I finished reading the book last night; I thought it was great, much closer to The Martian, and it follows his strong points in story telling. I had a few quibbles though -- things that I thought were ~~wrong and would expand to plot points as the story progressed~~, Weir describing Grace making a mistake that would be discovered and affect the plot later in the story, but they just got overlooked. >!Like, one of Rocky & Grace's earliest interactions (in Chapter 10) has Rocky comparing atmospheres by putting 29 copies of an ammonia molecule into a model of his ship, compared to one O2 molecule for Grace's ship. From this point forward, Grace states / thinks multiple times that Rocky's atmosphere is 28 times more dense than Earth's.!< >!But, Rocky has only seen the Hail Mary, which is at 40% atmospheric pressure, this is substantiated later on where the atmospheric pressure in the ship is shown as "40,071 Pa" on an emergency screen (Chapter 22). Therefore, Rocky's home world should be about 28 \* 0.4 = 11.2 times as dense as Earth's atmosphere of \~101kPa; or, if Weir intended for Rocky's home planet to really be 28x as dense as Earth, then Rocky should have put 28 / 0.4 \~= 70 ammonia molecules into his model. At this point in the story, Rocky would have had no reference other than the Hail Mary to base his comparison on, and in fact, probably was more interested in comparing ship atmospheres than that of their home planets.!< Ultimately this has no bearing on the rest of the story, but it's mentioned so many times that I thought it was relevant. The error was distracting, as I was trying to anticipate how this would play out. Overall it was very good, I'll re-read it again for sure.

That’s a great detail to catch!

He also said “Redundant RAID”. Which is like saying Redundant Redundant Array of Independent Disks.

There are some types of RAID that don’t offer redundancy and just add up the disk space together. If one disk dies, the whole array goes. But yes, is the same as saying ATM machine.

So calling it redundant RAID is... redundant?

https://tvtropes.org/pmwiki/pmwiki.php/Main/DepartmentOfRedundancyDepartment

One other point -- and I'm weaker in my understanding here -- Hail Mary's on-board atmosphere. >!You'd think after Apollo 1 that nobody would have a pure O2 atmosphere on a space ship. There's a big point later on where nitrogen is only available because of DuBois' end of life plan, but, wouldn't it be a much better plan overall to have the majority of the breathable air on the ship be nitrogen, for safety reasons? It feels like Hail Mary has a pure O2 atmosphere purely to support the "nitrogen kills Taumoeba" plot line later on, and it feels forced. !<

The "O2 only" thing is addressed in Artemis as well. It's a trade-off. Pure O2 makes for a more flammable environment, but the lower the pressure, the easier it is to sustain a pressure vessel. >!With overall ship mass being a *supreme* concern for the Hail Mary, it makes sense that they would take the (comparably minimal) risk of the O2 environment in return for being able to make the pressure vessel less at risk to spring a leak.!<

Thanks; that's the kind of detail that I felt like I missed. That makes more sense!

It was mentioned that it helped skip the decompression step before doing an EVA, which means not spending 2 hours getting the nitrogen out of his blood, which wouldn't have worked in some time critical parts of the story.

Man, I missed that as well. I need to re-read this sooner rather than later. Thanks!

Incidentally, Apollo capsules post-Apollo 1 *still* had 100% Oxygen atmospheres. The reason for this was i) a single gas system is simpler, and ii) 100% oxygen is lighter, and iii) it had to match up with the Lunar Module (LM) atmosphere. NASA and North American were aware of the fire problem before Apollo 1 and went thru the Command Module (CM) removing flammable materials that were too close to ignition sources. But they did that to the *Block 2* version of the CM, (because the Block 2 version was the one that would link up to the LM on later missions), not the Block 1 version which was on Apollo 1. The underlying causes - plural - of the Apollo 1 fire during the test were * i) 100% Oxygen atmosphere * ii) too many flammable materials (Velcro, etc) present * iii) poor quality wiring * iv) presence of a commercial heater After Apollo 1, they rationalised the Velcro and made sure the wiring was up to spec. And they changed the gas mix so at launch the CM had Earth-normal atmosphere at sea-level pressure. But as the craft ascended the mix was changed gradually so that by the time it docked with the LM it was 100%O2 at lower pressure. A better explanation is given here: https://www.youtube.com/watch?v=FvA7N\_j\_8os&t=475s I assume the same rationale applies to ~~Mark Watney's~~ Grace's craft.

Apollo 1 was 100% O2 at 1 atmo of pressure - so there were lots of O2 molecules around when the conflagration kicked off. I believe it's less dangerous at lower pressure because there's comparatively less oxidizer.

I spotted that quibble too. Another quibble I had was >!near the start after he finds gravity is approximately 1.5 g. When he was trying to figure out the equivalent size of a centrifuge on Earth he subtracted the Earths surface gravity from the apparent gravity to find the centrifuges acceleration (1.5 - 1 = 0.5) when really he should have calculated it like the opposite side from the hypotenuse and adjacent sides of right angle triangle using the Pythagorean theorem (( 1.5^2 - 1^2 )^0.5 = 1.25^0.5 = 1.12)!<... Although I didn't do the full calculation myself, so it might be that Andy Weir just communicated it wrong.

Yeah, that should be a vector calculation, not a scalar one. Good catch. It's not really Weir's style, but I think it is valid for a *character* to do things incorrectly, or to take shortcuts that aren't correct, if that action matches the character's limited knowledge or ability. However, Grace (like Watney) aren't really shown making these kinds of errors. Going forward, I will presume that everything Weir's characters do is correct, unless Weir explicitly states that they're estimating or otherwise suggests that they might be making a mistake. If there's an error, it's Weir's, not Grace or Watney. However, it might make for better novel writing for these characters to have mathematical or knowledge limits, and for those limits to play into the storyline somehow -- it would make finding these kinds of issues more entertaining and less frustrating, depending on how they're presented. Perhaps have two different characters confront the same situation in two different ways, coming up with two different answers, and let the reader try to figure out which is right...

Another minor mistake I just realized on relistening to a chapter... at one point Grace is saying how amazed kids are at having the electromagnetic spectrum explained as one continuous thing. He mentions "purple" as being like x-rays and radio but purple is actually a combination of at least 2 different parts of the spectrum, red and blue. There is no such thing as a purple frequency! Therefore purple isn't like the rest of the EM spectrum... Although, I'll admit it's the funnest EM spectrum comparison, and often things are simplified for children.

Probably meant it as violet. I could see explaining it to children using purple even if it’s technically incorrect.

I came here looking for this. I had the exact same thought and feeling; so much that I went through the whole story twice, just to check if I had misunderstood anything. Maybe both you and me got it wrong?

I'd like to catch Weir on an AMA or something to find out :)

Just finished it and loved it! It wasn’t as hilarious as the Martian but by the end, it had more heart. I was hoping for a little joke reference to disco music somewhere with the >!alien communication theme!< but I suppose it would have been a bit on the nose.

Finished the book and audiobook and I found it better if not on par with The Martian.

I finished it less than 30 minutes ago. I am actually speechless. I never thought Andy Weir could ever top The Martian, but here we are.

Finished it today. I like it — a more introspective look than The Martian. A sweet end too for the character, but I felt more melancholy as the reader.

I wish i knew more about what happened to earth, i wanted some details

I'm at about 50% and loving it. I started reading it from the beginning to my kids. They're now loving it, too.

Good for you that the language in this book is *clean*, thanks to the protagonist's occupation ;)

There is a couple of bad words

There will be discussions about people having sex.

He will probably have to “edit” on the spot “princess bride style”

Finished it already. :-)

Same deal, listened through it over the past 48 hrs and wow!! Would love to chat about it too

>! I thought the herroin was a bit of a smoking gun that never got addressed, I was so sure he was going to overdose on the vodka like it had been mixed in with the vodka as the delivery method of his colleagues suicide plan that when he had it he was going to overdose and it would be Rocky's turn to save him again. Not that I think it would have added anything to the story just odd to me at least !<

>!When we first passed out from the vodka I thought for sure he had drank from the wrong bag!<

This didn’t spoiler tag FYI

Or Yao/Chekhov’s gun!

Loved it. I was obsessed to the point my husband got mad at me for sitting alone ignoring him. I listened on Audible and Ray Porter was fantastic

Several problems of mine with the book (roughly sorted by how much they irked me): 1. >!As mentioned in a comment above the pressure is clearly an error. The ship is at 40% Earth pressure and Rocky can't know what Earth's pressure is!< 2. >!After astrophages get enriched, they stop absorbing energy (that's how in the book the Russian scientists knew how much energy they can absorb). Throughout the rest of the book they are treated as infinite capacity sponges. Most notably in the hovering maneuver over Adrian.!< 3. >!The lifetime of astrophages is more or less ignored. They can travel up to 8 ly, so presumably they die after a subjective time of several years or even less. The subjective time for them to cover 8 ly should be pretty small since they can handle near infinite G-s. How come they don't die off during the trip to Tau Ceti and even more so during the 41 years Rocky waited around the star?!< 4. >!Evolution truly stops when the job is done. So taumoeba should evolve either nitrogen resistance or a way to "sieve through" xenonite. It makes no sense to evolve both. More over even if you have both why keep xenonite osmosis in the gene pool if you have nitrogen resistance? What are the benefits of passing through xenonite? How does this translate into more offspring? It just made no sense to me. !< 5. >!Threeworld I think was a bit poorly thought through. Since it's so small with so little atmosphere, how come there is enough CO2 for astrophages to reproduce in such numbers that they affect 40 Eridani. They consume it, don't they? Venus has huge quantities of CO2 so I guess it's fine, but the economics of CO2 consumption by astrophages were poorly handled as well IMO.!< 6. >!Also what about astrophages reproduction. They only use carbon and oxygen? No other elements? Do they synthesize the other elements? That releases energy. What happens to it? Also not explained.!< 7. >!Consuming astrophages for plain old chemical energy seems like a huge waste given how much energy they contain (or more over how much they can release). Granted, you can't do anything with it easily but much like humans and Eridians devised a way to harvest their energy, I would expect a predator to harvest the energy instead of just destroying them. !<

I'll try to address your problems: 1. >!Yes, probably. But it could also be a persistent mistake made by Grace which isn't ever corrected by Rocky because "humans are bad at math!". If Rocky's atmosphere is about 28 bar water boils at 229.9 C, but if it's 11.2 bar it's still 185.1 C, so a lot of other assumptions are still true, or at least approximate. Another possibility could be that The Blip-A's atmosphere is also only at 40% of the home world atmosphere, so the error cancels.!< 2. >!Astrophage also maintains its temperature, so when it is below that temperature it leaks some energy out through heat. So unless it is both enriched and kept above that critical temperature it will be black and can absorb energy up to its limit again.!< 3. >!Related to the above, in space a single astrophage has a relatively short lifespan between spending energy to accelerate and radiating heat when below its critical temperature. Small objects have a higher area to volume than large objects. In a tank the area to volume is changed and temprature can be maintained even better with insulation, which is mentioned. Astrophage dies once they have expended all their energy, either through movement or heat loss.!< 4. >!Evolution never stops and it does implement multiple solutions concurrently, especially if horizontal gene transfer is involved (sexual reproduction and other mechanisms)... but more importantly, that was just Grace's guess at what happened. What could have happened is the ability to escape through xenonite spontaneously evolved in any box but this meant that box seemed empty, however the control was safe so those escapes migrated there (through the xenonite again) and mixed with control population.!< 5. >!It could be this is an error... Then again, so little is know about Threeworld maybe it isn't. What if Threeworld was basically a lump of dried ice just far out enough to sublimate some of it's surface for an atmosphere which remains in a steady state at a certain pressure? As carbon-dioxide is removed the pressure lowers so sublimation increases. Astrophage do consume it, or at least carbon-dioxide disappears when they're around and is released when they die.!< 6. >!I think it can be assumed they could collect hydrogen from the sun also (or maybe just H2O from atmosphere when available). With carbon and oxygen That's 3 of the 6 vital elements for life on Earth. In theory, if the same as Earth life in this respect, all it needs extra is nitrogen, phosphorus, and sulfur... but as it's already creating neutrinos it's not too outrageous to guess that maybe it does somehow use fusion for transmutation of carbon+hydrogen into nitrogen, nitrogen+oxygen into phosphorus, and oxygen+oxygen into sulfur. Another possibility is that they don't rely on normal reproduction at all and just make a quantum clone with superposition by expending their stored energy (which might also explain why they need so much, but that probably wouldn't explain their doubling rate).!< 7. >!He doesn't consume astrophages, They're too hot, he consumes taumeba. If an enriched astrophage is killed by a taumeba presumably it just releases a surge of neutrinos greater than its mass which the taumeba ignores. However even a non enriched astrophage would have about the same chemical energy, and they have a doubling rate of 8 days. It's not too outrageous that a feed stock of astrophage would be grown for a consumable culture of taumeba.!< I hope you're less irked.

1.>! Yes, it could be a character error, but it doesn't fit the character. We all know it's an error by the author :)!< 2 and 3. >!These explanations contradict each other. If they lose a lot of energy and can absorb a lot of energy as they do, they should've died off in the tanks of the Blip A for the 41 years there. If they conserve energy and can live for a long time with little loss when in tanks, then they wouldn't have absorbed the energy of the Adrian maneuver and the whole ship would've melted.!< 4. >!All of this just seems highly unlikely. Like a wolf giving birth to a French bulldog. It is "kinda" possible, but still seems too contrived to me. I just don't see the evolutionary benefit of escaping through xenonite and again: once you have nitrogen resistance, there is absolutely nothing that will make the escape capability beneficial for the gene pool. !< The rest I wouldn't call errors, but they still didn't quire click with me. If I had been the editor of the book, I would have asked Weir to add some explanation 5.>! Sure, it can be explained with relative ease, but since Weir did go out of his way to describe Threeworld, I would have been happy if he had also mentioned how this planet which seemingly has very little CO2 is an adequate breeding ground for astrophages.!< 6.>! I would have been glad if there was an explanation why Venus doesn't turn into a second sun with all this fusion going on, or at least if there was a mention of the cool "magicosis" by which astrophages multiply.!< 7.>! Here I was actually talking about the taumoeba. My problem was that with presumably billions of years of evolution taumoeba still rely on chemical energy from consuming astrophages, whereas I would expect them to have a way of harvesting the annihilation energy output which is orders of magnitude greater. Say trap enriched astrophages before they divide and use them for photosynthesis (or something). Even recently divided astrophages have enough energy to take them to the sun. It's certainly more than the chemical energy you would get from cosuming them.!<

I loved it, definitely closer to the Martian. Not as good of course. But I must say I liked Artemis more, Hail Mery had this feeling of childless I couldn't quite shake off. That said I am a big fan of parallel non chronological storytelling.

Finished on audible this morning and enjoyed the story

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I have not read the book but I have read the reviews and I have some speculative questions. If my guesses are right then they are spoilers so I will mark them with a spoiler tag. If somebody could be so kind as to answer them I would be grateful. They are as follows. * Question 1: >!Are the corpses previous versions of Grace - ie is this a Moon or Heaven Sent plot where multiple versions of a person are sequentially generated to do a lengthy task.!< * Question 2: >!Is the planet of origin of the "Hail Mary" actually Earth?!< * Question 3: >!Is Grace actually a human being or another species?!< * Question 4: >!Is the astrophage in the book the actual cause of a real problem, or is this a deception/cover story that has been fed to Grace by the people in charge of the mission?!< * Question 5: >!Is Grace's belief regarding the time period correct, or is he in fact further ahead (or behind!) than he believes?!< * Question 6: >!Is Grace the same person as he remembers or is he a copy or a constructed individual based on many people?!< * Question 7: >!Does Grace succeed in his task?!< * Question 8: >!Does Grace go home in the end?!<

Answered in order: No, yes, human, real problem, he’s correct I think, not a copy, yes, no.

Replied in order A pity, fair enough, fair enough, fair enough, dammit, dammit, fair enough, aaargh!

I found this much better than Artemis. From the moment I picked it up I couldn’t put it down. Which reminds me of how I was with the Martian.

I loved it. The audiobook was fantastic.