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

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

#51

Post by hinkley » Wed, Sep 11, 2019, 8:54 PM UTC

yellowapple wrote: post #35

transreal wrote: post #2

With a planet this large, visiting it would be a one way trip due to the "The Tyranny of the Rocket Equation" [0]. I'm looking forward to the day we start finding exo-planets that are closer to Earth in size and which could potentially have space-faring races (and which we could leave if we were ever to visit them). [0] - https://www.nasa.gov/mission_pages/station/expeditions/exped...

I wonder if we could work around the stronger gravity by using a spaceship as the anchor for a space elevator or skyhook? Both of those technologies are pretty far off, but so is getting humans to another star system.

As gravity increases the tensile strength necessary for the elevator increases. We haven't even figured out how to mass produce materials that would suffice for an elevator on earth yet.

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

#52

Post by dkural » Wed, Sep 11, 2019, 8:57 PM UTC

DidISayTooMuch wrote: post #46

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.

Wait, is this correct? Doesn't 111 light-years mean even light takes 111 years to travel through? And light travels at 1c.

Light does not experience time at light speed - it is stuck in a static moment. So from our stationary perspective, light takes 111 years to come from a 111 light year distance, but from light's perspective it takes an instant.

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

#53

Post by yawz » Wed, Sep 11, 2019, 9:00 PM UTC

atoav wrote: post #31

Swizec wrote: post #22

Earlier quoted context omitted.

So you can survive the trip but even if you come back home, it’s not home anymore? Imagine leaving 222 years ago and coming back now ...

Many european cities would still exist and the mountains I grew up in front of too. But granted, all people I know would be dead and some I could find in the history books maybe..

> and some I could find in the history books maybe..

Where you would also be, at that stage.

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

#54

Post by cthalupa » Wed, Sep 11, 2019, 9:01 PM UTC

transreal wrote: post #2

With a planet this large, visiting it would be a one way trip due to the "The Tyranny of the Rocket Equation" [0]. I'm looking forward to the day we start finding exo-planets that are closer to Earth in size and which could potentially have space-faring races (and which we could leave if we were ever to visit them). [0] - https://www.nasa.gov/mission_pages/station/expeditions/exped...

I mean, as far as I am aware, that problem is due to the propulsion method. Would a nuclear based rocket not be able to solve this issue? My understanding is that it would.

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

#55

Post by t3f » Wed, Sep 11, 2019, 9:02 PM UTC

Swizec wrote: post #22

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.

So you can survive the trip but even if you come back home, it’s not home anymore? Imagine leaving 222 years ago and coming back now ...

I would recommend reading Noumenon by Marina J. Lostetter if you'd like to scratch that theoretical itch playing out one specific way.

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

#56

Post by gdubs » Wed, Sep 11, 2019, 9:02 PM UTC

dkural wrote: post #52

DidISayTooMuch wrote: post #46

Earlier quoted context omitted.

Wait, is this correct? Doesn't 111 light-years mean even light takes 111 years to travel through? And light travels at 1c.

Light does not experience time at light speed - it is stuck in a static moment. So from our stationary perspective, light takes 111 years to come from a 111 light year distance, but from light's perspective it takes an instant.

Every time I think I’m closer to understanding matters of time and space...

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

#57

Post by yourbandsucks » Wed, Sep 11, 2019, 9:02 PM UTC

kadoban wrote: post #42

yourbandsucks wrote: post #37

Earlier quoted context omitted.

Orbit isn't a height, it's a speed. 7 km/sec for low earth orbit. A balloon floating you higher while not making mach 20 isn't much of a shortcut.

How poor of a shortcut is it? I'm not really clear on what the math would look like. Would it just be better by approximately the ratio of gravity's strength at the surface vs the height of the balloon?

Basically just saves what you would've lost to wind resistance and gravity while getting to that height, while adding the complication of accelerating from 0 to orbital before falling back into the atmo.

Space elevator ideas usually have the hop-off point all the way out at geosynchronous orbit to solve the velocity problem. Which is.. a really tall elevator.

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

#58

Post by warent » Wed, Sep 11, 2019, 9:03 PM UTC

dkural wrote: post #52

DidISayTooMuch wrote: post #46

Earlier quoted context omitted.

Wait, is this correct? Doesn't 111 light-years mean even light takes 111 years to travel through? And light travels at 1c.

Light does not experience time at light speed - it is stuck in a static moment. So from our stationary perspective, light takes 111 years to come from a 111 light year distance, but from light's perspective it takes an instant.

Yeah, the experience of time to travel a distance approaches zero as your speed approaches the speed of light. It's really crazy to think about.

It is worth adding for the sake of clarity that light has no perspective or frame of reference because photons are non-inertial.

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

#59

Post by dsfyu404ed » Wed, Sep 11, 2019, 9:03 PM UTC

TheOtherHobbes wrote: post #27

transreal wrote: post #2

With a planet this large, visiting it would be a one way trip due to the "The Tyranny of the Rocket Equation" [0]. I'm looking forward to the day we start finding exo-planets that are closer to Earth in size and which could potentially have space-faring races (and which we could leave if we were ever to visit them). [0] - https://www.nasa.gov/mission_pages/station/expeditions/exped...

Surface gravity will be around 2g, so even if it has a rocky surface it's not going to be a very comfortable home from home.

So a 150lb person will weigh 300lb. Sure that's gonna suck on day one but there's plenty of people who weigh that much who get by. Without all the health complications from high body fat it wouldn't be that bad. You'd probably die young but I don't think that would bother people.

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

#60

Post by hinkley » Wed, Sep 11, 2019, 9:03 PM UTC

jerf wrote: post #48

hinkley wrote: post #26

Earlier quoted context omitted.

I made it well into this decade before I was made aware of this fact. It's kind of a shock, still. At some point your planet is massive enough that you can't get into orbit with chemical rockets (even, I think, by flying them up like Burt Rutan?). The implications for the Drake equation are pretty big. Rockets without any promise of ever being able to break orbit are good for what, war? Would you keep developing them…

"At some point your planet is massive enough that you can't get into orbit with chemical rockets (even, I think, by flying them up like Burt Rutan?)." Nuclear rockets don't seem to be very hard. They're somewhat dangerous if they explode, but they aren't very hard. Fairly solid prototypes were built decades ago and there's little to suggest they couldn't have been made production-grade [1]. We'd have them now if we d…

Do solids settle out of air on a high gravity environment faster? The air would be thicker. Does gravity or buoyancy win than tug of war?

I spent a day once trying to figure out what the Bronze Age would be like for marine creatures. Oxidation is less of a problem but galvanic action is huge. Fire pretty much doesn't work, which blocks a whole bunch of precursors like ceramics.