Tag Archives: Weather

DIY: Rain in a Bottle

Have you ever been sitting inside on a rainy day and wondered how exactly rain is made? With a simple experiment, you can make it rain anywhere (anywhere that’s some kind of closed container, anyway).


To perform this experiment, you will need hot (not boiling) water, plastic wrap, ice, and a container like a glass or a bottle.

Step 1:


You or an adult should heat up the water to the point when it begins to steam, but not actually boil. This can be done in the microwave (about 2 minutes, depending on microwave power and amount of water) or on the stove, so long as you exercise caution. If you choose a microwave as your heat source, use a microwave-safe container. If the water is boiling, let it cool and do not put it in anything plastic.

Step 2:

Pour the water into your glass, bottle, etc.and stretch the plastic wrap tightly over the top. Let this sit for a minute or two.

Step 3:

Set ice cubes over the plastic wrap and let it sit for 6-8 minutes. As time passes, you will see condensation form on the bottom of the plastic wrap. These drops will steadily grow until raining back down. You’ve made it rain indoors!

How it works:

When the steam rises off of the hot water, it comes in contact with the ice, which cools down the steam and condenses it to a liquid. This is a scaled-down version of something called the water cycle, where water evaporates from oceans, rivers, and other bodies of water, cools down and condenses into clouds in the atmosphere, and eventually rains back down on all of us.

Fire Tornado!

Tornadoes are born when extreme weather circumstances come together. Their short, destructive lives are still not fully understood, but one leading theory goes like this: sometimes, winds at different altitudes blow at different speeds, rolling the air between them into a horizontal, rotating cylinder. If a supercell thunderstorm is nearby, the spinning column can be pulled into the maelstrom. Once the tornado is vertical, its lower end has the potential to touch down and wreak havoc on Earth’s surface.

West Texas wildfire

West Texas wildfire. Image credit: Texas Forest Service.

In a real supercell, swirling updrafts are created by variations in temperature, pressure, and wind speed in the storm area. In this experiment, we simulate updraft conditions by physically pushing the air into a rotating column formation using a window screen rolled into an open-ended cylinder. Without the screen (and the wind it generates), the spinning fire doesn’t do anything especially interesting. That’s because of Bernoulli’s principle: the faster a volume of fluid moves, the more neighboring molecules are sucked into the breeze. By giving the air a push, we draw extra oxygen in towards the flame.


Fire tornadoes are spectacular in the lab, but you don’t want to see one in nature. These twisting ropes of flame have played a tragic role in several of the greatest conflagrations in human history. From Chicago to Peshtigo to Tokyo and beyond, they’ve spread blazes with devastating speed and blocked victims from reaching safety in nearby bodies of water.

At least one team of researchers is working towards harnessing the power of the fire whirl for practical purposes. Hot, clean-burning blue fire tornadoes show potential as a tool for improved oil spill cleanup.

As with any experiment involving combustion, check in with an adult, keep a fire extinguisher on hand, and exercise caution if you decide to make a flaming tornado at home. We used a turntable with a heat-safe covering, a non-flammable window screen stapled into a cylinder, duct tape, a glass flask, and a few ounces of 99% isopropyl alcohol to create our fire whirl.

Written By: Caela Barry

Godzilla El Niño and You

You’ve probably heard a lot about this year’s El Niño, which is predicted to be the biggest since 1998. What exactly does that mean? This global weather phenomenon has complex and far-reaching consequences, but the mechanism behind it is simple!

ThermoclineCupsLet’s start by considering normal weather patterns in the Pacific ocean. Water near the surface is heated by the sun. This warm upper layer floats on top of cooler, denser ocean depths, resulting in a dramatic temperature barrier called the thermocline. At left, we’ve modeled the thermocline in a plastic container: warm water is colored red, and cool water is colored blue. Because the warm water is less dense, it floats.

In a non-El-Niño year, equatorial trade winds blow strongly from east to west, moving surface water along with them. In the Pacific, these winds push the warm upper layer of the ocean towards Australasia. Cooler water wells up in the east to fill the space left by the warm water moving out. As a result, the thermocline sits at a slant. Surface temperatures are normally warmer in Indonesia than Ecuador by about 45 degrees Fahrenheit.

This tilt in the thermocline is responsible for the typically wet climate in Southeast Asia and relatively dry conditions along the Americas’ equatorial Pacific coast. Warm water near southeast Asia and Australia evaporates and blows inland, resulting in lots of rain. Cool, nutrient-rich water from deep in the ocean sustains whole ecosystems in the eastern Pacific, but doesn’t generate much precipitation.


During an El Niño year, the thermocline shifts, resulting in warmer than normal surface temperatures in the eastern tropical Pacific. Animation credit: NASA Goddard

In an El Niño year, trade winds weaken. With nothing to hold it in place, warm surface water sloshes eastward towards the Americas, leaving the western Pacific cooler than normal. Australia and southeast Asia experience drought conditions. The equatorial Americas see unusually intense precipitation, which comes in the form of coastal flooding in some regions and severe winters in others. Since warm water doesn’t vacate the eastern ocean, cool water can’t well up to replace it. Coastal ecosystems that depend on deep-ocean nitrates and phosphates struggle, undermining economies that depend on industrial fishing.

El Niño is defined as unusually warm surface water in the eastern tropical Pacific, but its consequences extend around the world. North of the equator, the western U.S. sees intense winter storms. Across the ocean, unseasonably dry weather disrupts agriculture in Indonesia, Australia, and even South Africa.

Although the thermocline’s oscillation isn’t precisely predictable, it is part of an ocean temperature cycle that repeats every two to seven years. So, yes, it’s going to be an intense season! That said, this is nothing that hasn’t happened before, and we’ll likely see a new “Godzilla” El Niño in another decade or a few.

Written by: Scott Alton, Caela Barry

Into Thin Air: CO2 Science

Carbon dioxide, or CO2, is one of the handful of compounds that most people are familiar with. People and animals breathe it out, plants love it, and we make a lot of it, which probably has some consequences. We are going to look at this well known gas in its solid form and hopefully answer any questions that come up along the way!

bigbubbs croppedSolid carbon dioxide is more often referred to by the name dry ice. This is because it never leaves behind a wet spot when it disappears. Unlike water, which will melt to a liquid naturally under normal conditions at room temperature, dry ice will instead skip to a gas. To the left, you can see dry ice under water releasing bubble after bubble of transparent carbon dioxide gas. This physical transition from a solid to a gas is called sublimation, and isn’t anything to be afraid of. Its just the less familiar cousin of evaporation and condensation. For more on that, check out this blog.

Here, we put our dry ice in a bowl of warm water. Water is constantly evaporating, and this warm water is no exception. As a result, the air above the water is very humid as it contains a lot of this evaporated water. One important thing about dry ice that hasn’t been mentioned yet: it’s cold. Like -109℉ cold. Brrr!

Adding it to the water causes air temperature to drop, forcing the water vapor in the air to condense. If it looks like fog, that’s because it is! We have simply made a low-flying cloud in a bowl! Clouds in real life form the same way. Warm air carries water vapour up into the high, cold parts of the atmosphere where they condense in the same way, minus the dry ice, of course.

The cloud forming is independent from the bubble expanding. This is a bit tricky. As the water vapor cools down and condenses it is not pushing out on the bubble. However, the dry ice is sublimating. the resulting carbon dioxide gas takes up more space. Unfortunately, CO2 is colorless. This makes it look like the cloud is blowing up the bubble, but really the cloud is just filling up the space that the sublimated dry ice is clearing out for it, until…

burst my bubble

The bubble bursts and the dense cloud falls to the ground, which looks really cool. It also raises a rather interesting question: If clouds are more dense than air, then what in the world are they doing way up there in the sky? The answer is a bit complex. The short version is that the tiny water droplets that make up clouds fall very slowly, but they tend to form in warm, rising, low pressure air that overcomes their slow fall, allowing them to float high in the sky.

For more information, I recommend reading this article.

Geyser in a Bottle! Science!!!

Ever wish you could control the weather? In this experiment, we’ll harness the weight of the atmosphere to make a tiny storm in a beaker! As you read this sentence, the air around you is exerting enormous pressure on your body. Imagine a jacket made of one-inch checkerboard squares. Now imagine that each tiny box weighs fifteen pounds! At sea level, atmospheric pressure is about 15 pounds per square inch. Multiply 15 by the number of square inches on the surface of your body to get an idea of how much weight you’re bearing every moment of every day.


Atmospheric pressure results from the weight of the air above you. Credit: Peter Mulroy, http://peter-mulroy.squarespace.com/air-pressure/

We don’t notice all this weight because we’re used to it. Take the pressure away, though, and awesome dynamics ensue. Heating a volume of air is one way to create a drop in pressure. Adding heat to a gas causes its molecules to speed up and spread out.


As the air inside the flask expands, some is pushed out through the tube. Invert the container into cool water and the liquid blocks the opening– the escaped air is trapped outside! The gas left inside the flask shrinks as it cools, creating a low-pressure zone in the container. Here’s where that 15 pounds per square inch comes in. Once the pressure in the flask is lowered, atmospheric pressure pushing on the surface of the water outside forces the liquid up the tube.

When the water reaches the main compartment of the container, the gas inside experiences a sudden drop in temperature. A chain reaction of cooling occurs, and water rushes in to fill the empty space left by the condensing air.

Cloud in a Bottle

Let’s take a look at the science of clouds!


Pockets of warm air near the Earth’s surface naturally float up through the atmosphere like hot air balloons. As an air pocket rises, it expands and cools down. This causes the water molecules within it to group together, creating droplets large enough to see. When a lot of these droplets gather in one place, they form a cloud. We usually observe clouds on a very large scale, but we can also create a cloud in a bottle by imitating the pressure & temperature differences found in nature.


Diagram of how a cloud forms. Credit: North Carolina State University

This experiment begins with a small amount of rubbing alcohol in a 2-liter bottle. There are several ways to do this demonstration. We use rubbing alcohol because it evaporates at a lower temperature than water, giving us a more impressive tabletop cloud!


First, we pressurize the bottle using an air pump.  Next, we release the pressure, causing the air inside the bottle to expand and cool (much like a pocket of warm air does as it rises through Earth’s atmosphere).  Just as cooling, expanding air causes water vapor to condense in nature, the cooling, expanding air in the bottle allows the rubbing alcohol to condense into a visible cloud of droplets.

fire light

This cloud looks very similar to the ones you see in the sky, but there are some important differences, as you can clearly see.



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