Does space travel work, like how it does in sci-fi movies?

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Oh okay. So when scientists say that if you were to go to Mars it would take seven months, is that just seven months for the astronauts that are traveling there, and it will take more time to get there for people on Earth since time is different?

Dude...you gotta do some studying on your own. Learn the basics please.

There is interplanetary space, and then there is interstellar space, and then there is intergalactic space. Each of those three is unimaginably dwarfed by the next type of space.

Forget about intergalactic for now.

We already send unmanned probes to Mars, and its not impossible that some nation may land humans on Mars in your lifetime. But Mars is in interplanetary space. So we can send stuff there using the same rockets that got us to the moon that only travel at a few tens of thousands of miles per hour. Far less than light speed. Because they are far less than light speed Einstein's time dilation doesn't effect it ( there is a slight effect that does have to be taken into account in the technology, but its doesn't effect humans much because it microscopically small).

So if your movie is about going to Mars then "seven months to Mars" means seven months for both astronauts and for the folks back on earth. No need to worry about Einstein, and his time dilation effects.

But if your space ship goes beyond mars, beyond Pluto, and leaves the solar system, and visits the nearest Star (alpha centauri), and whatever planets that that star may have...then it has to traverse a distance of four light years.

The distance from the sun to earth is eight "light minutes", to Mars "twelve light minutes", to Pluto about five or six "light hours". The nearest star is four light years. A whole bigger of order of magnitude. Get it?

Even the nearest star is zillions of times farther away than the farthest planet in our own solar system. So with even the closet destinations in interstellar space you get Hollywood needing near light speed, or light speed, or more than light speed, travel for the characters to get around. And its at big fractions of light speed that you would get a time dilation effects of Einstein.

So if your characters are just going to mars you don't need to worry about time dilation. But you do worry about that for Mathew Mcconnehy in a movie if its title is "Interstellar" (and they do factor that it into it in that movie).

Except Hollywood doesn't worry about time dilation(nor much of anything else in real science) in either Star Wars or Star Trek (both of which take place in interstellar space) because...its Hollywood.

https://scaleofuniverse.com/                              o

And even in THE EXPANSE, humans are limited to small fractions of the speed of light, even with the capability to accelerate for half the journey (usually at about 1/3g or around 3.2667m/s/s) because they're not accelerating long enough or hard enough to attain even a decent fraction of light speed.

In THE EXPANSE, they use the Ring Network to get around the problem of the vast distances between stars - kick around our solar system at non-relativistic speeds, go through the rings and then kick around the remote solar system at non-relativistic speeds, ignoring the vast interstellar distances in between by virtue of the wormholes (rings) joining the systems.

THE EXPANSE generally does a pretty good job of addressing the amount of time it takes to get around the solar system, including having communications lag due to the number of minutes for a radio signal to get from, say, Earth to Mars and for a reply to get back.

In Babylon 5, they used "jump" gates/points and "hyperspace" to avoid travelling anywhere near light speed - and even used "hyperspace relays" to allow radio transmissions (limited to the speed of light) to get between star systems at "conversation speeds" - they didn't always apply the physics evenly and there were none of the light-delay lags that one would expect for radio transmissions between star systems that are "days/weeks apart" when travelling through hyperspace at non-relativistic speeds... surely even light/radio would take several minutes to cross that sort of distance and there should certainly be a communications lag between the local jump point (out beyond Jupiter's orbit IIRC) and Earth. They didn't even have delays communicating between Earth and Mars.

So basically "short cuts" to bypass the inconveniently huge swaths of space between here and where the action is.

In Star Trek they "warp space" but that's applied so inconsistently, it's a total joke. They run around in "warp" mode and barely get from one side of the planet to another at one moment and then travel fantastic distances between stars the next. (basically, they move at the speed of plot)

They use "warping space" to hand-wave away any relativistic effects as they say the "ship" is not approaching/exceeding light speed because it's in a "bubble" of space that's being "warped" from one place to another and relative to that bubble of space, the ship is not actually moving... at least, that's my understanding of Star Trek technobabble/handwaving, and I'm sure it's been contradicted at least once in the course of the many series.

Basically, the only way to have a series/movie set in an interstellar setting, is to find some way to work around or completely ignore relativity and/or light speed.

So ... to answer OP's original question: In movies time travel works - in real life scientists haven't got it worked out and some people think they never will. In movies someone can be frozen and kind of go into hibernation to "wait but not grow old" to allow for a very long trip between stars, but in real life no-one has ever been able to get the freezing trick to work.
In real life and in movies traveling through space really does change how time flows, but the rules they use in the movies are not the rules real scientists use (at least in most movies). If you COULD "wait but not grow old" because of freezing - like Captain America - that would be kind of like time travel, but only forward and never backward. You would need some other kind of explanation in your movie for "going back" (which I think they did in the second Thanos movie). In real life going forwards in time by waiting (without the freezing) works - like the message and the DeLorian that Doc Brown sent to Marty in Back to the Future (second or third movie - forget which) but going backwards does not (but there are some real scientific theories based on certain math related to Einstein's equations that say it might work - but no experimental evidence showing that it DOES work).
The different between going forwards in time and never backwards - and the related concept of "entropy" - are sometimes called "Time's Arrow" - since, like a "one way" sign, it always points in the same direction.

Off topic - It is in both BTTF II (ending scene) and III (beginning scene). Marty is approached by a Western Union courier with a telegram from the Wild West era during a downpour in 1955. The DeLoren was stored in a cave for 70 years when Marty found it (in 1955) at the beginning of BTTF III.

I am a big BTTF fan and have a signed copy (Doc and Biff) of the trilogy set. I have personally met both actors. They were at a Comic Con that I attended a few years ago.

Please resume the regularly scheduled topic.

Thanks, QuantumChemist - I kind of remember it like that but couldn't quite recall and didn't feel like looking it up.

The Hitchhiker's Guide to the Galaxy trilogy (in 5 books) has a lot of fun with time travel - and pokes fun at some of the ideas frequently seen in books and movies.

Science has basically this sorted out, in 'theory' there is no other option than what we have now like ion or chemical or compression for propulsion. Non. There are wild hypothesises from theoretical work, but the energy needed amounts to the output of many suns at the same time. Anyone here is familiar with what happens with that amount of energy/mass in one place? For now nothing with mass has been observed moving at light speed, the LHC try to push the limit as far as possible spending enormous amounts of energy to move some houndred thousand of protons close to light speed, the construction has a mass of hundreds of tons. All this is infuriating as I want to flag down a saucer and get off of this rock (towel is ready) but the prospects of ending further away than, say Mars, is just not there.
There are two objects that humankind has made that now has reached interstellar space (we assume) and they started that journey in bl**y 1977. (https://en.wikipedia.org/wiki/List_of_a ... lar_System)

This popped up on the news today:

https://news.yahoo.com/warp-drives-phys ... 33579.html

For the record, I think they are barking up the wrong tree.

↑ Old news, but with a new cherry on top.

Like the author says, I will not fully trust the mathematical models until there is experimental proof; or, as the great philosopher Benjamin Brewster put it in 1882, "In theory there is no difference between theory and practice, while in practice there is".

I will hold my enthusiasm in check until an actual FTL flight is made.

I liked the worm holes in Contact (the movie).

My oldest son told me he didn't like Star Trek because of the Warp Drive - which didn't make any sense. He preferred Star Wars because hyper-drive made sense.

I asked him how the "Hyper Drive" - if it made sense - worked.

He started to give an example of bending a piece of paper, and how if you could just put a hole in the piece of paper you could take a short cut from one place on the paper to another.

I asked him if bending the paper might also be called "warping" the paper. He said "no - well think of it this way - think of a small worm traveling on the surface of an apple". I asked what you might call it if a board was bent like the surface of an apple. Might you call that "warped"?

He stopped and said "Well I'm just saying the Hyper Drive concept makes more sense to Me".

Cannot argue with that.

The closed star is less than 10 light years away. You could travel to the nearest star in about 20 years if you could move at half the speed of light. FTL not really needed. 40 years if you could travel at 0.25 the speed of light. Doable.

The point about what we "have done" as opposed to what we "might do" is well taken. No man-made object HAS gone as far as one light-year distance. Experiments with a nuclear rocket have been tried - the dollar cost and time (politics change every 4 years in the USA) shut the project down. Less mass and more thrust. Anti-mater rockets violate no physical laws, but the cost is many order of magnitudes above any real project which has been tried.

I was trying to understand the difference between the "hypothetical warp drive" and it has to do with wave propagation which can actually move at FTL - but you cannot really ride it.

Once you accept the idea of N-dimensional space the idea of a wormhole or some other kind of way to take a short cut around 4-space can make sense from a purely theoretical point of view.

The idea of "hypothetical hyperspace" is actually that there may be a nearby dimension which has different physical laws - and the speed of light isn't a limit there. This is different from the wormhole or the warp drive. But still purely fictional. For now.

Quantum Entanglement is just plain weird - it might be explained by N-dimensional physics. The last time I looked at it physicists didn't really think it could be used for FTL communication since you couldn't really use it to sent information.
I don't understand it well enough to guess if it is the next big thing or just an oddity. FTL communication violates causality - but the universe might not mind - causality is just part of our model, perhaps not the universe.

The laws of aerodynamics get very strange as you approach the speed of sound in air. Eventually we solved that one and "broke the Sound Barrier". In the first episode of "Star Trek" a young man announces "we have broken the Light Barrier". Well that is pure fiction for now. Who knows what the future holds. Maybe quantum gravity or zero-point energy or dark matter (WIMPS) (etc, etc) holds some surprises. Still plenty of things we don't know about.

There is a real theory that some dimensions are "rolled up" and can only be seen sub-atomically - there are allusions to this in the Marvel movies where they are able to solve time travel by shrinking down into the "nano-realm" (whatever that might be).

It is fun to think about. And Wonder.

Put very simply, to quote the great Atomic Rockets website: "Relativity, Causality, FTL travel: choose any two."

You can have both relativity and causality, but that means no FTL travel.  You can have Relativity-conforming FTL travel, but that means inviting causality paradoxes.  Or you can have causality-obeying FTL travel, but that means throwing the substantial part of relativity out entirely, namely the axiom that there are no special reference frames.  If you have such a special reference frame (hyperspace, the energy grid, whatever), then you're fine in the causality aspect while you're zooming across the universe, but you have to be painfully aware of the other implications of throwing out the core principle of the most well-tested theory/theories in science...

Source:  This Reddit Page 

Nobody liked "throwing out" Newton to make way for Einstein but they had to. This little thing called "evidence" kept gumming things up. And truth be told Newton still works most of the time on the usual cases. Causality may be hard and fast or it may break in very special corner cases. The Michelson–Morley experiment caused people to have to throw out the idea of Either. When the experimental evidence doesn't match the theory - no matter how well accepted or well tested - the theory will have to change. There are probably other examples. Those are just two that come to mind.

The Higgs boson breaks symmetry.

The grand unified theory will require some kind changes when physicists can find one that agrees with all evidence.
4 dimensions will not be enough for that.

Theories have to follow the universe and not the other way around. Every "law" of physics is a mathematical model. Einstein said "To the extent math refers to reality, we are not certain to the extent we are certain, math does not refer to reality".

Hitchens Razor: What can be asserted without evidence can be dismissed without evidence.

Newton's Flaming Laser Sword: If something cannot be settled by experiment, it is not worth debating.

Here is an example of Physicists to not completely dismissing the possibility of FTL

https://en.wikipedia.org/wiki/Faster-th ... eplication

Note that it was investigated as possible.

Given any reasonably-sounding claim, a good scientist will investigate.

However, the mere investigation does not validate the claim; only results that match the claim will do so.

Take a generic forensic scientist, for example.  She receives the claim that a dead person was murdered.  The claim is based solely on the circumstances surrounding the dead person (e.g., circumstantial evidence).  Being a good scientist, she investigates.

If she finds no evidence of "foul play" -- no wounds, no traces of poison, no signs of violence or neglect, et cetera -- then she must conclude that the death was due to "natural causes", and that the claim of murder is invalid.

If she finds a puncture wound, a bullet hole, or some other signs of an inflicted death, then she must conclude that the death was either a homicide or a suicide, depending on the locations of the wounds and the condition the body was in when it was found.

Mere investigation (or suspicion) does not validate a claim; results do.  Suspicion indicates interest.  Investigations indicate activity.  Results indicate validity.