Generating Extremes: Temperatures

By Kenneth Freeman

‘Extreme’ is a relative word: an Antarctic -30°C may seem extremely cold to you or me, but it’s fairly standard for an emperor penguin. In the laboratory, extremes can be far more dramatic: we approach the absolute limits of physical properties like temperature, reaching levels that can’t easily be comprehended. At these farthest limits we can explore exciting science which broadens our understanding of the fundamental forces in nature and provides insight that can lead to new technologies.

There are lots of ways to take a physical object to the extreme: examples include extremes of temperature, extremes of size (very big or very small), and extremes of pressure. These three properties – temperature, size, and pressure – are quite familiar from our everyday lives. Hot and cold, big and small are simple enough; pressure may be less intuitive initially, but doesn’t require much thought to understand its effects.

In the sciences, we can consider lots of other extremes too: for example concentration, magnetic field and time (e.g. looking at incredibly fast processes). We can also combine these different extremes to create a multitude of extreme environments. Here we’ll look at the methods used to produce these conditions in the lab, and how they compare to the extremes we see in nature.

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Extremophiles: Life at Extreme Conditions

By Katherine Brown

Extremophiles are defined as organisms that may survive comfortably in environments that would be impossible for a human to survive in – whether this be extremes of temperature, pressure, pH, salinity or radiation. The word “extremophile” is a very loose definition, and is better treated as an umbrella term, from where you must specify in which extreme environment the organism survives. To best understand life at extreme conditions, it is perhaps best to discuss the limiting factors on life.

It’s a commonly known fact that the human body operates at 37°C, and in fact all mammals have a body temperature of between 36 and 40°C. Reptiles and fish, being cold blooded, have lower body temperatures than mammals, whereas for birds it is slightly higher. All told, most animals are found to have body temperatures in the range of 8 to 48°C. So what is it that sets this limit?

The Grand Prismatic Spring in Yellowstone National Park. Waters in the middle of the spring can reach almost 90°C. The bands of colour are a result of different thermophilic bacteria that live in the spring, sticking to rings where the temperature is best for them. These thermophiles produce different levels of carotenoids, which are similar to the chlorophyll that gives plants their green colour.

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