Are you often in a trance, hoping to travel back in time and change history? Have you often fantasized about what the future would be like? Even though it is often thought to exist only in science fiction, the idea of traveling through time has captivated generations of people. But is it really as out of reach as it sounds?
Do you always seek the truth? Do you always have curiosity?
Admiring the night sky is one of the easiest ways you can travel through time. This is because it takes a long time for beams of light from other planets in the universe to reach us, and the things in the sky that you see are probably not what they really were at that time. In fact, it may be that by the time you see these distant stars, they will cease to exist. During the time it takes for the light they emit to reach Earth, they may develop into spectacular supernovae or disappear altogether.
From another point of view, it is often said that assuming that aliens had a powerful telescope, at this moment, sixty-five million light-years away, they could clearly see the real cause of the extinction of the dinosaurs. But that doesn't matter to us, because we can't see our own planet from sixty-five million light-years away. Perhaps one day in the future, we too can see this puzzling phenomenon in the universe, for example, we can also witness the ancient pioneers of other planets wandering their land.
Whether this is really time travel depends on whether you think of "seeing the past" as a kind of time travel. After all, our flesh can't go wherever it wants. In terms of actual movement, predicting the future, what you really need is speed. As long as you are in a faster reference frame, the slower your perception of the passage of time is relative to the slower moving reference frame, that is to say, you "foresee" the "future" of the slower reference frame, which is also known as the "clock slow effect".
At the same time, it means that if someone goes to space on a rocket, by the time they come back, they've effectively visited the future. In fact, this phenomenon is well documented... Like GPS navigation satellites moving so fast in orbit, the accuracy it maintains can be used to explain this phenomenon.
Every astronaut who has ever been in space is affected by the same less noticeable thing. In 2015, Russian astronaut Gennady Padaka broke the record for "the longest stay in space" — 879 consecutive days of missions. It has been said that, taken as a whole, the total time he moved at a higher speed meant that he moved 1/44th of a second into the future relative to Earth time. Although he moved very little time, not enough to make Gennady Padaka a time traveler, he still moved 1/44 more to the future than anyone else.
For all astronauts on the International Space Station, these tiny time trips are due to the high velocity of 17,100 miles per hour on the International Space Station in space. But for large-scale time travel, the International Space Station is not a convenient way. For example, it will take about 100 years for astronauts on the space station to advance 1 second into the future. The fastest manned spacecraft in history: the 1969 Apollo 10 Charlie Brown command module, flew at a record-breaking speed of 24,791 miles per hour — much faster than the International Space Station and another 10 years to move a little into the future. Even the fastest man-made objects have no chance to move more into the future.
During the solar mission, NASA's Parker Solar Probe has exceeded 150,000 miles per hour — of course there are no passengers on it, and we're some distance from an era when manned spacecraft could fly at such high speeds — and even if we could propel astronauts to that speed, it would take years to experience a few seconds of time travel on board the spacecraft. Traveling in time and space is never an easy task! In addition, gravity also affects time. The stronger the gravity acting on the object, the slower the flow of time.
This is actually another reason for the time difference between everyone and astronauts on Earth. Scientists have shown that atomic clocks close to Earth's surface go slower than atomic clocks farther away from Earth. Applying it to larger scales, many science fiction writers speculate that we can use the gravitational pull of huge objects to provide the necessary forward momentum for time travel. We can briefly sail into orbits of an unusually massive object— say, a black hole, and the enormous gravitational pull means that by the time we leave this massive object, we have traveled into the future.
Scientifically and mathematically, this can certainly be verified, but it's still an imperfect method for real-life time travel. First, even something as massive as a supermassive black hole can only slow you down by about fifty percent — so for people on Earth, a decade near a black hole could be the equivalent of twenty years on Earth.
Of course, the plan to "take a journey of decades to move another decade into the future" should not be scoffed at by us... But that's not so realistic, and there's another huge problem we're facing – distance. Specifically, as a way of time travel, you used a supermassive black hole at the center of the Milky Way galaxy, which is about 26,000 light-years away... So, if you're driving at the speed of light somehow, it's going to take 26,000 years to get there. Upon arrival, you carry out the plan to "turn ten years into twenty years" and fly back... When you finally return to Earth, you'll find that this is not the future you hoped for 20 years from now, but the future in 50,000 years — thanks to the time spent on the journey.
So while black hole time travel is theoretically feasible, don't expect to be able to harness its energy soon. For it to work, the black hole must be near us from the start... But if the black hole is really that close to us, it could destroy us and the solar system before we can use it for time travel.
Of course, when we imagine a time machine, we don't just want a device that can only take us to the future — we also want to make it possible to "travel through the past" (or at least return to the present from the future!). ）。
In general, most theories about "traveling back in time" argue that traveling back to the past is only possible when we are able to break the speed of light... But this would break the laws of physics and is generally considered impossible.
But is there any other way to go back in time?
Astrophysicist Ron Mallett believes there is, and he has devoted most of his career to pursuing what he loves all his life — to prove that time travel is possible. Malitte specialized in Albert Einstein's famous theories and proposed a way to travel through time in the past. This method involves "distorting" space-time without requiring the speed of light. Malitte said that by creating a gravitational field with a laser beam, space-time can be twisted into a ring, and you can travel all the way along the ring you made... Eventually go back in time.
If it's unbelievably perfect, it's because there's a huge pitfall: if you use Mallett, you can only go back in time to the moment when the machine started. This means that we can't go back to the age of the dinosaurs, or miraculously prevent past established events from happening. But this kind of machine is still very useful. Any future event worth restarting can be given another chance, while Malet's laser ring will greatly reduce the risk of future time travel. It can show time travelers through the future a way home, back in time and space where they originally existed, rather than actually moving from the "now."
This point in time disappears out of thin air. However, Mallett's views have been attacked by his peers, and he himself stressed that the technology is still a long way from becoming a reality.
Finally, the existence of living time travel also implies the existence of living crossers. But are they already among us? While no one attended Stephen Hawking's "Time Traveler Party," many have been declaring themselves from the future for years. A better example is John Titor, who claims to be from the 2000s looking for an IBM 5100 computer.
Titor's story is very interesting, but his predictions never came true, so his story is considered a complete hoax. In addition to Titor, there are many people who stand up to tell their crossover stories to the media, write mysterious blog posts, or make videos of crazy spreads, although in the end no one can really prove to the public that their cross-over stories are real. However, there have been a variety of images of time travelers throughout history, some of which have attracted public interest. For many, the fact that time travelers have not yet been confirmed is enough to prove that time travel never existed. But another segment argues that our skeptical tendencies toward time travel mean that even if humans one day invented time travel, we might not believe the narratives of the lucky ones who never came back to the present using the technology.
For now, we can still draw some solace from the fact that, at the end of the day, each of us, travels through the future at a constant speed of 1 second per second. It's not as fascinating as it is in the movies, but at least we don't run the risk of being stuck in the distant future or forgotten by time.
Fy: Long Smoke, Jeong Chul-han, Holy Joy, A-Yun of Amber River