It is so massive he has to make affordances Epstein never had to. You can visit Lanai today for example. I took a day trip there a couple years ago. Saw the cat sanctuary. Not much else to do there. There is a little holdover company town inland from the Dole days but I didn't visit that. I'm not sure how much time Ellison even spends there. I get the sense that having these some 3k common folk holdout residents plus visitors makes it a bit less attractive than it might have seemed when he signed his name on 98% of a Hawaiian island. Seems a couple years ago he shifted his primary residency to his mansion near Mar a Lago. Bored of the plaything now, I guess.
It is just bizzare when you take a step back and remember the world 20 years ago. NASA would just post directly to their own website. Of course they would. Now imagine you go back in time 20 years ago and say "What if we took all these images you are providing for the public on their dime, compressed the hell out of them, and served them in this for profit proprietary marketing/propaganda app instead?" Engineers in 2006 would have probably looked at you like you had three heads. The question would make no sense back then.
Something to think about when we consider what is "normal" today. Not much really is normal. We've been beaten to think it is.
I feel that this is somewhat orthogonal. Yes, some questionable things have happened that made the ways how people exchange information be controlled by a handful of corporations.* But for NASA specifically, this is not relevant. They were not the ones who forced people to go to social networks; they needed to go there because this is where their audience was.
* On that note, and for the sake of the argument, I would say that the years of free uncontrolled information exchange in the Internet can probably be considered an exception. Information exchange was always controlled by governments and businesses (e.g. TV and newspapers) before, just as it is now. The fact that you or I don't like it does not change that this is how it used to be before the Internet appeared as a "free space". My generation was lucky to see how great the world with free information exchange could be, but I don't have much hope that it would stay like that for long.
I don't see the left handed aspect as necessary for life. To me this just suggests our common ancestor for life on earth made use of this chirality. Another group of organisms somewhere else could have evolved from an ancestor that makes use of right handed chirality. Or one that is hand-blind.
It seems that the choice between left-handed and right-handed amino-acids was random.
However, it is unlikely that other kinds of life forms could use both kinds indiscriminately, because mixing them creates difficulties in the assembling of polymers. So it is likely that amino-acids produced by some extra-terrestrial life form would also be predominantly of only one orientation, but it could happen to be the right-handed variant.
Moreover, extra-terrestrial life forms could use very different complex amino-acids, because there are much more of those than the 11 that have been added to the simple amino-acids in the terrestrial proteins.
That makes sense that the chirality can affect downstream polymer assembly or even folding in the higher order structures.
Likely we are all left handed on earth because our left handed ancestor outcompeted the right handed organisms in the primordial soup. Or the right handed organisms just didn't evolve in the first place here on earth and there was nothing to outcompete. There might still be some higher order advantages to shifting chirality one way or another. Certain molecules, such as methamphetamine, have differing bioactivity based on chirality. Maybe this can be regulated in some way such as to control the rate of some other downstream process. In an abstracted sense, chemists here on earth are already this organism as they refine reactions to produce desired chirality and reduce expenditure on undesired chirality.
ET could be using different amino acids, or more or fewer. I would hazard to guess there is immense selection to reduce the amino acid set to its most necessary components. This pressure has gotten to the point here on earth where even these necessary components might not all be produced endogenously by the organism who needs them, but consumed from the environment saving energy spent on synthesis. But this requires your neighbor to be producing these AAs, such that you consume them, and you having sufficient feedback mechanisms to not immediately consume all of your neighbor's species and put your own insufficient lineage to extinction.
The living beings use much more amino acids than those that compose proteins.
The relatively low number of amino acids that are used in proteins appears to be caused by the difficulty of modifying the genetic code by adding not yet encoded amino acids to the set of encoded amino acids.
Variations of the genetic code are known at various living beings, but nonetheless they are very rare, because a change in the genetic code requires a lot of other coordinated changes. A new kind of transfer RNA must be encoded in the genome (the only likely origin of such a new tRNA is a mutation in one of the existing) and that RNA molecule must be able to bind preferentially to the codons that are repurposed to encode a new amino acid, and also to molecules of that amino acid, which requires a lot of favorable change is the molecular structure of that RNA.
It seems that in the earliest form of genetic code, there were only 4 distinct symbols, i.e. of the 3 nucleobases of a codon only the central one was meaningful and the 2 peripheral nucleobases did not encode information.
The 4 original symbols selected between 4 major kinds of amino acids: the special amino acid glycine, an acid amino acid, a hydrophobic amino acid and an amino acid with intermediate behavior, like alanine or proline.
These variations would have been enough to build proteins with specific conformations.
The fact that a codon had 3 nucleobases, presumably to ensure the binding to transfer RNA molecules, even if only one of them encoded information, appears to have been a great luck, because this allowed later the expansion of the genetic code, because 3 bases give 64 combinations allowing the encoding of up to 64 symbols.
Most of the possible codons have remained ambiguous until today, but the number of encoded amino acids has increased slowly in time, up to 21, the most recent additions to the encoded set being those of the sulfur-containing amino acids, aromatic amino acids and selenium-containing amino acids.
As you say, there are disadvantages in using many kinds of amino acids, but there are also advantages, by allowing the creation of proteins with properties that are not achievable with a smaller set of amino acids.
The balance between advantages and disadvantages appears to have slowed down continuously the rate of adding new amino acids to the set encoded in the genetic code, so that the majority of the living beings of today have not added any new amino acid since several billion years ago.
Most of the expansions of the genetic code happened before the last common ancestor of all living beings of today, so that today there are very few living beings with more recent modifications in the genetic code.
Life can even use something other than amino acids. They are really inconvenient when you think about it. Fixed nitrogen is extremely rare, and there are no nitrogen-containing minerals other than some exotic exceptions.
Amino acids are useful because they can be easily joined together and split apart (via the C-N bond). But there are other types of "molecular glues" that are viable, like sulfur or phosphorus.
Amino acids are much more likely to be involved in the appearance of life anywhere than other molecules.
For instance it would be much less surprising if an alien life form used another kind of polymer to store information, instead of nucleic acids, than if it would not use amino acids. The fact that on Earth the living beings eventually used ATP and RNA appears to have been determined in great part by chance, while the use of amino acids seems to have been much more deterministic.
Some of the simple amino acids are very easy to be synthesized in abiotic conditions, which is why they are ubiquitous in many celestial bodies.
The advantage of amino acids is that they do not contain only one end that can be attached to other molecules, but that they contain two such ends. A molecule with only one connector would attach to another, forming a dimer, after which no further reaction is possible.
A molecule with two connectors, like an amino acid that has both a carboxyl end and an amine end, can be daisy chained into a polymer of arbitrary length. This allows building complex structures.
There are other molecules with two connectors, but they are much more unlikely to appear in abiotic conditions.
Thioesters, i.e. a kind of organic molecules that are bound by a sulfur bridge, like you mention, appear to have been much more important when life has appeared on Earth than today, but such molecules were important as intermediates in metabolic reactions, not as structural blocks, like amino acids, and there are no known naturally-produced molecules with sulfur that could be used as easily as amino acids to make molecules with arbitrary complex shapes.
> The fact that on Earth the living beings eventually used ATP and RNA appears to have been determined in great part by chance, while the use of amino acids seems to have been much more deterministic.
It looks like on Earth the RNA was the initial replicant. RNA can be folded into complex shapes and can have catalytic properties in itself. Ribosomes that assemble proteins have RNA at the active site with proteins only providing structural framework.
That's why amino acids might not end up being so universal.
Biochemists have been doing just that for like 100 years. They'd take a bunch of yeast, grind the cells into a slurry releasing whatever is inside, separate the cell debris, and perform experiments measuring fermentation rate.
Same issue as with cliffnotes. Easy way out means the easy way will be taken. Unless, you actually design a decent assignment or exam. In person essays or exams, heavily weighted, you are simply screwed if you didn't study the old fashioned way. A couple of my more serious classes were like this: no homework, no projects, entire grade based on 3 exams. That put the fear of whatever diety you subscribe to into you like nothing else to study hard and not fall behind. One bad exam you can't really come back from. Better luck next year when you retake it. Or, you dig in like hell.
3 tests was already better than the traditional Spanish university class: 1 exam. which is probably written by the department head, not your teacher, and he isn't in any way interested in a high pass rate. Failing 90% of the class might even be positive for them. At that point classes aren't even important: You purchase the tests from the last 10 years, and then you have a prayer of knowing what the bar might be this year.
Teaching, fairness and measuring student performance might seem like similar goals, but it's just so very easy to make sure you succeed at one while messing up the others.
> Teaching, fairness and measuring student performance might seem like similar goals
What? Teaching and measurement are very different goals. The whole point of teaching is to mess with measurements.
This automatically means, by the way, that a huge conflict of interest exists whenever the same party is supposed to be responsible for both instruction and measurement. That's why assessment in a traditional Spanish university is out of the hands of the professor. We should aspire to be more like them.
I tested out of all but the last required Spanish class so I probably skipped over some early stuff and avoided the deeper stuff. But at that level I remember we'd do oral exams with the TA 1 on 1 maybe 15 mins in the hallway. I forget the logistics of it all now. I remember making presentations and class participation in spanish being important. I can't remember how the written exams went.
The insidious thing here is that students can think they're studying and practicing by chatting with an AI "tutor", which shifts them into a passive observation role that's no better than watching YouTube videos.
It turns out that it's much less memorable if you're too "clear and helpful", so nothing helpful sticks for students. A good teacher (tutor, educator, pick a word) challenges students and makes them the right amount of uncomfortable.
These resources often suck for the college major level anyhow. Youtube and such is all dumbed down usually. Or if it isn't dumbed down, you risk studying beyond the scope of the lecture. Every class I took, the professor would say something like "anything in lecture could end up on the exam." And indeed, every exam was comprised of something that came from the slides, and nothing that didn't come from the slides. Even if there was an assigned textbook, there would be so much skipped over, either subtopics or entire chapters. Emphasis can vary by lecturer for the same class as well. The class might fall behind or run ahead of whatever is outlined on the syllabus; that is more an aspirational goal than a solid plan of what to expect.
The best tutor, as always, is your TA or professor, during office hours that you already pay for in tuition. No one takes advantage though, well the students who were getting As already do just to validate their understanding. The students who really ought to go never go.
I'm a college (physics) professor, and last semester specifically had a huge shift in student behavior. In introductory courses, students basically stopped coming to help sessions.
I give a substantial amount of extra credit for attending regular help sessions which yielded about 30% help session conversion in past semesters. This term it dropped below 5%, and those few who came were the ones who were high B/ low A students. The solid A students don't come because they don't need to. The low B and lower students didn't come because they thought they didn't need to? It's unclear, but clearly something changed.
Students performing in the mid-B and up range weren't affected, but below that? The bottom dropped out. Students who should have earned B's earned C's. Students who could have earned C's... didn't.
I used to love classes like that and now that I’m a few decades beyond university, I realize they helped me the most. That do it properly now or everything is going to suck is a good prep for the real world.
How could you tell? I proctored. People cheat pretty frequently and other students are none the wiser. It really takes like 4 proctors if you want to do it right. Even then I'm sure the clever ones are slipping through. These were scantron though. Short response/essay format you'd be screwed if you didn't know your stuff.
reply