3 ms·

Another example in science that you'd think is well understood, but isn't is water. We still don't know why and how clouds form or why ice is slippery, we don't

Another example in science that you'd think is well understood, but isn't is water. We still don't know why and how clouds form or why ice is slippery, we don't even know whether liquid water is strictly speaking a liquid and not a crystal some of the time.

mjevans 10y ago
My intuition on ice: * Black ice is clear because it is ice with nearly ice water as lubricant (and black because heat absorption makes it more likely for dark ground to cause it first); I think everyone accepts this. * Truly cold ice is more difficult. I suspect that it's easy for any piece that does stick to break off (under an uneven compression force), which provides a lot of small pieces that prefer to not stick to the ice it's self. Ice sticks to ice cube trays because it froze there and is thus force balanced to there. That's where I'd begin with theory and experiments if I wanted to take the time and effort to figure this out.
chadgeidel 10y ago
We don't know why ice is slippery? I thought that was understood as hydroplaning (small amounts of ice melt and then you have a low-friction scenario where water separates the two surfaces). I've read that when ice is cold enough and the other surface (a rubber tire for example) is also below freezing point there is good traction. Is there a description of this that a layman such as myself with a college degree in mathematics (heavy undergraduate physics) could understand?
- nkurz 10y ago
  It may be too basic for you, but I liked this 2005 overview from Physics Today: http://www.chemistry.northwestern.edu/documents/about/RosenbergPhysicsToday.pdf http://www.chemistry.northwestern.edu/documents/about/Rosenb... The problem with the popularly held "pressure melts the ice" theory is that ice can still be very slippery even at temperature-pressure points that are not explained by that explanation. It may be misleading to say that ice's slipperyness is "not understood", but it still is definitely an area of active research, with the understanding and theories evolving more rapidly than one might expect for something "obvious".
  - chadgeidel 10y ago
    Thank you!

mjevans 10y ago

My intuition on ice: * Black ice is clear because it is ice with nearly ice water as lubricant (and black because heat absorption makes it more likely for dark ground to cause it first); I think everyone accepts this. * Truly cold ice is more difficult. I suspect that it's easy for any piece that does stick to break off (under an uneven compression force), which provides a lot of small pieces that prefer to not stick to the ice it's self. Ice sticks to ice cube trays because it froze there and is thus force balanced to there. That's where I'd begin with theory and experiments if I wanted to take the time and effort to figure this out.

chadgeidel 10y ago

We don't know why ice is slippery? I thought that was understood as hydroplaning (small amounts of ice melt and then you have a low-friction scenario where water separates the two surfaces). I've read that when ice is cold enough and the other surface (a rubber tire for example) is also below freezing point there is good traction. Is there a description of this that a layman such as myself with a college degree in mathematics (heavy undergraduate physics) could understand?

nkurz 10y ago
It may be too basic for you, but I liked this 2005 overview from Physics Today: http://www.chemistry.northwestern.edu/documents/about/RosenbergPhysicsToday.pdf http://www.chemistry.northwestern.edu/documents/about/Rosenb... The problem with the popularly held "pressure melts the ice" theory is that ice can still be very slippery even at temperature-pressure points that are not explained by that explanation. It may be misleading to say that ice's slipperyness is "not understood", but it still is definitely an area of active research, with the understanding and theories evolving more rapidly than one might expect for something "obvious".
- chadgeidel 10y ago
  Thank you!