Gravity as a thought experiment

Isaac Newton, Professor at Trinity College, London, fled London to escape the twin catastrophies of a recurrent Bubonic Plague outbreak and the later “Fire of London”. Both of which occurred during a 2 year period, 1665-66, during which a third of London’s population died.

To occupy himself during his self-imposed “lockdown”, he compiled his reflections on gravity and related physical phenomena, in a classic work entitled: PRINCIPIA, the foundation of modern physics.

Gravity and light were key parts of his research interests and speculations. It was two centuries and a fraction later that Albert Einstein proposed that both light and gravity were “wave” phenomena and that both were “bent” as they moved through space. Light had been observed to bend and break up into primary colors and wavelengths long before, but gravity was, and is, a continuing mystery in many aspects, even to Einstein.

(Update on gravity reflection: Do Mirrors for Gravitational Waves Exist?; https://arxiv.org/abs/0903.0661, a report from Cornell University, U.S.A.)

Suppose, during the Covid 19 imposed lockdown, we could focus on phenomena such as gravity, and engage in thought experiments which sometimes lead to breakthroughs in science and understanding of our world.

Like most of us, I’m afraid that human nature during this 2020 pandemic and related political opportunism and disfunction have clouded our minds to the point that distraction would be helpful.

Here Goes:

Suppose that, instead of the usual energy hogging metal boxes we move ourselves around in, we used gravity to gently lift our metal boxes off the surface just enough to eliminate the need for wheels or tracks.

Many of you will recognize that this describes an already studied method of doing this, known as “magnetic levitation”. However, this technology requires enormous amounts of electrical energy and infrastructure to implement and operate, so seems to have receded into the archive of brilliant but impractical schemes. Battery-electric vehicles and gyroscopic power systems have their own well-known obstacles to overcome, and neither can function without specific infrastructure and abundant fixed energy suppliers.

All that would be needed for gravity fueled levitation is a means, attached to the “metal box, something like car with no wheels or engine” which needed to be moved around, to reflect the energy already existing between the box and the earth–up to now securing the box to the earth–back to the earth such that the box is lifted sufficiently to enable frictionless movement.

The beauty of harnessing gravity via reflection/deflection is that, exactly as the gravity field between heavy masses and light ones automatically adjusts to whatever the “metal box” earlier mentioned weighs, sufficient spacing to achieve frictionless travel would depend on how it was focussed rather than a need for external power input. Remember Newton’s determination that, absent air resistance, light bodies fall at the same speed as heavy ones.

Of course, any human inside the box would have in mind a destination, rather than some random amusement ride which could turn into something truly terrifying.

Frictionless movement over a level surface could be enabled by nothing more than, say, the cooling fan or turbine used to displace heat from onboard air conditioning for passengers, for example. Of course, some sort of battery or power source would be needed, since vehicle AC compressors typically require 3 to 5 horsepower to operate. Some type of vane or rudder system would be needed to provide directional control as well.

Braking and wind effects on a frictionless land vehicle would be significant engineering challenges once the forward motion systems are sorted out, but if we were able to harness gravity to lift such a vehicle, perhaps we could use the same force to maintain direction despite wind effects and control momentum (braking).

Most urban travel, except for cities like Pittsburg and San Francisco, is typically on fairly level ground. Hills would obviously be a challenge for frictionless vehicles, so summoning up imaginative solutions for that problem would be additional brain teasers.

My speculation on the “ascent” (hill) challenge is to imagine that harnessed gravity to lift “metal boxes” to enable frictionless movement could possibly be finessed to enable ascent of such a frictionless body, since ascent is a similar challenge to gravity with an added horizontal component.

Have you forgotten about pandemics and politics yet?

How about a final word from Professor Newton: