Moontanman

Not if they were a million years apart in time, there are, estimate, 500 billion stars in the milky way, if one in a million have an advanced civilization then 500,000 of them exist but divide that by the age of the galaxy, I'm not sure what that is but let's just say a ballpark figure of 10 billion years. If an advanced technological civilization lasts 10,000 years then they could be a million years apart from each other in time. https://en.wikipedia.org/wiki/Fermi_paradox Military radar is both high powered and directional, radio leakage is not. One short message directed at the magellanic clouds is hardly a concentrated effort to draw attention to ourselves... There are Military drones that can take off and land autonomously and autonomous cars already exist as well as tractor trailers.

If the ancient aliens claims drive you nuts then this might be for you!

They avoid gravity wells... Actually you have to assert that aliens want to come here before you can say anything. Time is also a factor, do alien civilizations last forever? Ours has lasted a few thousand years so far, time is as big a factor if not larger than space. There could have been a million civilizations in the Milky Way so far and they could be separated by not just thousands of light years but thousands of years as well. I am of the "opinion" that planets would be avoided due to the fact that life has adapted to the earth, finding an earth like planet is no guarantee that we could live there. In fact slight variations in chemicals could make a planet uninhabitable to us even though the life that has adapted to it is prolific. It makes much more sense to build your own worlds than to try and find a world that happens to be perfect for you. Some alien specialist might be interested in us for various reasons but landing on the white house lawn would destroy the study. There is no reason to think that aliens would want to contact us and the idea that we could simply see them through their radio "leakage" is false. It's doubtful that we could detect a civilization identical to us at Alpha Centauri unless they were specifically pointing a high powered transmitter directly at us. Our radio leakage fizzles out within a light year or so due to the interstellar medium. Military type radar would be an exception but it would unlikely be a repeating signal and we have detected such signals from various places in our galaxy but they are not given weight because they do not repeat. I think we don't see aliens because that is exactly what we would expect to see unless they are intentionally signaling us and we do not do that, why should they?

Self driving cars are already a thing, why not self flying cars?

Fusion is the only technology required for star travel via McKendrick type artificial worlds that don't already possess. Developing the technology to build such worlds may not be easy but the engineering has been worked out. Distance is not a limiting factor given fusion, when you can build worlds supporting many thousands of people miles long and wide encased in the debris left over from their making from asteroids the idea of a destination becomes close to meaningless. Yes i am speculating but I am not speculating about things that are in violation of what we know to be possible. No FTL, no force fields, no Clark Tech, just fusion. If we can't control fusion then we might be limited to building a Dyson swarm around our current fusion power source but even that means many thousands of times the surface area of the Earth and there are other possibilities for star travel like probes humans are stored electronically and reproduction occurs after the space craft gets there. Maybe hundreds of thousands of years after launch. Flying cars suffer from a lack of an energy source, nothing more.

I think I am making a point you refuse to consider, technology marches on, I have suggested nothing that requires new physics yet you continue to dismiss the possibilities based on what we can currently do much like the quote I gave.

People who think Mars is a great place to colonise should spend a year in Antarctica, Mars is far less hospitable, much harder to get to, and out of range of any possible timely help... Antarctica is a paradise compared to Mars but you don't see lines forming to homestead Antarctica... Earth at the orbit of Venus would be somewhat warmer, probably too warm to maintain Earth like conditions. Venus receives twice as much energy from the sun as the earth does and it is thought that oceans would begin to evaporate and a runaway greenhouse would ensue. As recently, according to some sources, as 2 billion years ago Venus might have had earth like conditions even with oceans and life but the sun is steadily getting warmer and will eventually do to the Earth what it did to Venus. For a while...

Ok you win, man will never reach the moon because we can't jump high enough...

Jupiter is not a stop over for interstellar travel, Jupiter is in fact a site for manufacturing habitats. The moons and Lagrange points of Jupiter contain all the materials necessary to build habitats. This would be the starting point for colonization of the solar system which would eventually lead to things like a Dyson swarm, and colonization of the Kuiper belt and the Oort cloud. A these habitats would be the next step for moving on out, it might take centuries to develop the technology to build habitats and set up laser highways and or stations to accelerate volatiles and other supplies to traveling habitats but the possibilities are not limited to stopping for gas...

The relevance is that no one is saying we will build a star ship in earth orbit and take off for the nearest earth like planet. It's like expecting European humans who were building log rafts to suddenly build 747's and fly to north america. We will build movable habitats for centuries all over the solar system before we even think of the oort cloud. The idea of a generational ship is not impossible and if you are taking your home with you stopping at some point to build more habitats is hardly stopping for gas in fact gas and dust could be harvested with out stopping and going from our Oort cloud to the next is not unreasonable. Why would you stop for gas at 0.01% of your trip? I don't get that.

Because you seem to be dismissing my assertions of the beginning taking place in the solar system... The silicone based life on a hot planet, organo-metallic based organisms might be more likely, but we know so little about what that might be like it's limitations are totally unknown..

So these things must start in interstellar space?

You keep assuming we are only talking about interstellar space. This would have to start inside the solar system, be perfected inside the solar system. In fact I would think millions of these things would be build inside the solar system for use inside the solar system before the tech developed to allow longer voyages. McKendree cylinders might be unproven but there is no reason to think they could not be built

If the point was colonization of space using the resources contained there there would be no destination. Your habitat would be your home and volatiles can be stored on board, even a smallish Mckendree cylinder of five miles long and one mile think would have nearly 8 square miles of living space, twice that if you could your counter rotating partner cylinder and no attempt at simply simply letting natural processes would be like the biosphere project. The biosphere project assumed no way to add outside materials and it was far too small. At first these habitats would stay inside the solar system near sources of raw materials but as technology advanced I would bet cylinders and even support tech would move out into interstellar space, using EM capaults to send volatiles to passing habitats. Any largish object would become a refueling station, repair, station and a place to make more habitats.

I gave a link to Mckendree Cylinders, lots of variations, take two counter rotating cylinders, energy via controlled fusion, make them 10 miles long 2 miles thick. rotate them within a non rotating metal scaffold, cover the scaffold with the construction debris. Things like rock, ice, regolith and minerals that contain other valuable materials. as thick or massive as you are willing to have if you have to slow down any acceleration you may have planned. You might decide to stay hear where your house was built, say Jupiter's lagrange points, but most would eventually decide to move out, very slowly at first, building up speed with gravitational assists when ever possible. A huge amount of fuel, hydrogen, can be stored in the construction debris layer as ices which would protect from small meters.Keep you speed low so that when you detect an object ahead you can decelerate to take on volatiles if needed but using this method you should be able to cary many times the mass of volatiles you would lose over the time it took to semi drift to the next oort cloud. The only analogy we might make it RV travel, taking your home with you, it might take a million years but eventually things like gas stations might pop up on widely separated objects and chucks of icies or other necessities could be EM accelerated to the speed of the space RV to be captured so they don't even have to slow down. https://en.wikipedia.org/wiki/Stanford_torus https://en.wikipedia.org/wiki/O'Neill_cylinder https://en.wikipedia.org/wiki/McKendree_cylinder https://en.wikipedia.org/wiki/Dyson_sphere#Dyson_swarm https://en.wikipedia.org/wiki/Space_habitat Best I could do on short notice, now I have go and pass some more kidney stones hallelujah!!!!!

https://phys.org/news/2018-08-oort-clouds-stars-visible-cosmic.html https://en.wikipedia.org/wiki/Interstellar_object http://www-ssg.sr.unh.edu/ism/what1.html A cursory look only found listings of objects like oumuamua and or gas and dust but I have recently seen estimates of smaller ice and rock objects occuring in interstellar space, enough to be useful but I can't find them right now. I am unable to be online for long due to heath problems. I'll continue to look for the specifics at later date or with draw my claim your call... You do realise you are quoting an average of gas not objects right? And the oort cloud extends almost a light year away from the sun at least? "your own little world" would be many miles long and miles wide, rotate for internal gravity and house thousands of people. The asteroids would be the construction materials along with trojan asteroids, kuiper belt objects and or oort cloud objects. I'm not saying it would be easy but the task is well within the realm of possibility. Engineering studies were done decades ago.

The situation is more akin to being able to refuel and build more boats as you go. Even tiny islands would be exploited to refuel, repair, and reproduce more boats. We used to think the asteroids were natural islands for resources of a kind but volatiles would be a problem now we know that asteroids contain volatiles. We used to think that metals were the limit but we now think that carbon fibers and such will be the majority of construction materials with metals having a much smaller role. We used to think that self contained habitats were a necessity but now we know that ices and other volatiles are available in space. Space is not empty, gas dust and even chucks exist in reasonable numbers even in interstellar space. It's not a matter of building a ship to travel to the new world, its a matter of colonizing the ocean by removing the raw materials we need form the water. Oort clouds extend far from a star and do not suddenly stop but slowly become the interstellar medium, which is not a vacuum but contains significant quantities of various materials from the size of dust grains to planetoids. The expansion would proceed from the asteroids to the kuiper belt to the oort cloud to oort to objects in the interstellar medium to other oort clouds and onward. Planets and deep gravity wells would be avoided for the most part. Single forays to the next star would be difficult to improbable but tiny steps out by millions of habitats would be inevitable... If no one had ever used iron ore to make cars how would you even know there is supporting evidence? he was as much as saying there are no raw materials and so it can't be done. Do I really have to demonstrate the existence of resources in space?

I suggest you do some research... Your assertion still sounds like someone standing on an iron ore deposit and says it's impossible to use it to make cars...

Depends on what you mean by full,a habitat the size of the ISS would have problems surviving the journey to Mars, a McKendree cylinder many miles long could exist for centuries if not millenia and chunks of icy rocks are not uncommon and dust could even be harvested... I am not talking about firing up a Mckendree cylinder and heading for the nearest star, the expansion would be slow, centered around our own star and thousands if not millions of habitats slowly expanding in all directions making use of materials we encountered to top up, store, and even build new habitats. It would take tens of thousands of years to make it to one star but the expansion would be in all directions eventually resulting in combined speeds greater than light as the bubble of humanity expanded...

Recent discoveries show space is full of the material we need to build, refuel, top up volatiles, and simply live in the depths of space. Space dust can be collected without ever slowing down if nothing else. Speeds would be slow but since you travel in your own little world that becomes irrelevant.

That is just technological development not a flaw. It's like saying the ISS defines how big a space habitat can be. Mckendree cylinders would solve the isolation aspect, it's just a matter of size.

The ability to survive depends on the ability to break the umbilical, space is full of the stuff we need to live...

The only current flaw I am aware of is our lack of controlled fusion. Can you point out a few more, I'd like to be less wrong if possible..

I am not suggesting any magical technology, and distance is meaningless if you live in a space habitat. I'm not sure what this has to do with star travel. Why? I would not suggest escaping to other planets, such an assertion is foolish. Not taking care of the Earth is foolish and short sighted in fact I see a time when the majority of humans live in space habitats and the earth is more of a nature reserve. No reason to go back yet? We put a lander on Titan using nothing but chemical rockets... I doubt you have a clue to what you are talking about. Yes and a famous scientist said we would never travel faster than 60mph blah blah blah... We already have, evidently just not fast enough for you...

Our galaxy is 150,000 lys plus across but size is not a valid argument, technology could eventually conquer the entire local cluster of galaxies given a few hundred million years. You seem to be using the word evidence in place of the word proof, no proof but a body if evidence does indeed exist from the first mars landing to the universe being filled with organics. Life uses resources, space is full of such resources, saying the effort to use them is greater than they would be worth is like saying digging iron to build cars makes it illogical to drive to a gas station to buy gas... The only thing scarier than finding out we are not alone is finding out we are alone... paraphrasing A.C. Clark... This makes no sense, sending out radio waves or lasers is so easy and cheap it could not impact our survival in any way and even if it did the sun is going to kill us in a few hundred million years if we don't move out into the galaxy... And BTW all the trilobites are dead, mostly because all they did was crawl along the bottom feeding on the mud... We currently are aware of several thousand planets within around 1000 light years of the earth, at least one planet in the habitable zone around the nearest star. I am not sure why you would assert the idea that another earth would have to be a billion light years from Earth... Our everyday radio emissions would not be detectable buy us at the distance of the nearest star. Intentional radio signals or military type radar would be but would not be repeatable and would therefore not be considered intelligent signals ny our own SETI program if we detected them. BTW we have detected such signals but since they didn't repeat... https://en.m.wikipedia.org/wiki/List_of_potentially_habitable_exoplanets https://en.wikipedia.org/wiki/List_of_nearest_terrestrial_exoplanet_candidates