I didn't wrangle the lower limit that way -- it just fell out. If it hadn't, perhaps I couldn't be typ
The asymmetry in time dilation, as exhibited by the twin paradox, is actually not a result of the acceleration and deceleration. It's the result of the travelling observer taking measurements in more than one reference frame. If you use the correct Lorentz transform, t'=gamma*(t-(v*×/c^2)), you can show that the travelling observer really does experience less time passing.
On new propulsion https://www.scientificamerican.com/article/the-good-kind-of-crazy-the-quest-for-exotic-propulsion/ NIAC, though, is all about new ideas. The program functions as NASA’s venture capital arm, in that it supports technologies that might pan out, big-time. “Crazy” stuff, according to Jason Derleth, NIAC’s program executive. Derleth? Hmmm. Augie's progeny?
Even if these ideas don't immediately pan out - you can often learn something, just from "tinkering"...
Perhaps a better target or two? https://phys.org/news/2019-08-planets-orbiting-teegarden-star-earthlike.html https://arxiv.org/abs/1906.08783 A way to power probes? www.spacedaily.com/reports/Russia_Unveils_Ambitious_Project_for_Laser_Recharging_of_Satellites_in_Orbit_999.html
I don't think that Woodward's MEGAdrive can be dismissed too quickly yet. I don't want to repost anything that the authors don't want spread around yet, and it sucks to be a rumor monger, but I don't think the case is shut on the Woodward Mach Effect drive at all.
I hope so. I got my hopes up with the Breakthrough Propulsion Physics Project (BPP) https://academickids.com/encyclopedia/index.php/Breakthrough_Propulsion_Physics_Program The universe does have a cruel streak--pulsars that simulate radio beacons. I wouldn't be surprised if there were a new state of degenerate matter that could perfectly replicate the first five minutes of an I Love Lucy episode--and make us think ET was playing our TV programs back to us.
^ While not impossible in the grand scheme of things, highly unlikely. In that case there IS a planet with sentient clipboards that walk around with legs and arms.
I kind of like his QI theory but I dislike the abbreviation of "to", "for", and "are" to "2", "4", and "r" in his tweets. I believe McCulloch has also proposed an FTL drive based on QI theory but I don't know enough about it to spot any flaws in its conception. ETA: Mike McCulloch's blog mentions an asymmetrically accelerating horizon approach to generating thrust. It sounds like a plausible and testable mechanism. https://physicsfromtheedge.blogspot.com/?m=1
If i am not mistaken he began looking at the problem from the Flyby Anomaly. Flyby Anomaly still seems the best way, to me, to test many of these assymetric-thrust ideas. The former needs to be looked at anyway, whether it involves the latter, so why not handle two matters at once.
Well - that article certainly was interesting and it does make a bit more sense than some of the weird "explanations" (aka a form of hand wavium) that some in the science community have used concerning Quasars...
I love nuclear propulsion. I have a book on the Orion project which is fascinating as we cane so close to bypassing puny chemical rockets and going straight to nuclear propulsion in the 1960's. The nuclear test ban treaty killed it. Plus the fallout from the early designs was pretty bad. Still the modern ideas seem pretty solid but as the uninformed public are scared of anything with the word "nuclear" in it. Fact is. If we are going to have a hope in hell of man going beyond Mars then nuclear is pretty much the only way to go. So we need to get over this fear.
The Nuclear Salt Water Rocket should be smoother than Pulse Orion--but would have more of a stagnant heat problem This made me wonder: https://www.nextbigfuture.com/2015/02/confirmation-of-ultra-high-energy.html It is the first time I have heard the term "chemonuclear"
https://www.wired.com/story/mach-effect-thrusters-interstellar-travel/ a good write up from yesterday . Woodward and Fearn are now claiming a breakthrough and thrust is visible to the naked eye on the Mach thrusters.
Correction - our radio signals aren't made (eg, strenghtened) for interstellar travel. Most of them decay by 1 to 2 LY. So I doubt anyone has heard us, or heard anything coherent. Conversely, it's doubtful we're gonna hear anything. Even a concentrated, powerful, repeating signal that accounts for decay could had been sent...and missed us to due the slightest error, was recorded and never acknowledged as repeating, or came when we couldn't detect it. It's very possible that civilizations also advance quickly beyond radio for mass communication for something else, like laser communications and fibre optics. Not totally, of course - wifi comes to mind, no? - but enough that the 'buzz' around a solar system would decrease. And if anyone was watching for long enough, they might chalk it up to just stellar or planetary phenomena than something technological. We just won't know until we lob a probe or a ship to Proxima, Alpha, and Beta Centauri and check all the worlds of note there. And who knows? Maybe something is alive under a thick Psuedo-Venusian or Psuedo-Titanian atmosphere. Maybe they're oceanic, or exist under the ice. To them that might be all there is, unless they get rocketry and poke above their atmospheres. Maybe they're in massive tunnel systems after nuclear or biological or natural disaster. Our local neighborhood is REALLY big. Even just the Local Bubble alone. I don't doubt there's alien civilizations out there. But if radio signals decay at 2 ly, and even directed signals have a low chance of being recieved, we have to rely on telescopes and sub-relativistic laser-communication probes, and those might not get back results until the higher end of this century, if we even launch any this century: this might be a very Mars and Venus and Titan and Callisto focused century, which is fine - but it does mean we're not looking far out, and most of our scopes and missions might go to Centauri, Bernard's, maybe Wolf or something of that nature. But what about, say, Xi Bootis? Procyon? Tau Ceti? 82 Eridani? Omicron 2 Eridani? Epsilon Eridani? Van Maanans? Fomalhaut? Epsilon Indi? Delta Pavois? Sigma Draconis? 61 Cygni? Vega? Gliese 1061, Gliese 876? Gliese 892? These are all within or close to 20ly alone. And further beyond.... I'm a bit optimistic. Maybe something 'reset' the local area so we're not too disparate in technology. Or maybe everyone uploads into a artificial universe defended by drones. Or maybe some are cavemen, some are angels. Maybe the technology plateau is close by, real soon - No fusion, no ftl, nothing fancy than maybe cybernetics and electric cars - or maybe we're on the cusp of breaking new fields and rewriting the laws we know. Until we get out there and check, even with just probes to report back in 120 years, we can't really say. And even then, we're looking at basically a 'sector' of space 20-30LY wide. Big, but far from the galaxy. Maybe the forerunners migrated to the galactic core to make a super energy rich cluster of computorium brains to live in. Maybe they run around the galaxy, running from each other to avert mutual destruction. So on and so on. But I really doubt that at this time, there's not some counterpart to us writing a similar topic on similar technology in a similar world around a similar sun. Even if they're on the direct opposite side of the galaxy and thus we won't know, I think the math of just, how many exoplanets, even earth sized, around a g class star, in the goldilocks zone, is estimated to be what - in the millions alone? I doubt they're all just empty and waiting for us to terraform the ones closest to us in time. We have to overcome the cruelest speed limit there is - .C. Even relativistic speed is a pain to get to, probably only achievable by antimatter rockets or laser boost beams. Communications take years. Travel on the timetable of decades. And if that's the best we got, then no wonder we don't see galactic civilizations, interstellar organizations, what have you. Civilizations probably aren't driven by pure mathematics to explore, expand, exploit, exterminate forever, if a civilization can unite at all to begin with. Loads of them probably fall into ennui or virtual bliss. Many may have energetic phases, then grow stagnant and inwards looking for decades, centuries, millennia. Many may want to reach out but don't, due to their own economics, politics, religion, culture, so on. Maybe they lay down wormholes, stick to what they know. Maybe they do meet a neighbor, and wipe each other out, or damage each other to be functionally extinct or non-technological soon enough, blasting their worlds with interstellar or interplanetary artillery and diverted asteroids and drone warfare. And they all live, grow, build, decay, die - nothing lasts forever. No civilization, no technology, no species. All we can say right now is that they're not here, and the galaxy does not seem to be converted into anything organized of a technological nature. We can say that as far as we know due to the light lag, the core hasn't been converted into a massive energy apparatus, and no dyson spheres or big megastructures exist, as far as we can see, at least within 100 Lightyears of us or so. Other than that, the game's afoot, really.