I bet you didnt know that

ytpe2r5bxkn0c1

sbsquarepants wrote: »

On a slightly related note - we all know that ice is slippery (insert hilarious rte news video here:D) But nobody knows why it is so slippery.
To explain - ice itself does not have a particularly low co-efficient of friction as it's surface on the microscopic level is quite rough. What makes it so slippery is the thin layer of liquid water that appears on the surface when something moves on the ice, smoothing out the peaks and troughs - what nobody yet understands is the how and why of that liquid water appearing. It appears even on ice that should be far too cold for water to exist in a liquid state, it was assumed for a long time that some mixture of heat from friction and pressure was the cause, but the numbers just don't add up even when dealing with small contact areas and high speeds like in the case of an ice skate blade.

Hence why they 'brush' the ice in curling to assist the slide of the stone.

sbsquarepants

Curling has got to be the maddest sport ever invented - but then I bet you did know that!:D

There was Russian husband and wife team failed a drugs test there recently. What drugs could possibly help you with curling (acid I suppose might help it make some sense, but apart from that!)

CruelCoin

sbsquarepants wrote: »

But nobody knows why it is so slippery.

"We now know that ice has a very thin liquid-like layer on its surface which, down to temperatures more than 35 degrees Celsius below zero, has been measured to be around 1 to 10 nanometers thick. This is why ice is slippery. It's also why ice-skating is possible at temperatures well below zero, which was another hotly debated topic because ice skating is possible at much colder temperatures than either a simple pressure melting or friction melting theory would predict. That layer exists because, unlike molecules inside the bulk of ice, which are attached to and pulled on by molecules from above and below, those at the surface are only attached to and pulled on by molecules from below. That imbalance disrupts the lattice structure so it 'collapses' into a quasi-liquid state."

http://www.abc.net.au/science/articles/2014/08/20/4067852.htm

There is always a tiny film of water on the surface of ice, and the pressure from a skaters blade drops the freezing point momentarily.

Physics Today paper on it, complete with graphs: http://lptms.u-psud.fr/membres/trizac/Ens/L3FIP/Ice.pdf

Have to say, i'm really enjoying this thread lads.

CruelCoin

sbsquarepants wrote: »

Curling has got to be the maddest sport ever invented - but then I bet you did know that!:D

There was Russian husband and wife team failed a drugs test there recently. What drugs could possibly help you with curling (acid I suppose might help it make some sense, but apart from that!)

Recent controversy over whether or not a curler had let go of the handle in time has led to calls for eagle eye, curling edition.

sbsquarepants

sbsquarepants wrote: »

But nobody knows why it is so slippery.

Correction - almost nobody:D

The article I was reading actually did mention that theory, but said it was still being disputed. This "quasi liquid" layer has also since been discovered on all manner of materials from various metals to semi conductors at temperatures well below their melting points.

Another interesting bit of ice trivia - there are actually 11 different types of ice, (12 if you count vanilla:cool:) classified by their crystalline structure - the stuff you throw lumps of into your drink to cool it down is known as ice Ih.

RiderOnTheStorm

I find water fascinating. I credit a very good physics teacher for the LC.
We all know that water is either solid, liquid or gas, depending on its temperature. But there is a triple-point, a temp at which all 3 states exist. Its very near zero degrees. I get that water can be part liquid and part ice right at point where its about to cross the lower border, but how the hell is there some gas there too? My teacher said gas, ie vapour, is present at nearly all temps , even if its a tiny thin layer very close to the surface. This is why windy days are better for drying clothes, than warm (and windless) days....says every housewife ever. The wind blows away the vapour, and the wet clothes then replace it from their stock, and the process repeats (until dry).

CruelCoin

RiderOnTheStorm wrote: »

I find water fascinating. I credit a very good physics teacher for the LC.
We all know that water is either solid, liquid or gas, depending on its temperature. But there is a triple-point, a temp at which all 3 states exist. Its very near zero degrees.

https://en.wikipedia.org/wiki/Phase_diagram#/media/File:Phase_diagram_of_water.svg

That triple point is at a very specific pressure.

I can't live without my coffee. That's why i'm never climbing Everest. The lower pressure makes water boil at 70-something celsius, meaning you always get a **** cup of joe.

RiderOnTheStorm

To add to the ice-is-slippy chat ...
I remember being told that is was pressure that caused the heat of reentry when space craft come back to earth, not the heat of air friction due to speed/friction. See bicycle pump and blackholes for example, says my old teach. Could it be same for ice skates? They are very thin, so pressure (per sq inch) is high. Enough to raise temp slightly to put it into the "slippy zone"?

Skylinehead

CruelCoin wrote: »

"We now know that ice has a very thin liquid-like layer on its surface which, down to temperatures more than 35 degrees Celsius below zero, has been measured to be around 1 to 10 nanometers thick. This is why ice is slippery. It's also why ice-skating is possible at temperatures well below zero, which was another hotly debated topic because ice skating is possible at much colder temperatures than either a simple pressure melting or friction melting theory would predict. That layer exists because, unlike molecules inside the bulk of ice, which are attached to and pulled on by molecules from above and below, those at the surface are only attached to and pulled on by molecules from below. That imbalance disrupts the lattice structure so it 'collapses' into a quasi-liquid state."

http://www.abc.net.au/science/articles/2014/08/20/4067852.htm

There is always a tiny film of water on the surface of ice, and the pressure from a skaters blade drops the freezing point momentarily.

Physics Today paper on it, complete with graphs: http://lptms.u-psud.fr/membres/trizac/Ens/L3FIP/Ice.pdf

Have to say, i'm really enjoying this thread lads.

Is that similar to how water can evaporate at room temperature? The bulk of it obviously won't (not boiling temperature, nowhere near), but at the surface individual molecules can have the energy to "escape" into the air.

jmayo

sbsquarepants wrote: »

Curling has got to be the maddest sport ever invented - but then I bet you did know that!:D

There was Russian husband and wife team failed a drugs test there recently. What drugs could possibly help you with curling (acid I suppose might help it make some sense, but apart from that!)

Yet another sport given to the world by the Scots.

At this stage there have been banned substances found in competitors of nearly every imaginable sport.
Although some argue what is and isn't a sport.

Remember how poor old Big Bill Werbeniuk had to give up the 30 pints of lager and was on Inderal which was banned.

BTW she is a real hottie

david75 wrote: »

Speaking of Endurance. Has anyone read that book of the same name, about Shackletons expedition to the Antarctic to cross it on foot?
The never ending series of disasters and efforts and trials and endurance’s the crew went through, being stuck down there for years, If it was a film it would be totally completely unbelievable.
Amazing read no matter what. Can’t recommend it enough.

And right by his side was a Kerry man.

Shackleton never lost a man under his command.
Three men were lost in the Ross Sea party, but that was not under his direct control. It was under the control of Aeneas Mackintosh, who was one of those to die.

Oh and as opposed to most of the other British explorers e.g Scott he was not Royal Navy, but Merchant Marine.
Crean was Royal Navy.

Frank Worsley the absolutely fantastic navigator that steered the James Caird lifeboat from Elephant Island to South Georgia was also Merchant Marine but server in Royal Navy reserve.

BTW there was another Irish man, Cork born Timothy McCarthy on that expedition and he was also one of the 6 to make the Elephant island to South Georgia trip.
He also has the dubious distinction of being the first member of the Weddell Sea party of the Imperial Trans-Antarctic Expedition to die in World War 1.
Lionel Greenstreet has the distinct of being the last surviving member of the Weddel Sea party to die in 1979.

topper75

The only three countries that host both red and grey squirrels in the wild are Ireland, Britain, and Italy.

david75

I saw a red squirrel in the Phoenix Park about two months back and was sure I was seeing things as I had thought they were now extinct or near enough to it but no, sitting on the ground watching me and the dog. He took off up into the tree soon as I moved to get a pic. Ragin.

quickbeam

Capt'n Midnight wrote: »

When Isaac Newton was head of the UK mint he had a Mr Chaloner hung, drawn and quartered for making counterfeit coins

I never heard of him, but fascinating reading.

VW 1

The curlers failed the drug test, testing positive for meldonium. A lot of sports stars had been taking this, most famously Maria Sharapova was banned for it.

The primary purpose of it is to treat coronary heart disease, thought to help performance by expanding arteries and increase blood flow.

CruelCoin

Skylinehead wrote: »

Is that similar to how water can evaporate at room temperature? The bulk of it obviously won't (not boiling temperature, nowhere near), but at the surface individual molecules can have the energy to "escape" into the air.

The molecules are moving, and sometimes have the kinetic energy to break through the waters surface.

https://chemistry.stackexchange.com/questions/7449/why-does-water-evaporate-at-room-temperature

I'm by no means a matter expert, i'm just good at using google.

CruelCoin

VW 1 wrote: »

The curlers failed the drug test, testing positive for meldonium. A lot of sports stars had been taking this, most famously Maria Sharapova was banned for it.

The primary purpose of it is to treat coronary heart disease, thought to help performance by expanding arteries and increase blood flow.

It's weird how many athletes get exemptions for drug use for "medical treatment" reasons.

You'd swear they're the sickliest bunch of people on earth.

CruelCoin

When Honeybees mate with the Queen during her maiden flight, the male turns his penis inside-out in the queens sting chamber. The penis bursts during the act of climax, and the male bee dies soon after.

So, the queen leaves behind her a trail of penisless corpses.




That's a thing you know now.

ohnonotgmail

Jimmy Carter was the first US president born in a hospital.

jmayo

david75 wrote: »

I saw a red squirrel in the Phoenix Park about two months back and was sure I was seeing things as I had thought they were now extinct or near enough to it but no, sitting on the ground watching me and the dog. He took off up into the tree soon as I moved to get a pic. Ragin.

They are making a major comeback particularly in parts of the Midlands and AFAIK it is down to the reemergence of Pine Martens.
The same thing has been noticed in Scotland where Pine Martens numbers come back, grey squirrel population drops and the reds then make a comeback.

It is good to see the yankie invaders get their comeuppance.

CruelCoin wrote: »

It's weird how many athletes get exemptions for drug use for "medical treatment" reasons.

You'd swear they're the sickliest bunch of people on earth.

Especially those Russians and those cyclists.
What sickness did Sky's Bradley Wiggins have again ?

david75

jmayo wrote: »

They are making a major comeback particularly in parts of the Midlands and AFAIK it is down to the reemergence of Pine Martens.
The same thing has been noticed in Scotland where Pine Martens numbers come back, grey squirrel population drops and the reds then make a comeback.

It is good to see the yankie invaders get their comeuppance.



Especially those Russians and those cyclists.
What sickness did Sky's Bradley Wiggins have again ?

Ah that’s great news! I hadn’t seen one in years. Good to hear they’re making their way back

Wibbs

david75 wrote: »

Ah that’s great news! I hadn’t seen one in years. Good to hear they’re making their way back

Years ago I knew a chap with a decent plot of land in Wicklow. Mostly woodland. He hadn't seen a red squirrel in years. The greys were causing damage IIRC so he went about trapping them(he released them elsewhere*). Within a few months reds started to come back from apparently nowhere.







*I remember thinking at the time that was probably illegal?

CruelCoin

CruelCoin wrote: »

It's weird how many athletes get exemptions for drug use for "medical treatment" reasons.

You'd swear they're the sickliest bunch of people on earth.

Rugby seems to be the most popular sport for asthmatics.

Wibbs wrote: »

Years ago I knew a chap with a decent plot of land in Wicklow. Mostly woodland. He hadn't seen a red squirrel in years. The greys were causing damage IIRC so he went about trapping them(he released them elsewhere*). Within a few months reds started to come back from apparently nowhere.







*I remember thinking at the time that was probably illegal?

Shush...

ytpe2r5bxkn0c1

david75 wrote: »

I saw a red squirrel in the Phoenix Park about two months back and was sure I was seeing things as I had thought they were now extinct or near enough to it but no, sitting on the ground watching me and the dog. He took off up into the tree soon as I moved to get a pic. Ragin.

The park is one of the last remaining strongholds for Reds in Leinster, with much work in recent years to control the number of Greys there, on order to help the Red population.

david75

We see greys every day when we’re up there. I won’t say they’re fearless but they’re definitely cheeky. The odd time they see my dog coming and run up the tree but only to about 6 or 7 feet up, then they’ll circle the trunk, totally taunting him as they’re just slightly out of reach of him jumping to try get them

Could be they’ve become used to dogs as there’s that many in the park every day. But it’s funny to watch too.

Knex*

I'm late to the astronaut conversation, but anyone interested in the space side of things could get enjoyment from this radio lab interview, entitled Dark Side of The Earth.

Just 20 mins long, it describes how '200 miles above Earth's surface, astronaut Dave Wolf -- rocketing through the blackness of Earth's shadow at 5 miles a second -- floated out of the Mir Space Station on his very first spacewalk. In this short, he describes the extremes of light and dark in space, relives a heart-pounding close call, and shares one of the most tranquil moments of his life'.

http://www.radiolab.org/story/242184-dark-side-earth/

Here's another snippet from the accompanying article.

Out in blackness of space, the contrast between light and dark is almost unimaginably extreme -- every 45 minutes, you plunge between absolute darkness on the night-side of Earth, and blazing light as the sun screams into view. Dave and Anatoly were tethered to the spacecraft, traveling 5 miles per second. That's 16 times faster than we travel on Earth's surface as it rotates -- so as they orbited, they experienced 16 nights and 16 days for every Earth day.

Dave's description of his first spacewalk was all we could've asked for, and more. But what happened next ... well, it's just one of those stories that you always hope an astronaut will tell.

Some more context.

Here is a great photo of what space looks like if your back is to earth, whilst you're hanging in space, and the light is illuminating the space beyond.

http://spacetelescope.org/images/ann1110a/

Very hard for me to do justice to the actual verbal account from Dave Wolf, so I would encourage people to listen to it.

CruelCoin

Knex. wrote: »

Just 20 mins long, it describes how '200 miles above Earth's surface, astronaut Dave Wolf -- rocketing through the blackness of Earth's shadow at 5 miles a second -- floated out of the Mir Space Station on his very first spacewalk. In this short, he describes the extremes of light and dark in space, relives a heart-pounding close call, and shares one of the most tranquil moments of his life'.

I love stories from spacewalks.

Scott Kelly told a story of how on his spacewalk he was going over the handrails, and he was shocked to see how it was full of holes from micro-meteorites.

The whole station is covered with shock absorbing cladding, but the handrails are not. Some of them apparently look like someone has shot a rifle clean through them.

CruelCoin

Knex. wrote: »

http://www.radiolab.org/story/242184-dark-side-earth/

I was on a boat in the red sea last autumn, and at night I was blown away by the density of the stars / milky way.
What you can see when you get away from light pollution is amazing.

lmimmfn

CruelCoin wrote: »

I was on a boat in the red sea last autumn, and at night I was blown away by the density of the stars / milky way.
What you can see when you get away from light pollution is amazing.

and no clouds

dxhound2005

Some animals, including humans, intentionally kill members of their own species. The highest murder rate is among meerkats. Some other species do not show this behaviour.

http://www.independent.co.uk/news/science/meerkats-revealed-as-the-most-murderous-mammal-known-to-science-a7335741.html

Capt'n Midnight

jmayo wrote: »

Shackleton never lost a man under his command.
Three men were lost in the Ross Sea party, but that was not under his direct control. It was under the control of Aeneas Mackintosh, who was one of those to die.

They split into two groups to setup depots so the Shackleton party would find them.

The difference was that one group took all its stuff out in one go and continually moved forward from their previous depots. The other group would go back to base camp between the relays. So they got a small chance to recuperate but as it turned out later, far more importantly a chance to eat seal meat and so avoid the scurvy that decimated the first group.

It's not that the first group didn't know about scurvy it's that everyone was so unprepared. The reverend who died was on a scurvy supplement, but it only had about a thirtieth of the Vitamin-C that he needed. Like Scott a little more luck , or better preparation and he'd have survived.