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time travel

Would backwards time travel unravel spacetime?

Astrophysicist Ethan Siegel offers two scenarios where it wouldn’t: The second way out is to assume that the past isn’t written, and your actions do matter. The Universe, as it exists today, is not bound to the state its in right now if you travel back to the past. In a way, every action you take creates a new, alternate history for the Universe. You can kill your own grandpa before your parents are conceived; you can prevent your parents from meeting and falling in love; you can kill Hitler before World War II or assassinate Brutus and Cassius and Marc Antony before they assassinate Caesar. In short, you can change history. The only thing you have to give up, Read More ›

Astrobiologist: Why time travel can’t really work

Recently, cosmologist Carlo Rovelli, author of The Order of Time, argued that time travel, especially into the future, can work. However, astrobiologist Caleb A. Scarf sees an insurmountable barrier, which he calls the “spatial problem”: Let’s take the Earth’s motion around the Sun. A month of orbit corresponds to moving in an arc of approximately 78 million kilometers. During that same period the entire solar system will have also moved approximately 600 million kilometers around our galaxy, and our entire Local Group of galaxies will have swept through about 1.7 billion kilometers of space relative to the cosmic microwave background. Not only do you need to traverse those kinds of distances, you need to get it correct to within a Read More ›

Cosmologist Carlo Rovelli: Future time travel only a technological problem

Not a scientific one. Dan Falk interviews physicist Carlo Rovelli about “about the nature of time, whether it has a beginning and if humans might one day master time travel:” Could time travel ever be possible? Well, “time traveling” is what we do all our lives, isn’t it? But you mean, can we jump quickly to the past or to the future. Jumping to the far future is certainly possible. It’s only a technological problem, not a scientific one. One way is to move very fast. When you move fast, time passes very slowly for you — so if you could run fast enough around your house many times, you could do that in a time span which for you Read More ›

At the BBC: Still working on that ol’ time machine…

From the BBC: Albert Einstein thought the three dimensions of space were linked to time – which serves as a fourth dimension. He called this system space-time, and it’s the model of the Universe that we use today. But Einstein also thought it was possible to fold space-time, creating a shortcut between two distant locations. This phenomenon is called a wormhole, and it can be visualised as a tunnel with two openings, each emerging at different points in space-time. Wormholes might exist naturally in the cosmos; indeed, scientists in Russia are trying to use radio telescopes to detect them. But using wormholes for time travel won’t be straightforward. Indeed not. Unless everything is absolutely determined, some wise person from the Read More ›