Water found on a potentially life-friendly alien planet • Hacker News Board

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

#251

Post by healsjnr1 » Thu, Sep 12, 2019, 3:18 AM UTC

dylan604 wrote: post #221

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…

does this take into consideration that you would need to start slowing down halfway there?

It wouldn't need to be halfway. At 3gs acceleration, it would take about 115 days to accelerate up to the speed of light. You'd then travel ballistically for the majority of the journey before having to decelerate for another 115 days.

Given the total journey would be ~40,000 days the 230 days of acceleration probably isn't going to impact things too much. Even if you brought it back to 1g acceleration, it's still only around 700days out of 40,000.

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

#252

Post by jessaustin » Thu, Sep 12, 2019, 3:21 AM UTC

amelius wrote: post #65

ajconway wrote: post #18

Earlier quoted context omitted.

Theoretically, you can. At 0.99c 111 light years take about 15 years of ship time to travel.

And how much time will it take a person to reach that speed at human-safe acceleration? And how much energy would it take?

This paper has some interesting ideas. They want to manufacture really tiny black holes (radii of "a few attometers") and use Hawking radiation (which is inversely related to mass) to drive the vehicle. The black hole serves as both engine and fuel tank.

https://arxiv.org/abs/0908.1803

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

#253

Post by aussieguy1234 » Thu, Sep 12, 2019, 3:24 AM UTC

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

I think the keyword here is "potentially habitable"

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

#254

Post by Swizec » Thu, Sep 12, 2019, 3:26 AM UTC

jaco8 wrote: post #250

Swizec wrote: post #239

Earlier quoted context omitted.

You still get in trouble I think. Have any political regimes been stable enough in the past 222 yaers for the trust to survive? All of Europe has gone through multiple revolutions, USA was only 30 years old back then so you wouldn’t have considered it ... that leaves what, the UK? Any parts of Asia that survived since 1797?

With travel time that long , you have to consider technological advancement at home. Just imagine that you look out of your window after travelling for 70 years and there is this other ship overtaking yours with ease.

Going down in history as "First to leave, last to arrive". Brutal

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

#255

Post by BurningFrog » Thu, Sep 12, 2019, 3:34 AM UTC

petre wrote: post #249

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

It isn't habitable even if it's a super Earth because the gravity would be 8g if it's 8x the mass of Earth.

That's not how it works. The moon is 1% of Earth's mass, but has 16% of our gravity.

I'm not entirely clear on the deciding factors, but it's probably mostly density.

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

#256

Post by ddingus » Thu, Sep 12, 2019, 3:47 AM UTC

gisely wrote: post #242

vermilingua wrote: post #238

Earlier quoted context omitted.

> when we get faster than light travel FTL requires numerous things to be true about our universe, that all signs say are not.

The speed of light is just a compute constraint imposed on the physics simulation that is our universe. If we can just get the gods who are running that simulation to give us a little extra compute time in our neck of to woods then we can all be galactic explorers.

Maybe there are glitches possible.

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

#257

Post by ddingus » Thu, Sep 12, 2019, 3:49 AM UTC

glup wrote: post #240

vermilingua wrote: post #238

Earlier quoted context omitted.

> when we get faster than light travel FTL requires numerous things to be true about our universe, that all signs say are not.

...crushing all my dreams of being a starship captain, thanks.

I am reading big space operas right now.

What we know of this reality is so limiting compared to what we can imagine.

Good dreams. Many of us have them.

I also like to dream the knowable remains much larger than the currently understood too.

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

#258

Post by 0xffff2 » Thu, Sep 12, 2019, 3:52 AM UTC

fwip wrote: post #202

0xffff2 wrote: post #143

Earlier quoted context omitted.

Currently we have no known materials that would actually survive a 111 light year trip to another solar system, so that fact that we can't actually build the space elevator when we get there seems irrelevant. They're both roughly the same order of magnitude of impossible with our current technology.

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 system intact enough for the device to actually function.

Still a bit wishy-washy since it involves magical technology that we have no idea how to build, and if we had the communications technology we would probably have the materials science too, but hopefully that gets the point I was originally trying to make across.

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

#259

Post by roywiggins » Thu, Sep 12, 2019, 3:54 AM UTC

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…

N=2 means that we now know how to detect more than the one we are standing on, so it says a lot about how many we might expect to find soon.

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

#260

Post by 0xffff2 » Thu, Sep 12, 2019, 3:56 AM UTC

mrkstu wrote: post #179

0xffff2 wrote: post #109

Earlier quoted context omitted.

>If you go straight up far enough you’ll be out of Earth’s gravity well. While you could theoretically do this by accelerating directly up, You still have to accelerate somehow.

Understood, but somehow the discussion ended up around achieving orbital velocity instead of escape velocity (the one relevant to the original sub-thread topic), two very different numbers (though escape velocity is ultimately a higher number.) https://physicsabout.com/orbital-escape-velocity/

Sure, but they're not orthogonal at all. One is just a lot more delta-v than the other. It's the same basic thing. Point the rocket nozzle in the opposite direction that you want to go and turn it on (modulo the fact that the "direction you want to go" might not be intuitive because orbital mechanics).