Though some dermatologists believe showers can be better for your skin by helping it to retain some naturally occurring oils, baths are still symbolic of relaxation. Luxuriating in standing water provides a break in routine and allows people to unwind.
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Now, scientists may have found evidence that there’s a more substantial benefit to bathing: It might actually help alleviate depression.
In a study [PDF] out of Freiburg University in Germany and published by the preprint repository bioRxiv, 45 subjects with moderate to severe depression as measured by the Hamilton Depression Rating Scale (HAM-D) were instructed to either exercise for 45 minutes twice each week or take 30-minute hot baths (at 104°F) and then relax with hot water bottles and a warm blanket for 20 minutes twice a week. The subjects were then retested with HAM-D after eight weeks. Those who bathed reported a six-point drop in their score, which averaged 21.7 on a scale of 1 to 50 at the outset. Exercise patients saw only a three-point drop.
There are some significant caveats to this study, which has not yet been peer-reviewed. In addition to the sample size being small, 13 of the 23 people assigned to the exercise group failed to complete the study because they were unable or unwilling to continue physical activity.
Some researchers suggest that soaking can address one’s mood by helping to normalize a person’s body temperature and circadian rhythms, which help regulate the sleep-wake cycle. (The hot water bottles provided a continued spike in body temperature.) A 2017 study led by the University of Madison-Wisconsin demonstrated that regularly raising a individual’s core temperature to 101.3°F led to a 4.27-point reduction in the HAM-D score after six weeks (though the findings from the small-scale study were controversial).
While it’s too early to conclude whether hot baths should be a prescription for depression, or that their benefits are equal to those of exercise, they have almost no side effects and are likely to result in more adherence than an exercise regimen.
It is often said that sound doesn’t travel in space. And it is true … in empty space. Sound is pressure waves, that is, propagating changes in pressure. In the absence of pressure, there can be no pressure waves, so there is no sound.
But space is is not completely empty and not completely devoid of pressure. Hence, it carries sound. But not in a manner that would match our everyday experience.
For instance, if you were to put a speaker in interstellar space, its membrane may be moving back and forth, but it would be exceedingly rare for it to hit even a single atom or molecule. Hence, it would fail to transfer any noticeable sound energy to the thin interstellar medium. Even the somewhat denser interplanetary medium is too rarefied for sound to transfer efficiently from human scale objects; this is why astronauts cannot yell to each other during spacewalks. And just as it is impossible to transfer normal sound energy to this medium, it will also not transmit it efficiently, since its atoms and molecules are too far apart, and they just don’t bounce into each other that often. Any “normal” sound is attenuated to nothingness.
However, if you were to make your speaker a million times bigger, and let its membrane move a million times more slowly, it would be able to transfer sound energy more efficiently even to that thin medium. And that energy would propagate in the form of (tiny) changes in the (already very tiny) pressure of the interstellar medium, i.e., it would be sound.
So yes, sound can travel in the intergalactic, interstellar, interplanetary medium, and very, very low frequency sound (many octaves below anything you could possibly hear) plays an important role in the formation of structures (galaxies, solar systems). In fact, this is the mechanism through which a contracting cloud of gas can shed its excess kinetic energy and turn into something compact, such as a star.
How fast do such sounds travel, you ask? Why, there is no set speed. The general rule is that for a so-called perfect fluid (a medium that is characterized by its density and pressure, but has no viscosity or stresses) the square of the speed of sound is the ratio of the medium’s pressure to its energy density. The speed of sound, therefore, can be anything between 0 (for a pressureless medium, which does not carry sound) to the speed of light divided by the square root of three (for a very hot, so-called ultrarelativistic gas).
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The scientific process of carbon dating has been used to determine the age of Ötzi the Iceman, seeds found in King Tutankhamun’s tomb, and many other archaeological finds under 60,000 years old. However, as SciShow points out in a recent episode, the excessive use of fossil fuels is making that method less reliable.
Carbon dating, also called radiocarbon or C-14 dating, involves analyzing the ratio of two isotopes of carbon: C-14 (a radioactive form of carbon that decays over time) and C-12 (a more stable form). By analyzing that ratio in a given object compared to a living organism, archaeologists, paleontologists, and other scientists can get a pretty clear idea of how old that first object is. However, as more and more fossil fuels are burned, more carbon dioxide is released into the environment. In turn, this releases more of another isotope, called C-12, which changes the ratio of carbon isotopes in the atmosphere and skews the carbon dating analysis. This phenomenon is called the Suess effect, and it’s been well-documented since the ‘70s. SciShow notes that the atmospheric carbon ratio has changed in the past, but it wasn’t anything drastic.
A recent study published in Nature Communications demonstrates the concept. Writing in The Conversation, the study authors suggest that volcanoes “can lie about their age.” Ancient volcanic eruptions can be dated by comparing the “wiggly trace” of C-14 found in trees killed in the eruption to the reference “wiggle” of C-14 in the atmosphere. (This process is actually called wiggle-match dating.) But this method “is not valid if carbon dioxide gas from the volcano is affecting a tree’s version of the wiggle,” researchers write.
According to another paper cited by SciShow, we’re adding so much C-12 to the atmosphere at the current rate of fossil fuel usage that by 2050 brand-new materials will seem like they’re 1000 years old. Some scientists have suggested that levels of C-13 (a more stable isotope) be taken into account while doing carbon dating, but that’s only a stopgap measure. The real challenge will be to reduce our dependence on fossil fuels.
For more on how radiocarbon dating is becoming less predictable, check out SciShow’s video below.
This content was originally published here.