition).

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Part 1: The Importance of Numbers and Arithmetic

  1. On emotional energy debates: David MacKay: "Twaddle emissions are high at the moment because people get emotional (for example about wind farms or nuclear power) and no-one talks about numbers." — Sustainable Energy - Without the Hot Air (David MacKay, free edition).
  2. On numbers, not adjectives: David MacKay: "To make this comparison, we need numbers, not adjectives." — Sustainable Energy - Without the Hot Air (David MacKay, free edition).
  3. On twaddle: David MacKay: "I’m concerned about cutting UK emissions of twaddle – twaddle about sustainable energy." — Sustainable Energy - Without the Hot Air (David MacKay, free edition).
  4. On numbers chosen to impress: David MacKay: "Numbers are chosen to impress, to score points in arguments, rather than to inform." — Sustainable Energy - Without the Hot Air (David MacKay, free edition).
  5. On being pro-arithmetic: David MacKay: "Please don’t get me wrong: I’m not trying to be pro-nuclear." — Sustainable Energy - Without the Hot Air (David MacKay, free edition).
  6. On innumerate codswallop: David MacKay: "We are inundated with a flood of crazy innumerate codswallop." — Sustainable Energy - Without the Hot Air (David MacKay, free edition).
  7. On a plan that adds up: David MacKay: "We need a plan that adds up!" — Sustainable Energy - Without the Hot Air (David MacKay, free edition).

Part 2: Energy Reality and Misconceptions

  1. On every little helps: David MacKay: "A more realistic mantra is: if everyone does a little, we’ll achieve only a little." — Sustainable Energy - Without the Hot Air (David MacKay, free edition).
  2. On effective servants: David MacKay: "The number of kilowatt-hours per day you use is thus the effective number of servants you have working for you." — Sustainable Energy - Without the Hot Air (David MacKay, free edition).
  3. On the solar panel myth: David MacKay: "Manufacturing a solar panel consumes more energy than it will ever deliver. False." — Sustainable Energy - Without the Hot Air (David MacKay, free edition).

Part 3: Renewables, Physics, and Limits

  1. On the countryside: David MacKay: "My main reason for feeling such a panelling of the country would be implausible is that Brits like using their countryside for farming and recreation rather than solar-panel husbandry." — Sustainable Energy - Without the Hot Air (David MacKay, free edition).
  2. On wind turbines paying back: David MacKay: "Wind turbines with a lifetime of 20 years have an energy yield ratio of 80." — Sustainable Energy - Without the Hot Air (David MacKay, free edition).
  3. On covering the country with windmills: David MacKay: "What fraction of the country can we really imagine covering with windmills?" — Sustainable Energy - Without the Hot Air (David MacKay, free edition).
  4. On electric vehicles: David MacKay: "Electric vehicles can deliver transport at an energy cost of roughly 15 kWh per 100 km." — Sustainable Energy - Without the Hot Air (David MacKay, free edition).
  5. On the laws of physics: David MacKay: "Trees are carbon-capturing systems; they suck CO2 out of thin air, and they don’t violate any laws of physics." — Sustainable Energy - Without the Hot Air (David MacKay, free edition).
  6. On an energy yield ratio above one: David MacKay: "An energy yield ratio bigger than one means that a system is A Good Thing, energy-wise." — Sustainable Energy - Without the Hot Air (David MacKay, free edition).
  7. On getting off fossil fuels: David MacKay: "We’ve found that it’s hard to get off fossil fuels by living on our own renewables." — Sustainable Energy - Without the Hot Air (David MacKay, free edition).
  8. On pumped storage: David MacKay: "Pumped-storage facilities equal to 400 Dinorwigs can completely replace wind for a national lull lasting 2 days." — Sustainable Energy - Without the Hot Air (David MacKay, free edition).

Part 4: Nuclear Power and Real-World Trade-offs

  1. On nuclear not being infinitely dangerous: David MacKay: "Nuclear power is not infinitely dangerous." — Sustainable Energy - Without the Hot Air (David MacKay, free edition).
  2. On horror at nuclear danger: David MacKay: "At the same time, we must not let ourselves be swept off our feet in horror at the danger of nuclear power." — Sustainable Energy - Without the Hot Air (David MacKay, free edition).
  3. On half-measures: David MacKay: "I am worried that we won’t actually get off fossil fuels when we need to." — Sustainable Energy - Without the Hot Air (David MacKay, free edition).
  4. On carbon sequestration: David MacKay: "Carbon sequestration companies are not thriving, even though the advice from climate experts and economic experts alike is that sucking carbon dioxide from thin air will very probably be necessary to avoid dangerous climate change." — Sustainable Energy - Without the Hot Air (David MacKay, free edition).
  5. On clean coal: David MacKay: "We could get off fossil fuels by investing in “clean coal” technology." — Sustainable Energy - Without the Hot Air (David MacKay, free edition).

Part 5: Information Theory and Machine Learning

  1. On unifying information theory and machine learning: David MacKay: "Why unify information theory and machine learning? Because they are two sides of the same coin." — Information Theory, Inference, and Learning Algorithms (MacKay, Cambridge University Press 2003; free on-screen edition).
  2. On brains: David MacKay: "Brains are the ultimate compression and communication systems." — Information Theory, Inference, and Learning Algorithms (MacKay, Cambridge University Press 2003; free on-screen edition).
  3. On shared tools: David MacKay: "The state-of-the-art algorithms for both data compression and error-correcting codes use the same tools as machine learning." — Information Theory, Inference, and Learning Algorithms (MacKay, Cambridge University Press 2003; free on-screen edition).
  4. On perfect compression: David MacKay: "The output of a perfect compressor is always perfectly random bits." — Information Theory, Inference, and Learning Algorithms (MacKay, Cambridge University Press 2003; free on-screen edition).
  5. On asymptotic equipartition: David MacKay: "I put the words ‘asymptotic equipartition’ in quotes because it is important not to think that the elements of the typical set TNβ really do have roughly the same probability as each other." — Information Theory, Inference, and Learning Algorithms (MacKay, Cambridge University Press 2003; free on-screen edition).
  6. On assumptions in inference: David MacKay: "Advocates of a Bayesian approach to data modelling and pattern recognition do not view this subjectivity as a defect, since in their view, you cannot do inference without making assumptions." — Information Theory, Inference, and Learning Algorithms (MacKay, Cambridge University Press 2003; free on-screen edition).
  7. On the correct solution to an inference problem: David MacKay: "The correct solution to an inference problem is found using Bayes’ theorem." — Information Theory, Inference, and Learning Algorithms (MacKay, Cambridge University Press 2003; free on-screen edition).
  8. On high dimensions: David MacKay: "Now consider two Gaussian densities in 1000 dimensions that differ in radius σW by just 1%, and that contain equal total probability mass." — Information Theory, Inference, and Learning Algorithms (MacKay, Cambridge University Press 2003; free on-screen edition).

Part 6: Bayesian Inference and Occam's Razor

  1. On Occam's razor: David MacKay: "Bayesian methods can assign objective preferences to the alternative models in a way that automatically embodies Occam’s razor." — Information Theory, Inference, and Learning Algorithms (MacKay, Cambridge University Press 2003; free on-screen edition).
  2. On where sampling theory fails: David MacKay: "As we will now see, there are also inference problems where sampling theory fails to detect ‘significant’ evidence where a Bayesian approach and everyday intuition agree that the evidence is strong." — Information Theory, Inference, and Learning Algorithms (MacKay, Cambridge University Press 2003; free on-screen edition).
  3. On the second level of inference: David MacKay: "What is not widely appreciated is how a Bayesian performs the second level of inference; this chapter will therefore focus on Bayesian model comparison." — Information Theory, Inference, and Learning Algorithms (MacKay, Cambridge University Press 2003; free on-screen edition).
  4. On the Occam factor: David MacKay: "The magnitude of the Occam factor is thus a measure of complexity of the model; it relates to the complexity of the predictions that the model makes in data space." — Information Theory, Inference, and Learning Algorithms (MacKay, Cambridge University Press 2003; free on-screen edition).
  5. On early stopping: David MacKay: "An ad hoc solution to overfitting is to use early stopping, that is, use an algorithm originally intended to minimize the error function G(w), then prevent it from doing so by halting the algorithm at some point." — Information Theory, Inference, and Learning Algorithms (MacKay, Cambridge University Press 2003; free on-screen edition).

Part 7: Education, Teaching, and Clear Thinking

  1. On understanding by creating: David MacKay: "You can understand a subject only by creating it for yourself." — Information Theory, Inference, and Learning Algorithms (MacKay, Cambridge University Press 2003; free on-screen edition).
  2. On understanding as a creative process: David MacKay: "Understanding is a creative process." — Sustainable Energy - Without the Hot Air (David MacKay, free edition).
  3. On optional chapters: David MacKay: "All chapters of Part III are optional on a first reading, except perhaps for Chapter 16 (Message Passing)." — Information Theory, Inference, and Learning Algorithms (MacKay, Cambridge University Press 2003; free on-screen edition).
  4. On cybernetics: David MacKay: "In the 1960s, a single field, cybernetics, was populated by information theorists, computer scientists, and neuroscientists, all studying common problems." — Information Theory, Inference, and Learning Algorithms (MacKay, Cambridge University Press 2003; free on-screen edition).

Part 8: The Scale of the Challenge

  1. On imagining living sustainably: David MacKay: "Never mind when fossil fuels are going to run out; never mind whether climate change is happening; burning fossil fuels is not sustainable anyway; let’s imagine liv- ing sustainably, and figure out how much sustainable energy is available.” However, climate change has risen into public consciousness, and it raises all sorts of interesting back-of-envelope questions." — Sustainable Energy - Without the Hot Air (David MacKay, free edition).
  2. On the cost of fixing climate change: David MacKay: "If the true cost of fixing climate change were £40 per person then the government could fix it with the loose change in the Chancellor’s pocket!" — Sustainable Energy - Without the Hot Air (David MacKay, free edition).
  3. On renewables alone: David MacKay: "It’s not going to be easy to make a plan that adds up using renewables alone." — Sustainable Energy - Without the Hot Air (David MacKay, free edition).
  4. On the solution to climate change: David MacKay: "Solving climate change is a complex topic, but in a single crude brushstroke, here is the solution: the price of carbon dioxide must be such that people stop burning coal without capture." — Sustainable Energy - Without the Hot Air (David MacKay, free edition).