„What it takes to produce a gravitational repulsion is a negative pressure. According to general relativity, it turns out... both pressures and energy densities can produce gravitational fields, unlike Newtonian physics, where it's only mass densities that produce gravitational fields.“

—  Alan Guth, Lecture 1: Inflationary Cosmology: Is Our Universe Part of a Multiverse? Part I.
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Albert Einstein photo

„We shall therefore assume the complete physical equivalence of a gravitational field and a corresponding acceleration of the reference system.“

—  Albert Einstein German-born physicist and founder of the theory of relativity 1879 - 1955
Statement of the equivalence principle in Yearbook of Radioactivity and Electronics (1907)

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William Crookes photo

„It is curious that the popular conceptions of evil and malignant beings are of the type that would be produced by increased gravitation“

—  William Crookes British chemist and physicist 1832 - 1919
Context: It is curious that the popular conceptions of evil and malignant beings are of the type that would be produced by increased gravitation — toads, reptiles, and noisome creeping things — while the arch fiend himself is represented as perhaps the ultimate form which could be assumed by a thinking brain and its necessary machinery were the power of gravitation to be increased to the highest point compatible with existence — a serpent crawling along the ground. On the other hand, our highest types of beauty are those which would be common under decreased gravitation. The "daughter of the gods, divinely tall," and the leaping athlete, please us by the slight triumph over the earthward pull which their stature or spring implies.

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Otto Lilienthal photo

„All flight is based upon producing air pressure, all flight energy consists in overcoming air pressure.“

—  Otto Lilienthal German aviation pioneer 1848 - 1896
Der Vogelflug als Grundlage der Fliegekunst (1889); English edition: Birdflight As The Basis of Aviation (1911).

Richard Feynman photo

„We can deduce, often, from one part of physics like the law of gravitation, a principle which turns out to be much more valid than the derivation.“

—  Richard Feynman American theoretical physicist 1918 - 1988
Context: Now we have a problem. We can deduce, often, from one part of physics like the law of gravitation, a principle which turns out to be much more valid than the derivation. This doesn't happen in mathematics, that the theorems come out in places where they're not supposed to be! chapter 2, “ The Relation of Mathematics to Physics http://www.youtube.com/watch?v=M9ZYEb0Vf8U” referring to the law of conservation of angular momentum

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Marshall McLuhan photo

„To say that a body or its gravitational field 'bends in space' in its vicinity is the discuss visual space in acoustic terms.“

—  Marshall McLuhan Canadian educator, philosopher, and scholar-- a professor of English literature, a literary critic, and a communicat... 1918 - 1980
p. 40

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