Wormholes, Portals, and Time-Space Travel
Posted by Karl Withakay on February 1, 2013
I’d like to discuss what seems to me to be a fundamental problem with various forms of wormhole/ portal based travel in either space or time as represented in various forms of science fiction. It occurred to me some time ago, and in fact I started writing this post back in November 2012. I was reminded of it today while reflecting a little on the last five seasons of Fringe, which led to me thinking about The Observers and the way they can travel through time.
Science fiction frequently treats the Earth as if it was fixed in space relative to all other points and objects in space when we know this is not the case. Consider, if you will, Back to the Future when the DeLorean hits 88 mph and jumps through time to arrive in the exact same place on Earth, but at a different time.
The Earth rotates on its axis at a speed of about 465 m/s. In other words, if the Earth was otherwise fixed in space, after standing in place on the surface of the Earth for one second, you’d be about 465 meters from the point in space where you were the previous second.*
However, the Earth is not otherwise fixed in space. While it rotates about its axis, the Earth orbits the sun at roughly 30 km/s. So after that one second, you’d be about 30 km from your previous point in space regardless of whether the Earth was rotating on its axis or not.
But wait, there’s more. The sun and the entire solar system orbit the center of the Milky Way galaxy at around 220 km/s. This means that after one second, you would have traveled 220 km from the point in space you were at just one second prior, give or take 30 km depending on where the Earth was in its solar orbit and what direction it was traveling relative to the motion of the Solar System.
As the sun orbits the center of the Milky Way, the Milky Way is also not fixed in space. Our galaxy moves in and with an expanding universe, and is influenced in that motion by various factors, such as the gravitational pulls of the Great Attractor and the Shapley Supercluster. The Sun and Solar System move with a resultant velocity of about 370 km/s relative to the Cosmic Microwave Background radiation.
So by jumping just one second forwards or backwards in time and arriving in the exact same location in space, you would be several hundred kilometers from the surface of the Earth in space because the Earth, the Solar System, and The Milky Way are all in constant motion in a celestial ballet.
This problem would apply to most wormholes and portals in space (technically space-time) as well unless such portals were gravitationally bound to the locations of the endpoints so that they traveled through space with the planets/ locations of the entry points. The Stargate franchise gets around this problem nicely by making the wormholes connections generated between two gates rather than two regions of the fabric of space-time itself.
Back to the Delorean- after jumping through time to arrive in the same location in space, it would be stranded in the (near) vacuum of space and the drive doomed to death. (There’s no way to drive back.)
Interestingly, this brings up another interesting conundrum: What’s so significant about traveling at 88 mph (or any speed) relative to the surface of the Earth in the first place, and should it matter what direction you are driving relative to the motion(s) of the Earth? Velocity is relative to some reference frame and not absolute. The Delorean might be traveling at 88 mph relative to a bystander standing on the ground, but it would be traveling less than that relative to a tailwind and more than that relative to oncoming traffic, to say nothing about its velocity relative to something like the Moon or the Voyager 1 probe. That DeLorean in free space would be traveling at least 88 mph relative to something; what would or wouldn’t cause it to time travel? In fact, since there would be no air resistance or friction with the ground, it would likely still be traveling at 88 mph relative to the Earth** as its momentum carried on in space.
I don’t really have a good conclusion or summary here other than to say that traveling in time without also traveling in space may not be such a good idea. Sorry, Doc.
* Note that the net distance from the previous point will be less that the arc distance traveled, but the difference over the time interval used would be minimal. I’m also ignoring the motion of the Earth as a result of the Earth-Moon gravitational interactions as they co-orbit each other and other similar factors.
** I suppose things gets even trickier here. No longer being on the surface of the Earth, the Delorean would no longer be rotating with the Earth’s surface as it revolves about its axis, but would continue on a tangent from where the Earth was before the DeLorean hit 88 mph and jumped through time. This would be further complicated the change in gravitational forces exerted on the Delorean by the various actors due to their changed locations relative to the Delorean, which will be greater the further it has jumped in time. There are also other complicating factors involved here, but I think I’ve made my point.
Cordial Deconstruction 
Normand said
Interesting point you have Karl. But, assuming you are “building” a wormhole, it is built already having the same momentum you have, no? Like planes on Earth, no matter going to East or West, (except for air resistance, wind, etc.) it should take the same time to cover the same distance assuming the same speed (despite their speed is measured against the air), no?
If I am not mistaken, any build machine or contraption should be “fixed” to the references you have proposed. Then we have to consider the acceleration due to universe expansion. It could be a problem in big scales, but as far as I understood inside a galaxy the changes are none or quite small to be considered. What do you think?
Karl Withakay said
Well, on your first point, you are assuming the wormhole endpoints/portals are physical objects with mass and momentum (like black holes) rather than physical properties of localized regions of space-time (as in a rips in space-time). I basically covered that scenario with my “unless such portals were gravitationally bound to the locations of the endpoints” caveat, which basically implies the mass and momentum concept. For the purpose of my post, I was treating the endpoints as properties of localized regions of space-time itself rather than physical objects such as black holes. Your scenario is why, although I titled the post “Wormholes, Portals, and Time-Space Travel“, I mostly focused on the example of the time jumping Delorean from Back To the Future.
On the second point, I’m not an astrophysicist, but it seems to me that the distance scales are far less relevant than the time scales. With the caveat that it’s really difficult and bordering on meaningless to talk about distances of millions or billions of light years while referring to the same point in time, unless I’m mistaken (and that’s certainly possible) the expansion of the universe over human time scales, even over distances of billions of light years, isn’t very significant. The expansion of the universe is more significant over vast differences of time (millions, billions, & trillions of years). Also, I don’t think we’ve yet definitively established whether that rate of expansion is constant, or if the rate it itself is also increasing, but an accelerating expansion of the universe might be even more problematic for out stretching wormhole.*
This did cause me to think of another interesting concept. If we have a time portal from one point in time to another, do those endpoints travel in time with the local regions of space-time? In other words, is the portal a phenomenon that continues to exist such that one can visit it at any time and travel through it to a certain distance (say 1 billion years) in the past or future, or are the endpoints of the portal fixed in time such that they briefly flash in and out of existence? (ie: Are the endpoints fixed to precise moments in time, say Feb 8, 2013 CE at 10:00:00AM and Feb 8, 1,000,000,000 CE at 10:00:00AM?)
*Frankly, I don’t hold much hope for wormholes, they seem to create too many insurmountable physics problems. Place one portal an the surface of the Earth with the entry point facing up. Place the other portal some distance above the first with the entry/exit point facing downwards. (seal them in a cylinder without air to eliminate air resistance.) Drop an item into the first portal and let if fall forever between the portals as it accelerates due to gravity and approaches the speed of light and infinite kinetic energy.
Daedalus said
Interestingly, there was a Jimmy Olsen story of the 60’s where he climbed into a time machine, presumably one created by your friend and mine, Phineas T. Potter, and found himself drifting away from the Earth even as he traveled into the past.
Which, in the end, was only a device to get him to Krypton so he could meet the El family before the Big Bang, so to speak.
And according to dc.wikia, it’s #101 of Jimmy Olsen, Apr. 1967.
jaQ Andrews said
Old post, but…
I’ve always assumed, by way of rationalization if not actual science, that time travelers are constrained by the gravity well they inhabit. If one travels 6 months back in time, yes, Earth is on the opposite side of the Sun, but the time traveler is locked into position within Earth’s gravity field. I know just enough physics to understand that gravity can affect the passage of time, so this rationalization works well enough for me.
It’s also possible, since all motion is relative, that Earth is in fact stationary and every other celestial object is moving around us. That would make time travel possible only on Earth if one couldn’t compensate for motion in the first three dimensions.
Karl Withakay said
Interesting. Just a few quick thoughts in response:
First of all, the topic at hand is instantaneous portal/wormhole type time travel- traveling form one point in time and space to the same place in space in a different time using a shortcut in space-time. You’d be not so much traveling 6 months forward in time as you would be instantaneously moving between two points in time-space that were separated by 6 months. You would skip that 6 months entirely and not experience it at any kind of different rate. (We’re talking Back to the Future here and not The Time Machine) It shouldn’t matter if in the middle of that 6 months, the Earth is dismantled and the companents moved by galactic engineers to different ends of the solar system 1 week after you left and then returned and reassembled to what would have been its normal location 1 week before you arrived. Following your rationalization, if that did happen, you’d careen off into space since the gravitational pull of the Earth was absent form that part of space during part of the time between your departure and your arrival.
Lets’ say you travel in a ship orbiting the Earth to a point in time about 4.5 billion years in the past, before Theia impacted with the Proto-Earth destroying it and creating the Earth as we know it and its moon*. Would you emerge unharmed at the end of the trip? If you had been in orbit during the collision, you would have likely either been destroyed in the collision or flung off into space due the the gravitational interaction of the bodies involved. By your rationalization, shouldn’t something similar happen to you while time traveling “through” this event?
Is it just gravity that affects the time traveler? What about the other fundamental forces?
As to your second point, of course, the universe is not geocentirc, and the relative motion of the other bodies even in just our solar system make this quite clear. Frankly, the geocentric view breaks down really quickly. If you don’t look to hard, it sort of works for the sun, moon, and stars, but that’s about it. Before the Copernican model was accepted, astronomers had to contrive very complicated and elaborate behaviors to explain the paths of the Wanderers (planets) in the night sky.
These are just some quick thought, so they may not be as well constructed as the original post. 🙂
* Assuming the giant impact hypothesis is correct.
jaQ Andrews said
Found this while on a Wikipedia jaunt and again thought of this old post. It vaguely addresses your original point. I must confess that I found it somewhat past my bedtime and did not brain it thoroughly.
http://en.wikipedia.org/wiki/Time_travel#Time_travel_or_spacetime_travel