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A scientific fact/tidbit you recently learned that you thought was interesting

Outside the tropics, not only does the moon look upside-down when you go to the hemisphere you aren't used to, but so do the constellations that are visible from both places. And the paths that the sun & moon & zodiac constellations take look like they're rising on the right and setting on the left in the southern hemisphere but rising on the left and setting on the right in the northern hemisphere.

The one fact that's behind all of those and explains them is that, when you look at the ecliptic zone (the band of the sky where the sun & moon & planets & zodiac constellations all are), you're looking south if you're in the northern hemisphere but looking north if you're in the southern hemisphere.

I learned the compass directions in my back yard, so my way to visualize this is by imagining still being back in that yard & watching things in the sky move over familiar things (an empty field & some woods to the east, Brian's back yard to the south, Greg's back yard to the north, our houses to the west & northwest & southwest). Facing south and watching ecliptic things move left to right feels normal & natural. Imagining ecliptic things moving right to left is bizarre. Imagining any of them appearing to the north is bizarre. Combining them gets less bizarre; having things appear in the north and move right to left fits together because it means they still rise over the empty field & woods and set behind the houses, just like when they were in the south and moving left to right.

In the tropics, the ecliptic band is straight overhead, so you don't look north or south at it and neither left-right nor right-left would seem to be the more natural direction to people who had always lived there.

As you move north & south between hemispheres, the ecliptic band, including the paths of the sun & moon & zodiac constellations, tilts south & north in the sky. At or near the Earth's poles, it's tilted all the way to horizontal, so everything just slides around near the horizon doing full circles all the way around you: right in the Arctic circle, left in the Antarctic circle.
 
A fever helps your immune system and hinders pathogenic invaders basically because your cells are bigger, and have more innate mechanisms by which they can withstand the higher temperatures.
 
Delvo said:
...
In the tropics, the ecliptic band is straight overhead, so you don't look north or south at it and neither left-right nor right-left would seem to be the more natural direction to people who had always lived there
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Interesting. It wasn't until I moved to Bellingham, WA and had a view over the bay off of my back porch that I became fascinated I could see the planets across the ecliptic. Before that I lived in Eugene, OR or parts south of that.

Delvo said:
...At or near the Earth's poles, it's tilted all the way to horizontal, so everything just slides around near the horizon doing full circles all the way around you: right in the Arctic circle, left in the Antarctic circle.
Click to expand...
If it is overhead on the equator, how is it horizontal at the poles? :boggled:

I can't quite picture that so I'm going to have to contemplate the Universe a bit more. Maybe I'm expecting it to be 'horizontal' when it already is by the time you get to to the Canadian border.
 
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arthwollipot said:
A fever helps your immune system and hinders pathogenic invaders basically because your cells are bigger, and have more innate mechanisms by which they can withstand the higher temperatures.
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Really? So cells are bigger as opposed to better vascular circulation?

How do bigger cells increase the number of innate mechanisms?

All the years I've worked with infectious disease and I can't tell you how many new things I'm learning about the immune system every day.
 
Skeptic Ginger said:
Really? So cells are bigger as opposed to better vascular circulation?

How do bigger cells increase the number of innate mechanisms?

All the years I've worked with infectious disease and I can't tell you how many new things I'm learning about the immune system every day.
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Well, that's what Philip Dettmer says in his book Immune: A Journey into the Mysterious System That Keeps You Alive (not a paid advertisement) :D

As a medical professional I think you'd find it a bit simplistic and lacking in detail, but it seems to be a good basic description of the whole complicated mess that is the human immune system. It's a hefty book. Here's the relevant paragraph, spoilered for length:

How exactly does the actual temperature increase stress out pathogens and make our cells better at fighting them? Well, it all has to do with the proteins inside cells and how they work. To put it in a simplified way: Certain chemical reactions between proteins have a sort of optimal zone, a temperature range in which they are the most efficient. By increasing the temperature in the body during fever, pathogens are forced to operate outside this optimal zone. Why does this not affect your cells but even helps them? Well, as we alluded to earlier, your animal cells are larger and more complex than for example bacteria cells. your cells have more sophisticated mechanisms that protect them from higher temperatures, such as heat shock proteins. Also, your cells have more redundancies, if one of their internal mechanisms is impaired, they probably have alternative mechanisms that can take over. This is also the reason fever is helpful to your immune cells, since they can handle the heat, they can make use of the effect that higher temperatures tend to speed up certain reactions between proteins. So the complexity of your cells, in contrast to many microorganisms, makes them not suffer from fever but instead work more efficiently. Of course there is also a limit on how hot we can get and for how long before our systems break down too.


This is followed by a footnote indicating that ectothermic animals artificially induce fever-like conditions by basking on hot rocks.
 
arthwollipot said:
Well, that's what Philip Dettmer says in his book Immune: A Journey into the Mysterious System That Keeps You Alive (not a paid advertisement) :D

As a medical professional I think you'd find it a bit simplistic and lacking in detail, but it seems to be a good basic description of the whole complicated mess that is the human immune system. It's a hefty book. Here's the relevant paragraph, spoilered for length:

How exactly does the actual temperature increase stress out pathogens and make our cells better at fighting them? Well, it all has to do with the proteins inside cells and how they work. To put it in a simplified way: Certain chemical reactions between proteins have a sort of optimal zone, a temperature range in which they are the most efficient. By increasing the temperature in the body during fever, pathogens are forced to operate outside this optimal zone. Why does this not affect your cells but even helps them? Well, as we alluded to earlier, your animal cells are larger and more complex than for example bacteria cells. your cells have more sophisticated mechanisms that protect them from higher temperatures, such as heat shock proteins. Also, your cells have more redundancies, if one of their internal mechanisms is impaired, they probably have alternative mechanisms that can take over. This is also the reason fever is helpful to your immune cells, since they can handle the heat, they can make use of the effect that higher temperatures tend to speed up certain reactions between proteins. So the complexity of your cells, in contrast to many microorganisms, makes them not suffer from fever but instead work more efficiently. Of course there is also a limit on how hot we can get and for how long before our systems break down too.


This is followed by a footnote indicating that ectothermic animals artificially induce fever-like conditions by basking on hot rocks.
Click to expand...
Temperature range for proteins and other cell functions makes more sense to me than cell size. I don't think it's cell size or complexity per se that allows us to tolerate a certain heat range over a bacterial pathogen, we've evolved to tolerate a certain heat range.

Thermophiles can tolerate much higher temperatures than we can so that contradicts the guy's hypotheses. OTOH it might just be the author adjusting his information to particular readers.

It is believed that a fever within a certain range serves a purpose fighting infection.
 
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Skeptic Ginger said:
Temperature range for proteins and other cell functions makes more sense to me than cell size. I don't think it's cell size or complexity per se that allows us to tolerate a certain heat range over a bacterial pathogen, we've evolved to tolerate a certain heat range.
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The idea is that larger cells allow for more sophisticated intracellular mechanisms that provide heat tolerance. Not much room for that sort of thing in a bacterium.

Skeptic Ginger said:
Thermophiles can tolerate much higher temperatures than we can so that contradicts the guy's hypotheses. OTOH it might just be the author adjusting his information to particular readers.
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It's definitely that - the book is written for an interested non-expert audience so as I said a lot of detail is omitted. He often points out when he is omitting detail. But the book also isn't about making hypotheses. It's describing the current level of knowledge. And Kurzgesagt is especially concerned with fact-checking. Some early videos were removed and corrected when it was established that their fact-checking wasn't sufficient. They're not perfect, but they're a pretty reliable source for information.

 
arthwollipot said:
The idea is that larger cells allow for more sophisticated intracellular mechanisms that provide heat tolerance. Not much room for that sort of thing in a bacterium.
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Thermophiles contradict that size hypothesis.


arthwollipot said:
But the book also isn't about making hypotheses. It's describing the current level of knowledge.
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Those are hypotheses. It doesn't matter what state of scientific support they have.


arthwollipot said:
And Kurzgesagt is especially concerned with fact-checking. Some early videos were removed and corrected when it was established that their fact-checking wasn't sufficient. They're not perfect, but they're a pretty reliable source for information.
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You know how facts work in science, right? That he changed his text, updated his POV means his facts are only whatever was valid at the time. And that's how science works.

Re the video, I don't agree at all that oversimplification equates to lying. :rolleyes:

Half of that video is an ad for their videos. I am not impressed as we say in medicine. They wouldn't need an explainer video ad if they were providing correct up to date information.
 
And hey, the book has given me some context so that I know what this article about monoclonal antibodies is going on about.

tl;dr: the human immune system is complicated and amazing. Any description of it is going to simplify some concepts. But the most amazing thing is that the basic concepts can be understood by someone who doesn't have a five-year medical degree with a postgraduate specialisation in immunology. And that's a tidbit that I found interesting.
 
arthwollipot said:
So issuing corrections is bad now?
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:rolleyes: That's what you think I said?

SG said:
That he changed his text, updated his POV means his facts are only whatever was valid at the time. And that's how science works.
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One of those quotes is not like the other.


I get it you find this source impressive and valid. That's fine. I've not said your source isn't valid.

What I said was the existence of thermophiles contradicts the hypothesis that cell size was the variable which fever allowed human cells to survive a fever while microorganisms did not.

And you have the problem of viral pathogens which live within infected cells. How does cell size apply to them?
 
Dr. Keith said:
I recently was reminded of a pneumonic for knowing whether a moon is waxing or waning: DOC. If the partial moon looks like a D it is heading towards full, O, and if it looks like a C it is past full. So, D is waxing and C is waning. Now I’m wondering if that helpful bit of 7th grade science holds true south of the equator. Hmm.
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For the Southern hemisphere, just memorize "COD" for the same effect.
Of course, you now must not get confused whether it's DOC or COD for your current hemisphere! :D

A traditional "pneumonic" for Germans has been for a long time that the waning ("abnehmender"; literally: "losing weight") moon is represented by the German cursive letter A, while the waxing ("zunehmender" = "putting on weight") moon is represented by the letter "Z".
Which only makes sense if you have learned the old (pre-1940s) German cursive script.

This inspired a wonderful little poem by Christian Morgenstern:

Als Gott den lieben Mond erschuf,
gab er ihm folgenden Beruf:

Beim Zu- sowohl wie beim Abnehmen
sich deutschen Lesern zu bequemen,

ein a formierend und ein z –
daß keiner groß zu denken hätt’.

Befolgend dies ward der Trabant
ein völlig deutscher Gegenstand.​

My translation:
When God created the dear moon
he gave him the following profession:

On waxing as on waning
to accomodate to German readers,

to form an a and a z -
so no one would have to think hard

Obeying this, the satellite became
a completely German item.​
:o
 
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Emily's Cat said:
:o Yes, I said it 100% backwards.

Why would hemisphere matter? The sun still rises in the east when you're in Australia, and sets in the west. The moon-sun-earth relationship doesn't get upended by hemisphere does it?
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No, but you do.

Imagine standing on the North Pole. Your head is pointing towards Polaris. Now imagine yourself standing on the South Pole. Your feet are pointing to Polaris.
 
Concerning waxing or waning moons, I tend to regard the Moon as waxing if I see it closer to sunset, and waning if I see it closer to sunrise.

Of course, this is no use when it is close to full moon. In that case, the Moon is gibbous, and the similarity to letters is useless anyway …
 
steenkh said:
Concerning waxing or waning moons, I tend to regard the Moon as waxing if I see it closer to sunset, and waning if I see it closer to sunrise.

Of course, this is no use when it is close to full moon. In that case, the Moon is gibbous, and the similarity to letters is useless anyway …
Click to expand...

The easiest way to tell is to just wait a few days. If the Moon is more full, then it was waxing, if it is closer to a new Moon then it was waning. This method works no matter which hemisphere you are in.
 
jeremyp said:
The easiest way to tell is to just wait a few days. If the Moon is more full, then it was waxing, if it is closer to a new Moon then it was waning. This method works no matter which hemisphere you are in.
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That's... not easier.

If the moon is already up when the sun sets, it's waxing. If the moon is still up when the sun rises, it's waning. You don't have to wait days to figure it out.
 
Emily's Cat said:
:( I need a visual diagram. I can't fit this into my brain, I don't understand why it would look different. I'm sure it makes perfect sense, it's just not processing for me.
Click to expand...

Click the link in this post from Skeptic Ginger, it's got a pretty good explanation along with diagrams and pictures:
Skeptic Ginger said:
More fun: Can the Moon be upside down?

Also, since rarely does one of the waxing or waning phases look perpendicular, the appearance looks upside down rather than a mirror image. I didn't know it happened until I traveled south and my reaction was, it's upside down!
Click to expand...
 
Here's another visual aide. I had a hard time imagining the view from the poles so I looked for more sources.

 
I think I remember the rule was: if you can add a stem and turn the moon in the letter 'p', it's in the 'premier" or first quarter. If you can add the stem on the other side, and turn it into the letter 'd', it's in the 'dernier' or last quarter. Waxing and waning follows from that.
 
Emily's Cat said:
:( I need a visual diagram. I can't fit this into my brain, I don't understand why it would look different. I'm sure it makes perfect sense, it's just not processing for me.
Click to expand...


Not a visual diagram, but try this. Look at the moon when it's high in the sky. That's you looking at the moon from your hemisphere. Now turn and face away from the moon, and tilt your head back and arch your back until you can see the moon again. Now it's upside down! That's someone looking at the moon at the same time from the same latitude (more or less) on the other hemisphere.

Except, they don't have to bend backward to see it that way because where they're standing, with their heads pointing the exact same direction as yours, the angle of the ground is such that they're standing and looking up normally.
 
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Ron Obvious said:
I think I remember the rule was: if you can add a stem and turn the moon in the letter 'p', it's in the 'premier" or first quarter. If you can add the stem on the other side, and turn it into the letter 'd', it's in the 'dernier' or last quarter. Waxing and waning follows from that.
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I thought the "d" word would be "done", but apparently I was using the wrong language.

Or, if adding a stem gives you "b", it's beginning, and if it gives you "q", it's quitting.
 
Emily's Cat said:
Delvo said:
Plums & cherries & apricots & nectarines are not only members of that family but even members of the same genus as almonds & peaches.
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I get all the fruity-fruits, they're all stone fruits. I can kind of see almonds... but why not other nuts as well? What makes almonds different?
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Different from other nuts? They just aren't related because there's no reason why they would need to be. A "nut" is just our word for a thing a plant produces which is good food for one kind of animal or another but harder & drier than other foods from plants, like fruits & veggies. Any plant lineage can evolve to produce relatively hard & dry food for animals, and, whenever & wherever they do, that gets called a "nut", regardless of which lineage of plant happens to have evolved it. (Peanuts, BTW, are named pretty literally; they're what you get when nuts evolve in a member of the pea subfamily.)
 
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Ron Obvious said:
I tend to avoid memorising with mnemonics for reasons similar to this.
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But at least in this case at least they all give the same result, no contradictions, unlike that stupid worthless "left hand shaped like a letter L" rule for remembering which is left.
 
Just now I learned that (probably) all golden hamsters in captivity today (as pets or as lab animals) are descended from a single female captured near Aleppo, Syria, in 1930 along with her litter of pups, of which only 3 males and 1 female survived.

So all those millions upon millions of golden hamsters - all the result of hardcore inbreeding!

(Since 1971, specimen newly captured in the wild have occasionally added to breeding pools here and there, but apparently, a 2001 study showed that all golden hamsters in captivity that they studied shared the same mitochondrial DNA - likely that of the females captured in 1930. Or the wild population in Syria has undergone some serious population bottleneck such that even the wild populations are mostly descended from one female.)

https://en.wikipedia.org/wiki/Golden_hamster#Discovery
 
Thermal said:
Only sort of a scientific fact, but I just found out why Pringles all have the same shape: they are made from the same kind of powder used to make instant mashed potatoes and molded. For the same reason, they cannot legally be called "chips".
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Similarly American cheese individually wrapped slices are not cheese. They are cheese product, something made from cheese, like 50% cheese. Also, they are not slices, but "singles", because they aren't sliced so much as poured into the wrappers which stomps them separate.

You can buy actual American cheese, as with any other cheese, but it is 2x as expensive.

This journey was kicked off wondering why the hell unwrapped American cheese slices were so much more expensive than wrapped, which should bump up the price, not decrease it.
 
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Delvo said:
But at least in this case at least they all give the same result, no contradictions, unlike that stupid worthless "left hand shaped like a letter L" rule for remembering which is left.
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In what way is that worthless? I've found it useful with 2nd-graders many times. How would one get a different result, or contradictions, unless you're missing some fingers or a thumb?
 
alfaniner said:
In what way is that worthless? I've found it useful with 2nd-graders many times. How would one get a different result, or contradictions, unless you're missing some fingers or a thumb?
Click to expand...

Getting the knuckleheads to remember that it relies on palms facing down
 
Emily's Cat said:
:( I need a visual diagram. I can't fit this into my brain, I don't understand why it would look different. I'm sure it makes perfect sense, it's just not processing for me.
Click to expand...

Imagine you're at the north pole at spring equinox, facing the sun (which is at the horizon), with the moon off to your left at half moon. You start moving south (really fast, so the earth/sun/moon don't move), and as you do so, the sun starts to rise in the sky. The moon remains off to your left, at half moon, but the half which is illuminated rotates as the run rises. That half always faces the sun. When you hit the equator, the sun is directly overhead, and it's the top half of the moon which is illuminated. Keep going until you reach the south pole, the sun is at the horizon directly behind you, the sun is still off to your left, and now it's the left side of the moon which is illuminated. You can turn around and face the sun, so that the moon is now on your right side, but it's still the left side of the moon which is illuminated, because the sun is now to the left of the moon.

When you're at the south pole, you're upside down relative to your orientation at the north pole.
 
Oystein said:
Just now I learned that (probably) all golden hamsters in captivity today (as pets or as lab animals) are descended from a single female captured near Aleppo, Syria, in 1930 along with her litter of pups, of which only 3 males and 1 female survived.

So all those millions upon millions of golden hamsters - all the result of hardcore inbreeding!

(Since 1971, specimen newly captured in the wild have occasionally added to breeding pools here and there, but apparently, a 2001 study showed that all golden hamsters in captivity that they studied shared the same mitochondrial DNA - likely that of the females captured in 1930. Or the wild population in Syria has undergone some serious population bottleneck such that even the wild populations are mostly descended from one female.)

https://en.wikipedia.org/wiki/Golden_hamster#Discovery
Click to expand...
:eek: Wow!
 
More fun: Can the Moon be upside down?

Also, since rarely does one of the waxing or waning phases look perpendicular, the appearance looks upside down rather than a mirror image. I didn't know it happened until I traveled south and my reaction was, it's upside down!
Click to expand...

It used to bother me with the crescents reversed when I moved down under but now don't noticed it. Orion I do notice being inverted.
 
Speaking of the moon, we always see the same side, even though the moon rotates.
 
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