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Comment by jandrese | Hacker News Reader

If it's malign there's really nothing we can do about it. A technology that can traverse the distance between solar systems is so far outside of our technology that it might as well be magic, and our current level of technology is already adequate to obliterate all life on the surface of the Earth. If you have power to travel interstellar distances the power to obliterate all life on a planet with no warning is trivial.

Ironically we might be in less trouble if they have FTL technology, since that might not require quite the outrageous level of technology you would need to do the journey with the physics that we know. The rocket equation is a harsh mistress.

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I don't believe FTL travel is possible, but if it were, the Fermi Paradox would seem to suggest it isn't obvious or trivial. It might require burning the mass energy of an entire star just to open a wormhole or hacking the matrix and forking the physics engine or sacrificing us to their chaos god patrons or something.

I think I'd rather deal with the aliens who just have really good rockets. At least we could potentially comprehend the rulebook they play by. Who even knows what the hell the Walkers of Sigma 957 are about?

IMO, If FTL was possible, something, somewhere, at some point in time would have engineered a self replicating organism capable of it. These things would be everywhere by now we would see evidence of them.

Like the plants that grow mattresses. I like it!

Another theoretical possibility is that any Alien life that is exploring the universe could be more resistant to acceleration / deceleration than we squishy humans are.

Perhaps they figured out AI or have made space-adapted biological life forms that can survive constant acceleration at 25Gs and are sending them out to scout the universe for other life, and once they find it they would signal back to the home planet.

25G of constant acceleration would kill any human, especially if it were maintained for the time it would take to approach light speed, but for an AI or a creature specifically developed to survive that it would make a trip to the Solar System from Alpha Centauri take 5-8 years.

Then again, if they could do 1G of constant acceleration that would only add like 2 years to the total trip. Long enough to be one-way for most people but short enough to be survivable under ideal circumstances.

Assuming they stopped outside of Neptune's or Pluto's orbit they would still have a few years of travel to make it to Earth but they would have started detecting our broadcasts long before arriving.

I'm not saying this happened, rather that it becomes plausible when you take some liberties with the starting conditions.

>25G of constant acceleration would kill any human, especially if it were maintained for the time it would take to approach light speed

>Then again, if they could do 1G of constant acceleration that would only add like 2 years to the total trip. Long enough to be one-way for most people but short enough to be survivable under ideal circumstances.

It would take ~2 weeks to to approach light speed while continuously accelerating at 25G. It would only take ~1 year to do so at 1G continuous acceleration.

On cosmic time and distance scales, those are essentially the same, especially since once we approach the speed of light, there's no going faster.

As such, tolerance for G forces seems pretty irrelevant for interstellar travel.

Doing so within the confines of a solar system is another matter altogether, I'd expect.

Humans die under 10g for more than a few minutes. Admittedly, we could position the humans to be in the optimal direction, but even 2g sustained for months would undoubtedly cause issues.

I picked 25G as it would be an insane but reasonable acceleration, and time is always a factor. Trimming 2 years off of a voyage might seem worthless on an intergalactic scale, since once you are more than a few solar systems away you're on the scale of AI scouts and generation ships, but for a close star like Alpha Centauri, 2 years (each way) might be the difference between a one way death march and the possibility of a heroic return home.

> Humans die under 10g for more than a few minutes

With no air?

It's not about the air. Its about our fundamental squishyness.

At 10g, a 150lb man would weigh 1,500 lbs. His heart isn't strong enough to move blood that suddenly weighs 90lbs/gallon that also has to push other blood that also weighs that same amount. His blood vessels, paper thin and easily torn under normal weight, suddenly have 10 times the amount of pressure to resist.

He's fine for a few moments, jet pilots experience short bursts of 10g during flights quite often, occasionally more.

Might pass out after 10-20 seconds, but after 10 minutes, his brain, starved of oxygen and squished under its own weight, ceases to function. His heart or his blood vessels rip and tear from the strain, and his body falls apart inside of its own skin.

It's not pretty, but it would probably be a fairly painless way to go.

Getting back to your question, his ability to breathe is not relevant under those situations. The absence of oxygen would accelerate his demise no more than it would under any other situation.

Grandfather paradox says the riders on the ship won’t experience most of the time of the ride

>Grandfather paradox says the riders on the ship won’t experience most of the time of the ride

No. The Grandfather Paradox[0] says nothing of the kind:

   The consistency paradox, commonly known as the grandfather paradox, occurs 
   when the past is changed in any way.[5] The paradox of changing the past 
   stems from modal logic: if it is necessarily true that the past happened in a 
   certain way, then it is false and impossible for the past to have occurred in 
   any other way, so any change to the past would be a paradox.[13] Consistency 
   paradoxes occur whenever any change to the past is possible.[6]
   
   A common example given is a time traveler killing their grandfather before 
   their parents' conception, thus preventing the conception of themselves. If 
   the traveler were not born, they could not kill their grandfather; therefore, 
   the grandfather proceeds to beget the traveler's ancestor who begets the 
   traveler. This scenario is self-contradictory.[5] One proposed resolution for 
   this paradox is that a time traveller can do anything that did happen, but 
   cannot do anything that did not happen.[5] Another proposed resolution is 
   simply that time travel is impossible.[14]

[0] https://en.wikipedia.org/wiki/Temporal_paradox

Sorry I spoke quickly. I meant the twin paradox and reached for the wrong label

A fun exercise is to calculate how much mass in rocket fuel you would need to accelerate at 25G for two weeks. Or even to accelerate at 1G for a year. Even if you assume a ridiculously high ISP like 1 million seconds (our current best engines are around 8,000 ISP, and they're severely limited in thrust) and close to unlimited energy to add to the mass. Like you're using antimatter to kick propellant out the back at relativistic velocities.

Now add in the mass to slow down once you begin to approach your destination.

I know I am not taking relativity into account but outside of that it's something like 250 kilograms (~550lbs) of antimatter (and that value again for the matter for it to react to) or the equivalent in other fuels. The only difference is how quickly you burn through it.

Which doesn't sound like a lot but its probably as much or more antimatter than exists in the entire solar system, so if it were the fuel then whoever was using it would need to have figured out a method to create and store antimatter in bulk along with the ability to react antimatter as rocket fuel without destroying the rocket its fueling.

Also, FTL technology existing would naturally abate the prospects of interstellar war under the Dark Forest theory, because it means FTL communication is possible; and factions that can communicate with each other quickly are far less likely to fight each other. This was, at least in the first book, a (iirc stated) reason why the Dark Forest theory exists.

Of note: It might not require the outrageous levels of technology you might expect to accelerate technology to the delta-v 3I/ATLAS is traveling at, simply because there are absolutely star systems near ours already traveling at a pretty large sun-relative delta-v. We get a ton of galaxy-relative velocity for free from our solar system; we just have to shoot the probe at slower solar systems. Putting (and surviving) biological life in there, however, is a different matter.

I don't know. We humans can communicate with one another quickly but war still exists, it just uses modern communications platforms for espionage, propaganda, attacking information infrastructure and controlling drone swarms.

I have a theory that what we need to reduce conflict in the future is not more speed of communication but more fidelity. At present we can only communicate in spoken or written human language, and this language is not just imprecise and ambiguous, but also untrustworthy (easy to lie with).

If you imagine for just a second a future technology that can transmit genuine opinion, intention and feeling in a way that is hard to fake and therefore easy to trust, it should be easy to see how wars could be averted. So any technology that's even a small step in that direction would probably help.

It would still require a stupendous amount of delta-v to slow down enough to be captured by the gravity well of the place you are trying to land though.

Also, the Dark Forest theory is based on the same game theory principles that said the US needed to nuke the USSR flat by the early 1950s, it should not be used without skepticism.

Spoiler alert!

Edit: the book is "The Road not Taken"

There's a scifi story about a civilization stumbling upon how to achieve FTL travel. In the story, the tech is at the same time very simple and very unexpected. Anyways, they go explore the galaxy and invade and conquer with their primitive ships, which are little more than tin buckets. Their weapons technology is on the flintlock gun level.

(A tragic kind of) hilarity ensues when they stumble upon Earth with its completely unexpected, incredibly advanced weaponry. IIRC in the story most civilizations find FTL travel pretty early. Just Earth didn't happen upon it and instead had time to develop advanced weaponry, computers, etc.

Ooh, thanks for this. Apparently it's here, and is short enough to read in a few minutes, so I know what I'm doing!

https://www.eyeofmidas.com/scifi/Turtledove_RoadNotTaken.pdf

Interestingly enough, the same world ending technology can be used for interstellar travel & could have been used since the 1950s!

https://en.m.wikipedia.org/wiki/Project_Orion_(nuclear_propu...

https://en.wikipedia.org/wiki/Interstellar_ark

Arguably if you launched the project Orion interstellar ark from the ground you could have pulled the world ending at the same time as well, perfect tripple combo. ;-)

Talk about putting all your eggs in one basket and then killing the hen as well.

This doesn't sound true given what we know about asymmetric warfare in general. What if we discovered the object really was an artillery shell sent to destroy us, but the civilization at the other end only has the resources to fire one every ten years with an accuracy of 1% to hit the Earth?

We might be like a primitive tribe facing an attacker with battleships - a technology that might as well be magic, but still one we can adapt to by abandoning the seafront village and retreating into the jungle.

>We might be like a primitive tribe facing an attacker with battleships

The same is true for them. For every strength there's bigger strength.

Exactly. The guys with spears and bows can't defeat the battleship, but if they hide out in the jungle long enough, maybe someone else will come along to sink it.

And they are too retarded to figure out as much?

> our current level of technology is already adequate to obliterate all life on the surface of the Earth

FWIW, and reinforcing your point, this is not even remotely true. Humans lack the technology now or in the foreseeable future to destroy the Earth’s biosphere, which would likely require boiling the oceans. There’s a reason we use that as an example of an impossibly large task.

I purposely excluded the oceans and caves when I said that, but we've overbuilt nuclear weapons to such an absurd degree that we can render the land highly irradiated and inhospitable.

> The rocket equation is a harsh mistress.

Nice Heinlein reference

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