Gravity's Bias for Left May be Writ in the Sky


A Liberal in Lakeview's picture

Thanks for posting the link to a very interesting diversion from politics. That stated, I hope that the theoreticians do not formulate a correct theory of quantum gravity during our lifetimes. The record of history teaches very clearly what the usual suspects will do with the knowledge once they get enough government funding for their projects. This world would become much more dangerous. And besides, a TQG would do the average person little good, for he has little knowledge of the mathematics needed to understand such a theory and not even enough gumption to learn the rudiments of special relativity.

I can already imagine secular humanists (like those in a skeptics group I joined in Jan.) gnashing their teeth in anger about my comments if they were to read them. Immediately they'd be telling me about my opposition to science, about how I don't want advances for computer technology or medicine, yada yada.

On a related note, how about posting an article that explains how the vector of gravitational acceleration could be directed vertically downward on Earth, as entry level physics textbooks claim, even though we know that upward acceleration, as in a rocket or in an elevator, increases the g load on the passengers? In fact, it would compare three reference frames for a person

(i) standing on Earth (or the Moon, or Mars, etc.),
(ii) accelerating in Einstein's space elevator, or in a rocketship, and
(iii) standing on the inside of the rim of a large, rotating, wheel-shaped space station, like the one in 2001: A Space Odyssey.

Take (ii), for example, as a rocket is leaving its launch pad. As the rocket accelerates upward, the g load on an astronaut's body increases in proportion to the magnitude of upward acceleration. One briefly feels just such an increase when riding an elevator that starts to move up, although the acceleration soon drops to zero as the elevator reaches its maximum upward velocity. The implication is that the vectors of terrestrial gravity and of the rocket's acceleration are additive. However, if on Earth the vector of g were directed downward, as claimed in the entry level physics texts, its sign would be negative; the sign on the rocket's acceleration would still be positive nevertheless.

So, if g on Earth were directed downward, accelerating a body upward in the rocket should make that person feel as if gravity were diminished. (In fact, upward acceleration of 9.8 m/s/s would make the astronaut feel weightless.) This theoretical result contradicts experience, thus on Earth the vector of g points up, not down. The normal force, which those physics texts add to balance the force of gravity, points down or is simply ficticious. In fact, it seems the authors add that normal force (usually designated F sub N) to avoid silly questions about why gravity doesn't cause an object to accelerate upwards from the ground.

When one falls off a chair or the ledge of a building, one can treat the ground as if it were accelerating upward; that person, however, experiences weightlessness, as do astronauts training in the vomit comet. (We need to ignore the resistance of air in the case of the person falling off the building. But you could put him in a tall vacuum chamber to test the principle.) Far out in space, reference frame (ii) would require no normal force to explain the force that the astronauts experience as if it were gravity. That gravitylike sensation is supplied by the rockets. In (iii), the vector of centripetal acceleration is directed from the rim to the hub, and anyone standing on the inside of the rim enjoys artificial gravity. There, too, no normal force is needed to complete the explanation. Finally, for (i), curvature of space resolve the paradox of the vector of g being pointed upwards on opposite sides of the planet while at the same time stationary bodies on the surface remain at a fixed distance from each other.