> This discovery also links to another important finding of the last decade – the first chiral molecule in the interstellar medium, propylene oxide. We need chiral molecules to make the evolution of simple lifeforms work on the surface of the early Earth.
It would be really amazing if we were able to know if both chiralities are equally represented in the space. Apart from the life itself it is astonishingly interesting how life evolved to be monochiral.
Life has to be monochiral because biochemical reactions are catalyzed by physical machines- enzymes, where an entirely different physical shape of the enzyme active site would be required for it to work with the opposite isomer. Any particular DNA sequence that evolves to make a protein will only be able to work with one orientation- unless the enzyme was so floppy and flexible that it reacts with everything, which would be inherently dangerous to a living cell.
Think about trying to “evolve” a glove that fits perfectly on both hands yet is also specific and does not accidentally fit onto non-hands… it would be much harder and less likely than evolving one that only fits left or only right hands.
Spontaneous chemical reactions that make the things we find in space never had to physically fit into a machine like a key into a lock, so both chiral isomers are equally likely to form.
"Both" don't have to be represented in the same place at the same time. And even then, I could imagine them competing. I mean if both can work, why should only one exist?
PS: I mean both as in separate ecosystems. Not arguing that one organism could contain both.
I agree, but as far as we know life evolved only once, and particular chiral orientations in central carbon metabolism were then locked forever, because they can't be changed without breaking everything else. The same enzymes won't generally work with both steroisomers- every enzyme they interact with needs radical structural changes.
Less critical things outside of central carbon metabolism often do evolve different stereoisomers in different species, or even the same species. For example, the large macrocyclic antibiotic molecules sometimes evolve to flip sterochemistry, creating a new antibiotic.
there is a good argument to be made that there is exactly one life form on this planet,with various
sub types speaking different dna dialects, and there exists a kind of universal mutual comprehension of the base language in between all life forms
the explanation of chirality is very good
Doesn't matter. The names for the directions are arbitrary and you can pick whatever frame of reference you like. The question was only if the directions are distributed randomly.
Rotation can be described as a vector, pointing along the axis of rotation. You could imagine writing down the vectors for all of the objects in a planetary system, and doing some kind of statistics on the numbers to see if there was a preference for a particular axis. You could use a sign convention such as the right hand rule.
The rotation vector is associated with another, which is angular momentum. The reason why there's all kinds of spinny stuff in a solar system, or a galaxy, is that the massive objects jointly conserve the total angular momentum of the blob of dust that the system coalesced from.
Neutrinos are another beast, they have a preference for one direction of their spin quantum number:
To put the questions differently: assume we look at all the planets from the perspective of a single point (say, Earth), why do some spin one way (cw) and some spin the other way (ccw)? Are cc and ccw evenly distributed?
They seem to spin in different directions because you are observing them from a single point - earth.
Consider the following. You and I are standing on opposite sides of a pane of glass. I spin a wheel parallel to the pane of glass and we both observe it. From my side of the glass the wheel is spinning clockwise. From your point of view (because you are seeing the opposite side of the wheel) it is spinning counterclockwise.
Whether a given rotation is clockwise or counterclockwise depends entirely on your reference frame - they really don't have a robust definition that doesn't depend on the pov of the observer.
There is a really excellent and clear description of the problem and solution to this that is employed in classical mechanics here[1] but if you only care about the solution, by convention we employ the right hand rule. If you and I both agree a common direction in the plane of rotation of the wheel say parallel to the floor off to the side (whichever side doesn't matter but for one of us it will be to the left and the other right), point our right hand index finger in that direction (called r hat or the direction of radial motion) and curl our two smallest fingers in the direction of rotation of the wheel, our thumbs will be pointing parallel with one another. This would be called n hat (normal motion), and is the direction of any vectors which are the cross product of two vectors in the plane of rotation of the wheel. As a bonus if you make your right hand middle finger perpendicular to the index finger you have theta hat (tangential motion). Now even though you and I can't agree whether the wheel is spinning clockwise or counterclockwise we have three identical basis vectors and can use these to form a common polar coordinate system to describe this rotating system.
I'm trying to say it doesn't matter where you observe it from. If one thing is spinning one way, and another the opposite way. Whether you see it from your side, or my side, the directions of the two things are opposite. Am I wrong?
For the purposes of saying which spin there are more of (and we have observed a slight preference for one), we'd need to agree on which one is cw and which way is ccw. The slight bias is for ccw, as viewed from out planets North Pole, though it's not known if this is merely an observation bias or pervasive.
They are asking whether the distribution of the direction of rotation of all rotating celestial bodies is equally distributed, for this it is irrelevant which direction of rotation is designated and how.
If you consider the North Pole to be the top of the Earth, then the Earth rotates counter clockwise, and so does the Sun, and the Earth orbits the Sun ccw also.
This is true for most of the other planets also and they orbit in the same plane.
And this is true for most stars in the galaxy and the rotation of the galaxy itself too.
And if you consider the South pole to be the top of the Earth then the Earth rotates clockwise and so does the sun and the eath orbits the sun clockwise also. It's pretty much all an arbitrary convention and depends on your frame of reference.
If you define North to be "the pole that if it's on the top then things rotate counterclockwise" and that's consistent then that's equivalent to the definition of an orientable Euclidian space I think, and I'm glad that's the case for our universe because things would be mighty weird if it weren't. You could shift your breakfast around the table and it would come back as a mirror image of itself.
Joking aside as I understand it any orientable 3-d space admits two orientations, which are defined by the choice of the surface normal n. If you do it the way I said in a sibling post with the right-hand rule then n is pointing paralel to the axis of the Earth with positive in the direction of the North pole, the rotation is counterclockwise from that perspective and everything is groovy. But we could equally use our left hand, our thumb would point South and the rotation of the Earth would be clockwise. In that case we are choosing to orient using the other possible surface normal (-n).
If you take the South Pole as the top, then the Earth rotates clockwise, which is the SAME (this is the important bit) as the Sun, which is the SAME as the solar system, which is the SAME as the Galaxy. They're (nearly) all clockwise.
The Sun and most planets and in general stuff rotates in the same direction because it formed from a cloud that had some movement, caused by a bifurcation at some point of its formation. Bifurcation meaning losing balance in chaos and moving away from that initial unstable equilibrium into a significant motion.
So it shouldn't be surprising stuff is for the most part moving in the same direction. It's surprising when something isn't, probably because it was hit by some body changing its angular velocity.
Hate to disappoint anyone searching, but it turns out two of them were vestigial and fully enclosed, to the point the deceased individual probably never realized it. Although if he did, giving his body to medical science was a great way to let everybody else know...
Does uBlock leave some kind of explanation in the place of the ad telling you what overall quality of ad it was? Like, the message you are responding to isn't complaining about having to see the link: they are noting that this kind of cross-promotion might lead one to discredit the content we are reading, as it is kind of an important signal, not merely noise.
ha ha ha ha,I so lucky!,I block everything,and get away with it!
the largest part of my reading on hn is the comments,as many many of the commentors know a lot more than the writers and scientist,and just realised that if it were not for some brave volenteers reading the articles to get the comments going,I would be so much poorer
I'm beginning to think that I might remove them from my source. Almost all of their articles are reprints of the reprints of originals from elsewhere. I haven’t checked and cleaned my sources in more than a year. I will do a retrospection during the yearly cleanup in December.
Do you have any recomendation? Sometimes the same press release is posted by different news blogs. If there is a better one or the original one, dang may decide to change it.
> This discovery also links to another important finding of the last decade – the first chiral molecule in the interstellar medium, propylene oxide. We need chiral molecules to make the evolution of simple lifeforms work on the surface of the early Earth.
It would be really amazing if we were able to know if both chiralities are equally represented in the space. Apart from the life itself it is astonishingly interesting how life evolved to be monochiral.
Life has to be monochiral because biochemical reactions are catalyzed by physical machines- enzymes, where an entirely different physical shape of the enzyme active site would be required for it to work with the opposite isomer. Any particular DNA sequence that evolves to make a protein will only be able to work with one orientation- unless the enzyme was so floppy and flexible that it reacts with everything, which would be inherently dangerous to a living cell.
Think about trying to “evolve” a glove that fits perfectly on both hands yet is also specific and does not accidentally fit onto non-hands… it would be much harder and less likely than evolving one that only fits left or only right hands.
Spontaneous chemical reactions that make the things we find in space never had to physically fit into a machine like a key into a lock, so both chiral isomers are equally likely to form.
"Both" don't have to be represented in the same place at the same time. And even then, I could imagine them competing. I mean if both can work, why should only one exist?
PS: I mean both as in separate ecosystems. Not arguing that one organism could contain both.
I agree, but as far as we know life evolved only once, and particular chiral orientations in central carbon metabolism were then locked forever, because they can't be changed without breaking everything else. The same enzymes won't generally work with both steroisomers- every enzyme they interact with needs radical structural changes.
Less critical things outside of central carbon metabolism often do evolve different stereoisomers in different species, or even the same species. For example, the large macrocyclic antibiotic molecules sometimes evolve to flip sterochemistry, creating a new antibiotic.
there is a good argument to be made that there is exactly one life form on this planet,with various sub types speaking different dna dialects, and there exists a kind of universal mutual comprehension of the base language in between all life forms the explanation of chirality is very good
Does propylene oxide demonstrate a "propeller effect" like some other handed chiral molecules?
From https://news.ycombinator.com/item?id=41873531 :
> "Chiral Colloidal Molecules And Observation of The Propeller Effect" https://pmc.ncbi.nlm.nih.gov/articles/PMC3856768/
I wonder something similar on a larger scale...
I wonder if planets revolve around stars cw vs ccw evenly distributed.
(and could these kinds of things be related?)
> I wonder if planets revolve around stars cw vs ccw evenly distributed.
Depends on whether you view it from one side or the other, no? Or, how do you define which side of a planetary system is the "top"?
Doesn't matter. The names for the directions are arbitrary and you can pick whatever frame of reference you like. The question was only if the directions are distributed randomly.
Rotation can be described as a vector, pointing along the axis of rotation. You could imagine writing down the vectors for all of the objects in a planetary system, and doing some kind of statistics on the numbers to see if there was a preference for a particular axis. You could use a sign convention such as the right hand rule.
The rotation vector is associated with another, which is angular momentum. The reason why there's all kinds of spinny stuff in a solar system, or a galaxy, is that the massive objects jointly conserve the total angular momentum of the blob of dust that the system coalesced from.
Neutrinos are another beast, they have a preference for one direction of their spin quantum number:
https://neutrinos.fnal.gov/mysteries/handedness/
In fact you could use the spin of neutrinos to say that the sign convention for rotation is not arbitrary.
To put the questions differently: assume we look at all the planets from the perspective of a single point (say, Earth), why do some spin one way (cw) and some spin the other way (ccw)? Are cc and ccw evenly distributed?
They seem to spin in different directions because you are observing them from a single point - earth.
Consider the following. You and I are standing on opposite sides of a pane of glass. I spin a wheel parallel to the pane of glass and we both observe it. From my side of the glass the wheel is spinning clockwise. From your point of view (because you are seeing the opposite side of the wheel) it is spinning counterclockwise.
Whether a given rotation is clockwise or counterclockwise depends entirely on your reference frame - they really don't have a robust definition that doesn't depend on the pov of the observer.
There is a really excellent and clear description of the problem and solution to this that is employed in classical mechanics here[1] but if you only care about the solution, by convention we employ the right hand rule. If you and I both agree a common direction in the plane of rotation of the wheel say parallel to the floor off to the side (whichever side doesn't matter but for one of us it will be to the left and the other right), point our right hand index finger in that direction (called r hat or the direction of radial motion) and curl our two smallest fingers in the direction of rotation of the wheel, our thumbs will be pointing parallel with one another. This would be called n hat (normal motion), and is the direction of any vectors which are the cross product of two vectors in the plane of rotation of the wheel. As a bonus if you make your right hand middle finger perpendicular to the index finger you have theta hat (tangential motion). Now even though you and I can't agree whether the wheel is spinning clockwise or counterclockwise we have three identical basis vectors and can use these to form a common polar coordinate system to describe this rotating system.
[1] https://www.youtube.com/watch?v=q785KV5ZIN0&t=45s
I'm trying to say it doesn't matter where you observe it from. If one thing is spinning one way, and another the opposite way. Whether you see it from your side, or my side, the directions of the two things are opposite. Am I wrong?
For the purposes of saying which spin there are more of (and we have observed a slight preference for one), we'd need to agree on which one is cw and which way is ccw. The slight bias is for ccw, as viewed from out planets North Pole, though it's not known if this is merely an observation bias or pervasive.
They are asking whether the distribution of the direction of rotation of all rotating celestial bodies is equally distributed, for this it is irrelevant which direction of rotation is designated and how.
hmmm, maybe not as analogous to chirality as I thought?
If you consider the North Pole to be the top of the Earth, then the Earth rotates counter clockwise, and so does the Sun, and the Earth orbits the Sun ccw also.
This is true for most of the other planets also and they orbit in the same plane.
And this is true for most stars in the galaxy and the rotation of the galaxy itself too.
So it's pretty much all counter-clockwise.
And if you consider the South pole to be the top of the Earth then the Earth rotates clockwise and so does the sun and the eath orbits the sun clockwise also. It's pretty much all an arbitrary convention and depends on your frame of reference.
If you define North to be "the pole that if it's on the top then things rotate counterclockwise" and that's consistent then that's equivalent to the definition of an orientable Euclidian space I think, and I'm glad that's the case for our universe because things would be mighty weird if it weren't. You could shift your breakfast around the table and it would come back as a mirror image of itself.
Joking aside as I understand it any orientable 3-d space admits two orientations, which are defined by the choice of the surface normal n. If you do it the way I said in a sibling post with the right-hand rule then n is pointing paralel to the axis of the Earth with positive in the direction of the North pole, the rotation is counterclockwise from that perspective and everything is groovy. But we could equally use our left hand, our thumb would point South and the rotation of the Earth would be clockwise. In that case we are choosing to orient using the other possible surface normal (-n).
If you take the South Pole as the top, then the Earth rotates clockwise, which is the SAME (this is the important bit) as the Sun, which is the SAME as the solar system, which is the SAME as the Galaxy. They're (nearly) all clockwise.
The Sun and most planets and in general stuff rotates in the same direction because it formed from a cloud that had some movement, caused by a bifurcation at some point of its formation. Bifurcation meaning losing balance in chaos and moving away from that initial unstable equilibrium into a significant motion.
So it shouldn't be surprising stuff is for the most part moving in the same direction. It's surprising when something isn't, probably because it was hit by some body changing its angular velocity.
The same goes for the alignment of equators.
Samples from space of an iso-energetic chiral molecule are going to show a racemic mix. Unless there's a discrete reaction path favoring handedness.
Just saying that on the same webpage there was a link to an article about the guy with three p*nises...
Hate to disappoint anyone searching, but it turns out two of them were vestigial and fully enclosed, to the point the deceased individual probably never realized it. Although if he did, giving his body to medical science was a great way to let everybody else know...
I was rather under impression that this whole news source was just spreading things catchy but made up, including said carbomolecule..
uBlock is your friend unless you're in to that sort of thing. Not that there's anything wrong with it...
Does uBlock leave some kind of explanation in the place of the ad telling you what overall quality of ad it was? Like, the message you are responding to isn't complaining about having to see the link: they are noting that this kind of cross-promotion might lead one to discredit the content we are reading, as it is kind of an important signal, not merely noise.
ha ha ha ha,I so lucky!,I block everything,and get away with it! the largest part of my reading on hn is the comments,as many many of the commentors know a lot more than the writers and scientist,and just realised that if it were not for some brave volenteers reading the articles to get the comments going,I would be so much poorer
This is a shitty news source, please use a better one
I'm beginning to think that I might remove them from my source. Almost all of their articles are reprints of the reprints of originals from elsewhere. I haven’t checked and cleaned my sources in more than a year. I will do a retrospection during the yearly cleanup in December.
Do you have any recomendation? Sometimes the same press release is posted by different news blogs. If there is a better one or the original one, dang may decide to change it.
MIT News perhaps https://news.mit.edu/2024/scientists-discover-molecules-stor...
[flagged]