Wednesday, April 08, 2009

Richard Feynman on gravity

The Messenger Lecture about The Law of Gravitation:
Playlist (click, 7 x 8 minutes, play all)
The first minute is black. Then the Cornell Provost introduces RPF in the first part: the lecture takes place in 1964 when Feynman was already happy at Caltech.

In the first part and the early second part, he explains why science is superior over social science and why he would focus on Nature rather than Man. Tycho de Brahe is quoted as the originator of science: his idea was to record the observed positions so accurately that different detailed hypotheses could be compared and/or excluded.

The third part is already dedicated to Kepler's laws. He mentions some theories of that time - that angels were pushing the planets. The theories were almost right, RPF says, except that the angels are actually sitting on another side and are pushing the planets radially. :-)

Applause follows. Of course, the discussion turns to Galileo and inertia. Newton added the forces that can change the straight lines to different paths. The universal law of gravity evolves naturally. A lot of dramatic predictions were made - parameters of orbits, tides, etc. High-precision tests followed: the moons of Jupiter. The first discrepancies (moons ahead of the schedule) were explained by the finite speed of light.

In the fourth part, he explains more examples how new laws can be found by taking the old ones serious: the Neptune was predicted and discovered by the 2nd observatory (that didn't share the arrogant and dumb anti-theorist attitude of the 1st one). ;-) Finally, the Mercury anomalies were fixed by Einstein.

The fifth part discusses how gravity holds clusters of stars together: gravity extends very far. For galaxies, he has no way to check but he has no doubt ;-) that the inverse square law will continue to hold (and no dark matter would be needed haha). Gravity acts on clusters of galaxies, too. Still, gravity doesn't have too many applications, except for scholars' jobs and astrologers. :-) Feynman asks whether he attracts a viewer physically. :-)

In the sixth part, Cavendish-like short-distance tests of gravity are being reviewed. Newton's constant was determined for the first time. Equivalently, the masses of celestial objects - in "small" units from everyday life - were measured. The Eötvös experiments to test the equivalence principle are reviewed. He continues with the electrostatic law that has the same inverse square law and argues that the electro-gravitational unification had not worked so far. The huge discrepancy in their strength (between electrons) is picked as an argument against their unification.

Well, this is pretty much what we call the hierarchy problem these days. The last, seventh part continues with this mystery and suggests that the quintessence solutions don't work. More importantly, he mentions quantum gravity. Feynman says that there was no theory of quantum gravity at that time. He promotes the second lecture, on the link between maths and physics (see the URL below), by suggesting that some people may prefer a "mechanism" over maths.

The laws are often known incompletely. However, Feynman concludes by saying that gravity is pretty because its laws are simple in principle (not necessarily in their manifestations) and universal. Nature only uses the longest strings to weave the patterns. So each small piece of the fabric of the cosmos reveals the organization of the entire tapestry.

And that's the memo.

See also: RPF on the arrow of time, the relationships between maths and physics, fourty-six 1979 lectures, Pleasure of finding things out, and Feynman's 90th birthday where additional links appear.

1 comment:

  1. Gravity Limits Link Ultracold And Superhot,
    Our Inability To Create Singularity

    A. From "Strings Link the Ultracold with the Superhot"
    Perfect liquids suggest theory’s math mirrors something real

    "When the universe was very young, and still superhot from the aftermath of the Big Bang, plasma should have been the only state of matter around. And that’s what scientists at Brookhaven expected to see when they smashed gold ions together at 99.99 percent of the speed of light using a machine called RHIC (for Relativistic Heavy Ion Collider). RHIC physicists thought the ion collisions would melt the gold’s protons and neutrons into a hot plasma of quarks and gluons at a temperature of a trillion kelvins, replicating conditions similar to those a microsecond after the birth of the universe. But instead of a gaslike plasma, the physicists reported in 2005, RHIC served up a hot quark soup, behaving more like a liquid than a plasma or gas."

    B. The expectation of Brookhaven scientists was a bit unrealistic

    The "aftermath of the Big Bang" lasted much less than 10^-35 seconds. This is evidenced by the fact that "Gravity Is THE Manifestation Of The Onset Of Cosmic Inflation Cataclysm" :

    With all respect due to the scientists at Brookhaven it is very difficult to expect that they can recreate the state of pre big-bang energy-mass singularity.

    Commonsense is still the best scientific approach.

    Respectfully suggesting,

    Dov Henis
    (Comments From The 22nd Century)
    EVOLUTION Beyond Darwin 200

    Commonsensible PS To
    Gravity Limits Link Ultracold And Superhot,
    Our Inability To Create Singularity

    A. From "Strings Link the Ultracold with the Superhot"

    A new truth always has to contend with many difficulties,” the German physicist Max Planck said decades ago. “If it were not so, it would have been discovered much sooner.”

    B. IMO gravity is attempted reversal of inflation

    To me, a simple uninformed one, E=mc^2 is a derived formula, whereas E=Total[m(1 + D)] is a commonsensical descriptive concept.

    I intuitively regard both the ultracold and superhot liquids as being in a confined space and "striving but unable" to overcome D, to render D=0.

    I also intuitively regard accelerated collisions smashups as attempted "reverse inflations" in the sense that Newton's law of universal gravitation seems to me as "reverse inflation".

    Dov Henis
    (Comments From The 22nd Century)