Time Travel is Possible. Einstein Taught Us That.
Is the time we experience in our day-to-day lives real? Theoretical physicist Brian Greene explores the potential particles of time and why we could, in theory, travel forward in time but not back.
Brian Greene is an American theoretical physicist and string theorist. He has been a professor at Columbia University since 1996 and chairman of the World Science Festival since co-founding it in 2008. Greene has worked on mirror symmetry, relating two different Calabi–Yau manifolds (concretely, relating the conifold to one of its orbifolds). He also described the flop transition, a mild form of topology change, showing that topology in string theory can change at the conifold point.
Greene has become known to a wider audience through his books for the general public, The Elegant Universe, Icarus at the Edge of Time, The Fabric of the Cosmos, The Hidden Reality, and related PBS television specials. He also appeared on The Big Bang Theory episode "The Herb Garden Germination," as well as the films Frequency and The Last Mimzy.
Brian Greene: We know a lot about time. We know that time in some sense is, at rock bottom, that which allows change to take place, right. When we say that time has elapsed, we notice that because things now are different from how they were a little while ago. That’s what we mean by time elapsing. But is time some fundamental quality of reality or is it something that our brains impose on our perceptions to organize our experience into some coherent framework that allows us to survive? I mean I can well imagine that we have been under evolutionary pressure over the millennia to organize perception so that we can survive, get the next meal, plan for the future. All of that would seemingly require that we have a conception of time that we apply to what we experience out there. But that doesn’t mean time as we experience it is real. It doesn’t mean that time as we experience it is how the world is actually structured. I mean there are many ideas that people put forward. The possibility, for instance, that, you know, we all know that matter is made of molecules and atoms. Could it be that time is also made of some kind of ingredient? A molecule of time? An atom of time? Is that really what time is at a fundamental level?
Time travel is absolutely possible. And this is not some sort of weird sci-fi thing that I’m talking about here. Albert Einstein taught us more than 100 years ago that time travel is possible if you’re focusing upon time travel to the future. And I’m not referring to the silly thing that we all age, right. We’re all going into the future. Sure, I’m talking about if you wanted to leapfrog into the future, if you wanted to see what the Earth will be like a million years from now, Albert Einstein told us how to do that. In fact, he told us two ways of how to do it. You can build a spaceship, go out into space near the speed of light, turn around and come back. Imagine you go out for six months and you turn around and you come back for six months. You will be one year older. But he taught us that your time is elapsing much slower than time back on Earth. So when you step out of your ship, you’re one year older, but Earth has gone through many, many years. It can have gone through 10,000, 100,000, or a million years depending on how close to the speed of light you traveled.
And he also taught us if you go and hang out near the edge of a black hole, time again will elapse more slowly for you at the edge of the black hole than back on Earth. So you hang out there for a while, you come back and again you get out of your ship and it will be any number of years into the future, whatever you want all depending on how close you got to the edge of the black hole and how long you hung out there. That is time travel to the future. Now, of course, what people really want to know about is getting back. Can you travel back to the past? I don’t think so. We don’t know for sure. No one has given a definitive proof that you can’t travel to the past. In fact, some very reputable scientists have suggested ways that you might travel to the past. But every time we look at the proposals in detail, it seems kind of clear that they’re right at the edge of the known laws of physics. And most of us feel that when physics progresses to a point that we understand things even better, these proposals just will be ruled out, they won’t work. But I guess I would say there’s a long-shot possibility based on what we know today that time travel to the past might be possible. But most of us wouldn’t bet our life on it.
Theoretical physicist Brian Greene is fascinated by time. Is the time we experience in our day-to-day lives real? Is our interpretation of time actually how the world is structured? Could time be broken up into particles like matter? These questions fuel Greene's curiosity, and their most likely answers indicate that time travel into the future is very much possible. But traveling back in time, well, probably not. Greene explains why.
Brian Greene is the chairman of the World Science Festival, running May 27-31 in New York City.
Explore how alcohol affects your brain, from the first sip at the bar to life-long drinking habits.
- Alcohol is the world's most popular drug and has been a part of human culture for at least 9,000 years.
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If you want to know what makes a Canadian lynx a Canadian lynx a team of DNA sequencers has figured that out.
- A team at UMass Amherst recently sequenced the genome of the Canadian lynx.
- It's part of a project intending to sequence the genome of every vertebrate in the world.
- Conservationists interested in the Canadian lynx have a new tool to work with.
If you want to know what makes a Canadian lynx a Canadian lynx, I can now—as of this month—point you directly to the DNA of a Canadian lynx, and say, "That's what makes a lynx a lynx." The genome was sequenced by a team at UMass Amherst, and it's one of 15 animals whose genomes have been sequenced by the Vertebrate Genomes Project, whose stated goal is to sequence the genome of all 66,000 vertebrate species in the world.
Sequencing the genome of a particular species of an animal is important in terms of preserving genetic diversity. Future generations don't necessarily have to worry about our memory of the Canadian Lynx warping the way hearsay warped perception a long time ago.
Artwork: Guillaume le Clerc / Wikimedia Commons
13th-century fantastical depiction of an elephant.
It is easy to see how one can look at 66,000 genomic sequences stored away as being the analogous equivalent of the Svalbard Global Seed Vault. It is a potential tool for future conservationists.
But what are the practicalities of sequencing the genome of a lynx beyond engaging with broad bioethical questions? As the animal's habitat shrinks and Earth warms, the Canadian lynx is demonstrating less genetic diversity. Cross-breeding with bobcats in some portions of the lynx's habitat also represents a challenge to the lynx's genetic makeup. The two themselves are also linked: warming climates could drive Canadian lynxes to cross-breed with bobcats.
John Organ, chief of the U.S. Geological Survey's Cooperative Fish and Wildlife units, said to MassLive that the results of the sequencing "can help us look at land conservation strategies to help maintain lynx on the landscape."
What does DNA have to do with land conservation strategies? Consider the fact that the food found in a landscape, the toxins found in a landscape, or the exposure to drugs can have an impact on genetic activity. That potential change can be transmitted down the generative line. If you know exactly how a lynx's DNA is impacted by something, then the environment they occupy can be fine-tuned to meet the needs of the lynx and any other creature that happens to inhabit that particular portion of the earth.
Given that the Trump administration is considering withdrawing protection for the Canadian lynx, a move that caught scientists by surprise, it is worth having as much information on hand as possible for those who have an interest in preserving the health of this creature—all the way down to the building blocks of a lynx's life.
The exploding popularity of the keto diet puts a less used veggie into the spotlight.
- The cauliflower is a vegetable of choice if you're on the keto diet.
- The plant is low in carbs and can replace potatoes, rice and pasta.
- It can be eaten both raw and cooked for different benefits.
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