British physicist Stephen Hawking threw a party in 2009 for time travelers. However, he didn’t send out the invitations until 2010. (No guests showed up). Most likely, time travel is not conceivable. Hawking and others have claimed that even if a time machine were attainable, it would be impossible to visit events before the moment it was constructed.
What about time travel, though? And that’s a different yarn. Some might call the idea crazy.
We are all time travelers, of course, because we are carried along by the flow of time at the pace of one hour per hour, from the past to the future.
Still, just like a river, the current varies in speed depending on where you are. The current state of science provides various options for gaining a head start on the future.
1. Rapidly Traveling Through The Past
Going very quickly is the most straightforward and workable method of time travel.
At velocities close to that of light, time seems to pass more slowly for a moving observer, as predicted by Einstein’s theory of special relativity.
This is not a theoretical possibility; it has been experimentally verified. By using two identical atomic clocks, one of which was flown in a jet aircraft and the other on the ground, physicists could demonstrate that the faster the plane was moving, the slower the clock ticked.
The impact on the planes is negligible. When traveling at 90% of the speed of light, however, time passes about 2.6 times more slowly than it does on Earth.
And time travel becomes even more intense as you approach the speed of light.
The protons flying through the Large Hadron Collider at 99.9999991% the speed of light are perhaps the fastest objects ever created by human technology. Using the theory of special relativity, we may determine that a proton’s second is comparable to 27,777,778 of our seconds, or almost 11 months.
Surprisingly, particle physicists must account for time dilation when working with particles that decay. The half-life of a muon decays in 2.2 microseconds under laboratory conditions. However, muons with high velocities, as those produced when cosmic rays hit the upper atmosphere, require ten times as much time to decay.
2. Gravitational Time Travel
The next time travel concept draws further inspiration from Einstein. His general theory of relativity states that the stronger one’s sense of gravity, the slower the passage of time.
For instance, the force of gravity increases as one approaches the Earth’s core. When you’re walking, time passes more slowly than you think.
This effect has been quantified once again. Researchers at the National Institute of Standards and Technology (NIST) in the United States measured the time difference between two atomic clocks mounted on shelves 33 centimeters apart in 2010.
Because of the slightly stronger gravity, it experiences, the lower one ticks at a slower rate.
A region of extraordinarily intense gravity, like a black hole, is all that is required for time travel to the far future. Moving closer to the event horizon causes time to slow down, yet crossing the border is fraught with danger and results in permanent imprisonment.
Time might appear to slow slower in the presence of gravity. Wikimedia Commons for the win!
And even if it were, the effect is weak so it wouldn’t be worth the trouble.
Getting to a black hole (the nearest is around 3,000 light years away) would cause more time dilation than orbiting the black hole itself if you could get there.
As Kip Thorne, the film’s scientific advisor, explains, the condition shown in Interstellar—in which one hour on a planet near a black hole is comparable to seven years back on Earth—is so severe as to be unachievable in our Universe.
Amazingly, GPS systems need to consider time dilation effects (caused by the speed of the satellites and the pull of gravity) to function correctly. Without these corrections, your phone’s global positioning system (GPS) wouldn’t be accurate within a few kilometers.
3. Suspended Animation as a Means of Time Travel
It’s possible that you can go into the future by slowing down or stopping your body’s functions and then starting them up again later, altering your experience of time in the process.
When the appropriate circumstances of temperature, moisture, and nourishment are fulfilled, bacterial spores can remain dormant for millions of years. While in hibernation, some mammals, including bears and squirrels, can drastically reduce their cells’ need for food and oxygen by slowing their metabolism.
Will people be able to do this?
Although it is likely beyond the technological capabilities of the present day to entirely halt your metabolism, some researchers are working on a method to induce a short-term hibernation lasting at least a few hours. If this happens, a cardiac arrest victim may have just enough time to make it to the hospital.
The future is shown by the sci-fi show Lost in Space. Wikimedia Commons for the win!
In 2005, American researchers showed that mice (who don’t hibernate) might have their metabolism slowed by exposing them to low concentrations of hydrogen sulfide, which binds to the same cell receptors as oxygen. The mice’s metabolic rate was reduced by ten, and their core body temperature dropped to 13 degrees Celsius. Mice might be safely resuscitated after being dead for six hours.
Unfortunately, the same studies on sheep and pigs did not provide positive results, suggesting the procedure may not apply to larger animals.
Replacement of the blood with a cold saline solution has been successful in pigs and is undergoing human clinical trials in Pittsburgh.
4. Using Wormholes to Go Back In Time
Wormholes are theoretical shortcuts across space-time that can potentially connect locations a billion light-years apart or further back in time.
The quantum scale is far smaller than an atom, and many physicists (Stephen Hawking included) think wormholes are continually appearing and disappearing at this scale.
Capturing one and expanding it to human size would be tricky and require a lot of energy, but it’s theoretically conceivable.
The incompatibility of general relativity with quantum mechanics has prevented any successful attempts to prove either side of the debate.
5. Light as a Medium for Time Travel
American scientist Ron Mallet proposed a different method of time travel in which a rotating cylinder of light would warp space-time.
Dropping something within the rotating cylinder would cause it to be propelled across time and space, much like a bubble in a cup of coffee when you stir it with a spoon.
In Mallet’s view, time travel into the past or the future is possible if one employs the appropriate geometry.
Mallet has been trying to get funding for a proof of concept experiment involving dropping neutrons through a circular arrangement of spinning lasers since he published his theory in the year 2000.
However, his ideas have failed to gain traction in the physics community at large, with some critics claiming that a fundamental premise of his model is dogged by a singularity (a fancy word for “it’s impossible”).