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dilation effect states that clocks moving relative to an observer are measured by

that observer to run more slowly (as compared to clocks at rest). Not only time

intervals are different in different reference frames. Space intervals – lengths

and distances – are different as well: the length of an object is measured to be

shorter when it is moving relative to the observer than when it is at rest. Not

only length and time intervals have shown to be relative. Mass, another basic

mechanical quantity, is measured to increase as its speed increases. Another

basic result of the special relativity is that the speed of an object cannot equal or

exceed the speed of light. It is perhaps easiest to see it from the mass-increase

formula, m = m

0

/ ¥1 – v

2

/ c

2

. As an object is accelerated to greater and greater

speeds, its mass becomes larger and larger. Indeed, if v were to equal c, the

denominator in this equation would be zero and the mass m would become

infinite. To accelerate an object up to v = c would thus require infinite energy,

and so is not possible. The fact that a steady net force applied to an object

contributes to increasing its speed, mass and energy has led to a crucial part of

Einstein’s theory, to the idea that mass is a form of energy. The relation

E = mc

2

(energy equals mass times the square of the speed of light) is now

believed to apply to all processes, although the changes are often too small to

measure.

(6;…)

A great many experiments have been performed to test the predictions of

the special theory of relativity. Within experimental error, no contradictions

have been found. Scientists have therefore accepted relativity as an accurate

description of nature. At speeds much less than the speed of light (v << c), the

relativistic formulas reduce to the old classical ones. Relativity thus does not

contradict classical mechanics. Rather, it is a more general theory, of which

classical mechanics is now considered to be a limiting case. The importance of

relativity is not simply that it gives more accurate results, especially at very

35

dilation effect states that clocks moving relative to an observer are measured by that observer to run more slowly (as compared to clocks at rest). Not only time intervals are different in different reference frames. Space intervals – lengths and distances – are different as well: the length of an object is measured to be shorter when it is moving relative to the observer than when it is at rest. Not only length and time intervals have shown to be relative. Mass, another basic mechanical quantity, is measured to increase as its speed increases. Another basic result of the special relativity is that the speed of an object cannot equal or exceed the speed of light. It is perhaps easiest to see it from the mass-increase formula, m = m0 / �1 – v2 / c2. As an object is accelerated to greater and greater speeds, its mass becomes larger and larger. Indeed, if v were to equal c, the denominator in this equation would be zero and the mass m would become infinite. To accelerate an object up to v = c would thus require infinite energy, and so is not possible. The fact that a steady net force applied to an object contributes to increasing its speed, mass and energy has led to a crucial part of Einstein’s theory, to the idea that mass is a form of energy. The relation E = mc2 (energy equals mass times the square of the speed of light) is now believed to apply to all processes, although the changes are often too small to measure. (6;…) A great many experiments have been performed to test the predictions of the special theory of relativity. Within experimental error, no contradictions have been found. Scientists have therefore accepted relativity as an accurate description of nature. At speeds much less than the speed of light (v << c), the relativistic formulas reduce to the old classical ones. Relativity thus does not contradict classical mechanics. Rather, it is a more general theory, of which classical mechanics is now considered to be a limiting case. The importance of relativity is not simply that it gives more accurate results, especially at very 35

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