Warning: SPOILERS for Fantastic Four #4
The Fantastic Four have finally pointed out a major plot hole when it comes to time travel in the Marvel Universe - and they've solved it with a tragic scenario. Reed Richards may be one of the smartest men on Earth, but he is far from the most compassionate, and his actions prove time and time again that what he believes is best isn't always the case. His latest "solution" to a world-ending problem solves a time-travel conundrum in the worst possible way.
Fantastic Four #4, written by Ryan North with art by Iban Coello, begins with a flashback sequence to an alien invasion of Manhattan, with the epicenter being the Baxter Building. The aliens have resisted nearly all of Reed Richards' plans so far, so he quickly improvises a dangerous solution: send the entire Baxter Building forward in time one year. This gets rid of the aliens by throwing all of them into space, far outside Earth's solar system, while everyone else inside the building remains safe; they'll return in one year's time.
Reed Richards Knows Every Time Machine Is Also A Space Machine
Reed is able to accomplish this through a little-known (and rarely commented on) phenomenon concerning time travel. Most time machines in science fiction (the Marvel Universe included) deliver the traveler to the exact spot where they left - but those machines must also account for the movement of the Earth, and the solar system through space. Reed's dialogue implies this, and for the first time, Marvel acknowledges that time travel must also teleport the traveler through space as well as time.
Unfortunately, Reed's method to winning the day can easily be constituted as overkill in this situation. In an invasion scenario where only the aliens needed to be taken care of, Richards decided to move everyone in the building - his children included - forward in time one year. While this tactic ostensibly saves the Earth, it devastates families of those in the building, who must now cope without their loved ones for a year (or longer, if Reed's calculations are incorrect). The Fantastic Four's leader, once again, fails to understand people.
There are plenty of time travelers in the Marvel Universe (Cable, Kang, and even Doctor Doom on more than a few occasions), and they all have teleporters along with the power of time travel. Accounting for the movement of the Earth, Reed Richards successfully fended off an alien invasion, but perhaps irreparably damaged the standing of his team in Manhattan for the foreseeable future. The Fantastic Four's leader perhaps wishes he had sent himself back in time to warn himself of the fateful decisions he would soon make.