Stephen Hawking's Four Essential Questions

March 14 marks six years since death to Stephen Hawking. On his personal website (now replacing), Hawking defined himself as “Cosmologist, space traveler and hero“It was definitely, The three things. Claimed to work in The basic laws that govern the universeHe described his three main discoveries.

We will summarize it here. We will discuss four transcendent questions answered by Hawking: Where are time and space born? Where do they die? Is the universe finite? Does humanity have a future in it?

Based on Einstein

Hawking's work builds on the extraordinary theory we have about the universe: General relativity By Albert Einstein. Revolutionary concept of time And based on space (continued Free time), based on the principle of equal power. Fruit, in turn, a Moment Eureka: The free fall that Einstein imagined From the roof of your house.

From his incisive logic, backed by incredibly clear principles, resulted in A Just The possible law of the universe, which is given by the relativistic field equations. So, for our universe, according to Cosmic principleThey admit A Single Solution: That Friedman-Lemaitre-Robertson-Walker.

Exceptional result: a Just A possible equation and solution to the universe!

Hawking started there and was surprisingly able to go further Singularity theories (Hawking-Penrose) and the results on Temporal and spatial thermodynamics (Beckenstein-Hawking). With them he was able to answer eternal questions.

Where is time and space born?

Using Einstein's theory, Hawking concluded that our universe has Origin In the past beginning. This was his first discovery. Hawking and Penrose's singularity theories state that space-time began with a singularity: a singularity the great explosion.

This has been proven by going back in time, using theoretical equations and conditions that existed in the early universe (partially recreated in large laboratories, e.g. CERN).

There comes a moment when time and space disappear: it is no longer possible to go back any further. There is its origin! It is like searching for the sources of the Nile, as Livingstone did, the exact place where he was born.

Where do they end?

Space-time comes to an end in each of the black holes that are constantly forming in the universe. These are other singularities that arise from Hawking-Penrose theories. Laundries where time and space disappear forever.

These results led to the need to Gravity quantization, to be able to validate it on very small scales. Only then can they be considered definitive, and not just classical estimates of reality. In other wordsIt was necessary to combine Einstein's general relativity and quantum physics: the two great theories of the twentieth century.

The first step in this direction was taken by Hawking himself, with his second great discovery: Hawking radiation.

“Each Schwarzschild black hole, of mass M, emits electromagnetic radiation as if it were an ideal black body at the temperature: T = ℏc³/8πGMk“.

The magic formula, which combines the most fundamental constants in nature: Planck, ℏ (quantum physics); The speed of light, C (relativistic physics); That universal gravity, g (Newtonian physics); Boltzmann, K (Thermodynamics); And the number π (mathematics).

everyone The major physical theories are brought together in a simple formula. A beautiful international symphony!

However, Hawking opened new paths that had not yet been explored. One, towards Gravity quantization. And another, towards the emerging theory of quantum information and its amazing cosmic paradoxes.

Is our universe finite?

This question has interested many generations. For centuries, the universe was thought to be eternal, infinite in space and time. Then he changed his mind several times.

Hawking and Hartle even showed that if time were imaginary to begin with, the universe would lack edges and boundaries. It would be finite, though infinite, and there would be no initial singularity. The way I was raised Hence it will be determined by the laws of physics.

This was his third discovery, Hartle Hawking's conjecture About the universe Self-sufficientSomehow.

Does humanity have a future in the universe?

Already in the last years of his life, Hawking analyzed the very serious problems we face. He concluded that it could become fatal to humanity if we do not solve it in the next hundred years.

Hawking was optimistic: he predicted that by then, we would have established self-sustaining colonies off Earth. Advances in intelligence (human and artificial) will have found the solution to the many problems that now lie. Opening a new horizon for centuries of hope.

His final piece of advice to young scientists (always his favorite audience) was to keep that wonderful feeling always alive when thinking about our vast and complex world: “There is nothing that can compare to the experience of an instant EurekaTo discover for the first time what no one knew“.

Until the universe fades away, or humans disappear, the extraordinary discoveries that Stephen Hawking left us – such as his beautiful formula, now engraved on his tombstone – will generate new knowledge. In this unique time and place in which we remember him today, six years after his death.

Emilio ElizaldeSenior Research Professor, Theoretical Physics and Cosmology, Space Science Institute (ICE – CSIC)

This article was originally published on Conversation. Read the creative.