Human centered physics, Part I
May 29, 2011 § 1 Comment
Physics is a human-centered science. Imagine, for example, that we had an extremely accurate 3D stereovision system that allowed direct visual perception of the relative distances of the moon, planets and the stars in the sky. This kind of an exceptional human capacity would have totally changed the history of classical and modern astronomy and physics.
Simply by looking at the sky, even the prehistoric men had seen that the moon is quite near to us, compared to a few other relatively close by celestial objects, the planets, of which only two had been seen to come between us and the sun and the rest of them always further from the sun. The first men would have been less susceptible to the moon illusion. Most of the stars would twinkle somewhere far, far away and it would have been everyday knowledge that the stars don’t travel around the earth. These perceptions would have led to another kind of development in natural sciences.
One might take this as an insignificant story of science fiction or a fairy tail. But some may know that 3D stereo maps of about 100 000 stars have already been created by the observations of the Hipparcos satellite http://www.rssd.esa.int/index.php?project=HIPPARCOS and you can even buy a 3D star atlas so that with stereo glasses you can directly view the (scaled) relative locations of a number stars and galaxies (cf. Monkhouse & Cox, 2000).
There is more than meets the eye in this specific example of 3D stereovision. We can even ask, what if our other sensory-perceptual systems were totally unlike they are now? How would it have affected the development of physics? What kind of instruments, measures and theories of the world had been developed for the purpose of intelligent living and clever science? What about aliens having totally different sensory (if they had such properties) systems?
Celestial 3D stereovision?
Realistic biologists and opticians might argue that such a 3D stereovision system is not simply possible in the human head where the eye separation is just too small for the observation of extremely large 3D distances. It is true that we use our stereovision for rather near observations in our personal space and in accurate manipulation of objects.
But we can imagine a biological system with an extremely accurate visual (iconic) memory and a 3D stereo processing capacity that could have an effective depth perception even for stellar relative distances (just like the Hipparcos satellite does). It would combine the image sensed when the earth is at one extreme position on its trajectory around the sun with the image of the same object observed at the opposite side of the trajectory. This would function as an immense stereoscope with an artificial between-the-eyes distance of about 150 000 000 km that would provide a magnificent celestial 3D stereovision through the space. Possible or not, the thought experiment is eye opening: any kind of sensory systems can be theoretically constructed. The stereoscope in the photo is from the early 20th century France.
Had we possessed this valuable capacity for 3D vision, our knowledge of the universe had certainly progressed faster and Ptolemy, Copernicus, and Galilei had been puzzled by other celestial problems; perhaps totally different skills and talents would have been valuable in natural sciences. Giordano Bruno could have survived, or at least be murdered for completely other reasons by the Roman inquisition. Indeed, the capacity limitations of our senses have had significant social and cultural consequences as well.
Sensory determinants of physics
Other similar thought experiments can be inspiring: what were the consequences for the physical theory formation that distances were measured with stick standards? What about the impact of other “natural” standards constructed and used, for example, for estimating the weight of objects or the passing of time? Originally they all were invented in order to compensate for our sensory limitations. Can a physicist neglect these simple human constrains and assume that they have not guided physics at all or that it is only a matter of transformation from one domain to another?
It is rather surprising that such serious thought experiments are not more popular among theoretical physicists. A delightful exception is George Gamow’s Mr. Tompkins in Wonderland, published in 1946 where he entertains the idea and considers and all its relativistic consequences for our world and experiences if the speed of light were only 30 miles/hr.
It would be creative fun to write a fairy tale of a physics professor in a world where human vision had an extremely accurate spectral sensitivity, visual-spatial resolution better than an electron microscope, and 3D vision with a better depth resolution than that of the Hipparcos satellite. This physics professor would not lecture about the discovery of the spectral redshift in the stars, everyone would know the phenomenon. He could go directly into its interpretation with the help of the basic astronomical 3D-depth knowledge.
We will always need a grounding theory of observation, not only in the form of fairy tales – because when seriously taken, it is one of the eternal tasks of mankind in trying to understand our perception of the world and ourselves. The knowledge building in classical and modern physics has been profoundly constrained by the limiting capacities of the human sensory observation processes and measurement systems have been invented for compensating for this lack of objectivity. Hence, all physical measures and the theories derived from them are inherently human-centric, and the results of our observation mechanics. The measurement stick in the photo is from my grandfather, and perhaps originally from his father.
It is not an accident that pointers have been found useful as indicators in a number of measuring instruments: human visual sensitivity to object position is one of our best sensory abilities. While these considerations may sound like superficial perceptual speculation, it is possible to show that they have serious consequences for any physical theory building.
Frogs and the theory of the universe
Had the frog a similar brain like ours, but still possessing its known derivative eyes that are sensitive to spatial and temporal changes in the environment, it would have created another kind of physics than we have today. For example, for a frog, a meter stick “is not there” unless it moves, vibrates back and forth or it is visually flashed on and off.
The human vision has similar limitations since images stabilized on the retina disappear within a few seconds but luckily our eyes move constantly and prevent this peculiar kind of biological blindness. If they did not move, a stationary meter stick would have little value as an instrument for measuring the length of a fabric, unless it was waved back-and-forth to keep it visible, which would make the measurement of the fabric – also moved around – quite a challenge.
What is especially problematic about the frog’s eyes is that they are derivative or transient sensors but they are by no means linear instruments. Hence, the theory of the universe created by the frog (with a human brain) would not be a simple linear transformation from ours. It is an exercise of high ambiguity to try to derive a physical theory that is testable by instruments and measures that are relevant to the frog, and then to build a theory of the universe based on this minute difference between man and the frog.
We could use the frog or some other “model animal” in the same way that pharmacologists and brain scientists use animal models in trying to understand the human mind. But above all, we should build a theory of observation that includes a general observer (an alien) and a general world.
In the following I have shortly speculated how the human sensory properties have constrained the theory formation and practices of physics. It is imaginable that the development of physical measures was an evolutional, human and social process including at least the following steps:
- Cost/benefit analysis was apparently the first step in the invention of any possible measurement system, typically based on economical calculations like securing minimum losses in measuring the amount of materials sold or minimum engineering cost of the errors made in its use.
- Sensory amplification is an operation used in many forms of physical measurement, for example in the use of measurement sticks, scales, compasses, and ammeters. Showing the position of a pointer relative to a suitably marked background makes the positional reading accurate: our visual system is extremely good in such comparison tasks. A standard measurement stick functions in the same way. For a scientist frog, however, he pointers would be visible only when they are moving.
- Perceptual transformation from one sensory domain to another. A fascinating example is from the China, about 200 BC. A system to measure the amount of liquid filled into a barrel of fixed size and form, was accomplished by using a set of reference barrels filled with known amounts of liquid and hitting alternatively both the barrel being filled and the reference with a bat and listening to the sounds generated. Equal sounds meant equal amounts of liquid, wine for example. This was a case of deriving a physical measure based on perceptual transformation from one sensory domain (perception of volume in which we are not very good) to another (perception of sound differences in which we are relatively good). The gains made by the measurement system boosted its use and standardization. This mode of physical measurement is not untypical for modern physics either. The famous Wilson cloud chamber was used for detecting particles from ionizing radiation as visible tracks that could be photographed and measured. Again, a scientist frog had not been happy with such poorly visible measures and it would have invented dynamic arrangements, which of course, would have led to early consideration of the complex temporal dynamics of the observed particles. We can also ask how much different other chamber inventions – compared against the presently available ones – would have been created by the brainy frogs?
- Combination of sensory domain information. The speed of sound was difficult to measure during the times of Newton when suitable chronometers were not available. Newton used a simple pendulum method that you can still try today in the same corridor in Cambridge where he attached a nail, like a thumbtack in the sole of his shoe. Having the swinging pendulum with a known time constant hanging from his hand, walking in the corridor towards its distant wall, listening to the sound from the nail hitting the stone floor and then echoing with a delay from the distant wall, and observing the phase of the pendulum when hearing the two temporally separated sounds, he could estimate the speed of sound when he knew the distances. He made a measurement error of about 10% by this subjective method. It relied on sensory transformation by combing the sensory observation between sensory domains: visual position, timing, and the sound. In this case, across sensory channels comparison made an accurate physical measurement possible.
An evident question now arises: could novel physical theories be invented by changing the way the basic physical entities and measures are defined? Is it possible to build a physics of alternative realities that are as true as our present ones, but from a different perspective, the perspective of a known or general theoretical observer, a frog, alien, or man? Would it make any sense? Could mathematicians be offended by these human-centric thoughts about our knowledge of nature – perhaps not, they might even be inspired by them.