We are not going to be doing any interstellar space travel

News flash: I’m not a scientist, or an expert in any field. However, I can do simple math and I also read what scientists have been saying.

The obvious conclusion: Travel between the stars is, in fact, a pipe dream. NASA, however, will lose all funding if they talk about how we will not be leaving this star system in the foreseeable future, so they pretend like they’re working on it.

Now, I’ve just gone and pissed off a lot of you folks. I apologize, I know this is like being told Santa Claus isn’t real, and God is a man-made fiction. I know you’d like for space travel to be a reality. Me too, by the way. Well, we will be able to travel within the solar system just fine. The issue is **interstellar **travel. It’s not going to happen.

Sorry, fans of Star Trek. Your dreams of humanity spreading through the cosmos are ludicrous. Now I will explain why I feel I can make such a prediction, and say it’s conclusive. I can’t account for technologies that may be discovered in the future, you say? Well, this is true. If science figures out how to create literally infinite amounts of energy, then my explanation holds no water. However, there is not an infinite energy source within the star system of Sol. Atomic energy is not infinite. The sun’s radiation is not infinite. Fusion power is not infinite. Even matter converted completely into energy, with almost no energy lost from the conversion process, is not infinite energy. And several interstellar travel plans require infinite energy.
Warp Drive

This is pure fiction. It is true that we can bend spacetime. However, even something as massive as a black hole with the weight of 100,000,000 solar masses only bends spacetime around itself, it does not create a conduit to another part of the galaxy. And, need I mention, we do not have 100,000,000 solar masses worth of matter or energy inside our solar system. Therefore, we do not have access to that amount of energy. Scientists have no known process of bending spacetime using gravitation which in any way causes warp drive to be possible. We can’t even replicate the kind of slight bending in spacetime that occurs around a tiny object such as the Earth, without a mass the size of the Earth. That kind of gravitational effect is small and localized around the object in question, and you won’t be transporting the Earth with you on this interstellar voyage.

The amount of energy required to bend spacetime around even a tiny vessel would be far beyond anything we can produce. It could only be accomplished by converting an extremely large amount of matter directly into energy, such as instantly converting a planet the size of Jupiter into the kind of energy required to curve space. The mechanism for doing so is unknown, but even assuming we master matter to energy conversion, even assuming we master the ability to conduct such an extreme amount of energy through a machine of some kind (it would completely obliterate any material it passes through), and even assuming we knew how to convert that energy into a spacetime warp around the vessel, we still have numerous problems, Houston.

  1. You only have so many planets to consume. There aren’t many between the stars that you can stop and scoop up. If something happens to your spacecraft en route (just wait until you see where the real problem is) you just blew up a planet to move a ship into its own doom. You’ve accomplished nothing and the star system has one less planet in it. Congratulations.

  2. You’re warping space. That doesn’t mean you are invulnerable to the matter that you’re passing through.

It will completely obliterate your spacecraft at any speed which is a significant percentage of sub-light speed. And we’re talking about bending space for the explicit purpose of getting near (or somehow exceeding) light speed. You run into tiny asteroids, dust, interstellar gas (between the stars is not void, but a very thinly dispersed matter field called the “interstellar medium”) at anything close to light speed and the matter will create conditions similar to the big bang, and your entire space vessel goes KABLOOIE. This effect is not lessened by warping space and going faster. It just means you’ll be warping that matter toward your space vessel at even higher energy levels, which means you’re going to be obliterated even harder. You know how landing an aircraft in the ocean is fatal at a high enough speed? You know how big huge giant asteroids made of iron completely incinerate just moving through an atmosphere at a high enough velocity? Well, we’re only talking about speeds of about 100 to 1000 miles per hour. Now imagine you’re traveling at 500,000,000 miles per hour. This is a velocity where you are not yet moving at light speed. Run your spacecraft through any kind of matter, even if it is interstellar gas, and you’ll be obliterating trillions upon trillions of atoms against your spacecraft every second, even though they are “thinly dispersed”, you’re still covering 500,000,000 miles in an hour, which means you’re hitting trillions of atoms every second, even if there’s less than one atom per cubic meter. This is the equivalent of trying to fly through an asteroid at mach 17. You’re not going to make it, boy-o. And not even if you make the ship out of as of yet undiscovered fictional material Unobtainium. There are precisely zero forms of matter which will survive such an impact. You could be made out of neutron star material, you will still be completely obliterated. Therefore you will never, ever, ever, ever, ever, ever even *approach *light speed. You won’t even come close.

And we’re ony talking about the relatively easy part, which is getting up to that speed, and moving in a straight line. Yeah, we have the technology to do that now. It will just take a long time, and it will require an ion drive. We know how to make them. They are capable of continued acceleration without massive numbers of tons of chemical rocket fuel. But we won’t be able to move in a straight line. And we wouldn’t want to move at that speed under any circumstances. I’ll tell you why. But first, another mythological creature:

Okay, warping space to create warp drive requires energy which can fold space in front of and behind a spacecraft, and to sustain such energy levels for hundreds or thousands of years. It’s completely prohibitive.

A wormhole is a fictional structure created out of warped space, connecting two distant parts of the galaxy. The structure of which must be generated in the first place, and then maintained long enough for a ship to pass through it.

Problem: We can’t even fold space around a tiny spacecraft. Or a pound of dirt, for that matter. The energy level required to fold space across the distances between the stars would be infinitely higher than that. Black holes that occur naturally require much more matter than is in our solar system. So to even have a shot at this, you’d need to collapse all the matter in the solar system, and even then, all you have is a useless black hole, not a wormhole. You’d need to collapse a black hole at your destination point as well, or instantly generate the equivalent amount of energy. Once again, how are you going to find it? And problem number two: How do you get there to form the other end of the wormhole?

You’d need to travel there first, wouldn’t ya. And therein lies one of the many problems.

And we don’t know jack about wormholes other than, for a fact, it would require a nearly infinite amount of energy just to create one. Then, you’d need to keep it from collapsing using something that generates an anti-gravity force. Otherwise the entire thing collapses within tiny increments of Planck time. Nothing we know of generates a natural anti-gravity field, and you’d need to generate a field EQUIVALENT to the amount of energy you used to create the damned wormhole in the first place. A nightmarishly large amount of energy to breathe life into this completely unrealistic monstrosity, and a nearly infinite amount of energy to keep it from collapsing, and that energy has to be of the negative variety, by the way, to generate an opposing field. You’re not going to do this with magnetism or the strong or weak nuclear forces, because the wormhole has to be large enough to allow for a spacecraft to move through it. So the nuclear forces aren’t far-reaching enough. And gravity overpowers magnetic AND nuclear forces combined at those energy levels. That’s why iron can be crushed into neutron star matter- the magnetic repulsive forces and the nuclear weak force cannot overcome gravity.

So in total, you’d need the force equivalent to a black hole being instantly created in star system A, and in star system B, and the force equivalent of several black holes’ worth of anti-gravity energy just to keep it from collapsing, we’d still need to know how to convert the energy into a folding of space, we’d still need to know how to connect the two ends of the fold, we’d still need to travel to star system B in the first place, and did I mention this still requires an infinite amount of energy?

This is never going to happen, and even if we could do it, we absolutely shouldn’t. We shouldn’t consume the entire matter of a star system just to travel to another one. It’s pointless. That means we can’t try again if we fail. The cost is too high.You could know how to do it, and you’d still need the fleets of regular spaceships to go collect all the matter in a star system, and then you’d need to obliterate all the matter all at once and convert it to energy, without screwing it up.

This is as much within our means as reversing the expansion of the universe. It is entirely beyond the power of human beings, even with technology that allows perfect conversion from matter to energy, there just isn’t enough matter in our solar system. Therefore this is not viable.
Any significant fraction of speed of light travel


In order to survive the forces exerted on the ship itself, and the human life contained within it, we travel at a rate of acceleration which amounts to approximately 1 G, and little more than that is recommended. If you were able to put 1 G worth of acceleration on the vessel, and provide that level of energy continuously, you can reach a considerable fraction of light speed at a reasonable time frame.

Assuming you can convert matter to energy so efficiently that it is economically feasible to have a constant rate of acceleration, you have the following issues.

  1. It will take you as long to slow down as it did for you to speed up

  2. The Oort cloud extends out to approximately 1 light year. You cannot navigate such a field at anything near light speed, because navigation will be impossible. What happens when you turn a vessel at near light speed? When you are turning, you create an arc. The more massive your craft, and the faster you are moving, means it is harder and slower to turn the ship. Remember Titanic? Couldn’t corner worth a damn and that’s when we’re traveling at steam ship speeds, and we’re talking about a vessel not nearly as massive as an interstellar space ship would end up being. You try turning to avoid an asteroidal “iceberg” and you will do one of two things- either fail completely in turning the ship in time, or be destroyed by the lateral forces required to turn it.

TL;DR- The Oort cloud means you’ll be traveling at very slow speeds just trying to exit the damned Solar System. It will take you hundreds of years just to get out of this place.

  1. The Oort cloud would be awfully strange if it is the only such cloud in the universe around a star system. You can bet the future of humanity on the fact that there will be a similar cloud around every single star in the heavens. Which means another several hundred years at very slow speeds when you arrive at your new star system, just to safely navigate through the cloud around that star.

  2. You’re still running into gas, dust, and ejected material every now and then in distant interstellar space, and there will be absolutely no way of detecting or avoiding this material until you’re blowing through it at near-light speed, which destroys your ship in every case.

  3. Rogue planet


Yeah, sometimes this happens. And we have no idea how often. But it’s a fact- things get ejected from star systems, and star systems have been around for most of the history of the universe. That means there is a crapton of interstellar objects of a size greater than a grain of sand, and yes, some of them will be bigger than the freaking planet Earth.

You can’t avoid hitting one if it is in your path and you’re traveling at near light speed. But you were already incinerated just from the dust itself, so why are we worried about a planet? The odds are low that you hit one, but if you do, your journey is over. And that means you’d need to be able to detect and avoid interstellar objects with a mass greater than a grain of sand, even if you were able to survive impacting interstellar gas and dust at that speed, which you can’t.

And there is absolutely no way to avoid hitting the gas and the dust, which again, is completely fatal at those speeds, under all circumstances. You could make the hull out of pure titanium, and put a “cow catcher” several hundred miles long made out of solid steel, and the gas you’re hitting will be the equivalent to the Large Hadron Collider’s worth of energy release per atom, creating conditions similar to the Big Bang, on the nose of your spacecraft.

In short, your space ship will be flying into the equivalent of what the universe was like seconds after the Big Bang, every second, for THOUSANDS OF YEARS. Your spacecraft was destroyed, no matter what it was made out of, long before the first year had ended.

So that means you travel at very slow speeds between the stars, or you don’t travel at all. This means your journey can take hundreds of thousands of years.

Which means we won’t be doing it at all, because by then, the star system we were traveling to is now a few hundred billion miles away from where it was when we began our journey, because these stars aren’t stationary. They’re moving toward and away from us at great velocities. And even if you could find an intrepid crew to board your interstellar craft for a hundred thousand years, you’d have to put them all in stasis, because nobody is going to be part of the human petri dish experiment for 100,000 years of traveling awake and alive in a generational ship the size of the international space station IF WE’RE LUCKY.
The journey itself at speeds less than 1% of the speed of light

Perhaps we really build a magnificent craft, and it is the size of an office building. Could you imagine building something that’s going to survive for 100,000 years of human inhabitants and interstellar debris and radiation, and vibration and turbulence? Could you imagine living for 25,000 generations inside an office building that never changes? We have the entire planet to roam on and people still go absolutely batshit insane and blow themselves up. Try containing humanity for 100,000 years inside a building and ensuring that nobody goes crazy and explodes the hull. So stasis for the entire journey is recommended, and that includes while navigating asteroids and dodging comets. So the computer has to fly us there and keep us alive. And we’d better hope it never overheats, never needs human maintenance, never breaks down, never needs replacement parts, never experiences an error, and so on, and so on. And we have to hope our hibernation stasis never gets interrupted for any reason, ever.
We manage to get there somehow

And if we do manage to get to the next star system, we find that none of the planets there is capable of supporting life, or that the one that is, has no life on it, and will take many, many generations of planting and farming bacteria and other life forms and creating an eco-system. So we could be orbiting our new Earth for 1,000 years before it is remotely habitable. And in such a case, we’d be better off just colonizing Mars, now wouldn’t we?

And perhaps we find it is already inhabited. We won’t know until we get there. And when we find out, we find out the planet is inhabited with life forms which will utterly destroy our immune response and turn our organs into liquid shit. We have absolutely no defense to alien germs.

Bottom line: I predict that 100,000 years from now, there will still be no human life outside of this solar system. And the feeble attempts we make to leave this star system will fail, and continue to fail for at least this long. Wormholes and Warp drive will never happen, and slow sub-light travel will be too expensive and time-consuming for us to bother with. Finally, life on Earth gets wiped out by a natural or man-made phenomenon before the 100,000 years are up, and even if we happened to colonize Mars, the Mars colony withers and dies without mother Earth’s help.

Cue your TL;DR reactions. If you can’t make it through this post, you’ll never make it past the asteroid belt, buddy, let alone the Oort cloud.

“It’ll never fly.”

Don’t listen to him, Trekkers! I’ve created a neutron Warp Drive that will transport you instantly to far away galaxies! I know it looks like an old grain silo with a bunch of deadbolts that lock from the outside, but looks can be deceiving!

You too, House DJs. Don’t you make me turn on the hose again.

That sucks. Deep down I always knew this to be true, but I appreciate your detailed but very readable reasoning.

In your opinion (anyone can chime in), how does this shape your attitude toward interstellar communication? It’s looking like that, at least, might happen… 50 years between messages (let’s say) brings its own challenges, but less insurmountable. But what will it mean to talk to “folks” we know we can never meet? I guess a bit like friends or family members who live on either side of an uncrossable border, but who can exchange letters (surely this has happened in human history, probably somewhere right now) – writ large.

More likely still is that we will detect life forms on some exoplanet, and know soon after that they’re not “intelligent” in any way. We’ll be able to say something like, “90% probability it’s pondscum, 10% probability it’s more like a slime mold,” and that’s it. We’ll never be able to get close enough to know more.

Or – does removing the human body from your scenarios help things at all? That is, might we be able to send a vehicle to said exoplanet and have it return to earth with a stlll-living sample of said pondscum?

Send several (for redundancy) lightweight, high speed probes to another star; upon arrival they use local materials to build a laser receiver and colonial/industrial infrastructure. Some time afterwards, a communications laser arrives encoded with the recorded mind states of a number of humans (or whatever); new brains and bodies are constructed and the minds downloaded into them. Off the top of my head there’s one scenario you didn’t cover.

Not at all. At astronomical distances it takes only a tiny nudge to miss an object. The last thing you would want is to turn at right angles like an ocean going vessel anyway; you’d be giving up all your forward velocity.

That’s a serious exaggeration.

Why? If you’re going slow, build big; big enough to hold a town’s worth of people. Have the thing travel between those comets and rogue planets, harvesting useful materials as it goes so it never runs out of fuel and supplies. Every so often it stops by a large chunk of interstellar debris, builds another ship out of it and moves half its population there. Keep this up for long enough and interstellar space will be filled with an ever expanding cloud of these ships traveling in all directions.

Eh. If we’re talking realistically, long before then either we won’t be human in any biological sense or we’ll have been replaced. And by then our descendents will be used to living in space and will likely be more interested in colonizing that than any planets in the system.

Personally, I predict that in a few centuries at most there won’t be a significant amount of what we would call humans anywhere, in or out of this system.

:rolleyes: No, if we ever do colonize this system there’s no reason to think that the colonies would be dependent on the homeworld. Especially since preventing such a extinction scenario is one of the major reasons to colonize space in the first place.

Last question – what about unmanned flybys of exoplanets (once they’ve been definitively detected)? Will it ever be worth the time and expense just to get some nicer pictures (and geologic tests, if they land) of those planets? (I’m talking about the closest ones, which by the law of averages I’m assuming will NOT harbor life.) I guess the answer depends partly on how good our Solar System-bound telescopes and such can ever get.

I’m holding out for galactic colonization by the silicon-based children of the mind of Man. On a crusade to find and wreak vengence upon the race who caused our extinction.

The current issues of Skeptical Inquirer has a good article on this. I thoughht this was what might have set the OP off, in fact, but he doesn’t seem to give any indication that he read it. The SI article, in tyuirn, cites in large part an appendix to a 1960s article by Edward Purcell* that considers practical near-lightspeed travel in some detail and shows that it wouldn’t be practical.
Occasionally SF writers will point out how extremely hard and unlikely the realities of near-luminal speeds are, but this makes for short, depressing, and often dull stories, so they take really high speed trabvel as a “given” asnd see wghere that gets them. It’s really no different from Jules Verne making the assumption that firing his heroes out of a cannon (in From the Earth to the Moon) wouldn’t simply smash them to pulp, sop that he really could proceed to the interesting stuff.
And occasionally someone will suggest a workaround. Physicist and Robert L. Forward wrote a book entitled Indistinguishable from Magic, in which he alternates essays about seemingly improbable high-tech possibilities with stories that use them. One of his favorites is near-luminal travel, and he devoted considerable time and effort to the topic, coming up with his “Starwisp” concept of laser-light-pressure-driven ultralight craft. For this, both the effective “engine” and the effective “reaction mass” don’t have to be carried aboard and accelerated along with your payload, so you can avoid the absurdly higfh mass-to-payload ratios even matter-antimatter engines would, by Purcell’s calculations, require**. But it’s still a helluva huge effort and expenditure. Neverheless, his concept has been published in respectable journals, and I heard him lecture about it at a meeting of the American Institute of Astronautrcs and Aeronautics.

*Physicist and nobel prize-weinner. And author of my first college text in Electricity and Magnetism.
** Purcell came to the conclusion that using matter-antimatter you could accelerate to relativistic speeds with a ship-to-payload mass ratio that’s about a single order of magnitude (a factor of teon or so). But if you actually wanted to slow down and stop, it required a couple of orders of magnitude. For even perfect fusion-fueled accerelation the ratios were completely absurd.

I’m not aware that NASA relies on the notion of interstellar travel for any funding; they have a hard enough time getting funding for interplanetary work.

Of course we will colonize Mars before any substantial push to the stars (if we ever get off this rock to stay). That hardly impinges on the necessity to go beyond.

I didn’t see any comment on sublight voyages other than generation and sleeper ships. What about digitized minds, robots, and stored DNA? We don’t have to transport whole people across the gulfs; we build them on arrival, or we don’t bother with old-style biological bodies at all. So send out as many relatively-small probes as we can build, and accept that some fraction will go awry or be destroyed.

As for the predicted demise of humanity within 100,000 years: quite possible. But shouldn’t we try to avoid that? Preserving our home world (as long as the sun remains amenable) and reaching out as far into space as we can manage–these seem like they should be fundamental species motives.

Why do you hate humanity, pizza man??

In other words, we might not be able to colonize other planets, but maybe we could help exoplanet life forms colonize us.

Not such a great idea after all. Oh, well.

So… no pizza delivery to Alpha Centauri, then?

I’m not so sure. That’s why my follow-up questions focus on the feasibility of interstellar travel for:

  1. Human bodies (looks like it’s pretty unlikely)
  2. Lower life forms/soft tissues (exoplanetary pondscum; earthly mozzarella, pepperoni, or tomato sauce…)
  3. Just an unmanned, unpizza’d probe
  4. Messages

Delivery in 30,000 years guaranteed or your pizza is free!

I see these arguments made sometimes, like it’s ‘manifest destiny’ to colonize Mars, or extend our species life span. 99%+ of life that ever lived on Earth have gone extinct. What makes us so special?

IMHO, our efforts and resources are better spend in solving earth-bound problems. Otherwise, we are likely to snuff ourselves out or soil our nest long before technology provides a life raft to some other place.

I’m going to go total nerd here and state that the utilization of space is the solution to our earth-bound problems.

Over-pessimistic on several fronts:

  1. You don’t need an artificial black hole to create a warp drive, and the energy requirements might not be as bad as first thought. There are already proposals for laboratory experiments to detect whether a warp effect can actually be created, although no one is proposing that a Zephram Cochrane will appear in our lifetimes.

  2. The Oort Cloud is not a boulder-strewn rubble field like the Millennium Falcon went through. The bodies in it are estimated to be separated by distances comparable to the width of our solar system. Gas and dust are an acknowledged problem, and most proposals for fast interstellar flight presume some sort of system for clearing the way- lasers, or magnetic shields, or expendable drones.

  3. No one proposes a 100,000 year journey; 1% of the speed of light would get you to the nearest solar systems in about 500 years, 5% within 100 years. Presumably long before we could launch such a journey we’d be familiar with keeping people alive and well in habitats within our system. And no the colonists wouldn’t be crammed into a ridiculously small ship.

  4. If we’ve learned to live in our solar system beyond Earth, we don’t need a viable ecosystem waiting for us at our destination. See above about keeping people alive and well in habitats. Interstellar colonization isn’t going to be a Heinleinesque “Farmer in the Sky” scenario of neo-pioneers building log cabins and plowing the new land.

Then you had better come up with a way to stop Voyager 1, if it is not already travelling in interstellar space.

For your value of “we,” maybe. But there is more to the Universe and physics than is comprehended by your puny Earth brains.

Radiation is a problem for sending humans to Mars. Some of this radiation comes from the Sun, but some of it is galactic cosmic rays. That’s going to be a problem if you’re talking about a longer space voyage than a Mars mission. It might also make your pizza taste funny when you finally get it.

If you get a pizza 30,000 years after you ordered it, do you take inflation into account when figuring the tip? :wink:

I think his other rants about his pizza delivery costumers explains the reason quite well :slight_smile: