How High Is The Moon?

How do we begin to measure the distance from the earth to the moon? One obvious thought is to measure the angle to the moon from two cities far apart at the same time, and construct a similar triangle, like Thales measuring the distance of the ship at sea. Unfortunately, the angle difference from two points a few hundred miles apart was too small to be measurable by the techniques in use at the time, so that method wouldn’t work.

Nevertheless, Greek astronomers, beginning with Aristarchus of Samos (310-230 B.C., approximately) came up with a clever method of finding the moon’s distance, by careful observation of a lunar eclipse, which happens when the earth shields the moon from the sun’s light.

For a Flash movie of a lunar eclipse, click here!

To better visualize a lunar eclipse, just imagine holding up a quarter (diameter one inch approximately) at the distance where it just blocks out the sun’s rays from one eye. Of course you shouldn’t try this---you’ll damage your eye! You can try it with the full moon, which happens to be the same apparent size in the sky as the sun. It turns out that the right distance is about nine feet away, or 108 inches. If the quarter is further away than that, it is not big enough to block out all the sunlight. If it is closer than 108 inches, it will totally block the sunlight from some small circular area, which gradually increases in size moving towards the quarter.

Thus the part of space where the sunlight is totally blocked is conical, like a long slowly tapering icecream cone, with the point 108 inches behind the quarter. Of course, this is surrounded by a fuzzier area, called the “penumbra”, where the sunlight is partially blocked. The fully shaded area is called the “umbra”. (This is Latin for shadow. Umbrella means little shadow in Italian.) If you tape a quarter to the end of a thin stick, and hold it in the sun appropriately, you can see these different shadow areas.

Question: If you used a dime instead of a quarter, how far from your eye would you have to hold it to just block the full moonlight from that eye? How do the different distances relate to the relative sizes of the dime and the quarter? Draw a diagram showing the two conical shadows.
Now imagine you’re out in space, some distance from the earth, looking at the earth’s shadow. (Of course, you could only really see it if you shot out a cloud of tiny particles and watched which of them glistened in the sunlight, and which were in the dark.)

Clearly, the earth’s shadow must be conical, just like that from the quarter. And it must also be similar to the quarter’s in the technical sense---it must be 108 earth diameters long! That is because the point of the cone is the furthest point at which the earth can block all the sunlight, and the ratio of that distance to the diameter is determined by the angular size of the sun being blocked. This means the cone is 108 earth diameters long, the far point 864,000 miles from earth.

Now, during a total lunar eclipse the moon moves into this cone of darkness. Even when the moon is completely inside the shadow, it can still be dimly seen, because of light scattered by the earth’s atmosphere. By observing the moon carefully during the eclipse, and seeing how the earth’s shadow fell on it, the Greeks found that the diameter of the earth’s conical shadow at the distance of the moon was about two-and-a-half times the moon’s own diameter.

Note: It is possible to check this estimate either from a photograph of the moon entering the earth’s shadow, or, better, by actual observation of a lunar eclipse.

Question: At this point the Greeks knew the size of the earth (approximately a sphere 8,000 miles in diameter) and therefore the size of the earth’s conical shadow (length 108 times 8,000 miles). They knew that when the moon passed through the shadow, the shadow diameter at that distance was two and a half times the moon’s diameter. Was that enough information to figure out how far away the moon was?

Well, it did tell them the moon was no further away than 108x8,000 = 864,000 miles, otherwise the moon wouldn’t pass through the earth’s shadow at all! But from what we’ve said so far, it could be a tiny moon almost 864,000 miles away, passing through that last bit of shadow near the point. However, such a tiny moon could never cause a solar eclipse. In fact, as the Greeks well knew, the moon is the same apparent size in the sky as the sun. This is the crucial extra fact they used to nail down the moon’s distance from earth.

They solved the problem using geometry, constructing the figure below. In this figure, the fact that the moon and the sun have the same apparent size in the sky means that the angle ECD is the same as the angle EAF. Notice now that the length FE is the diameter of the earth’s shadow at the distance of the moon, and the length ED is the diameter of the moon.

The Greeks found by observation of the lunar eclipse that the ratio of FE to ED was 2.5 to 1, so looking at the similar isosceles triangles FAE and DCE, we deduce that AE is 2.5 times as long as EC, from which AC is 3.5 times as long as EC. But they knew that AC must be 108 earth diameters in length, and taking the earth’s diameter to be 8,000 miles, the furthest point of the conical shadow, A, is 864,000 miles from earth.

From the above argument, this is 3.5 times further away than the moon is, so the distance to the moon is 864,000/3.5 miles, about 240,000 miles. This is within a few percent of the right figure. The biggest source of error is likely the estimate of the ratio of the moon’s size to that of the earth’s shadow as it passes through.

Recognising High Blood Pressure And The Damage It Does

High blood pressure is a very serious disease. It can cause damage to your vital organs and in the worst cases can be fatal. Sufferers of high blood pressure often do not show any symptoms and when the symptoms do show, the damage has often already occurred. Therefore, the best way to determine whether you have high blood pressure or not is to go and see a trained doctor and get it checked out.

Blood pressure is said to be normal if it is 140 over 85. However, it can differ between different races and geographic locations. Generally speaking blood pressure above 140 over 85 is said to be high. A few degrees above normal may not cause any significant problems but a signficant increase can be dangerous.

As I mentioned above high blood pressure does not always display symptoms. However, there are a number of signs you can look out for. Regular migraines are also a sign of high blood pressure. If you find yourself breathless after a little exertion this is another sign that you may have high blood pressure, particularly if this didn't seem to happen previously. A third sign is increased nose bleeds or increased bleeding from any other area of the body. Additional signs of high blood pressure can include hyperventiliation and tension. If you notice any of these signs, particularly an increased occurence of any particular sign e.g. increased nosebleeds, you should seek further advice from your doctor immediately.

If it is not treated high blood pressure can cause damage to multiple areas of your body. Your eyes receive blood through the optic arteries and if these are damaged by high blood pressure then your vision may be impaired. Brain damage is another possible outcome of high blood pressure. The brain requires oxygen and nutrition which is supplied in the blood stream. If this supply is impaired by high blood pressure it can lead to a mini-stroke, a full stroke and even dementia in old age. High blood pressure can also cause serious damage to the heart including heart attacks and heart failure.

As you can see high blood pressure can easily go unnoticed and potentially cause a lot of damage to your body. However, if it is identified early enough then you are likely to never experience any of the consequences mentioned in this article. It is advisable to go and see your doctor immediately and be tested for high blood pressure. As long as it is diagnosed early enough it can be managed using a combination of medication, diet and exerc

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Don't Forget The High Blood Pressure Checkups: It's A Serious Thing

Don't Forget The High Blood Pressure Checkups: It's A Serious Thing

Sometimes, changing your lifestyle into a better one is not enough. Lowering the hypertension might suppose a drug treatment too. Based on the fact that every person is different and the high blood pressure affects each one in a particular manner, the physician will prescribe the right drugs and dosage according to each case.

The status of your health might be affected by the high blood pressure and the worrying aspect is that it has no visible symptoms. Checking your health frequently by performing tests and talking to your personal physician regularly about the health problems you might have is the only way you can trace hypertension. Once you know you have it, immediate measures must be taken because hypertension might cause you serious problems, even fatal ones, if is not taken care of.

The elements causing high blood pressure are various, and strongly related to modern times. Today we find ourselves in many stressful situations and we are the victims of sedentary and poor diets. The personal physician is the right person to guide you on the way of escaping this wrong way of life and help you control the high blood pressure.

Sometimes, changing your lifestyle into a better one is not enough. Lowering the hypertension might suppose a drug treatment too. Based on the fact that every person is different and the high blood pressure affects each one in a particular manner, the physician will prescribe the right drugs and dosage according to each case.

The medicated treatment can be avoided though by staying away from the elements that can cause it from the fist time. You can begin with being more active. Exercise at least two times a week and you will make your body stronger and healthier. The blood circulation will improve significantly and the high blood pressure can be controlled and decreased.

The food you eat should be low in cholesterol and if you choose it, you will be able to keep your arteries in shape. But do not forget that healing comes form inside too. Try to manage the stressful situations in your life and see the bright side of your life. Be calm and optimistic and your blood pressure will be also under control.

When the situation of high blood pressure is not up to you because you have inherited it, the things we can do about it are regular visits to the doctor to control the levels of the blood pressure and a healthy way of life. Do not think that if you are diagnosed with high blood pressure you are in deathly danger. Take it as a signal of alarm, a sign of a need for a complete turn in your life. If you realize its' seriousness and stop for a minute to think about it, choose the hard way of life, the healthy one. High blood pressure checkups can help you be a winner in the confrontation with this affection.

Author: Clive Jenkins Clive

High Blood Pressure And Hypertension The Same Thing

High Blood Pressure And Hypertension: The Same Thing

High blood pressure, which is known medically as hypertension, causes the heart to work too hard because it has become more difficult to force blood through the circulatory system. Over time, this can result in severe damage to the heart's muscle and tissue. It also contributes to hardening of the arteries, or atherosclerosis.

Someone with hypertension or high blood pressure has a higher risk of experiencing a heart attack or stroke. Furthermore, elevated blood pressure can lead to kidney disease, severe eye damage and loss of vision.

In the United States, almost 70 percent of people over the age of 65 have high blood pressure. It's also common for people of all ages who are overweight.

A number of risk factors are widely known to contribute to high blood pressure, although the exact causes are still somewhat mysterious. People who don't get much exercise and eat poor diets are likely to get high blood pressure. Heredity also seems to play a role.

High blood pressure can often be controlled with medications, but lifestyle changes are the best "prescription" for long term overall health.

How High To Pull The Foot Up In Running?

HOW HIGH TO PULL THE FOOT UP IN RUNNING?

To know the answer to this question, one has to understand the purpose of the "pull" in running.

In the Pose Method of Running, the pull is the last element of the technique that allows for the most efficient transition from one foot to the other. That's the purpose, now let's elaborate.

Running is nothing but "change of support". If all we need to do is change our support, then the ultimate goal is to do that action with the least possible effort. Actively working just one group of muscles - the hamstrings - fits the purpose. So to run is to pull your feet up with hamstrings, while leaning forward. What for? To change support to continue to move forward.

So how high and how intense is the pull? It should only be high enough and strong enough to break contact with the ground. Due to inertia the foot will naturally come up higher, if you're running at a higher speed. And it will travel lower at a slower pace.

You will notice that putting less intentional effort into pulling your feet up will help you do it correctly, by utilizing the hamstrings only. You will also notice that such an important thing as high cadence is easier to achieve, if you don't pull your feet all the way up.

The general rule is - you're better off "under-doing" it, than "over-doing" it. If you pull too high and too hard you will waste energy and will tire your hamstrings. The exaggerated motion of the pull, demonstrated in the running drills, is strictly for learning purposes, to help your body learn better patterns of movement required for running.

Article by Dr. Nicholas Romanov
Composed by L. Romanov