TIL - Today I Learned .. share something you learned for the first time

[Horus Salubrius]

Out walking the dogs this Christmas morning & I came across this coming from many dead branches & bits of wood throughout the forest.  At first I thought it was a fungi, turns out it is called Hair Ice - kind of rare, requires very certain temperatures & humidity to occur, only extrudes from wood (ie. not through bark)  & only occurs between 45 & 55 degrees north.  Wasn't until 2015 that scientists discovered the fungi inside the wood that imparts an antifreeze quality to the water, preventing the water from forming larger ice crystals, leading to this hair like appearance.   Bizarre & fascinating - I have never seen this before !  

Edited December 25, 2020 by Horus Salubrius

[Rolig Loon]

 

[Odaks]

What does it feel like to invent math?

That was a bit of a conversation stopper!

[Maryanne Solo]

Recent security camera installations, (Ultra HD, 4k, 8mp, 3840 x 2160), revealed a cheeky little fox cruising the property late at night.
It takes exactly the same route every evening of course.
Over time this semi rural area has become suburbia 😒 but there's a massive nature reserve, a creek and sports grounds directly across the road.
Foxes aren't native to this country so its very surprising to see one right here.
We did have pet foxes, (sort of/they're wild), when I worked at the 416 hectare/1027acres, (1.61mi2 - 4.16km2 - 41.6 castles LOL), local native garden/park,
but that's about 10kms away.
I'll try get a piccy of it next time I see it on screen, It's really cute. 🥰
 

Edited January 2, 2021 by Maryanne Solo
Added windoze calculator conversions.

[Zzevir]

That I'm a totall failure. I new this before but I have new evidence. 

[Rolig Loon]

Surely nobody can be a total failure or a perfect fool. We're all too flawed for that. You must have accidentally done at least a few things right.  Smile.  Maybe it will happen again. 😎

[Arkam]

42 minutes ago, Zzevir said:

That I'm a totall failure. I new this before but I have new evidence. 

You are not a total faliure, at least you serve as bad example.

((  Sorry, I could not shut up the bad joke  😁 ))

[Marigold Devin]

I honestly only just found out that flames have no shadows.

(But I still don't know what the three seashells are for in Demolition Man)

[Echelon Alcott]

TIL avatar physics. I had never heard of it before today. Yeah, I've been away from SL for quite a while, but getting back in the game! 

[BjorJlen]

3 hours ago, Marigold Devin said:

I honestly only just found out that flames have no shadows.

(But I still don't know what the three seashells are for in Demolition Man)

   Oooo, thank you for that interesting tidbit about fire. I'll have to try it out and look see. 😁

   As far as the 3 seashell's goes though, both Stallone and Bullock both explained what they were for, though they of course have different views. Check these out...

   Stallone's explanation...
   Bullock's explanation...

Peace...

[Madelaine McMasters]

4 hours ago, Marigold Devin said:

I honestly only just found out that flames have no shadows.

(But I still don't know what the three seashells are for in Demolition Man)

Don't let that idea to into your long-term memory, it's not true. I can and have cast shadows from flames. Light a candle outside on a sunny day and look at the shadow, you'll see the faint outline of the flickering flame. If it's sunny enough, the shadow of the flame might be as visible as the flame itself. If you light a propane torch outside on a sunny day, it's easier to adjust flame length by looking at the shadow than the flame.

 

Edited October 19, 2021 by Madelaine McMasters

[Marigold Devin]

6 minutes ago, Madelaine McMasters said:

Don't let that idea to into your long-term memory, it's not true. I can and have cast shadows from flames. Light a candle outside on a sunny day and look at the shadow, you'll see the faint outline of the flickering flame. If it's sunny enough, the shadow of the flame might be as visible as the flame itself. If you light a propane torch outside on a sunny day, it's easier to adjust flame length by looking at the shadow than the flame.

 

My head hurts already  but that shadow is from the thermal/heat rather than the flame itself, and is much bigger as a result. 

[Madelaine McMasters]

8 minutes ago, Marigold Devin said:

My head hurts already  but that shadow is from the thermal/heat rather than the flame itself, and is much bigger as a result. 

Most of the candle flame shadow we see in sun/incandescent light is from refraction of light by the heated gases. Water (think of the bottom of an outdoor pool on a sunny day) casts shadows via both refraction and reflection. It doesn't make any difference whether light is prevented from passing from a source to a destination by absorption, reflection, or refraction, the result is a shadow.

https://www.wtamu.edu/~cbaird/sq/2014/02/12/can-air-make-shadows/

Here's a nifty demonstration of burning sodium in the light of a sodium vapor lamp, making the flame's absorption spectrum the dominant mechanism for casting the shadow...

 

[Rolig Loon]

41 minutes ago, Marigold Devin said:

My head hurts already  but that shadow is from the thermal/heat rather than the flame itself, and is much bigger as a result. 

Hmmm.. You can't see heat.  You can see some of the effects that heat has on things, like the changes in refraction as light passes through hot gases.  That's what you see in the wavy air over hot pavement or over a flame.  And it's also what you see in the incandescence and wavy air in a flame itself.  Now, can you see a shadow from hot air or incandescent gas? Sort of.  Light shining through a flame or the air over hot asphalt is bent and dispersed, so when it strikes a surface it casts something that looks like a shadow.  It's not because the light is being blocked, but because it's refracted in irregular directions.

EDIT:  Oooh... Maddy got here first. ^^  What she said.....

Edited October 19, 2021 by Rolig Loon

[Madelaine McMasters]

59 minutes ago, Rolig Loon said:

Hmmm.. You can't see heat.

Unless  you have a parabolic mirror and some time on your hands...

Before placing the mirror we made into its telescope home nearly 40 years ago, Dad and I did some Schlieren imaging with it.

ETA: Well, that's not really seeing heat, it's seeing refraction caused by heat. You can see heat with one of these...

https://www.amazon.com/s?k=flir+camera

The static you hear between radio stations is heat. Two Bell Labs engineers won a Nobel for figuring this out...
https://en.wikipedia.org/wiki/Discovery_of_cosmic_microwave_background_radiation

If you turn the volume control on a record player all the way up with no record playing, the hiss you hear is heat jostling electrons in the amplifier circuits...
https://en.wikipedia.org/wiki/Johnson–Nyquist_noise

Edited October 19, 2021 by Madelaine McMasters

[bigmoe Whitfield]

that the stray cat at work that likes nobody, will come to you if you know the right sounds,  he is the most dicile cat and loving,  but he still dont like the others, took him a bit, but I can typically walk out one of the loading doors and click and psst and here he comes running with a happy meow.

[Phil Deakins]

(Yester)TIL that my Amazon Fire TV Stick can be used to operate smart bulbs and stuff like that with voice. Today I'm receiving 3 smart bulbs. I'll collect them from the drop-off point when I've finished this cup of tea 🙂

[Prokofy Neva]

https://www.quantamagazine.org/first-time-crystal-built-using-googles-quantum-computer-20210730/

[Arielle Popstar]

12 hours ago, Madelaine McMasters said:

Don't let that idea to into your long-term memory, it's not true. I can and have cast shadows from flames. Light a candle outside on a sunny day and look at the shadow, you'll see the faint outline of the flickering flame. If it's sunny enough, the shadow of the flame might be as visible as the flame itself. If you light a propane torch outside on a sunny day, it's easier to adjust flame length by looking at the shadow than the flame.

Is that actually a shadow or a difference in the brightness of light falling on a surface? After all, when the sunlight starts turning to evening and night, the flame will be the brighter source of light falling on the same surface. No change to flame or surface and yet it would no longer be seen as shadow, so by definition I would say it is not casting a shadow but a differing degree of brightness in comparison.

[Orwar]

   Didn't learn this today, but the other day: candle flames are hollow. Sort of.

[Kathlen Onyx]

TIL that people really do use the SL voice morphers and they actually are very good at deceiving people.

[Lindal Kidd]

12 hours ago, Madelaine McMasters said:

Before placing the mirror we made into its telescope home nearly 40 years ago, Dad and I did some Schlieren imaging with it.

ETA: Well, that's not really seeing heat, it's seeing refraction caused by heat. You can see heat with one of these...

https://www.amazon.com/s?k=flir+camera

The static you hear between radio stations is heat. Two Bell Labs engineers won a Nobel for figuring this out...
https://en.wikipedia.org/wiki/Discovery_of_cosmic_microwave_background_radiation

If you turn the volume control on a record player all the way up with no record playing, the hiss you hear is heat jostling electrons in the amplifier circuits...
https://en.wikipedia.org/wiki/Johnson–Nyquist_noise

Maddy, you should be teaching high school physics. You have a way of looking at things, and making others see things, that would enthrall your students and lead a lot of them on to careers in science and engineering.

[Madelaine McMasters]

3 hours ago, Arielle Popstar said:

Is that actually a shadow or a difference in the brightness of light falling on a surface? After all, when the sunlight starts turning to evening and night, the flame will be the brighter source of light falling on the same surface. No change to flame or surface and yet it would no longer be seen as shadow, so by definition I would say it is not casting a shadow but a differing degree of brightness in comparison.

A shadow is a difference in the brightness of light falling on a surface, caused by something between the surface and the light source. To science, it doesn't matter whether that something absorbs, refracts, diffracts, scatters, or reflects the light, and it doesn't matter whether that difference in brightness is detectable by the human eye. Most of us are only familiar with what we can sense directly under nominal conditions. Everything you said is correct, and fully consistent with the definition of "shadow". If I shine a bright enough light on shadow of an object, it will seem to vanish. That doesn't mean the object stopped casting a shadow.

The fact that you can look into a beautiful golden sunset without harming your eyes is due to the shadow Earth's atmosphere casts on you. Most of our atmosphere is O2 and N2, which scatter shorter (UV, violet, blue) wavelengths via Rayleigh scattering. At noon, the Sun's light passes down through the least amount of atmosphere, encounters the least scattering, and is therefore truest to its actual color. As the Sun sets, its light must travel through ever more atmosphere to reach our eyes, losing more and more shorter wavelengths (and intensity overall) to scattering. This is why the sky is blue and the Sun becomes dimmer and redder as it sets. Smoke particles are much larger than O2 and N2, and scatter even longer wavelengths (green, yellow), leaving us with those awesome and foreboding deep red sunsets.

Here's an image of a shuttle launch shortly after sunset that demonstrates all of this, and more...

At ground level, the smoke trail is dimly lit because it's in Earth's shadow. You can see that same shadow in the dark sky just above the horizon. Had the launch occurred just east of the Rocky Mountains or mid-town Manhattan you'd see a shadow of the sunset skyline on the eastern horizon. You've probably seen the shadows of clouds opposite the sun at dawn/dusk. If you turned to face the sunset, you might see the "crepuscular rays" which are the projection of those shadows through the atmosphere. This launch occurred during a full moon, when the moon is directly opposite the sun. The shadow of the smoke trail (an anticrepuscular ray) can be seen terminating at the moon. You don't see that shadow emanating from the bottom of the plume because that part is already in the earth's shadow. You don't see the shadow emanating from the top of the plume both because there is less atmosphere to scatter light up there, and because the trajectory has changed to be across our angle of view, spreading what little shadow there is across a wider swath of the image.

As you climb up the smoke trail, you see the emergence of red, orange and then yellow. The sun hasn't yet set at those altitudes, and the trail is being directly illuminated through decreasing amounts of atmosphere. The higher you go, the less blue is scattered out. Ultimately, the top of the plume appears as bright and white as the midday sun. If you look out to the horizon, you see the same progression from shadow to red, orange and yellow. Yet, unlike the smoke trail, the sky does not get brighter as elevation increases. That's because the warmer hues near the horizon are the cumulative scatterings of many miles of atmosphere. As you climb higher in the sky, there is less atmosphere to scatter light of any color and the sky grows darker. That the sky overhead remains blue into darkness is due to absorption of longer wavelengths by atmospheric ozone at high altitude.

My father exposed me to the limitations of our senses, and never passed up an opportunity to carry us beyond them. Rather than follow his path into mechanical engineering, I went into electrical, almost entirely because the electromagnetic spectrum is so much more than we can sense and electricity is so much faster than machines. I wanted to use and make tools to expand my reach. I'm now in my sixth decade of that glorious road trip.

Edited October 19, 2021 by Madelaine McMasters

[Madelaine McMasters]

2 hours ago, Lindal Kidd said:

Maddy, you should be teaching high school physics. You have a way of looking at things, and making others see things, that would enthrall your students and lead a lot of them on to careers in science and engineering.

Thank you, Lindal. That's very kind.

I actually tried teaching circuit design for two semesters. I got frustrated by the lack of curiosity and motivation of the students. I also got some scathing student appraisals, stating I was "too tough". I got called into the department chair's office to discuss that, and the fact that the average grade I'd given was "C". I noted that the student handbook stated "C" indicated average performance.

He: We like to think that our students are above average.
Me: This is Milwaukee, not Lake Wobegon.

To this day, I'm surprised I was invited back for a second semester. I did not return for the requested third.

The high point of my career might have been the last day of it. I'd announced my retirement to my last consulting client, who decided to throw a little lunch party to celebrate my departure. One of the engineers I'd been working thanked me for reminding him just how joyful engineering could be. That brought a little round of applause from the rest.

I don't often shed tears, but I did then.

 

Edited October 19, 2021 by Madelaine McMasters

[Silent Mistwalker]

16 hours ago, BjorJlen said:

   Oooo, thank you for that interesting tidbit about fire. I'll have to try it out and look see. 😁

   As far as the 3 seashell's goes though, both Stallone and Bullock both explained what they were for, though they of course have different views. Check these out...

   Stallone's explanation...
   Bullock's explanation...

Peace...

 

https://blog.whogivesacrap.org/home/goodfun/before-toilet-paper