The river of time, running endlessly. Time is both familiar and strange to us, familiar is that everyone feels its existence in their daily busyness, strangeness is that no one can really say it clearly, and even whether it exists objectively is still controversial...
Time Rider – Stephen Hawking
The late British theoretical physicist Stephen Hawking once wrote the popular science community's god work "A Brief History of Time", and he studied the problem of time deeply. In fact, the original name of "A Brief History of Time" was "From the Big Bang to the Black Hole", and the publisher felt that this name was too 2B, so it changed it to "A Brief History of Time". However, when translated into the Chinese edition, Mr. Wu Zhongchao, a student of Hawking, titled the book "A Brief History of Time- From the Big Bang to the Black Hole" in the first edition of the domestic first edition, the First Promotion Series.
What is from the Big Bang to the Black Hole? It is from the beginning of time , the Big Bang singularity to the end of time — the black hole singularity, from the beginning to the end. He also proposes a new idea in the book, called the boundaryless condition, under his conjecture, time has no beginning and no end, and the universe has neither a beginning nor an end... It can be seen that Hawking's study of time is deep.
The iron law of time – the law of cause and effect
When it comes to time, it is inevitable to face a fundamental law of the universe, the law of cause and effect. This is a fundamental law on which all the laws of physics exist, imagine what would happen if the law of causation did not exist? What a ridiculous world would it be if there was no reason for an event to occur, or if the outcome of an event preceded its cause? All laws will cease to exist, and physics will cease to exist... (Suddenly remembered the story in "The Three-Body Problem" where physics does not exist)
The singularity in the Big Bang singularity (the beginning of time) and the singularity of the black hole (the end of time) in a brief history of time come from the singularity theorem (also known as the singularity theorem) that Hawking and his friend Penrose jointly proved, and one of the preconditions when they proved the singularity theorem was that the causal law was true!
The premise that the law of causation is established is that time must be unidirectional, which seems to us to be taken for granted, but for physicists this seems a bit strange, because almost all physical laws except thermodynamics are time reversible, that is, almost all physical laws are still true in the case of time inversion. For example, in a classic mechanical experiment, you can't tell whether the video is playing or reversing based on the images you see.
Especially after the theory of relativity was proposed, because there was no absolute time, the one-way nature of time was challenged, and the possibility of time travel was proposed, so there was the so-called grandfather paradox (also translated as the grandmother paradox). Hawking, a staunch advocate of the law of causality, did not believe in the fact that there was time to travel back in time, so he devised a clever experiment.
A time party for time travelers
At 12:00 noon on June 28, 2009, Hawking arranged a party at the University of Cambridge in the United Kingdom, pulled up a banner that read "Welcome Time Travelers," and waited quietly alone.
Until the end of the scheduled time, there is no future person who travels through time to be present...
The day after the party, Hawking publicly sent out an invitation letter "Professor Stephen Hawking sincerely invites you to the Time Traveler Party" with the space-time coordinates of the party attached. That is to say, he only published the information about the event at the end of the event, and this ingenious experimental design can both inform future humans who can travel through time and avoid modern people posing as future time travelers.
Why aren't future time travelers participating?
So the question is, since an invitation has been sent to the future, why has no one come to participate? The most direct reason, of course, is that time is irreversible, that is, it is impossible to go back to the past, that is, it is conditioned by the law of cause and effect. This is the view of most people, and it is also the point that Hawking wants to prove through this experiment. Is there anything else possible? Yes! I'll try to enumerate a few:
1, before the discovery of the method of time travel, human beings are extinct, human civilization disappears, and no one knows about this experiment.
2. The future time-space travel behavior is limited by legislation, and it is not allowed to interfere in the past, and it is not allowed to intervene in the past human history.
3. The experimental records of Hawking's time party did not circulate until the time travel was achievable.
4, highly developed future human beings disdain to participate in the experimental activities of a primitive human.
……
You go on to add...
(The above pictures come from the future, if there is infringement, please contact to delete)