# Today I Learned

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Today I learned the first compass was probably made in China between 200 and 300BC. It was made of made of lodestone, a naturally magnetized ore of iron. https://en.wikipedia.org/wiki/History_of_the_compass

This is a picture of one of the first compasses.

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Today I learned that skills improved by participating here on scienceforums can, at least in some minor way, be helpful in the current virus situation. I joined a local initiative where students study

I found out you can be superstitious, but not a little bit stitious.

Today I learned that you only need 39 digits of π to calculate the circumference of the observable universe with a precision of one atom.

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On 11/16/2018 at 6:57 PM, Itoero said:

Today I learned the first compass was probably made in China between 200 and 300BC. It was made of made of lodestone, a naturally magnetized ore of iron. https://en.wikipedia.org/wiki/History_of_the_compass

This is a picture of one of the first compasses.

Edited by michel123456
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On 11/18/2018 at 4:00 PM, michel123456 said:

And also the way the ancients use to get proper orientation: you point a stick toward the sunrise at horizon in the morning, and in the evening you point a second stick towards the sunset. The bisector gives you the South. (and not the North).

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11 minutes ago, michel123456 said:

And also the way the ancients use to get proper orientation: you point a stick toward the sunrise at horizon in the morning, and in the evening you point a second stick towards the sunset. The bisector gives you the South. (and not the North).

Wait, why wouldn't it give you the North and South?

I'm envisioning two sticks facing 180 degrees away from each other. In my mind, the bisector could point north or south, depending on which side of the two sticks you placed it....

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23 minutes ago, Raider5678 said:

I'm envisioning two sticks facing 180 degrees away from each other.

They wouldn't (except at the equator on the summer solstice, perhaps). In the northern hemisphere, the sun normally rises and sets south of you. (But I guess you don't literally mean 180º)

But, of course, the line that bisects the angle would obviously also tell you where north was as well, just because it is opposite south!

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1 minute ago, Strange said:

They wouldn't (except at the equator on the summer solstice, perhaps). In the northern hemisphere, the sun normally rises and sets south of you. (But I guess you don't literally mean 180º)

Ah, yeah. Okay. I did mean 180 degrees, but I wasn't accounting for the fact that the Sun doesn't actually set exactly West and exactly East unless you're on the equator.

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23 hours ago, Strange said:

They wouldn't (except at the equator on the summer solstice, perhaps). In the northern hemisphere, the sun normally rises and sets south of you. (But I guess you don't literally mean 180º)

But, of course, the line that bisects the angle would obviously also tell you where north was as well, just because it is opposite south!

Exactly. When the Phoenicians mariners sent by Pharaoh Necho II (circa 600 BC) returned from their journey around Africa, they told that at some time the sun was at noon in the northern part of the sky. They were considered as liars at the epoch but now it is a very strong argument to believe them. They indeed traveled in the southern hemisphere.

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I think I’m in love.

Larva of a bluebottle fly (Calliphora vomitoria), under electron microscope:

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4 hours ago, koti said:

I think I’m in love.

Larva of a bluebottle fly (Calliphora vomitoria), under electron microscope:

I know what I'm going to be next Halloween!

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1 hour ago, Phi for All said:

I know what I'm going to be next Halloween!

A maggot!

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2 minutes ago, StringJunky said:

A maggot!

A little chamois and some wool and I think I could make a winter hat look just like that. I larva good ski cap!

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10 minutes ago, Phi for All said:

A little chamois and some wool and I think I could make a winter hat look just like that. I larva good ski cap!

I didn't know they had teeth. I've handled probably millions of them whilst fishing.

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1 hour ago, StringJunky said:

I didn't know they had teeth. I've handled probably millions of them whilst fishing.

Those are fangs Stringy and they are beautiful...just look at it again.

You heartless Mammal.

Edited by koti
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6 minutes ago, koti said:

Those are fangs Stringy and they are beautiful...just look at it again.

You heartless Mammal.

I can picture it hacking with those teeth on my dead body, like a pick axe going "Nom Nom..."

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55 minutes ago, StringJunky said:

I can picture it hacking with those teeth on my dead body, like a pick axe going "Nom Nom..."

I’m picturing a bad 80’s b type scifi horror movie with trademark grotesque special effects. This larva face reminds of those.

Edited by koti
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• 2 weeks later...

Today I learned scientists have uncovered the largest volcanic region on Earth – two kilometres below the surface of the vast ice sheet that covers West Antarctica.

Edited by Itoero
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Today I learned bacterial pathogens have coevolved with humans in order to efficiently infect, replicate within, and be transmitted to new hosts to ensure survival and a continual infection cycle. For enteric pathogens, the ability to adapt to numerous host factors under the harsh conditions of the gastrointestinal tract is critical for establishing infection. One such host factor readily encountered by enteric bacteria is bile, an innately antimicrobial detergent-like compound essential for digestion and nutrient absorption. Not only have enteric pathogens evolved to resist the bactericidal conditions of bile, but these bacteria also utilize bile as a signal to enhance virulence regulation for efficient infection.

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• 3 weeks later...

Today I learned that graphene can self repair:

Quote

Graphene can self-repair holes in its sheets when exposed to molecules containing carbon, such as hydrocarbons. Bombarded with pure carbon atoms, the atoms perfectly align into hexagons, completely filling the holes.[21][22]

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• 3 weeks later...
!

Moderator Note

Discussion about the geometry of graphene has been split here.

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• 2 weeks later...

Today I learned that (in newer cars, at least) there is a little arrow next to the fuel gauge to let you know which side the tank is:

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1 hour ago, Strange said:

Today﻿ I learned that (in newer cars, at least) there is a little arrow﻿ next to the fuel gauge to let you know which side the tank is:﻿﻿

Yep my brother in law told me a couple years ago. It is a useful feature.

My 2005 Chevy Colorado has one.

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You would think they would standardize on one side or the other.
If only to avoid the confusing messes at the gas pumps.

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A couple weeks ago I learned the giant trevally fish can eat/hunt birds.

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