Author Archives: sanhei

Symmetry of matter seems impossible

I am not a physicist, so the following may be my misunderstanding. Symmetry seems theoretically impossible, except at one instant. If there was a perfectly symmetric piece of matter (after rotating or reflecting it around some axis, the set of locations of its atoms would be the same as before, just a possibly different atom in each location), then in the next instant of time, its atoms would move to unpredictable locations by the Heisenberg uncertainty principle (the location and momentum of a particle cannot be simultaneously determined). This is because the locations of the atoms would be known by symmetry in the first instant, thus their momenta unknown.

Symmetry may not provide complete information about the locations of the atoms, but constrains their possible locations. Such an upper bound on the uncertainty about locations puts a lower bound on the uncertainty about momenta. Momentum uncertainty creates location uncertainty in the next instant.

Symmetry is probably an approximation: rotating or reflecting a piece of matter, its atoms are in locations close to the previous locations of its atoms. Again, an upper bound on the location uncertainty about the atoms should put a lower bound on the momentum uncertainty. If the atoms move in uncertain directions, then the approximate location symmetry would be lost at some point in time, both in the future and the past.

Less inspiring people in universities than in early school

A student claimed that fewer inspiring people are found in universities than in early school. Empirical checks of this would be interesting and would need a measure of inspiringness. A theoretical explanation is a tradeoff between multiple dimensions: subject matter competence, integrity, reliability, communication skills, being inspiring, etc. The tradeoff is on both the demand and the supply side. An inspiring competent person has many career options (CEO, politician, entrepreneur) besides academia, so fewer such people end up supplying their labour to the education sector.

On the demand side, a university has to prioritise dimensions on which to rank candidates and hire, given its salary budget and capacity constraints on how many job positions it has. Weighting competence more leaves less emphasis on inspiringness. Competing universities may prioritise different dimensions (be horizontally differentiated), in which case on average each institution gets candidates who have more of its preferred dimension and less of other dimensions.

As a side note, what an organisation says its priorities are may differ from its actual priorities, which are evidenced by behaviour, e.g., who it hires. It may say it values teaching with passion, but hire based on research success instead.

A constraint is a special case of a tradeoff. Suppose that given the minimum required competence, an employer wants to hire the most inspiring person. The higher this level of competence (teaching PhD courses vs kindergarten), the fewer people satisfy the constraint. At a high enough level of the constraint, there may be insufficient candidates in the world to fill all the vacant jobs. Some employers cannot fill the position, others will have just one candidate. Maximising inspiringness over an empty set, or a set of one, is unlikely to yield very inspiring people.

It may be inherently simpler to inspire with easier material, in which case even with equally inspiring people throughout all levels of education, the later stages will seem less inspiring.

Larger leaps through theory may be required as a subject gets more advanced, leaving less scope for inspiring anecdotes and real-life examples. The ivory tower is often accused of being out of touch with common experience. Parting with everyday life is partly inevitable for developing any specialised skill, otherwise the skill would be an everyday one, not specialised.

If inspiring people requires manipulating them, and more educated individuals resist manipulation better, then inspiring people gets more difficult with each level of education. Each stage of study selects on average the more intelligent graduates of the previous stage, so if smarter people are harder to manipulate, then those with higher levels of education are harder to inspire. On the other hand, if academics are naive and out of touch with the ways of the world, then they may be easier to manipulate and inspire than schoolchildren.

People accumulate interests and responsibilities in their first half of life. The more hobbies and duties, the less scope for adopting a goal proposed by some charismatic person, i.e., getting inspired by them. Later in life, many goals may have been achieved and people may have settled down for a comfortable existence. They are then less inclined to believe the need to follow a course that an inspiring person claims is a way of reaching their goals.

Receive-only mode for phones to save power

Airplane mode cuts off all or non-wifi communication, which is undesirable. Receive-only mode would allow receipt of texts and recorded messages, save power and prevent detection of the phone by radio frequency methods (not by a metal detector). If the phone is stationary, then there is no need for it to send periodic keep-alive or hand-off signals to the cell phone tower. The phone’s accelerometer and GPS receiver can detect with reasonable accuracy whether it stays in the same cell tower’s range. Only when the phone moves a large enough distance will sending hand-off or check-in signals become necessary.

Location can also be detected using the radio receiver of the phone (which every phone has for calls and texts) if multiple cellphone towers are in range – just triangulate. A saved map of tower coverage areas in the phone helps position the phone and detect when the phone moves to a different tower’s area.

A software modification should be enough to create a receive-only mode: turn off sending (supplying power to the antenna) but keep receiving (measure and record the voltage and current in the antenna). Add optional deactivation of the receive-only mode based on the accelerometer and GPS detecting the phone moving out of range of the current cell tower.

Recumbent bicycle bunny hop in theory

I have not tried this, so it is just speculation. There are many claims online that a recumbent bike cannot be bunny hopped. However, lifting the front wheel should be possible while sitting on the bike, because lifting the front caster of an office chair is possible without touching the floor. Lean forward, then slam your torso back against the backrest – careful that you don’t tip over backward. Your legs may be lifted or the feet may rest on top of the “spider” at the bottom of the chair.

On a recumbent, a further boost comes from suddenly pedalling hard in low gear, which accelerates the rear wheel forward and under, rotating the front wheel up around the pivot of the rear wheel.

Lifting the rear wheel of a recumbent should be possible while seated, because popping your butt off the floor when sitting with straight legs is possible without using your leg muscles. Put your fists on the floor slightly behind and to the side of your hips. Bend your elbows, then suddenly straighten them, pushing explosively against the floor. Your butt and your fists lift a few inches. Keep your legs locked straight. Very strong people can do this with legs lifted (in boat pose: body in V-shape with only the butt and fists touching the floor).

Because lifting each wheel is possible and the movements do not directly oppose each other, a recumbent should be bunnyhoppable. Lift first the front and then the rear wheel.

Contraception increases high school graduation – questionable numbers

In Stevenson et al 2021 “The impact of contraceptive access on high school graduation” in Science Advances, some numbers do not add up. In the Supplementary Material, Table S1 lists the pre-intervention Other, non-Hispanic cohort size in the 2010 US Census and 2009 through 2017 1-year American Community Survey data as 300, but Table S2 as 290 = 100+70+30+90 (Black + Asian + American Indian + Other/Multiple Races). The post-intervention cohort size is 200 in Table S1, but 230 in Table S2, so the difference is in the other direction (S2 larger) and cannot be due to the same adjustment of one Table for both cohorts, e.g. omitting some racial group or double-counting multiracial people. The main conclusions still hold with the adjusted numbers.

It is interesting that the graduation rate for the Other race group is omitted from the main paper and the Supplementary Material Table S3, because by my calculations, in Colorado, the Other graduation rate decreased after the CFPI contraception access expansion, but in the Parallel Trends states (the main comparison group of US states that the authors use), the Other graduation rate increased significantly. The one missing row in the Table is exactly the one in which the results are the opposite to the rest of the paper and the conclusions of the authors.

Animal experiments on whether pose and expression control mood

Amy Cuddy promoted power poses which she claimed boosted confidence and success. Replication of her results failed (the effects were not found in other psychology studies), then succeeded again, so the debate continues. Similarly, adopting a smiling expression makes people happier. Measuring the psychological effects of posture and expression is complicated in humans. For example, due to experimenter demand effects. Animals are simpler and cheaper to experiment with, but I did not find any animal experiments on power poses on Google Scholar on 28.03.2021.

The idea of the experiment is to move the animal into a confident or scared pose and measure the resulting behaviour, stress hormones, dominance hormones, maybe scan the brain. Potentially mood-affecting poses differ between animals, but are well-known for common pets. Lifting a dog’s tail up its back is a confident pose. Moving the tail side to side or putting the chest close to the ground and butt up in a “play-with-me bow” is happy, excited. Putting the dog’s tail between the legs is scared. Moving the dog’s gums back to bare its teeth is angry. Arching a cat’s back is angry. Curling the cat up and half-closing its eyes is contented.

The main problem is that the animal may resist being moved into these poses or get stressed by the unfamiliar treatment. A period of habituation training is needed, but if the pose has an effect, then part of this effect realises during the habituation. In this case, the measured effect size is attenuated, i.e. the pre- and post-treatment mood and behaviour look similar.

A similar experiment in people is to have a person or a robot move the limbs of the participants of the experiment into power poses instead of asking them to assume the pose. The excuse or distraction from the true purpose of the experiment may be light physical exercise, physical therapy or massage. This includes a facial massage, which may stretch the face into a smile or compress into a frown. The usual questionnaires and measurements may be administered after moving the body or face into these poses or expressions.

Improving the accuracy of waist circumference measurement

Waistline needs to be measured for clothes size determination and health evaluation, but the instructions to do it are vague: keep the stomach neutral, neither sucked in nor bulged out, hold the measuring tape not too loosely nor too tight. A person’s waist expands and contracts with the breath, so at which point of the breath cycle should the measurement be taken? How much tension should the measuring tape have?

Averaging several measurements would be more accurate than a single vaguely defined one, both in the sense of replication across different measurers and in the sense of corresponding to the physical quantity of interest (health status, tightness of the clothes). One simple way is to average the measured perimeter of a maximally sucked-in gut and a maximally pushed-out gut.

A better measure, but quite difficult to take, is to average the waist circumference across the whole cycle of breathing in and out, for several cycles. A device to do this would be a loop of flexible measuring tape pulled into a roll by a spring, similarly to a construction measuring tape made of metal. The roll would contain electronics which continuously record how much tape is in the roll, therefore the length of the loop outside the roll. The length data could be averaged to obtain the average waistline.

A more modern method is to use two cameras pointed at the person from two sides at waist height, recording a 3D video of the waist over the breath cycle. The video could then be averaged on a computer to find the mean volume. Whole-body volume could be determined similarly – no need for Archimedes’ Eureka method of submerging the body in a bathtub with a volume scale on it. The volume and the weight determine the density of the body, which gives partial information about its fat percentage.

Paying pharmaceutical firms for capacity is problematic

Castillo et al. 2021 (doi:10.1126/science.abg0889) make many valid points, e.g., vaccine production should be greatly expanded using taxpayer money because the quicker recovery from the pandemic more than pays for the expansion. Castillo et al. also suggest paying pharmaceutical manufacturers for the capacity they install instead of the quantity they produce. The reasoning of the authors is that producers are delaying installing capacity and the delivery of their promised vaccine quantities to save costs and to supply higher-paying buyers first, because the penalties for delaying are small. Producers refuse to sign contracts with larger penalties.

What the authors do not mention is that the same problems occur when paying for capacity. In addition, the capacity needs to be monitored, which is more difficult than checking the delivered quantity. Before large-scale production, how to detect the „Potemkin capacity” of installing cheap production lines unsuitable for large quantities? The manufacturer may later simply claim technical glitches when the production line does not work. Effective penalties are needed, which in turn requires motivating the producer to sign a contract containing these, just like for a quantity contract.

Paying in advance for capacity before the vaccine is proven to work insures firms against the risk of failure, as Castillo et al. say. The problem is that such advance payment also attracts swindlers who promise a miracle cure and then run with the money – there is adverse selection in who enters the government’s capacity contract scheme. Thus capacity contracts should be restricted to firms with a good established reputation. However, vaccines from innovative entrants may also be needed, which suggests continuing to use quantity contracts at least for some firms. If the law requires treating firms equally, then they should all be offered a similar contract.

Identifying unmeasurable effort in contests

To distinguish unmeasurable effort from unmeasurable exogenous factors like talent or environmental interference in contests, assumptions are needed, even for partial identification when overall performance can be objectively measured (e.g., chess move quality evaluated by a computer). Combining one of the following assumptions with the additive separability of effort and the exogenous factors provides sign restrictions on coefficient estimates. Additive separability means that talent or the environment changes performance the same way at any effort level.

One such identifying assumption is that effort is greatest when it makes the most difference – against an equal opponent. By contrast, effort is lower against much better and much worse opponents.

A similar identifying assumption is that if there is personal conflict between some contest participants but not others, then effort is likely higher against a hated opponent than a neutral one.

The performance of a given contestant against an equal opponent compared to against an unequal one is a lower bound on how much effort affects performance. Similarly, the performance against a hated rival compared to against a neutral contestant is a lower bound on the effect of effort. The lower bound is not the total influence of effort, because even against an unequal neutral opponent, effort is still positive.

Computer vision training sets of photos are endogenous

In principle, every pixel could be independent of any other, so the set of possible photos is the number of pixels times the number of colours – billions at least. No training data set is large enough to cover these photo possibilities many times over, as required for statistical analysis, of which machine learning is a subfield. The problem is solved by restricting attention to a small subset of possible photos. In this case, there is a reasonable number of possible photos, which can be covered by a reasonably large training data set.

Useful photos on any topic usually contain just one main object, such as a face, with less than 100 secondary objects (furniture, clothes, equipment). There is a long right tail – some useful photos have dozens of the main object, like a group photo full of faces, but I do not know of a photo with a thousand distinguishable faces. Photos of mass events may have ten thousand people, but lack the resolution to make any face in these useful.

Only selected photos are worth analysing. Only photos sufficiently similar to these are worth putting in a computer vision training dataset. The sample selection occurs both on the input and the output side: few of the billions of pixel arrangements actually occur as photos to be classified by machine vision and most of the training photos are similar to those. There are thus fewer outputs to predict than would be generated from a uniform random distribution and more inputs close to those outputs than would occur if input data was uniform random. Both speed learning.

When photo resolution improves, more objects of interest may appear in photos without losing usefulness to blur. Then such photos become available in large numbers and are added to the datasets.