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Comment: Re:Yes, nearby (Score 4, Informative) 242

by Gospodin (#30437110) Attached to: Super-Earths Discovered Orbiting Nearby, Sun-Like Star

That is an ion engine. My back-of-envelope calculations say that accelerating to .0002c and back to rest requires an Isp of about 5300 if you assume a mass ratio of 10:1. (Which is about as high as you can expect with current technology.) You can do a little better with staging, but not orders-of-magnitude better.

If you can improve your Isp to, say, 50,000, which is well beyond current technology, then you could accelerate to almost 0.002c. Relativistic effects won't be really evident until well over 0.2c (at that speed it's only a 2% time dilation). We're not close to rockets that can attain such speeds.

Improving the mass ratio is even less helpful, btw, since that's a logarithmic factor. An Isp of 50,000 with a mass ratio of 100 still only gets you to 0.004c. I suppose it's conceivable that an interstellar ship that needed almost no structure could have an extremely high mass ratio, but you can see how ridiculously high it has to be to matter.

The only way we're going to send starships at relativistic speeds is to use (i) some form of non-rocket propulsion, like solar sails or those reactionless Casimir-effect thrusters or some other exotic method, (ii) something with a truly enormous Isp. Current ion engine tech tops out at about 30,000 s, and even nuclear pulse tops out at 100,000 s.

Comment: Re:I can guess why IBM was pushing for IEEE 754r (Score 1) 158

by Gospodin (#30387610) Attached to: ECMAScript Version 5 Approved

Will these be accessible from ECMAScript? And will most programmers use them correctly?

If it's an implementation of 754r, then the answer to the first question is yes. As to the second, obviously I can't say.

Exactly, and that is why i think 754r is a stupid hack. Depending on it makes implementations more complicated without solving the problem it is set out to solve: Programmers that haven't done their homework.

With all due respect, 754r is not a stupid hack. It's a well-thought-out way to handle an exact datatype. From your other comment you seem to think having an exact datatype is useful, but perhaps you haven't thought through all the implications of that. (For example: take the exact number "1" and divide it by the exact number "3". What's the result? In 754r, it will be "1.33333" with some number of 3s, and will be flagged as being "rounded" and "inexact". So at least the programmer knows the number is no longer exact. Arbitrary-precision computations don't solve this problem.) 754r may not be perfect, but at least it's an effort to work through all the implications.

That said, including 754r in ECMAScript probably is stupid. It's pretty complicated, and wouldn't see all that much use. If it's really needed, code it up as an add-on library. (And provide ECMAScript with an easier way to handle... add-on libraries. Which I understand they're working on.)

Comment: Re:I can guess why IBM was pushing for IEEE 754r (Score 2, Informative) 158

by Gospodin (#30368174) Attached to: ECMAScript Version 5 Approved

First, it won't fix the stupid programmer bug. 754r can't guarantee exactness in every situation. For instance, (large_num+small_num)+small_num == large_num != large_num+(small_num + small_num).

Actually, 754r handles situations like these via exception flags. If large_num + small_num == large_num, then the "inexact" and "rounded" flags will be raised (possibly others, too; I haven't looked at this in a while), which the programmer can use to take some alternate logic. It's certainly true that stupid programmers can use these tools incorrectly (or not use them), but isn't that true of any system? Sufficiently stupid programmers can defeat any countermeasures.

Comment: Re:The answer is... (Score 1) 220

by Gospodin (#29453683) Attached to: New 'Drake Equation' Selects Between Alien Worlds

Whether dolphins are that way I'm not sure, but I think humans have definately [sic] hit a point where our current physical form can adapt to environments easily enough that there is not much natural selection to change us much from an evolutionary standpoint anymore (in essence we've become what the cockroach is: a supremely adaptable organism that can survive almost anywhere).

Considering how much evolution has occurred in humans in the past few hundred thousand years, an eyeblink on evolutionary scales, I think this assertion is far from "definite".

Comment: Re:Alien Web Profit (Score 1) 202

by Gospodin (#29111467) Attached to: Looking For a Link Between Sci-Fi UFOs and UFO Reports

The problem with the idea of creatures with lifespans millions of times longer than ours is that they wouldn't have had time to evolve. Or, if they had rapid reproductive cycles (human-scale) but very long lifespans, then (a) you have to wonder how that could have evolved and (b) how come they haven't overpopulated their planet yet? Might make for an interesting science-fiction novel background, but it's not very plausible.

The cyborg idea is a better one. Although for really long life, I think you'd have to ditch the biological component altogether.

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