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Every teenager has stayed up late, woken up early, regretted their decision, end then slept extra long the next night. Can a person really catch up on sleep? Numerous studies have been conducted on the subject, and what is the prevailing hypothesis is that there are two systems dealing with sleep, a circadian process and a sleep homeostatic process. The circadian process is a rhythm of sleepiness and alertness over a twenty four hour period. This clock is related to the amount of light received by the eyes and can change when stimulus to the eyes is removed. This cycle is controlled by the suprachiasmatic nucleus in the hypothalamus in the brain. This region of the brain is affected by light and stimulus to the eyes, and it is what causes the circadian process. the interaction of this part of the brain results in changes in hormone levels in the body, promoting either sleepiness or alertness. The sleep homeostatic process is basically a pressure that builds up during the day that promotes sleep. the pressure dissipates during sleep. Being awake for days can build this process up and cause a difference in brain wave patterns when sleep finally comes. However, brain patterns return to normal after only a night or two of sleep, meaning that a lack of sleep happening as a shock isn't known to have lasting effects yet. Chronic sleep restriction and sleeping disorders are much different. Getting less sleep than is necessary on a regular basis can cause negative effects to take much longer to wear off and some effects may not be completely reversible. The problem with studying the effects of chronic sleep restriction is that it is difficult to find willing participants for studies and difficult to produce reliable studies because of lifestyle changes caused by sleep restriction. The physics of all this lies in the fact that all of these effects are caused by electrical and chemical reactions in the brain and body. Also, this was caused by physics. Something as simple as the amount of light entering the eyes can affect the sleep cycles of millions of people. It is important to get a full night's sleep every night, but one night every blue moon won't make a difference in your life. Chronic sleep restriction is the thing that can cause serious problems to the brain, body, and lifestyle. I'm going to bed.
Water is strange. Unlike most compounds, its solid form is (normally) less dense, and of a larger volume than its liquid form. Because of this, its very difficult to compress water, because normally there isn't really anything to compress it into. But the story of ice is a bit different from the snow and hail we see falling outside of our windows during these winter months. In fact, ice has many different forms, depending on the conditions it forms in. The ice we commonly know is called Ih - a common ice type with a hexagonal structure. But as you can see from the picture, there are many different types of ice. Ic is also a (relatively speaking) common ice type, with a cubic structure that can be present in the upper atmosphere. In total there are 15 different types of ice, all forming at different pressures and temperatures, all with different crystal structures, densities, and electrical properties. For example, while water is hard to compress, when put under great enough pressure at normal temperatures, can form into ice IV (not pictured), a denser form of ice. While most variations are just density and structure based, certain forms (like ice XI) have ferroelectric properties, which is something I looked up and failed to understand, but it sounded interesting. And noticing the lower pressures, below ~1 kPa (about 1/100 of normal sea pressure), liquid water fails to exist, and water vapour will undergo deposition straight into ice below this point. As we head into winter, it's interesting to note the complexities of such a common substance. It can take on many forms with many properties, and I think that's pretty cool.