Mysteries of Fundamental Physics

While the science of physics is able to explain an enormous amount of things about the world, there are still enough mysteries to keep physicists busy for a long, long time. I will talk about mysteries relating to fundamental physics. Fundamental physics explains the rest of physics and provides the basis of chemistry.

Fundamental physics is just one small part of science, but discovering solutions to its mysteries can reveal new kinds of scientific knowledge.

Creationists say that the existence of scientific mysteries demonstrates that all science is unsound. This is their argument against the theory of evolution.

Some aspects of science may be hard to understand or believe. But, at a time when there are so many global problems that cannot be addressed without scientific guidance, the many groundless alternative beliefs and fake news are a threat to humanity.
It would help humanity if more people had some idea about scientific mysteries and the large body of science that surrounds them.

Mysteries
When there are phenomena that can’t be scientifically explained, scientists look for aspects of known science that might give them some clues. They also try to imagine what new theory or concept might be invented to solve the problems. Usually, they will produce new theories, of which there may be several versions. Other scientists may be dubious or dismissive. Scientific journals and other publications will discuss all this, sometimes with undue optimism. I will include a few examples in the discussion, and some of the people here might disagree with what I say.

The apparent weirdness of some fundamental physics might make you think that I am talking gobbledygook. Don’t be put off by that, or by the scientific terms. I will explain things whenever necessary.

I will now discuss a few mysteries, using seven topics:
Some basic scientific concepts.
Dark matter;
Quantum mechanics;
The special and general theories of relativity,
Black holes,
The second law of thermodynamics, and
Expansion of the universe.

Some basic concepts

Physics recognises a range of basic entities such as matter, energy, time, and space.

These entities interact with each other in accordance with their particular characteristics. Their interactions produce forces that pull things together and push things apart. These forces produce everything that happens in the universe. For example, every piece of matter is made of particles and groups of particles that have been brought together and held together by forces.

There are four known fundamental forces, the gravitational, the weak nuclear, the electromagnetic and the strong nuclear forces.
The gravitational force makes objects attract each other, a bit like the way magnets attract iron. This force holds us to the earth. If the gravitational force suddenly disappeared, we would all start floating into space, along with everything else that wasn’t tied down.
The amount of gravitational force between objects is proportional to their masses, that is, to the amounts of matter of the particular objects. Also, the force gets smaller in proportion to the square of the distance between the objects. If we were standing on a small object in outer space, such as a comet or an asteroid, and then threw a ball up, it might not fall back. The ball would go further up than it would on Earth, and the gravitational force of the object we were on might be too weak to pull it back. It might not even be a good idea to jump.

The strong nuclear force holds protons and neutrons together to form the nucleus of each atom. Its effect barely reaches beyond the nucleus of the atom.

The weak nuclear force affects electrons and some other particles, and also causes changes to protons and neutrons inside the atomic nucleus, sometimes leading to radioactive decay. As with the strong force, it has an extremely short range.

The electromagnetic force comes from the electric charge of particles such as protons and electrons, each one of which has one unit of electric charge. The charge of a proton is referred to as positive and the charge of an electron is referred to as negative. Positive charges repel each other, negative charges also repel each other, and positive and negative mutually attract each other. An electric current is the movement of electrically charged particles, driven by these repulsions and attractions. Electric current produces heat and/or magnetic energy and/or electromagnetic waves.

The differences between the maximum strengths of these forces are astounding. The weak nuclear force is about a million trillion trillion times the gravitational force. The electromagnetic force is about ten million million times the strength of the weak nuclear force. And the strong nuclear force is about a thousand times the strength of the electromagnetic force.

Physicists say that if the values of the fundamental masses and forces, were different from their present values, the universe, as we know it, could not contain galaxies, stars and planets.

How could the universe have formed such surprisingly appropriate and specific values?

Some people concoct rationales to explain it, some invoke the supernatural, and some regard this to be a mystery. One rationale is that our universe is one of a huge number of universes, all of them different, and we just happen to be lucky. Another is that it is the result of a long process of evolution. How would we know?

That is my first mystery.

Dark matter

I will now look at dark matter, which nobody can see.

A galaxy is a system of millions or billions of star systems that are more or less like our solar system. Each galaxy throughout the universe is held together by the pull of its gravitational forces. Also, the galaxies are rotating. Some galaxies are rotating fast enough for us to expect their outer parts to be flung out into space. The calculations say that there is insufficient mass in the galaxies for their gravitational force to hold the outer parts in. But they don’t fly out. Cosmologists think there must be some extra source of gravity to hold them in. They can’t see it, so they call it dark matter.

The calculated total mass of dark matter in the universe is about five times the calculated mass plus energy of the universe itself. And that is just about all that is known about dark matter.

There have been suggestions about what it is, but none have been confirmed. One hypothetical contender is WIMPs, i.e., weakly interacting massive particles. Despite all sorts of attempts, no WIMPS have been detected. Another candidate is neutrinos, which we know about and have detected. Neutrinos are extremely tiny particles, much smaller than electrons, travelling at a very high speed.
They pervade the universe. Trillions of them are passing through our bodies all the time. They have not been ruled out, but it would be odd if, while being a part of the universe, they also had five times the mass of the universe.

Some scientists think there is no dark matter, just something missing from our laws of gravitation. But the calculations using their theories don’t fit the evidence from the astronomers’ observations.

Which makes dark matter the second mystery in this talk.

Relativity and Quantum mechanics

Relativity and quantum mechanics are fundamental theories of physics, but they disagree on some issues. Relativity is mainly relevant at extremely large masses and speeds, and quantum mechanics is mainly relevant at extremely tiny masses and distances.

There are two theories of relativity. The special theory of relativity refers to objects that are moving at very fast speeds. An observer measuring a very fast moving object would find that the space around it has shortened, and time around it has lengthened, that is, slowed down, and the mass of the object has increased.

These three changes may be hard to visualise.

Space being shortened means that distances become shorter and things become closer together. Lengthening time means that events take longer to happen.

The mass of an object can be thought of as the amount of energy required to change the object’s motion. The increase in the mass of a moving object is because, as the speed increases, more and more energy is needed to change the object’s speed or direction.
According to the formula that calculates the increase of mass, at two thirds of the speed of light, or 720 million kilometres per hour, the mass of an object is increased by about 35%. At 99% of the speed of light, the object’s mass would be 50 times its normal mass. At the speed of light, the object’s mass would become infinite. To produce an infinite amount of mass would require an infinite amount of energy, which is impossible. So moving as fast as the speed of light is impossible.

Similar formulas relate to the changes of space and time, which are referred to as “distortions”.

All this might be hard to believe, but it has to be taken into account for space missions where rockets travel at very high speeds, and for the accuracy of the GPS service, which uses satellites orbiting around the earth.

This theory also says that matter can be converted into energy, and energy into mass, as described by Einstein’s famous formula e = mc2.

It also views the concept of space and time as one integrated entity, spacetime.

The general theory of relativity also relates to mass and spacetime. It says that, in the area surrounding an object, the effect of the mass of the object is to stretch space and to make time slow down. The amount of these effects is proportional to the mass of the object, and it decreases in proportion to the square of the distance from the centre of the object. So, to get a lot of distortion of spacetime, it is necessary to be fairly close to a fairly massive object. And with both space and time lengthened, the closer to the massive object, the slower everything happens.

This means that when something enters an area where spacetime is distorted by a massive object, it will have its direction of travel bent towards the massive object. This is because the side of the moving object that is closer to the massive object will be moving more slowly, which changes the object’s orientation than the side that is further away. This is equivalent to the force of gravitation, which I have already described. It is what makes satellites go into orbit around the earth.

If the object is travelling very fast, its path may not bend enough to make it go into orbit and it could then “escape”. If it is moving more slowly, its course might be bent enough for it to crash into the massive object.

All of the predictions arising from the theories of relativity have been confirmed by rigorous testing, with the exception of some aspects of black holes. This is one area where relativity disagrees with quantum mechanics.

I will discuss black holes later, and will now discuss quantum mechanics.

Quantum mechanics has a lot of strange aspects, but they are all supported by observation and mathematics. It says that everything in the universe comes in packets of specific size. That is, size is not continuous. It increases or decreases by tiny “quantum leaps’. This applies to mass, space, time, energy, force and everything else. The universe can be thought of as being “granular”. with each grain having its own specific size.

One aspect of quantum theory is Heisenberg’s uncertainty principle. It says there is a limit to how precisely things can be measured. The more precise a particular measurement is, the less precise other related measurements can be. The example that is usually quoted is measuring both the position and the momentum of a moving object. Getting a perfectly accurate measure for one of them would mean knowing nothing about the other. But we would always know something about it, which makes absolute exactness impossible.

Quantum mechanics, by both theory and observation, has produced what is called its standard model. This model includes a range of fundamental particles, and their properties. The main ones are:

Particles and other objects can be represented and treated as waves. But only very small objects can behave like waves. Similarly, waves can be represented as particles, but can behave like particles only at small, high energy, wavelengths.

Particles can be in more than one place at the same time. They can also be in more than one version of a particular condition at the same time. This is called superposition. When a particle interacts with something or is detected and measured, only one location and only one version of the condition can be “successful”, and this is the one that occurs. The mathematics calculates the probabilities of each possibility, but makes no predictions. A humorous depiction of superposition is known as Schrodinger’s cat, where a cat in a closed box is both alive and dead until its condition can be determined by observation.

Some particles, called bosons, provide the fundamental forces. For example gluons provide the strong nuclear force that holds together the nucleus of every atom. Photons contribute to the electromagnetic force. One kind of particle, the Higgs boson, that has been in the news a lot during recent years, is said to “bestow mass onto matter”.

Two particles can become "entangled" with each other by momentarily coming together. Then, when the particles go their separate ways, if one of them is observed, the characteristics of the other are also simultaneously known, irrespective of the distance of separation.

So entanglement appears to violate the special theory of relativity by allowing information to exceed the speed of light.

These things may sound weird or illogical, and inconsistent, in contrast with the accepted principle that all physical processes are logical, consistent and predictable. But they are supported by mathematics and observation. Quantum behaviour is more obvious at the atomic scale or thereabouts. At larger scales, physical processes are found to be consistent and predictable.
As with relativity, all of the predictions arising from quantum theories have been confirmed by rigorous testing, with the exception of some aspects of black holes.

Despite the overall success of quantum mechanics as a theory, there is no satisfactory way of explaining how superposition, entanglement, etc., could occur. The prominent suggested kinds of explanations are the Copenhagen and the many worlds interpretations.

The description that I have just outlined applies to the Copenhagen interpretation. Its mathematics explains superposition, but it has no explanation of entanglement.

Many scientists prefer the many worlds interpretation. This rejects superposition, which avoids the problem of entanglement. Particles are in just one position and one condition. Interactions occur almost as if they are not quantum processes.

However, this interpretation requires that all of the possible conditions that a particle could have had, must occur, but not in this universe. Other universes cater for every other possible outcome of every interaction that could have happened but did not happen, in our universe. To accommodate this, new universes keep occurring, all slightly different from the others.

These descriptions of the Copenhagen and many worlds interpretations were just rough overviews. There are many versions of both.

All version of quantum mechanics feel unconvincing. They can be mathematically described but the underlying processes can’t be explained. The many worlds interpretation seems to be an excessively grand way of accounting for individual sub-atomic probabilities, and it introduces some additional mysteries.

A humorous attitude to the Copenhagen interpretation, is "shut up and calculate". This recognises that the workings of quantum mechanics are still a fundamental scientific mystery.

There must be some underlying process that will look logical when we discover it.

Relativity and quantum mechanics have differences of opinion regarding entanglement, which I have just discussed. They also differ regarding black holes.

So the two mysteries here are how to resolve the incompatibilities between relativity and quantum mechanics, and how quantum mechanics works.

Black holes

Black holes are extremely dense objects that strongly attract everything in their vicinity. The mass of black holes ranges from about ten to billions of times the mass of the solar system. The gravitational effect of this huge mass makes the space and time around black holes so warped that nothing can escape from them, not even light. This accords with the general theory of relativity. This theory also predicts that black holes exist forever and their enormous force of gravity makes them contract to an infinitesimal size. Quantum mechanics disagrees with both predictions.

Astronomers have detected matter falling towards black holes. Because light can’t escape from the area around them it is impossible to see black holes themselves or anything in the space surrounding them.

What can be seen is the area where light and matter begin to be able to avoid being swallowed by the black hole. This area, known as the event horizon, contains matter that is captured in orbit around the black hole. This matter includes ionised gas, which emits a huge amount of light. Some of this gas escapes at high speed. In the meantime, more matter, including gas, is being attracted to the black hole. Earlier this year, there were coloured pictures of the event horizon of a black hole on television and newspapers.
The black area inside the brightly coloured event horizon of typical black holes is many times bigger than our entire solar system.

A theory called string theory was developed about 50 years ago as an attempt to solve the incompatibilities between relativity and quantum mechanics. Its many versions have described a huge number of hypothetical unique universes, but haven’t solved the problems of this mystery.

Astrophysicists say they are only beginning to understand the quantum physics of black holes, which means they think that, sometime, they will. Perhaps they will then resolve the difference of opinion with relativity.

The ultimate future

Some fundamental science gives glimpses of the ultimate future of the universe. This is, of course, not an issue that anyone needs to worry about, but some people, including me, think it’s an interesting philosophical mystery.

I will discuss two scenarios, the second law of thermodynamics and the expansion of the universe.

An example of the second law of thermodynamics is that if something hot, i.e., with a high temperature, is in close contact with something cooler, i.e., with a lower temperature, then heat will transfer automatically from the hot thing to the cooler thing, making them closer in temperature. Heat will not be transferred from a cooler thing to a hotter one unless some outside energy is provided to increase the difference in temperature.

Temperature may be thought of as the pressure of heat, or, in scientific terms, the heat potential. Heat is one form of energy. Each form of energy has its own kind of potential.

Voltage is electrical potential. The force of gravity also is a potential. A gravitational example of the second law is expressed as "water finds its own level." Water readily runs downhill, but does not freely run uphill.

Overall, the differences between temperatures, and all other kinds of potential, are continually becoming smaller throughout the universe.

The second law of thermodynamics also implies that patterns and structures will not, of their own accord, become more complex or more structured. Some complex systems do occur from the energy of nearby reactions. All forms of life are examples. But the overall tendency will always be towards less complexity and more “disorder”. The entire universe is becoming more uniform and more disorderly.

This law reinforces the idea that time has only one direction. If an egg is cracked and the yolk and white are whipped together and then cooked, there is no possibility that time will run backwards and reassemble the egg.

The process of continuously increasing uniformity implies that the universe will eventually become stagnant and hardly anything will happen.

Some people speculate that when the universe meets a certain stage of uniformity, it will start becoming more and more complex and differentiated. Whether time could then run backwards and cause omelettes to turn into fresh eggs is a moot point. Such a reversal require the input of a huge amount of energy, and might involve some unknown processes, implying new concepts of causality and time.

The second scenario relating to the ultimate future is based on observations made by cosmologists that the universe is expanding at an increasing rate. If the universe keeps expanding, everything will keep getting further away from everything else. In some distant future, everything will be too far from everything else for any interactions to occur.

There must be a source of energy driving this expansion. It would be great if we could we find a way to tap some of it off. That might solve a few energy problems to save our planet.

If the universe is expanding at an increasing rate, then the amount of this energy must be increasing. We can’t detect it, so we call it dark energy.

Some people speculate that this energy will run out at some stage, and the universe will start shrinking through gravitational attraction. This could eventually create another “big bang”. But irrespective of whether the universe kept expanding, or maintained its size, or started to contract under the gravitational force, it would continue to become more uniform and inert.

Whatever dark energy is, it is calculated to be about twice the mass of the rest of the universe plus dark matter. There is no accepted theory to explain dark energy, but there are a few theories.

Some scientists speculate that it is the same energy that created the big bang at the beginning of the universe. The idea is that some energy was left over at the big bang, and dark energy is this leftover energy.

But saying that some external energy created the big bang goes against the common assumption that the big bang was the beginning of everything, including space and time and mass and energy. So, did the big bang just occur mysteriously out of nothing, or did something cause it?

Or did the big bang actually occur? There are theoretical problems with it.

Some scientists think that the big bang, or some other incident, must have occurred in a much larger entity than our universe. They argue that, just as our universe creates stars and planets and organisms, a larger universe could have created smaller universes, including ours.

But what produced that larger universe and all that energy? Continuing this theme of beginnings leads to some infinite past. But if time were infinite, we should have already reached the condition of universal stagnation, as described by the second law of thermodynamics. Does this disprove the second law? What do we mean by an infinite past?

We have infinite numbers in mathematics, but we would need new kinds of concepts to describe infinite time, and also infinite space and material.

The alternative to an infinite past is an ultimate beginning at which everything began.

This must mean it began from nothing.

How could something happen if there was absolutely nothing; no time no space no material and no potential to do or be anything?
This is a very deep mystery.

Solvable, and probably unsolvable, mysteries

I have now discussed seven fundamental mysteries: the good luck of the universal constants, dark matter, relativity, quantum mechanics, the ultimate future, dark energy, and how the universe could have begun.

Some scientists expect all mysteries to be solvable. I think that is a matter of faith –some mysteries might be intrinsically unsolvable, at least by humans. But which ones fit into which category? The criteria might be whether the mystery is the result of human limitations, or physical impossibility, or philosophical untenability.

Human limitations relate to physiology and brainpower, which determine what interactions we are able to make with the physical world.

What we discover about the world relies on our kinds of sensory organs and our ability to interpret what they tell us, and on our imagination and reasoning. Our imagination and reasoning have enabled us to develop theories, and to devise and build very powerful instruments that greatly extend the kind of interactions we can make. But there may be many things that we intrinsically can’t know about.

The main physical impediment to knowledge is the sheer size of the universe. Cosmologists deduce that most of the universe is so distant from us that the light from it has not yet reached the earth.

Light from the more distant parts of the visible universe is very faint and subject to distortion and pollution. Much of the detail is indistinct. The continually increasing expansion of the universe is making it increasingly distant from us. And some of what we can see happened billions of years ago. We assume, but don’t know, that the rest of the universe is similar to what we can see.

The philosophical mysteries take us to concepts that seem to be beyond logic. They would seem “unnatural”, with unnatural being distinct from supernatural.

There have been scientific concepts that once seemed unnatural and are now taken for granted. Examples are the relationship of the earth to the rest of the universe, gravitation, electricity, radio waves, and the distortions of mass, space and time. Mathematical examples are irrational numbers, negative numbers, imaginary numbers and fractals.

We now have quantum mechanics, infinite time and space, and ultimate beginnings, which all seem unnatural and contain mysteries.
Solving such mysteries could transform our lives in the same way that solving our previous mysteries has done.

Conclusion

What I have presented is a superficial picture of some mysterious aspects of one branch of science.

I think there will always be mysteries, and things that we are intrinsically unable to know about.

But that doesn’t negate the things we have already discovered and explained, even if some of our explanations may be incomplete.

Presentation to the Agnostic Forum, Melbourne, September 1st, 2019

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