Breaking the warp barrier for faster-than-light travel | Hacker News Reader

Breaking the warp barrier for faster-than-light travel

uni-goettingen.de

87 pointsmrrazz74 comments

It is early in the morning, so I'm still irritable, but this line is pretty egregious

The energy savings would need to be drastic, of approximately 30 orders of magnitude to be in range of modern nuclear fission reactors.” He goes on to say: “Fortunately, several energy-saving mechanisms have been proposed in earlier research that can potentially lower the energy required by nearly 60 orders of magnitude.”

Say the fission reactor they have in mind is a collection of the biggest in human history and is a whole terawatt (1E12 watts). Another 30 orders of magnitude less power brings you down to 1E-18 watts.

For context[1] a typical human cell consumes ~1E-12 watts. You could take a morning coffee poop and put it in a jar with a thermocouple and power your warp drive with the decomposing biomatter if those results are right.

If the energetics are that favorable I would really like an explanation why we haven't encountered space whales, let alone rapidly expanding alien civilizations.

[1]https://en.wikipedia.org/wiki/Orders_of_magnitude_(power)#Be...

For a long time I thought of the sun as being the product of many cycles of recycled material from older suns - but if you look at the cosmic calendar our sun has been around for roughly half (a little less than) the age of the universe! For all we know we could be the first intelligent species to reach the space age in our observable universe.

The older stars were bigger and therefore had much shorter lifetimes, so the Sun indeed is made of the guts of several generations of stars. The Sun is at least the third generation down from the Big Bang.

The noise is huge though, the whole Mesozoic era was just a random delay for our evolution, imagine if it didn't happen or was shorter. Time needed for development of civilization and travel around the galaxy is an infinitesimal perturbation in such huge noise.

It is a strangely worded sentence for sure, but it's probably referring to previous sensitivity analysis done on the original Alcubierre negative mass-energy requirements:

https://en.wikipedia.org/wiki/Alcubierre_drive#Difficulties

60 orders of magnitude is about the difference of the mass of the observable universe to 'a few milligrams'.

If aliens ever visited us they may be blown away that the majority of our bodies are made up of rocket fuel.

University of Göttingen alum here, in our astrophysics courses we used to make jokes about how generous the approximations were. Comparing x^2 with x^5, take log on both sides, 2 ~= 5, so x^2 = x^5 ... Appropriate xkcd: https://xkcd.com/2205/

One of my favorite derivations in stat mech is for the Chandrasekhar limit where you start by assuming pi=1 because you say stars are cubes.

Something makes me want to continue that xkcd strip with a CS approximation with something about all of those being just constant factors.

It currently requires 1e42 (say), and 30 orders of magnitude less brings it into the realm of possibility with a large power plant.

Continuing with the assumptions, it takes /us/ 1E42 watts, but the authors speculate that the universal lower bound is indistinguishable from 0. Much like how we can't make a useful fusion reactor, the universe at large has made loads of them because. If their suspicions are right and the lower bound is so low, it would need to be some incredibly contrived collection of events to not occur naturally with some regularity.

An improbable drive?

I presently have no time to get into GR, but surely wish I did. Here instead of comment I offer two papers: Erik Lentz (underlying the work in the press release here):

https://arxiv.org/pdf/2006.07125.pdf

And similar seeming work by another group at something called the “advanced propulsion lab” (who are they?)

https://arxiv.org/pdf/2102.06824.pdf

It’s interesting that they both claim positive energy solutions that, eh hem, do the trick.

Is there any physical proof that theory is sound in those papers?

I mean have they tried to send anything electron, atom or anything small that would confirm FTL speed ?

No they just wrote it down. These are not experimental papers.

A smallest possible scale experiment would the logical follow up, unless some GR expert shoots holes in the models on paper first.

Edit: ftl is not the experiment in question. Simply demonstrating some minuscule effect due to manipulated spacetime curvature would Be quite enough! (Enough to be a huge deal, even if it’s not even useful practically, for the foreseeable future)

We don’t need hyperexotic negative energy to travel to the stars, we just need to live a lot longer, and we need our friends and family to live longer too so we can comeback and see them again.

I kind of disagree here. 50 thousand years — it doesn't matter if people are biologically alive. You, your friends, family, society, relationships — would all be very, very different when you come back.

If you just meant "see friends and family", yeah technically you could see each other I guess. Practically, might as well be an alien.

You haven't met my family, I see.

It's a solved problem: just make the stars your home and live there. The ability to live among the stars is required for interstellar travel. That will be your place to come back. Those who travel among the stars don't live in dirt like earth pigs.

I would like to know more about how this problem was solved, so that I too may be freed from the indignity of living like an earth pig.

You take an instance of the people you want to take with you, and they take an instance of you in return. It won't feel like goodbye.

50,000 years later you sync memories if there has no been trickle of communication in that time between you and your instances

do we read the same greg egan books?

50.000 years is a bogus number. No serious space engineer calculates with that. The goal is 1/5 lightspeed, which would mean 25 years.

Unless some really freaky physics discovery is made (allowing FTL travel), and I don't believe at this point that that'll ever be done (or if it will that it may cause a sudden cataclysmic event), I don't believe we'll ever become interstellar travelers.

More viable at this point is that we'll develop Von Neumann probes. But that depends on whether we manage to develop computers smart enough to fully independently harvest resources and self-reproduce.

Before that, it'll be projects like Voyager, deep space probes that contain fragments of our knowledge and culture. If there's other intelligent species out there, there may be a slim chance that they'll be found, eventually. But the chances are slim. Maybe if there's a lot, they get sent to start orbiting distant stars, and can start broadcasting.

But given that it takes tens of thousands of years to reach the nearest stars, it's unlikely that the probes will be anything but dead chunks of slag by the time they arrive.

But given that it takes tens of thousands of years to reach the nearest stars, it's unlikely that the probes will be anything but dead chunks of slag by the time they arrive.

You're not exactly saying meteorites are the remnants of alien probes, but you're not not saying that either.

I agree but the nearest star is (only?) 4 light years away. If we only managed to travel close to the speed of light, we surely live long enough today. Time dilation will cause our friends to be older by a few years than they should be, but not by that much right?

There is a cool calculator of what happen if you travel around with constant 1G acceleration.

Long story short: to travel to Alpha Centauri it would take for the traveller still about 4 years, and when back at home, people would have aged only some months more than the astronauts.

Crazy things happen if you decide to go on galaxy-wide trips though, to the astronauts because space contraction they perceive their own trip as happening still rather quick, a 100 000 ly trip (the size of our galaxy, for reference) takes 22 years for someone inside a spaceship with 1g acceleration, perfectly doable. But people outside still see it taking 100 000 years... (meaning they will be 100 000 years "older" from the point of view of the astronauts)

After I found all this out, I concluded space travel isn't THAT hard, assuming you have a way to accelerate constantly at 1g for 22 years (that is the hardest part actually), you can get anywhere in the galaxy in a human lifetime, no need for generation ships, cryogenics or other crazy tech.

In fact even going to other galaxies is easy, a trip to Andromeda takes 28 years!

Mind you, all those calculations were done assuming you will burn at 1g until half the distance, and then burn at 1g to brake, if you don't brake you can get even faster to places (although that wouldn't be very useful I guess).

According to google the universe is 93 billion ly wide. If you accelerate (and decelerate later) at constant 1g, this trip takes 49 years for the astronaut!

> After I found all this out, I concluded space travel isn't THAT hard, assuming you have a way to accelerate constantly at 1g for 22 years (that is the hardest part actually), you can get anywhere in the galaxy in a human lifetime, no need for generation ships, cryogenics or other crazy tech.

Unfortunately, there is also a kind of rocket equation for constant 1g acceleration, and if I remember correctly it's not really doable for any realistic amount of time, even with matter/antimatter reaction drives.

I think because of the expansion of the universe, you don't have to decelerate as much if you travel to far away galaxies.

See the novel Tau Zero by Poul Anderson. https://en.wikipedia.org/wiki/Tau_Zero

I think you're forgetting that there's a hard upper limit on velocity.

Edit: Ah, wasn't aware of length contraction. https://courses.lumenlearning.com/physics/chapter/28-3-lengt...

You never reach that limit if you are accelerating with a normal engine at 1g. You will get closer and closer to it, but never reach it.

If you somehow DO achieve lightspeed, time stops for you, completely, so from your point of view you are teleporting, but since time is stopped no machine or chemical reaction can happen, thus why we believe lightspeed machinery is impossible.

By the way, achieving near lightspeed with 1g acceleration is in a way, hard, for example the trip to alpha centauri at 1g results in you achieving "only" 94% of light speed... to do that same trip peaking at 99.0% of light speed it would take 3g of acceleration, and it would result in the trip being roughly 1/3 shorter (taking 1.7 years more or less, instead of 5)

> Crazy things happen if you decide to go on galaxy-wide trips though, to the astronauts because space contraction they perceive their own trip as happening still rather quick, a 100 000 ly trip (the size of our galaxy, for reference) takes 22 years for someone inside a spaceship with 1g acceleration, perfectly doable. But people outside still see it taking 100 000 years... (meaning they will be 100 000 years "older" from the point of view of the astronauts)

But from your frame of reference wouldn't you be moving much faster than the speed of light? If you're taking 22 years to travel 10,000 ly, that means you're moving faster than light in your perception, doesn't it? Isn't that forbidden in any frame of reference?

From your perspective, the entire length of the milky way is squished into 22 light years (roughly), so not really violating anything. From the outside frame of reference you still take 10000 years (plus) to cross that distance, from your perspective, the distance gets shorter.

From your frame of reference, the universe is much smaller in the direction of travel. You'd still see light zoom past you at 1c, though.

Not on subjective velocity. As you approach the speed of light from an outsider's perspective from the insider's perspective the universe appears to shrink.

But if you experience 22 years to make 10,000 ly's of distance, you've subjectively gone much much faster than the speed of light, haven't you? I thought that was a constant in all frames of reference.

From your own perspective you are always stationary, it's just the universe that is moving (and shrinking).

Quote from the original claim:

They are saying add a constant 1g acceleration and you can get anywhere relatively quickly, no warp bubble required. That's what I'm taking exception to. If we add a warp bubble, sure, but a constant 1g acceleration shouldn't ever see you having an experience of moving faster than the speed of light, and that 10,000 ly trip should still take > 10,000 ly.

You move at a constant vector, the speed of light, through both space and time. Since you go from basically 0 magnitude in space (anything us humans do on earth) to approaching the speed of light, that robs direction from the time magnitude. Therefore, going that quickly means you experience substantially less time. Taken to the extreme, when you move at the speed of light, you experience no time; you would simply from a human perspective teleport to the place where you start decelerating (given that's possible lol).

No, you're misunderstanding.

From your frame of reference, the universe is much flatter in the direction of travel, and getting flatter and flatter the more time you spend. The distance between Earth and the edge of the galaxy will get smaller and smaller in your direction of travel.

Thanks - yeah, I realize now that the length actually shortens.

When you go fast, subjective experience slows down.

You'd have 22 years of thoughts, for example, even though 10,000 years of stuff happened elsewhere.

From the perspective of an observer on earth, the trip takes a long time. The people on the spaceship experience 22 years.

It's not about time dilation, I realize now it's possible due to the length actually contracting. https://courses.lumenlearning.com/physics/chapter/28-3-lengt...

If it didn't you'd still need to pass through 10,000 ly of space and if you were going at slower than the speed of light it would still appear in your frame of reference to be > 10,000 years. But contraction removes that limit and shortens the distance.

They are different sides of the same coin.

This is the realization that really made SR click for me. The fact that "in the traveller's frame of reference, the universe becomes smaller in the direction of travel" is the same thing as "in the traveller's frame of reference, time becomes dilated".

As an example, from the perspective of a photon, the trip takes 0 seconds, the photon is emitted and absorbed at its destination with no (subjective) travel time

> Time dilation will cause our friends to be older by a few years than they should be, but not by that much right?

Technically they wouldn’t be older, you’d be younger.

"relativity"

The trip becomes quicker (to you) the faster you go. If you could ride a beam of light, you’d be there instantaneously, thanks to length contraction. Meanwhile 4 years would pass on earth in some sense. (To an observer watching from earth with a hypothetical telescope, you are seen to arrive only after eight years total. Of course you could just ride the light back and tell him about it all, ha.)

With FTL you could wish yourself a good trip before you left.

Living longer would help. Changing society would help more. If you can engineer society towards some obsession with expanding through the universe, we could probably travel to the stars in our lifetimes. It'll be slow, shitty, dangerous travel though.

Coincidentally, Alcubierre recently posted a review article on warp drives: https://arxiv.org/pdf/2103.05610.pdf. It looks like a good introduction to this topic.

I am not a physicist by any means, so this may come off as a dumb question, but: If gravity waves have been discovered, and they move at the speed of light (speed of causality?), being thrown off by the most energetic events in the universe, how can something like an Alcubierre drive even work when essentially it is also a gravitational wave generated by far less energy?

It usually requires exotic matter with negative mass which isn't normally found.

This one supposedly doesn't, which is why it's so newsworthy.

I'm not qualified to judge the paper or its contributions, but this particular paragraph in the press release quoting the author smells of way, way too much faith on part of the author himself:

> “This work has moved the problem of faster-than-light travel one step away from theoretical research in fundamental physics and closer to engineering. The next step is to figure out how to bring down the astronomical amount of energy needed to within the range of today's technologies, such as a large modern nuclear fission power plant. Then we can talk about building the first prototypes," says Lentz.

While I'm not a physicist, calling anything in the paper's area even a single step towards engineering rather than belonging firmly in the realm of theoretical speculation is an astronomically huge claim. Extraordinary claims require extraordinary evidence, and so on. (FWIW, I'm totally fine with research producing only theoretical speculation as long as it's sound.)

While I (again) cannot judge the paper, that kind of a blurb by itself makes me automatically feel much more skeptical about anything in the study.

I know it's from a press release, and press releases are a kind of marketing, but they should still be somewhat proportional.

Does “Craft using an inertial mass reduction device”[1] use the same concept as described?:

I don’t know if there’s a difference between this and the Alcubierre drive.

Perhaps the tic-tacs were prototypes, given the patent and claims made by others. They may not be FTL capable, though, at least not within Earth’s atmosphere[2].

If the technology were to exist, it would be seen as a serious weapon and threat to security as much as a tool for colonization and exploration, so why a patent would be filed and left as much is beyond me.

I don’t want to legitimize make-believe things, though, if that is what they are, which is tough to say with much certainty.

[1]- https://patents.google.com/patent/US10144532B2/en

[2]- https://nymag.com/intelligencer/2019/12/tic-tac-ufo-video-q-...

If warp drives actually are feasible (either sub or super liminal), that'd be great. However, it seems to me that it's much more likely we'll travel between stars as digitized minds that are recorporialized at the destination.

That's only going to become a solution if you can convince people that the process preserves continuity of experience.

How do I know that I actually wake up on the other side, instead of dying and having a clone with my memories wake up instead?

I don't really see a difference. You experience a discontinuity every night when you sleep.

Of course, this entire concept is reliant on materialism. If you believe in a soul, then I'd probably find it difficult to convince you that a digital copy of you is close enough to being you.

> you experience discontinuity every night when you sleep

Something dubious about this. No one thinks they're annhiliated upon sleeping, then reconstituted upon waking.

Even adhering to materialism, the problem with mind uploads is the same problem as with teleportation: a copy is being made. Destroying the original does not mean a consciousness transfer then magically occurs from the original to the target. For mind uploads, the only plausible sounding way around this is the Moravec transfer, but even that is reliant on the Ship of Theseus thought experiment having a definite answer.

Some people do think that. There are whole fields of philosophy about it.

> Even adhering to materialism, the problem...

If you don’t require continuous experience, then this issue goes away. You certainly didn’t experience living before you were conceived. My view is that consciousness is an emergent property of informational and processing structure of the brain (and possible other systems as well)—-I don’t see any physical issues with copies (other than that it might result in confusion and social problems).

This seems naive. If you have a brain and you make a digital copy of it...you now have two copies (assuming you can even make a perfect digital copy, which seems doubtful). What does that mean for continuous experience? Who are you at that point? WHICH one are you? Then you kill the first one...effectively murder. Philosophers have never been credited with their practical abilities...only theoretical.

Uh, you're both. After that, the two copies would diverge, so they'd eventually have different experiences and personalities, but with a common past.

And yeah, killing one of them would be murder, if they've had a chance to diverge.

The video game SOMA deals with these issues to some extend; Who is the real you if you copy-paste yourself over to a new body? And what about the you that stayed behind?

Out of curiosity, what is the state of this research? That's the Takeshi Kovacs solution, but I haven't seen any real jumps in that regard other than some new tech allowing the brain to control computers to some degree.

And even if we do have that tech, we'd still have to be able to reach those destinations in the first place so we could establish outposts where our digitized minds could travel to. At the moment, the only way to do so is a generation ship capable of surviving the ~1000 years it would take to get to a new location with current technology.

There is foundational research being done on destructive brain scanning and emulation. It is decades—at a minimum—away from being more realizable.

You don't need to send a generation ship, just solar sails powered by massive laser installations that have enough tech on board to convert an asteroid into a receiver.

To be fair, 1000 years is not very long when you have digital immortality.

Is there even an electrolytic cap that survives a 1000 year space trip?

Probably not right now, but I don't see why it wouldn't be possible.

Anyhow, a laser propelled solar sail would make the journey to, say, alpha centuri in more like 20-40 years.

There's really not much point in slow travel if you can, instead, launch a self-replicator, wait a few decades for it to get there, and then just cast on over.

All fine until he cited the Proxima Centauri problem. He cites 50,000 years to reach it with conventional rocket tech. But this nearest star is only about 4.2 lightyears away, so there's no need for exotic warp-drives. Conventional 1/5 (20%) lightspeed rockets could do it also in a lifetime, i.e. in 25 years.

Soliton stuff is entirely unpractical, conventional tiny rockets are in our reach.

I wonder whether evolutionary algorithms could be of some use here, to help find good "shapes".

Star Trek TNG: New Ground [1].

[1] https://memory-alpha.fandom.com/wiki/Soliton_wave

protip: ET is already here.

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