Water found on a potentially life-friendly alien planet

https://www.nationalgeographic.com/science/2019/09/first-water-found-in-habitable-exoplanets-atmosphere-hubble-kepler-k2-18b/

by Leace • 7 years ago

606 369 7 years ago

nationalgeographic.com

transreal• 7 years ago

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...

JumpCrisscross• 7 years ago

With a planet this large, visiting it would be a one way trip

Assuming chemical propulsion and no refuelling at the destination.

Supermancho• 7 years ago

If it's chemical propulsion, you're dead when you get there. If there's no refuelling (and you need refuelling) with some other travel mechanism, you can't get back.

So we have an "or" assumption, not "and", with an additional and assumption about refuelling. That's how I read it.

dogma11383• 7 years ago

I think what the GP refers to is that there isn’t enough energy in chemical rockets to overcome its gravity, even flight might not be even possible albeit that’s also dependent on the density of the atmosphere to some extent.

allannienhuis• 7 years ago

The amount of fuel at the destination doesn't change the rocket equation for being able to get into orbit from the planet. From the provided link:

"If the radius of our planet were larger, there could be a point at which an Earth escaping rocket could not be built. <snip> That radius would be about 9680 kilometers (Earth is 6670 km). If our planet was 50% larger in diameter, we would not be able to venture into space, at least using rockets for transport."

archgoon3• 7 years ago

It's 111 light years away. For all intents and purposes, that's a one way trip right there; irregardless of the rocket equation. Even at relativistic speeds, you can't come home anymore.

ajconway• 7 years ago

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

guelo• 7 years ago

The fastest spacecraft humans have produced is the Parker Solar Probe which when it zips around the sun will reach 430,000 mph. At that speed it would take 173,000 years to reach this planet.

soulofmischief2• 7 years ago

We're talking about just escaping the surface gravity, not returning to Earth.

markdown• 7 years ago

regardless

partiallypro2• 7 years ago

But that's assuming you're traveling at the speed of light, right? In reality it would take much much longer than 111 years.

perseusprime11• 7 years ago

At 111 light-years, we need to create a vehicle that can sustain several generations.

kadoban4• 7 years ago

So that's purely for a chemical rocket, right?

Is there any combination of tricks that can realistically push the envelope there? For example can we use a space elevator to start higher/faster (or, I don't know, balloons? a catapult or railgun or something?), laser power delivery from the ground, so we don't have to carry all the fuel, and an orbiting way-station for refueling, etc.?

Miner49er4• 7 years ago

Solar sails might be able to beat it.

https://en.wikipedia.org/wiki/Solar_sail

ta1234567890• 7 years ago

Exactly

From the reference article:

Travelling from the surface of Earth to Earth orbit is one of the most energy intensive steps of going anywhere else. This first step, about 400 kilometers away from Earth, requires half of the total energy needed to go to the surface of Mars.

Which means that if we use something like a balloon/blimp in the first stage, it would be a lot more energy efficient.

Anyone knows why it's not done that way already?

Also, whatever happened with the plane+rocket Virgin Galactic project?

buboard• 7 years ago

Launching from a mountain is a possibility ( I think China does it)

Realistically, but not plausibly unless its an emergency, Thermonuclear bombs:

https://www.youtube.com/watch?v=EzZGPCyrpSU

lopmotr• 7 years ago

Nuclear bomb rockets would probably do https://en.wikipedia.org/wiki/Nuclear_pulse_propulsion

mabbo2• 7 years ago

For example can we use a space elevator to start higher/faster (or, I don't know, balloons? a catapult or railgun or something?), laser power delivery from the ground, so we don't have to carry all the fuel, and an orbiting way-station for refueling, etc.?

These methods will all help with the first 1% of your problem, getting off of the earth.

But you need so many orders of magnitude more energy to reach the kinds of velocity needed to get to another star in less than a million years. It's just an unfathomable amount of energy per kg. Put simply: if you can get to another star, getting off the planet is nothing.

SJSque• 7 years ago

There's also the Wait Calculation to consider:

https://en.wikipedia.org/wiki/Interstellar_travel#Wait_calcu...

PorterDuff3• 7 years ago

Hey, I like that idea.

Maybe it implies that every interstellar mission is just an in-flight rescue mission.

0xffff215• 7 years ago

That's interesting in theory, but as far as I know our interstellar propulsion technology hasn't advanced significantly at all in the last 50+ years. You can't do theory in a vacuum forever. I'd argue that unless we launch an interstellar something, we're never going to see any technological advances in the field.

ryacko2• 7 years ago

The wait calculation implies that the returns from economic growth will eventually be converted into rocket fuel. A fun equation, but economics doesn’t translate well on time scales where depreciation of capital is 100% and becomes another expense.

hinkley4• 7 years ago

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? Would you give up dreams of the stars? Would you look for intelligent life you couldn't ever possibly meet?

jerf3• 7 years ago

"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 didn't find the risk/reward to be too highly slanted to the "risk". Other species and other ecosystems may come to different conclusions, e.g., an ecosystem already more exposed to radiation and evolved to deal with much higher levels of it may judge it much less "risk" for some radionuclides to be scattered across the landscape in case of failure.

What can be more of a problem is being in a place where you have no obvious access to technology at all. However smart our cetacean buddies may be, it is not clear even at this point in the 21st century what path to technology they could possibly have from their starting point. "The literature", a.k.a. "science fiction" has hypothesized breeding programs to develop various tools, but it's still not entirely clear how they'd get from "breeding useful jellyfish" to, well, anything like technology as we know it. It's possible we're just not solving this problem because we don't have to, maybe there's some easy path with the right development path, but it's still not clear what that would be.

[1]: One of my markers for "the space age is truly here" is when we lift a nuclear rocket into space, sans fuel, and fuel it with space-sourced radionuclides. Earth-bound citizens will still complain, because "NUCLEAR BAD!", but their complaints will be ignorable at that point.

scarejunba• 7 years ago

So long as you're carrying all the fuel on you, right? If I can launch 1000 auxiliaries that resupply you and a 1,000,000 auxiliaries to resupply the 1000 auxiliaries I can go up farther.

TheOtherHobbes• 7 years ago

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.

dsfyu404ed• 7 years ago

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.

gcthomas2• 7 years ago

Given the published figures for size and mass, it will be closer to 1.5 - 1.6 g. Still tricksy to walk for unmodified people, but not impossible, especially given how long it will take to reach it. Plenty of time to work out how to change people.

yellowapple2• 7 years ago

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.

hinkley4• 7 years ago

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.

scrumbledober2• 7 years ago

currently we have no known materials that would actually be strong enough to support their own weight at the length of a space elevator on earth. double the gravity and the length will also at least double (possibly quadruple? not sure on the math here) so it may also be impossible to build a space elevator on one of these planets, at least without the use of active suspension (possible? theoretically.)

cthalupa7• 7 years ago

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.

perl4ever10• 7 years ago

A nuclear rocket still needs propellant, doesn't it?

pierre_d5282• 7 years ago

Or we could shift to an other side of the universe by "inverting" the mass of the ship where the speed of light is much higher[1].

Cosmology is so cool... too bad we do not have time for that: we cannot even cure the common cold!

[1] https://januscosmologicalmodel.com/pdf/2014-ModPhysLettA.pdf Cosmological bimetric model with interacting positive andnegative masses and two different speeds of light,in agreement with the observed acceleration of the Universe

atonalfreerider• 7 years ago

Special Relativity can be summed up in the sentence: “We live in a spacetime which is an M4 manifold with a hyperbolic Lorentz metric of signature (+−−−)”. General Relativity can be stated accordingly: “The Universe is an M4 manifold with a Riemannian metric of signature (+−−−)” which is a solution of the Einstein equation:Rμν−12Rgμν+Λgμν=χTμν.

It sounds like you get anti-gravity for free along the way to getting superluminal travel.

spullara• 7 years ago

I couldn't find anything with its approximate radius (it mentions about-earth sized and 8x the mass but that could mean anything) to make an evaluation of the likely gravitational force at the surface in order to make the evaluation of whether you could get off the planet cheaply.

nothis2• 7 years ago

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 provided some estimates and they're kinda... disappointingly low, at around 20000 stars. That's a number where some "1% of 1% of 1%" kinda filter quickly ends up in a scenario where a planet fitting all our criteria might simply never be in reach. For something more "realistic" (I know, heh!) like 20 light years, there are only 150 solar systems. I've seen different numbers and have no idea how they're calculated but for the usual astronomic scales which quickly go into "billions" territory, it seems we're kinda stuck with a comparably small list of candidates.

tejtm• 7 years ago

It might cheer you up to to think we have yet to prove there is a star with no planets.

flukus• 7 years ago

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.

newsbinator• 7 years ago

That's a number where some "1% of 1% of 1%" kinda filter quickly ends up in a scenario where a planet fitting all our criteria might simply never be in reach.

It might cheer you up to think that's the only reason the human race happens to be the one in our neighborhood that made it into space, without being stepped on by an Old One.

perl4ever10• 7 years ago

I think people are beginning to realize, that just as there are more asteroids than planets, and more space junk than large asteroids, there are a lot more free floating planets than stars.

It could well be the universe is filled with life, but the dominant mode is underground chemo/radiotrophic microbes on planets without stars.

Miner49er4• 7 years ago

It's depressing to think that if there is intelligent life on that planet, we won't be able to communicate with them in any way in our lifetime, yet it's so close. Unless they started sending communications our way over a century ago.

tyri_kai_psomi2• 7 years ago

If it is depressing to think about it, then why think about it? Does it have any real implications for significant outcomes about your life or is it in a way some type of FOMO?

Miner49er4• 7 years ago

Well, I suppose I'm using a bit of hyperbole. Maybe I should say sad. And don't worry, I won't think about it very long.

chr12• 7 years ago

It is more depressing that our lifetime is not even 100 years long. Hopefully Aubrey de Gray's predictions about longevity escape velocity would turn out to be true and we or our children would be able to wait for communications spanning multiple centuries.

dopamean• 7 years ago

What makes a planet an "alien" planet?

Rerarom• 7 years ago

Not being in our Solar System, I guess.

makerofspoons• 7 years ago

It is part of a different solar system: https://en.wikipedia.org/wiki/Exoplanet

onemoresoop• 7 years ago

I never encountered the term alien planet but exoplanets are planets outside our solar system. In a way all planets are alien to one another. Alien to us is anything extraterrestrial in this context.

infradig• 7 years ago

The media.

lucb1e• 7 years ago

Yeah that was my first thought when reading the headline: "yet another habitable planet found" is getting old, now we need to mention it's "alien" (generally associated with green men, or more broadly, life not originating from earth; not with a planet) to get attention.

cryptoz• 7 years ago

Lots of discussion on the possibility of going or communicating, but for me the excitement is the narrowing of uncertainties in the Drake equation and the focusing of discovery of alien life, intelligent or otherwise.

Discoveries like this improve our understanding of likelihood of extraterrestrial life, which has direct Earthly implications. It also enables better estimates and searches for planets that are closer, say ~4 to 20 lightyears away, for those super interested in the traveling & communicating possibilities.

tontonius• 7 years ago

After reading Liu Cixin's Three body Problem, let's just say I'm less super interested in communicating :)

novaRom• 7 years ago

I am thinking to get a not very expensive refraktor (120 mm) with Azimutal mounting, for deep space and terrestrial observations. Just interested in Astronomy, but have no idea what level of details can be seen with that kind. I am fascinated by Orion Nebula and Andromeda which I can see with simple 8x42 ED binoculars. Now thinking about telescope. Dobsonians look pretty heavy, I want something portable and inexpensive. Do you have any suggestion? Are refractors good for that?

eggpy2• 7 years ago

potentially life-friendly

Spoiler: it's not

0xffff215• 7 years ago

Life friendly != human friendly.

eggpy2• 7 years ago

I understand that. This planet is far more likely to not be habitable, period. We might as well consider Neptune to be "potentially life-friendly".

calgaryeng2• 7 years ago

Isn't it odd to think that one day, there will be a top post on Hacker News: "Alien Life Discovered on Nearby Planet (430 points)".

DC-3• 7 years ago

One would like to think that it would get more points than that :-)

yiyus• 7 years ago

But if it gets more than 430, it will have 430 at some point.

alex_duf• 7 years ago

It depends if it's the same day apple announces their new iPhone

escapecharacter• 7 years ago

Right underneath “10 Reasons why Git 3.7 is going in the wrong direction (583 points)”

nmfert• 7 years ago

For sure would get more points than 430 haha

chenning3• 7 years ago

A very quick search suggests that earth will become uninhabitable somewhere between 500 million and 2 billion years from now. If we shot a probe to this life-friendly alien planet with some sort of primordial soup, even traveling at the speed of light it would take 4 billion earth years to get there. Do I have that right? Basically we'll never even come close to being around when it finally arrives, if it ever arrives. Has anyone ever thought about doing this? We've shot gold records out into space for aliens with turn-tables. Why haven't we tried this?

0xffff215• 7 years ago

A very quick search suggests that earth will become inhabitable somewhere between 500 million and 2 billion years from now.

I'm 99% sure that Earth is inhabitable right now... perhaps you meant "uninhabitable"?

chenning3• 7 years ago

Is it though??? (edited, thanks)

mdgrech23• 7 years ago

Your assumptions may be wrong especially considering how far in the future we're talking.

kadoban4• 7 years ago

It would not take 4 billion years at the speed of light, it would take 111 years. That's what light-years are, the distance travelled by light in a year.

0xffff215• 7 years ago

Strictly speaking, if you actually traveled at the speed of light, the trip would be instantaneous from the reference frame of the craft making the trip. It would still take 111 years from our frame of reference on Earth.

chenning3• 7 years ago

Ah, right. Basically I vote for firing a primordial soup probe to this sucker.

cody3222• 7 years ago

That's what wormholes are for...

not_a_cop752• 7 years ago

It seems like it would be much easier to terraform the real estate around us than try to opt for something 100 light years away.

Mars has a leaky atmosphere - sure it's a real fixer upper. But we have a better chance of fixing it, or even correcting the orbit of our planet so that in 500 million years it's still livable.

grumpy82• 7 years ago

Or sending a HUGE human civilization spaceship somewhere.. maybe it will outlast the earth?

jacobsenscott• 7 years ago

Even easier is to stop digging stuff up and burning it. But we can't even do that.

AnIdiotOnTheNet2• 7 years ago

Christ, why even go to Mars? Even in the worst cases the damage we do to Earth will still leave it significantly more hospitable than Mars.

nothis2• 7 years ago

traveling at the speed of light it would take 4 billion earth years to get there

Genuinely wondering how you got that number. I'm reading 111 light years in the article, wouldn't that simply be 111 years of travel time, at the speed of light? Am I missing something?

chr12• 7 years ago

The threat in 500 mln years is that all CO2 will be used in shells of see creatures. But considering how good we are at freeing more carbon this issue should be easy to fix.

ghostbrainalpha• 7 years ago

Serious question - Do we have the capability to send human life there now?

Obviously its going to be a one way trip. And it would require a generational ship.

So could we build a ship that held 12 people initially, 6 couples, all who were allowed to have 2 children, so 24 people max, and could we load it with enough supplies to last over 100 years?

Even if the group that eventually arrived had no way to sustain life, and they just went there for a quick swim before dying... is it possible?

0xffff215• 7 years ago

We don't have the capability to send anything there now. Sending even a tiny probe that is capable of communicating back to Earth from our closest stellar neighbor is beyond our current technology. People are actively working on it, but it's unlikely that we will have the technology to even send an unmanned probe to this star within our lifetimes. We might send a probe to Alpha Centauri, but it's even questionable whether it will be fast enough to arrive within our lifetimes.

trhway• 7 years ago

Project Orion - riding nuke explosions - using existing tech/materials and those 100K nukes that both sides had at the peak of the Cold War would bring a 30K ton ship to the 5-10% of c. Curiously, getting all that 100K+ ton of hardware to LEO where one can finally start exploding the nukes seems to be more complicated task right now.

manicdee2• 7 years ago

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

mabbo2• 7 years ago

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 find a faster linear algorithm."

(All of this is paraphrased because it's been over a decade).

The point is: we have found another planet with water. We now know this is possible! We know that it's probably not super uncommon (or else we wouldn't have found one so soon). That's what's amazing about this.

So what if it's not perfect, it's a great discovery!

ant6n• 7 years ago

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.

caf• 7 years ago

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

mr_toad• 7 years ago

Neptune is ‘only’ 57 times the volume of Earth, whereas Jupiter is 1321 times the volume of Earth. The size range of ice/gas giants is bigger than the gap between Earth and the smallest ice giants.

brownbat• 7 years ago

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 sniff test on a planet and then just breathe without assistance.

https://en.wikipedia.org/wiki/Bronchiolitis_obliterans

You have an identical twin to Earth with slightly different dust composition and it could shred our lungs. We are highly, highly tuned to our home.

Which doesn't mean we can't go anywhere. But it won't just be advances in travel speed that will get us off world. It may also require drastic modifications to the human organism.

tripzilch4• 7 years ago

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.

petre• 7 years ago

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.

BurningFrog• 7 years ago

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.

aussieguy1234• 7 years ago

I think the keyword here is "potentially habitable"

luxuryballs2• 7 years ago

Also it just seems to be water, they’re obviously not 100% sure it’s not something else that’s reading as water.

gmueckl• 7 years ago

How easy is it to have different mixtures of substances that lead to similar enough absorption apectra that they are indistinguishable with the available resolution and sensitivity?

Tepix2• 7 years ago

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 earth is not very friendly for humans, ignoring all the other possible issues (pressure, chemical composition, radiation, flares etc)

manicdee2• 7 years ago

The “habitable zone” is the theoretical range from the Star that allows an Earth-like planet to have mean temperatures suitable for Earth-like life.

It’s almost entirely arbitrary, but roughly based on luminosity of the star.

perl4ever10• 7 years ago

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.

carrozo2• 7 years ago

So tired of hearing about “habitable” planets that would take millennia to get to. Call me when the space elevator has been commissioned.

0xffff215• 7 years ago

If it makes you feel any better, virtually all of them are uninhabitable to humans. The excitement comes from the idea that they could be locations of alien life that we would easily recognize. In other words, we need better communications tools, not better space travel.

anyfoo2• 7 years ago

Or even just better observation tools, that would be amazing already. Sadly, at the scales we are talking here, even "just" getting those tools seems very improbable, at least...

carrozo2• 7 years ago

Imagine if we could somehow have optical closeups of these planets and all we found were trillions of dinosaurs incapable of all but crow-like tool-making. We’d be so buzzed and bummed at the same time.

lachlan-sneff3• 7 years ago

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.

ryacko2• 7 years ago

If we can simulate wetware perfectly, we would also be able to solve any health condition.

This is all presumptive of the preferences of individual humans. It may be that the giant extrasolar Earth-type planets could be dismantled and rebuilt into smaller Earths located at various Lagrange points.

lachlan-sneff3• 7 years ago

For sure, maybe future humans won't want to do that. The important takeaway is that they'll have the opportunity to do so if they wish.

They could even clone them back on the other end and install the preexisting mind, basically teleportation.

russellbeattie• 7 years ago

Only 1,050,000,000,000,000 kilometers away...

tunesmith7• 7 years ago

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 will take for us to arrive there.

One common recommendation for annual energy growth rate is 1.4%, and then taking the square root to get velocity growth rate since velocity has a square root relationship with energy.

By plugging that in, we can minimize our time by growing for 1020 years, and then traveling for 144 years, for a total time-from-now at 1164 years.

Another paper[2] estimated an annual velocity growth rate of 4.72%, quite a bit faster. Plugging that in, it says we should wait 195 years for a travel time of about 21 years, or 216 years overall. This is of course incorrect since it assumes being able to travel FTL. So if you instead look at how long it would take to get to light speed travel at that rate, you're looking about about 159 years, or arriving at the planet at a time-from-now of about 270 years.

Of course, if you're seeking to minimize time-from-now from the perspective of a traveler, maybe you'd take off sooner. Kind of a tradeoff - less time to wait for the traveler, more time to wait for the home planet. I haven't figured out that part of the math yet.

[1] https://ipfs.io/ipfs/QmXoypizjW3WknFiJnKLwHCnL72vedxjQkDDP1m... [2] https://arxiv.org/abs/1705.01481

Simon_says2• 7 years ago

taking the square root to get velocity growth rate

This is your mistake. It's an approximation that works well only at low speeds.

dylan604• 7 years ago

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

healsjnr12• 7 years ago

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.

tunesmith7• 7 years ago

No, it assumes you start and end at whatever that maximum velocity is that we've been able to achieve.

That'd be fun to add, though. I'm not really sure what human-safe acceleration is - people here assume it's in the 1g-3g range. (That seems like a lot to me though, particularly for a long period of time - I think anything more than a fraction of g would be wildly uncomfortable.)

narrator• 7 years ago

Progress in physics was much faster in the early 20th century when it wasn't so fascinated with deep space. Yes, you needed to observe eclipses to verify relativity, but that was a tool, not the end in itself.

Cosmology involves distances that are so great that it seems like it's pouring a whole bunch of smart people's efforts down the drain in an ultimately futile waste of brain power that will never amount to anything much at all. Besides, when we get faster than light travel we can just pick up exoplanet research where we left off and it will actually be practical and probably far more efficient with the computers and such we will have developed by then.

vermilingua4• 7 years ago

when we get faster than light travel

FTL requires numerous things to be true about our universe, that all signs say are not.

_imba_• 7 years ago

Progress in physics was much faster in the early 20th century when it wasn't so fascinated with deep space.

I don't think measuring progress is tivial enough to make that assumption. It's also unfair to blame a fascination with deep space for any slower progress, things are more complicated than that.

Getting humans onto anther planet asap is one of the most important things one can pursuit for humanity. The earth is a giant single point of failure

privong• 7 years ago

Cosmology involves distances that are so great that it seems like it's pouring a whole bunch of smart people's efforts down the drain in an ultimately futile waste of brain power that will never amount to anything much at all.

I think it depends on what one wants to get out of the research. If the goal is a commercially realizable product on a shortish time horizon (say < 50 years), then cosmology may not be the best approach. But the justification for cosmology and much of astrophysics is typically that it is a probe of fundamental science and the acquisition of knowledge for its own sake. In which case whether we can ever travel to other planets or galaxies is moot, since it's the physical understanding and knowledge that's the goal.

Many before me have used the example of relativity, which when proposed, seemed to have little practical value. But GPS wouldn't work without relativistic corrections. 100-120 years ago one could've made a similar statement about fundamental physics and work on relativity. But if we'd abandoned it because of a lack of immediate relevance then we wouldn't have workable GPS today. The benefits of fundamental research (in many areas, not just astrophysics) are often quite difficult to forecast.

amelius2• 7 years ago

it seems like it's pouring a whole bunch of smart people's efforts down the drain in an ultimately futile waste of brain power that will never amount to anything much at all.

Well, at least they're not making people click ads ...

tripzilch4• 7 years ago

when we get faster than light travel we can just pick up exoplanet research where we left off

if we get FTL, we'll be able to pick up that research before we left off ...

DoctorOetker2• 7 years ago

we might some day discover that we are roughly coaxially located between 2 civilizations exchanging knowledge, and get up to speed with their knowledge.

or observe civilizations broadcasting knowledge in a loop: motivation? perhaps the faster they can get others up to speed, the faster others might contribute knowledge back which may some day save their civilization.

temporalparts2• 7 years ago

Does this take into consideration that your mass increases as you travel closer to the speed of light?

tunesmith7• 7 years ago

No, I'm not sure what that would suggest - how would that need to be accounted for? Maybe some fraction of light speed would need to be the upper bound, low enough that mass increase wouldn't have a material impact? I'm having trouble understanding what impact the mass increase would have in the first place.

skrebbel• 7 years ago

As a startup founder, I learned the hard way to not assume progress will ever be exponential.

blencdr• 7 years ago

As a guy who lives in a finite world where energy comes mainly from fossil fue in a way or another, I do not assume that any constant progress in energy supply is something achievable.

tunesmith7• 7 years ago

Over any timeframe, the rate of progress between the beginning and ending of the timeframe can be phrased as exponential for some exponent. It's just a matter of accurately estimating what that exponent is.

I take your point though - hypergrowth cannot be sustained - and estimating that exponent is fairly valueless if volatility is too high. This is all just math fun that won't be valuable if we bump along for hundreds of years and then all of sudden make a massive discovery.

radeklew2• 7 years ago

As others have said, E=mv^2/2 only holds at very small fractions of the speed of light. I believe the equation you need is E=mc^2/sqrt(1-v^2/c^2)-mv^2.

https://en.wikipedia.org/wiki/Kinetic_energy#Relativistic_ki...

tunesmith7• 7 years ago

Can you explain this further? It seems this is relevant more for something other than the Wait Calculation. The original Wait Calculation doesn't factor in mass at all. I'm having trouble understanding what this impacts. Is this more about relativistic time passage, like from the ship traveler versus the observer?

Most scenarios I've explored - low velocity growth rate, nearby planets/stars - the Wait Calculation tells you to stop researching and start launching long before your tech gets to significant fractions of light speed.

gregmac• 7 years ago

Does that include slowing down and stopping, or would you be at max speed by the time you got there?

I always thought that was a very well thought out aspect of The Expanse: spend half the trip accelerating, then flip the ship around and spend the other half slowing down (aka accelerating in the opposite direction).

mAritz• 7 years ago

Disclaimer: Just an arm-chair Space Engineers player here.

I always thought that was a very well thought out aspect of The Expanse: spend half the trip accelerating, then flip the ship around and spend the other half slowing down (aka accelerating in the opposite direction).

With current technology you would not do this, since that means using extra fuel that weighs a lot and thus increases the force required for the same amount of acceleration as you'd get with less fuel and less burn.

Of course that changes drastically if the fuel required for more acceleration (and its container) is very light-weight. I would assume fusion or fission based thrusters would be better in this regard, however I think currently those produce very little acceleration in a vacuum compared to combustion thrusters.

babuskov• 7 years ago

One common recommendation for annual energy growth rate is 1.4%

Where does this come from? Does it even hold water when compared to past data? Looking at some Wikipedia data for the past 20-30 years, it seems that the increase in speeds is much higher:

https://en.wikipedia.org/wiki/List_of_vehicle_speed_records#...

hoseja• 7 years ago

That's a lot of hand-waving. Reminds me of Drake equation. Why not just admit we have no clue yet? Also the Parker Solar Probe speed is due to orbital mechanics of basically free-falling towards the sun and you'd have to do things very differently if you wanted to have that speed going out of the solar system.

mk89• 7 years ago

So our only hope to see a planet different from ours is that some advanced alien population comes to "see" us, with all the implications this has...

nannal• 7 years ago

History does not favour the civilization which is visited.

alexgmcm• 7 years ago

Why is annual energy growth rate or industrial growth rate assumed to correlate to the speed of space travel?

Just because we build more power plants or sell more tractors doesn't imply a corresponding improvement in spacecraft technology.

The Wait Calculation seems to make even less sense than the Drake Equation - which is at least correct in theory even if the actual variables have so much uncertainty it is useless.

neuronic• 7 years ago

This completely dismisses any tangential factors, of course. Going earlier might be an advantage, as new ways to kill each other (or kill Terran ecosystems) emerge.

Going later to optimize for time is one aspect of deciding how to spread throughout the galaxy. Another question might ask, which is the most risk reducing strategy? And the answer might be completely different.

wazoox• 7 years ago

Yeah. Well. That's a fun math game and not much more. Other view on "energy growth rate": https://dothemath.ucsd.edu/2011/07/galactic-scale-energy/

Energy growth is due to end sooner or later.

First, in the real world, any long term exponential growth is actually the upward branch of an S (that plateau at some point) or of a bell curve (that falls down after a peak).

Second, with such an energy growth rate we'll boil the ocean from heat dissipation long before we reach the stars.

imtringued• 7 years ago

There is also the problem that as you get away from the sun you receive less energy. Making your own portable mini sun with a fusion reactor is essential for interstellar travel.

eru2• 7 years ago

Mostly I agree. But: we can keep our energy curve growing for a bit longer, if we branch out into the local space around us. No worries about boiling the ocean, when the energy stays in orbit.

numerobis• 7 years ago

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)?

munherty• 7 years ago

Someone please correct me, because with a planet that is at 111 light years away aren't we technically looking back in time?

Any type of observation was only a period Of time and any type of life used to be there, but may not be there presently?

Simon_says2• 7 years ago

Everything you look at is looking back in time.

dyslexit• 7 years ago

110 years in the past is insignificant relative to a planet's geological period's age.

ryeguy_24• 7 years ago

Correction, water “was” found. This water was there 111 years ago.

ballsyballsman• 7 years ago

Calling it "alien planet" has a negative warmongering tone.

leonroy• 7 years ago

Reading about that led me to this article about a water world that was discovered:

‘A giant waterworld that is wet to its core has been spotted in orbit around a dim but not too distant star’

With oceans 9000 miles deep (15000 km). For context the Earth’s diameter is 7900 miles (12700 km).

The imagination really does boggle at the thought. I think science fiction is going to have a hard time keeping up with the incredible science fact we are observing in our lifetimes.

https://www.theguardian.com/science/2009/dec/16/waterworld-p...

known• 7 years ago

If water is found can we assume fish like life in that planet?

flywithdolp• 7 years ago

That's the kind of news that makes me smile and worry at the same time

All my life I wait for the moment we will find life

I just afraid if it will really happen from everyone reactins

DoctorOetker2• 7 years ago

that title should read "Water found on a potentially life-friendly exoplanet"

jug• 7 years ago

So they finally got there. Detecting atmospheric water vapor on a planet 110 light years away. amazing.

sbarre• 7 years ago

This reminds me of a sci-fi book I read when I was a kid called Rocheworld by Robert Forward.

They were going to the Barnard Star, but it had binary planets where one was all water.

Good book (if I recall)..

timpannn• 7 years ago

Thought this was found multiple years ago?

carapace• 7 years ago

I think we would have to manage to extend human lives to ~10,000 years or more to be spacefaring.

najarvg• 7 years ago

Sorry if it's been mentioned in the threads before - Here is Phil Plait's (@badastronomer on twitter) practical explanation of this finding - https://www.syfy.com/syfywire/water-vapor-detected-in-the-at... TLDR - "NO, THIS DOES NOT MEAN THE PLANET IS EITHER EARTH-LIKE OR HABITABLE."

Water found on a potentially life-friendly alien planet

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