Centerfield

Just too cool and odd not to throw in an open thread....

TO THE STARS!

The X Prize Foundation is working to bring regular folks up to the edge of space, NASA is aiming for the moon, and the Mars Society is pushing for trips to the Red Planet. So who's focusing on the incredibly far frontier beyond the solar system? Scientists and dreamers from NASA and elsewhere have established a new foundation to focus on the real-life prospects for interstellar flight.

Posted by: Tully at July 7, 2006 12:37 AM

call me a pessimist, but I have serious doubts that we'll ever come up with the sort of technological breakthrough that will allow interstellar travel in any way that's not onerous and lengthy.

Not saying we shouldn't try, or that there's no merit to the idea. I'm just saying that I don't think we'll be traveling through worm holes or besting the speed of light so as to travel to places light years away in a matter of seconds, hours, or days. And I cheerfull concede that I don't have a clue what I'm talking about, It's almost purely a gut feeling that while there may indeed be pie, it's not going to be in the sky. IOW, the real world practice of traveling in space is that it will be slow, and boring, and that space will be foubnd to be just that...99.999999999999% empty space.

Posted by: bk at July 7, 2006 11:40 AM

Based on what we know today, Brian is certainly correct. On the other hand, based on what we knew 500 years ago, the same could have been said of travel thru the empty air. The problem, of course, is that we keep learning new things which change what is possible.

Does that mean I think we will end up traveling thru worm holes or hyperspace? Nope. Because if history indicates anything it is that the actual solution in this case is likely to be something which nobody had thought of centuries before it came to pass. Kerosene in Otto cycle engines to move vehicles thru the air? Even one century, let alone 5, before airplanes became practical nobody would have come up with that one! And mostly they were thinking of flapping wings, which nobody actually uses.

And I would bet that we are more like 500 years than 100 from managing to get people to another star. Although I suspect that we could, with foreseeable technology, manage within 100 years to _start_ an automated vehicle on a trip to the Alpha Centauri and have a reasonable chance of it eventually arriving and sending back pictures.

Posted by: wj at July 7, 2006 12:34 PM

WJ, while all you say is preety much true, I'm more pessimistic than that. It's easy for you to say, and so it's just as easy for me to cheerily concede that 500 years ago the things we do and know now were practically unimaginable.

But even 500 years ago we could see birds fly, and we had fireworks. So IMO the flight and propulsion things we do now were a little bit more imaginable. (although i also cheerily concede we're working without a decent yardstick, making such judgements very suspect).

The thing that gives me pause is that the known physics seem to suggest some bounds on the realm of the possible. Again, I am (pun intended)light years from any practical expertise, but hat little I do know seems at glance to suggest that humans aren't going to be able to surpass the speed of light unless we find a way to transform and reconstitute living beings and/or bend space time. I view such stuff as being about as far-fetched as it gets. Granted, that it is "fetchable" at all means that it is imaginable.

When one considers the nature of growth and sutenance of the species, it seems like we have 2 choices, broadly speaking. We either have to accept Earth as our finite space for all practical purposes, or we have to accept that growth is necessry for survival, and growth will eventually require expansion beyonf Earth's finite space. I find the former an inviting prospect philosophically, since it suggests that ultimately introspection and self-examination are unavoidable. But what I believe about human nature suggests to me that the latter case (survival only by continual outward growth) is more likely. In other wors, I think we need to keep growing outward in order to thrive.

And i think that we way we do this is going to much more closely resemble the ways we already know than it is going to resemble the pretty dreams we can imagine. I don't expect transcendent breakthroughs in physics that render the speed of light a problem of the past. My guts says its an upper bound.

I expect a glacial expansion into the realm beyond Earth driven by determination and necessity. It wiill grow as networks of tenous spidery webs using ingenious and usually barely-good-enough duct tape methodology. In other words, I expect this expansion to be more about brute force of will and need than miracles of beautiful elegance. Speed of light aside, I'm saying more about the way in which I think we'll transcend our current bounds than I am about what I think our bounds are.

Posted by: bk at July 7, 2006 01:05 PM

Im think, Mars colony in 50 years or less, and Martian atmosphere production in 100 or less, stars? 300-500 years, hyperlight travel? Maybe never, maybe next week. who knows

Posted by: Dan at July 7, 2006 01:11 PM

Anyone have any thoughts on the current escalation of the NK missile melodrama? I noticed that the immediate aftermath suggested an ephemeral show of global unity, which is of course always the way. Just about everyon agreed that the didn't like it much that NK was rattling its sabre, thumbing it's nose in defiance.

But since when does translate into concrete action? Many nations are united in their not liking of the missile test. Buit are they united in what they think should be done about it? Nope.

NK understands this. Clearly the smarter ones among the globes despots took copious notes on Saddam Hussein's conduct, and they all havew a good idea about how best to play "jerk the UN round the mulberry bush again, like we did last summer."

And of course, such things come easy to bullies anyway. It's a first grade lesson. Both bullies and the bullied know that the not liking wehat a bully is doing matters not a fig. The only relevant question is "whaddaya gonna do about it?"

I don't think anyoine is going to get together and do anything substantive about NK any time soon. Unless you count threatening and talking and handshaking and re-negging.

Posted by: bk at July 7, 2006 01:14 PM

Although I suspect that we could, with foreseeable technology, manage within 100 years to _start_ an automated vehicle on a trip to the Alpha Centauri and have a reasonable chance of it eventually arriving and sending back pictures.

We could do that now, wj. If we wanted to pay for it, and we were really patient on waiting for the arrival data. Lemme give that one a kick--Voyager 1 and Voyager 2, both launched in 1977, are still in operation, still sending and receiving data, and are both roughly 17 BILLION miles from Earth. That's six times the distance from the sun to Neptune, past the termination shock barrier of the solar system and into the heliosheath. Both probes are expected to reach the heliopause still functioning and returning data. Past that, no one knows.

OK, that's a really slow boat in terms of cosmic distances--but those two 1970's-tech probes are still sending and receiving data from quite a LONG ways away. With current technology we could launch a Centauri probe. With any form of incremental constant-acceleration drive our grandkids could watch the data come in.

Posted by: Tully at July 7, 2006 01:16 PM

I expect a glacial expansion into the realm beyond Earth driven by determination and necessity.

That's exactly right, I think; for example, the Russians and the Chinese are interested in going to the moon because they believe they can exploit a helium isotope that is abundant there for energy. Likewise, I think that as space technology develops, it will become more and more practical to seek to mine gasses and materials from other planets that are either scarce or difficult to extract here. The future will not look like Star Trek, but it might look a lot like Outland (or even the factual setup underlying the Alien trilogy). Posted by: Simon at July 7, 2006 01:20 PM

The speed of light is one of those tricky things, it seems.

Whether it takes 100 or 500 years (I'll venture it closer to former than the latter) when mankind learns how to achieve near light speed it will mean something fundamentally different than we are used to. It will mean that, in our (future) lifetimes we can go farther than we ever thought we could, BUT we can NEVER GO BACK to the life we leave behind. Any people we leave behind would be dead in a matter of (interspace) months.

I wholeheartedly agree that the biggest changes will be in places we never even imagine. One of the biggest, I believe, will be a Revolution in Economics that will empower individuals to a degree no one will be ready for. Issues of powerlessness in life will give way to issues of morality regarding WHETHER things that are possible should be done in the 1st place.

The limits of Outer Space will be met with the limitlessness of Inner Space. Issues of psychology and the Mind will become common place. The confluence of Genetics and Psychology (i.e. the illusion of superior vs. inferior) will come to the forefront. And all the while, I believe, we will come face to face with the notion that, the more we come to know, the LESS we own of what actually is out there to BE KNOWN. And moreover, the more powerful we become, the more careful we must be, NOT for the sake of others, BUT in fact, for OURSELVES.

Posted by: Cavalier829 at July 7, 2006 02:06 PM

To put the distance travelled by the Voyagers into perspective, they've gone about 26 light-hours. Proxima Centauri is about 4.2 light-years. But the Voyagers have had NO additional acceleration on their trip since launch, other than gravity assist from planetary fly-by. And even an apparently trivial constant acceleration of 0.01 g adds up quite considerably over time.

Now, I'm not a ballistics math man so I can't vouch for certainty in my calculations, BUT...a probe capable of a constant 0.01 g acceleration would reach Proxima Centauri in about 29 years if it didn't have to stop when it got there, and in about 40 years if it accelerated halfway and then decelerated the rest, to reach the system and explore rather than just flying by. At 0.1 g (a tenth of a gravity) a flyby would take a decade to get there, or about 13.5 years if you were stopping and staying.

And even at a paltry constant acceleration of 0.001 g you'd be doing a flyby in under a century.

Posted by: Tully at July 7, 2006 02:09 PM

I'm home, recovering from a biking accident (must watch both far traffic AND nearby trash cans pushed far out into road AT THE SAME TIME). My current guess is that we'll get there via some kind of wormhole engineering. IMHO, notime soon, though. That doesn't mean it isn't worth keeping an idea on the field of possibilities.

Leonardo did correctly predict that wings would be used to fly, it's just that he had no idea how they would be used. And that's where we are on wormholes; all the math about wormhole travel that you hear about is utterly useless except as a fun exercise, and even if we had a wormhole available nearby without the planet being doomed, we're only talking about one atom at time. But it could turn out that some simpler trick is available. I sure hope so!

IMHO, we're looking at a centuryish til wormhole engineering. And it'll take alot of work between creation of (virtual?) wormholes to get to practical travel.

Posted by: Jon Kay at July 7, 2006 02:18 PM

You have to get to a pretty hefty fraction of c (lightspeed) for time dilation to get serious and noticeable, Cav. 80% or so? Something like that. And at the upper ranges additional acceleration quits producing the same speed gains--as mass rises the gains are incremental, with increase in velocity inverse to the time dilation. But I'm exceeding my level of informed ignorance here, so don't take that as fact, just a rough tool for speculation.

Stealing someone's publicly posted applet for constant-acceleration trips (and damn but I wish I'd found that BEFORE I gave myself a math migraine) I find that my initial calculations on acceleration were correct, and we don't have to give ourelves math headaches unless we want to know the exact fraction of c reached at midpoint before deceleration.

Relativistically speaking, going to Proxima Centauri at 1 g would take 5.8 years as seen from earth, but 3.5 years "ship's time." Assume they hang out for a year to explore, then come home. 12.6 years round-trip on earth, 8 years ship's time.

At 0.1 g constant it would be 13.4 years each way from earth, or 27.8 years with that stopover, compared to 12.5 years ship's time each leg, or 26 years with that stopover.

Not unreachable.

(My sympathies, Jon. I always manage to avoid the traffic, but those staionary objects are sneaky....)

Posted by: Tully at July 7, 2006 02:31 PM

Now, I'm not a ballistics math man so I can't vouch for certainty in my calculations, BUT...a probe capable of a constant 0.01 g acceleration would reach Proxima Centauri in about 29 years if it didn't have to stop when it got there, and in about 40 years if it accelerated halfway and then decelerated the rest

Well, the challenge, then, is how to design either a solar sail that can sustain >0.01g acceleration in interstellar space, or to design an engine with an engine that will do the same thing, but with an adequate fuel source compact enough to be carried by the probe. Or perhaps some combination of the two - a solar sail that would carry it as far as the heliopause, which would then be jetissoned and an ion engine deployed for the rest of the journey? Posted by: Simon at July 7, 2006 02:48 PM

Not very centrist, but rather amusing. Mind you, I think most people would agree that bashing Cindy Sheehan is puerile but fun, and Michelle Malkin is always watchable.

Posted by: Simon at July 7, 2006 03:25 PM

Yeah solar sails for interstellar travel have a wee problem. Constantly reducing thrust from reduced radiative solar pressure at distance, and all that. But anything that gives you a boost (ANY boost) without eating up your reaction mass is a Good Thing. So the two-stage (or more) idea is sound.

You might be surprised at some of the drive concepts that are already either tested or in development. Solar sails are one of them. NASA's working on a plasma-fusion drive right now, one developed by one of our astronauts, no less.

Posted by: Tully at July 7, 2006 03:41 PM

Some video from the Lieberman-Lamont debate. It's like watching a gladiatorial meeting between a field of wheat and a combine harvester. Well played Lieberman.

Posted by: Simon at July 7, 2006 03:42 PM

T.

I guess what your saying is true below the higher percentages, however, I think we have to remember it's a perceptual issue. The closer you get to the speed the more the perception is that it takes more time and energy to get additional speed, but the reality is traded in time. Those traveling at near the speed of light would be perceived by us as barely accelerating, while those on the ship would actually continue to travel faster and faster (assuming your resolved your power issues.)

But for a trip to Alpha Centauri you'd probably only lose 8 or so years to your Earthbound contemporaries.

The Voyagers were only meant for solar travel, right? I don't remember that The Creator meant them to head to Alpha Centauri or somesuch. (Oops, that was Voyager 6. Hasn't even happened yet. Sorry about that.)

Posted by: Cavalier829 at July 7, 2006 04:07 PM

Tully,
From the article:

The Variable Specific Impulse Magnetoplasma Rocket (VASIMR) is a type of propulsion system that produces a plasma exhaust at temperatures similar to those in the interior of the sun. The system may generate rocket thrust with performance hundreds of times higher than that of present chemical rockets. The increased performance could mean dramatic reductions in fuel requirements. While conventional rocket nozzles would melt under the extreme temperatures, VASIMR uses magnetic force fields to control and direct the plasma exhaust jet.

So it's explicitly an impulse engine? Maybe I was wrong about the future not being like Star Trek. ;)

Posted by: Simon at July 7, 2006 04:32 PM

LOL. I hadn't noticed that. There's other types of "impulse engine" designs floating around, but that's the one in development.

Cav, the point is that since you have to get to a high percentage of c before time dilation becomes a factor, there's not much reason. Unless you're making a LOOOOOONG trip and actually need the time dilation. Of course, any sublight interstellar trip qualifies as long!

Dilation and mass increase effects don't really kick in and get humpin' until you're up around 0.8c or better. A lotta respectable rocket science guys say you don't want to go that fast anyway unless you have some way to "sweep" a very clean path out ahead of yourself. Even a measly hydrogen atom can hit hard when you're whacking into it at a big chunk of c. Especially when you get into that increased-mass deal. The more thoughtful ones say that the practical limit may be about 0.6c with magnetic shielding, and maybe 0.3c without, both of which are well shy of any noticeable time dilation effect.

Posted by: Tully at July 7, 2006 06:21 PM

Not much reason...... to even attempt it? Or to worry about it?

So did we decide then, that the Voyagers, if pointed towards, say Alpha Centauri, would actually arrive there in 29 years given current intertia?

Posted by: Cavalier829 at July 7, 2006 06:46 PM

Oh my no. If the V'gers were headed at Proxima Centauri with their current velocities, they'd get there in about 1600 or 1700 years. If they had constant-boost of 0.01g starting NOW they'd be there in 29 years. If they had to come to a stop on arrival instead of whizzing on by, they'd be there in 40.

Posted by: Tully at July 7, 2006 06:53 PM

Not much reason to try to get that last 15% or so of c, unless you've got thrust to throw away and really good shielding.

Posted by: Tully at July 7, 2006 06:55 PM

Teach ME to attempt scalars in my head. If the V'gers were headed to Proxima Centauri at their current velocities right now, their ETA would be roughly 46 thousand years, not 1600. Call it the end of the next ice age.

Posted by: Tully at July 7, 2006 07:00 PM

Dang, Tully, for a second there I thought the rules had gotten easier. But that's o.k..

O.k. maybe you've already answered this and I'm missing the inference:

I get you now regarding the last 20 to 40 % of light speed not being worth the cost, but the reason I wonder if that is fully accurate is what I have believed to be the laws of Relativity.

We know from Einstein that a body requires much larger expenses of energy to get the last percentages, but I thought that was from the stationary vantage point of Earth. But that for the Voyager, human or otherwise, wouldn't one be able to achieve infinite speeds? Wasn't the point of time dilation that you could achieve any speed, you just couldn't take the Universe you knew with you? Meaning that the Universe begins to age more rapidly the closer you get to "c" (as perceived by the stationary body?)

To make it more simple, isn't "c," from a stationary viewpoint, actually a state of omnipresence, hence the fact it is unachievable?

Posted by: Cavalier829 at July 7, 2006 07:44 PM

Breaking topic, it looks like Joe Biden's mouth has gotten him into real trouble:

http://rajforcongress.blogspot.com

Posted by: Rafique Tucker at July 7, 2006 11:39 PM

Ow! I got a math migraine just from trying to read through all of this! The subject absolutely fascinates me -- and I get my bra all twisted wishing I'd had the smarts to take more math and science in high school. Unfortunately, english was easier for me. *sigh*

Posted by: Heather at July 7, 2006 11:47 PM

Nobody here holds Joe Biden in greater contempt than do I, but I think that Malkin got it right - "I don't see what the big deal is over [] Biden's remark ... There are plenty of reasons to roll your eyes when Biden opens his mouth. This doesn't make my list."

Posted by: Simon at July 7, 2006 11:51 PM

And I pretty much took Raj to task for making a mountain out of a mole hill over at Stubborn Facts. He looks to me like just another pandering, say whatever-gets-you-publicity, big on mouth short on substance politician grabbing at the "reform" label as his gimmick for success.

Posted by: PatHMV at July 8, 2006 01:08 AM

To make it more simple, isn't "c," from a stationary viewpoint, actually a state of omnipresence, hence the fact it is unachievable?

Getting WAY over my head, but not as I understand the equations. Then again, I do NOT understand the Lorentz transforms or Minkowski space, or the curved space-time solutions of general relativity either. I studied the wrong kinds of math for physics, and some things don't explain well in words.

Briefly, my own rough verbal take is that "C" is the speed of light in a vacuum, 300,000km/second*, the maximum (known) speed of propogation of electromagnetic radiation. (In general relativity, c is also the speed of the propogation of gravity.) It's a physical constant. It does not change, regardless of your observation point. Light leaving a point A (in a vacuum) will move away from that point A at c. If A is a moving point, the velocity of A does NOT transfer to the light. And from a point B moving at a different speed than point A and in a different direction, that light will still be seen as moving at c away from point A. All that can actually change is the perceived energy/frequency of the light.

c is a constant, maybe THE constant of the universe. It's everything else that's relative.

[*--it's actually a hair under that, but I'm not designing physics experiments, so...]

Posted by: Tully at July 8, 2006 01:14 AM

Actually c as a constant is being questioned recently. Relativity has been a very useful tool, but until we get some sort of unified field theory I remain unconvinced of Relativity's ultimate "truth". There are too many holes in it.

The technology has been in existence for a long time now, but one real problem with reaching a decent % of c is getting the mass necessary out of Earth's gravitational field. Another problem with lengthy spaceflight is the frailty of our bodies. Even a short (3years) manned mission to Mars is doubtful at present. We don't react well to weghtlessness (1g acceleration would be nice, but how do you get that much fuel into Earth orbit?), not to mention cosmic radiation once we leave the magnetosphere.

But not to worry. Useful nanotech and bioengineering could solve the biological problems very shortly. If we were smart we would start terraforming Mars right now. I've seen lowball estimates of $10-20 trillion and less than 500 years to turn it into a very comfortable place.

There is very little doubt in my mind that if we don't eradicate ourselves first that we will colonize our solar system by either shaping it to our needs or shaping ourselves to its reality at some point in the future. I am skeptical that we will leave it other than by telepresence.

Posted by: Dennis at July 8, 2006 03:30 AM

Simon,
First, Biden's "Indian-American" remarks in context were hardly offensive. As for his views on defense strategy and terrorism I submit Biden's thoughts on 9/10/2001 here . Want to show me a Republican view that made more sense the day before 9/11? Now remember Biden didn't know about the trillion dollar invasion of Iraq that was coming, but he did warn of focusing on terrorism instead of prematurely ending the ABM treaty. 100 billion on missile defense for what strategic advantage? When you take the Gore/Clinton agreement with Russia to allow technology transfers and weapons to Iran and the Bush pre-emption of the ABM treaty, it is small wonder we are facing Chinese missile build up and Iranian threats. Biden makes a bunch of sense in his 2001 speech. Many argue we are simply too stretched to deal with Iran. Yesterday the F-35 was christened "Lightening". Not so lightening fast with the money to build them. Fuel Cells for our military, toilets for our troops etc. etc. all are in question because of the actions of this administration's strategies. Put Biden's warnings in context with the usual Right Wing attacks like this. Of course Biden is merely in agreement with his friend Senator Lugar.

Posted by: Maxtrue at July 8, 2006 08:19 AM

And Simon, Malkin taking shots at Biden is more laughable than anything that can be said about Biden. She is a Fox regular that never ceases to embarrass herself with absurd and reactionary opinions. At least she doesn't share Liebau's hair style, if not her talking points.

Posted by: Maxtrue at July 8, 2006 09:45 AM

Dennis, the analyis of that is in dispute, and do please note that even if all the data and analysis were correct, you're talking a change of less than one part in ten billion over a few billion years, and three different constants that are involved. You're right to doubt that we'll ever have a correct Grand Unified Theory, if only because it's ontologically impossible. We are part of what we're observing, we can never accurately and comprehensively internalize it. Our "map" can never be a completely accurate represetnation of the territory without becoming the territory--omniscience. But I'll leave the theoretical cosomologists to fight that one out. A change of a couple of parts in ten billion over a few billion years means that for all practical purposes we can treat c as a physical constant. You don't have to know the precise molecular combustion pattern of an air-fuel mixture to know how many ergs are consistently produced by it.

We don't react well to weightlessness (1g acceleration would be nice, but how do you get that much fuel into Earth orbit?), not to mention cosmic radiation once we leave the magnetosphere.

You don't need acceleration for ship's "gravity." Centrifuging works just fine when you get to a large structure--and any manned interstellar vessel isn't going to be a tiny one. And we have excellent radiation shielding--though of course that adds mass.

Any effective shielding to prevent molecular decay and particle "strikes" on an interstellar vessel moving at any considerable fraction of c would have to be "field" shielding, not material. But that same "shielding" might be part of the drive, the "scoop" that gathers in matter for the jet. See Bussard ramjets*. If you have to carry all your delta-V as fuel, no point in starting. You can't carry enough. Gotta get at least some of that fuel along the way, and/or build up pretty substantial velocity before firing up the drive.

Impacting a few large ice asteroids onto Mars would be an excellent start on terraforming it.

[*--I believe there are a couple of minor factual inaccuracies in that article, but I'm too tired and busy right now to fisk 'em out.]

Posted by: Tully at July 8, 2006 01:06 PM

Tully,

Saw this, thought of you. :-)

Oh, for a time machine!

Posted by: Blue Jean at July 10, 2006 12:43 AM

Max,

Whatever the pluses or minuses of Joe Biden, no one should be particularly threatened by this guy in terms of Presidential aspirations.
Heard from one of his colleagues this weekend that his greatest difficulty is that he never had an unspoken thought. Makes you wonder how he ever got as far as he has.

Posted by: Cavalier829 at July 10, 2006 11:32 AM

Tully,

Lorentz transforms and Minkowski space? Phew! That's WAY ahead of me! Physics was never my strong suit anyway.

Now for a few words about telepresence.......Isn't that the shorthand for Sandra Day O'Connor's judicial philosophy? Dennis, now that she's retired maybe we should harness THAT for space travel.

Posted by: Cavalier829 at July 10, 2006 11:39 AM

It's beyond me too, Cav, but I can't see how to comprehend the details of relativity without them. Words don't do it. So I hit the point where I just have to put up with the rocket scientists saying, "Well, kinda, but not really..." when I toss out a paradigm. THat's where they head off into some foreign tongue I never studied.

Thanks, Jean! I can appreciate that article. Oh, if only I had a time machine....

Posted by: Tully at July 10, 2006 01:46 PM

One thing that's definite about the future if past history is any indication.... it will be both terribly surprising and terribly familiar at the same time.... there will be many things that are very similar to what we imagined...but they won't work in the way we expected them to at all.

As far as the possibility of future expansion in space, there are 3 big assumptions that we really need to realize ARE assumptions:

1) That it truely is not possible to travel faster then the speed of light. - You know it is entirely POSSIBLE that the fact that light is not affected by the relative velocity of the object it is eminated from is a unique property of LIGHT rather then a unique property of that particular SPEED. In short, the Theory of Relativity is not conclusively prooven.

2) That to travel between point A and point B one must neccesarly traverse all the points between the two.

3) That it'll actualy still matter that much to us if a journey between 2 systems takes 1,000 years.

Posted by: cengel at July 10, 2006 03:52 PM

Um, the rocket science guys tell me that you're wrong on [1] and [2]. Not on the speed of light thing (skipping the hypothetical but theoretically possible tachyon) but on the "property of light" thing. We say "speed of light" but c is actually "propogation of electromagnetic radiation in a vacuum," which is a different thing. Light actually moves slower in atmosphere and solids, for example. But c appears to hold firm for EM radiation, and for gravity as well.

Things (OK, subatomic particles) actually can and do move between two places without traversing all points in between. It's called quantum tunneling, and it's part of the basis for some of our advanced electronics. Once again, we're jumping past the bounds of what I can explain properly or even really understand without learning more math (math that might be beyond me), but it really happens. Not much help for space travel purposes--we're not subatomic particles.

"Relativity is wrong." You'd find Einstein being one of the first to agree with that. Why? Because like all mathematical "science," relativity theory is a descriptive construction. It's far better at accurately describing the physical universe than its predecessor, Newtonian mechanics, but that doesn't mean it's the end of the line, it's just a much better model. That by no means indicates it's the best model, or that we can ever truly achieve the best model. See earlier, about the map/territory problem.

Newtonian mechanics still works just fine for most purposes, despite being technically "wrong." As will Einsteinian relativity when we manage to one-up it. They're sufficiently descriptively accurate for the applications we use them for.

Posted by: Tully at July 10, 2006 05:26 PM

Tully,

Forgive me if I fail to be as certain about knowing the true nature of the workings of the Universe as you and your rocket scientist freinds. I just know that throughout human history we ALWAYS think we have a pretty good handle on how things really work....and we ALWAYS seem to be humbled to discover that we didn't have nearly as solid an understanding as we thought we had.

Furthermore, Newtonian physics had a big advantage, it was extensively and easly subject to emperical tests. Relativistic Physics really isn't to the same degree. We can observe things that APPEAR to make sense... but testing them extensively isn't really possible.

For instance, you can test whether when you throw a rock up in air it will fall back down. You CAN'T really test whether a rock that is traveling in an object at 60% the speed of light and recieves a force that would normaly accelrate 60% of the speed of light will max out at 100% the speed of light rather then 120%....because we can't figure out yet how to begin to approach accelerating it close to even a fraction of that speed. All we can do is observe how natural forces that do move at close to that speed APPEAR to function. Not really the same thing as extensive, controled mechanical testing eh?

Same thing for objects larger then sub-atomic particals moving from one point in space to another without passing through the points in between. We certainly know some things that WON'T work to make that happen..... but I don't think we've really even scratched the surface of thinking about things that might allow that to happen.

I'm NOT saying that it MUST follow that any of #1, #2 or #3 are false assumptions. They MAY prove to be entirely true and accurate for all practical purpose...... just that we don't know because they haven't been around long enough and we haven't had the technological gadgets sophisticated enough to put them to the test (or even really observe them well) to beat them up properly and see how well they hold up. Give us a thousand years....and if they still look pretty solid THEN I'll start to have the confidence in them that you seem to ;)

P.S. The "crystal spheres" theorists thought they had it all pegged to.... and they were the rocket scientists of thier day.

P.P.S. I'm NOT denegrating the rocket scientists. They are the best we have at understanding how the Universe works given the tools and body of knowledge we have available today. But they are neither omnicient nor infallible. In a couple thousand years we may be able to do things in practical usage that our rocket scientists today would describe as theoriticaly impossible..... just as much of our every day world today would seem like absolute magic or superstition to the most learned minds of 2,000 years ago.

P.P.P.S. Thanks for the info on the EM radiation and gravity. I was curious whether that held true for other forces (especialy gravity). The last time I looked into the subject (years ago) I didn't find any info on that. But again, that still tells us how certain forces APPEAR to behave...it doesn't tell us that ALL (or even) most forces MUST behave similarly. Stronger then it was before....but certainly not conclusive.

Posted by: cengel at July 10, 2006 07:00 PM

Recent work indicates that gravity also propogates at c. And there's been some extensive testing that confirms relativity as a general model, including the predicted behavior of EM radiation in curved space-time. But once again, the details are either over my head or someplace that my head doesn't go. You can find the details if you dig around. Like Newtonian mechanics, it works for now. Given better models, we can do more, or at least understand more.

The rocket science guys know their business. They'd be the first to admit that a quantum leap (snicker) in theory could produce results we think impossible now. Show 'em the leap, they'll start making the gizmos.

Check my last para. I think we're talking past each other a good bit and saying many of the same things from different angles.

Posted by: Tully at July 10, 2006 07:16 PM