Segui l&#x27;autore

Come tutti i libri dello stesso autore..."facile" da leggere e che e' divulgativo davvero.

Recensito in Italia il 8 gennaio 2023

lovely

Recensito in Italia il 29 dicembre 2019

Un gran bel tributo ad uno dei più influenti uomini della storia moderna. Ottimo il contenuto ed ottima l'impaginazione.

Una persona l'ha trovato utile

Piera

Libro

Recensito in Italia il 23 marzo 2021

Libro

2 persone l'hanno trovato utile

Appassionante, divulgativo, essenziale

Andrea Paternostro

Recensito in Italia il 8 luglio 2023

Da leggere in lingua originale. Hawking spiega in modo estremamente brillante (e mai noiosa) l'evoluzione delle teorie cosmologiche. Tanti esempi, altrettanta ironia, nulla dato per scontato (ma una buona cultura generale è necessaria per capirlo a fondo).

Recensito in Italia il 17 marzo 2019

A book that everyone have to read. Such a great mind, such a great man, such a great scientist. Pure light.

6 persone l'hanno trovato utile

Chiara

Grandioso

Recensito in Italia il 6 maggio 2019

Grandioso nella sua semplicità. Riesce a spiegare concetti complessi in maniera accessibile. Oltre ad essere un esempio con la sua vita

5 persone l'hanno trovato utile

Paolo

Bel libro

Recensito in Italia il 12 aprile 2020

Bello da leggere

Una persona l'ha trovato utile

Traduci tutte le recensioni in Italiano

Le recensioni migliori da altri paesi

Paulo Carvalho

Um pequeno livro de um grande autor.

Recensito in Brasile il 18 novembre 2023

Em suas últimas publicações enquanto vivo, Stephen Hawking responde todas as grandes questões científicas em aberto da atualidade com sua didática singular, raramente recorrendo a argumentos técnicos, deixando a leitura ainda mais leve. Eis um livro pequeno para capturar em duas ou três tardes as grandes ideias de um dos maiores cientistas do nosso tempo que rejeitava o rótulo de gênio. Destaque para a homenagem póstuma da sua esposa no final do livro, assaz emocionante.

Ligiaele

hermoso libro

Recensito in Messico il 14 agosto 2022

Si buscas respuestas de física cuántica es el libro Ideal pero también muchas de esas respuestas aplican a la vida de un simple mortal

Steven H Propp

A POSTHUMOUS WORK, CONSOLIDATING AND SUMMARIZING HAWKING’S VIEWS

Recensito negli Stati Uniti il 3 maggio 2022

The publisher noted in this 2018 book, “Stephen Hawking was regularly asked for his thoughts of the ‘big questions’ of the day… Stephen maintained an enormous personal archive of his responses, which took the form of speeches, interviews and essays. This book draws from this personal archive and was in development at the time of his death. It has been completed in collaboration with his academic colleagues, his family and the Stephen Hawking Estate.”

In the first chapter, Hawking explained, “People have always wanted answers to the big questions…I am a scientist… I have spent my life traveling across the universe, inside my mind… I have sought to answer some of the big questions. At one point, I thought I would see the end of physics as we know it, but now I think the wonder of discovery will continue long after I am gone… most people can understand and appreciate the basic ideas if they are presented in a clear way without equations…” (Pg. 4)

He states, “If you accept, as I do, that the laws of nature are fixed, then it doesn’t take long to ask: what role is there for a God?... One could define God as the embodiment of the laws of nature. However, this is not what most people would think of as God. They mean a … being, with whom one can have a personal reliationship… I use the word ‘God’ in an impersonal sense … for the laws of nature, so knowing the mind of God is knowing the laws of nature. My prediction is that we will know the mind of God by the end of this century. The one remaining area that religion can now lay claim to is the origin of the universe, but even here science … should soon provide a definitive answer to how the universe began… I think the universe was spontaneously created out of nothing, according to the laws of science.” (Pg. 28-29)

He adds, “When the Big Bang produced a massive amount of positive energy, it simultaneously produced the same amount of negative energy. In this way, the positive and the negative add up to zero…So what does this mean in our quest to find out if there is a God? It means that if the universe adds up to nothing, then you don’t need a God to create it. The universe is the ultimate free lunch.” (Pg. 33) He continues, “The laws of nature itself tell us that not only could the universe have popped into existence without any assistance… but also that it is possible that nothing caused the Big Bang. Nothing.” (Pg. 35)

He summarizes, “When people ask me if a God created the universe, I tell them that the question itself makes no sense. Time didn’t exist before the Big Bang so there is no time for God to make the universe in… it’s my view that the simplest explanation is that there is no God. No one created the universe and no one directs our fate… there is probably no heaven and afterlife wither. I think belief in an afterlife is just wishful thinking… We have this one life in which to appreciate the grand design of the universe, and for that I am extremely grateful.” (Pg. 38)

He recounts, “the theorems Roger Penrose and I proved … indicated that the universe began in a Big Bang, a point where the whole universe and everything in it were scrunched up into a single point of infinite density, a space-time singularity. At this point Einstein’s general theory of relativity would have broken down. Thus one cannot use it to predict in what manner the universe began. One is left with the origin of the universe apparently being beyond the scope of science… That the universe began with a singularity was not an idea that I or a number of other people were happy with.” (Pg. 50-51)

He notes, “M-theory, which is our best candidate for a complete unified theory, allows a very large number of possible histories for the universe. Most of these histories are quite unsuitable for the development of intelligent life. Either they are empty… or wrong in some other way. Yet, according to Richard Feynman’s multiple-histories idea, these uninhabited histories might have quite a high probability. We really don’t care how many histories there may be that don’t create intelligent beings. We are interested only in the subject of histories in which intelligent life develops. This intelligent life need no be anything like humans. Little green men would do as well…” (Pg. 56-57)

He asserts, “We are the product of quantum fluctuations in the very early universe. God really does play dice.” (Pg. 61) He continues, “There may be other universes. M-theory predicts that a great many universes were created out of nothing, corresponding to the many different possible histories… There is still hope that we see the first evidence for M-theory at the LHC particle accelerator… at CERN in Geneva… I think the discovery of supersymmetric partners for the known particles would revolutionize our understanding of the universe… There is still some hope that the LHC will discover supersymmetry. Bus supersymmetry might still be found in the next generation of accelerators … So there may well be other universes, but unfortunately we will never be able to explore them.” (Pg. 62-63)

He acknowledges, “That carbon atoms should exist at all, with the properties that they have, requires a fine adjustment of physical constants… If these constants had significantly different values, either the nucleus of the carbon atom would not be stable or the electrons would collapse in on the nucleus. At first sight, it seems remarkable that the universe is so finely tuned. Maybe this is evidence that the universe was specially designed to produce the human race. However, one has to be careful about such arguments, because of the Anthropic Principle, the idea that our theories about the universe must be compatible with our own existence. This is based on the self-evident truth that if the universe had not been suitable for life we wouldn’t be asking why it is so finely tuned.” (Pg. 69-70)

He continues, “One can apply the Anthropic Principle in either its Strong or Weak versions. For the Strong Anthropic Principle, one supposes that there are many different universes, each with different values of the physical constants. In a small number, the values will allow the existence of objects like carbon atoms. Since we must live in one of these universes, we should not be surprised that the physical constraints are finely tuned. If they weren’t, we wouldn’t be here. The Strong form of the Anthropic Principle is thus not very satisfactory, because what operational meaning can one give to the existence of all those other universes? And if they are separate from our own universe, how can what happens in them affect our universe? Instead, I shall adopt … the Weak Anthropic Principle. That is, I shall take the values of the physical constraints as given.” (Pg. 70)

He suggests, “The early appearance of life on Earth suggests that there is a good chance of the spontaneous generation of life in suitable conditions… Short lengths of RNA could reproduce themselves like DNA, and might eventually build up to DNA. We cannot make nucleic acids in the laboratory from non-living material, let alone RNA. But given 500 million years, and oceans covering most of the Earth, there might be a reasonable probability of RNA being made by chance.” (Pg. 75)

He points out, “According to the theory of relativity, nothing can travel faster than light, so a round trip to the nearest star would take at least eight years… In science fiction, they overcome this difficulty by space warps, or travel through extra dimensions. But I don’t think these will ever be possible, no matter how intelligent life becomes.” (Pg. 82)

He asks, “What are the chances that we will encounter some alien forms of life as we explore the galaxy?... there ought to be many other stars whose planets have life on them. Some of these stellar systems could have formed five billion years before the Earth---so why is the galaxy not crawling with self-designing mechanical or biological forms? Why hasn’t the Earth been visited and even colonized?... Maybe the probability of life spontaneously appearing is so low that Earth is the only planet in the … observable universe----on which it happened. Another possibility is that… most of these forms of life did not evolve intelligence.” (Pg. 83)

He explains, “Einstein’s paper of 1905 seemed to rule out time travel into the past. It also indicated that space travel to other stars was going to be a very slow and tedious business… If the spaceship went very near the speed of light it might seem to the people on board that the trip to the galactic centre had taken only a few years. But that wouldn’t be much consolation if everyone you had known had died… thousands of years ago when you got back. That wouldn’t be much god for science-fiction novels either…” (Pg. 130)

He suggests, “Closely related to time travel is the ability to travel rapidly from one position in space to another… the only way to get from one side of the gallery to the other in a reasonable time would seem to be if we could warp space-time so much that we created a little tube or wormhole. This could connect the two sides of the galaxy and act as a short cut to get from one to the other and back while your friends were still alive. Such wormholes have been seriously suggested as being within the capabilities of a future civilization. But if you can travel from one side of the galaxy to the other in a week or two you could go back through another wormhole and arrive back before you had set out…” (Pg. 133-134)

He notes, “it might seem that as we advance in science … we might be able to … warp space and time in some … way so as to be able to travel into our past. If this were the case it would raise a whole host of questions and problems. One of these is if time travel will be possible in the future, why hasn’t someone come back from the future to tell us how to do it… Of course, some people would claim that we have already been visited from the future. They would say that UFOs come from the future and that governments are engaged in a gigantic conspiracy to cover them up and keep for themselves the scientific knowledge that these visitors bring. All I can say is that if governments were hiding something they are doing a poor job of extracting useful information from the aliens… once you admit that some [UFO reports] are mistakes or hallucinations, isn’t it more probable that they all are than that we are being visited by people from the future or from the other side of the galaxy?” (Pg. 137-138)

He continues, “A possible way to reconcile time travel… would be to say that such travel can occur only in the future. In this view own would say space-time is our past was fixed because we have observed it and seen that it is not warped enough to allow travel into the past. On the other hand the future is open… This picture… would still have plenty of paradoxes… like going back and killing your parents before you were born… There seem to be two possible resolutions. One is what I shall call the consistent-histories approach… On this view… it would imply that we were completely determined: we couldn’t change our minds. So much for free will. The other possibility is what I call the alternative-histories approach… [whereby] the universe has every single possible history, each with its own probability… But each history is complete and self-contained… So a rocket cannot transfer to another alternative history when it comes around again… It thus seems that we are stuck with the consistent-histories picture…” (Pg. 138-140)

He concludes, “According to … M-theory… space-time ought to have eleven dimensions… seven of these dimensions are curled up in a space so small that we don’t notice them… If this picture is correct it might be possible to arrange that the four flat dimensions get mixed up with the seven highly curved or warped dimensions. What this would give rise to we don’t yet know. But it opens exciting possibilities. In conclusion, rapid space travel and travel back in time can’t be rules out according to our present understanding. They would create great logical problems, so let’s hope there’s a Chronology Protection Law to prevent people going back and killing their parents. But science-fiction fans need not lose heart. There’s hope in M-theory.” (Pg. 142)

He suggests, “the rapid pace of improvement will probably continue until computers have a similar complexity to the human brain. Some people say that computers can never show true intelligence, whatever that may be. But it seems to me that if very complicated chemical molecules can operate in humans to make them more intelligent, then equally complicated electronic circuits can also make computers act in an intelligent way. And if they are intelligent they can presumably design computers that have even greater complexity and intelligence.” (Pg. 161)

This book will be absolute ‘MUST READING’ for anyone even remotely interested in scientific approaches to such questions.

38 persone l'hanno trovato utile

RICHARD-NICOLS François

Les plus récentes découvertes magnifiquement décrite.

Recensito in Francia il 19 gennaio 2024

Humour et clarté à la portée de presque tous. Le monde tel que la vraie science le découvre est infiniment plus intéressant que l'image que nous en avions. Si agréable à lire!

Amazon Customer

Exactly what you would expect from a book by Stephen Hawking.

Recensito nel Regno Unito il 17 gennaio 2024

We are lucky that we can read simple answers to concepts and questions written by such a man… although it does make me worry for the future of the human race.

Una persona l'ha trovato utile