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Water found on a potentially life-friendly alien planet

nationalgeographic.com

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Re: Water found on a potentially life-friendly alien planet

#391

Post by numerobis »

tunesmith wrote: post #204

I got into the Wait Calculation[1] a few weeks back and made a Jupyter notebook out of it. At our current max speed (692,000 km/hr, stated max speed of Parker Space Probe), it would take about 173,000 years to get to that planet. We could instead choose to Wait and grow our tech. By picking a constant annual growth rate and then doing some calculus to find the minimum, we can calculate the shortest possible time it w…

Why don't you stick to the energy growth rate (instead of the 4.72% velocity growth rate) and then use the relativistic formula of the kinetic energy (in which the relationship between energy and velocity is not quadratic — the quadratic approximation is valid only for small velocities)?

Re: Water found on a potentially life-friendly alien planet

#392

Post by bestest »

simon1573 wrote: post #305
vermilingua wrote: post #275

Earlier quoted context omitted.

Anything in the Culture series by Iain M. Banks; The Expanse series by James S. A. Corey; The Commonwealth and Void trilogies by Peter F. Hamilton, and the Night’s Dawn trilogy also by Peter F. Hamilton; The Dune saga by Frank Herbert.

Is Pandoras Star worth the effort?

Yep, the Commonwealth series got solid 4s out of 5s from me, which is very good — I very rarely give a book a 5.

Re: Water found on a potentially life-friendly alien planet

#393

Post by fwip »

0xffff2 wrote: post #258
fwip wrote: post #202

Earlier quoted context omitted.

Sure we do. Chuck a rock in the right direction, it'll still be a rock 111 light years later.

Okay, I should know I have to be 100% pedantic when discussing these kinds of topics, so that's my bad. I amend my claim to the following: Assuming we could generate a sufficiently focused laser or other communication mechanism to communicate over 111 light years (which we can't), currently we have no known material that we could build the comm device out of that would survive a 111 light year trip to another solar s…

Thanks for the clarification :)

Re: Water found on a potentially life-friendly alien planet

#394

Post by dodobirdlord »

solipsism wrote: post #244
dodobirdlord wrote: post #243

Earlier quoted context omitted.

In this case N=2 is very different from N=1. The probability of detecting further Earth-like planets is not influenced by the existence of Earth, because what we're actually measuring is the conditional probability of detecting Earth-like planets given the existence of Earth, which already factors Earth in. In this case N=1 is a lot more like N=0 and N=2 is a lot more like N=1.

That's silly. The type of world we're interested in is ones that could support life as we know it. We knew one of those exists. We're trying to find more.

Calling it silly seems a bit harsh, it's just statistics. We are interested in knowing the frequency of earth-like planets existing. If we assume that the existence of earth is a pre-condition for life existing and performing the measurement, then the existence of earth tells us nothing about that frequency. Regardless of the frequency in question the count of earth-like planets starts at 1, because in scenarios where the count is at 0 the measurement is not being performed. There could be millions of earth-like planets in the milky way, or there could be only one, or earth could even be the only life-supporting planet in the universe. There is no mechanism given only the existence of earth to reason statistically about the distribution of earth-like planets.

Whereas finding a second one tells us a lot. So that's why I say we are in more like the N=0 case, and that finding a second earth-like planet puts us in the N=1 case.

Re: Water found on a potentially life-friendly alien planet

#395

Post by perl4ever »

heavenlyblue wrote: post #339
bakuninsbart wrote: post #322

Earlier quoted context omitted.

Could you give some sources for that or explaing where exactly the problems in fusion technology lie and how it could be solved by throwing money at it?

ITER is planned to be completed in 2026 and it'll generate a net 0 of electricity at 300MW in/out. It seems the issue with fusion is that it actually works much better at scale. But the same could be said about nuclear reactors - it obviously is much harder to build a compact one.

Does it work better at scale? The sun definitely produces a lot of energy in total. However, "the Sun's "power density" is "approximately 276.5 W/m3, a value that more nearly approximates that of reptile metabolism or a compost pile than of a thermonuclear bomb".

If, overlooking the details, we were able to build a cubic meter sized "fusion box" that outputs 276W, then it would take about 2 million of them to produce a reasonable output for a power plant of 600MW. And it would take up about half the volume of NASA's vehicle assembly building, ignoring any support structure needed. That's not unimaginably huge, but it's pretty large compared to other types of power plants, I would think.

So assuming we solve all the technical problems to capturing the power source of the stars using handwavium or perhaps generously donated alien widgets, I wonder if it might still be uneconomic.

Re: Water found on a potentially life-friendly alien planet

#396

Post by perl4ever »

klyrs wrote: post #375
bestest wrote: post #368

Earlier quoted context omitted.

Not quite true. You'd spend half of the travel time under 1g accelerating, then the ship does a 180 degree flip in 0g, and then you spend another half of the travel time under 1g decelerating. Edit: Of course, at constant 1g acceleration, at day number 354 we reach 1c. Don't know if we should start coasting before we reach 1c or just the hell with it and see what happens if we keep accelerating.

So many people in this thread are acting like constant acceleration is possible. Unfortunately the faster you get, the more energy it takes to maintain constant acceleration. > Don't know if we should start coasting before we reach 1c... Don't worry about it. Your rocket would need to expend an infinite amount of energy to accelerate to c. The energy stored in your finite-sized rocket is finite. At a certain point it…

"Unfortunately the faster you get, the more energy it takes to maintain constant acceleration."

I'm not sure what you mean by this. You could also say "the slower you get, the more energy it takes to maintain constant acceleration". Constant means ongoing, so as long as it is constant, you are going to have to expend more energy.

Unless you mean that somehow, you could determine your absolute speed by how much you accelerate for a given expenditure of energy, but wouldn't that violate relativity?

Re: Water found on a potentially life-friendly alien planet

#397

Post by perl4ever »

solipsism wrote: post #199
saagarjha wrote: post #193

Earlier quoted context omitted.

The point is finding planets aside from our own .

Sometimes N=2 is extremely different from N=1. Specifically when we have N=1 and we suspect that it might be unique, or extremely rare to the point that you wouldn't expect to find instances. Sometimes N=2 is not that different from N=1 though. Specifically when you don't think the situation is necessarily that rare, you just don't have a big population to choose from. That's the situation here. Astronomers expect to…

Just as an aside, Facebook is useful to demonstrate the Birthday Paradox. Even if you don't know that many people.

Re: Water found on a potentially life-friendly alien planet

#399

Post by perl4ever »

tripzilch wrote: post #342
brownbat wrote: post #220

Earlier quoted context omitted.

> Being in the “habitable zone” doesn’t mean a planet is habitable True. Being a spooky near twin of Earth isn't necessarily enough. The air inside popcorn factories is basically identical to the Earth's atmosphere, but breathing in diacetyl, a butter flavor you'll find in that air, will kill you a few months or years later. Popcorn lung really undermined my naive view that we would one day be able to run a scan or a…

That'd be something, people travel for 30 years to a distant planet, die four days later because something in the atmosphere we didn't account for and did not filter properly, or a crystalline fungus that eats away our suits.

Happens a lot in (bad) science fiction, and parody thereof.

People land on a planet, go "I wonder if the atmosphere is breathable?", then open their helmet and take a deep breath.

But I think by the time anyone is arriving on a planet around another star, it will be with biotechnology that allows adaptation to a rather wide variety of environments.

Re: Water found on a potentially life-friendly alien planet

#400

Post by perl4ever »

Tepix wrote: post #310
manicdee wrote: post #134

Some caveats per Marina Koren https://twitter.com/marinakoren/status/1171873631808438273 1. This planet probably doesn’t have a solid surface 2. Being in the “habitable zone” doesn’t mean a planet is habitable 3. The detection is of water molecules, chances are the water only exists as vapour in the atmosphere of this small gas giant. 4. If you ask 10 astronomers about this you will get 11 opinions

> 2. Being in the “habitable zone” doesn’t mean a planet is habitable Related question: Does "habitable" mean "habitable for humans"? I thought it didn't, but after reading some dictionary definitions, i believe it does. On the other hand looking at the planetary habitability wikipedia page it's clear that it means "life-friendly". No wonder many people are confused. Of course a planet with 8-9 times the mass of eart…

People have commented that a planet a bit larger than earth (I think 8-9 times qualifies) would have gravity too strong for rockets to ever be practical, and thus whether you were a marooned earthling or evolved there, you would never ever be able to get into orbit.

So, there could be "super-earths" with life similar to ours, even intelligent, and they would never be able to participate in a space-faring society.

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