This is a nice bit of work a friend of mine found and shared.  It’s clever and even has some funny woven into it 🙂

Traversable Achronal Retrograde Domains In Spacetime

My only issue with any discussion of time-travel though involves space.  Not exactly “Space” as we see it looking up at the sky, but space as in, “Hey look there’s a giant boulder in front of me that’s taking up space”.  But actual Space is part of this frustration as well.  I’ll explain why.

In books, movies, even serious discussion of time-travel, every one has a time-traveller disappearing as the traveller starts to travel and then re-appears in the “real world” as time travel stops.

Ok, let’s roll with this idea, and hold that thought.  We’ll use this later on.

Now, if someone travels through time “for just an instant” and comes back, we are shown/told that the person re-appears in the same spot he or she started.

Ok.

And if someone travels for a longer bit of time, he or she may collide upon “re-entry” if something is in the same spot he or she started.  Like if a dog or chair happened to be moved into the traveller’s starting point.  Makes sense if you look at it this way.

Here’s where “Space” and “space” come into play and messes with my head, and temporarily eclipses all the fun in the fiction and discussion.

We’ll focus our attention to what the “disappearing time traveller” means.

Let’s use a specific example.

 

Sally has just used a time-travel device to go back 30 years in time.  She’s a fan of 1980s music and just wants to have fun.

Her friend Bob will wait around for her to return, because he’s not as big a fan of the 80s as is she.  Also he doesn’t like fun, as he’s a grumpy bear.

According to pop culture concept of time-travel, she disappears from Bob’s view.  The assumption is that she’s gone back 30 years to the past, in the same spot she and Bob are located.

Sally walks around for a week or so, admiring the headbands and spiky hair, visits a salon to have her hair style upgraded to the Big Hair look, goes back to the spot where she’d appeared, and uses the time-travel device again to go back to her frowny friend Bob.

From Bob’s perspective, she returns a few moments after disappearing with a new hair style.

They’d been very careful to not return her back immediately or overlapping her departure.  Legend has it that if time-travel entities meet, the world will end or something.  Anyway, they choose to not take this chance.

It’s easy to understand (and visualise) that if something is placed in the location where the person used to be, and the person “comes back” from time-travelling, he or she would collide with that object. Or become merged with it, ala The Fly (hellllppp meeee).

Same logic applies (in this example) to objects that “used to exist” in the spot where the time-traveller going to the past might encounter.

Like if a building used to be at the spot where Sally and Bob are standing, and she were to travel back in time, she’d collide with the building and generally make a mess of things.

These are easy enough concepts to grasp. That’s why pop culture uses these memes.

Now.  Here comes the part that hurts my head and bothers me that no one’s addressed it in pop culture time travel.

Focus on the disappearing act.

Sally “disappeared”.

She “has left the building”, as one might have said a long time ago.

Where did she go?

To the past!  Right.  I got that part.

But I mean physically, where did she go?

She has left our current plane of existence.  Let’s say, for argument’s sake, her physical body moved into another “dimension” during the travelling process.  Which makes her invisible to the viewer or anyone not moving along with her.  And not just “invisible” but incorporeal with regards to our world.

She has left our plane of existence.

Which allows her to move backwards/forwards in time.

But…

…and this is a BIG BUT…

…this also means our plane of existence can move (forwards in time, naturally) in any physical direction it has been moving, without bringing her along with it.

Look at your feet.  I assume you aren’t walking whilst reading this.

Pretty firmly planted on the ground, eh?  Unless you’re listening to music, too , and tapping your feet.

But generally speaking, you aren’t moving much.

Ah but you are placed on the Earth.  Which is rotating.  And if you’re at the Equator, you are moving as fast as 1,070 miles per hour, according to NASA.

That’s just the Earth’s rotation.

The Earth’s speed as it moves around the Sun is about 66,000 miles per hour, according to Universe Today.  Oh, and how quickly is the Solar System and our Galaxy scooting along?  Best to check with Astrosociety.org.

So even when we think we’re sitting still, we’re moving, spinning, rotating.  No wonder some of us are dizzy at times.  me more than most, I suspect.

 

But let’s get back to Sally.

She’s jumped out of our plane of existence.  She was moving along just like Bob was, following along in the astral roller-coaster ride we all are on.  But then she left the ride to travel through time.

Let’s assume (big assumption) that she follows Newton’s 1st Law of Motion.  That she’ll continue to move at her current speed unless an object acts on her – stopping, slowing her down, or speeding her up.

She’s become a drifter, moving very very very quickly in a single direction.

Blame The Vector Principles on this.  But don’t blame the sunshine, moonlight, good times, or even The Boogie.  It’s The Vector Principles this time.

Our physical world can’t touch her.  The floor can’t hold her.

The Earth can’t guide her and very very very quickly, rotates and eventually moves away as it continues its orbit around the Sun.

The Sun, in turn, moves along in its path in the Solar System and scoots out of Sally’s view.

So when she turns off her time-travel machine, she’ll be very surprised to find herself drifting in Space.  It’ll have been 30 years in the past, but physically, she’s a long way from home.

 

And this is why I can’t really enjoy time-travel movies.  It’s that durn Vulcan logic ticking away that butchers Bill & Ted movies.

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Photo credits

http://www.flickr.com/photos/whatleydude/8318380582/

http://www.flickr.com/photos/25477528@N00/5181143856/

http://www.flickr.com/photos/ethanhein/2242736982

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