> For a long time now, NASA rockets have been designed for space exploration purposes, not military purposes.
Doesn't matter. Those space exploration rockets aren't helping us to address a single pressing or practical problem here on Earth, and they won't in the foreseeable future either.
> Once we had relatively efficient ways to put objects into the orbit of our choice, we found more and more applications.
Putting Earth-serving and Earth-observing objects in orbit is great. But that's not space exploration. Sending probes beyond Earth, if it's not for detection of Earth-threatening objects, is of no use to us now nor will it be in the foreseeable future.
> We developed capabilities for scientific purposes, and these capabilities proved to be very useful in everyday life.
In fact none have, with respect to space exploration.
> If we hadn't indulged in space exploration, we wouldn't have had the ready-made ability to put up GPS satellites once we could build them.
Nonsense. All we needed for GPS were military rockets -- the same kind used to launch spy satellites.
> We've also learned a whole lot scientifically...
Nothing that we really needed to know now. None of it has helped us to address a single pressing or practical problem here on Earth, and none will do so in the foreseeable future either.
> What you are saying is that past space exploration efforts were good because you can see good results from them, and the current ones are wasteful since you lack imagination.
Incorrect. NO space exploration has been good. Again, space exploration means the exploration of space objects. The only exploration that mattered was the detection of Earth-threatening objects.
> There's no difference between gravitational waves and lasers as you explain them. Both were theorized and apparatus constructed.
That's correct. But the second was inherently useful due to its confirmation of properties of matter which we could exploit. The first is not such a device.
> The big difference is that lasers were created long enough ago that we've found very large numbers of useful purposes.
Incorrect. Lasers were known by scientists immediately to be useful and to provide promising capabilities. That's not the case with gravity wave detectors.
> There's no difference between gravitational wave detectors and Leyden jars as you describe. Neither was useful for any practical purpose.
Again incorrect. You don't seem to be reading my comments completely, so you're making me repeat them. Gravitational waves detectors detect things we cannot manipulate nor exploit for our benefit. Leyden jars did the opposite -- immediately.
> Both demonstrated properties of matter here on Earth.
Inaccurate. Gravity wave detectors demonstrate properties of matter here on Earth that we cannot exploit. Gravity is the weakest force in the universe.
> Scientists working on electricity early on didn't know that they could manipulate and exploit it for anything useful.
Incorrect. It was clear by making sparks that they could easily control something new. They could see that *immediately*. Sparks could start fires. They could make a frog's legs jump -- helping to understand physiology -- even pertaining to the human body. Gravity wave detectors cannot do any such thing.
> The big difference is that the Leyden jar era of electricity was a long time ago, and we've had lots of time to develop uses.
Incorrect. The uses for Leyden jars were immediate. Learn your history.
> So we shouldn't bother trying to understand anything about it then...
That's a straw man. No one is suggesting that "we shouldn't bother".
What I'm saying is we should postpone further study for the time being -- since knowing more than we already know now about gravity won't change what we can do here on Earth in the foreseeable future.
> Many breakthroughs in technology and medicine were discovered due to space research.
Inaccurate. None of those breakthroughs were discovered in space. All resulted from research to solve practical problems and we can keep doing that -- researching to solve practical problems -- without building, launching, and monitoring space exploring spacecraft and telescopes.
> For example, that microprocessor you are using in your computer and that is also used to accelerate cancer research? Developed for space exploration.
Incorrect. It was developed for many purposes, primarily military.
> You have just described all forms of basic research, not just gravity waves and space exploration.
Incorrect. Research using gravity waves and the exploration of space are exceptional. Neither can help us to address a single pressing or practical problem here on Earth in the foreseeable future -- due to certain realities of physics, technology, and common sense. That's not the case for most other fields of scientific research.
> There was no particular use for lasers when they were discovered...
Lasers were not "discovered". They were *theorized* and then later *realized* (built). Their development confirmed properties of matter here on Earth which scientists knew we could manipulate and exploit.
> There was no particular use for electricity when the Leyden jar was invented.
Incorrect. Both demonstrated properties of matter here on Earth which scientists knew we could manipulate and exploit.
> Now, as far as space exploration goes, we have solved some practical problems already, most obviously with communications and GPS satellites.
Those are not part of "space exploration" as the term is most often used and as I use it. Space exploration means exploring space objects and space phenomena -- not the setting up of Earth-observing and Earth-serving satellites, which address pressing and practical problems here on Earth.
>... it was space exploration that pushed development of rockets that could put something in geosynchronous orbit.
Incorrect. It was the addressing of practical problems (i.e. military applications) which pushed the development of rockets.
> GPS satellites are a combination of space exploration and development in other areas.
Incorrect. GPS satellites are the result of addressing practical problems -- mainly military.
> The problem with "for the foreseeable future" is that in many ways that's a pretty darn short time.
Inaccurate. The time involved depends on the subject. The foreseeable future for *fashion* is incredibly short, but for subjects like faster than light travel, we can see centuries ahead, if not millenia.
> I'm nearing retirement age, but "the foreseeable future" is still considerably shorter than my expected remaining lifespan.
Incorrect. The foreseeable future for many capabilities we can imagine (e.g. FTL travel, reaching the nearest star, teleportation) is many many times the lifespan of humans.
> And what exactly do you think it cost to send a half-dozen legions off to expand Rome's borders and who do you think actually benefited from it?
If it was paid for by public funds, and if the public didn't benefit, then the public would've been justified to protest it.
>... the aristocrat who was at the top got the state to fund their army and then kept the spoils for themselves. It was the very definition of using state funds for personal enrichment.
Then the public would've been justified to protest it.
We don't need to go to Mars to research and develop technologies.
> Except we won't, because there will be no profit-driven motive to develop many of them.
Quite the contrary. Practically any research and development which can help us to address pressing and practical problems here on Earth in the foreseeable future can be profited from. Basically every technology which is helping us today earns income for *someone*.
> The space program largely been driven to solve problems related to space travel but whose solutions turn out to have significant applications on Earth.
We don't need the space program for that. We can "solve problems" and provide "significant applications on Earth" by researching those problems here on Earth directly. That the space program succeeded in solving problems only shows that we can solve problems that we address. Let's address the right ones directly.
> You have no idea what it will or will not address.
Quite the contrary, but you'd need a background in physics and technology, and experience, to understand that observing gravity waves and conducting space exploration in general cannot help us to address a single pressing or practical problem here on Earth in the foreseeable future.
Since you don't have that required background, please refer us to a credible expert who could provide a plausible argument for the contrary in your place.
> When the first scientists were mucking around with electricity in the 18th century they were giving people shocks and making frogs legs jump. Within a hundred years they were rolling out the world's first global high speed communication's system.
Yes but, firstly, their work didn't cost hundreds of millions, or billions, in public funds. Secondly, their work was inherently promising since it was the study of materials and phenomena here on Earth that we could control, manipulate and exploit. It already made frogs legs jump. There were good chances that it could help address problems here on Earth. That's not the case with gravity waves or space exploration in general which we can't control or manipulate for use here on Earth.
> My research is in making better microscopes (to cure cancer and whatnot...) and I've been personally looking at some of the advances in interferometry that allowed LIGO to be built...
We didn't need to build LIGO at the expense of hundreds of millions of dollars in public funds, and to continue funding its operation, to make those "advances".
> Heaven forbid that we ever do anything that could be useful beyond today or tomorrow.
Inaccurate. Heaven forbid that we ever misallocate hundreds of millions of dollars, or billions, in public funds, to projects which cannot help us to address a single one of our pressing or practical problems here on Earth in the foreseeable future.
Small mistakes in allocation of public funds are understandable and to be expected. No need for heaven to forbid that.
> You think you know what we need. You're wrong. You don't.
On the contrary, I do know quite a few things that we need and I know that nothing we can observe in space, apart from Earth-thrreatening objects, can help us to address our pressing and practical problems here on Earth in the foreseeable future.
> You'd surely want to know all about gravity, then, wouldn't you?
No. We wouldn't be able to do anything about gravity in the foreseeable future anyway. Furthermore, we kinda need it.
What we need instead is *a cure* for cancer. *That's* a pressing problem and we should reallocate LIGO funds to *that* instead -- and to other pressing research projects.
On the contrary, it most certainly *does not* matter.
> If the alcubierre drive (aka "warp drive") is to ever become reality, we need to more fully understand how gravity works...
All in good time. There's no possibility of us developing such a drive in the foreseeable future and having such a drive would not help us to address a single pressing problem here on Earth in the foreseeable future anyway. That kind of research is premature and we should postpone it for now.
By postponing it, we get to better fund research to address our pressing problems here on Earth and we'll make faster progress on a warp drive, more cheaply, in the future due to better computers, better technology, and probably AI to assist us.
>... and then we need to develop a way to create and manipulate gravity waves and development of the sort of power sources required will likely take centuries.
Exactly. No point in pressing now when we have pressing problems to address and future technology will help us progress faster on warp drives in the future anyway.
> Otherwise, we're doomed to exinction if we keep thinking "well, we can't do anything practical with it now, so let's not bother."
Straw man. *No one* is thinking that way. What I'm saying is to *postpone* warp drive research for the time being.
> Had past generations held this mentality, we would not have computers, the automobile, central heating and HVAC, or even the electric light today.
Incorrect. All those developments came from research to address practical problems here on Earth. Your premise is a straw man anyway. No one has the "mentality" you claimed.
> Given your lack of appreciation for the whole point of pure science...
Given your lack of scientific and technical background, I'm not surprised you don't understand the exceptional situations where certain research *cannot* help us to address a single pressing or practical problem here on Earth in the foreseeable future.
> The current detectors are the most sensitive instruments ever developed by humanity, and in and of themselves mark a major leap forward in technical ability.
Doesn't matter. That's not the kind of "technical ability" nor the kind of instrument we need. It won't help us to address a single pressing or practical problem here on Earth in the foreseeable future.
Meanwhile, we need better microscopes to better study cells and the brain -- to help cure cancer and to help understand how the brain works. That's the instrumentation and the "technical ability" that we need and that can truly help us to address pressing and practical problems here on Earth in the foreseeable future -- for the good of humanity.
There are considerably fewer than 1 percent of the solar systems of the Milky Way within the distance implied by a response arriving to Earth within 1,500 years.
If those aliens were to respond as soon as they detected our signals, and if we were to detect their response exactly 1,500 years from now, then those aliens would be 790 light-years away. Our signals have already traveled 80 years outwards. In 710 more years they would reach those aliens. The return trip would take another 790 years making a total from today of 710 years + 790 years = 1500 years.
The Earth is about 26,000 light-years from the center of our galaxy. If we cut the Milky Way into pie slices, how *wide* would a slice have to be 26,000 light-years from the center to accommodate a sphere of 790 light-years? To simplify, let's consider that sphere to have a diameter of about 1600 light-years.
A circle around our galaxy 26,000 light-years from the center would have a circumference of about 160,000 light-years, so the Milky Way could be cut into *100 pie slices* wide enough 26,000 light-years from the center to accommodate a sphere having a diameter of 1600 light-years.
This also neglects all the solar systems in our slice which are less than 25,210 light-years from the center of the galaxy, and more than 26,790 light-years from the center of the galaxy. It also neglects all the solar systems in roughly the same zones in the other slices as well so, again, there are considerably fewer than 1 percent of the solar systems of the Milky Way within the distance implied by a response arriving to Earth within 1,500 years.
They are assuming those aliens would be 790 light-years away.
If those aliens were to respond as soon as they detected our signals, and if we were to detect their response exactly 1,500 years from now, then their distance from us would be 790 light-years. It works out as follows: our signals have already traveled 80 years outwards. In 710 more years they will reach those aliens -- making the outbound trip 790 years. The return trip would take 790 more years making a total from today of 710 years + 790 years = 1500 years.
> I think you overstate the practical value of past expansions...
Not really.
>... the places all but the most primitive stone age migrations entered were already occupied by someone else.
Doesn't matter. The explorers still set out for *practical purposes*.
> Most of Rome's territorial expansions were purely conquest for the benefit of its ruling class -- the subjugation of foreign peoples, expropriating their wealth and enslaving their populations.
Thus for *practical purposes*.
>... the Vikings for the most part were motivated solely for plunder...
They carried that out *for immediate practical purposes*.
>... with little practical benefit for their home countries and without any long-term settlement.
They carried out their raids for the *practical purpose* of plunder. The items plundered certainly benefited whomever financed/supported their raids.
> Travel to Mars is less about its immediate practical value and much more about its secondary value in learning what it takes to get there and explore.
That's a very weak justification for the spending of billions in public funds. We can get those very same kinds of benefits by addressing our pressing and practical problems right here on Earth.
> The secondary value of the technologies and know-how of making this work will produce profound benefits for things like sustainable energy and medicine here on Earth...
We don't need to go to Mars for that. We can simply research and develop those technologies right here on Earth.
> To me, the ovious road to success looks like this...
"Success" for public funding should be defined as *progress in addressing our pressing and practical problems here on Earth in the foreseeable future*.
By this measure no mission to Mars in the foreseeable future would represent "success" for public funding.
>... humans have been doing it for millennia... It's part of what makes us human.
Nonsense. All those past explorations were for practical purposes -- to own land, to find new trades routes, etc.
Going to Mars at this time in our history would serve absolutely no practical purpose for humanity whatsoever. It would not help us to address a single pressing or practical problem here on Earth in the foreseeable future. Such missions should not be publicly funded at this time (Musk and SpaceX would not be paying for this mission out of their pockets).
Public funds should instead be spent to help address our pressing and practical problems here on Earth in the foreseeable future.
When public funds are concerned (Musk and SpaceX won't be paying a Mars mission out of their pockets), pushing "forward" should mean funding work and research that will help us to address our pressing and practical problems here on Earth instead.
> Finally someone is going to push us off this rock.
What do you mean "us"? The near-totality of "us" (over 7 billion of "us") will be staying right here on Earth for all of the foreseeable future.
> We stopped space exploration in the 1970s and never really returned.
Nonsense. Probes and rovers *continued* "space exploration" since then.
> It's about time to start doing amazing things again.
Nonsense. It's about time we invested *those* public funds to help address our pressing and practical problems right here on Earth instead.
>... the possible sacrifice for pushing our species forward.
"Pushing our species forward"? What the hell does *that* mean? Which way is forward? Was developing the Internet going forward? Would curing cancer be going forward?
Slashdot Mirror
> For a long time now, NASA rockets have been designed for space exploration purposes, not military purposes.
Doesn't matter. Those space exploration rockets aren't helping us to address a single pressing or practical problem here on Earth, and they won't in the foreseeable future either.
> Once we had relatively efficient ways to put objects into the orbit of our choice, we found more and more applications.
Putting Earth-serving and Earth-observing objects in orbit is great. But that's not space exploration. Sending probes beyond Earth, if it's not for detection of Earth-threatening objects, is of no use to us now nor will it be in the foreseeable future.
> We developed capabilities for scientific purposes, and these capabilities proved to be very useful in everyday life.
In fact none have, with respect to space exploration.
> If we hadn't indulged in space exploration, we wouldn't have had the ready-made ability to put up GPS satellites once we could build them.
Nonsense. All we needed for GPS were military rockets -- the same kind used to launch spy satellites.
> We've also learned a whole lot scientifically ...
Nothing that we really needed to know now. None of it has helped us to address a single pressing or practical problem here on Earth, and none will do so in the foreseeable future either.
> What you are saying is that past space exploration efforts were good because you can see good results from them, and the current ones are wasteful since you lack imagination.
Incorrect. NO space exploration has been good. Again, space exploration means the exploration of space objects. The only exploration that mattered was the detection of Earth-threatening objects.
> There's no difference between gravitational waves and lasers as you explain them. Both were theorized and apparatus constructed.
That's correct. But the second was inherently useful due to its confirmation of properties of matter which we could exploit. The first is not such a device.
> The big difference is that lasers were created long enough ago that we've found very large numbers of useful purposes.
Incorrect. Lasers were known by scientists immediately to be useful and to provide promising capabilities. That's not the case with gravity wave detectors.
> There's no difference between gravitational wave detectors and Leyden jars as you describe. Neither was useful for any practical purpose.
Again incorrect. You don't seem to be reading my comments completely, so you're making me repeat them. Gravitational waves detectors detect things we cannot manipulate nor exploit for our benefit. Leyden jars did the opposite -- immediately.
> Both demonstrated properties of matter here on Earth.
Inaccurate. Gravity wave detectors demonstrate properties of matter here on Earth that we cannot exploit. Gravity is the weakest force in the universe.
> Scientists working on electricity early on didn't know that they could manipulate and exploit it for anything useful.
Incorrect. It was clear by making sparks that they could easily control something new. They could see that *immediately*. Sparks could start fires. They could make a frog's legs jump -- helping to understand physiology -- even pertaining to the human body. Gravity wave detectors cannot do any such thing.
> The big difference is that the Leyden jar era of electricity was a long time ago, and we've had lots of time to develop uses.
Incorrect. The uses for Leyden jars were immediate. Learn your history.
> So we shouldn't bother trying to understand anything about it then ...
That's a straw man. No one is suggesting that "we shouldn't bother".
What I'm saying is we should postpone further study for the time being -- since knowing more than we already know now about gravity won't change what we can do here on Earth in the foreseeable future.
> Many breakthroughs in technology and medicine were discovered due to space research.
Inaccurate. None of those breakthroughs were discovered in space. All resulted from research to solve practical problems and we can keep doing that -- researching to solve practical problems -- without building, launching, and monitoring space exploring spacecraft and telescopes.
> For example, that microprocessor you are using in your computer and that is also used to accelerate cancer research? Developed for space exploration.
Incorrect. It was developed for many purposes, primarily military.
> You have just described all forms of basic research, not just gravity waves and space exploration.
Incorrect. Research using gravity waves and the exploration of space are exceptional. Neither can help us to address a single pressing or practical problem here on Earth in the foreseeable future -- due to certain realities of physics, technology, and common sense. That's not the case for most other fields of scientific research.
> There was no particular use for lasers when they were discovered ...
Lasers were not "discovered". They were *theorized* and then later *realized* (built). Their development confirmed properties of matter here on Earth which scientists knew we could manipulate and exploit.
> There was no particular use for electricity when the Leyden jar was invented.
Incorrect. Both demonstrated properties of matter here on Earth which scientists knew we could manipulate and exploit.
> Now, as far as space exploration goes, we have solved some practical problems already, most obviously with communications and GPS satellites.
Those are not part of "space exploration" as the term is most often used and as I use it. Space exploration means exploring space objects and space phenomena -- not the setting up of Earth-observing and Earth-serving satellites, which address pressing and practical problems here on Earth.
> ... it was space exploration that pushed development of rockets that could put something in geosynchronous orbit.
Incorrect. It was the addressing of practical problems (i.e. military applications) which pushed the development of rockets.
> GPS satellites are a combination of space exploration and development in other areas.
Incorrect. GPS satellites are the result of addressing practical problems -- mainly military.
> The problem with "for the foreseeable future" is that in many ways that's a pretty darn short time.
Inaccurate. The time involved depends on the subject. The foreseeable future for *fashion* is incredibly short, but for subjects like faster than light travel, we can see centuries ahead, if not millenia.
> I'm nearing retirement age, but "the foreseeable future" is still considerably shorter than my expected remaining lifespan.
Incorrect. The foreseeable future for many capabilities we can imagine (e.g. FTL travel, reaching the nearest star, teleportation) is many many times the lifespan of humans.
> And what exactly do you think it cost to send a half-dozen legions off to expand Rome's borders and who do you think actually benefited from it?
If it was paid for by public funds, and if the public didn't benefit, then the public would've been justified to protest it.
> ... the aristocrat who was at the top got the state to fund their army and then kept the spoils for themselves. It was the very definition of using state funds for personal enrichment.
Then the public would've been justified to protest it.
We don't need to go to Mars to research and develop technologies.
> Except we won't, because there will be no profit-driven motive to develop many of them.
Quite the contrary. Practically any research and development which can help us to address pressing and practical problems here on Earth in the foreseeable future can be profited from. Basically every technology which is helping us today earns income for *someone*.
> The space program largely been driven to solve problems related to space travel but whose solutions turn out to have significant applications on Earth.
We don't need the space program for that. We can "solve problems" and provide "significant applications on Earth" by researching those problems here on Earth directly. That the space program succeeded in solving problems only shows that we can solve problems that we address. Let's address the right ones directly.
> You have no idea what it will or will not address.
Quite the contrary, but you'd need a background in physics and technology, and experience, to understand that observing gravity waves and conducting space exploration in general cannot help us to address a single pressing or practical problem here on Earth in the foreseeable future.
Since you don't have that required background, please refer us to a credible expert who could provide a plausible argument for the contrary in your place.
> When the first scientists were mucking around with electricity in the 18th century they were giving people shocks and making frogs legs jump. Within a hundred years they were rolling out the world's first global high speed communication's system.
Yes but, firstly, their work didn't cost hundreds of millions, or billions, in public funds. Secondly, their work was inherently promising since it was the study of materials and phenomena here on Earth that we could control, manipulate and exploit. It already made frogs legs jump. There were good chances that it could help address problems here on Earth. That's not the case with gravity waves or space exploration in general which we can't control or manipulate for use here on Earth.
Photons have no rest mass.They do exhibit mass when travelling.
> My research is in making better microscopes (to cure cancer and whatnot...) and I've been personally looking at some of the advances in interferometry that allowed LIGO to be built ...
We didn't need to build LIGO at the expense of hundreds of millions of dollars in public funds, and to continue funding its operation, to make those "advances".
> Heaven forbid that we ever do anything that could be useful beyond today or tomorrow.
Inaccurate. Heaven forbid that we ever misallocate hundreds of millions of dollars, or billions, in public funds, to projects which cannot help us to address a single one of our pressing or practical problems here on Earth in the foreseeable future.
Small mistakes in allocation of public funds are understandable and to be expected. No need for heaven to forbid that.
> You think you know what we need. You're wrong. You don't.
On the contrary, I do know quite a few things that we need and I know that nothing we can observe in space, apart from Earth-thrreatening objects, can help us to address our pressing and practical problems here on Earth in the foreseeable future.
> Hey dickhead ...
I don't think so.
> ... what if gravity causes cancer?
That would suck.
> You'd surely want to know all about gravity, then, wouldn't you?
No. We wouldn't be able to do anything about gravity in the foreseeable future anyway. Furthermore, we kinda need it.
What we need instead is *a cure* for cancer. *That's* a pressing problem and we should reallocate LIGO funds to *that* instead -- and to other pressing research projects.
> It most certainly does matter.
On the contrary, it most certainly *does not* matter.
> If the alcubierre drive (aka "warp drive") is to ever become reality, we need to more fully understand how gravity works ...
All in good time. There's no possibility of us developing such a drive in the foreseeable future and having such a drive would not help us to address a single pressing problem here on Earth in the foreseeable future anyway. That kind of research is premature and we should postpone it for now.
By postponing it, we get to better fund research to address our pressing problems here on Earth and we'll make faster progress on a warp drive, more cheaply, in the future due to better computers, better technology, and probably AI to assist us.
> ... and then we need to develop a way to create and manipulate gravity waves and development of the sort of power sources required will likely take centuries.
Exactly. No point in pressing now when we have pressing problems to address and future technology will help us progress faster on warp drives in the future anyway.
> Otherwise, we're doomed to exinction if we keep thinking "well, we can't do anything practical with it now, so let's not bother."
Straw man. *No one* is thinking that way. What I'm saying is to *postpone* warp drive research for the time being.
> Had past generations held this mentality, we would not have computers, the automobile, central heating and HVAC, or even the electric light today.
Incorrect. All those developments came from research to address practical problems here on Earth. Your premise is a straw man anyway. No one has the "mentality" you claimed.
> Given your lack of appreciation for the whole point of pure science ...
Given your lack of scientific and technical background, I'm not surprised you don't understand the exceptional situations where certain research *cannot* help us to address a single pressing or practical problem here on Earth in the foreseeable future.
> The current detectors are the most sensitive instruments ever developed by humanity, and in and of themselves mark a major leap forward in technical ability.
Doesn't matter. That's not the kind of "technical ability" nor the kind of instrument we need. It won't help us to address a single pressing or practical problem here on Earth in the foreseeable future.
Meanwhile, we need better microscopes to better study cells and the brain -- to help cure cancer and to help understand how the brain works. That's the instrumentation and the "technical ability" that we need and that can truly help us to address pressing and practical problems here on Earth in the foreseeable future -- for the good of humanity.
There are considerably fewer than 1 percent of the solar systems of the Milky Way within the distance implied by a response arriving to Earth within 1,500 years.
If those aliens were to respond as soon as they detected our signals, and if we were to detect their response exactly 1,500 years from now, then those aliens would be 790 light-years away. Our signals have already traveled 80 years outwards. In 710 more years they would reach those aliens. The return trip would take another 790 years making a total from today of 710 years + 790 years = 1500 years.
The Earth is about 26,000 light-years from the center of our galaxy. If we cut the Milky Way into pie slices, how *wide* would a slice have to be 26,000 light-years from the center to accommodate a sphere of 790 light-years? To simplify, let's consider that sphere to have a diameter of about 1600 light-years.
A circle around our galaxy 26,000 light-years from the center would have a circumference of about 160,000 light-years, so the Milky Way could be cut into *100 pie slices* wide enough 26,000 light-years from the center to accommodate a sphere having a diameter of 1600 light-years.
This also neglects all the solar systems in our slice which are less than 25,210 light-years from the center of the galaxy, and more than 26,790 light-years from the center of the galaxy. It also neglects all the solar systems in roughly the same zones in the other slices as well so, again, there are considerably fewer than 1 percent of the solar systems of the Milky Way within the distance implied by a response arriving to Earth within 1,500 years.
They are assuming those aliens would be 790 light-years away.
If those aliens were to respond as soon as they detected our signals, and if we were to detect their response exactly 1,500 years from now, then their distance from us would be 790 light-years. It works out as follows: our signals have already traveled 80 years outwards. In 710 more years they will reach those aliens -- making the outbound trip 790 years. The return trip would take 790 more years making a total from today of 710 years + 790 years = 1500 years.
> I think you overstate the practical value of past expansions ...
Not really.
> ... the places all but the most primitive stone age migrations entered were already occupied by someone else.
Doesn't matter. The explorers still set out for *practical purposes*.
> Most of Rome's territorial expansions were purely conquest for the benefit of its ruling class -- the subjugation of foreign peoples, expropriating their wealth and enslaving their populations.
Thus for *practical purposes*.
> ... the Vikings for the most part were motivated solely for plunder ...
They carried that out *for immediate practical purposes*.
> ... with little practical benefit for their home countries and without any long-term settlement.
They carried out their raids for the *practical purpose* of plunder. The items plundered certainly benefited whomever financed/supported their raids.
> Travel to Mars is less about its immediate practical value and much more about its secondary value in learning what it takes to get there and explore.
That's a very weak justification for the spending of billions in public funds. We can get those very same kinds of benefits by addressing our pressing and practical problems right here on Earth.
> The secondary value of the technologies and know-how of making this work will produce profound benefits for things like sustainable energy and medicine here on Earth ...
We don't need to go to Mars for that. We can simply research and develop those technologies right here on Earth.
> To me, the ovious road to success looks like this ...
"Success" for public funding should be defined as *progress in addressing our pressing and practical problems here on Earth in the foreseeable future*.
By this measure no mission to Mars in the foreseeable future would represent "success" for public funding.
> ... humans have been doing it for millennia ... It's part of what makes us human.
Nonsense. All those past explorations were for practical purposes -- to own land, to find new trades routes, etc.
Going to Mars at this time in our history would serve absolutely no practical purpose for humanity whatsoever. It would not help us to address a single pressing or practical problem here on Earth in the foreseeable future. Such missions should not be publicly funded at this time (Musk and SpaceX would not be paying for this mission out of their pockets).
Public funds should instead be spent to help address our pressing and practical problems here on Earth in the foreseeable future.
When public funds are concerned (Musk and SpaceX won't be paying a Mars mission out of their pockets), pushing "forward" should mean funding work and research that will help us to address our pressing and practical problems here on Earth instead.
> Finally someone is going to push us off this rock.
What do you mean "us"? The near-totality of "us" (over 7 billion of "us") will be staying right here on Earth for all of the foreseeable future.
> We stopped space exploration in the 1970s and never really returned.
Nonsense. Probes and rovers *continued* "space exploration" since then.
> It's about time to start doing amazing things again.
Nonsense. It's about time we invested *those* public funds to help address our pressing and practical problems right here on Earth instead.
> ... the possible sacrifice for pushing our species forward.
"Pushing our species forward"? What the hell does *that* mean? Which way is forward? Was developing the Internet going forward? Would curing cancer be going forward?
> Public funds can only be used for the public good.
Yep
> How about "war"? That's for the public good?
If not, we should protest that use of public funds too.
> What public good were roads developed for?
You're asking that seriously?