Is there an explanation for the lightspeed-travel in FF4?

No. It wasn’t addressed.

Hey kid, it ain't that kind of movie

Fiction

As President Ross once said, "hey kid, it ain't that kind of movie."

As Harrison Ford once (allegedly) said:

“It ain’t that kind of movie.”

According to the movie’s dialogue, it’s FASTER than light speed. It’s not really important enough to the story to address


It’s a movie about superheroes brother

Reed probably tinkered with the engine for 20 minutes and made it not do that because science.


Reed did it.

I dunno why people are dismissing the question, marvel literally hired physicists for the time travel elements

I was watching F4 and noticed that one is made of rocks. How can he move if his joints aren't flexible and how does he digest food? Are the rocks packed tight enough that his "skin" is still waterproof, or does he leak through the cracks? Is there an actual explanation for why this isn't addressed?

Real talk though, it's sci-fi and doesn't follow real Physics. They didn't want to have to deal with time-dilation so they just ignored it.

Okay first off, based on what they show it’s an FTL drive of some kind. Since the physics of the real world don’t apply to that, time wouldn’t pass on Earth.

If you want to blow your mind even further, they use the FTL engine to get there, use it to escape and lure the Surfer to the neutron star and then use the star to slingshot the back to Earth which would not be an FTL trip thus making relativity apply. In the time it would have taken them to travel it sublight speeds from the neutron star to Earth, the Surfer would have already escaped and taken Galactus to Earth.

There are numerous things in superhero movies that defy the natural laws of the real world. You can either ignore them and enjoy the movies or you can let them ruin the movies for you. If I took the time, I could ruin every Marvel movie for you in that regard.

I actually liked this inclusion because it shows technology can evolve differently in different universes. And that progression does not have to be "linear." The whole world is analog, with records and knobs and such, yet they have FTL in this world. Maybe super unlikely, but I like these points about the progression of technology that it illustrates. 

Well technically if you move faster than light speed, doesn’t time reverse? You’re going faster than light so the light you’re reaching is what was reflected before what you can actually see. So by that logic, it’ll even out for the time that they’re in close proximity to the neutron star

The made sure to turn on the relativity regulators, naturally.

See also Star Trek’s Heisenberg compensators for making possible atomic teleportation.

Dozens and dozens MCU comic book movies and this is the nugget that made you go "Hey, wait a minute!"?

Nope, it wasn't addressed. Nothing related to science and physics was addressed in this movie, not even the stuff outside the scope of the team's knowledge

Science "Fiction"

They also had a device that teleports matter, an all in one baby monitor, a robot helper that runs on tapes, mole people, a stretchy guy, a rock guy, a guy who can self immolate and live, a woman who can go invisible, a baby who can raise the dead, a giant space deity that eats planets and makes space surfing beings made of silver but by all means, draw the line at their spaceship velocity. That's just not real enough! 

Reed is like the smartest person ever. If he wants his lightspeed engine to be faster than it'll be faster.

not even once did i wonder about it.

Don't they enter some sort of wormhole that allows them to fly Faster than Light? I can only imagine that's why they don't experience time dilation.

Invisibility, Fire, Rock and Steetching also weren't explained other than cosmic accident with radiation. Some things cant be explained in detail if you want the movie to have any pacing. Audiences are more likely to lose interest in an explanation (that will completely made up ) than they will just saying it goes FTL. That way you dont get pinned down with a specific mechanism for space travel. Unless its a plot point in said movie, which the way they travel waant here.


Kid, it ain't that kind of movie

Tony Stark made a palm sized nuclear reactor which is impossible to be made due to the minimum critical mass required to initiate a reaction. Peter Parker created a fluid that solidifies into a material with absurdly high tensile strength which is also physically impossible. Science in the MCU is fictional and has loopholes to make some stuff happen that cannot be explained in the real world.

There's a rockman driving a flying car. And you're worried about FTL?

Time works in scifi film how director want it to work. i hope this is relevent.