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Q:
How close have scientists come to making time travel possible?
A:
A: TOM GIBLIN, Associate Professor of Physics

The good news is that physicists have developed complete, tested and verified models of time travel that perfectly explain how objects (including humans!) can, and do, travel through time.

The bad news is that it’s the ultimate one-way street. We constantly are traveling through time, but our velocity in that direction is, with all the unfortunate consequences, unstoppable.

The theories of special and general relativity fully explain the rich physics of how to manipulate the rate at which clocks can tick due to large relative velocities and/or different altitudes — not to mention the even more significant effects of strong gravitational fields or near-light speed travel. It’s unavoidable to draw the analogy between these models and humans’ perception of how quickly time seems to pass; an hour in lecture can seem like a minute or a day depending on your frame of mind.

Understanding time travel, at least in this sense, is more than an academic exercise. The observable consequences of relativity are relevant in many of the processes that we take for granted. For instance, not a day goes by that I don’t rely on my GPS to tell me how long it will take for me to get home. This technology would be useless without a careful understanding of why the clocks on the GPS satellites tick at a (relative) different rate to those we have in our phones.

The great mystery, however, is not the fact that we travel through time in one direction, but rather why we travel in one direction. Macroscopic physics — thermodynamics, to be exact — dictates the rules that compel us forward, and forbid us to travel backwards, through time. On the other hand, microscopic physics has (almost) nothing to say about the choice of early versus late or young versus old. All microscopic laws of physics are time-reversal symmetric, meaning that these laws don’t care if time goes forward or backward. The origin of the arrow of time, the principle that dictates that we bleed after we’re cut, is an open question in physics. 

In short, we’re great at time travel; we know a lot about how time works and have harnessed its power in multiple ways. The limitations of this model that get us down, but these same limitations help our GPS get us to where we need to go.

Q:
Are we repeating history?
A:
GEORGE GOLDMAN '20, History Major from Boston

A: GEORGE GOLDMAN '20 | History Major from Boston

This question reminds me of a history class I took called “Modern History of the Middle East.” In the class, we learned about the recent wave of protests and revolutions (the Arab Spring) that took place from 2010 to 2012 throughout the Middle East in countries like Tunisia, Egypt and Syria. We discussed how protests often happen in cycles; in other words, they come about as a part of a larger historical pattern in which revolts of collective action against the government rise, fall, and make way for the next cycle to continue the trend.

For instance, the Young Turks Revolution of 1908, the Egyptian Revolution of 1952, and the Iranian Revolution of 1978-79 each were a part of a distinct protest cycle in which the people rose up against the government. However, history did not completely repeat itself in each case. The methods and eventual outcomes of the protests all were very different.

American writer Mark Twain once said, “History doesn’t repeat itself, but it often rhymes.” After taking “History of the Modern Middle East,” I learned how the Arab Spring protests were not a complete repeat of history, but instead a sort of rhyme with history. For sure, ideas, goals and traditions continued from one protest cycle to the next, but the kinds of people protesting and the results of the protests were often very different. As a history major myself, I have learned that your question is one that has kept many a historian busy.