Copyright � 2026 by Shane
Tourtellotte
There is not one kind of time machine, any more than there is one kind of automobile. While possessing the same basic functions, they have a wide array of sizes and capabilities that mimics the range between sub-compacts and eighteen-wheelers. How you handle your machine depends on where it falls on the spectrum.
If you already have your time machine, you’ve already made the decisions about what you can do with it, maybe without realizing it. This section will bring those capacities and restrictions into focus. If you haven’t yet built your time machine, these pages are definitely for you. You can decide now what the best option is within your limits: of resources, of patience in getting the thing built and starting your adventures, and of risk acceptance.
The types of time machines can be broken down along two axes. The first axis is the mobility of the machine: whether it is fixed in place when not traveling through time, or whether it can move itself, or even be carried by the time-traveler. The second axis is mobility in transit: whether the machine moves through time alone, or can relocate itself in space as well as time.
The type most people would want is obvious: something that could zip you halfway around the world as well as two thousand years back, that you could carry in your pocket safe from accidental discovery. Good luck building such a thing. Even in a field that makes flights of fancy come true, there are practical limits to be confronted, and trade-offs to be made.
Size may be inconvenient for mobility, but it also allows you to stretch your capabilities and reduce your risks. You can carry more power to run the machine. You can bring more cargo to the time you’re visiting, from trade goods to first aid supplies to replacement parts for the machine. (Likewise, you can carry more cargo from the time you’re visiting.) You can use components that are less miniaturized so you aren’t compromising on precision with how far you travel, how well the inertial anchor functions, or how sensitive the wormhole generator is to the boundaries of what it’s conveying.
Being able to sideslip through time and space simultaneously is obviously convenient and useful for a time-traveler. It also multiplies the work the machine needs to do, meaning it probably needs to be bigger to do that work. Again, miniaturization compromises precision and requires even more stringent tolerances, meaning building it to specs will take longer and be costlier, and your trip will be riskier.
The two axes mentioned before produce six main types of time machine -- so my review will naturally start with the seventh.
Designation: WABAC Series
Capabilities: Stationary unit; sends objects through time and space but does not itself travel through time.
This type of time machine can almost be termed a time projector: it sends things through time and space without moving itself at all. It allows a brute force approach to the technical problems: you can build as large as you need for equipment and power, and it can send large masses and volumes if desired. Despite being primitive in ways, it is a surprisingly viable choice for a model of time machine.
The main problem with this series is its inflexibility in permitting follow-up travel. You cannot skip ahead or back from when you are, nor shift your position, however useful this could be to you. You’re limited to returning to the timeframe where you started, doing so from the place where you arrived in your destination timeframe. That’s where the wormhole is, and that’s all it’ll be capable of doing when you use it again.
You need the wormhole to be there, and accessible, to make the return journey. Generally, this means the wormhole will remain where it appeared, held open by the machine in your original timeframe. It won’t be gaping open, of course, where anybody can happen upon it, peek in curiously, and blunder through. It will be shrunk down to microscopic size, preferably on the atomic scale or even smaller. Larger than that, and the merely microscopic wormhole could carve a path through the body of somebody walking into it. This is bad both for the perforated innocent and for the cleanliness of your machine’s projection stage: tiny strings of meat are messy beyond their size.
You, the intended passenger, will need something to open the wormhole back to proper size when you want to return. Generally, this is a pod that emits a particular EM frequency when activated. Sensors on the machine’s side of the wormhole detect the signal and enlarge the wormhole for transit. Of course, to get through an atomic-scale wormhole for detection, the emission needs to be extremely short wavelength, on the order of hard X-rays or gamma rays. Hopefully your pod is well shielded1.
If you’re chary about lightly irradiating yourself, it is also possible to program the machine to re-create the wormhole at a set time, or even series of times, to permit your return. This allows the wormhole to be closed, removing the nuisance of people or animals possibly walking into it. One trade-off here is the threat of inconvenient witnesses when it re-opens, which an opening at your immediate command would avoid. This can be mitigated by having the opening occur in the dead of local night, but it still leaves some risk.
The WABAC Series is perhaps not so simple that a highly intelligent dog can operate it, but it is a practical option for time travel, if you have the resources and space to build something that large. For the more constrained, there are other options, and arguably better ones.
Designation: Wells Series
Capabilities: Non-mobile unit; travels through time only.
This is the classic concept, the Model T of time machines. It is the easiest technically to produce and provides the core functionality, but it is limited. It’s the likeliest type for the shoestring time-traveler to make, which by simple probability means it’s your likeliest type.
Its limitations are clear. If, for example, you want to witness the signing of the Declaration of Independence, you need to build the machine in or near Philadelphia, or transport it to that area before making your jaunt. Once at your destination, concealment of the machine will be burdensome and probably not very reliable. Try to acquire maps of the area drawn up in that time, and hope they are accurate -- if you’re visiting the past. If the future is your destination, you won’t have this option, unless you or someone else has done some advance scouting.
Even so, this model is arguably a better option for visiting the future than the past. Motivation for seeing the future is usually general rather than specific. You aren’t going forward to witness the world-shaking assassinations of 2085, or the parade for the first astronauts to return from Mars, or even that awesome World Cup final in 2046. You’re going to the future to see the future, to discover the broad expanse of what the coming centuries hold. You don’t need to go to an exact place for that: someplace is enough.
Contrariwise, one’s interest in the past is much likelier to be specific than general. Wandering through London of 1595 has its appeal, but odds are you have a destination in mind. If you aren’t hovering around palaces trying to get a glimpse at Elizabeth, you’re probably taking in a play at the Globe -- or maybe a competing establishment, to see if the Bard’s colleagues might deserve better than to stand forever in his shadow.
This isn’t hard and fast. You might be content to visit ancient Rome for the general ambiance, or you might aim for historical events of the future once you’ve visited the further future and found out what those historical events were/will be. In the main, though, the Wells series is a better fit with visiting the generalized future, which meshes nicely with how H.G. Wells used it in his famed novel2.
For more than an economy-class trip, you have other options.
Designation: Rufus Series
Capabilities: Non-mobile unit; travels in time and space.
This series provides a leap in capability from the Wells type, in a framework which likely can support the size and power demands it makes. For the time-traveler with more time and patience, and greater resources, it is a very sound choice.
Having combined time-space mobility does more than expand the places you can visit. If the machine is precise enough, and you have enough dependable information on how your destination was laid out in the time you’re visiting, you can arrive at a well-concealed location. With this starting advantage and the right camouflage options, your machine should be pretty safe from discovery.
A word about that camouflage, though I will have more to say later in the handbook. Before your trip, you can dress up the time machine as something that might pass casual notice in your destination time. A big rock or a cairn, a large bush or tree trunk, and many other things could work well in the right place. (This also holds for the Wells series.) This is best combined with precise knowledge of the area, but can still be at least slightly helpful as a general precaution. Artificial items are much less practical hiding options, except maybe in cluttered urban settings. Human-made stuff is too likely to draw direct human interest. I cannot imagine Who could think otherwise.
If you aren’t fortunate enough to hit the right hiding spot directly, there is a workaround. A second, short hop in your time machine can move you spatially to the ideal place. Accuracy should not be an issue for an abbreviated hop, but energy consumption will be: a short trip doesn’t use that much less energy than a long one. Watch the fuel gauge.
The primary advantage to this series remains being able to leap across continents as well as eras. The advantages are clear enough that I won’t rhapsodize about them here: consider them praised.
Excellent as this option is, there’s another one that’s pretty electrifying.
Designation: Brown-McFly Series
Capabilities: Mobile unit; travels through time only.
Never underestimate the power of an ad campaign brilliantly disguised as a summer blockbuster. This is the dominant design people now have in mind when they imagine owning a time machine. Fortunately, they haven’t been sold a lemon. This is a very capable model, depending on circumstances the best type you can have.
The leading feature is obviously its mobility. The machine is much easier to move to the spatial coordinates of your destination when the distance is drivable, and will excite less curiosity and suspicion if you need to ship it from, say, California to Japan. Mobility also makes for better secrecy in your destination time, as it can move itself to a good hiding location. Its utility for moving you around in that time, however, is limited to a narrow band before and after your home time. Any time before the 20th century will make it obviously anachronistic, and too much beyond the present day it will be rendered an eye-catching, rumor-starting antique3.
Real life will even do the movie concept one better. Your machine will have plenty of abstruse equipment, but no flux capacitor. You will not need to build up dangerous speeds in order to generate the wormhole that moves you through time. A bit of motion will help you traverse the wormhole once it’s generated ahead of your vehicle, but it won’t need anything past safe neighborhood speeds. This isn’t cinematic, but it’s much safer, not only for you but for anyone who might be right in front of you when you pop into their timeframe.
The size of the machine will still be enough to accommodate all the needed equipment, as well as its power requirements. Carrying capacity should be adequate for extra energy storage, spare mechanism parts, and a generous allowance of cargo. Just be sure to have adequate security, and to take the keys with you. When it comes to someone breaking into your mobile time machine, Gone In Sixty Seconds takes on brand new meaning.
Designation: Epoch Series
Capabilities: Mobile unit; travels through time and space
This is the obvious next step for a mobile time machine: something that can move itself while transiting time as well as within a single timeframe. It’s great in theory, but the conversion to practice is harder than it looks.
Accurate time-space displacement requires knowing just when/where you are and just when/where you’re going. That’s doable with a mobile time machine in the modern era because of modern supporting technology. Try to call up GPS during the Napoleonic Wars, and zut alors, you won’t get far.
If you can return to your point of arrival for the return trip, that helps a lot, but it’s no certainty. You may wind up dependent on dead reckoning by the machine itself for precise positioning. That can work, but it will need extra equipment, drawing extra power. Other things will get crowded out. You’ll have to prioritize more, make harder choices, do with less.
Take this as a restraint, though, not a bar. If you’ve managed to build a time machine, odds are you’re pretty capable and resourceful. Apply that to this problem, with a clear eye about what’s necessary, and you’ll find a way through, even if it’s not everything you wanted it to be.
Get yourself home safe. That’s your first priority. Otherwise, how do you expect to brag about everything you’ve seen and done?
Designation: Eakins Series
Capabilities: Portable unit; travels through time only.
Big, cool-looking time machines have their appeal, especially on the silver screen. The more cautious time-traveler may prefer something that doesn’t stick out so much that the locals can’t help but notice that something is out of the ordinary. A time-travel device that you can carry, even conceal, on your own person takes some of the risk out of the enterprise. You have to balance this, however, against the risk that it adds.
A mechanism as complex as a time machine requires a certain minimum size to function. A hand-portable machine can provide this, but with little room to spare and not much room at all for extended functionality. You’ll get there and you’ll get back, if it’s not too long a leap through time. Maybe internal power will suffice, but more likely you’ll need fast-discharge batteries. Precision may suffer with miniaturization and loss of redundancy. You could miss your target time by hours or even days, and you might also want to set your re-emergence a couple feet higher to mitigate risks of misplacement. If you go up a size or two to a belt or backpack machine, you’ll get some more wiggle room, but for options it will still be a plodding walk compared to driving a luxury car.
This may be all right. You don’t need a luxury car for every trip. Simple machines can work for simple itineraries, and some added riskiness in the travel may be acceptable to you4. If you’re aware of the compromises brought by portable size, if you judge the benefits to be greater, that is enough. If you put enough effort into recognizing and examining the questions, there is no “wrong” answer.
Okay, perhaps there is one wrong answer.
Designation: Boggs Series
Capabilities: Portable unit; travels through time and space.
This is the ultimate. Easy to carry; able to send you to any place and any time; accurate, reliable, and durable. It is the Holy Grail of time machines.
That last description encapsulates how difficult it would be to obtain one.
A small time machine with unlimited capabilities may skate by in less demanding fiction, but in reality it’s a pipe dream5. Limited size forces miniaturization of components, reducing precision in movement through time and especially space. Energy requirements mean the device basically cannot travel on its own: you won’t so much plug a battery into the machine for each jump as plug the machine into a battery large enough to power the trip. Bringing enough of those batteries for anything beyond a simple there-and-back will drastically reduce the concept of portability attached to the enterprise.
As I’ve emphasized before, there are always trade-offs, even with sophisticated technology. If you’re limiting your time machine’s size, it will come with limited functionality, or limited reliability of those functions, or both. In most practical cases, a portable time machine means moving in time only, not space. Accepting the limitations, working with them or around them, is your best course.
Should you come into possession of a Boggs Series machine, something with every advantage, be careful. Anything that capable in that size probably comes from a technological base well in advance of ours. In short, it belonged to some far-future time-traveler. That person will probably insist on getting it back -- or have friends, or bosses, who insist on getting it back. Imagine how likely you’d be to fend off a four-dimensional SWAT raid, and plan accordingly. Offering it back for a moderate reward might be your base-case scenario, even if you do look silly putting that in the want ads or posting those flyers around your neighborhood.
Footnotes:
You might also consider hiding the emitter close to the wormhole’s location, so you’re not taking doses from the stray radiation it produces while idling. This is viable in fortunate circumstances, but do not push your luck in separating yourself from your only way back to the present day. One curious person or nosy animal, one heavy boot or hoof or wagon wheel, and you are in big trouble.
He was weaving an “if this goes on” tale rather than slaking his curiosity, but writers are allowed such leeway.
It even may, depending on distance in the future and local laws, be illegal to operate such a vehicle. Support or oppose pending legislation as applicable.
If you want to keep safe at all costs, you could just stay home. Here I could catalog all the risks of ordinary life, but there’s no sense in making you more of a worrywart than you may already be.
I decline to comment on what is in the pipe to be giving you such dreams.
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