Most of us, and as referenced in H.G. Wells’ The Time Machine (1895), have dreamed of time travel, a fascinating sci-fi concept that has existed for hundreds of years and one that represents one of man’s wildest fantasies. Surprisingly, recent work has shown us that the idea of moving between different points in time is far more than just science-fiction. In fact, a number of researchers, including astrophysicist Ethan Siegel have found some tentative support when it comes to the concept’s feasibility.
In a blog post for Forbes, Siegel has explained that according to Einstein’s theory of general relativity – completed in November 1915 and one that cuts to the core of our understanding of the universe – traveling back in time to alter the past is technically possible through a number of different methods. One such proposed method is via wormholes.
The place to start when it comes to wormholes is to understand what these space and time shortcut passages represent. In theory, wormholes, a term coined in 1957 by American theoretical physicist John Archibald Wheeler, are tunnel-like space connections created by very strong, dense, positive and negative energy fluctuations occurring in the fabric of space and time that bridge two vastly distant points of the universe with one another. Under this theory, Siegel explains that you could have a wormhole if the above-mentioned fluctuations-each create a curved space connection that opposes the other. If the connection lasted long enough, theoretically a particle could be transported through.
But still, for a wormhole to be traversable, apart from discovering particles with a negative energy and mass, it would also need to create a supermassive black hole and negative mass/energy counterpart. According to Siegel, in theory, after the wormhole as a flexible space and time passage has connected the black hole with its negative mass/energy counterpart, this, in his view, “should allow for a traversable wormhole.”
It goes without saying that Siegel’s theory is also based on the concept of bending space and time sprung from Einstein’s theory of General Relativity, which after describing the physical fabric of the universe as a four-dimensional body that includes three spatial dimensions, along with the combined concept of space and time, also identified the method of wormholes as theoretical space portals that “can transfer matter through to another dimension”.
Recently, evidence for this theory has moved beyond science-fiction. A couple of years ago, Spanish scientists built a magnetic wormhole which is not quite a space-time wormhole. The model, however, created a portal for magnetic fields by making a magnet disappear at one end of the wormhole, seemingly leaving space altogether, to only appear again at the other end of the wormhole. The transfer of the magnetic field was achieved via a process that is magnetically undetectable and only visible by light.
While this magnetic wormhole doesn’t exactly teleport particles or become scalable so that a human could pass through and get teleported across space and time, it does highlight the fact that important advances are being made and that perhaps, one day, we will be able to manipulate space and time in a similar manner.
Another potential time travel method is time dilation.
“If you travel close to the speed of light, you experience a phenomenon known as time dilation,” Siegel writes. “Your motion through space and your motion through time are related by the speed of light: The greater your motion through space, the less your motion through time.”
In other words, the closely linked theory of general relativity-time dilation effect, basically allows motion in space to actually alter the flow of time. Based on that idea, imagine traveling at almost the speed of light (300,000 km/sec) and reaching a destination that was 40 light years away in only a year, and then spend another year to come back. According to Siegel, while you might reach your destination in only a year, due to the time dilation effect that creates a difference of elapsed time between two events, and to length contraction, when you returned to Earth more than 80 years would have passed. This is not only because time moves slower for Earth-like objects that are near strong gravitational fields, but also because time travels forward and is dependent only on how fast you are moving through space.
So in a sense, by spending time away from planet Earth and returning at a later point, a human could fast forward through time. If you could get close to a black hole (theoretically speaking of course, given that for the time being the probability of that event happening is zero…spinning black holes bend space-time themselves ; they are so massive, powerful and all-consuming that anything including light gets trapped forever once it passes their event horizon, also known as the ‘point of no return’), due to its density and therefore intense gravitational forces in the vicinity, thousands of Earth-years might pass by while you as a traveler experience the presence as just a few seconds. While this sort of time travel is completely possible by the known laws of physics and based on very solid scientific ground, it allows only travel into the future, not into the past.
This is not the case though with wormholes. Siegel argues that if “we talk about the same speeds as we did earlier, the “in motion” end of the wormhole would have aged 40 years, but the “at rest” end would only have aged by one year. Step into the relativistic end of the wormhole, and you arrive back on Earth only one year after the wormhole was created, while you yourself may have had 40 years of time to pass.”
Which is to say that if someone had created a pair of entangled wormholes 40 years ago, it would be possible to selectively travel back in time by stepping “into one of them today, in 2017, and wind up back in time at the mouth of the other one… back in 1978”. Luckily, this form of time travel excludes the possibility of the proposed grandfather paradox – a hypothetical scenario in which someone via a “closed timelike curve,” which is the result of an extremely powerful gravitational field such as that produced by a spinning black hole, travels back through time to murder his/her own grandfather, preventing in the process his/her own later birth.
Concluding, Siegel adds: “A great many unusual things become possible in the Universe if negative mass/energy is real, abundant, and controllable, but traveling backwards in time might be the wildest one we’ve ever imagined.”