The Science of Summer

Why does ice cream look different when it melts in your car and gets refrozen?
If you have ever made homemade ice cream, you may have noticed that it takes a lot of work. My family’s ice cream maker looked a lot like this one which was electric but needed a little more monitoring than the ones we have today.

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The key to some good ice cream is keeping it at the perfect temperature and keeping it moving. Commercial creameries have special machines that continually stirs the ice cream while it is being frozen. These machines cool the ice cream much more quickly than my home machine ever could, which is why their ice cream is much creamier. It prevents larger ice crystals from freezing in the ice cream.

When ice cream melts in the Houston heat on your way home from the grocery store, you may notice that it’s not quite the same consistency any more. If you put the ice cream back into the freezer, it will refreeze, but over a longer period of time than the original ice cream. In addition when you re-freeze the ice cream, you aren’t churning the mixture. This allows larger crystals to form which affects its appearance and its creamy consistency. It is not recommended to refreeze ice cream that has been left out for a longer period of time. Ice cream is made out of dairy, so it can grow bacteria or spoil if left out for too long!

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How does sunscreen actually work?
First, we have to talk about what happens to cause your skin to burn. When you are out in the sun, your skin is exposed to sunlight which is made from ultraviolet (UV) radiation. Ultraviolet radiation can be subdivided into three categories based on wavelength. UV-A radiation has the longest wavelength. It is not absorbed by our atmosphere’s ozone layer and it is the type of UV that is responsible for long term skin damage. UV-B radiation has a shorter wavelength than UV-A. Some of the UV-B radiation is absorbed by the ozone layer and the remaining UV-B radiation that reaches the earth’s surface is responsible for sunburns. The last type of UV radiation is UV-C radiation. It has the shortest wavelength and it is completely absorbed by our atmosphere. On the Earth’s surface, we are not affected by UV-C radiation, but it could be an issue for astronauts if they didn’t have those protective suits. Sunscreen protects our skin from the two most common forms of UV radiation on the earth’s surface – UV-A and UV-B.

Essentially, sunscreen forms a thin, invisible protective layer on the surface of our skin. It uses organic and inorganic active ingredients to form that protective layer. The organic ingredients such as octyl methoxycinnamate and oxybenzone absorb UV rays. When the rays are absorbed, the energy is harmlessly dissipated in the form of heat. Some of the organic materials in sunscreen will slowly break down over time, which is why we need to reapply sunscreen regularly. The inorganic active ingredients like zinc oxide or titanium dioxide reflect the UV radiation essentially preventing the UV radiation from hitting the skin. Early versions of sunscreen were opaque and white, which reflected the UV radiation well. However, it wasn’t the most appealing look for the beach. With newer technology, they’ve made these inorganic materials much smaller and nearly invisible.

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How can I cool down a warm beverage quickly?
It’s the middle of summer, and when you walk outside it feels like you have walked through a curtain of heat and humidity. Nothing sounds better in a Houston summer than a nice, cold drink. But we’ve all forgotten to move something from the pantry to the fridge, and ended up with a warm drink instead. Even when you move that drink to the fridge, it can take over 45 minutes to reach the cool temperature you’d prefer. Here are a few ways to cool down your beverage quickly, and the science on how it works.

Option 1: The Wet Paper Towel Method.
Wrap your bottle or can in a wet paper towel and place in the fridge. The drink will cool down much faster with the wet paper towel because of how heat is transferred. Normally, heat will transfer from a higher temperature object to a lower temperature object. In the case of the drink in the fridge, the heat will transfer from the soda can (higher temperature) to the air in the fridge (lower temperature). Heat can be more easily transferred through a solid like the soda can because the atoms are closer together on average. It is much more difficult with a gas like the air in the fridge because the atoms are more spread out on average. When we put a wet paper towel onto the outside of the can, we are using a liquid to facilitate the transfer of heat more easily than with air. Water from the towel will evaporate from the towel and the remaining water will be cooler. This process is called evaporative cooling. The wet towel also conducts the heat from the can cooling the soda to the temperature you prefer.

Option 2: The Salt & Ice Water Method.
Fill a bowl with ice and water, then pour salt over the icy mixture. Place the can or bottle in the bowl, and stir. It should be colder in about 5 minutes. The reason that this method works so well is trifold. First, you are lowering the melting point of the ice when you add salt so the mixture will be colder than 32° F. Basically as the ice is melting, it is using up a little bit of energy to break bonds causing the remaining water to be colder. Having a colder liquid helps the heat transfer between the liquid and the soda can. Which brings me to the second reason that it cools quickly – it’s a liquid! As we mentioned in option 1, heat can be transferred more easily through water than through air, so the water is facilitating the heat transfer. Lastly, stirring the bottle or can around in the mixture can reduce the amount of time needed to cool down the soda. If you did not stir the mixture, then the can would slowly transfer heat to the liquid surrounding it making the liquid immediately surrounding it warmer. The transfer of heat would continue slowly until both the can and the liquid reach equilibrium. By stirring the mixture, you are exposing the can to more of the cold water which speeds up the transfer of heat. In both situations, the can and liquid are reaching equilibrium, but over different amounts of time.

With either cooling option, you will get a nice cold beverage quickly and now you know the science behind it!

Ice Planet: Earth

There has been much discussion and confusion about global climate change. With an upcoming lecture and planetarium show on the topic, you have an opportunity to discover the facts and whether or not you should be concerned about the climate. This month we invite you to learn more about ice and glaciers, and the effect these have on our planet.

Ice Planet: Earth

On Wednesday, May 26 at 6:30 p.m. Dr. Mark Fahnstock will discuss the changes of our planet’s ice cover, specifically how it has changed over the past year, decade, and century. Dr. Fahnstock, who studies the glaciers of Greenland and the Antarctic, explains his research to the public. Don’t miss his lecture and the chance to learn more about global warming and our planet’s weather.

Ice Worlds

If you are interested in global climate change, the Poles are the place to watch because changes there can have a dramatic effect on the whole planet. When ice turns to water, it changes from a reflector to an absorber of solar radiation. When water turns to water vapor, it becomes a powerful greenhouse gas. When water vapor forms clouds, it becomes a reflector once again.

In 2007-2009, countries around the world celebrated the International Polar Year with expanded funding for research on Earth’s changing poles. On Memorial Day weekend, the Burke Baker Planetarium opens a new Ice Worlds show featuring what has been learned about the Arctic and Antarctic in the past two years.

Understanding the role of ice on our world is the first step in understanding how water amplifies any climate change. Ice Worlds is a beautiful show, including ice imagery from Earth’s poles and from the different ice-covered worlds in our solar system.

Live From the Poles: North Lake and the Journey Home

Our guest blogger today is Chris Linder, a Research Associate at the Woods Hole Oceanographic Institution in Massachusetts. He is the project manager and field photographer for the National Science Foundation-sponsored Live from the Poles project. He’s been sending us weekly updates about their progress.

On July 21, scouts, summer campers and Ecoteens had a chance to get their most pressing climate questions answered from Ian Joughin, the leader of the Greenland Glacier Expedition that Chris has been writing about here through a live satellite link to the campsite in Greenland; later that night, adults got their turn. You can listen in, below.


The team is now back from the Greenland; here’s Chris’ last post on what they learned.

North Lake and the Journey Home

It has been a whirlwind since my last post—a hectic final week on the Greenland ice sheet studying two glacial lakes, a helicopter transfer back to the town of Ilulissat, and a long series of flights taking us home. Warm socks and down jackets are now a thing of the past—I’m typing this dispatch in 87-degree heat in Seattle (I know that’s not really hot for Texans, but it’s quite a tough adjustment for me after a month of subfreezing temperatures!)

A final aerial survey just before we left showed
that the lakes were beginning to form ice on the
surface again. As winter returns to the ice, the
lakes will freeze solid and remain frozen
until the next summer. © Chris Linder, WHOI

Our final week on the ice was dedicated to exploring two nearby lakes, one of which had recently drained (dubbed “North Lake”) and another that was partially full of water when we arrived (dubbed “North North Lake”).

North Lake made the news earlier this year when Dr. Sarah Das (Woods Hole Oceanographic Institution) and Dr. Ian Joughin (University of Washington Applied Physics Lab/Polar Science Center) published a pair of papers in the journal Science about the spectacular draining event that they captured with their instrumentation in July 2006. That summer, a giant hole called a moulin opened up in the lake bed and drained the entire water volume (which is a lot; this lake is several kilometers long!) in an hour and a half. This year, the lake was already empty when we arrived (in fact, we had already heard from colleagues that it drained on July 10, the day we arrived at South Lake camp), so the research team had the freedom to explore the empty lake basin on foot.

The dimpled surface on these tilted blocks shows
that these were part of the former lake bed. The
cracking of the ice sheet surface caused them to break
free and float to the surface as the lake drained.
© Chris Linder, WHOI

Our visits to the North Lake basin revealed a bizarre landscape of car-sized blocks, canyons, rivers and waterfalls. The variation in the landscape on the ice sheet, particularly in the drained lake beds, is staggering. I expected it to be, well, flat, and white.

What we saw was quite different—towering blocks of pushed-up ice, rivers of freezing melt water carving their way through 60-foot deep canyons, gaping bottomless cracks and holes. The color of the ice ranges from opaque white to clear to bluebird blue. To my glaciologist companions, the landscape was also an open book. The blocks indicate where major cracks occurred (the blocks are pieces of the ice sheet that are broken loose during the cracking), and the rivers lead us to the crevasses (cracks) or holes (moulins) where the water was still pouring through the ice sheet to the bedrock. If you put your ear to the cracks, you can hear the water echoing in the depths.


Moulins, or holes in the ice sheet,
can be an otherworldly blue.
© Chris Linder, WHOI

It will still be some time before the final picture of the 2008 lake draining can be told. The scientists had only a brief amount of time to examine their instruments and prepare them for another year of data collecting before we had to pack up and fly out. In the coming months, scientists will be examining the data their instruments collected over the previous year. Dr. Mark Behn, a scientist from the Woods Hole Oceanographic Institution’s Geology and Geophysics department (and resident “icequakes” expert), had this comment about the data he did look at:

“Even with a 10 minute look, I can see that the quality of the data is good, which tells me the instruments are working. We can also see the timing of large cracking events that drain the lakes, which stand out as dramatic spikes on the record.”

Be sure to check the Polar Discovery website to read dispatches about our other adventures at North Lake, including the release of a harmless tracer dye into a moulin and the investigation of “North North Lake.” 

Thank you to everyone who came in to the museum on July 21 to talk with moderator Twila Moon and Dr. Ian Joughin live from the ice. Stay tuned for future Live from the Poles expeditions on the Polar Discovery website. Until then, best wishes and thanks again for reading,

Chris

Interested in learning more about Chris, his team and their journey to Greenland?
Learn about the purpose of this trip.
Travel to Greenland with him.
Read what they did their first week.

A New Home on the Ice

Our guest blogger today is Chris Linder, a Research Associate at the Woods Hole Oceanographic Institution in Massachusetts. He is the project manager and field photographer for the National Science Foundation-sponsored Live from the Poles project. Today – in addition to sending us weekly updates -Chris and fellow researcher Dr. Ian Joughin made a live call to our summer campers in the Burke Baker Planetarium; we hope to post the audio from the call here soon. If you’ve got questions of your own, visit us tonight – they’ll be calling us back. For now, here’s more from Chris, from the ice sheet: 

The camp at North Lake

We have been camping on the ice sheet for over a week now, and it’s amazing to think how familiar this environment now seems, especially compared to how foreign it felt when I stepped off the helicopter.

Some of the peculiarities of living on a 3,000-foot thick slab of ice:

– Water: you don’t have to carry a water bottle on a hike, just a cup. The water is the best tasting I’ve ever had.
– Cooking: no refrigeration required! We made a no-bake cheesecake the other night and it was quite a treat. Just left it outside the cook tent to chill…
– Slippery tents: instead of using tent stakes to secure the tents, we use ice screws, which are 6-inch metal screws. The problem is, they heat up in the sun and melt out after a day, so we spend a lot of time repositioning the ice screws.
– No night: this is a tough one—the 24 hours of daylight make it hard to sleep and it’s easy to forget what time it is.

The past week has been a busy one—we typically wake up at 8 a.m. and sometimes don’t finish work until 1-2 a.m. The science team has been working nonstop to refurbish their long-term instruments and survey the terrain by foot and air. They successfully installed two new instrument towers on the shores of the recently drained South Lake, which will measure the weather, icequakes (using a seismometer), and the movement of the ice sheet (using a sensitive GPS). For more information about the tools our science team uses to track moving ice, visit the Polar Discovery tools page

View of a glacial lake from a helicopter

We also completed an hour-long helicopter survey of 20 nearby lakes. An aerial perspective gives you so much information that you can’t get from either the ground or from a satellite.  You can see immediately the water level in a lake, count the number of inflow channels, and see where the lake is draining (if at all).  The weather cleared during the survey and we had magnificent views of the glacial lakes – full ones, empty ones, and draining ones.

On July 16, we disassembled our carefully constructed home at South Lake and packed everything up for a move to North Lake.  Although much of the work will be similar to what we did at South Lake (removing existing instruments, assembling new ones, and field mapping by foot and helicopter), the research team is expecting to see different processes at work here. 

Last year, South Lake drained through a huge downstream channel, while North Lake gushed through a gaping hole called a moulin right in the center of the lake.  This year, new observations at South Lake confirmed that the water primarily drained through a huge crack that ran right through the lake. 

In the coming days, the science team is hoping to piece together this year’s story about North Lake, how it is similar and different from South Lake, how this knowledge can help to understand the thousands of glacial lakes that form on the ice sheet each summer, and what conclusions can be passed along to researchers modeling the global climate. Don’t forget to visit Polar Discovery to see daily photo essays!

Newly installed instrument towers at South Lake