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Tides

Moon not only attracts the water. Gravity does not distinguish well as land, sea and air travel following the moon. Such We may not realize it but what does a fish at the bottom of the ocean tides?

Let's start by explaining the subject of the tides. If the Earth did not have satellite would be a more or less stable area, an earthquake here, a detachment there, but no major changes every few hours. The presence of the Moon, its gravity, it attracts whatever is on our planet change this situation. And as the force of gravity depends on the distance more strongly attracted to objects closer, those found in front of his face.

forces on variables from the Moon, (sometimes aided by the Sun) the surface is deformed by creating two bumps on the ends. The rigidity of the crust deformation limits but the ground can rise 30 to 50 centimeters .



do not see it because we have no references to perceive the change. The case of water is different. We have a reference since the lower ground displacement allows us to measure the rising tide. This rise depends on several factors. First the distance to the moon, which varies between 363,104 and 405,696 miles. Second orientation to the sun, which can add the effect and, last but not least, local geography that can enhance or diminish much height. In general, costs ocean tides are much higher than for smaller seas.



And the atmosphere? It also moves but here we have even less references. Like a fish in the background we study the surface problems. What we can do is to measure changes in pressure caused a wave. The effect is very small, just 100 microbars
, about 0.01 percent of the normal pressure on the surface. Compared the change in pressure at the bottom of the ocean can be from 0.1 or 0.2 percent. In both cases, the change is completely hidden from the variations caused by weather and only careful statistical analysis can discover. Even the thermal expansion caused by the sun at dawn, generates a pressure change 20 times more intense in the atmosphere

But although the results are different from the cause is the same. The moon draws us all and all alike. Sometimes as much as to dream of visiting.

Category: Physical

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The lunar dust problems

When the lunar probe Surveyor 1 landed on the moon had a first and urgent mission. Get a picture of your legs to see if it was sinking, if the surface had sufficient substance to support future Apollo missions.


How to calculate the depth of a pile of dust?. Or consistency. Or the weight that is able to resist from 384,000 kilometers away. In 1966 it was not a theoretical problem. Were little more than three years that the man pisase the Moon, the first extraterrestrial object to be stepped on and did not know very well how serious the field. Naturally multiplied all studies, estimates of the composition of the regolith covering its surface, simulations of the behavior of micrometeorites falling on the Moon and analysis of the action of its weak gravity and solar radiation to compact. The general opinion was to resist, but the final proof could only furnish a ship that posase and check the resistance of the ground. Surveyor mission was a success, but unfortunately it seems that some still have not heard .

Once stepped on, the lunar dust continued to occupy scientists for many reasons. One of the most curious was the smell. You could not smell the powder through the costumes but embedded in the surface and just pervasive. Later the astronauts breathed small particles dispersed in the air of his ship. According to the astronaut Charlie Duke moondust smelled of gunpowder. Obviously the composition

lunar dust is unlike the powder but rather, no one knows which caused the resemblance. Changes in temperature, desorption of some gases, maybe some chemical reactions, were combined to produce an odor that disappeared on reaching the ground. One of the many questions that still await us on the moon.


And is not the only surprise might be in store. Some preliminary studies indicate that the finer particles of lunar dust may pose a serious health problem. Here on Earth, fine particles of silica dust may cause serious diseases such as silicosis of miners. Even more fine particles appear to be dangerous in the dust. Small enough to cross the pulmonary barrier, its composition rich in iron may interfere with the functioning of hemoglobin and produce a slow suffocation similar to that caused by carbon monoxide.

Hopefully the problem is manageable as well as risks of radiation exposure we discussed in a previous post. Only further research can tell us if this fear disappeared as did the fear that the Apollo was over four meters deep in the lunar regolith.

Category: History of science

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Butterflies like grains of sand

say belongs to every cause an effect and every effect a cause. If it were that simple. In fact, the nature can be much more complicated. Sometimes the effect has little to do with the causes.

Take a simple grain of sand. If we let them fall one by one they form a small mountain. And the mountain is stable but only for a while. There comes a time when a single grain of sand is capable of causing an avalanche, an effect quite disproportionate. Physicists call it a non-linear response , an extremely interesting concept that should explain another day.

Returning to our "mountain" it is clear that the collapse has to do with the way it is constructed. Random falling grains of sand is formed a structure shaped "cone" defined by gravity. This cone is not perfect and appear at random, unstable areas both small and large. If a grain falls into these volatile areas causing a small avalanche. But over time they increase the volatile areas until the whole of our mountain of sand is full of them and get to touch each other. Then a single grain of sand can cause an avalanche that spread from one area to another to cause a significant collapse. Like contests dominoes falling, where one piece can bring down thousands of pieces carefully arranged. Of course nobody in nature "directs" the pieces, but the physical laws like gravity tend to produce the same effect. Understanding the behavior of a grain of sand hidden in a mound required careful computer simulations conducted by a team of physicists led by Per Bak .

Their findings have created a new branch of physics. The study of "self-organized criticality systems." The general idea is that, naturally, the system will accumulating instabilities. The longer time of accumulation, but grains of sand without a collapse, the more likely a more serious breakdown and its consequences. The familiar " butterfly effect "would be a similar example. Not that the butterfly has the energy needed to cause a storm thousands of miles but the system is at a point where minimal disturbance causes a substantial change in the result.

"This affects us in everyday life? can that much. It has been suggested that history or economics are full of similar processes that might respond to the same principle. Since the bubbles in the stock market or the price of housing certain historical events as World War I where a murder caused the slaughter of millions of people in four long years filled trenches. Such After studying these conditions could prevent the worst consequences. It's amazing what we learn from studying a humble pile of sand.


Category: Physical