Author Topic: Loose Thoughts About Physical Reality  (Read 853 times)

Offline trdsf (OP)

Loose Thoughts About Physical Reality
« on: June 02, 2017, 01:16:34 PM »
Just bouncing some things around inside my head.  Feel free to join in.

'Visible light' is an anthropocentric term.  There's nothing inherent in those particular wavelengths that makes them visible, it is our ability to perceive them that makes them visible.  Had we evolved around a dimmer sun, the range that we call 'visible' could easily be shifted into longer wavelengths.  Had there been an evolutionary advantage to being able to see by microwave radiation, we would call that the visible spectrum, and many species on Earth do have different ranges of what they would call 'visible' -- bees seeing into the ultraviolet, or snakes into the infrared, or even some birds that can sense the magnetic field of the earth.  Were any of them the dominant species, they would call their particular range 'visible light', and it would not be the same as ours.  By the same token, we can't assume that other intelligences in the universe would consider the same stretch of radiation 'visible light'.

...but...

There are some good physical reasons that the vicinity of what we call 'visible light' should be the electromagnetic range of choice for any entity evolving organs of detection.  First and foremost, stars with the kind of stable life span that gives time for evolution to do its thing emit strongly in this range.  Our own sun emits most strongly at around 500nm (green, oddly enough), which is smack in the middle of the spectrum we've evolved to perceive, and comparably long-lived stable stars also peak in that vicinity (or longer in the case of red dwarfs).  So it's not unreasonable to suggest that on average, species that evolve the ability to detect electromagnetic radiation will tend to detect this particular range from the infrared to the ultraviolet.  Also, the wavelengths involved are short enough that they tend to reflect off atoms (okay, okay, are absorbed and re-emitted by them) rather than ionize them like shorter wavelengths do, or slip past them with barely a whisper (or only induce heating) like those with wavelengths larger than the atomic scale.

So I don't know.  Is the phrase 'visible light' unnecessarily anthropocentric, or are there good reasons that evolution would favor development of detection of that range of electromagnetic radiation?
"It's hard to be religious when certain people are never incinerated by bolts of lightning." -- Calvin and Hobbes
"I thought I committed regicide today, but I committed deicide!" -- Sadie Doyle, Beyond Belief

Re: Loose Thoughts About Physical Reality
« Reply #1 on: June 02, 2017, 05:05:59 PM »
As you say, it's right at the range produced by our local star. Any life out there should perceive, in the same way, the light that their particular star emits. So you're right, the term "visible light" is only so in relation to us and the light we perceive.

Actually, though, the sun is larger than about 95% of stars, so if life can evolve in systems with smaller stars, their visible range would be toward the longer wavelengths, so most life would probably have a visible range toward the redder end of the spectrum.
God Not Found
"And God promised men that good and obedient wives would be found in all corners of the world... then He made the earth round...and laughed and laughed and laughed...."
unknown

Offline trdsf (OP)

Re: Loose Thoughts About Physical Reality
« Reply #2 on: June 03, 2017, 02:48:59 PM »
Yeah, there's been an amazing turnaround in the last couple decades about what does and does not constitute a habitat.  When I was small, the best speculation about life elsewhere in our own solar system was limited to lichens on Mars, and Sagan and Salpeter's ingenious ideas about life in Jupiter's clouds, and that was pretty much it.  Everywhere else was too hot or too cold or too airless.

Now just in our own solar system, we not only consider those two, but also the clouds of Venus and the subsurface oceans of Ganymede, Enceladus, Europa and Titan as potential habitats.  Eight habitats (one confirmed, seven hypothetical) in just one solar system certainly forces us to think more broadly when looking for extrasolar life.

I'm not sure what I think about the chances of complex life on a tidally-locked world around a red dwarf.  They're certainly long-lived enough to allow enough time for biological evolution, but I wonder if the relatively fixed environment would encourage development beyond simple multicellular life.  The weather on such a world would be constant, within limits -- there would be no seasons and no tides, and the effects of those on evolution must be profound.

So now I think I'm leaning towards an argument that intelligent life would probably mark the range of 'visible light' as roughly similar to ours, because I suspect you're going to need a variable environment to keep pushing speciation, and that means a star that's large and bright enough to have a habzone sufficiently distant that the planet (or planets) orbiting therein does not rapidly become tidally locked.

That is going to generally rule out red dwarfs as hosts for intelligences, but they are probably going to be the most common hosts for simple life just because there are so many of them.
"It's hard to be religious when certain people are never incinerated by bolts of lightning." -- Calvin and Hobbes
"I thought I committed regicide today, but I committed deicide!" -- Sadie Doyle, Beyond Belief

Offline SGOS

Re: Loose Thoughts About Physical Reality
« Reply #3 on: June 04, 2017, 10:41:54 AM »
Evolution seems to revolve around DNA or some similar mechanism, so I'm wondering how likely it is that DNA or some similar mechanism is bound to occur.  Is it likely or not? If it isn't, evolution is not going to happen.  As for life itself, I have the same question.  It seems that atoms have a propensity to combine in many ways.  We know that the possible combinations are not infinite.  Certain atomic combinations appear to be impossible.  Did the combinations that lead to life on Earth just occur as an unlikely fluke, or are they of the nature that given time they are likely to happen?  Life isn't a miracle, unless you believe it is.  There isn't anything remarkable about life, unless you think it's remarkable.  All it seems to be is a certain combination of atoms.  Different combinations produce substances with different characteristics.  Life is just one characteristic of certain combinations, and there may be more combinations that are possible than the combination we know of.  It just hasn't happened on Earth.

Is that a loose enough thought to be in keeping with this thread?

Offline Baruch

Re: Loose Thoughts About Physical Reality
« Reply #4 on: June 04, 2017, 12:44:01 PM »
Evolution seems to revolve around DNA or some similar mechanism, so I'm wondering how likely it is that DNA or some similar mechanism is bound to occur.  Is it likely or not? If it isn't, evolution is not going to happen.  As for life itself, I have the same question.  It seems that atoms have a propensity to combine in many ways.  We know that the possible combinations are not infinite.  Certain atomic combinations appear to be impossible.  Did the combinations that lead to life on Earth just occur as an unlikely fluke, or are they of the nature that given time they are likely to happen?  Life isn't a miracle, unless you believe it is.  There isn't anything remarkable about life, unless you think it's remarkable.  All it seems to be is a certain combination of atoms.  Different combinations produce substances with different characteristics.  Life is just one characteristic of certain combinations, and there may be more combinations that are possible than the combination we know of.  It just hasn't happened on Earth.

Is that a loose enough thought to be in keeping with this thread?

Good question.  It would seem, post facto, that genes are a great idea in biology.  But this is in two stages ... with genes, nuclear and mitochondria ... one can conserve successful design.  The early Greek idea of random body parts combining with various reasonable success in the environment ... is an early version of evolution.  Turns out the real combinations occur at a level below eyesight, but which manifests in ways that can be seen in megafauna/flora.  But change is only thru mutation, and most mutations are deleterious.  The second great stage is sex ... the semi-random combination from two different individuals, exponentially expands what life can do, an innovation that happened early, before plants and animals became separate life forms.  Can you propose any other mechanism, that both conserves and innovates so well?
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Offline trdsf (OP)

Re: Loose Thoughts About Physical Reality
« Reply #5 on: June 06, 2017, 03:42:44 PM »
Evolution seems to revolve around DNA or some similar mechanism, so I'm wondering how likely it is that DNA or some similar mechanism is bound to occur.  Is it likely or not? If it isn't, evolution is not going to happen.  As for life itself, I have the same question.  It seems that atoms have a propensity to combine in many ways.  We know that the possible combinations are not infinite.  Certain atomic combinations appear to be impossible.  Did the combinations that lead to life on Earth just occur as an unlikely fluke, or are they of the nature that given time they are likely to happen?  Life isn't a miracle, unless you believe it is.  There isn't anything remarkable about life, unless you think it's remarkable.  All it seems to be is a certain combination of atoms.  Different combinations produce substances with different characteristics.  Life is just one characteristic of certain combinations, and there may be more combinations that are possible than the combination we know of.  It just hasn't happened on Earth.

Is that a loose enough thought to be in keeping with this thread?
Works for me.  That's the nice thing about loose thoughts, they point in all sorts of directions and you never know where you'll end up when you follow one.

I would love to see other kinds of data-bearing molecules, just to see what's possible.  Given the ease with which the basic amino acids form, I wouldn't be surprised to see DNA-like molecules in extra-terran life, but I would be surprised if the overall basic chemistry is the same.  Certainly the principle of mediocrity leads us to assume that there must be more efficient ways to store, replicate and evolve biological data than the way DNA does it.

Of course, a perfect replicator would be an evolutionary bottleneck, with changes limited to the genetic shuffle of sexual replication and the stray cosmic ray causing damage.

And I agree, there's nothing special about life insofar as the rest of the universe goes -- excluding non-reactive helium, we and the universe are made of the same things in the same order of abundance.  That tells me we're a product of the universe, not an insertion into it.
"It's hard to be religious when certain people are never incinerated by bolts of lightning." -- Calvin and Hobbes
"I thought I committed regicide today, but I committed deicide!" -- Sadie Doyle, Beyond Belief

Re: Loose Thoughts About Physical Reality
« Reply #6 on: June 06, 2017, 05:18:15 PM »
Well
I would love to see other kinds of data-bearing molecules, just to see what's possible. 

Well, there's XNA (Xeno Nucleic Acid), but that's artificial. Could be possible for a self-replicating molecule to form naturally, made of things other than A, G, C and T.
God Not Found
"And God promised men that good and obedient wives would be found in all corners of the world... then He made the earth round...and laughed and laughed and laughed...."
unknown

Offline Baruch

Re: Loose Thoughts About Physical Reality
« Reply #7 on: June 06, 2017, 07:48:44 PM »
Well
Well, there's XNA (Xeno Nucleic Acid), but that's artificial. Could be possible for a self-replicating molecule to form naturally, made of things other than A, G, C and T.

Did paper level experiments in college regarding xenobiology.  DNA is tricky, it is a series of 4 kings of pairs, but really are just two (A/T) and (C/G) in order to keep the helix in line ... (so it is a binary code if you don't care which way the pair is going, but a quaternary code when it is de-helixed.  You pretty much have to use carbon, not silicon, and the (zipper teeth) base pairs have to have the same size, to keep the helix in line..  There is DNA Origami ..

https://en.wikipedia.org/wiki/DNA_origami
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Offline trdsf (OP)

Re: Loose Thoughts About Physical Reality
« Reply #8 on: June 08, 2017, 11:40:41 AM »
Well, there's XNA (Xeno Nucleic Acid), but that's artificial. Could be possible for a self-replicating molecule to form naturally, made of things other than A, G, C and T.
Ooo, that's new information to me.  Neat!

One wonders what other data-bearing molecules there might be, ones that don't look like DNA/RNA/XNA, though.  Why only four types of base pairs, for example?

And the flip side, as usual, is that the molecules that make up the nucleic acids are very easy to form naturally, so we might be better served looking for other ways to combine them than for completely different structures.
"It's hard to be religious when certain people are never incinerated by bolts of lightning." -- Calvin and Hobbes
"I thought I committed regicide today, but I committed deicide!" -- Sadie Doyle, Beyond Belief

Offline trdsf (OP)

Re: Loose Thoughts About Physical Reality
« Reply #9 on: June 08, 2017, 01:59:55 PM »
Another loose thought.

The estimated spontaneous remission rate of cancer is about 1 in 100,000.

The Vatican has confirmed 69 "miracle cures" out of about 200,000,000 visitors to the shrine at Lourdes, among all maladies.

That calculates out to random chance being at least 29 times better at miracle cures than faith -- alas, I only have cancer's remission numbers, so I can't get more exact.
"It's hard to be religious when certain people are never incinerated by bolts of lightning." -- Calvin and Hobbes
"I thought I committed regicide today, but I committed deicide!" -- Sadie Doyle, Beyond Belief

Offline Baruch

Re: Loose Thoughts About Physical Reality
« Reply #10 on: June 08, 2017, 06:07:54 PM »
Another loose thought.

The estimated spontaneous remission rate of cancer is about 1 in 100,000.

The Vatican has confirmed 69 "miracle cures" out of about 200,000,000 visitors to the shrine at Lourdes, among all maladies.

That calculates out to random chance being at least 29 times better at miracle cures than faith -- alas, I only have cancer's remission numbers, so I can't get more exact.

Only matters if you are a cancer victim, and if cured, who you blame the cure on.
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Re: Loose Thoughts About Physical Reality
« Reply #11 on: June 09, 2017, 05:32:59 PM »
Well, it might just matter to the families and loved ones of cancer victims, as well.
God Not Found
"And God promised men that good and obedient wives would be found in all corners of the world... then He made the earth round...and laughed and laughed and laughed...."
unknown

Offline Baruch

Re: Loose Thoughts About Physical Reality
« Reply #12 on: June 09, 2017, 06:45:06 PM »
Well, it might just matter to the families and loved ones of cancer victims, as well.

As to causation ... two people, three opinions ;-)
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Offline trdsf (OP)

Re: Loose Thoughts About Physical Reality
« Reply #13 on: June 15, 2017, 12:36:41 PM »
Another loose thought.  Let's take 25 years as the average length of a generation.

If you go back 30 generations, around 1200-1250CE, on average you have more ancestors than there were physically alive at the time.

If you go back 38 generations, around 1000-1050CE, on average you have more ancestors than the total number of human beings that have ever existed.

Never let anyone tell you we are not all related.

I have a distant cousin who converted to Mormon back in the 70s or 80s and did a huge genealogical thing that happened to sweep my family up in it, so I have a family tree back to the 1400s in southwest England for that one line.  At the same time, I had about half a million other direct ancestors in the same generation that I have no idea who they were.  I find that sobering.  I would like to know who they were, and where they were.
"It's hard to be religious when certain people are never incinerated by bolts of lightning." -- Calvin and Hobbes
"I thought I committed regicide today, but I committed deicide!" -- Sadie Doyle, Beyond Belief

Offline Baruch

Re: Loose Thoughts About Physical Reality
« Reply #14 on: June 15, 2017, 12:51:19 PM »
Usually regular genealogy is only good back 10 generations or less ... because of adoptions and fostering (in Ireland).  Most people didn't have a family name before 1500, and some not before 1800 (Jewish folks).

DNA checks are on autosomal DNA (good back 300-500 years), Y chromosome (good back 5,000 - 10,000 years) and Mitochondrial DNA (good back 5,000 - 10,000) years.  That is because the autosomal DNA is shuffled every generation, the other two only change slowly by mutation.  So we can have a little knowledge about our Neolithic ancestry.  The other stuff, does show where in the world my ancestors were living, in general (basically NW Europe as of 300 years ago).  Back then I had 4,000 ancestors (some of which may be the same person, due to over counting).  Of course in longer time frames, there is inevitable over counting ... but presumably not much impact due to inbreeding.  Having any knowledge prior to 300 years ago, only happens if you have noble ancestry, of the kind of people who kept genealogical records.  Because I am part noble ... I have some family related history (but no direct connection) going back to Roman times.  Of course the closer you are related to recent noble ancestors, the more inbreeding you suffer from.
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