Why Traveling to Alternate Dimensions Would Be a Disaster
Traveling to alternate dimensions and alternate worlds is a staple of science fiction. It allows us to ask, “What if?” and then show what might have been. Why is traveling to alternate dimensions a disaster, no matter the scenario?
Let’s look at the dangers in every possible scenario of interdimensional travel between different alternate timelines.
You Travel to an Alternate Universe Where You Exist
If you travel to an alternate universe where you already exist, you’ll create trouble for yourself if somewhere on the planet where you fail to follow the rules of your society, aren’t where your in-universe counterpart is supposed to be or simply fail the test of you being you when you meet others who think they know you. It could be as mundane as talking to a pretty girl and others think the alternate version of you is cheating. It could be as dangerous as you appearing somewhere highly restricted or violating local laws, returning home when trouble appears, and now the in-universe you gets the blame and lacks your escape mechanism.
There are many multi-verse based stories where someone travels to another timeline / universe and meet up with a different version of themselves. The dimensional travel would be pretty bad in most cases. The other person thinking they are hallucinating is one possibility, while meeting them while really drunk or drugged would be the least difficult one to deal with.
Meeting another version of you when you’re both arrested for one or the other’s crimes creates a mess for both of you, and the in-universe you lacks the escape mechanism you do. And if you vanish from the police station, the in-universe you will still face a lifetime of scrutiny - if not dissected - in the hope of learning about dimensional travel or unraveling their conspiracy theories about how two of you existed. You just ruined the life of your double, if not killed them, by sharing their world for a while.
And all of these cases don't include the possibility of a conservation of mass model where you going to another universe pulls your alternate into your universe, so you risk coming home to find out your double made a mess of your life.
You Travel to an Alternate Universe Where You Used to Exist
You’ve appeared in a timeline / alternate universe where you used to exist. If you died as a baby, you’re at risk of allegations of identity theft. If you died as an adult, you still risk charges of identity theft unless they charge you with faking your own death instead. I hope you didn’t disappear under suspicious circumstances, and now those who killed that timeline’s version of you want to kill you instead.
Assuming you stay out of legal trouble, the horrors for those you meet who attended your funeral are rarely part of the story.
An Alternate Universe Where You’ve Never Existed but Is Similar to Ours
Papers, please! You have no papers or identity cards or implanted chips or whatever to prove you are you in most alternate timelines. Land in a fascist society, and you risk being killed for carrying ID for our world. Show up without papers in less severe papers, and you still risk being killed. If you don’t have identification in some nations, you risk being jailed as an illegal immigrant or killed as a suspected spy. Land in the middle of a war ignorant of the history and politics, and you have no idea what to say to not get killed. And telling the truth looks like a really bad lie or you’re crazy. I hope this alternate dimension doesn’t kill the insane, but you might wish you were dead after their version of a lobotomy.
If you show up in a similar but different world, the more likely possibility is being labeled crazy and locked up a la “12 Monkeys”. Then you risk a fate worse than death, because there is no family to claim you or friends to argue your case. You are utterly alone, unless you can go home. And if you get home, the explanation of where you’ve been can get you locked up in the psych ward here.
Another possible threat is that you’ve traveled to an alternate timeline that is different because some plague swept through the population and killed a few of your ancestors. Now you’re at risk of diseases they don’t consider problematic because they’re resistant, and since you’re not descended form the survivors, you are not.
You Travel to a Very Different Universe/Timeline Populated by People
You’ve stepped into an alternate reality very different than our own. One of the biggest mistakes these movies assume is that everyone speaks English. Go back and read Shakespeare without the Cliff Notes. Travel very far from your timeline / universe, and even English is difficult to manage. And that’s assuming you don’t land in a North America where Columbus didn’t get his funding and everyone speaks Amerind languages a couple centuries diverged from our world’s languages. Or the Vikings came over in mass a thousand years ago or some other major demographic shift that equally alters the languages.
In any such a scenario, even having a universal translator that uses all of our languages won’t work for their very different languages. After all, language is the result of historical interactions between cultures, and this scenario already gives them a very different history.
Accidentally violating a local taboo, which is very likely since you don’t know the customs, risks your life. The more exotic the world, the more likely such a disaster occurs.
Stepping into a timeline very different from ours also introduces the dangers time travel does. Diseases are constantly mutating, and you’re outnumbered trillions to one. Assuming you don’t die on inhaling the air instantly, unfiltered water, soil bacteria and so forth are all very dangerous. Do you want to make contact with these people? About 90% of the Native Americans and Aborigines were wiped out by contact with European diseases that were childhood illnesses for the latter. And that’s assuming that the bacteria you carry don’t start a pandemic with them. Dogs smell you in part due to the unique cloud of bacteria around you. There are the fungi and bacteria that live on your skin, often bacteria in the nasal passages, the viruses that don’t bother you but will kill others.
It doesn’t even have to be a serious disease to pose a threat to you. Bubble Boy David Phillip Vetter died when he received a bone marrow transplant with his sister that contained the dormant Epstein-Barr virus. And now you’re stepping into a world without their genes for disease resistance to the native diseases, and your immune system will be overwhelmed by trying to fight everything at once when it is exposed. Simply dealing with twenty minor but brand new infections is enough to kill you.
Let’s look at some of the more mundane problems of appearing in a timeline/universe where you neither allies nor a means of communication. At best, you’re fodder for enslavement, assuming you don’t die of some dangerous plant or condition you can’t understand. At worst, you’re assumed to be magical, killed for your stuff and consumed, as even some African groups practice today. Then there’s the more likely standard human act of killing you because you are obviously a foreign invader / intruder or for your stuff.
The Alternate Dimension Has Very Different Life Forms
Without a spacesuit, landing on a world where oxygen producing life didn’t evolve will kill you. The carbon reducing atmosphere is more akin to Venus than Earth’s today. You risk a nearly as bad scenario if oxygen producing plants are present but not as successful; gradual suffocation gives you time to think about it. Or life took a different biochemical route during evolution, and everything is now poisonous. Then there’s the more mundane situation of landing on a world where mega-fauna now rule because humans didn’t arise, so whether chased by dire wolves or dinosaurs, you’re still something’s dinner.
The Danger of Traveling Where Earth’s Very History Differs
Jump to another dimension with a different geologic history, and you end up falling from 500 feet into the air to the ground or ocean instead of stepping out onto land.
Travel to a dimension where a comet or other body interacted with Earth’s orbit incrementally differently, and you end up in a timeline where the planet is several thousand miles in another dimension. Now you’re teleporting into space or rock, take your pick.
You’re equally dead if you land in one where Earth didn’t develop an atmosphere or lost it. Landing on an alternate Earth before it was hit by the Mars-sized body that created the Moon means you land on a smaller world with a radically different topology. Smaller and nearly all water, at best you’ll see it from a moderate height before landing in the shallow seas. At worse, you’ll view it from space while choking on the vacuum.