The Search for the Fundamental

Motion of gas molecules Español: Animación mos...
Motion of gas molecules Español: Animación mostrando la agitación térmica de un gas. Cinco partículas han sido coloreadas de rojo para facilitar el seguimiento de sus movimientos. Русский: Хаотическое тепловое движение на плоскости частиц газа таких как атомы и молекулы (Photo credit: Wikipedia)

When does it stop? This screen that I am looking at, the keyboard that I am typing on, the invisible air between my eyes and the screen, even my body, all are composed of atoms, I told and believe. Apart from atoms, all there is is radiation, of various sorts.

The ancient Greek philosophers didn’t know about atoms so proposed various theories, which today seem quaint, but eventually they came around to atomism, and abandoned the other theories. In particular the theory of the four classical elements, earth, fire, water and air was dropped.

The four classical elements, after Aristotle. ...
The four classical elements, after Aristotle. Чотири стихії (за Арістотелем) (Photo credit: Wikipedia)

As I said, the theory now sounds quaint, but, given that the ancient Greek philosophers were not of an experimental frame of mind, the four classical elements could explain much of what could be observed. Everything could have been a mixture of these elements in various proportions.

After all, it appeared to work for colours – all colours that can be displayed on a computer screen can be specified in terms of the amount of the three primary colours of red, green and blue that a single pixel or dot on the screen emits. Why shouldn’t this scheme work for other things than light?

Barycentric RGB
Barycentric RGB (Photo credit: Wikipedia)

However Greek philosophers (and of course, philosophers in other cultures) noticed that, while some things could be broken down into component parts – sugar could be melted and burned, water could be driven off to leave the salts behind, and more importantly alcohol could be evaporated off and collected to make spirits, some things could not be broken down.

Gold, sulphur and phosphorus stubbornly refused to separate into earth, air, water or fire. Of course such stubbornness could be explained by the classical element theory – after all some things are easier to break down than others, but the Greeks eventually dropped the theory in favour of atomism. (This and what follows is highly simplified and condensed).

(Click here for rotating model)
(Click here for rotating model) (Photo credit: Wikipedia)

This is the belief that everything is made up of small indivisible particles which differ from element to element. The lump of gold contains billions of gold atoms, while the sulphur block contains sulphur atoms.

From about the start of the scientific revolution, people started to work out the rules of chemistry, and the ‘why’ of chemical reactions. Why did carbon in coal burn away and leave an ash? We know that the carbon in the coal burns using the oxygen in the air and creates oxides of carbon which are gasses and not easily detectable, but the experiments which led to this knowledge were preformed in the era of the scientific revolution.

So, matter is composed of atoms. That seemed to be the end of the story, as the vast majority of chemical experiments could be explained in terms of atoms, but exactly why atom A reacts in fixed proportions with atom B, but won’t have a bar of atom C. These relationships were noted but not really explained.

By the middle of the 19th century scientists began to detect problems with the “atoms as billiard balls” model. Electrons were discovered and soon related to chemistry, answering the above question. The new model, “atoms as small planetary-like systems”, had a small positively charged, and solid nucleus surrounded by a swarm of negatively charged electrons, with the electrons taking a major role in determining the chemistry of the atom.

It was discovered that many elements behaved as if each atoms of the element weighed the same, but some elements broke this rule. The gas Chlorine for example has an atomic weight of 35.45. In other words each atom weighed about 35 and half times as much as a Hydrogen atom.

It was eventually discovered that not all Chlorine atoms weighed the same. Most had an atomic weight of 35 but some (about half) had a weight of 36. To cut a long story short it was discovered that the supposedly solid nucleus was composed of a collection of other particles called protons and neutrons.

English: Liquid Chlorine in flask for analysis.
English: Liquid Chlorine in flask for analysis. (Photo credit: Wikipedia)

While the number of protons and electrons determine the chemistry of an atom almost completely, the number of neutrons contribute mass to the atom and barely affect the chemistry.

While electrons appear to be truly fundamental particles and cannot be broken down further, the protons and neutrons are composed of particles called quarks. For reasons mentioned in the Wikipedia article quarks cannot be found in isolation, but are only found in other particles.

English: The quark structure of the proton. Th...
English: The quark structure of the proton. There are two up quarks in it and one down quark. The strong force is mediated by gluons (wavey). The strong force has three types of charges, the so-called red, green and the blue. Note that the choice of green for the down quark is arbitrary; the “color charge” is thought of as circulating among the three quarks. (Photo credit: Wikipedia)

In addition to protons and neutrons, quarks make up other sub-atomic particles such as mesons. Scientists have discovered or postulated bosons which are particles that bind quarks and other fundamental particles together. From then on, things get complicated!

I haven’t mentioned the photon, which is bosonic, or the neutrino which is a fermion. All fundamental particles fit into one of these two families, and all sub-atomic interactions are the result of the rather incestuous exchange of these particles in their various groups and a strict set of rules. So far so good.

English: Enrico Fermi
English: Enrico Fermi (Photo credit: Wikipedia)

However, there are still questions to be answered. Are these particles truly fundamental or do they have components, which may or may not be particles in the classical sense? What are the sizes of these particles, if such a concept is appropriate at this level? Have we found them all? What about dark matter?

Scientists have abandoned the first question. They don’t generally refer to particles as fundamental. They have seen a long list of fundamental particles turn out to be not so fundamental after all.

Sizes of the particles may not make sense at the particle level, but the various theories may indicate sizes for some of them. There are difficulties over the size of the electron for instance. If it were a point object rather than having something that equates to size, then that causes difficulties with some theories.

As for the third and fourth questions, it appears that scientists may have found all the particles that explain ordinary matter, but naturally cautious, they don’t rule out other forms of matter such as the so called “dark matter” and “dark energy“. Dark matter and dark energy apparently interact with gravity and (from the Wikipedia article) and the Weak Nuclear Interaction.

pie chart of dark matter and normal energy rat...
pie chart of dark matter and normal energy ratio taken from en.wikipedia (Photo credit: Wikipedia)

My original question was “When does it stop?” By this I meant, which particles are truly fundamental and which have components that determine their properties? This question remains open, but if you have followed through my exposition, you will probably see that this is a question without an easy answer.

 

Thinking Inside of the Box

Illustration of the expansion of the Universe ...
Illustration of the expansion of the Universe after the Big bang. In Bulgarian. (Photo credit: Wikipedia)

Science aims to explain things, and by extension to explain everything. Is this even possible? Suppose the Universe consisted of a box, 20 million metres in each direction. Scientists inside this box could investigate this universe, but could they explain everything about this universal Box?

Suppose that the Box had impenetrable walls, so scientists could not probe outside of it. So they could say that the width, height, depth of the universe was 20 million metres and they could describe what was in it. They could also say that one side of the cube attracted everything in the Box and that side could be labelled “down” and the opposite side “up”.

English: Snapshot from a simulation of large s...
English: Snapshot from a simulation of large scale structure formation in a ΛCDM universe. The size of the box is (50 h -1 Mpc) 3 . Run using GADGET (GPL software) (Photo credit: Wikipedia)

There also might be statistical laws, so that the temperature, on average, might be 20 degrees Celsius, but could differ from that norm from place to place and from time to time. Box scientists might determine that everything appeared to be made up of tiny indivisible particles. Box atoms.

Some Box philosophers might ponder what was beyond the limits of the Box. They’d ponder the fact that starting from one side of the Box, one could travel 20 million metres in a perpendicular direction, but one could not travel 20 million and one metres. Why not?


Embed from Getty Images

I’m sure that they would have plenty of theories. For instance, one philosopher might contend that the Box was embedded in an infinite impenetrable bedrock, while another might say that it was obvious – the Box was embedded in nothing. No space, no time, no thing!

Meanwhile scientists probing the Box atoms might split them and discover a whole new world of sub-atomic particles. Others might conceive of space in the Box as being a seething mass of pairs of virtual particles, being created and moving apart for a brief instant and then merging into nothing, no thing, again.

English: Tracks of ionizing radiation in a clo...
English: Tracks of ionizing radiation in a cloud chamber (thick, short: alpha particles; long, thin: beta particles). Français : Traces d’ionisation matérialisées sous forme de micro-trainées de condensation par des particules radioactives dans une chambre à brouillard ; Les trainées épaisses et courtes signalent des particules alpha ; les longues et files matérialisent le passage de particules beta). (Photo credit: Wikipedia)

But, says one bright spark, what about a particle pair created on the boundary of the Box? One particle would enter the Box, and the other would travel somewhere else! This would lead to other speculation – if the second particle travelled in another Box, then that other Box would presumably be a mirror image of our Box!

Such speculation would wait on experimentation by the Box scientists and I’m aware that I cannot push the Box analogy too far with out it breaking. But, just as in the case of the Box scientists, philosophers and scientists in this Universe have similar issue.

An illustration of a ramified analogy, one com...
An illustration of a ramified analogy, one component of Gordon Pask’s Conversation Theory. Self-made (Photo credit: Wikipedia)

In our Universe there are no bounds (under current theories, I believe) but that doesn’t mean that we can’t speculate about what is beyond our Universe, whatever “beyond” may mean in this context.

The Box scientists could potentially explain every thing in the Box, maybe even the fact that it had existed, pretty much unchanged (on average) for all time, and that is periodically, over astronomically long time scale is doomed to repeat itself, time and time again.

Mesquita, repeat ad infinitum
Mesquita, repeat ad infinitum (Photo credit: Wikipedia)

When they go further than that, it is pure speculation, as all the data that they have relates to the Box. They have no data from outside of the Box. All the waves and particles that are observed originate in the Box. All the forces and fields are part of the Box. While scientists may speculate about “other Boxes”, that is all that they can do.

That’s the problem. The Box scientists, and the scientists from our Universe, can only observe events in the Universe in which they are embedded. Observations relate only to events in the local Universe.

English: Multiverse, a light sculpture by Leo ...
English: Multiverse, a light sculpture by Leo Villareal featuring 41,000 computer-programmed LED nodes, located between the National Gallery of Art’s East and West Buildings, on the National Mall in Washington, D.C. (Photo credit: Wikipedia)

Some conjectures suggest that our Universe is one of many universes all linked together in some way. Some conjectures suggest that the laws of our Universe apply in many other similar universes separate from ours. Some people conjecture that universes may exist where there are no laws or the laws that there are have no similarity in any way to the laws of our Universe.

In the Box universe these conjecture would amount to ideas that there may be other Box universes out there with similar laws to the Box universe, maybe linked in some way to the hypothetical Box universe. There may even be universes which have laws which are not at all similar to those of the Box universe. For instance a universe which springs from a single point in a vast explosion and expands at a vast rate either forever or to a certain point only to collapse once again. How bizarre!

The Big Bang era of the universe, presented as...
The Big Bang era of the universe, presented as a manifold in two dimensions (1-space and time); the shape is right (approximately), but it’s not to scale. (Photo credit: Wikipedia)

The Box scientists would not have any way to decide whether or not their were any other Boxes as their observations would only observe events in their own Box. The only way that events in one Box could possibly affect the events in another Box would be if there was a link between them in some way.

This doesn’t necessarily mean that the event would be observable as the effect of one universe on the other universe. It would just appear as an event in each universe as it transpires as a result of the laws of the universe in question.


Embed from Getty Images

The theory may posit a link between two universes but the events in one universe can only result from events within that universe. If this were not so, the event in the universe would appear to happen without any causation in the universe. In other words it would be an anomaly or a miracle.

In other words, suppose a scientist in one universe knows of a law where he can cause an effect in another universe. If he can cause this effect in his universe then in the other universe something will also appear to cause this effect. Maybe this cause will be a scientist in the other universe trying to create an effect in the first universe!


Embed from Getty Images

This possible symmetry of cause and effect across more than one universe would mean that it would be difficult if not impossible to detect the presence of another universe by its effects on our universe.

The person in the Box universe would likely be in the same position. This means that he would never know if there were anything outside of his 20 million metre cube. He could postulate an infinite series of Boxes stacked like bricks in an endless array. Or he could postulate Boxes grouped into “houses”. Or he could postulate that his was the only Box and that speculations about universes started from “Big Bang” explosions are mere fiction.

Detail of the bricks in the Great Wall at Muti...
Detail of the bricks in the Great Wall at Mutianyu. (Photo credit: Wikipedia)