[quote=“Astrid, post:19, topic:47669, full:true”]
A awful lot ofvplanets out there
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I am aware of the estimated number of stars and planets.
How many are habitable?’
How many have remained habitable for billions of years?
How many also have the chemical make up for civilizations to thrive and make technological advances?
I think this number would be pretty small considering how many factors have to line up but there are just way too many unknowns to know for certain. Maybe once we fully map out life’s origin here we’re can better estimate it.
Yes there is a host of critical, heavy elements required for advanced life. We probably even want certain ratios (not too much, not too little!). So not only do we need these neuron star collisions but we need many stars to have gone nova and we want the right mix. We obviously won’t form and evolve in a solar nebula, so we are talking multiple generations of stars, of which our sun is a third. That is why I enjoyed @Dale’s link. The universe is as small and as young as it could be for us to exist right now. No wasted space or time. The universe itself is in the goldilocks zone in terms of its development for advanced life!
I know countless people --as @Astrid did-- point out the large number of planets but I think a lot of them can be excluded pretty easily from harboring advanced, self aware life that has evolved though natural causes. “Rare earth” for me but not dogmatic. I get the impression Hugh Ross overstates things but I think there is some truth to this: “In elliptical galaxies, star formation ceases before the interstellar medium becomes enriched enough with heavy elements. For life, stellar systems need to form late enough that they can incorporate this heavy-element-enriched material." Excerpt From: Hugh Ross. “The Creator and the Cosmos: How the Latest Scientific Discoveries Reveal God.” Apple Books.
Some galaxies are not good places to look for advanced life (contra the 2015 study). I remember reading Hugh Ross’s long lists of fine-tuning constants and also things about the earth and galaxy that need to be just right for advanced life to form in The Creator and The Cosmos which was updated in 2018. Again, I think it is overstated a bit and some might influence others but I think the gist of his point is clearly made. There is a lot more to it than having water and not being too close or far from the sun to have advanced, intelligent life. Things really lined up nicely for human life to exist on this pale blue dot…
Although there is some correspondence between the time of the last plague and departure and the the week of the feast of Unleavened Bread, the total events took rather longer. The bitter oppression commemorated in the bitter herbs had lasted for rather more than a week, for example.
Total Planets? Or do you mean earth like? There are in all likelihood, via statistical extrapolation, plenty of planets that would fall in the “habitable zone” (porridge is just right!) but that is only one parameter necessary for advanced life. Please understand I am not taking about any type of life but life that needs to survive and evolve to much higher complexity over long periods of times.
Yes but how many narrowly defined parameters need to line up to have a planet capable of supporting the evolution of advanced intelligent beings over possibly billions of years? We need to be able to compare the sun total of those parameters with the sum total number or planets and see what we end up with. Both sides are speculative and not fully mapped out and there is no certainty to be had.
Also, there is no need to fear advanced civilizations unless it’s actually possible for entire space ships and advanced beings to travel faster than light. Our best science now tells us space travel is largely limited to within solar systems and even that is slow. Space is too big and the current maximum speed in the universe is C (light).
I also wonder how long it would even take to safely accelerate an inertial being to the speed of light. It’s an easy calculation. Just have to assume an acceleration. You would need to decelerated just as long. Maybe I’ll do it later.
Vinnie
Klax
(The only thing that matters is faith expressed in love.)
28
Even if we’re the only intentional species ever, in the entire dying insignificant, infinitesimal universe of 10^24 worlds, none of which we can possibly travel to (cause and effect can only travel at c at the most, ever, and nothing significant can be artificially propelled outside an atom smasher to even 0.1% c) let alone 0.1) let alone inhabit but one for less than a million years, for the rest of its 10^100 years, we evolved. That much is absolutely certain. Of course there are trillions of rare earths. They are extremely rare at 1:1,000,000,000,000,000,000, but that takes us to a trillion. The same for the infinity of universes from eternity.
And don’t worry @Astrid, contact is obviously absolutely impossible.
If you want the acceleration manageable long-term for humans (<~1.5 gees), probably something like 6 months to a year, but the fuel required would be ridiculous. Ion propulsion might be able to manage ~50 years.
From the rearranged definition for acceleration: Vf = Vi +at where assuming we start from rest and initial velocity (Vi) = 0, we end up with t = Vf / a
Vf = C ~ 300,000,000 m/s
A = 15m/s^2 (~1.5g)
t = 20,000,000s or about 231.5days (236 if I use less rounded versions of C and g).
So yeah, two thirds of year of experiencing an acceleration of 1.5gs just to get to light speed. Then the same of course to break if you can decelerate at 1.5gs.
We can get distance traveled via Vf^2 / 2a = about 1.9x10^12 mi. which is about a third of a light year (5.88 trillion miles). Congratulations, if you were leaving earth, and somehow managed to get to C, despite all the problems inherent in that scenario, in 4 more years you will make it to Promixa Centauri, our nearest celestial neighbor. At least you get three stars in one and some potential exoplanets in the “Goldilocks zone!”
Also, the ship can at least simulate artificially gravity because it can be designed so everyone is “sideways” or the direction in which you stand parallels the direction of motion. As you said, how much fuel would be needed? How does the mass increase work? The whole system will exponentially increase in mass as you approach C. This requires a larger applied force to maintain the 1.5g acceleration and at some point your energy needs will become infinite as we know with single particles in accelerators. So getting to c hypothetically with kinematics equations is not actually getting to c. So assuming your fuel’s force output is the same, the increase in mass means it would take far longer. Your fuel’s thrust will presumably have to increase the whole time to account for mass expansion.
Another good question here is to figure out how much time will have elapsed on your home planet given your speed is approaching c and we have time dilation just to get to to light speed, not to mention the rest of your trip. This will only get worse as you travel though. An alien civilization is certainly not going to come visit us then return “home” later. All their loved ones and the world as they knew it would be long dead!
For avoiding too much mass increase but going fast, something between 0.5c (y=1.15) and 0.8c (y=1.67) would be good. The thrust required for a ~1,000,000 kg craft to accelerate at 14 m/s is about half that of the first stage of the Saturn V. Except this has to run for 20,000,000 s instead of 168 s. Which means, if it ran on kerosene and liquid oxygen, the way Saturn V did, it would need 200,000,000 kg of fuel. Which would need 4x10^12 kg of fuel, which would need… Kerosene and Liquid oxygen doesn’t have a high enough thrust-to-weight ratio to work. A laser run by a nuclear reactor might. If the laser is about 10MW, then the nuclear reactor would only need to be about as powerful as the ones on nuclear submarines. Which would be light enough to fit on this ship. Firing a 10 MW laser at the launch pad is probably a bad idea, given that 1 MW lasers are used for missile defense systems. If the beam is 5 arcminutes wide, then it has to be about 3x10^10 m away to match ambient sunlight. We should avoid pointing this at random other things, too. 500 s is long enough that we could turn so the laser is pointed away from earth. 5 GJ going into the launch pad would be about like hitting it with two Tomahawk missiles.
This is, I believe related to the fact that the Old Testament is written in Hebrew, Adam and Eve are Hebrew names, and Hebrew did not exist as a language at the time period a historical Adam and Eve would have lived. Abraham didn’t even speak Hebrew.
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Klax
(The only thing that matters is faith expressed in love.)
36
We’ll never, as in never, have lasers that powerful. Batteries of nuclear powered ones might stop SL&ICBMs. If you have a spare $1TN to waste. For one battery to test against actual SL&ICBMs. Which, of course could start WWIII alone. Better nuke 'em before we can’t and they can.
The only anti-woo propulsion system that will ever work for humans to go Star Trekkin’ is ‘aitch bombs. Proving Fermi wrong for the right reason again. Stars are very, VERY, VERY noisy which is why we’ll never, as in never, pick up the neighbours’ Neighbours either.
That would either start running into the endless feedback loop if you try to get something up to ~0.7 c, or would require accelerations that are way too high for humans to handle.
We have ones that are CW and about 100 kW, but we don’t try running them for months at a time. Also, the cooling system needed would be rather better than anything we’ve developed. If we decrease the mass to about 1,000 kg (post-launch), ignore the “human passengers need to survive” part, then we might be able to use a 100 kW laser to accelerate it up to ~0.7 c over ~25 days. More realistically, we could use ion propulsion to accelerate small spacecraft up to that speed over the course of a few decades.
Klax
(The only thing that matters is faith expressed in love.)
40
I’m sure we will, but they’ll be unmanned national vanity projects next century, by India and China, for close ups of Proxima Centauri in a century. How long can a fission plant with no moving parts run for? A few decades at most.
