From: David Rudiak <drudiak.nul> Date: Mon, 17 Dec 2012 11:01:57 -0800 Archived: Tue, 18 Dec 2012 07:08:22 -0500 Subject: Re: Update To Our View Of The Drake Equation >From: Edward Gehrman <egehrman.nul> >To: <post.nul> >Date: Sun, 16 Dec 2012 08:55:42 -0800 >Subject: Re: Update To Our View Of The Drake Equation >>From: David Rudiak <drudiak.nul> >>To: post.nul >>Date: Sat, 15 Dec 2012 11:59:07 -0800 >>Subject: Re: Update To Our View Of The Drake Equatio >Thanks for the information. You're correct. I have a very basic >physics understanding and I didn't know how the math worked out. >That's why I asked the question. Your explanation helped but I >have a few more questions. >How does the laser beam stay focused on the space craft? What >happens to the space craft if there is a malfunction of the >laser and the beam is interrupted? Ed, this was a thought experiment to illustrate how it might be possible for humans to come up with energies needed to propel probes to some fraction of light speed and achieve interstellar travel in a reasonable period of time. And if we can conceivably do it, thenso can some other technological civilization. Ones much older than us could have achieved interstellar migration a long time ago and be visiting us now. That's the counter to the usual argument against UFOs that interstellartravel is impossible, therefore UFOs cannot represent interstellar visitation. You can of course come up with various scenarios where things go terribly wrong, such as space shuttles blowing up on takeoff or disintegrating on reentry. That doesn't mean that space shuttle flight is impossible. Similarly, technical problems with designing and implementing an interstellar flight system doesn't make it impossible, just very difficult. If there are no fundamental physical, economic, or political limitations, engineers are usually very goodat figuring out how to deal with the technical problems. >When you calculate energy use, are you doing it by the second or >hour or day or just the initial need. You wrote: >"The energy to accelerate that 10 ton probe to 10% light speed >would be the equivalent of less than one day's operation of such >a system." I'm talking about total energy needed to accelerate the probe to 10% light speed. The energy per second is the power, and the total energy is the power times the time. Energy is total quantity; power the rate at which the energy is delivered. Fill your bath tub with water and gallons is the quantity, but gallons per minute is the rate at which you fill it. In my thought experiment, you could generate enough energy with the robotic moon solar energy stations to accelerate the 10 ton probe to 10% light speed in less than a day. In the real engineering world, things wouldn't be so simple. As noted, power or energy per second of such a system would be equivalent to the energy of an A-bomb blast every second. I doubt you could focus that much power on the probes laser light-capturing sail without incinerating it. Instead you would probably need to use some fraction of that power and stretch out the acceleration period over a much longer period of time. Hard as it may be to believe, a square mile of Earth receives an A-bomb's worth of solar energy every day, and we don't burn up because it is gently spread over a large area and period of time instead of into a tiny area and fraction of a second. The total energies are the same, but the power levels and densities are many orders of magnitude different. So maybe that probe would need to be accelerated at much lower power levels over a period of a year or two instead of a day to prevent being incinerated. Again, the point of the exercise was to illustrate how human civilization in the not-too-distant future might generate the energies needed to achieve interstellar travel in an economical way, not provide a complete blueprint of exactly how this would be carried out. >Once the craft arrives at the required speed, is the laser still >needed? In other words, does it require the same amount of >energy per second, or hour or day to stay at speed, or once it >gets to speed, does it glide to its destination? In deep space there is essentially no friction, so yes it could glide to its destination, just as our chemical rockets burn only briefly during the acceleration phrase. The Apollo space capsules did not fire rockets all the way to the Moon and back. Or with the laser system, you could keep on accelerating the probe for as long as you could keep the lasers focused on it. Again, this was a thought experiment to illustrate how one might achieve only 0.1c interstellar space travel, but the same system could theoretically boost you to even greater speeds since energy supplied is external and does not have to be carried on board the probe. >And once it gets there, how does it stop and then turn around >and return? It's a probe. It doesn't need to stop and turn around to get back, no more so than other of our rocket-based probes turn around and come back. Most do flybys, like the old Voyager probes now on the edges of our solar system. If you do want to stop and linger (and possibly colonize), then you do need some way to decelerate your probe, which would take the equivalent amount of energy as accelerating it. NASA had a proposal for that as well, but I forget. It would be technically much more difficult, but not impossible. >I agree that our visitors seem concerned with our nuclear >weapons. Why should they be if they don't live here? Maybe ethics and philosophy. Planets with extensive, complex life are probably quite rare. It's a tragedy to see one self- destruct. I think we might feel much the same way about some other civilization and planet. Or maybe for the same reason, we are a rare genetic resource that they are using. Wouldn't want to destroy such a valuable resource through nuclear war or environmental collapse. Their possible concerns about our future doesn't mean they necessarily live side by side with us or arose on Earth, though I wouldn't rule out the possibility that Earth could have been visited and even colonized by externals many times in the past, or now. But my definition of ET is a very general one: did not originate on planet Earth. Even if they are co-existing with us now in some way, they did not arise and evolve here like we did. I have seen no physical evidence pointing in that direction. A technological civilization can't just arise and disappear without leaving a trace, yet still be here hiding under some rock that we haven't overturned yet. It took a world civilization with billions of people and thousands of cities just to get us where we are now. >Since they don't seem to be looking for a fight, it's much more >likely that their concern is generated by their knowledge that >we could destroy the neighborhood we both share. Possibly, but as noted, there are other possibilities as well, so I wouldn't characterize your scenario as "much more likely." We are all speculating here. Listen to 'Strange Days... Indeed' - The PodCast At: http://www.virtuallystrange.net/ufo/sdi/program/ These contents above are copyright of the author and UFO UpDates - Toronto. They may not be reproduced without the express permission of both parties and are intended for educational use only.
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