"Did You Know......"

[slaughtr]

Originally Posted by Ian

This thing about the small intestine reaching the moon is a longstanding rumor. All I can figure is that they are referring to the digestive surface of the small intestine (all those microvilli.........)

That's my guess. In that case, it may well be, but not just from "uncoiling". Otherwise, it would take me forever to do an autopsy!

[Cthulhu]

Originally Posted by Lancia

I think the myth comes from bare coils in old frigidaires.
They used to defrost them by putting hot water in the metal trays.
The heat defrosted the insulating frost on the coils and the now bare coils would cool very rapidly again.


Only cold water can freeze.
Hot water must be converted to cold before freezing.
It is a linear and predictable medium.

I wish temperature change was linear and predictable in liquids. That would make heatflow modeling much nicer. Advection and the fact that heat flows faster along larger gradients screw things up. It's possible for hot water to freeze faster than cold water, it's called the Mpemba effect.

Mpemba effect - Wikipedia, the free encyclopedia

[Ian]

Originally Posted by Cthulhu

I wish temperature change was linear and predictable in liquids. That would make heatflow modeling much nicer. Advection and the fact that heat flows faster along larger gradients screw things up. It's possible for hot water to freeze faster than cold water, it's called the Mpemba effect.

Mpemba effect - Wikipedia, the free encyclopedia

A common mis-explanation of the effect is that hot water cools quicker than cold water. For the hot water to freeze first the temperature of the (initially) hot water would reach zero first. The two temperatures would cross at some point so that the hot water can win the "race" to zero degrees and start freezing. At that crossing point, assuming a simple model that ignores effects such as convection and uneven cooling, the rates of cooling would be the same. In fact, the hot water will always be playing catch-up with the cold water. Once at zero, there will be a certain time delay before freezing is complete because of the latent heat of freezing, and this time delay is independent of the initial temperature of the water as both the hot and cold water will be at zero.

The effect is thus more complex than a simple uniform-body cooling model.


From Wikipedia:

[Lancia]

Ice cream is not water.
That will have to be proved to me.

Hot water doesn't take three times as long to cool because the bigger differential causes faster cooling until the temperatures become closer together.
Just like putting air in a tire.
I've done the experiment.
It's closer than you would expect.
But you can't get around the laws of physics.

You know they still use water to measure heat?

Too bad.
I do have issues with the mass/ conservation of energy stuff.
Damn rules!

[mgreenbl]

Originally Posted by Ian

This is fact; confirmed with my wife who is a gastroenterologist.

This thing about the small intestine reaching the moon is a longstanding rumor. All I can figure is that they are referring to the digestive surface of the small intestine (all those microvilli.........)

I think he meant to say the total length of veins, arteries, and capillaries. It is apparently 60,000 miles according to:

Blood Vessels - Miles of Plumbing - MedicineNet - Health and Medical Information Produced by Doctors

converted to feet, it would be 316,800,000, or almost 1/4 of what the original poster listed.

Mark

[mgreenbl]

Originally Posted by Cardinal

Did you know, if you have a group of 23 people, the odds are in favor (50.6%) of there being a birthday match between two of the people?

in a group of 40 people, odds are 90%


Mark

[glb]

Originally Posted by Cardinal

Did you know, if you have a group of 23 people, the odds are in favor (50.6%) of there being a birthday match between two of the people?

have heard this many times, still don't believe or understand it, based on there being 365 days in a year. Seems as if we'd need 183 people to have odds > 50%.

[luxige]

Originally Posted by glb

have heard this many times, still don't believe or understand it, based on there being 365 days in a year. Seems as if we'd need 183 people to have odds > 50%.

It's a little non-intuitive and surprisingly hard to calculate (for me, anyway).

Your calculation is correct for a match of a specified birthday. Say you are in a room alone, and people enter one at a time. How many need to enter for one of them to have the same birthday as you? If 365 come in, at least one has to have the same day as you. (Half that number, 183, would give the 50/50 odds you calculated).

That's to match just you. Now try it again, but with you and a friend in the room to start. Obviously the odds have increased (for either of you to get a match). Add another person, and the odds are better still, etc.

In the room of 23 people, person #1 could match with any of the other 22. #2 could match with 21 people (#3 through #23; we already counted the possibility of matching #1). And so on. So there are 22 + 21 + 20 + ... +1 = (23 x 22)/2 = 253 possible pairs. Suddenly the odds look good. To get the exact odds of a match, you have to calculate the probability that every birthday is different, and subtract that from 100%. That's where I get lost.

[Cthulhu]

Did you know that the earth is still hot, not because of latent heat, but because of decaying Uranium?

If it wasn't for radio-decay of Uranium within the mantle, the Steffan-Boltzman equation (black body emission) demonstrates that the earth would be cold by now.

[Implosion]

Originally Posted by luxige

Your calculation is correct for a match of a specified birthday. Say you are in a room alone, and people enter one at a time. How many need to enter for one of them to have the same birthday as you? If 365 come in, at least one has to have the same day as you. (Half that number would give the 50/50 odds you calculated).

Not quite. Assuming a functionally infinite sample population (what 5 billion these days?), the probability should be calculated with replacement. You could have 365 people including yourself in a room, but *other* folks could share a birthday with eachother, and therefore not with you.

Work that backwards, and allow for checks to see if any additions also have coincident birthdays and your required sample size to reach 50% probability starts to go down rapidly.

I'll run this by the research statisticians at work...this question should keep them closeted in rooms with whiteboards for at least a little while.

[Lancia]

I am told that in 18 generations, you are a blood relative to every other person on earth.
Within six generations, there is supposed to be a good chance of being related to anyone in this country.

Run that by them!

[Implosion]

Naw, sounds too much like a Kevin Bacon question. They just roll their eyes when those come up...

[Lancia]

You're related to Kevin Bacon?


It's just genetics and math.

[thetoast]

Originally Posted by Cardinal

Did you know Winnipeg is the coldest city in the world with a population over 600,000?

I believe that... I spent the first 26 years of my life there

Try frequently waiting at a bus stop during -40C/F weather (before windchill...). But it does also get unusually hot... often in the mid-thirties Celsius during summer

[apk919]

Originally Posted by glb

have heard this many times, still don't believe or understand it, based on there being 365 days in a year. Seems as if we'd need 183 people to have odds > 50%.

The easiest calculation is to take the odds of 23 people having <b>unique</b> birthdays, and subtract from 1 (i.e. the odds of at least two of the people having a non-unique birthday).

You make the calculation by adding people to the room one at a time. So, the first person is "free" (since there's no one else in the room, their birthday can't match anyone elses). For the second person, the odds that they have a unique birthday is 364/365. For the third, 363/365 (since by definition the first two have unique birthdays). Fourth: 362/365, etc.

So the full calculation is: ((364/365) * (363/365) * (362/365) * ... * (343/365)) = 0.492703, which is < 0.5

That means the the odds of 23 people in a room having unique birthdays is < 50%... so the complement is that the odds of at least 2 people out of 23 in a room having the same birthday is (1 - x) where x is < 0.5... in other words, > 0.5 (50%)

Get it?

[luxige]

Originally Posted by Implosion

You could have 365 people including yourself in a room, but *other* folks could share a birthday with eachother, and therefore not with you.

Oh. Yeah.

I think my knuckles are starting to drag the ground.
At least I got the last part right...

(I think)

[chapster5]

My god people! enough with the math quations and on with the useless facts


A whale's penis is called a dork.

Right-handed people live, on average; nine years longer than left handed people.

[Bavarian Motorist]

Originally Posted by apk919

The easiest calculation is to take the odds of 23 people having <b>unique</b> birthdays, and subtract from 1 (i.e. the odds of at least two of the people having a non-unique birthday).

You make the calculation by adding people to the room one at a time. So, the first person is "free" (since there's no one else in the room, their birthday can't match anyone elses). For the second person, the odds that they have a unique birthday is 364/365. For the third, 363/365 (since by definition the first two have unique birthdays). Fourth: 362/365, etc.

So the full calculation is: ((364/365) * (363/365) * (362/365) * ... * (343/365)) = 0.492703, which is < 0.5

That means the the odds of 23 people in a room having unique birthdays is < 50%... so the complement is that the odds of at least 2 people out of 23 in a room having the same birthday is (1 - x) where x is < 0.5... in other words, > 0.5 (50%)

Get it?

You're not factoring in leap year. Spaghettios!

[serpent]

Originally Posted by apk919

Get it?

btw still dont get it


There is a large brass statue of Winnie-the-Pooh in Lima, Peru.

The average four year-old child asks over four hundred questions a day.

In November 1999, two women were killed by a lightning bolt. The underwire located in their bras acted as a electrical conductors, and when the lightning bolt hit the bra they left burn marks on their chest.

Being unmarried can shorten a man's life by ten years. (i personally think this one is false )

[apk919]

Originally Posted by Bavarian Motorist

You're not factoring in leap year. Spaghettios!

The question was <b>based</b> on there being 365 days in the year. So it was the correct answer.

If you insist on leap years being included, then the equations just start with (365/366)... you still get the >50% result:

1 - ((365/366) * (364/366) * (363/366) * ... * (344/366)) > 0.5



It's actually <i>slightly</i> more complicated, because if you include 2/29, that day is not distributed uniformly with the other 365 days (it's 1/4 as likely as the others). Again, doesn't change the answer significantly...

Originally Posted by chapster5

My god people! enough with the math equations and on with the useless facts

What's wrong with a little useless mathematics?