Episode: 4178
Title: HPR4178: Today I learnt (2024-07-27)
Source: https://hub.hackerpublicradio.org/ccdn.php?filename=/eps/hpr4178/hpr4178.mp3
Transcribed: 2025-10-25 20:52:47

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This is Hacker Public Radio Episode 4178 for Wednesday the 7th of August 2024.
Today's show is entitled, Today on Learn 2024-727.
It is part of the series today I Learned.
It is hosted by Dave Morris, and is about 8 minutes long.
It carries an explicit flag.
The summary is, a few more things I learned recently.
Hello, welcome to Hacker Public Radio.
My name is Dave Morris.
Today I'm going to do a show with the heading of or in the series of today I learned.
What I do for me is that as I come across interesting facts or things that seem worth putting
into such shows, I keep them, keep an eye on them.
So they're not actually today I learned items a few days ago, a few weeks ago, but bringing
them all together like this I hope is interesting.
The first item I've got is about the mass extinctions that have occurred on this planet.
They've been I think five of these over the history of the planet, and they're various
theories about what caused them and so forth.
These are theories that come and go because more information is discovered.
When I came across recently concerned the movement of the galaxy or movement of the solar
system within the galaxy.
So the galaxy is a big sort of disc, not an entirely flat one, but anyway, consider it
as a disc and the solar system orbits the disc towards the outside I believe, but I'm
not fully I'm not an astronomer so I don't understand this in a huge amount of detail.
But as it orbits then it's not in parallel or co-planar with the galaxy.
So there's points at which the solar system is a little bit above the middle of the galaxy
and a little bit below.
So when it's in the plane of the solar system then any gamma ray bursts that occur in the
galaxy tend to be shielded from the solar system.
But when it's above or below the plane then it's more vulnerable, we are more vulnerable.
The period of rotation is the galactic year which is about 255 million years long.
So the thinking seems to be that when the solar system is less protected the cosmic radiation
has effects on the life on Earth.
It does seem to be a correlation between the extinction events and the galactic year and
the exposure of the solar system.
But I don't get the message that this is a certainty, it's a theory, it's a hypothesis
even not even got as far as a theory and of course extinctions may have multiple causes.
If you look up my first link about extinction events in Wikipedia there's a lot of discussion
there about how extinction has occurred.
So it's an interesting area that can be investigated, that's what I think anyway.
There's no certainty about it again but this was new to me so I thought I'd share it.
And item is how you express the volume of liquid which is called milliliter, a thousandth
of a liter.
Do you write lowercase ml or lowercase m capital L?
No, I was watching a YouTube channel recently, the guy that's cooking in Canada, I've made
a pretty link to it and he finishes with the recipe usually either something he's created
or most often from various old recipe books, that's the show I particularly watch, things
from the 1920s and before, fascinating what people at, but often in the recipe contains
measurements like a 540 ml can of tomatoes with the ml is lowercase m capital L.
Now I did chemistry at school and university, somewhat relaxing the interior image, we
were taught that the abbreviated form of milliliter is ml in lowercase.
So I keep looking at this and thinking that can't be right.
So I went to research it and that the mixed case one is permitted and it's preferred in USA
Canada and Australia while we in Europe prefer the lowercase ml, didn't know that before.
If you look at the link I've provided, the various abbreviations for fractions and multiples
of liters all have a lowercase only and a mixed case version.
So desiliter is lowercase dl and d capital L desiliter, a hundredth of a liter I guess.
And I also discovered in the table there's a thing called a quetta liter which is ten
to the thirty liters.
So that's cool.
Not sure where and I will need to know that information, but fun.
The last one is a bit of sort of human anatomy and physiology and stuff which I do quite
enjoy finding out about having been a biologist.
This particular one is about a human gland called the mibumium gland.
There's multiple of these, it's a type, they're types of sebaceous glands and they're
in the eyelid.
Now sebaceous glands are the ones that you get at the base of hair follicles.
They produce an oily secretion that helps to keep the skin freer bacteria and just generally
more flexible, not dried out and so forth.
And the stuff that comes out of sebaceous glands is called sebum and it's from the Latin word
for talo, the stuff that used to be used to make candles, it's of animal fat stuff.
I did know about these, the mibumium glands are found on the edge of the eyelid just inside
of the eyelashes and the oily substance they produce helps prevent the eye surface from
drying out.
It sort of seals in the tear liquid that keeps the eye surface moist and it stops it from
drying.
And it also helps, I was interested to see, it helps the eyelids to make an airtight seal
when you close your eyes.
There are other functions, there are links obviously to, if you want to dig deeper, find
out more about it.
I didn't know about these things as a student, but the sort of biology that I did was really
animal biology and we looked at human anatomy to some extent, so we didn't, I'm not sure
whether it was that they didn't spend much time on it because they had too many other
things to do or whether less was known at that particular point.
The glands have been known about, since 1600, 1700, the German physician called Henrich
Mibum and that's obviously where the name has come from, from Germany and he was a physician
and scholar, it says in Wikipedia, there's a link if you want to look.
I didn't know that the secretions produced by these glands can reduce, as you get older
and the glands will also be blocked and there's various drugs and other things, hormone
levels that can affect them.
The result is, the thing called MGD, Mibomium gland dysfunction, so when I went to see my
optometrist, he said, you might have this, so you might need to get some treatment for
your eyes because my eyes are a bit sore and dry sometimes.
And of course, the name of the secretion of the Mibomium glands, riffing on the fact
that sebaceous glands produce sebum, the secretion from Mibomium gland is called Mibum.
Okay, that's the end, thanks very much, bye.
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