Ultimately, Time Travel is essential for Space Travel

Long-time readers may note that this blog bounces (veers?) between space-related content and time/temporal physics-related content.  Today, aside from admitting that (not surprisingly) the two topics are primary passions of mine, I’ll tell you why they’re related, and intimately so.

It’s all Einstein’s fault.

After an interstellar trip, a faulty suspended animation chamber reduces an astronaut to an ancient corpse. (From Planet of the Apes; Credit: 20th Century Fox)

Put very simply, according to Relativity: When dealing with events in the universe, it is impossible to separate the distance of space from the passage of time.

This is why astrophysicists and cosmologists speak of actions in the universe occurring and affecting “space-time.”  (Hence the “space-time continuum” that makes such a frequent appearance in sci-fi technobabble.)

What does this mean for us?  Well, in day-to-day experience, not much more than the odd reality that the moon we see is 1 second old.  Similarly, the sun we see is lagging 8 minutes behind us in time.

Why?  Well, it takes the light that bounces off of the surface of the Moon 1 second to cross the 230,000-mile distance between the Earth and Moon to strike the retina of your eye, and it takes 8 minutes for the light that leaves the sun to cross the 93-million mile orbital void to get to Earth and reach your eye.  As a result, we see the Moon and Sun as they appeared when the light left them, not when the light reaches us.

The same can be said of distant stars.  The farther away a star is, the older it is. (Even if it’s 200,000 light years away – then you’re seeing it the way it looked 200,000 years ago.)

So, quizzically, yes – this means that universe we see is actually a horrible garble of apparent objects from intermixed times.  Fortunately for us,  compared to the incredible speed of light, we’re close enough (distance) to everything we need to experience, (e.g., our limbs, food, loved ones, walls, etc.,) so that this time lag is unnoticeable.

But when we start peering out into the rest of the cosmos, this distortion really matters.  Many of the stars we’re studying may have already exploded… but if they exploded a few years ago, we won’t know it until light from the explosion reaches us, which could take millions of years if the star is far away.

Now, let’s take our time-distance thought exercises a step farther and ask what happens if we score the holy grail of the Search for Extraterrestrial Intelligence.  What if, for the sake of argument, we receive and translate a friendly message from an incredibly advanced race of aliens?  And what if, by fortuitous happenstance, they (hoping to aid other, younger life-forms) offer unlimited knowledge to any beings that can meet them on their world, face-to-face?  Well, the offer doesn’t do us more than a hill of beans of good if it takes us 200 years for a multi-generational craft to get there, only to find that the benevolent race has gone extinct due to a problem with their parent star.  We want to reach them as soon as we translate the message.

We want to separate the distance of space from the passage of time.

So, if we can conceptually and technologically conquer time travel, we will have in essence conquered space travel.  If one can manipulate the passage of time, then the time taken to cross the distance of space with any type of propulsion system becomes an almost trivial tally – little more significant than the miles-per-gallon of a modern automobile.

Conventional propulsion systems will get us around in space for the foreseeable future, and more exotic systems will likely take us to the nearest stars.  However, I believe it will be the mastery of time that will transform our race from provincial planet-hoppers to truly savvy, galaxy-trotting, cosmic-colonial game-changers.

Something to think about.

Hawking promotes forward-only Time Travel

Eminent physicist and cosmologist Dr. Stephen Hawking has recently come out to say that he no longer fears ridicule and endorses the possibility of time travel.  While this might seem like a revelation, his actual endorsement is not.  Let me explain.

Einstein’s Special Relativity has shown for nearly the last century that objects appear to move through time more slowly the faster they move through space.  This phenomenon has been measured, though the effect is so slight in everyday experience that physicists ignore it.  However, if astronauts were to travel in a spaceship very close to the speed of light, (a version of the Twin Paradox,) the effect would be very pronounced (see: Time Dilation), and our intrepid explorers would zoom forward in time – in a few years time spent away for the astronauts, the Earth and everyone on it will have aged centuries.

This is the only sort of time travel Dr. Hawking has come out to endorse – forward time travel as a result of moving quickly – which, as I mentioned above, has been a known effect for nearly a hundred years.  Backward time travel in Dr. Hawking’s view is still impossible because it would allow violations of causality, which bother him.  (Endorsing that kind of time travel would have truly been a revelation!)

So, nothing new here.  However, anything that gets the physics of Relativity and time travel into public media is okay in my book!

…and being that Dr. Hawking is so clever, maybe that was his intent all along.