Monday, September 13, 2010

Perception of Reality and Mayonnaise

Jack Dikian
March 2010

How a jar of Mayonnaise helped overturn our perception of reality. For hundreds of years, we assumed incorrectly that materials, such as paint and mayonnaise remained viscous due to attractive forces that exist between neutral atoms and molecules.

The long held view that properties of such solutions are determined by van der Waals forces - long-range, attractive forces that exist between neutral atoms and molecules.

In the mid twentieth century the theory that was used to explain van der Waals forces, which had been developed by Fritz London in 1932, did not adequately reflect experimental measurements.

Casimir and Polder working at the Philips Research Laboratories in Eindhoven discovered that the interaction between two neutral molecules could be better described and interpreted in terms of vacuum fluctuations eventually leading to his famous prediction of an attractive force between reflecting plates. That is:-

What happens if you take two mirrors and arrange them so that they are facing each other in empty space?


In the days of classical mechanics the idea of a vacuum was simple. The vacuum was what remained if you emptied a container of all its particles and lowered the temperature down to absolute zero. The vacuum therefore was/is a region that is devoid of matter or put another way - a volume of space that is essentially empty of matter. It’s what comes to mind when we thought about space as we were growing up.

Space is shockingly bizarre

According to quantum mechanics, all fields have fluctuations. That is, at any given moment their actual value varies around a constant, mean value. Even a perfect vacuum has a fluctuating field, the mean energy of which corresponds to half the energy of a photon.

Some 30 years after Paul Dirac formulated the famous Dirac equation, which describes the behavior of fermions and which led to the prediction of the existence of antimatter (however, unable to deal with more than a single electron) Richard Feynman, and others, attempted to take the understanding of the Atom further and help develop the theory of everything.

Their theory, Quantum Electrodynamics (QED) is a far-reaching and more accurate than any previous approximations and underpins almost everything we experience in the physical world – shapes, texture, color, and how everything interacts together.

Here, empty space (a vacuum) buzzes with matter and activity. Here, energy is said to be borrowed from the future and is used in the creation of a particle and an antiparticle. These particles, in turn meet in a fraction of a second and annihilate each other. So energy is borrowed out of nowhere, turned into matter self-destruct and returns back into energy all in a fraction of a second. This is happening everywhere countless times a second.

So according to QED, the everyday matter filling our physical world, the world we see and feel is a kind of left-over from the feverish activities virtual particles get up to in the “empty” void.

Click here to download the complete article

Further reading

M Bordag, U Mohideen and V M Mostepanenko 2001 New developments in the Casimir effect Phys. Rep. 353 1 H B Chan et al. 2001 Nonlinear micromechanical Casimir oscillator Phys. Rev. Lett. 87 211801 F Chen and U Mohideen 2002 Demonstration of the lateral Casimir force Phys. Rev. Lett. 88 101801 C Genet, A Lambrecht and S Reynaud 2000 Temperature dependence of the Casimir force between metallic mirrors Phys. Rev. A 62 012110 S K Lamoreaux 1997 Demonstration of the Casimir force in the 0.6 to 6 micrometer range Phys. Rev. Lett. 78 5 K A Milton 2001 The Casimir Effect: Physical Manifestations of Zero-point Energy (World Scientific, Singapore)

Thursday, September 9, 2010

Popularity, Kids and Social Networks

Jack Dikian


When most kids reach that age where their proficiency with computers and mobile phones is only matched by what may be seen to be an obsession with the social desirability gained through an on-line social life.

Some parents will report that their kids’ on-line social life has taken over their life, and others will reflect on how these social networking sites have become a part of our every day life. It’s been said many times that teenagers consider social networks to be one of the prime avenues of leisure. In addition, teenagers will argue that depriving them of internet access is somewhat similar to that of being deprived of human rights.

From the myriad of interesting phenomena a social psychologist may glean of the role of the social network in mood modulation, social awareness, convenience of communication, educational value, language, social convergence, friendship forming, etc, the element I am particularly interested in is:

The question of perceived popularity in the age of social networking by both the teenager and also his or her parents of them.

We examine factors including:-
  • The concordance in avatars replicating the actual self versus avatars used by teenagers projecting the ideal self.
  • The degree of automatic stereotype activation when confronted by negative feedback.
  • If perceived popularity within the peer group (social network) is a predictor of some life outcomes.
  • Parent’s natural response when faced with a teenager who reports that he or she hasn’t nearly as many “friends” or “buddies” as others in his/her class.
Does the following sound familiar?

Why is it that we want 220 friends when we only ever speak to about 10 of them? And the worst thing is, there is always a mini competition to see who has the most friends driven to such an extent that people make fake accounts and/or befriend strangers who are new to these social networking sites.

It started to bother me says one mum, my daughter wasn’t very popular, and I suggested that she could fatten up her buddy list with names that I know my daughter is friends with….

Click here for full paper

Sunday, September 5, 2010

The Strange Effect of the Bathroom Scales

Jack Dikian

A few weeks ago I found myself weighing almost 10Kgs more than what I thought I'd weigh. This was after jumping on a new set of bathroom scales and having to almost do a double-take of the rotating dial. Whilst it’s true that some of my otherwise slim-fitting shirts aren’t fitting so well – I still regarded the 10Kg increases as excessive.

A number of theories prevailed – after all, the scales cost less than ten bucks. Engineering? that's something you wouldn't want to bank the farm on. Having said that though, the complication of most scales is by no means a Swiss chronometer. Also, it seemed to be calibrated, at least without a load.

Could using scales on soft flooring alter the scales’ functioning? More importantly, and by far the more interesting question - what exactly is it that scales measure. It turns out that this isn’t as obvious as it might seem, unless of course you are a physicist.

I’m going to return to the saga of the bathroom scales a little later – after exploring shorthand conventions and assumptions relating to the physical quantities,
mass and weight. For example, it is often said that bathroom scales is a measuring instrument for determining the weight or mass of an object. Here, both mass and weight are used synonymously.

Mass and Weight

Students of science often confuse mass and weight and many feel that there is no difference between the two. In fact the two are not the same.

Mass is the amount of matter present in a body and is an intrinsic property of the body. The mass of an object remains unaltered regardless of the reference frame it is being measured in and according to
special relativity it is related to energy by the famous relationship formula E = mc2. Weight on the other hand is the force which a given mass experiences due to the gravitational force between itself and another mass point (the Earth in our reader’s case).

Simply, we use the word mass to describe how much matter an object posses. On Earth, we weigh objects in order to calculate their mass. The more matter there is, the more the object will weigh. The difference between mass and weight is that weight is determined by the pull of the Earth’s gravity. If we are comparing two objects to each other on Earth, they are pulled by the same gravitational force and so the one with more mass weighs more. In space, where (where there is large distance between the two mass points) the gravitational force or pull of the Earth is smaller, an object may have no weight and yet still posses mass.

More formally, mass refers to any of three properties of matter, which have been shown experimentally to be equivalent. These are:

 Inertial mass,
 Active gravitational mass and
 Passive gravitational mass.

The inertial mass of an object determines its acceleration in the presence of an applied force. According to Newton's second law of motion, if a body of mass m is subjected to a force F, its acceleration a is given by F/m.

A body's mass also determines the degree to which it generates or is affected by a gravitational field. If a first body of mass m1 is placed at a distance r from a second body of mass m2, each body experiences an attractive force F whose magnitude is :

F = G(m1m2)/ r2

where G is the universal constant of gravitation, equal to 6.67×10−11 kg−1 m3 s−2. This is sometimes referred to as gravitational mass (when a distinction is necessary, M is used to denote the active gravitational mass and m the passive gravitational mass). Repeated experiments since the seventeenth century have demonstrated that inertial and gravitational mass are equivalent; this is entailed in the equivalence principle of general relativity.

The Unassuming Kilogram

Since 1889, the International System of Units (SI system) defines the magnitude of the kilogram to be equal to the mass of the International Prototype Kilogram often referred to as the “IPK”. The IPK is made of a platinum alloy and is machined into a cylinder. The IPK, also affectionately known as the ‘Big K’ and its six sister copies are stored at the International Bureau of Weights and Measures in a vault in the outskirts of Paris.

Three independently controlled keys are required to open the vault. Official copies of the IPK were made available to other nations to serve as their national standards. These are compared to the IPK roughly every 50 years.

For Australians, a metal ingot weighing precisely one kilogram is locked in a safe in a government facility on Sydney's North Shore. It is the kilogram against which all other kilograms in Australia are measured. Every precaution is made to ensure the weights are not contaminated. Given this is the reference standard of mass, any contamination with dust or fingerprints or any sort of foreign material, if unchecked, will impact upon and propagate throughout every aspect of everyday life as we know it.

What of the bathroom scales

David MacKay, a physicist at the University of Cambridge, after a chance conversation about bathroom scales measuring a greater weight when on carpet decided to investigate the reasons.

MacKay and his students tried a number of analogue bathroom scales on different surfaces. Sure enough, they found they weighed in at around 10 per cent more on thick carpet than on the hard floor.

To find out why, the studens took several sets of scales apart and measured the movement of the internal mechanisms when loaded on different surfaces. Inside each set of scales, four levers or "fulcrums", each pointing inwards from one of the corners, transmit the weight of the person to a spring-loaded metal plate at the back of the scales. The movement of the plate is then transferred via a metal rod to turn the dial on the scales.

They found that on a hard surface, the base of the scales bows. This makes the fulcrums at each corner of the scales tilt in slightly, shortening the distance between each fulcrum and the point at which the load pushes onto the lever.

Put the scales on a deep carpet, however, and the scales sink into it, so the carpet supports the base, which prevents it from bending. This increases the distance between each fulcrum and the point at which its lever is loaded, so for the same force the lever moves further. Even a small increase in this distance can add several kilograms to the weight registered on the display.

"I've always thought this was an urban myth," says a spokeswoman for Weight Watchers. "But it sounds like it makes a huge difference."