This term weight may not sound as if it is a very scientific term as we are acquainted with it in our everyday use of the term. We buy our food in many cases by the pound, we gauge the growth of our children from their infancy by their weight, the farmer measures many of his crops by the tons he produces, and we ourselves are usually quite conscious of our own weight; whether normal, over, or under. Weight is such a familiar and common measurement that we often use it with little thought of what it actually implies or what our measurements of weight are based on. When conversing about weight or our weight we fail to realize that we are actually working with an important scientific principle. This of course does not detract from its usefulness to us in our daily life, but I think it would be interesting to look into the matter.
In a scientific sense we must be very definite about what we mean when we talk about weight. Essentially weight is the amount of force with which gravity pulls us or any object to the surface of the earth. Therefore scientists do not like to use the word weight because of its vague and uncertain meaning. The scientists would rather speak of the weight as the force of gravity which it really is and not something that is contained in the object itself. Weight is not a quality that is inherent in an object of itself, but in the terms of the scientists it is a force acting on it; which is variable, so that it cannot be said that a certain object weighs the same at all times. As the force of gravity changes, the weight of the object changes, even giving the possibility of a condition called weightlessness; which is a state in which an object weighs nothing. The quality of this object whereby it is said to contain a certain amount of matter is called its mass, not is weight; this mass of a given object does not change but remains the same unless the object is changed in some manner.
To give an illustration of this fact suppose you were to stand on your household scale to determine your weight. Note what your weight is, and now we will imagine a trip up into space with you standing on that scale. As you rise above the surface of the earth you will notice that the indicator of the scale is showing a slightly different amount, a lesser amount. At first the indicator will decrease very little because you are still near the earth. As you rise higher and higher the indicator keeps showing a smaller and smaller weight. If you could imagine such a trip so that you actually went up into the vast space around our planet, a space trip, you would reach a point where the scale would show zero. You would actually weigh nothing. You ask, how is this possible, I have not changed during this trip so I must really weigh the same now as when I left, but the scale says something different. Actually you know that the amount of matter that is contained in your body has not changed so that you do not become nothing as the scale indicates that your weight is nothing. This amount of matter of which you are composed is constant and in scientific terms is called your mass or how much of you there is; this is constant. Unfortunately we use the same units to measure both mass and weight so we are confused as to what we mean when we give a certain figure for a certain object.
Now that we see that weight of an object is not a constant thing but changes as its position changes in regard to the earth and is really a measurement of gravitational force on the object, not of something in the object itself, some questions will naturally arise. Does the person living in a high altitude, say Denver, actually get a different amount when he buys a pound of butter than I do when I buy that pound of butter in Grand Rapids? If the scales are not corrected for the higher or lower altitude, or distance from the center of the earth, the man in Denver would get a different amount, more in fact, than I would. For all practical purposes the difference is very little but there is a difference. In practice this problem is overcome in a number of ways. First, scales can be set for a certain locality so that they register “correct” weights. Another way is to use a different type of scale. A spring scale which measures weight by the distance an object can stretch the spring is a common scale but one that really measures gravitational force and not the mass of the object. This type of scale is subject to change as the scale is moved from place to place. We do have a type of scale that is free from this defect, it is called a balance scale. On this scale the weight of an object is balanced by an equal weight in or on the scale. When the scale is in balance we check the weight of the balance which is equal to the weight
of the object being weighed. No matter where this scale is taken, once in balance it will stay in balance if the object stays the same. As the gravitational force on the object being weighed changes the same change takes place on the balance in the scale. In accurate work this is the only scale that can he used since it is the only one giving true results. It really gives not weight but the mass of the object which is constant.
This phenomenon called weight has many practical uses. The most important is that it keeps us firmly planted on the surface of the earth. Although it may be granted that to the rocket launchers of today this is more of a hindrance, without this force or weight of an object things would not stay in place readily and would all have to be fastened to prevent movement. Such a thing as water flowing downhill is an example of the force of gravity or weight causing it to move so that this movement can be harnessed to give us water power. Our everyday activities are based on this characteristic of nature, weight. It has some seeming inconveniences also. We must be careful how we place objects lest they crush something under them or they fall from the place we put them because of this force that always pulls them toward the earth. When climbing we must be very careful lest we fall back to the earth with a force great enough o do us harm. In our work this thing called weight makes us weary because we must oppose it in all work at all times in our labors. All these things serve to impress upon our minds that we in this physical sense are part of the earth and we cannot escape it; our weight constantly pulls us toward it.
The cause of our weight, gravity, is not understood except as to what it can do. Man today has learned how to measure it, how it works in our solar system, how to make use of it to serve his aims, but he has not learned what it really is. This is the goal which many scientists seek, the discovery of the true nature of weight. Their object is of course to find a way to prevent its influence so that man can travel away from the earth with great freedom. The tremendous energy that is needed to break away from this force that holds us on the earth can be seen in the recent attempts to send rockets to the moon. Some eighty tons of fuel and machinery are needed to make a few pounds break away from the earth. These few attempts have not been successful and those rockets have fallen back to earth. Whether man will ever be successful in this attempt to escape the force of gravity is difficult to determine and certainly that man himself will travel away from this planet is still far in the future if at all.
We can see in our weight or in the force of gravity that God has so ordained that this earth is the place of man and has so ordered the workings of this planet so that we are firmly held here. The question as to the right or wrong of an attempt to leave this earth for space travel I shall leave to others to discuss.