Science Megathread

[Blockzillahead]

I do believe there is no proven reason yet, but my best guess is that either some of it evaporates meaning less water to freeze, or perhaps little air bubbles in the liquid act as 'seeds' for the ice crystals to start forming

http://library.thinkquest.org/C008537/cool/freeze/freeze.html

[Ad Bot]

[Doomonkey]

The particles have momentum, but the rate of which this energy is lost does not.

When did anyone say that the rate of something had a momentum?

EDIT: But on the topic of boiling water freezing...

We know that in order to speed up a chemical or physical reaction some of the things you can do are increase the speed of the particles involved and increase the surface area of the object involved. We also know that the volume of a shape increases at a higher rate than the surface area of a shape, so it would stand to reason that if you break a large object into many smaller objects your surface area would greatly increase.

Putting these pieces of knowledge together, we might realize that if one wanted to freeze water quickly they might do it by changing the water from one large mass to many small masses and by increasing the speed at which the water molecules are moving. These conditions can be easily created by boiling water.

[Frosting]

Scientists may have discovered that their thoughts about absolute zero may all be incorrect. It was originally thought that when all atomic movement stopped, the point of absolute zero was reached. Now, they may have discovered that despite the fact an atom may cease to move, it's subatomic particles and quarks may still be moving.

[Count]

Now that this is a science megathread...ANATOMY FTW.

[Fluff-is-back]

Scientific bump!

[King Leo]

Scientists may have discovered that their thoughts about absolute zero may all be incorrect. It was originally thought that when all atomic movement stopped, the point of absolute zero was reached. Now, they may have discovered that despite the fact an atom may cease to move, it's subatomic particles and quarks may still be moving.

That is true. The energy of a particle can only be on discrete levels, kinda like steps on a ladder. The lowest step on this ladder is the ground state of the particle, and can only be achieved at 0 kelvin. However, this ground state does not equal to 0 energy.
This can easily be explained by the Heissenberg uncertainty principle, stating that you cannot predict both the position AND the momentum of the particle with absolute precision. If the particle would have had 0 energy, it would have been possible to predict both its momentum and position, thus breaking the uncertainty principle.

The weird things about quantum mechanics is that the particles don't really give a stuff about what is allowed and what isn't. A particle can be trapped inside a box with barriers requireing infinite energy to pass through. The particle isn't allowed to be inside the barrier or on the outside of the box. Yet sometimes, it still is.
This concept is called Quantum Tunneling.
A neat little video explaining it a bit better than I do: http://www.youtube.com/watch?v=cTodS8hkSDg

[Ipquarx]

Fluid physics question:
Say there's a large container filled with water.
That water is 100% still, no waves or otherwise net force going through it.

If there was a hole in the bottom of the container, in what cases would a whirlpool form, slowly drain out with no whirlpool, or just create a big hole like this occur, depending on the depth of the water and the radius of the hole?

[Mardalf]

Megascience

[Shadowed999]

REDACTED

[Fluff-is-back]

Fluid physics question:
Say there's a large container filled with water.
That water is 100% still, no waves or otherwise net force going through it.

If there was a hole in the bottom of the container, in what cases would a whirlpool form, slowly drain out with no whirlpool, or just create a big hole like this occur, depending on the depth of the water and the radius of the hole?

Just a guess that no hole would form due to no need for air to escape from the hole.

[dkamm65]

Fluid physics question:
Say there's a large container filled with water.
That water is 100% still, no waves or otherwise net force going through it.

If there was a hole in the bottom of the container, in what cases would a whirlpool form, slowly drain out with no whirlpool, or just create a big hole like this occur, depending on the depth of the water and the radius of the hole?

Often in sinks, toilets, bathtubs, etc., the water is already moving, though
maybe very slowly. As the water drains, that slow rotation becomes more
visible. In the case of a sink or bathtub, where the width of the pool
decreases as it drains, the rotation increases speed as it drains. This is
because angular momentum is conserved (think of a figure skater speeding up
as she pulls her arms into her body -- it is the same effect). In a draining
tank, the water by the drain has the least momentum. As it leaves, the
remaining water with more momentum takes its place. If an object with
angular momentum moves closer to the center of its rotation, it speeds up.
So, the water gradually picks up speed, and you see rotation.

Even if there is *no* angular momentum to start with, fluid can start to
rotate. This is called a "secondary flow". To understand why secondary flows
develop, you have to understand the nature of viscosity. When molecules of a
liquid are attracted to each other, they resist being pulled apart. For
example, when you move your hand through water, you are dragging molecules
of water with your hand. Some of the resistance is simply the inertia of the
water, but much of it is viscosity. The molecules that you accelerate pull
on the ones next to them, and those next to them, etc. Moving water
molecules across each other, a 'sideways' force, is called 'shear'.
Resistance to shear is called viscosity.

Imagine a large cylindrical vessel full of water with a small drain at the
bottom. When you open the drain, water starts to flow down the hole. Of
course you have taken great care to ensure the water is completely
stationary first, and that opening the drain does not perturb it. As the
water flows downward, it drags the molecules around it due to viscosity. At
the point of the drain, some of the molecules go down the drain, but other
ones cannot fit. Yet, they have still gained some energy by being dragged by
the ones that did go down the drain. They have to go somewhere, and since
they cannot go down, and gravity makes it hard to go up, they go sideways.
Over time, they start a rotational flow, called 'secondary flow'. Over a
short period of time, viscosity, caused by the molecules' mutual attraction
to each other, ensures that they move together in the same direction. In
time, a vessel with a drain full of stationary water will develop a quite
noticeable rotation due to secondary flow.

Another place where secondary flows commonly occur is in tea. Here, the
opposite occurs: a rotational flow causes vertical motion. If you drink
green tea, watch the leaves as you stir it. Even though you are stirring the
tea in a rotational direction, you can see the leaves are pushed upward. The
upward motion, caused by viscosity in response to the rotation, is another
example of secondary flow. Of course, depending on how you stir, it could be
your spoon moving them up, not secondary flow. So be careful. :)

A lot of research has been performed to understand how and when secondary
flows occur. It turns out that any viscosity gradient can cause a secondary
flow. Sometimes secondary flows are hard to see (they can be very
small/slow), but they are there! This is the underlying reason for the
'swirl' you see.

http://wiki.answers.com/Q/Why_does_water_run_down_a_bathtub_drain_in_a_swirl

[Fluff-is-back]

That's cheating :c

[MegaScientifical]

Wait, where did this topic come from?

[Night Fox]

Wait, where did this topic come from?

what?

[Doomonkey]

Scientists may have discovered that their thoughts about absolute zero may all be incorrect. It was originally thought that when all atomic movement stopped, the point of absolute zero was reached. Now, they may have discovered that despite the fact an atom may cease to move, it's subatomic particles and quarks may still be moving.

Except if a subatomic particle is moving then the atom is moving. While the body may be stationary its parts are not. If my finger is moving then I am moving.