What Might Time Travel Be Anyway?

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Do curso por The University of Edinburgh

Introdução à Filosofia

3524 classificações

The University of Edinburgh

Introdução à Filosofia

3524 classificações

Este curso apresentará a você algumas das principais áreas de pesquisa da filosofia contemporânea. Em cada módulo um filósofo diferente conversará com você através de algumas das questões e assuntos mais importantes da sua área de conhecimento. Primeiro iremos tentar entender o que é a filosofia - quais são seus objetivos e métodos característicos, e como ela difere de outras matérias? A seguir, usaremos o restante do curso para adquirir uma visão introdutória de várias áreas diferentes da filosofia. Tópicos que você irá aprender: Epistemologia, onde consideraremos que nosso conhecimento do mundo e de nós mesmos consiste em e como nós o obtemos; Filosofia da ciência, onde iremos investigar conceitos fundamentais da pesquisa e prática científica; Filosofia da Mente, onde levantaremos questões sobre quais são as implicações de ter uma mente, e como mentes deveriam ser entendidas e explicadas; Filosofia Moral, onde tentaremos entender a natureza dos nossos julgamentos e reações morais - se visam alguma verdade moral objetiva, ou se são apenas preferências pessoais ou culturais, e; Metafísica, onde iremos refletir sobre algumas das questões conceituais fundamentais sobre a natureza da realidade. O desenvolvimento deste MOOC, Curso Online Aberto e Massivo, foi liderado pelo centro de pesquisas Eidyn, da Universidade de Edinburgh. Para acompanhar 'Introdução à Filosofia', temos o prazer de anunciar o livro intitulado 'Phylosophy for Everyone' ou 'Filosofia para Todos' que foi adaptado a partir da obra de Routledge. Esse companheiro do curso de 'Introdução à Filosofia' foi escrito pela equipe de filósofos da Edinburgh, explicitamente, tendo em mente, as necessidades dos alunos deste MOOC. 'Filosofia para Todos' apresenta capítulos claros e de fácil utilização, resumos de cada capítulo, glossário, questionários, sugestões para leitura e guias para recursos online. Por favor, clique em 'Start Here' e navegue até a página 'Optional Reading' para obter mais informações.

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Time Travel and Philosophy

(Dr. Alasdair Richmond) In this module we'll think about some issues in metaphysics, a branch of philosophy that investigates the ways that reality could intelligibly be. Our case study will be the possibility, or otherwise, of time-travel. Some have thought that the apparent possibility of creating a machine that we could use to transport a person backwards in time can be ruled out just by thinking about it. But is time-travel really logically impossible? What would the universe have to be like for it to be possible? And can we know whether our universe fits the bill?

What Might Time Travel Be Anyway?7:18

Grandfather Paradoxes9:14

Two Senses of Change7:23

Conheça os instrutores

Dr. Dave Ward
Lecturer in Philosophy
University of Edinburgh
Professor Duncan Pritchard
Professor of Philosophy
University of Edinburgh
Professor Michela Massimi
Full Professor
Philosophy
Dr. Suilin Lavelle
Lecturer in Philosophy
University of Edinburgh
Dr. Matthew Chrisman
Reader in Philosophy
Philosophy
Dr. Allan Hazlett
Dr. Alasdair Richmond
Dr.
Philosophy
Guy Fletcher
Lecturer
Philosophy
Elinor Mason
Senior Lecturer
Philosophy

Hello from the past ladies and gentlemen. My name is Alasdair Richmond and I teach

philosophy at the University of Edinburgh, and I specialize in that branch of

metaphysics that looks at philosophical questions to do with time.

And in particular, time travel. And the aim of this talk is to give you a

short overview of the philosophy of time travel and some of the philosophical

problems that this topic throws up. The key text for this talk, is a 1976

paper by David Lewis, 1941-2001, called The Paradoxes of Time Travel.

And in that paper, Lewis tries to defend the logical possibility of backwards time

travel. So a really good way into the debate, is

to begin by looking at Lewis' definition of what time travel might actually

involve. And Lewis says, time travel involves a

distinction between two ways in which time could be registered, what you might call

external time on the one hand, and personal time on the other.

External time is time as it's registered by the world at large.

Which might be, times as it's registered by the movement of the tides, by the

rotation of the sun, by the movement of the air through space, by the sun rising

and setting. So external time is simply time as it's

registered by the majority of the non time traveling universe, time for everybody.

Personal time, on the other hand, is time as it's registered by a particular person

or a particular traveling object. So personal time for example might be time

registered by the traveler's watch. Time registered by the accumulation of the

traveler's memories, time registered by the accumulation of the traveler's

digestive products, time registered by the traveler's hair graying or cells dying.

Now for most us, and I'm going to assume for the purposes of this talk that most of

us aren't time travelers, external time and personal time march in-step.

If five minutes elapses for you, as recorded by your watch, by your digestion,

by your blood circulating, you should typically find that five minutes has

passed in the external world. But in cases of time travel, personal time

and external time diverge. And there are two ways in which this could

be imagined as happening. In case there's a forward time travel,

personal time and external time share the same direction, but they have different

measures of duration. Suppose for example, I depart from January

2013, in my time machine. And I arrive in January of 2063.

So 50 years has elapse in external time. But in my frame of reference, aboard the

machine measure by my watch, my digestion, the accumulation of my memories, all the

process that travel with me, only five minutes has elapsed.

So I get out the machine five minutes older, in personal time, only to find that

fifty years has elapsed in the extent of the world.

So this would clearly be a case of time travel.

Five minutes of personal time corresponds the same journey measures fifty years of

external time. So in case there's a forward time travel,

personal time and external time share the same direction, but different duration.

Cases of backward time travel, personal time and external time again diverge.

Remember that Lewis thinks that divergences between personal time and

external time aren't actually constitutive of time travel.

So in backward time travel, personal time and external time diverge, but they

diverge in direction. Suppose now, that my 5 minute personal

time journey from January, 2013, doesn't take me into the future, it takes me into

the past. So, I activate the machine, five minutes

passes for me. My watch shows an increase of five

minutes. Five minutes seems to elapse in my frame

of reference. But when I arrive, I've arrived in

January, 1863. So a journey that has five minutes

positive personal duration, has 150 years negative external duration.

So in backward time travel, personal time and external time diverge in direction.

So, in this case, five minutes positive personal time, measures the same journey

as a 150, year negative interval of external time.

Now a backward time journey has the peculiarity that in external time the

journey begins, after it ends. The journey ends in 1863, but it begins in

2013. So, says Lewis, given a distinction

between personal time and external time, it is at least possible to imagine both

forward time travel and backward time travel.

Now the details of this are slightly technical, but forward time travel seems

to be a very deeply embedded phenomenon, and one of our best supported physical

theories. Einstein's special theory of relativity

predicts that the rate at which time passes is not an absolute, not an

invariant, but varies according to relative speed.

In other words, the greater the relative velocity between two systems, the closer

that, that relative velocity comes to the speed of light.

The more that the rate of temporal passage diverges in those two frames of reference.

Now, if I'm lucky, I maybe have forty or even fifty years of personal time ahead of

me. And the Special Theory of Relativity says,

that if I travel fast enough relative to the solar system, I can make that forty or

fifty year interval of personal time, comprise tens, or hundreds, or millions,

or even billions of years of external time.

Provided that I travel fast enough, I can make my 40 years of personal time extend

through the entire future history of the Sun.

So forward time travel is very deeply embedded in Einstein's special theory of

relativity. And we have decade and decade of very well

supported physical results that suggests that these divergences between frames of

reference really, really occur. Backward time travel is a bit more

speculative, and whether physics permits backward time travel, is still something

that's naturally hotly contested. But the General Theory of Relativity seems

to predict that under certain circumstances, given an enormous amount of

mass, or an enormous density of mass, or enormously rapid movement of mass, it's

possible to create circumstances where personal time and external time diverge.

Not only in duration, but in direction. There's a famous model universe, by the

Austrian Mathematical physicist Kurt Godel, which describes a relativistic

possible universe where it's possible to t-, jump these into the local future that

can visit any point in the external past. So the General Theory of Relativity seems

to underwrite the kind of personal time, external time discrepancies, there's a

constitutive of backward time travel as well.

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