Metaphysics vs. Atheism

[King of the Americas]

*Warning this thread contains woo woo garb.

Last night on "30 Days", the show plotted an atheist in the home of staunch christians.

The show had none of the Jerry Springer-type outbreaks with one side throwing stuff or yelling at the other, but I did have hope when the atheist attended a bible study.

I couldn't help but keep thinking, maybe both of these people are wrong...

I take a Von Daniken/Hancock point of view, wherein I lack the metaphysical part of the equation. I believe the flood happened, except that I think it was a regional thing, as in the Epic of Gilgamesh. I don't believe in winged angels, but rather extra-terresterial piloted UFO's.

I like to refer to the bible as fictionalized facts...almost.

I can't swallow fanciful tales of omni-present god(s), but beings more evolved than us, playing super scientists by tagging and then releasing humans just to see what they do, sounds more than probable after watching a Discovery Channel special, and seeing humans doing the same thing to lesser evovled creatures.

Besides, I deem this view as THE compromise between the two vastly separated stances.

Any thoughts on the matter?

[Bikewer]

"Metaphysics" is sort of an abused term; in it's standard usage, "beyond physics", it refers to a sort of philosophical bent. "Why are we here", "what is a man", things of that nature.
Unfortunately, it's come to be a catch-all for all manner of new-agey, "spiritual", and woo-ish beliefs.

As to Aliens vs. God, or views influenced by the highly-discredited Mr. Von Danniken....
There is no more evidence for these things than there is for biblical miracles.

The bible stories (or any other scripture for that matter) may simply be seen as myths, enshrined in religion. Myths are common to all peoples on the face of the Earth, they are part and parcel of being human beings with the intellect to wonder why we are here.

[Filip Sandor]

"Metaphysics" is sort of an abused term; in it's standard usage, "beyond physics", it refers to a sort of philosophical bent. "Why are we here", "what is a man", things of that nature.
Unfortunately, it's come to be a catch-all for all manner of new-agey, "spiritual", and woo-ish beliefs.

As to Aliens vs. God, or views influenced by the highly-discredited Mr. Von Danniken....
There is no more evidence for these things than there is for biblical miracles.

The bible stories (or any other scripture for that matter) may simply be seen as myths, enshrined in religion. Myths are common to all peoples on the face of the Earth, they are part and parcel of being human beings with the intellect to wonder why we are here.

Yes Bikewer, I'm sure all the "credible" ex-military sources who spoke publicly on the Roswell incident were high-on acid when it happened.. and continue to be high on acid because they get paid to do it by secret organizations hoping to convince humanity that extra-terrestrial life is indeed real.

Are you saying we are the center of the Universe and that because you haven't seen a UFO or an alien, that the laws of physics which contribute to life somehow differ in different sections of our solar system/ galaxy/... and the billions of other galaxies?

[Dark Jaguar]

*Warning this thread contains woo woo garb.

Last night on "30 Days", the show plotted an atheist in the home of staunch christians.

The show had none of the Jerry Springer-type outbreaks with one side throwing stuff or yelling at the other, but I did have hope when the atheist attended a bible study.

I couldn't help but keep thinking, maybe both of these people are wrong...

I take a Von Daniken/Hancock point of view, wherein I lack the metaphysical part of the equation. I believe the flood happened, except that I think it was a regional thing, as in the Epic of Gilgamesh. I don't believe in winged angels, but rather extra-terresterial piloted UFO's.

I like to refer to the bible as fictionalized facts...almost.

I can't swallow fanciful tales of omni-present god(s), but beings more evolved than us, playing super scientists by tagging and then releasing humans just to see what they do, sounds more than probable after watching a Discovery Channel special, and seeing humans doing the same thing to lesser evovled creatures.

Besides, I deem this view as THE compromise between the two vastly separated stances.

Any thoughts on the matter?

Sure, considering that long long ago during my first forray into spiritualism, that was more or less my view on things. Basically I didn't want to rule out anything so I tried weaving it all into a rich tapestry of "it's all true". Unfortunatly eventually I realized I was just coming up with a comic book story. Too bad that itself wasn't enough to get me out of such things, but eventually I'd leave it all behind.

Anyway, the main problem is that your "compromise" between the two positions doens't really compromise. The hardcore faithful will see it as "the same" as any other view, including atheism, in that it doesn't agree with their faith. The atheists, well it depends on who you are dealing with I suppose. One can not believe in any god and still be a very silly sort of person after all. A skeptical sort is likely to be an atheist, but one can easily be an atheist for all the wrong reasons. I like this joke about inmates in an asylum plotting an escape as it illustrates it nicely:

"I can use this flashlight to make a beam of light and you can walk on it over the wall to freedom."

"That's insane. You'll just turn it off when I'm halfway there and I'll fall to my death!"

My main issue with your position is basically, why do you believe those events happened to begin with? There's really no point in trying to come up with an explanation for a phenomenon unless you know that particular thing is actually true to begin with.

If you have no reason to believe in all those fairy tale aspects, what makes you think the red sea actually divided at all, even if it was some natural event that is allowed by current science? What makes you think that the jews actually were kept as slaves in egypt and that some strange objects actually were flying around and were spotted?

Further, what makes you think these particular explanations are the correct ones anyway? I've heard the "those angels were aliens" explanation since I was a kid. Makes for good sci-fi but even if the guy did see something, what makes you think it was some alien space ship?

That's the reason skeptical sorts go atheist to begin with. They see no reason to believe a proposition, so they don't. It's not about a comrpomise of two beliefs held on equal footing, because they aren't. One agrees with the existing evidence, one does not.

This isn't to say there's anything wrong with your point of view if you decide you wish to believe it. I'm merely saying that it is pretty much in the same camp as any other religious belief. Says the skeptic; evidence?

(Those blasted semicolons, I usually abstain from them but allowed it in there for the sake of this joke. I never know exactly where they can be safely used...)

[Frostbite]

I read a bunch of books by the likes of Von Daniken, Sitchin, Hoagland and Hancock and, although there isn't definite proof to support their respective theories, I must admit I find the possibility absolutely mind-blowing.

I mean, we're only a few hundred years short of exploring other star systems, let alone colonizing other planets and tampering with whatever lifeforms we'll find there. What's to keep us from domesticating and/or genetically engineering certain species to our will, to perform whatever functions we want them to?

The universe is overwhelmingly huge. I find it plausible that there might be billions of civilizations out there, that some of them might have visited us in the past, and that some of those might have inferred with our cultural and/or biological development. I also find it plausible that, as a moderately advanced civilization, we might have been flagged as a potential member in some sort of galactic community and that, eventually, when we are ready, we'll be able to join it, and in the meantime we have been quarantined, only to be visited by occasional surveyors.

Now concerning mythological and biblical events, I see them simply as actual historical events which have been grossly misinterpreted, mistranslated and exaggerated for thousands of years. There probably wasn't a Flood per se, but perhaps a pretty dramatic increase in sea levels (1 to 10 meters) due to melting polar ice caps, for instance, and, since most ancient civilizations started near shores and rivers, they all felt it at pretty much the same time.

[joller]

I mean, we're only a few hundred years short of exploring other star systems,
Oh yeah? Who told you that?
So what's your idea for defeating the problem with the speed of light?

let alone colonizing other planets and tampering with whatever lifeforms we'll find there.
What life forms? We haven't found a proof of anything like that.

What's to keep us from domesticating and/or genetically engineering certain species to our will, to perform whatever functions we want them to?
the fact that currently there's no proof they even exist?

[Oldpossum]

[QUOTE=King of the Americas;1835489
I can't swallow fanciful tales of omni-present god(s), but beings more evolved than us, playing super scientists by tagging and then releasing humans just to see what they do, sounds more than probable after watching a Discovery Channel special, and seeing humans doing the same thing to lesser evovled creatures.[/QUOTE]

Just to be pedantic, you understand, what lesser evolved creatures would these be?:confused:
It's just if some scientist is hogging a hithero undiscovered cache of lesser evolved creatures, I'd like to have some to experiment on too!
Because as far as I was aware, every living thing on the planet, has been evolving for just as long as everything else has!:D

Also do you have any Hypothesis, as to why these greater evolved aliens, like to subject their research subjects to anal probes?;)

[Frostbite]

Oh yeah? Who told you that?
So what's your idea for defeating the problem with the speed of light?


What life forms? We haven't found a proof of anything like that.

the fact that currently there's no proof they even exist?

I'm obviously talking hypothetically. Guess I should've mentioned that for the ones who couldn't assume it.

[drkitten]

I'm obviously talking hypothetically.

What's the difference between "talking hypothetically" and "spewing unsupported nonsense"?

The problem with a statement like "we're only a few hundred years short of exploring other star systems" is that there's no reason at all (that I can see) to take such a prediction seriously. I've seen far too many similar predictions -- hell, this is 2006. We were supposed to have full human-level AI and manned flights to Jupiter five years ago -- and there are too many engineering problems (like the speed of light) that we don't even have an approach to solving.....

[Frostbite]

Ok then, a few thousand years. What's the difference?

Also, we could theoretically beat the speed of light using singularities and other means which are of course impossible to us with our current technologies.

[Hellbound]

Yes Bikewer, I'm sure all the "credible" ex-military sources who spoke publicly on the Roswell incident were high-on acid when it happened.. and continue to be high on acid because they get paid to do it by secret organizations hoping to convince humanity that extra-terrestrial life is indeed real.

Are you saying we are the center of the Universe and that because you haven't seen a UFO or an alien, that the laws of physics which contribute to life somehow differ in different sections of our solar system/ galaxy/... and the billions of other galaxies?

And just because a few fame-seekers (none of which, to my knowledge, can show they were even involved in the Roswell events beyond their own say-so) say these things, this negates all the laws of physics that explain exactly how much it would cost (in terms of energy and time) for an extra-terrestrial to reach Earth, even from the nearest star (which, as a trinary, is unlikely to have a stable planetary system capable of supporting life)?

Extra-terrestrial life is possible, and I believe it to be highly likely. Extra-terrestrial intelligence, less likely , but I expect it exists. ETs visiting Earth in flying saucers? Pull the other one...

[Overman]

Physics, and the athiesm that goes along with it, has a labortory and can be tested.

Metaphysics, has no lab, and cannot.

[drkitten]

Ok then, a few thousand years. What's the difference?

None whatsoever. It's still wildly and irresponsibly speculative.



Also, we could theoretically beat the speed of light using singularities and other means which are of course impossible to us with our current technologies.

Really? Every "theory" for beating the speed of light that I've seen postulates either "exotic matter" (which has never been observed in the universe) or "white holes" (which have also never been observed in the universe.)

Why not simply assume that fairies can pilot unicorns faster than light speed and be done with it?

[Hellbound]

Drkitten got to it before I did.

The FTL theories out so far all rely on the existence of objects whose properties are assigned, basically, to specifically allow for time travel. None have any evidence of existence.

[Frostbite]

None whatsoever. It's still wildly and irresponsibly speculative.




Really? Every "theory" for beating the speed of light that I've seen postulates either "exotic matter" (which has never been observed in the universe) or "white holes" (which have also never been observed in the universe.)

Why not simply assume that fairies can pilot unicorns faster than light speed and be done with it?

Ok you win. This is my last post on these extremely boring boards. Have a nice life.

[Dave1001]

Besides, I deem this view as THE compromise between the two vastly separated stances.

Any thoughts on the matter?

That's an interesting approach to ascertaining reality.

[Dave1001]

What's the difference between "talking hypothetically" and "spewing unsupported nonsense"?

The problem with a statement like "we're only a few hundred years short of exploring other star systems" is that there's no reason at all (that I can see) to take such a prediction seriously. I've seen far too many similar predictions -- hell, this is 2006. We were supposed to have full human-level AI and manned flights to Jupiter five years ago -- and there are too many engineering problems (like the speed of light) that we don't even have an approach to solving.....

The speed of light isn't going to keep us from exploring other star systems a few hundred years from now. Aren't the nearest starsystems only light-decades away? It seems to be a reasonably plausible prediction to me.

[Dave1001]

Physics, and the athiesm that goes along with it, has a labortory and can be tested.

Metaphysics, has no lab, and cannot.

I don't think atheism can be falsified in a lab.

[Dave1001]

I'm obviously talking hypothetically. Guess I should've mentioned that for the ones who couldn't assume it.

Unfortunately, some folks here think an intelligent reply is pointing out that you haven't included dozens of lengthly footnotes with your post.

[Bikewer]

"Are you saying we are the center of the Universe and that because you haven't seen a UFO or an alien, that the laws of physics which contribute to life somehow differ in different sections of our solar system/ galaxy/... and the billions of other galaxies?"

I don't believe I said anything of the sort. I noted that the evidence for alien visitation was as lacking as any evidence for biblical miracles.
As for Roswell...Perhaps a scan-through of the excellent series of articles that appeared in Skeptical Inquirer over the last few years would be the best way to guage my opinion on that event.

I would note that the late Carl Sagan was a big believer in the possibility of intelligent alien life. He was one of the movers and shakers of the S.E.T.I. project.
He was also a member of a variety of blue-ribbon panels who examined the very best UFO "cases".
Sagan said flatly that there was not a shred of evidence to indicate that we had been visited by intelligent beings from another planet.

[Hellbound]

The speed of light isn't going to keep us from exploring other star systems a few hundred years from now. Aren't the nearest starsystems only light-decades away? It seems to be a reasonably plausible prediction to me.

There are over a hundred or so within, say, 20 light years radius (IIRC, been a while since I examined the data). The closest (Proxima Centauri) is about 4 light years.

[drkitten]

The speed of light isn't going to keep us from exploring other star systems a few hundred years from now.

Yes, it will. More accurately, the speed of light combined with the energy budget needed.

[Dave1001]

Yes, it will. More accurately, the speed of light combined with the energy budget needed.

Could you (or someone else) elaborate on that or us please? Why are we unlikely to be able to afford the energy costs of traveling to nearby star systems in the next few hundred years?

[Psiload]

Could you (or someone else) elaborate on that or us please? Why are we unlikely to be able to afford the energy costs of traveling to nearby star systems in the next few hundred years?

You'd need to travel very fast in order to get to even the nearest star system (4.3 light years away). Even travelling at the speed of light (a physical impossibility) it'd still take you 4.3 years to reach the nearest star system.

And this will give you some idea of the energy required to do even that...

http://en.wikipedia.org/wiki/Faster-than-light

-To accelerate an object of non-zero rest mass to c(the speed of light) would require infinite time with any finite acceleration, or infinite acceleration for a finite amount of time

-Either way, such acceleration requires infinite energy. Going beyond the speed of light in a homogeneous space would hence require more than infinite energy, which is not a sensible notion.
Are you getting the picture?

[Hellbound]

Psiload:

To be fair, I think we should take a more realistic scenario.

Let's assume it's a manned mission. Because of this, we'll make a few "design specifications" to our craft.

Maximum acceleration: 1G. We don't want to crush our astronauts or make them too uncomfortable during the trip.
Minimum Acceleration: .1G I can't recall, but I believe about this level is the minimum needed to prevent bone/joint deterioration. We want them to be physically able to explore, or simply walk when they return.

Size: This is difficult. Most hypothetical designs I've seen for actual interstellar craft weigh in about 10 tons (IIRC, this was for a very small crew). So we'll use that as our weight.

Distance: 4.3 light years.

Travel Characteristics: We can do three calculations. First, we'll see about accelerating halfway, then deccelerating the rest, at a minimal acceleration (say speed = .9c at the halfway point). Then, we'll see about full acceleration to halfway and full deccel to end (1G), again with a max cruising speed of .9c. Finally, we'll do a minimal expenditure calculation using our minimum acceleration (.1G) and see where that takes us.

I'll work on these figures, but if someone with more know-how wants to run with them to figure energy requirements, feel free. I have to look up some data and equations, so I might be a while.

[drkitten]

Could you (or someone else) elaborate on that or us please? Why are we unlikely to be able to afford the energy costs of traveling to nearby star systems in the next few hundred years?

Consider the energy costs of accelerating a 1kg object to 1% of light speed (which would be necessary, at a minimum, to get to a nearby star-system in the "next few hunded years." ) (I get about 4.5 times 10^12 joules.)

Assuming we use a perfectly-efficient pinpoint fusion reactor (which could get about 3x10^8 J out of a single kg of fuel), we'd still need to use 100kg of fuel to get that much energy. And we'd need to carry that much fuel with us in order to decelerate at the end, so we'd need 100 times as much fuel as payload, and we'd need fuel to move the fuel, and so forth.

And these calculations don't take into account reaction mass!

[Dave1001]

You'd need to travel very fast in order to get to even the nearest star system (4.3 light years away). Even travelling at the speed of light (a physical impossibility) it'd still take you 4.3 years to reach the nearest star system.

And this will give you some idea of the energy required to do even that...

http://en.wikipedia.org/wiki/Faster-than-light


Are you getting the picture?

Not yet, because I don't think anyone is positing that the exploring vessels would travel at or close to the speed of light.

Let's say the vessel to the nearest star system travels at 1/5 the speed of light. So that the trip each direction takes 21.5 years. What are the best estimations of the energy costs?

Of course, if we substantially increase human lifespan in the next several hundred years, longer voyages could be feasible. So how about the energy costs of going 1/40th the speed of light? The vessel might depart 100 years from now, and reach the nearest star system in 172 years (if my math is correct) -within our "several hundred year" timeline. Let's say it carries a minimal human crew: 1 or 2 passengers.

Finally, we could send nanorobotic craft, which I think would greatly reduce the fuel needs. But I don't think that's in the spirit of the original speculation that we'll be exploring nearby star systems in a few hundred years. I think he/she meant human exploration. Because technically we're exploring star systems now with telescopy.

[Dave1001]

Psiload:

To be fair, I think we should take a more realistic scenario.

Let's assume it's a manned mission. Because of this, we'll make a few "design specifications" to our craft.

Maximum acceleration: 1G. We don't want to crush our astronauts or make them too uncomfortable during the trip.
Minimum Acceleration: .1G I can't recall, but I believe about this level is the minimum needed to prevent bone/joint deterioration. We want them to be physically able to explore, or simply walk when they return.

Size: This is difficult. Most hypothetical designs I've seen for actual interstellar craft weigh in about 10 tons (IIRC, this was for a very small crew). So we'll use that as our weight.

Distance: 4.3 light years.

Travel Characteristics: We can do three calculations. First, we'll see about accelerating halfway, then deccelerating the rest, at a minimal acceleration (say speed = .9c at the halfway point). Then, we'll see about full acceleration to halfway and full deccel to end (1G), again with a max cruising speed of .9c. Finally, we'll do a minimal expenditure calculation using our minimum acceleration (.1G) and see where that takes us.

I'll work on these figures, but if someone with more know-how wants to run with them to figure energy requirements, feel free. I have to look up some data and equations, so I might be a while.

Thanks. Awesome. :D (full disclosure, I think this thought experiment has been done multiple times before, by Carl Sagan and within science fiction. But I'm still curious as to the best informed results of it).

[drkitten]

Travel Characteristics: We can do three calculations. First, we'll see about accelerating halfway, then deccelerating the rest, at a minimal acceleration (say speed = .9c at the halfway point). Then, we'll see about full acceleration to halfway and full deccel to end (1G), again with a max cruising speed of .9c. Finally, we'll do a minimal expenditure calculation using our minimum acceleration (.1G) and see where that takes us.

I don't think you need to do this much work. Just calculate the maximum speed the ship will hit in mid-flight, then use 1/2 m v^2 to figure out how much kinetic energy it would be packing at that point.

Using your numbers and a local envelope, I get a cruising speed of 270,000,000 m/sec and a mass of 10000kg, giving me 3.645 x 10^20 Joules. I don't know what you're planning on using for rocket fuel, but if it's something like hydrogen, that's "only" about 10^18kg of hydrogen. To put that in perspective, that's something like a hundredth of a percent of the mass of the moon.....

And then remember that the spacecraft not only has to gain that velocity, but it has to lose it as well at the end of the trip.

[Hellbound]

Oh, cool!

I found answers for my 1G acceleration speed. See here (http://math.ucr.edu/home/baez/physics/Relativity/SR/rocket.html).

To pull relevant portions:

The time for the trip with 1G accel is 3.6 years on-board the ship.
The fuel needed is 38kg per kg of payload (assuming 100% efficiency, all matter to energy). That's a significant amount of energy. Using E=mc2 it works out like so:

E=(38kg)*(300,000,000m/s)*(300,000,000m/s)
E=3,420,000,000,000,000,000kgm2/s2 with is Joules
So, that's 3,420 TJ of energy, per kg of our ship.

So for our 10 tons (about 9000kg), we'll need (9000*3,420) 30,780,000 TJ.

Now, from [url=http://energy.cr.usgs.gov/energy/stats_ctry/Stat1.html]the USGS[/url, the U.S produces 72.9 Quadrillion BTUs per year. That works out to 76,909,500 TJ (1055 Joules/BTU).

So, we're looking at about half of the energy production in the U.S. for an entire year, in order to get this thing to the nearest star. This does not include the return trip, either, so we'd have to double it.

[Jimbo07]

... Just calculate the maximum speed the ship will hit in mid-flight, then use 1/2 m v^2

...

Using your numbers and a local envelope, I get a cruising speed of 270,000,000 m/sec and a mass of 10000kg, giving me 3.645 x 10^20 Joules. I don't know what you're planning on using for rocket fuel, but if it's something like hydrogen, that's "only" about 10^18kg of hydrogen.


:confused:

Using Fusion (http://www.astronomy.ohio-state.edu/~ryden/ast162_4/notes15.html), I'll take 650 trillion Joules to mean 6.5x1014 J.

Choosing a 'cruise' velocity of 0.5c (which gives a reasonable time dilation), I get 0.5(1.5x108m/s)2(10000kg) = 1.125x1020 J. Dividing gives approx. 173,000 kg, or am I wrong?

[Hellbound]

I don't think you need to do this much work. Just calculate the maximum speed the ship will hit in mid-flight, then use 1/2 m v^2 to figure out how much kinetic energy it would be packing at that point.

Using your numbers and a local envelope, I get a cruising speed of 270,000,000 m/sec and a mass of 10000kg, giving me 3.645 x 10^20 Joules. I don't know what you're planning on using for rocket fuel, but if it's something like hydrogen, that's "only" about 10^18kg of hydrogen. To put that in perspective, that's something like a hundredth of a percent of the mass of the moon.....

And then remember that the spacecraft not only has to gain that velocity, but it has to lose it as well at the end of the trip.

Yeah, I was going to get to fuel later. And I was trying to consdier both acceleration and decceleration. Found a few figures that give numbers for to and from Proxima, so I posted that.

Also, don't forget that relativistic effects come into play, which was the part I was going to be looking up.

[Dave1001]

Oh, cool!

I found answers for my 1G acceleration speed. See here (http://math.ucr.edu/home/baez/physics/Relativity/SR/rocket.html).

To pull relevant portions:

The time for the trip with 1G accel is 3.6 years on-board the ship.
The fuel needed is 38kg per kg of payload (assuming 100% efficiency, all matter to energy). That's a signifigant amount of energy. Using E=mc2 it works out like so:

E=(38kg)*(300,000,000m/s)*(300,000,000m/s)
E=3,420,000,000,000,000,000kgm2/s2 with is Joules
So, that's 3,420 TJ of energy, per kg of rocket. That means that 1/11th of our ship is actual equipment, the rest fuel. So our payload is about 825 kg. THat means we need 2,821,500 TJ of energy.

From here (http://energy.cr.usgs.gov/energy/stats_ctry/Stat1.html) the annual energy production in the U.S. runs about 72.9 Quadrillion BTUs. That works out to 76,909,500,000,000,000,000 J, or 76,909,500 TJ.

So, that means we'd need about 3.6% of the energy produced by the U.S. to send four people to the next closest star. This also assumes a 100% matter-to-energy conversion fueling the process. The closest we could get to that would be matter-antimatter but even then some energy is lost in conversion. MOre relistically, I'd say we could get, at best, 50% from a matter/antimatter thermal system. That means about 7.2% of the U.S. energy production for one year.

Awesome. I don't have the time or energy to recreate your work and check your numbers (nor do I have the aptitude to do it quickly). But if those numbers and calculations hold up, it seems quite possible and achievable to do several hundred years from now. Even if our energy conversion ratio is significantly lower than 50% and more in the realm of the best energy conversion ratios we can achieve with today's technology.

In fact, your work seems to imply that we could send a human to the next closest star with today's technology, although it would require massive social investment. Are their any current technological barriers to prevent us from doing so?

Sidenote: I forgot about the difference between on board ship time and time on Earth, so I think my previous comments about human aging are pretty irrelevant.

[Hellbound]

Awesome. I don't have the time or energy to recreate your work and check your numbers (nor do I have the aptitude to do it quickly). But if those numbers and calculations hold up, it seems quite possible and achievable to do several hundred years from now. Even if our energy conversion ratio is significantly lower than 50% and more in the realm of the best energy conversion ratios we can achieve with today's technology.

In fact, your work seems to imply that we could send a human to the next closest star with today's technology, although it would require massive social investment. Are their any current technological barriers to prevent us from doing so?

Sidenote: I forgot about the difference between on board ship time and time on Earth, so I think my previous comments about human aging are pretty irrelevant.


Actually, I miscalculated, because the 10 ton figure for craft weight was for crew compartments and stores...otherwise, you have the weight equivalent of two people for your payload.

I've recalculated with the 10 ton figure as the payload weight, which is more reasonable. You need crew quarters, 8 years or so of food (or means to produce it artificially, still not cheap), water, medicines, exercise areas, etc.

[Dave1001]

To put that in perspective, that's something like a hundredth of a percent of the mass of the moon......

That sounds like a lot, but it may not be prohibitive. To continue the parallel example to the energy used by the U.S. each year, what percentage of the mass of the moon does the U.S. use in energy each year?

[Dave1001]

Actually, I miscalculated, because the 10 ton figure for craft weight was for crew compartments and stores...otherwise, you have the weight equivalent of two people for your payload.

I've recalculated with the 10 ton figure as the payload weight, which is more reasonable. You need crew quarters, 8 years or so of food (or means to produce it artificially, still not cheap), water, medicines, exercise areas, etc.

okay, looking forward to your fleshed out appraisal of these factors.

[drkitten]

Yeah, I was going to get to fuel later.

Fuel is the big killer, though.

The United States happily burns through zillions and zillions of Joules of energy each year, mostly by burning millions of tonnes of fuel from a huge geological tank that's been accumulating solar energy since time immemorial. The mere energy isn't a problem -- but packing it up for transportation is.

I don't believe that "total conversion" matter/antimatter power generation will be practical, now or ever, and there's literally nothing else in theory that will even come close to making a practical fuel source; even if we could bind protons directly to make helium nuclei, that achieves less than 1% of the energy density of total conversion -- "the best energy conversion ratios we can achieve with today's technology" is about 0.01% of TC.

The other killer problem is simply reaction mass. Merely having "energy" doesn't help unless you've got mass to move in the other direction (another reason I don't think that matter/antimatter drives will ever happen). If you're going to assume the development of a reactionless thruster, why not simply assume fairies riding warp speed unicorns? And if you're going to use reaction mass for deceleration -- how are you carrying it?

[Hellbound]

okay, looking forward to your fleshed out appraisal of these factors.

I corrected them in the original post. I did not know I'd already been quoted before I began editing in the correction. It works out closer to 40-50% the energy cost.

And, as drkitten has noted, I did not take any account of reaction mass. THe figures I've made assume the absolute best technology (impossible technology, actually, since no process can be 100% efficient), so this is an absolute limit on the amount of energy needed, under the best possible conditions of technology.

As drkitten said, with anything in current or foreseeable technology, when you add in actual efficiency, fuel costs, and reaction mass, that figure is going to skyrocket. Because if you add, for example, 1 ton of reaction mass, you need 38 more tons-worth of energy to push it. I'd expect actual figures to require much, much more than this (at least a factor of one hundred) for anything in the foreseeable future.

Also, consider that even assuming antimatter is used, you have another problem. Conversion of energy into antimatter is, at best, 50% efficient. Any creation of matter from energy creates equal parts of matter and antimatter. So even before we consider reaction mass and other factors, we've doubled our energy requirement again.

[atari24]

Ok you win. This is my last post on these extremely boring boards. Have a nice life.

WAAAAAAAAAAAAA!

[Kaarjuus]

That sounds like a lot, but it may not be prohibitive. To continue the parallel example to the energy used by the U.S. each year, what percentage of the mass of the moon does the U.S. use in energy each year?

According to these stats (http://www.eia.doe.gov/ipm/supply.html), world oil production in 2005 was 84,361,000 barrels per day. The weight of oil depends on its source, but for about 8 barrels per tonne, this makes 3848970625000 kilograms per year. So, about 3.85×10^12 kilograms. The weight of the moon (http://en.wikipedia.org/wiki/Moon) is about 7,35×10^22 kilograms. So the moon has about 2×10^10 times greater mass than the oil produced in 2005 in the whole world. So a lot more than the hundredth of one percent.

[sphenisc]

Isn't it possible to set up fuel dumps on the way loosely analogous to the truck in the desert puzzle?

http://mathforum.org/library/drmath/view/55689.html

Obviously its got the added complexity of 'coasting' fuel dumps. But there's no need for return trips for the automated placement of fuel dumps. Of course on the way back you're going to be meeting fuel dumps going at some speed!

The most fuel efficient method is left as an exercise for the reader. :rolleyes:

[Hellbound]

Hmmm.

US energy use is equivalemt to about 800 tons (roughly) of mass yearly, which is about 725,000 kg. So that makes it 9.86x10-20 percent of the moon's weight yearly.

[sphenisc]

How much hydrogen etc. can you pick up in the interstellar medium?

[Kaarjuus]

To put the amount of hydrogen needed in better perspective, according to this (http://ga.water.usgs.gov/edu/earthhowmuch.html), there is roughly 1,4x10^21 litres of water in the world. As hydrogen composes 1/9 of the mass of a water molecule, we would need to convert a ninth of the world's water to fuel.

Edit: spelling mistakes.

[Hellbound]

How much hydrogen etc. can you pick up in the interstellar medium?

Not a lot, but now you're introducing two more problems. First, adding the weight of equipment needed to scoop the hydrogen. Second, you're adding to the drag of the spacecraft in the interstellar medium, which means more energy is needed.

IIRC the interstellar medium has a density of somethig around 2 to 3 molecules per m3, but that's recall and I have no idea to the accuracy of that figure.

Ah, check the Wikipedia entry for Bussard Ramjet (http://en.wikipedia.org/wiki/Bussard_ramjet).

Interstellar Space contains an average of 10-21 kg of mass per cubic meter of space. This means that the ramjet scoop must sweep 1018 cubic meters of space to collect one gram of ions per second.

Also gives some info on drag force.

[drkitten]

:confused:

Using Fusion (http://www.astronomy.ohio-state.edu/~ryden/ast162_4/notes15.html), I'll take 650 trillion Joules to mean 6.5x1014 J.

Choosing a 'cruise' velocity of 0.5c (which gives a reasonable time dilation), I get 0.5(1.5x108m/s)2(10000kg) = 1.125x1020 J. Dividing gives approx. 173,000 kg, or am I wrong?\

No, you're not wrong. You were fusing the hydrogen -- I was simply burning it in the calculation you cited. Technically I screwed up because I didn't bring along any oxygen to go with it, about eight times as much by weight.

The reason that I mentioned burning hydrogen is because it's about the best/densest chemical fuel we currently know of (and I think we have reason to believe that it's simply the best there is). If you want to start talking about non-chemical power (e.g. fission, fusion, total conversion, &c), then there's the basic problem that we don't know how to make thrust from any of them. So you can get a lot more energy out of fusing hydrogen than out of burning it, but it's not clear how we can make a fusion-based reaction drive.

[CaveDave]

... some of those might have inferred with our cultural and/or biological development. ...
[Speeling Police]:D
You surely intended interfered, didn't you?
[Speeling Police]:D

Cheers,
Dave

[Hellbound]

\

No, you're not wrong. You were fusing the hydrogen -- I was simply burning it in the calculation you cited. Technically I screwed up because I didn't bring along any oxygen to go with it, about eight times as much by weight.

The reason that I mentioned burning hydrogen is because it's about the best/densest chemical fuel we currently know of (and I think we have reason to believe that it's simply the best there is). If you want to start talking about non-chemical power (e.g. fission, fusion, total conversion, &c), then there's the basic problem that we don't know how to make thrust from any of them. So you can get a lot more energy out of fusing hydrogen than out of burning it, but it's not clear how we can make a fusion-based reaction drive.

I think the assumption is simple thermal reactions. i.e.-a fission reaction, using the heat from it to expel a reaction mass (which may be the fission by-products themselves). Or fusion, allowing an opening in the fusion chamber to expel the helium/wahtever that's created (which is heated by it's own fusion). THis, of course, assumes we are able to control and confine fusion within the near future, as well as pass the break-even point.

Antimatter is the easiest (if one ignores containment problems), simply dump your antimatter into the chamber with some hydrogen. THe antimatter reaction heats the hydrogen as your reaction mass. IT also has an advantage in that for longer trips, instead of increasing your reaction mass, you simply increase the antimatter amount and inject more at a time, increasing the specific impulse of the exhaust (so the same amount of hydrogen ejects faster, producing more thrust...or a smaller amount of hydrogen ejects faster, producing the same thrust).

NASA has done testing on thermal designs, using nuclear power to heat reaction mass. Look here under Thermal Rockets (http://www.pma.caltech.edu/~chirata/deltav.html) for a brief bit on it. Thermal engines seem capable of producing specific impulses 2 to 4 times as much as chemical fuels. Ion rockets have low thrust and power, but high efficiency and very high specific impulse.

There are possibilities for higher-energy chemicla fuels, as well, on that same page: Hydrogen-Flourine, Hydrogen/Ozone, and Beryllium/oxygen all have higher potential specific impulses than hydrogen/oxygen. All have drawbacks, though (acidic, explosive, and toxic, respectively).

[Hellbound]

Interestingly, the same site I linked to earlier gives a nice graph describing how your delta-V (desired change in speed measured in km/s) relates to the percentage of vehicle that must be fuel. The exhaust velocity of the engines figures into it, as well. So with antimatter, assuming an exhaust velocity of the speed of light, and a 1G max acceleration, we can figure out total deltaV assuming a constant acceleration out and back. 1G constant will reach c before our halfway point (well, not actually, but as close a percentage as makes not much difference, about 96% at half the distance). So best-case scenario we'd need 85% of our mass in fuel (Delta-V to c, then deccelerate again, so total delta-V is 2c (well, about 1.92c, but close enough).

[Dave1001]

To put the amount of hydrogen needed in better perspective, according to this (http://ga.water.usgs.gov/edu/earthhowmuch.html), there is roughly 1,4x10^21 litres of water in the world. As hydrogen composes 1/9 of the mass of a water molecule, we would need to convert a ninth of the world's water to fuel.

Edit: spelling mistakes.

Well, clearly the earth's water would probably not be our target source of hydrogen fuel. Where else in the solar system would be good sources of hydrogen fuel? If we're limited to water, I suspect the Earth only has a tiny fraction of the water we need.

[Dave1001]

According to these stats (http://www.eia.doe.gov/ipm/supply.html), world oil production in 2005 was 84,361,000 barrels per day. The weight of oil depends on its source, but for about 8 barrels per tonne, this makes 3848970625000 kilograms per year. So, about 3.85×10^12 kilograms. The weight of the moon (http://en.wikipedia.org/wiki/Moon) is about 7,35×10^22 kilograms. So the moon has about 2×10^10 times greater mass than the oil produced in 2005 in the whole world. So a lot more than the hundredth of one percent.

I don't know to what degree we're comparing apples and oranges here. Your numbers don't seem reconcilable with the numbers others have posted that the trip would take a few percentage point of the energy Americans expend in a year.

It seems counterintuitive to me that accelerating and decelerating a space ship that only weighs 10 tons and its fuel such that the passengers experience .1G to 1 G of force for a limited number of years would expend so much more energy that the earth's human population currently consumes in a year. Am I missing something? For starters, how long would the trip take from the perspective of observers from Earth? Huntsman? I presume something less than a gazillion years?

[Hellbound]

I don't know to what degree we're comparing apples and oranges here. Your numbers don't seem reconcilable with the numbers others have posted that the trip would take a few percentage point of the energy Americans expend in a year.

It seems counterintuitive to me that accelerating and decelerating a space ship that only weighs 10 tons and its fuel such that the passengers experience .1G to 1 G of force for a limited number of years would expend so much more energy that the earth's human population currently consumes in a year. Am I missing something? For starters, how long would the trip take from the perspective of observers from Earth? Huntsman? I presume something less than a gazillion years?

You're missing my corrections, in that the ship would weigh 10 tons for the payload only. The actual ship would weigh in at almost 400 tons, most of that fuel mass. It's corrected in my first post above, which I mentioned the first time you asked about it. This changes the figure to about 40% of U.S. energy use.

However, my calculations assume a few things that are unrealistic:

1. A 100% matter-to-energy conversion
2. A 100% efficient use of turning that energy into thrust.

Both of these are absolutely unsupportable for final figures. At a minimum, you have to double the energy requirement just to create the antimatter (again, assuming no energy is lost, you get 50% efficiency in manufacturing antimatter). Then, I did not account fo any reaction mass or any way for the energy release by the matter/antimatter reaction to be converted to thrust. A large portion of this will be released as gamma radiation, which can't be effectively used for thrust. Plus, the heating of the reaction chamber and surroundings, light released, etc, etc, etc. My estimate of 50% was likely far off before, with a bit more thought.

MOre likely efficincies are about 10%. So, you have 10%*50%, which means the total process is about 5% efficient. So, that 40% of the U.S energy budget translates to about 800% of the U.S. budget, which is about 30% more than the world energy budget for a year.

And we haven't built the ship, the antimatter production facility, or anything else.

To add more, currently the best proposed efficiency for an antimatter production line is 1%.

There's a LOT of problems to be overcome before we're anywhere close to this.

[Dave1001]

You're missing my corrections, in that the ship would weigh 10 tons for the payload only. The actual ship would weigh in at almost 400 tons, most of that fuel mass. It's corrected in my first post above, which I mentioned the first time you asked about it. This changes the figure to about 40% of U.S. energy use.

However, my calculations assume a few things that are unrealistic:

1. A 100% matter-to-energy conversion
2. A 100% efficient use of turning that energy into thrust.

Both of these are absolutely unsupportable for final figures. At a minimum, you have to double the energy requirement just to create the antimatter (again, assuming no energy is lost, you get 50% efficiency in manufacturing antimatter). Then, I did not account fo any reaction mass or any way for the energy release by the matter/antimatter reaction to be converted to thrust. A large portion of this will be released as gamma radiation, which can't be effectively used for thrust. Plus, the heating of the reaction chamber and surroundings, light released, etc, etc, etc. My estimate of 50% was likely far off before, with a bit more thought.

MOre likely efficincies are about 10%. So, you have 10%*50%, which means the total process is about 5% efficient. So, that 40% of the U.S energy budget translates to about 800% of the U.S. budget, which is about 30% more than the world energy budget for a year.

And we haven't built the ship, the antimatter production facility, or anything else.

To add more, currently the best proposed efficiency for an antimatter production line is 1%.

There's a LOT of problems to be overcome before we're anywhere close to this.

I saw your corrections although thanks for spelling it all out clearly here. My responses were to people that described using non-antimatter fuel like hydrogen fuel. Is antimatter a speculative fuel? If so, let's keep it to fuels that we know for a fact are usable in 2006.

I assume that that doesn't affect energy efficiency calculations of 10% efficiency, which is sounds like your saying is what's known to be realistic with technology in 2006.

But, I assume that using non-antimatter fuel affects the amount of fuel that will have to be transported, meaning that a lot, lot more fuel would have to be transported. How much hydrogen fuel would have to be transported for example? Where would we get if from? And do you think it could be done with today's technology? If not, how much of a leap would have to be made within a few centuries?

I guess, in short, could you redo these calculations, but using a known usable fuel source rather than antimatter? Could you give your assessment on whether we have sufficient quantities of this fuel source in our solar system that regular interstellar trips could be fueled by it? How much it would affect the entire mass of the space vessel throughout the trip? And what percentage of global energy use in 2006 terms would be needed to be expended to fuel a round trip? Thanks :)

[Jimbo07]

There's a LOT of problems to be overcome before we're anywhere close to this.

Columbus died in 1506, according to Wikipedia (http://en.wikipedia.org/wiki/Christopher_Columbus), still believing he had reached Asia. That is, by 1506, he was still underestimating the magnitude of his own problem.

In 2006, we're still crawling into orbit on experimental spacecraft, awed by still further distances that boggle the imagination. 500 years and we stand on an ocean vastly different than any previously imagined.

Now, if his ships had a top speed of between 5 and 15 knots, I'll generously say they went 25 km/h. The space station orbits at about 27,000 km/h, or roughly 1000 times the speed of ships 500 years ago, in a vastly different environment.

A 1000-fold increase over that would be, say, 25 M km/h, or 6.94x106 m/s gives a little more than 0.2c or 500 years from now, 1000 times the speed of ships today, in a vastly different environment (interstellar space).

Now sometimes, no matter what resources you throw at a problem, you encounter physical limits. A good example is transistor scaling. However, there is usually someone willing to look at workarounds, such as increasing die size if transistor density isn't improving, different semiconductor and interconnect technologies, etc.

...

drkitten and I have crossed on this before (specifically, FTL at the time). My two wild analogies are a little glib, but I maintain that impossible is a very strong word. Impossible is radically different from, "There's a LOT of problems." In fact, impossible doesn't even mean the same as a LOT LOT of problems. You'd have to have a googolplex of problems without even the wild imaginings of a solution before you got anywhere near impossible.

I wouldn't let the failure of realizing the movie 2001 inform wild speculation about events 500 or more years from now...

ETA: Just to be clear, my love for interstellar travel is fuelled much more by science fiction than science fact, which I freely admit. I think there is an interesting enough set of problems with interplanetary travel, and should I be lucky enough to do any instrumentation work on any spacecraft that actually flies, I will consider myself to be more than fulfilled.

[Hellbound]

I saw your corrections although thanks for spelling it all out clearly here. My responses were to people that described using non-antimatter fuel like hydrogen fuel. Is antimatter a speculative fuel? If so, let's keep it to fuels that we know for a fact are usable in 2006.

I assume that that doesn't affect energy efficiency calculations of 10% efficiency, which is sounds like your saying is what's known to be realistic with technology in 2006.

But, I assume that using non-antimatter fuel affects the amount of fuel that will have to be transported, meaning that a lot, lot more fuel would have to be transported. How much hydrogen fuel would have to be transported for example? Where would we get if from? And do you think it could be done with today's technology? If not, how much of a leap would have to be made within a few centuries?

I guess, in short, could you redo these calculations, but using a known usable fuel source rather than antimatter? Could you give your assessment on whether we have sufficient quantities of this fuel source in our solar system that regular interstellar trips could be fueled by it? How much it would affect the entire mass of the space vessel throughout the trip? And what percentage of global energy use in 2006 terms would be needed to be expended to fuel a round trip? Thanks :)

The 10% figure was a more realistic efficiency for an antimatter drive.

Conventional fuels are in the 1% range, at best. I couldn't even begin to calculate the numbers on that, but it going to end up being several times the amount of energy the world produces in a year.

[Schneibster]

With slowships, you have two problems:
1. Energy source.
2. Reaction mass.
Only a nuclear reaction can provide the energy needed; chemical reactions produce too low an energy density to be practical (a tenth of the Moon's mass, or some such absurdity). Thus, it's fission or fusion, from what we know right now, and fusion is pretty woo; antimatter isn't even on the table yet. We might do something with antimatter, once we can make it, and it would certainly be more powerful than anything we're going to do with either fission or fusion, but I suspect we have quite a ways to go before we have practical fusion, I'll be surprised if we have anything up and running on a practical basis before mid-century, and antimatter looks a lot farther away than that.

I'd go so far as to predict that when (yes, when, not if) we first send something or someone to another solar system, and I think it will be late in this century, we'll use solar sails for a significant amount of the acceleration and braking at both ends, and slingshot around the star in question (whether that be the Sun on this end or the destination system's star on the other) to maximize the benefits of the reaction drive we will no doubt start with; something that we can burn and make a lot of acceleration really fast, and keep as much momentum as we can figure out how through the slingshot. After we're out of the slingshot, or perhaps merely after we've exhausted our initial push, an ion drive is quite likely, since it provides the highest efficiency of acceleration of the reaction mass; most likely at a very low thrust, like well under a tenth of a gravity, perhaps as low as a hundredth. You get a lot more bang for the buck accelerating charged particles using an electromagnetic field than you do heating them, unless you have a really good heat source, which we don't (even fusion won't do it; fusion makes more energy in charged particles than it does in heat). This takes care of both the energy source and reaction mass problems, but at the cost of a very long transit time. Someone do the math; I'm too lazy. The math on the solar sail will be interesting too, both in terms of size vs. thrust, and in terms of bundling it up when it stops being a winning proposition and then carrying it to the destination, then spreading it again, etc.

As far as FTL goes, as far as I can tell from a great deal of research, and I'll even confess to having begun with a bias toward it, it looks impossible. The problem is that if you travel from point A to point B at FTL speed, there will always be some possible observer for whom you would arrive before you left, and this violates mass/energy conservation because you would have to exist at both the source and destination at the same time. In other words, unless mass/energy conservation is wrong, FTL is impossible.

Now, if I had found instead, for instance, that it just would require relativity to be wrong, you know, Albert had a little brain fart, heh heh, then I might buy that; but mass/energy conservation? No way. Not gonna happen. It's just too basic to the way that reality appears to work. Sorry to pee in your cheerios.

[Kaarjuus]

I'd go so far as to predict that when (yes, when, not if) we first send something or someone to another solar system, and I think it will be late in this century

Mankind will have great trouble powering itself late in this century after oil supply dries up and you think we'll have enough power for interstellar flight?

Using a solar sail, if we even are able to develop one that works well, will take forever. This would require a self-contained little world, with hundreds of generations of people manning the craft. I enjoy science fiction immensely, but this is unrealistic.

[Dave1001]

Mankind will have great trouble powering itself late in this century after oil supply dries up and you think we'll have enough power for interstellar flight?

I think that's a bit pessimistic (not talking about the interstellar flight aspect), because we have so many other demonstrated sources of energy, we have so many demonstrated ways to increase energy use efficiency, etc. My understanding is that we primarily use oil for energy not because it's the only energy source in abundance to serve our needs, but because it's currently the cheapest to extract and use (and further, my impression is that it's currently the cheapest to extract and use due to existing oil-based infrastructure build-up).

[Dave1001]

The 10% figure was a more realistic efficiency for an antimatter drive.

Conventional fuels are in the 1% range, at best. I couldn't even begin to calculate the numbers on that, but it going to end up being several times the amount of energy the world produces in a year.

Too bad (that you don't think you could make a calculation with that) cause I suspect it will still seem on balance realistic. As for it taking several time the amount of energy the world currently produces in a year, that doesn't seem like it should be especially prohibitive within the next several hundred years. It's probably not fair to imagine that in 300 years, the amount of energy the world produces in a year will be a similar scale leap as from 1700 to the present. But I'm curious how our energy production has increasted from 1950 to the present, given that I think our energy technologies are basically the same now as they were then (but my sense is that our economy and energy production has increased by orders of magnitude).

[Dave1001]

With slowships, you have two problems:
1. Energy source.
2. Reaction mass.
Only a nuclear reaction can provide the energy needed; chemical reactions produce too low an energy density to be practical (a tenth of the Moon's mass, or some such absurdity). Thus, it's fission or fusion, from what we know right now, and fusion is pretty woo; antimatter isn't even on the table yet. We might do something with antimatter, once we can make it, and it would certainly be more powerful than anything we're going to do with either fission or fusion, but I suspect we have quite a ways to go before we have practical fusion, I'll be surprised if we have anything up and running on a practical basis before mid-century, and antimatter looks a lot farther away than that.

I'd go so far as to predict that when (yes, when, not if) we first send something or someone to another solar system, and I think it will be late in this century, we'll use solar sails for a significant amount of the acceleration and braking at both ends, and slingshot around the star in question (whether that be the Sun on this end or the destination system's star on the other) to maximize the benefits of the reaction drive we will no doubt start with; something that we can burn and make a lot of acceleration really fast, and keep as much momentum as we can figure out how through the slingshot. After we're out of the slingshot, or perhaps merely after we've exhausted our initial push, an ion drive is quite likely, since it provides the highest efficiency of acceleration of the reaction mass; most likely at a very low thrust, like well under a tenth of a gravity, perhaps as low as a hundredth. You get a lot more bang for the buck accelerating charged particles using an electromagnetic field than you do heating them, unless you have a really good heat source, which we don't (even fusion won't do it; fusion makes more energy in charged particles than it does in heat). This takes care of both the energy source and reaction mass problems, but at the cost of a very long transit time. Someone do the math; I'm too lazy. The math on the solar sail will be interesting too, both in terms of size vs. thrust, and in terms of bundling it up when it stops being a winning proposition and then carrying it to the destination, then spreading it again, etc.

Fascinating! Is all of the technology you discuss here currently available and proven? Fission (is that the same as currently used atomic power?) and the technology that a solar sail uses? ion drives accelerating charged particles using an electromagnetic field? In other words, would it be technically possible to launch such a mission with today's technology? If some of these technologies are still speculative, then could such a mission be launched without them? If it can be done with today's technology, and the only prohibitive factor is cost, then I agree with you that such manned adventures will be launched, although I would probably stick with the several hundred year window. That we have not returned to the moon in a manned mission in 30 years is an indication to me that it will be hard to predict the rate of manned mission envelope-pushing in the time frame of decades.

[King of the Americas]

Question, did the picture of the Wright brothers first flight, 'prove' that they could fly?

Moreover, can 'we', as present day scientists, take this single still photograph as actual evidence that Orville did indeed take mankind into the sky on December 17th 1903?

'I' say, Yes... BUT you skeptics should or would probably say that the photo could have been faked...

And herein lies the catch to 'proving' anything. I take any evidence of anything with a grain of salt. Was there enough evidence to tell me that OJ was guilty, I think so, but the jury was convienced by the defense that some of the evidence 'could' have been tampered with and or planted. So proof beyond a reasonable doubt of his guilt was absent, in the jury's mind. However, one should NOT confuse not guilty with innocence...

Now, let us examine what 'proof' there is that we have been visited and or probed by E.T. Well, none that places the 'proof' beyond a reasonable doubt. But what I have found more often than not, is that IF a photo or a piece of video footage COULD be faked, then it is dismissed outright. And that is a notion I disagree with. Proof beyond a reasonable doubt of E.T. existance and visitation will likely be non-existant until one appears on the White House lawn during a rose garden press conference televised live. (then again if THAT happens, said E.T.'s will be taken under arrest and placed in quarantine)

My original notion, that there must be 'some' truth behind all these myths spawns from that whole finding Troy thing, and the similarities between the tale of Noah and the Epic of Gilgmesh.
Personally, I have seen and even collected evidence that 'heavenly' entities DO indeed exist, in some form or another. Now, I am NOT suggesting that such evidence is rock solid or 'proof beyond a reasonable doubt', of such a claim. What I AM saying is that I have seen a LOT of evidence all pointing to the same possiblity, that we HAVE indeed been visited, studied and or experimented on, by E.T.'s.

Moreover, I find that the atheists may very well be correct in their assumption that there is no God...but rather god(s) {*lower case}, and that the believers are too incorrect in identfying these 'more-than human' thing(s) as capital letter- "God". I think the metaphysical folks/believers define their "God" as the omni-present, omni-potent being who can do it all. And THAT is where they are wrong. Whereas the atheists are wrong in their dismissing out of hand the very notion that there isn't 'something' god-like flying about the heavens and or poking and proding humans.

I would like to thank all you number crunchers for your insight into intersteller flight dimensions and demands, I found it most interesting.