Is your great-grandmother alive according to Einstein’s theory? – 06/04/2023 – Science

It was a random question. Sabine Hossenfelder was in a taxi with a young man, and when she informed him that she was a theoretical physicist, the young man asked, “A shaman told me that my grandmother is still alive because of quantum mechanics. Is that true?”

The young man might not know it, but Hossenfelder was the ideal person for him to ask that question. The scientist, who now works at the Center for Mathematical Philosophy at the University of Munich, in Germany, spends her time looking for answers to this type of question.

“That’s what interested me in physics from the beginning: all those big, hard-to-answer questions,” she told BBC News Mundo, the BBC’s Spanish-language service.

“Twenty years later, I still don’t have the answers, but if you ask me a question, I can give you a pretty long answer.”

These answers are reflected in press articles and in books such as “Lost In Math” (“Lost In Math”, in free translation, no version in Brazil) and “Existential Physics: A Scientist’s Guide to Life’s Biggest Questions” (“Física Existencial : a scientific guide to life’s biggest questions”.

Furthermore, she became known through her blog BackRe(Action) and her popular YouTube channel. Hundreds of thousands of people follow the scientist on the internet. “We’re drawn to mysteries,” she says.

“I think behind that attraction is the desire to understand how we fit into this universe, what these fundamental laws that we use in physics tell us about it,” explains Hossenfelder. “They don’t exactly answer all the big questions, but they do give us a clue as to what’s possible and what’s not.”

But back to the question at the beginning of this text: Can what the shaman said to the young man in the taxi be true?

Relativity

“I really didn’t know what to answer, because quantum mechanics itself doesn’t have much to do with the afterlife,” says Hossenfelder.

“But after thinking about it a bit, I came to the conclusion that it wasn’t completely fake.”

“If you leave quantum mechanics aside, it is true that our theories of space and time, which go back mainly to Albert Einstein, tell us something about the reality of the past and also the future, although the future is more complicated because of this quantum mechanics .”

Following that thread, she arrived at an answer to the peculiar question.

“What Einstein taught us, although I think it came as a surprise to him even that it was a consequence of his theory, is that fundamentally you can’t talk about the existence of this present moment without also acknowledging the existence of the past in exactly the same way.” , says Hossenfelder.

You’ve probably already noticed: the present is an instant between the past and the future.

If I ask what you’re doing now, you’ll answer that you’re reading this article, but even that answer has a bit of the past.

“Everything you experience, everything you see, you see it as if it were a small amount of time in the past”, details Hossenfelder.

That is, the moment “now” is impossible to describe.

Furthermore, “what we call the present moment may be the future or the past for someone else. Einstein called this notion observer independence.”

Einstein’s train

To understand better, let’s recall one of Einstein’s famous thought experiments.

Until then, two streams of physics thought differently: the Newtonians claimed that, when measuring the speed of light, it would be different depending on how you moved; the Maxwellians argued that the speed of light was always the same.

Einstein focused on a key element of speed: time.

And he realized that the statement about time was a question about what is simultaneous.

For example, if you say that a train arrives at the station at 7:05 am, this simply means that it arrives at the platform at the same time as the clock is reading 7:05 am.

But Einstein thought that this notion of things happening at the same time actually depended on how you’re moving. And that meant that the flow of time might not be the same for everyone.

To explain this, Einstein imagined a man standing on a train station platform. Suddenly, two bolts fall on either side of him at exactly the same distance. The light from each of the beams hits your eyes at precisely the same moment.

For that man, the two rays fell simultaneously. But at that very moment, a train traveling close to the speed of light is passing by. In it, there is a woman.

As light emanates from the spokes, the train moves towards one while moving away from the other.

The light from the ray ahead, towards the person on the train, reaches the woman’s eyes first, as the distance is shorter. The back ray light comes later.

That is, unlike the man on the platform, for the woman, time elapsed between the two rays: one fell before the other.

So if the speed of light is constant – and it is – which observer is right? Did the lightning strike at the same time or one after the other?

The answer: neither and both. Both have an equally valid perspective.

“All observers have the same rights, so to speak: their reality is no more real than mine,” observes Hossenfelder.

the present past

This impossibility of defining a notion of now is called “the relativity of simultaneity”.

“Einstein said that we have to treat time as a dimension, and he created an entity called space-time”, explains the theoretical physicist.

“Once you’ve done that, you can’t introduce a specific moment into the now, because that doesn’t work for all observers.”

Following this logic, if there is no unambiguous notion to define what happens now, points out Hossenfelder, then every moment can be “now” for someone.

This would include every moment of your past and your future.

“This leads to the conclusion that the past exists in the same way as the present,” says Hossenfelder.

This reasoning would lead us to think that the past in which your great-great-grandmother lives exists in the same way as our present.

“Of course, if you want to talk to your great-grandmother, none of this will help you… we don’t know how to do that yet,” he says.

And those last words caught our attention: what did she mean by “yet”?

The laws

“At this point, I have to admit that what follows are things that I believe, that I find interesting, but may or may not be correct”, says the scientist.

At the very least, we were intrigued, especially considering that Sabine Hossenfelder’s musings are derived from the study of fundamental physics.

“If you think about it, when someone dies, in a way, they continue to exist,” says Hossenfelder.

“What happens is that all the information that made up your personality – the specific connections of atoms, the synapses in your brain and so on – breaks down, falls apart. But we know, from the way the fundamental laws of nature work, that this information is not destroyed.”

“The only thing that happens is that it diffuses in subtle correlations in the remains of the body, gets entangled with other particles, spreads throughout planet Earth and, in the long run, throughout the universe.”

So: the information is still there, but for practical purposes it’s impossible to retrieve.

However, Hossenfelder wonders: who knows what will happen in a billion years?

“The universe will exist for some time, so there is potential for technological development,” says Hossenfelder.

“Even if the information that makes up a person is no longer in one place and we can’t talk to them, maybe someone will figure out how to do that. Or something can change in the nature of humans; maybe some cosmic consciousness also spreads and this information spreads. make them accessible again”, says the scientist.

“I know it sounds crazy, and I confess I have a hard time understanding this intuitively, but based on what we know about how our current theories work, it seems that our existence transcends the passage of time. There is something timeless about the information that makes us up, besides constituting everything in the universe.”

As Einstein wrote: “For us believing physicists, the distinction between past, present and future has only the meaning of an illusion, however persistent.”