Galileo and the relativity of space

Some elementary scientific errors appear in Reason in Revolt, which quite undermine the authority of the author. One is an inability to grasp Galileo’s ‘principle of relativity’, confusing it with Einstein’s relativity. Another is to proceed from this failure to the conclusion that modern physics is saturated with “subjective idealism” since, Woods argues, Einstein was always concerned with “the observer” rather than the physical processes taking place independently of any observer in absolute space and time.

Woods misunderstands the term “the observer”, as if Einstein means the particular, subjective viewpoint of an individual, rather than a location from which an objective measurement can be taken.

Copernicus’ revolution

Aristotle’s heavens appeared incorruptible to western astronomers until the seventeenth century when, in 1609, Galileo constructed his telescope. Galileo discovered that there was change in the spheres, because moons orbited Jupiter, and the moon was pitted with craters and

not perfect. This gave rise to a new consciousness among the most advanced thinkers in the Renaissance.

Stars seemed to some to stretch to infinity. But Galileo did not see infinity through his telescope, nor has it ever been seen – only inferred by extrapolation, by the quantitative extension of finite observations.

Galileo defended the Copernican system, which redrew the map of the universe by rearranging the ‘perfect spheres’ so that the sun rather than the earth was at the centre of the solar system.

Nicolaus Copernicus’ famous On the Revolution of the Heavenly Spheres, published in 1543, is thought to have invested the word ‘revolution’ with its ‘revolutionary’ connotations, in the sense of a complete change or an overthrowing of the old conditions.

In his opening remarks, Copernicus briefly contrasted his revolutionary alternative of a universe in which the earth rotates with the old Aristotelian idea of immense but finite heavens which rotate daily round an immobile earth.

Ptolemy of Alexandria (87-150 CE), Copernicus tells us, had asserted that if the earth rotated, “this movement, which would traverse the total circuit of the earth in twenty-four hours, would necessarily be very headlong and of an unsurpassable velocity.” This rotational velocity, Ptolemy says, would have violently torn apart the earth long ago and all the pieces would have “passed beyond the heavens, as is certainly ridiculous”. (On the Revolution of the Heavenly Spheres, book one, Introduction, point eight, pp22-3)

Copernicus replies that the entire world is supposed to revolve once a day around the earth: “Why didn’t [Ptolemy] feel anxiety about the world instead, whose movement must necessarily be of greater velocity?” Would not the much greater rotational movement of the heavenly spheres have torn them apart and thrown them outwards?

Copernicus then asks a quite remarkable question: Have “the heavens become so immense, because an unspeakably vehement motion has pulled them away from the centre, and because the heavens would fall if they came to rest anywhere else?”

This remarkable insight bears comparison with two aspects of the Big Bang theory. Copernicus asks whether the universe is so large because it has expanded from the centre and whether this expansion has prevented the collapse of the heavens, which if they came to rest would be bound to fall back to the centre.

These tentative suggestions remarkably anticipate modern theory. Copernicus seems to present in one brief remark essentially an explanation to the problem of why gravity has not caused the universe to collapse in on itself, a problem which Woods had not fully grasped 450 years later, and an explanation so radical that it was not until the observations of Hubble in 1929-31, which showed that the rapid expansion of the universe would indeed counteract the pull of gravity, that it subsequently struck the scientific world.

Copernicus answers: “[I]f this reasoning were tenable, the magnitude of the heavens would extend infinitely.” Perhaps Copernicus has in mind Aristotle’s potential infinity – that the heavens would go on expanding indefinitely. But if Copernicus means “infinitely” in the sense Woods presents it (Aristotle’s actual infinity), this could only be true if the universe had existed for an infinite period of time. Yet if the universe is expanding “from the centre”, it must have began at some finite point in the past.

Date: 2015-01-11; view: 889