1937 Description of Lightspeed Travel

After a while I noticed that the sun and all the stars in his neighborhood were ruddy. Those at the opposite pole of the heaven were of an icy blue. The explanation of this strange phenomenon flashed upon me. I was still traveling, and traveling so fast that light itself was not wholly indifferent to my passage. The overtaking undulations took long to catch me. They therefore affected me as slower pulsations than they normally were, and I saw them therefore as red. Those that met me on my hea...

 Unlike Physics, Biology Can't Ignore Information

Physicists love to think about systems that take only a little information to describe. So when they get a system that takes a lot of information to describe, they use a trick called 'statistical mechanics', where you try to ignore most of this information and focus on a few especially important variables. For example, if you hand a physicist a box of gas, they'll try to avoid thinking about the state of each atom, and instead focus on a few macroscopic quantities like the volume and total en...

 Kai Krause: The Uncertainty Principle

Heisenberg’s idea had quickly been dubbed Unschärferelation, which transliterates to “unsharpness relationship,” but as there is really no such term in English ('blurred', 'fuzzy', 'vague' or 'ambiguous' have all been tried), the translation ended up as "the Uncertainty Principle"—when he had not used either term at all (some point to Eddington). And what followed is really quite close to the analogy as well: rather than stating that either position or momentum are "as yet undetermin...

 Scent on an Airless Planet

Scent seems to have all the disadvantages and none of the advantages, as a long-range sense. However, under special circumstances even a modified nose may fill the need. In a story of my own some years ago ("Uncommon Sense," Astounding Science Fiction, September 1945), I assumed an airless planet, so that molecules could diffuse in nearly straight lines. The local sense organs were basically pinhole cameras, with the retinal mosaic formed of olfactory cells. Since the beings in question were ...

 The Trick of Magnifying Normal Creatures

The trick of magnifying a normal creature to menacing size is all too common. The giant amoeba is a familar example; monster insects (or whole populations of them) even more so. It might pay an author with this particular urge to ask himself why we don't actually have such creatures around. There is likely to be a good reason, and if he doesn't know it perhaps he should do some research. In the case of both amoeba and insect, the so-called "square-cube" law is the trouble. Things like streng...

 The Need for an Internal Skeleton

The need for an internal skeleton stems largely from the nature of muscle tissue, which can exert force only by contracting and is therefore much more effective with a good lever system to work with. I belittle neither the intelligence nor the strength of the octopus; but in spite of Victor Hugo and most other writers of undersea adventure, the creature's boneless tentacles are not all that effective as handling organs. I don't mean that the octopus and his kin are helpless hunks of meat; but...

 We Must Think Outside the Rocket Equation

The rocket equation contains three variables. Given any two of these, the third becomes cast in stone. Hope, wishing, or tantrums cannot alter this result. Although a momentum balance, these variables can be cast as energies. They are the energy expenditure against gravity (often called delta V or the change in rocket velocity), the energy available in your rocket propellant (often called exhaust velocity or specific impulse), and the propellant mass fraction (how much propellant you need com...

 Intellectual Exploration as Geographical Exploration

My own field of physics is passing today through a phase of exuberant freedom, a phase of passionate prodigality. Sometimes as I listen to the conversation of my young colleagues at Princeton, I feel as if I am lost in a rain forest, with insects and birds and flowers growing all around me in intricate profusion, growing too abundantly for my sixty-year-old brain to comprehend. But the young people are at home in the rain forest and walk confidently along trails which to me are almost invisib...

 Hawking's Equation

awking has written down an equation which looks rather like Planck's equation. Hawking's equation is S = kA, where S is the entropy of a black hole, A is the area of its surface, and k is a constant which I call Hawking's constant. Entropy means roughly the same thing as the heat capacity of an object. It is measured in units of calories per degree. A is measured in square centimeters. Hawking's equation says that entropy is really the same thing as area. The exchange rate between area and en...

 Plank's Constant

In the year 1900 Max Planck wrote down an equation, E = hv, where E is the energy of a light wave, v is its frequency, and h is a constant which we now call Planck's constant. Planck's equation was the beginning of quantum theory. It said that energy and {22} frequency are the same thing measured in different units. Energy is measured in ergs and frequency in cycles. Planck's constant gives you the rate of exchange for converting frequency into energy, namely, 6 × 10–27 ergs per cycle. B...