The concept of time travel has captivated imaginations for generations, fueled by science fiction narratives like Doctor Who, Back to the Future, and The Time Machine. The tantalizing idea of journeying to bygone eras or leaping into the future sparks endless questions. But beyond the realms of fiction, How Can I Travel In Time according to the laws of physics? Is time travel merely a fantasy, or does science offer a glimmer of possibility?
While the Doctor’s adventures in the Tardis remain firmly in the realm of science fiction, physicists have been grappling with the nature of time and the theoretical possibilities of manipulating it for decades. Unlike the magic of the Tardis, real-world time travel, if achievable, would be rooted in the complex and often mind-bending theories of modern physics. So, let’s delve into what science actually says about how can I travel in time, separating fact from fiction and exploring the surprising truths about our universe.
Time Travel to the Future: A Scientifically Proven Fact
Perhaps surprisingly, traveling to the future isn’t just theoretical – it’s a scientifically proven phenomenon, thanks to Albert Einstein’s groundbreaking theories of relativity. A cornerstone of relativity is the understanding that time is not a constant, universal entity. Instead, time is relative, meaning its passage can vary depending on your speed and the gravitational forces acting upon you. This concept, known as time dilation, is key to understanding how can I travel in time into the future.
“This is where time travel can come in and it is scientifically accurate and there are real-world repercussions from that,” explains Emma Osborne, an astrophysicist at the University of York.
Time Dilation Through Speed: The Faster You Go, the Further You Travel in Time
One way to experience time dilation and effectively travel to the future is by moving at incredibly high speeds, approaching the speed of light. Imagine the famous “twin paradox”: if one twin embarks on a high-speed space journey while the other remains on Earth, the traveling twin will age slower than their Earthbound sibling. Upon returning, the spacefaring twin would have effectively traveled into the future relative to their twin on Earth.
Vlatko Vedral, a quantum physicist at the University of Oxford, illustrates this point: “If you travel and come back, you are really younger than the twin brother.” This isn’t just a thought experiment; astronauts like Scott and Mark Kelly have experienced slight time dilation, with Scott aging marginally slower during his extended stays in space. While their speeds weren’t close to the speed of light, the principle remains the same: speed affects time.
Time Dilation Through Gravity: Gravity’s Grip on Time
Another way to manipulate time and journey into the future is by experiencing intense gravitational fields, such as those near black holes. According to relativity, the stronger the gravitational field, the slower time passes. As Osborne humorously puts it, “Your head is ageing quicker than your feet, because Earth’s gravity is stronger at your feet.”
This concept was dramatically portrayed in the Doctor Who episode “World Enough and Time” and the film Interstellar. In these scenarios, characters near black holes experience time passing much slower than those further away, leading to significant time jumps into the future for those in the weaker gravitational field.
According to Albert Einstein’s theories of relativity, you can compress time if you are able to travel fast enough relative to those around you (Credit: Getty Images)
Real-World Applications: GPS and Time Travel
These relativistic effects are not just theoretical curiosities; they have practical implications in our everyday technology. Consider the Global Positioning System (GPS) satellites that guide us daily. These satellites experience both speed-related and gravity-related time dilation compared to clocks on Earth. As Osborne notes, “The clocks above click faster than the clocks on Earth” and require constant adjustments. Without accounting for these time differences, “Google Maps would be wrong about 10km (six miles) a day,” according to the European Space Agency.
In essence, relativity tells us how can I travel in time to the future: either travel at speeds approaching the speed of light or spend time in a strong gravitational field. While building a “time machine” in the traditional sense isn’t necessary for future time travel, achieving significant time jumps would require technologies far beyond our current capabilities.
Time Travel to the Past: A Far More Complex and Uncertain Journey
While future time travel is grounded in established physics, the prospect of traveling to the past is a much more perplexing and scientifically contentious issue. “It may or may not be possible,” states Barak Shoshany, a theoretical physicist at Brock University. “What we have right now is just insufficient knowledge, possibly insufficient theories.”
Relativity does offer some theoretical avenues for backward time travel, but these are highly speculative and fraught with challenges. Katie Mack, a theoretical cosmologist at the Perimeter Institute for Theoretical Physics, explains, “People tie themselves up in knots trying to find ways to rearrange space-time in order to make time travel to the past possible.”
Closed Time-like Curves: Looping Through Time
One theoretical concept is the “closed time-like curve,” a hypothetical path through space-time that loops back on itself. Imagine walking a path that eventually returns you to the exact point where you started, both in space and time. Such a path, mathematically described by logician Kurt Gödel in 1949, could theoretically allow for time travel to the past.
However, the existence of closed time-like curves is purely theoretical. Vedral emphasizes, “We don’t know whether this exists anywhere in the Universe. This is really purely theoretical, there’s no evidence.” Furthermore, even if they exist, creating or utilizing them seems incredibly improbable, even with advanced technology. Emily Adlam, a philosopher at Chapman University, suggests, “Even if we had much greater technological powers than we currently do, it seems unlikely that we would be able to create closed time-like curves on purpose.”
Even if we could create such loops, Vedral raises a philosophical concern: “You would literally be repeating exactly the same thing over and over again.” This concept echoes the Doctor Who episode “Heaven Sent,” where the Doctor is trapped in a time loop, reliving the same events for billions of years.
Cosmic Strings and Wormholes: Exotic and Unproven Possibilities
Another theoretical possibility involves “cosmic strings,” hypothetical one-dimensional objects with immense density that may have formed in the early universe. In a 1991 study, physicist Richard Gott proposed that if two cosmic strings moved past each other in specific ways, they could create closed time-like curves, enabling backward time travel.
However, the existence of cosmic strings is itself unproven. Mack points out, “We don’t have any reason to believe cosmic strings exist.” Even if they did, finding and manipulating them to create time loops seems astronomically unlikely.
Similarly, “wormholes,” theoretical tunnels through space-time that could connect vastly distant points, are sometimes considered potential time machines. Vedral acknowledges, “Wormholes are theoretically possible in general relativity.” The idea is that manipulating the ends of a wormhole could create a time difference, allowing for passage between different points in time.
However, wormholes, like cosmic strings, remain hypothetical. Osborne notes, “It’s been shown mathematically that they can exist, but whether they exist physically is something else.” Furthermore, even if they do exist, they are predicted to be incredibly unstable and microscopic in size. “Often wormholes are described as two black holes that have joined to each other,” explains Osborne, implying they would likely collapse under their own gravity.
Overcoming these limitations to make wormholes traversable and stable for time travel would require “negative energy,” a concept that is highly speculative and likely unattainable. Vedral concludes regarding wormholes as time machines, “It doesn’t sound like a very realistic proposal.”
Why is the Tardis a police box? The Tardis allows Doctor Who to travel through time. It also has an iconic appearance. Owing to a faulty camouflage system, it has got stuck in the form of an old British police box. Within the show, the camouflage function is called the chameleon circuit, which is a distressing mistake because chameleons mostly change colour to signal to each other, not to disguise themselves.
Quantum Mechanics and Retrocausality: A Mind-Bending Perspective
Beyond relativity, the realm of quantum mechanics, the physics of the very small, introduces even more bizarre possibilities and challenges to our understanding of time travel. One particularly strange phenomenon is “non-locality,” where entangled quantum particles can instantaneously influence each other, even across vast distances. Einstein famously called this “spooky action at a distance.”
Adlam explains that some interpretations of quantum mechanics propose “retrocausality” to explain non-locality. Instead of instantaneous action, retrocausality suggests that effects might travel forward in time and then backward, creating the illusion of instantaneity. “Instead of having an instantaneous non-local effect, you would just send your effect into the future, and then at some point it would turn around and go back into the past,” Adlam elaborates.
This interpretation challenges our intuitive understanding of time flowing linearly from past to future. However, retrocausality in quantum mechanics, even if real, is unlikely to offer a practical method for how can I travel in time in the way we imagine.
Adlam clarifies, “Retrocausality’s not quite the same thing as time travel.” The effects are observed at the subatomic level and are incredibly subtle. Scaling them up to macroscopic objects, like humans or time machines, is currently inconceivable. Furthermore, the nature of quantum retrocausality might prevent us from sending intentional messages to the past. As Adlam describes, manipulating these effects might require destroying the records of the past event you are trying to influence, making it unusable for practical time travel.
In quantum physics, an effect that occurs in one place can alter the state of something in another – it’s pretty spooky (Credit: Getty Images)
Conclusion: Time Travel – Future Achievable, Past Uncertain
So, how can I travel in time? Based on our current scientific understanding, traveling to the future is not only possible but a demonstrated phenomenon, thanks to the principles of relativity. By traveling at high speeds or experiencing strong gravity, we can effectively move into the future relative to the rest of the universe.
However, traveling to the past remains firmly in the realm of speculation. While relativity and quantum mechanics offer some intriguing theoretical possibilities like closed time-like curves, wormholes, and retrocausality, these concepts are either unproven, highly impractical, or may not even allow for the kind of controllable backward time travel we envision.
Shoshany concludes that our current theories are “incomplete,” suggesting that a deeper, unified theory of physics might be needed to definitively answer the question of past time travel. Until then, backward time travel remains a fascinating but likely impossible dream.
In the meantime, as you’ve reached the end of this article, you’ve already accomplished a form of time travel: you’ve journeyed several minutes into the future. Perhaps, for now, that’s the most reliable method of time travel available to us.
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