nowhere of water droplets?

[Turtle]

Originally Posted by Jay-qu

I understand that rain drops can take a few different shapes - but not perfectly sphereical ones. So my question is why do we get round hail?

Hail isn't always round (spherical), & the smaller it is, the less chance it has to get spherical. Hail is created when precipitation freezes, falls, & then is pulled against gravity by updrafts, As it rises it collects more water which then frezzes to form another layer of ice. Once the overall weight of a stone is sufficient to negate the updraft, the hailstone falls to the ground. Because the hailstone is solid as it forms, it may tumble in the air which distributes the new layers more or less evenly. A perfectly spherical hailstone I expect is rather anomolous.

[steelengineer]

Originally Posted by insight

Convection is nothing to do with gravity. As long as there is air to be transfered heat, convection takes place. Gravity pulls the air. If there is no gravity, there is no air and the convection also never happens. the density of air is lower in zero g, which interns to oversize the water doplet volume and the overall relative humidity ratio within the droplet boundary maintains.

the way i understand convection is that, the lower density fluid (liquid or gas) escapes to the top making the higher density fluid fill in the empty space. this is because the higher desity fuid has more mass per volume, and hence is pulled strongly downwards due to gravity relative to the lower density fluid. so where did i go wrong?

the inclusion of vaccum in the question no doubt removes all possibility of convection happening since there is no mass! and

Originally Posted by insight

If there is no gravity, there is no air

what does the existance of air have to do with gravity, and vice versa?????

[Jay-qu]

I understand how hail is created but around my house we always get round hail... ok ill admit its not perfect its slightly bumpy like a golf ball but the general shape is round

oh and steelengineer without gravity our planet would not hold the atmosphere in place - it would float away into space, I think thats what insight was getting at

[Turtle]

Originally Posted by Jay-qu

I understand how hail is created but around my house we always get round hail... ok ill admit its not perfect its slightly bumpy like a golf ball but the general shape is round

___Interesting observation JayQ. Given that a dimpled sphere (golf ball or otherwise) travels farther than a smooth sphere given the same applied force, may we assume these hailstones travel farther in the updraft & so stay longer & so grow thicker layers?
___Theorizing a 'perfectly' spherical hailstone is one thing, but finding one is another. On further thought, I'll stick my neck out & say they don't exist. Fractal boundary & all that.

[Jay-qu]

Originally Posted by Turtle

___Interesting observation JayQ. Given that a dimpled sphere (golf ball or otherwise) travels farther than a smooth sphere given the same applied force, may we assume these hailstones travel farther in the updraft & so stay longer & so grow thicker layers?
___Theorizing a 'perfectly' spherical hailstone is one thing, but finding one is another. On further thought, I'll stick my neck out & say they don't exist. Fractal boundary & all that.

Interesting idea... and yeah well nothing is perfect, but if there was one finding would be one thing - storing would be another, you cant touch it because it would melt unevenly... next time it hails i will take a few samples and if i get around to it i might photograph them and post it.

[Turtle]

Originally Posted by Jay-qu

Interesting idea... and yeah well nothing is perfect, but if there was one finding would be one thing - storing would be another, you cant touch it because it would melt unevenly... next time it hails i will take a few samples and if i get around to it i might photograph them and post it.

___Sweet! While driving in Kansas once a hailstorm hit with stones just slightly smaller than a baseball. I managed to pull off under an awning before it really let loose & it still ranks as one of the most awsome weather events I ever witnessed. It lasted about 3 to 5 minutes & made a sound like none I've ever heard. After it stopped, everyone's first interest went to rushing out to pick up the hailstones. Never mind the dents in the hood or broken windshields. I broke one open & counted about 15 layers of ice.

[CraigD]

Originally Posted by Turtle

… Given that a dimpled sphere (golf ball or otherwise) travels farther than a smooth sphere given the same applied force, may we assume these hailstones travel farther in the updraft & so stay longer & so grow thicker layers? …

I don’t know if golf-ball like dimpling of hailstones has a significant effect on them, but if it does…

The reason dimpled golf-balls fly further is that the dimples set up a boundary layer of air around the ball that reduces its effective aerodynamic drag. A hailstone with less drag would fall faster in an updraft, reaching the ground sooner (and having accumulated less ice) than a less aerodynamic one of the same mass.

So, if you want really super hailstones, give them little, high drag parachutes, wings, or something, allowing them to stay aloft and gather ice longer. Its hard to imagine a way this could happen naturally, though, so I expect that the size of hailstones is determined more by the strength of the updraft, the amount of water available, and the coolness of the air layer that cools them enough to make them accrete ice.

[Turtle]

Originally Posted by CraigD

I don’t know if golf-ball like dimpling of hailstones has a significant effect on them, but if it does…

The reason dimpled golf-balls fly further is that the dimples set up a boundary layer of air around the ball that reduces its effective aerodynamic drag. A hailstone with less drag would fall faster in an updraft, reaching the ground sooner (and having accumulated less ice) than a less aerodynamic one of the same mass.

So, if you want really super hailstones, give them little, high drag parachutes, wings, or something, allowing them to stay aloft and gather ice longer. Its hard to imagine a way this could happen naturally, though, so I expect that the size of hailstones is determined more by the strength of the updraft, the amount of water available, and the coolness of the air layer that cools them enough to make them accrete ice.

___On the bolded Because the air IS what applies the force right?
___Now Jayq actually said 'slightly bumpy' then followed with 'like a golf ball'. A golf ball is 'bumpy' because of 'dimples'; what if the hailstone is 'bumpy' with protruberences?

[Jay-qu]

yeah it wasnt really the best example but the have a what seems to be a bit of both... slight dents and raised parts...

[Turtle]

Originally Posted by Jay-qu

yeah it wasnt really the best example but the have a what seems to be a bit of both... slight dents and raised parts...

___On further reflection I have to chuckle When does the bumpyness stop being dimply & start being protuberenty? I mean every dimple has protuberent sides & every protuberence has dimply sides.