The World According to Physics

by Jim Al-Khalili

The universality of the laws of nature has fascinating mathematical origins and is linked with one of the most powerful ideas in science: symmetry. At a rudimentary level, everyone understands what is meant by a geometric shape that is symmetrical.

Noether’s theorem tells us that we don’t ‘invent’ the mathematics in order to have a way of describing the world, but rather, as Galileo observed, that nature speaks the language of mathematics, which is ‘there’, ready and waiting to be discovered.

Without matter (air) there would be no sound. In space, no one can hear you scream, as the byline to the 1980s movie Alien correctly pointed out.

This notion leads to the most famous equation in physics: E = mc2, which links mass (m) and energy (E) together (along with the square of the speed of light, c) and suggests that the two quantities are transformable into each other.

Nature does not care about our petty squabbles regarding the correct interpretation of quantum mechanics—it gets on with doing things the way it does, and exists independently of our perceptions.

Almost all phenomena we see in nature are due ultimately to one or other of these two forces: gravity and electromagnetism.

Superstring theory thus states that there are ten dimensions: four of spacetime that we experience plus the six hidden dimensions.

Originally, dark matter was proposed to explain the large-scale dynamics of entire clusters of galaxies. Further evidence then came from the way stars moved within spiral galaxies, circulating like undissolved coffee granules on the surface of a mug of instant coffee after it has been stirred.

Today, physics has given us a demystified explanation of how the universe began, with overwhelming observational evidence to back it up. But did the Big Bang itself have a cause? Was there something that triggered the birth of our universe in the first place?

The simplest answer is that there was no ‘before’ the Big Bang, for it marked the birth of both space and time. An idea put forward by Stephen Hawking and James Hartle, called the ‘no boundary’ proposal, states that, as we wind back the clock closer and closer to the Big Bang, time begins to lose its meaning and becomes more like a dimension of space.

Without an understanding of semiconductors, we would not have developed the transistor and, later, the microchip and the computer.

That handheld supercomputer we all carry around with us today (our smartphone), without which many of us would now feel utterly lost, is packed full of electronic magic, none of which would have been possible without quantum mechanics.

Our most successful scientific theories, such as relativity, quantum mechanics, the Big Bang theory, Darwinian evolution, plate tectonics, or the germ theory of disease, have all undergone rigorous scrutiny and have all emerged as the best explanations we have. None of these can be dismissed, as one often hears (particularly regarding Darwinian evolution), as ‘just a theory’.

Just as the word ‘theory’ has a different meaning in science compared with everyday conversation, so too does the word ‘certain’ mean something particular to scientists. Deep down, of course, I am actually quite certain that it is impossible to overcome the force of gravity through meditation in order to float off the ground.

But, if we want to know where we come from, where the atoms in our bodies were formed—the ‘why’ and ‘how’ of the world and universe we inhabit—then physics is the path to a true understanding of reality. And with this understanding, we can shape our world and our destiny.