Neil deGrasse Tyson Explains the Strange Paradoxes of Time Travel

Astrophysicist Neil deGrasse Tyson explains the nature of time and the conundrums of time travel in a recent interview.


Astrophysicist and science educator Neil deGrasse Tyson gave a fascinating interview recently to Jake Roper of Vsauce3, where he talked at length about the nature of time and the possibility of time travel.

Tyson thinks the most dramatic impact on our current understanding of time came from Einstein's discovery of general relativity. Time stopped being a linear, necessarily sequential idea where “we are all participating in the same ticks of the clock,” as Tyson says. With relativity, time became a more fluid concept, dependent on the observer.

Because of relativity, we learned that there is no “absolute time”.

“Time is relative, so time can be stretched, for me relative to you. So, time has multiple, sort of, parallel rates at which it flows, depending on the state of who's making the measurement and the state of who's in motion, and what conditions they are in,” said Tyson (0:53).

Tyson rather thinks of time as a dimension, calling us “prisoners of the present”. What he means is that we don’t have an ability to jump into the past or the future on our individual timelines. But what if we could do just that?

If time travel was feasible, we’d open ourselves up to some potentially mind-bending situations and logic puzzles. 

“Suppose you could move around in your timeline with the same flexibility as moving left and right, up and down, forward and backward. If that's the case you can revisit your own timeline. Under those conditions you do not die. You are always dying. You are not born. You're always being born. That's another kind of interesting way to think about time,” explained Tyson (1:34).

Some classic time paradoxes come out of this thinking. They revolve around the changes that can be imagined by suddenly being able to go back and forth in time.

If you jumped into the future, would you then know and remember everything that would have happened to you had you stayed in your original timeline and let events take place naturally?

And if your timeline already exists, could you change your fate by changing aspects of your future, if you managed to travel to it, like in the classic sci-fi movie franchise “Terminator”.

Neil deGrasse Tyson, astrophysicist, 'Cosmos' television show host and Frederick P. Rose Director of the Hayden Planetarium at the American Museum of Natural History speaks August 4, 2014 after a screening of James Cameron's 'Deepsea Challenge 3D' film at the museum in New York.  (Photo credit: STAN HONDA/AFP/Getty Images)

 Tyson hypothesizes that maybe you could alter your timeline, creating a new one as part of a “very complex, sort of, fractal structure”. And if this was possible, Tyson really doesn’t agree with some of the unnecessarily complicated plot choices of the "Terminator":

“So, what gets me about Terminator is he's got to kill everybody who might be the mother of the future of the person who overthrows the thing… You can go further back [in time] just have one little thing change and everything after that would change.”

In an example of another strange conundrum, Tyson also explores the idea of a particle that is never created nor destroyed and only exists in a time loop, a concept called “the Bootstrap Paradox”. In the time-travel movie “Somewhere in Time”, this “self-created” object was a locket which the lead character received as a gift from an old woman who told him to meet her back in time. He figures out how to go back in time, meets her when she's young and gifts her the same locket that she gave him back in the future. Once he did that, the origin of the object became uncertain and it got trapped in the time loop.

Another potentially big player in time travel - the infamous Butterfly Effect. It's a concept from chaos theory which basically says that small initial causes can create large ripple effects. If you were time traveling, could you too easily change the course of history?

Tyson isn’t so sure that if you, let’s say, go back and kill baby Hitler that you’d really change anything.

“You pivot everything on this one thing and tell me that all of civilization will be different. I'm not buying it. Civilization is more robust than that. And if Hitler were killed as a child, then no, maybe not - the Germans were ripe to have somebody rise up and take control of their psyche. And maybe the circumstances made Hitler - not Hitler making the circumstances,” pointed out Tyson (10:27).

In the end, Tyson doesn’t believe that travel back in time is possible, agreeing on that with Stephen Hawking. He thinks that at some point, physicists will discover a new law that will explain what prevents backwards time travel, adding “we don't know what that law is or why it must exist but everything we can imagine that allows it totally messes everything up.” 

While this is still just a hypothetical discussion, Tyson sees definite value in speculating about time travel. On the other hand, he takes comfort in living a “fixed” life in a linear timeline, adding his opinion of free will:

“If it is being a prisoner of the present transitioning from the past to the future, I have the illusion of free will. And I'm happy to live in that illusion in the knowledge that I don’t.” (13:15)

Watch the whole interview here:

3D printing might save your life one day. It's transforming medicine and health care.

What can 3D printing do for medicine? The "sky is the limit," says Northwell Health researcher Dr. Todd Goldstein.

Northwell Health
Sponsored by Northwell Health
  • Medical professionals are currently using 3D printers to create prosthetics and patient-specific organ models that doctors can use to prepare for surgery.
  • Eventually, scientists hope to print patient-specific organs that can be transplanted safely into the human body.
  • Northwell Health, New York State's largest health care provider, is pioneering 3D printing in medicine in three key ways.
Keep reading Show less
Big Think Edge
  • Push Past Negative Self-Talk: Give Yourself the Proper Fuel to Attack the World, with David Goggins, Former NAVY SealIf you've ever spent 5 minutes trying to meditate, you know something most people don't realize: that our minds are filled, much of the time, with negative nonsense. Messaging from TV, from the news, from advertising, and from difficult daily interactions pulls us mentally in every direction, insisting that we focus on or worry about this or that. To start from a place of strength and stability, you need to quiet your mind and gain control. For former NAVY Seal David Goggins, this begins with recognizing all the negative self-messaging and committing to quieting the mind. It continues with replacing the negative thoughts with positive ones.

Maps show how CNN lost America to Fox News

Is this proof of a dramatic shift?

Strange Maps
  • Map details dramatic shift from CNN to Fox News over 10-year period
  • Does it show the triumph of "fake news" — or, rather, its defeat?
  • A closer look at the map's legend allows for more complex analyses

Dramatic and misleading

Image: Reddit / SICResearch

The situation today: CNN pushed back to the edges of the country.

Over the course of no more than a decade, America has radically switched favorites when it comes to cable news networks. As this sequence of maps showing TMAs (Television Market Areas) suggests, CNN is out, Fox News is in.

The maps are certainly dramatic, but also a bit misleading. They nevertheless provide some insight into the state of journalism and the public's attitudes toward the press in the US.

Let's zoom in:

  • It's 2008, on the eve of the Obama Era. CNN (blue) dominates the cable news landscape across America. Fox News (red) is an upstart (°1996) with a few regional bastions in the South.
  • By 2010, Fox News has broken out of its southern heartland, colonizing markets in the Midwest and the Northwest — and even northern Maine and southern Alaska.
  • Two years later, Fox News has lost those two outliers, but has filled up in the middle: it now boasts two large, contiguous blocks in the southeast and northwest, almost touching.
  • In 2014, Fox News seems past its prime. The northwestern block has shrunk, the southeastern one has fragmented.
  • Energised by Trump's 2016 presidential campaign, Fox News is back with a vengeance. Not only have Maine and Alaska gone from entirely blue to entirely red, so has most of the rest of the U.S. Fox News has plugged the Nebraska Gap: it's no longer possible to walk from coast to coast across CNN territory.
  • By 2018, the fortunes from a decade earlier have almost reversed. Fox News rules the roost. CNN clings on to the Pacific Coast, New Mexico, Minnesota and parts of the Northeast — plus a smattering of metropolitan areas in the South and Midwest.

"Frightening map"

Image source: Reddit / SICResearch

This sequence of maps, showing America turning from blue to red, elicited strong reactions on the Reddit forum where it was published last week. For some, the takeover by Fox News illustrates the demise of all that's good and fair about news journalism. Among the comments?

  • "The end is near."
  • "The idiocracy grows."
  • "(It's) like a spreading disease."
  • "One of the more frightening maps I've seen."
For others, the maps are less about the rise of Fox News, and more about CNN's self-inflicted downward spiral:
  • "LOL that's what happens when you're fake news!"
  • "CNN went down the toilet on quality."
  • "A Minecraft YouTuber could beat CNN's numbers."
  • "CNN has become more like a high-school production of a news show."

Not a few find fault with both channels, even if not always to the same degree:

  • "That anybody considers either of those networks good news sources is troubling."
  • "Both leave you understanding less rather than more."
  • "This is what happens when you spout bullsh-- for two years straight. People find an alternative — even if it's just different bullsh--."
  • "CNN is sh-- but it's nowhere close to the outright bullsh-- and baseless propaganda Fox News spews."

"Old people learning to Google"

Image: Google Trends

CNN vs. Fox News search terms (200!-2018)

But what do the maps actually show? Created by SICResearch, they do show a huge evolution, but not of both cable news networks' audience size (i.e. Nielsen ratings). The dramatic shift is one in Google search trends. In other words, it shows how often people type in "CNN" or "Fox News" when surfing the web. And that does not necessarily reflect the relative popularity of both networks. As some commenters suggest:

  • "I can't remember the last time that I've searched for a news channel on Google. Is it really that difficult for people to type 'cnn.com'?"
  • "More than anything else, these maps show smart phone proliferation (among older people) more than anything else."
  • "This is a map of how old people and rural areas have learned to use Google in the last decade."
  • "This is basically a map of people who don't understand how the internet works, and it's no surprise that it leans conservative."

A visual image as strong as this map sequence looks designed to elicit a vehement response — and its lack of context offers viewers little new information to challenge their preconceptions. Like the news itself, cartography pretends to be objective, but always has an agenda of its own, even if just by the selection of its topics.

The trick is not to despair of maps (or news) but to get a good sense of the parameters that are in play. And, as is often the case (with both maps and news), what's left out is at least as significant as what's actually shown.

One important point: while Fox News is the sole major purveyor of news and opinion with a conservative/right-wing slant, CNN has more competition in the center/left part of the spectrum, notably from MSNBC.

Another: the average age of cable news viewers — whether they watch CNN or Fox News — is in the mid-60s. As a result of a shift in generational habits, TV viewing is down across the board. Younger people are more comfortable with a "cafeteria" approach to their news menu, selecting alternative and online sources for their information.

It should also be noted, however, that Fox News, according to Harvard's Nieman Lab, dominates Facebook when it comes to engagement among news outlets.

CNN, Fox and MSNBC

Image: Google Trends

CNN vs. Fox (without the 'News'; may include searches for actual foxes). See MSNBC (in yellow) for comparison

For the record, here are the Nielsen ratings for average daily viewer total for the three main cable news networks, for 2018 (compared to 2017):

  • Fox News: 1,425,000 (-5%)
  • MSNBC: 994,000 (+12%)
  • CNN: 706,000 (-9%)

And according to this recent overview, the top 50 of the most popular websites in the U.S. includes cnn.com in 28th place, and foxnews.com in... 27th place.

The top 5, in descending order, consists of google.com, youtube.com, facebook.com, amazon.com and yahoo.com — the latter being the highest-placed website in the News and Media category.
Keep reading Show less
Big Think Edge
  • Master Execution: How to Get from Point A to Point B in 7 Steps, with Rob Roy, Retired Navy SEALUsing the principles of SEAL training to forge better bosses, former Navy SEAL and founder of the Leadership Under Fire series Rob Roy, a self-described "Hammer", makes people's lives miserable in the hopes of teaching them how to be a tougher—and better—manager. "We offer something that you are not going to get from reading a book," says Roy. "Real leaders inspire, guide and give hope."Anybody can make a decision when everything is in their favor, but what happens in turbulent times? Roy teaches leaders, through intense experiences, that they can walk into any situation and come out ahead. In this lesson, he outlines seven SEAL-tested steps for executing any plan—even under extreme conditions or crisis situations.