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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

#191

Post by flukus »

nothis wrote: post #173
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'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). I just realized I have no real concept of how many stars there even are within, say, a 100 light year radius of our sun (I guess that's a more realistic thing to find out than the number of planets). A quick search…

On the plus side there are more moons than planets and many of them may be habitable. We've barely started looking at extra solar Jupiter like planets because of the much longer orbital periods.

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

#192

Post by caf »

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 am amused by the idea of a "small giant".

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

#193

Post by saagarjha »

ant6n wrote: post #185
mabbo wrote: post #178

Earlier quoted context omitted.

Years ago as a second year computer science student, I mentioned to a grad student I knew how disappointed I was about a certain algorithm. "It's O(n), but the constant is enormous! There's no point unless you have billions of elements"! She said to me "Yeah sure, but who cares? What it really tells us it's that it's possible to do this in linear time at all . That might not have been true, and now we know we might f…

We already knew it's possible to have a planet in the habitable zone with water (and life, incidentally). Whether it's common is still unclear, given that so far there's a big bias towards detecting large exoplanets that are close to the host star.

The point is finding planets aside from our own.

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

#194

Post by saagarjha »

stjohnswarts wrote: post #174
methodover wrote: post #169

Earlier quoted context omitted.

So, actually, like, it's actually really intuitive I feel like: From the perspective of an object accelerating, newtonian physics works totally intuitively. If you had a rocket that could accelerate at 1g indefinitely, you just go faster and faster and faster and you get to any destination you want (even far away!) pretty quickly. And it would be a rather comfortable trip! You'd have Earth-like gravity the whole way.…

There is nothing intuitive about relativity unless you understand the physics and math behind it. Intuition can only be as good as your knowledge and experience.

Hey, look at this guy over here who's never been accelerated to a relativistic velocity here! But in all seriousness, you don't need to know all the math behind how relativity works to have a general idea of its effects.

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

#195

Post by gus_massa »

rapind wrote: post #157
swarnie_ wrote: post #145

Earlier quoted context omitted.

That does raise a huge number of ethical issues. Do we have the right to interfere on a planet which may already have life?

Survival of the fittest. We launch our virus first... assuming they didn't already launch theirs, in which case it's mutual destruction.

Ignoring the moral problems ...

Nitpicking: Virus are a bad choice. Most are highly specific and reuse a lot of the machinery of the cell they attack. It's much better to send a mix of bacteria and archaea (ask an specialist to get a good combination of strands that like to live in different conditions (hot/cold, oxygen/no-oxygen, ...)). Put them inside a shell to protect them from radiation and a good shell for landing/crashing (ask another specialist for this part too), perhaps like a multiheaded interplanetary missile with many a copy of your minizoo.

Probably anything you send has enough bacterias to have a chance, unless it's super clean an sterilized. They try not to send bacterias to Mars, but I think bacterias will win. They only need a single error to get a free trip.

I remember a joke that someone said that Eukaryotes is the method that Prokaryotes use to travel from planet to planet.

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

#196

Post by saagarjha »

nerflad wrote: post #167
gradschool wrote: post #150

Earlier quoted context omitted.

Not a physicist, but I think it might not be that simple. From our point of view, a ship with constant 1g acceleration increases its speed by 9.8 m/s every second, but people on a ship moving at a significant fraction of c take more than one of our seconds to experience one of their seconds. During the time they experience one of their seconds, the speed increases more than 9.8 m/s, so they must experience greater th…

Isn't a second now officially defined as a single period of atomic decay of a certain atom (I think Cessium?)? So this theoretical near-lightspeed craft could adjust it's accelerators based on an onboard atomic clock that would not be based on seconds as we tend to perceive them, but on SI seconds. I assume these would be getting longer as velocity approached 1c. Unless radioactive decay is also affected by relativit…

One of the consequences of the theory of relativity is that there is no "absolute time". The atomic clock will perceive time just as you will–that is, slower than an inertial reference frame.

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

#197

Post by saagarjha »

gradschool wrote: post #150
caseymarquis wrote: post #81

Earlier quoted context omitted.

Just under a year at 1g (according to google. I'm on mobile and would have to derive from F = ma on paper to solve). Energy is variable. I'd assume energy isn't relevant, as it's currently impossible, so we're taking that for granted. Not really that long.

Not a physicist, but I think it might not be that simple. From our point of view, a ship with constant 1g acceleration increases its speed by 9.8 m/s every second, but people on a ship moving at a significant fraction of c take more than one of our seconds to experience one of their seconds. During the time they experience one of their seconds, the speed increases more than 9.8 m/s, so they must experience greater th…

Length contraction is something outside observers would see; the people on the ship would see themselves as normal (and hence not be "squashed".)

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

#198

Post by lachlan-sneff »

There are lots of people in the comments here talking about how long it would take to send a probe, or how many generations a generation ship would have, but it seems clear to me that that's not how humans are going to go to other solar systems.

Once we solve mind uploading (assuming that it's possible), we can send a blob of grey goo on a solar sail at a very high acceleration to another solar system. It can shed half of the sail and bounce the laser back to decelerate.

The grey goo would go and convert part of asteroid or something to computronium, and then we'd upload a bunch of humans over to the other solar system.

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

#199

Post by solipsism »

saagarjha wrote: post #193
ant6n wrote: post #185

Earlier quoted context omitted.

We already knew it's possible to have a planet in the habitable zone with water (and life, incidentally). Whether it's common is still unclear, given that so far there's a big bias towards detecting large exoplanets that are close to the host star.

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 find other Earth-like planets. We suspect rocky planets aren't that rare, we know planets at comparable distances from the star are not that rare, and we know H20 is plentiful in space. The problem is one of detection. The smaller the planet, the harder it is to detect water, so most of what we've found so far is gassy giants.

A good analogy is the fact that I don't know anyone who shares my birthday. That doesn't mean I would be amazed if I were to find someone did share my birthday, cuz I have no reason to suspect my birthday is particularly rare. I just don't know that many people.

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

#200

Post by saagarjha »

usrusr wrote: post #68
kadoban wrote: post #42

Earlier quoted context omitted.

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?

Better than the miniscule gain in potential energy (height x mass x gravity) because you also save a lot of aerodynamic drag not punching through the lower atmosphere at high speed and some "hovering losses" (rise time x mass x gravity, I'm sure there is a better term for that). But still not worthwhile due to the difficulty of floating a full size rocket. If you had a very very high mountain or tower, moving that fu…

I doubt such a planet would be hydrostatically stable, though…
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