doc_nano t1_jcb4shc wrote

>For the instances where individual molecules are charged, why do they never form ionic bonds as a result of being charged?

They actually do in many cases. For example, a molecule like acetic acid can lose a H+ ion to become acetate, which has a negative charge, and it can form ionic bonds with sodium to form sodium acetate crystals. In these crystals, negatively charged oxygen atoms from the acetate ion are ionically bonded to the positively charged sodium ions. Different crystal structures can form depending on how much water is present.

Isolated pairs of ions don't tend to stay associated in this manner for a variety of reasons (at least in the condensed phase such as an aqueous solution), but as long as they can form a regular lattice with the right energetics, molecules are perfectly capable of forming ionic bonds.


doc_nano t1_ja2weby wrote

It would be very easy to tell them apart genetically. The chances of anything close to the same genetics would be astronomically small, something like winning the lottery every day of an 80-year life.

However, they would likely be more similar to each other genetically than a random set of 2 human beings of the same gender and ethnicity.


doc_nano t1_j1hnswo wrote

One way to think about it is like artificial flavorings. The flavor of a cherry is complicated, so when a single chemical (usually benzaldehyde) is used to simulate the flavor of cherries or almonds, it’s a poor imitation of the real thing. It’s reminiscent of cherries because benzaldehyde is one of many flavor chemicals in cherries and almonds, but it doesn’t capture the full complexity of their flavor.

Similarly, a human experience like “winning” likely can’t be reduced to a single hormone or neurotransmitter. Brains and bodies are complex, so the experience of reward after winning likely includes many stimuli apart from testosterone - there are many subjective feelings and neurotransmitters/hormones involved in the struggle and victory, and these occur in a certain order during the experience of winning. The secretion of hormones and neurotransmitters is often local and has different effects in different parts of the body. Trying to achieve the same effect by injecting a single chemical is a bit like trying to swat a fly with a sledgehammer.

When the other cues of the struggle and victory are absent, it’s not surprising that even (a subset of) the same chemicals wouldn’t have the same effect. The brain’s expectations have a huge impact on our experience of events (consider the well-known placebo and nocebo effects), so even if we could perfectly simulate the hormonal effects of winning, a part of the subjective experience would be absent, so we might not expect the full effect to be present.

As for the god hypothesis… assuming one exists, he apparently has no problem with cheating, otherwise he wouldn’t have designed cuckoos to deposit their eggs in other birds’ nests so that they wouldn’t have to raise them on their own. Among thousands of examples where cheating occurs in nature and humans, often with impunity!


doc_nano t1_j0sikiu wrote

This is correct. Another good example is trying to read text across the room through a planar mirror if you’re nearsighted. Let’s say you can read text clearly without glasses if it’s a foot away but not if it’s 20 feet away. If you’re standing 1 foot from a mirror looking at text 20 feet behind you, light from the text will have to travel about 22 feet before it reaches your eyes, and you won’t be able to read it without glasses because you’re effectively trying to look at text that is 22 feet away, not 1 foot away.


doc_nano t1_iztz3dj wrote

Just adding this: although genetic mutations are “random” in the sense that whether they happen or not in an individual is, effectively, a roll of the dice, that doesn’t mean the dice are equally likely to land on all numbers. For example, it’s known that one nucleobase (cytosine, C) has an outsized tendency to mutate to thymine (T) because it only has to lose one amino group to turn into uracil, which looks to many enzymes indistinguishable from T. This even happens when you heat DNA in a test tube - a very small fraction of the C’s in that test tube will lose an amino group and become U. (Edit: and if the C was already methylated, it will turn into T if it loses the amino group.) This is actually a nuisance when you are looking for rare mutations in a sample, and can lead to false positives unless you correct for it somehow.

There are many other examples, but even at a chemical level certain DNA bases and sequences are more susceptible to mutation than others. This is at least part of the answer to your question.

Edit: So, while the occurrence of a mutation or not in an individual can be considered an essentially random process in most cases, not all random mutations are equally likely. It’s like if you had a hat full of names and drew a name at random: the likelihood that the name begins with S isn’t the same that it begins with X, just because S names tend to be more common (at least in English). The process can be random and still generate certain outcomes more than others.


doc_nano t1_iydss8q wrote

I don't have that feeling about space, but about deep water. There could be anything down there. Sharks, jellyfish, enormous whales that could swallow me in one gulp. I would never go scuba diving in the ocean for this reason. Yet somehow I find it fascinating at the same time.

Sorry that I don't have any constructive advice. If it's not debilitating, maybe try to appreciate the fear -- after all, it's part of what makes us human? If it is debilitating, probably best to consult a professional.


doc_nano t1_iydruye wrote

Yeah, the scale of space is just so stupidly vast compared to what could ever be traveled in a human lifetime. When the light now reaching us from Andromeda left that galaxy, there were no human beings yet. And that's the closest galaxy of comparable size to the Milky Way. There are galaxies thousands of times farther away than that. Those distances might as well be infinite.


doc_nano t1_iya1u5l wrote

Yeah, it's conceptually pretty similar to that kind of stitching. In some ways stitching the DNA sequences together is less complicated than an image because the data are one-dimensional and you don't need to correct for perspective artifacts for near-field objects. On the other hand it's a crap-ton more data elements than the number of pixels in even an HD image, so overall it's a lot more data to crunch through. And there are different kinds of artifacts that show up in sequencing data (such as read errors or mutations that occur during the copying of the DNA prior to sequencing) that need to be dealt with.


doc_nano t1_iy91y85 wrote

There are many ways one could do sequencing, but most modern sequencing involves chopping a genome into much smaller chunks at random, sequencing all those chunks, and using lots of computer power to see how all those chunks fit together originally ("shotgun" method). Since the chunks start and stop in (basically) random places, you will often find two different chunks that have the same sequence that came from different copies of the genome, and you can use that overlap to figure out how the whole thing fits together. This works really well for the most information-dense parts of the genome, and you can get a good sense of how complete it is by how frequently the same sequences pop up again and again (something called "depth" in the sequencing field). If most sequences pop up 10 or 20 times and you aren't getting any new sequences, there's a good chance you've sampled all the genome that you're going to see.

A hiccup is that large parts of the human genome and the genomes of many multicellular eukaryotic organisms contain very large, repetitive sequences of DNA. In this situation, you can't break the DNA into smaller chunks and expect to piece it back together, since different fragments of the repetitive sequence will look the same and you can't see how long that stretch really is. This is where you need to use other approaches such as long-read sequencing. However, the same logic applies: when you've sampled most of the genome many times over without uncovering anything new, the statistical probability that you're missing something is quite low.


doc_nano t1_ixejbu4 wrote

They do orbit very close, but are still within the habitable zone because their star is an ultra-cool red dwarf. The fact that they orbit so close/quickly was part of what made them (relatively) easy to detect.

I think there are still serious doubts about them harboring life because their proximity to their star and its radiation might prevent any long-term retention of an atmosphere. But opinions seem to vary and we likely won't know for sure until more data come in.


doc_nano t1_iwrhkud wrote

BTW, here is a handy calculator to figure out how the passage of time changes as you approach the speed of light relative to other reference frames.,measured%20by%20the%20moving%20observer.


doc_nano t1_iwrgmm7 wrote

Let's say you took a trip to Alpha Centauri, about 4 light years away, going 90% the speed of light all the way there and back (we'll pretend you don't need to accelerate and decelerate). To observers on Earth, about 8.8 years would have passed before you return. However, from your perspective, only about 3.8 years would have passed. Your biological age would have increased by 5 years less than everybody else, though each person would feel as though time had passed normally for them.

Edit: as a side note, if you could travel at 99.9999% the speed of light, you could get to the center of the Milky Way galaxy and back within a typical human lifetime. Of course, back on Earth more than 50,000 years would have passed and humanity might not be here anymore.


doc_nano t1_iwpw3nx wrote

Great graphic! My understanding from a little googling is that Apollo 11 took a little over 4 days to reach the moon. Do you know why the outbound transit is expected to take 8-14 days for the Artemis mission, per the graphic?


doc_nano t1_iuwuoze wrote

I don't blame you for being confused -- there is no single standard for comparing how similar two genomes are, since it depends a lot on what kind of comparison you're making. Nucleotide-for-nucleotide, you are right that there are almost no differences between the protein-coding sections of Homo sapiens and Neanderthal genomes. I don't know the exact number off hand, but it's surely much closer to 100% identity than 99%.

However, when people talk about what % Neanderthal DNA a person has, it's usually talking about larger "chunks" of the DNA. This is a measure of heredity that is more akin to saying a person has 50% European ancestry and 50% Asian (or whatever). The European and Asian human genomes are almost 100% identical, but you could analyze that person's DNA to figure out what fraction of the DNA was likely to have come from European populations and what fraction was likely to come from Asian populations. A common way to do this is to look for single-nucleotide variants (called SNPs or "snips") that are common in one population but rare in others. If you find several such SNPs in a region of the genome, the probability is high that the person has heredity from that population.

Edit: Also, it gets even more complicated when you start taking into account non-protein-coding parts of the genome, which can be more variable in sequence and size, as well as situations where whole parts of the genome might have been duplicated.