In physics you have four fundamental forces and four fundamental dimensions and two fundamental types of stuff with associated properties and fates. In each case you have something, the odd one out – the one that is not symmetrical – the jokers in the physics deck. What are they?
1) You have four fundamental forces of which three have symmetry.
*Electromagnetism or the Electromagnetic JOKER123 Force where symmetry abounds – magnetism can generate electricity; electricity can generate magnetism. Electricity/magnetism symmetry includes the positive vs. the negative; the northern pole vs. the southern pole of a magnet; attraction vs. repulsion; the negative electron vs. the antimatter twin, the positron.
*Strong Nuclear Force has symmetry in that within the nucleus of an atom, positively charged protons repel each other – protons push outwards, yet gluons keep them in their assigned place within the nucleus – gluons pull inwards: attraction vs. repulsion.
*Weak Nuclear Force has symmetry in that particle interactions can go in either direction. Weak interactions govern radioactivity. Radioactive nuclei can obviously be created; they also obviously can come apart at the seams (radioactive decay)!
*Gravity (the Joker): Gravity is unidirectional – it is attractive only. There is no equal and opposite antigravity except in the minds of science fiction writers.
2) There are four fundamental dimensions (ignoring unverified string theory) of which three have symmetry.
You need all four dimensions (space-time) in order to specify any particular event. You cannot have a happening in space without also having it happen in time; you cannot have an event that happens in time without it also happening in a three dimensional space. Yet only three of these dimensions are symmetrical.
*Left & Right is obviously symmetrical. These movements can be undone or reversed.
*Back & Forth is also obviously symmetrical. These movements can be undone or reversed.
*Up and Down are two directions that are obviously symmetrical. These movements can be undone or reversed.
*Time (the Joker): Time is unidirectional. Time flows in one direction only, from past to present to future. There is no equal and opposite arrow of time that extends from the future to the present and onto the past. Time cannot be undone or reversed. You cannot go back in time and change what has already happened. You remember the past; you do not remember the future.
3) There are two kinds of stuff plus the properties of stuff (like velocity, temperature, pressure and density) and the ultimate fate of stuff.
*Mass: There’s a conservation law – the conservation of mass/matter – which states that matter can neither be created not destroyed, only changed in form. Matter (mass) can be converted to other forms of matter. You can go from a solid to a liquid to a gas and back again. You can go from hydrogen and oxygen to water and from water to hydrogen and oxygen. You can fuse hydrogen into helium (which powers the Sun) which is also an example of the equivalence between matter and energy (see below) since that fusion process releases a lot of energy at the expense of a tiny bit of mass. Matter (mass) also has another form of symmetry – antimatter. Antimatter is the same as matter only with opposite electric charge (like the negatively charged electron and its antimatter counterpart, the positively charged positron).
*Energy: There’s another conservation law – the conservation of energy – which states that energy can neither be created nor destroyed, only changed in form. Energy can be converted to other forms of energy. The chemical energy inherent in petrol gets converted to the kinetic energy of motion and heat energy. The electromagnetic heat and light energy from the Sun powers up green plants, which in turn convert that solar radiation to chemical energy and ultimately your petrol as a fossil fuel, or fuel you directly as you munch on your salad.. Unlike matter however, there is no anti-energy since energy doesn’t have any charge. But I hear an objection here. What about electrical energy? Surely electricity is the flow of electrons and electrons have negative charge.
There’s another conservation law – the conservation of charge. An electron just cannot shed its negative charge and remain an electron. The electron in fact doesn’t shed its charge after electrical energy has been converted to other forms of energy. Just think of your everyday household electrical appliances. Electrical energy gets converted to sound, heat and motion in your electric razor; ditto your electric tea kettle. Your TV set receives electrical energy which is converted to light, sound, and heat. Your electric radiator converts electrical energy to heat and light; your flashlight battery converts chemical energy to electrical energy hence to light (and some heat). But sound, heat, light, motion etc. doesn’t not contain any charge. The electron’s negative charge does not literally get converted to heat or light or motion or sound. So it’s not the electron’s charge itself that’s the source of the energy in electrical energy.