Can information travel to the past?

When I read the question from today's consultation I thought "why do you ask it like that, instead of asking if it is possible to travel to the past?"

But I love that it is that way.

What occurred to me is that the reader who asked this must think that for teleportation we are a complex organism and that, therefore, you are not going to risk your life, because on the other side you would have to be rebuilt.

And yet, a message, if you send it digitally, 0 and 1, might make that time travel easier.

There is a very cool paradox about messages traveling through time and it is widely used in the field of quantum information.

This paradox is the following: someone writes a book in the past that solves all of humanity's problems: goodbye to wars, goodbye to diseases... In the future, you read the book and say to yourself "this person is my idol, "I'm going to travel back in time to meet her."

You travel to the past and you meet that person, but when you find him, he tells you: “I haven't written a book.”

You show it to them and insist: “Yes, yes, look, this is the book you are going to write.”

And then you give him the book, and he publishes it.

That information has traveled to the past and that person has received it.

But where did that information come from?

Where was it generated?

In the past or in the future?

That is the formulation of the question.

And to answer your question I am going to explain why we cannot send information to the past.

I start from the idea that we can send information to the future, for example, by writing a book.

But not to the past.

First because we don't have a time machine, at least not yet.

And second, can you build a time machine?

On a theoretical level, yes.

From a mathematical point of view, yes it is possible.

Wormholes, in theory, would allow such a machine to be built.

More information

Does the fifth dimension used in physics really exist?

A wormhole is a hypothetical tube-shaped structure whose open ends would be at two different points in space-time.

Moving through the hole would allow you to go from one of those points to another, so, also hypothetically, it would allow you to travel in time.

But, at the moment, no evidence has been found that space-time actually contains these structures, so it is a theoretical possibility.

This is the theoretical field in which I have worked, and I did my case, precisely, with a wormhole.

Such a hole that functions as a time machine is a theoretical possibility that can be built within the laws of physics.

But in reality it is not possible because, on the one hand, all time travel constructs require something completely exotic, an exotic matter or an exotic space.

And by exotic I mean that it is not something that we know in our physical world like matter or energy or any of the systems that we know.

I mean, you can think, theoretically, that maybe you could build that machine with negative energy, but in our world we have never seen anything with negative energy or mass.

And also, if you have a time machine and you try to put something in there, what happens?

Even if you managed to build that machine because you obtained the necessary exotic material, the way to put something in one of those machines so that it comes out the

other side

will surely end up destroying that information.

In short: the paradox is easily solved, since, although I have a wormhole that works as a time machine, when I bring that information closer to that hole it is as if there was a wall there that destroys the message I want to send. .

These time machines, therefore, would be very difficult to build due to the difficulty of obtaining the necessary exotic matter, but even if you built them, they have horizons and forces operating at their entrance that would prevent anything from entering and leaving unharmed.

So even if theoretically it could be built, it would not be effective because it could not be used for anything.

Ana Alonso-Serrano

is a researcher at the Humboldt University of Berlin and the Max-Planck Institute for Gravitational Physics in Potsdam (Germany).

Question sent via email by

Pedro Santangelo

.

Coordination and writing: 

Victoria Toro

.

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is a weekly scientific consultation, sponsored by the Dr. Antoni Esteve Foundation and the L'Oréal-Unesco 'For Women in Science' program, which answers readers' questions about science and technology.

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