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From	Message
brigadecommander 17-Apr-25, 12:54	a real story and a sublime one;www.youtube.com
mo-oneandmore 17-Apr-25, 13:48	Brig An amazing gift she has. And I've been trying to find more info. about that planet that the James Webb detected a gas signature that is only produced by organic processes on earth. It's a mere 705,400,000,000 miles (120 light years) away from earth. Man could reach the planet in about 201,334 years at a speed of 400,000 MPH (about the speed of the The Parker Solar Probe -- the fastest ever to date) en.wikipedia.org Wowee! Here we come, huh?
lord_shiva 18-Apr-25, 00:07	Missed Three Zeroes It’s 700 trillion miles, not 700 billion. But who does light years in miles? Astronomers measure in parsecs and convert to light years for laymen. Miles are s nonsense, but I saw the BBC reported it that way, not km or inches or furlongs.
bobspringett 18-Apr-25, 01:35	Shiva 00:07 <But who does light years in miles?> Spot on! I'm bemused by the American habit of stating large weights in 'so many thousand pounds' instead of tonnes or 'so many African Elephants'. Also talking about flood flows in gallons per hour. Why not cumecs (cubic metres per second), like engineers do. I remember an exercise when I was doing my B.E., where we had to calculate the maximum vertical speed of a cam follower. One wag gave the speed in furlongs per fortnight. At least he was alliterative. But I have to admit that it's easy to lose track of all them zeroes. I had to quadruple-check when I was writing the Argo Trilogy, calculating what accelerations in metres per second for how many seconds would result in what velocity as a fraction of lightspeed, and how far would be travelled in that time. And all that was constrained by the Rocket Equation, giving terminal velocity in terms of initial/final mass ratios and exhaust velocity. So I have some sympathy for those who drop a few orders of magnitude.
mo-oneandmore 18-Apr-25, 06:28	Shiva AI found the number to be 7.054 x 10^14 and I agree that I missed three digits. Bob: 120 light years is about 3.5 x 10^18 ft. 120 light years is about 4 x 10^19 inches 120 light years is about n x 10^n nanometers. 120 light years is about ... ... ...
mo-oneandmore 18-Apr-25, 06:47	Bob 120 light years = 1.135 x 10^27 nanometers. Shiva: 120 light years = 7.589 x 10^6 astronomical units = not that big of a number when compared the others. 120 light years = 1.20 x 10^2 light years
lord_shiva 18-Apr-25, 16:24	LOL Whenever I need to say “just a minute” I tend to specify, “just six times ten to the first seconds…”
lord_shiva 18-Apr-25, 16:43	AU Astronomical units form the basis of the parsec, a parallax of one arc second. You snap a photo of stars in the sky, wait six months, then take another photo of the same night sky. If closer stars shift one 3600th of a degree with respect to very distant points of light, you can use simple trig to get the distance. Six months equals the base of a triangle centered on the sun 2 AU long (one AU being the average Earth/Sun distance). With such a short base and long hypotenuse the hypotenuse and long leg are roughly equivalent in length. The math is complicated a little bit by the fact the sun is drifting one direction while the target star in another. We tend to ignore these factors as not being significant over the course of six months (half a year puts Earth on the opposite side of the sun). Anyway, tan(theta)=opp/adj. A theta of 1/3600° yields a distance (opp) of 206,265 AU. 3.26 light years.
apatzer 18-Apr-25, 19:00	If you were to count every mile (taking only one second per mile) for the entire 120 light years. It would only take you a meer 22,372,000 years to complete.
lord_shiva 19-Apr-25, 06:40	Voyager 1 This spacecraft is moving 38,000 miles per hour, which is about ten miles per second (a bit more). So it will have moved 120 light years away after a mere 2.2 million years, per Apatzer’s calculation. Gemini says one light year every 18,000 years, so 18K times 120… 2.16 million years. I’m satisfied his number is good.
mo-oneandmore 19-Apr-25, 08:03	Shiva Man has some formidable --- maybe impossible science to develop the speed that's needed to reach the stars, huh? And anti-gravity drive ain't gonna develop enough acceleration.
lord_shiva 19-Apr-25, 10:49	Antigravity Gravity isn’t bipolar, like electromagnetism. There is no antimass. Even antimatter exerts positive mass gravity. Electromagnetism does bend space, but in the same way mass bends space. Spacetime curves down, it never curves up. We cannot push space from the other side—at least—there is no credible theory for accomplishing that. We cannot push space push space from this side, but there s no way to pull space. And as you note, there is little between stars on which to grasp flat space for a decent pull (antigravity). There is, however, dark energy. Figuring out how to harness that could yield spacecraft a decent boost. It also explains the Fermi paradox. Tapping dark energy likely causes some sort of universal decay, in much the same way tapping fossil fuel accelerates global warming. So extraterrestrial intelligences that harness dark energy get eradicated by the overlord species protecting local spacetime from dark energy rips. A race advances, taps dark energy which reveals the danger they represent, and they get sterilized by the galaxy police. We have not observed dark energy tears in distant galaxies—at least not in ways discernible as such to us. This shows the dark energy monitoring force is effective in all galaxies with the capacity for sentient life. Anyone catch K2-18b?
lord_shiva 19-Apr-25, 10:59	K2-18b Oh, silly me. 120 ly. So this entire thread was about the 9 earth mass planet orbiting a red dwarf star where microbes may have been discovered. Any motile K2-18b life forms would be incredibly strong, given that world’s surface gravity. 11.56m/s2. That contrasts with 9.8m/s^2 here on Earth. So not all that much more. I had assumed a higher value.
lord_shiva 19-Apr-25, 11:03	Weight A 100lb Earthling would weigh 120 lbs on K2-18b.
apatzer 19-Apr-25, 16:50	Lord Shiva That's very interesting. I also had assumed a higher value. I don't think that microbes are effected the same way by gravity. I would imagine that on a 9 earth mass planet that animals would be smaller. But I guess that would really depend on the atmosphere. Before the Siberia traps eruption and especially before the Chicxulub impact event. The oxygen content in our atmosphere was much higher. Animals could therefore support a larger frame. I had often thought that one of the reasons for the mass die offs were due to the global firestorm as particulate matter fell back to earth from the impact. Had actually used up a tremendous amount of Oxygen.
bobspringett 22-May-25, 18:55	For a given density, the mass of a planet is proportional to the cube of its radius, and gravity is proportional to the inverse square. So surface gravity would be proportional to the radius, or cube root of the mass. A planet with 9 Earth masses and the same density would have a surface gravity of just over twice that of Earth. So where did the 11.56 m/sec2 come from? Or am I in error assuming the same density? Admittedly, Earth is the densest planet in our solar system, so it might not be typical of rocky planets and it's certainly not typical of ice/gas giants.
apatzer 22-May-25, 19:09	Bob Thats interesting, without looking it up. I would have thought Mercury would have been the densest. Also the earth has a larger than it otherwise would have been metallic core due to the collision and merger with Theia.
bobspringett 22-May-25, 19:28	Patz Mercury is almost as dense as Earth, due to its over-sized core. But Earth, being more massive, compresses its core and mantle more than Mercury.

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