We Are All Time Travelers
(To the future)
Google shows well over 100,000 references to “Time Machine,” a phrase that first appeared in an H.G. Wells novella in1895. Throughout the centuries, the idea of time travel has captured the imagination of everyone from the average “Jane” to Nobel Prize-winning physicists. While time travel has been fantasized, fictionalized, filmed and debated, there is no real consensus on the viability of traveling forward or backward in time.
In April 2007, Stephen Hawking wrote, ”Time travel was once considered scientific heresy. I used to avoid talking about it for fear of being labeled a crank. But these days I’m not so cautious. In fact, I’m more like the people who built Stonehenge. I’m obsessed by time. If I had a time machine, I’d visit Marilyn Monroe in her prime or drop in on Galileo as he turned his telescope to the heavens. Perhaps I’d even travel to the end of the universe to find out how our whole cosmic story ends.”
In physics, time is described as a dimension just like the three we commonly think of: length, width and height. When traveling from your house to the work, however, you are not only moving in 3-D, but traveling forward in time, the fourth dimension. From this perspective, we are all Time Travelers, moving at the rate of 1 second per second in the direction of the future. Or are we?
Interestingly, we live about 80 milliseconds in in the past. Use one hand to touch your nose, and the other to touch one of your feet, at exactly the same time. You will experience them as simultaneous acts. But clearly, it takes more time for a signal to travel from your feet to your brain than from your nose to your brain. The reconciliation is simple: our conscious experience takes time to assemble, and your brain waits for all the relevant input before it experiences the “now.” Experiments have shown that the lag between when things happen and when we experience them is about 80 milliseconds. (per David Eagleman.)
Here you are, living in the past yet moving towards the future, so time travel is clearly possible. The challenge is to travel through time in increments that are perceptible: hours, days, years, decades and centuries. That brings us to Wormholes and Time Dilation, two of the most prominent theories of time travel.
A wormhole is a theoretical ‘tunnel’ or shortcut, predicted by Einstein’s theory of relativity, that links two places in space-time – visualized above as the contours of a 3-D map. Here, negative energy pulls space and time into the mouth of a tunnel, and it emerges in another space and time.
As illustrated above, a beam of light traversing a path between two points in curved space-time will take longer to complete the journey than a hypothetical spaceship taking advantage of a wormhole’s shortcut. **
While Wormholes are only hypothetical constructs, many physicists believe that they do exist, although microscopic in size and equally so in duration. Down at the smallest of scales, smaller even than atoms, we get to a place called the quantum foam. This is where wormholes are believed to exist. Tiny tunnels or shortcuts through space and time constantly form, disappear, and reform within this quantum foam, and they actually link two separate places and two different times.
Unfortunately, these real-life time tunnels are just a billion-trillion-trillionths of a centimeter across and last well under a billionth of a second. Some scientists theorize that it may be possible to capture a wormhole and enlarge so it becomes big enough for a human, or even a spaceship, to enter. Given enough power and advanced technology, perhaps a giant wormhole could be constructed. If so, it would be a truly remarkable device. One end could be here, near Earth, and the other far, far away, in some distant galaxy.
Theoretically, a time tunnel or wormhole could do even more than take us to other planets. If both ends were in the same place, and separated by time instead of distance, a ship could fly in and come out still near Earth, but in the distant past. Maybe dinosaurs would witness the ship coming in for a landing! Astro-physicists have theorized that the power necessary to keep a wormhole open will not exist in the foreseeable futures; but how often have we heard that, only to be proven wrong?
Time Travel to the Future Made Easy (-er)
In my second post, “7 Theories on Time That Would Make Doc Brown’s Head Explode,” the author’s talked about how, “The Faster You Go, the Slower Time Moves” and “The Higher You Live, the Faster You Age.” These are the keys to time travel, and they arise from Einstein’s work during his prolific period of 1905-1922. We can save the detail for later, but Einstein proved that acceleration and gravity were essentially indistinguishable. Both of these concepts are related to time dilation, and it happens because gravity warps time as well as space. The closer you are to the ground, the more you are affected by the Earth’s gravity and the slower time moves. On the other hand, as you get higher, gravity’s pull weakens and time speeds up.
Additionally, the faster you travel, the slower time moves. ( See Time Dilation http://www.phys.unsw.edu.au/einsteinlight/jw/module4_time_dilation.htm) You may already know this, thanks again to Einstein – if you’re going the speed of light, time pretty much stops. We can save the math for another day, **but in his famous work on special relativity in 1905, Albert Einstein predicted that when two clocks were brought together and synchronized, and then one was moved away and brought back, the clock that had traveled would lag behind the clock that had stayed put. Einstein considered this to be a natural consequence of special relativity, not a paradox as some suggested, and in 1911, he restated and elaborated on this result as follows:
“If the stationary organism is a man and the traveling one is his twin, then the traveler returns home to find his twin brother much aged compared to him. The paradox centers around the contention that, in relativity, either twin could regard the other as the traveler, in which case each should find the other younger—a logical contradiction. This contention assumes that the twins’ situations are symmetrical and interchangeable, an assumption that is not correct.”
Furthermore, accessible experiments have been done that support Einstein’s prediction. In 1911, Paul Langevin gave a “striking example” by describing the story of a traveler making a trip traveling at 80% of the speed of light. The traveler remains in a projectile for one year of his time, and then reverses direction. Upon return, the traveler will find that he has aged two years, while 160 years have passed on Earth. [[**See Wikipedia – Twin Paradox]] Thus, the traveling twin will have travelled 160 years into the future while his clock shows only 2 years have past!
This is not supposition and has been verified through rigorous and continuous experiments since 1911. While theoretical problems persist, i.e. long term space travel and the absence of the vehicle that can attain anywhere near 80% the speed of light, it is indeed foreseeable that this issue will be overcome in the century ahead of us.
The Case Against Travel To the Past
We will spend time discussing this concept at a later time, but suffice it to say that the overwhelming consensus is that it is not possible under current laws of physics to travel backward in time. If travel to the past were possible, the world would be filled with billionaires making their riches from betting on sporting events. Moreover, have you ever heard of anyone sanely stating, “Hello, I am from the future.”
As Robert A. Heinlein concluded, “His older self had taught his younger self a language which the older self knew because the younger self, after being taught, grew up to be the older self and was, therefore, capable of teaching. ”