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Time and measures of time Bego, Brogi, Dolfi, Tonola. TIME & SPACE. Time for Sir Isaac Newton. Newton (1643-1727) believed that there were two different types of time: time itself, and time measured by man.
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Time and measures of time Bego, Brogi, Dolfi, Tonola TIME & SPACE
Time for Sir Isaac Newton • Newton (1643-1727) believed that there were two different types of time: time itself, and time measured by man. • Absolute time was time as it would be for God, who was omnipresent and had the function of an absolutely regular, universal clock, that is, one whose intervals are always of the same duration at every time, in every place, for each subject.
Albert Einstein (1879-1955) He was the first who excluded God from the cosmic association of physicists. The distinction between absolute and relative time becomes impossible, since time becomes a quantity measured by a Human observer. In reality all time measurements are relative to actual observers located at particular points in space and time, having their own clocks and moving at specific velocities and acceleration. This is a summary of the theory of relativity.
The special relativityIt results from two postulates: • The speed of light is the same for all observers, no matter what their relative speeds. • The laws of physics are the same in any inertial (= non-accelerated) frame of reference. This means that the laws of physics observed by a hypotetical observer travelling with a relativistic particle must be the same as those observed by an observe who is stationary in the laboratory.
The first postulate is the crucial idea that led Einstein to formulate his theory. It means we can define a quantity which is a fundamental constant of nature: the speed of light. • The second postulate states that we can formulate rules of nature which don’t depend on our particular observation of the situation. ATTENTION: this doesn’t mean that things behave in the same way on Earth and in space! An observer on the surface of the Earth is affected by the Earth’s gravity, but it means that the effect of a force on an object is the same independently of what causes the force and also of where the object is or what its speed is.
Consequences of Special Relativity • The time lapse between two variants is not invariant from one observer to another, but is dependent on the relative speeds of the observers’ reference frames (Lorentz transformation equations). • Two events that occur simultaneously in different places in one frame of reference may happen at different times in another frame of reference (lack of simultaneity). • The dimensions ( for example lenght) of an object as measured by one observer may differ from the results of measurements of the same object made by another observer (Lorentz transformation equation).
Twins Theory • Einstein supposed that we had two twins: one stayed on the Earth, the other travelled at the speed of light. When the second came back to the Earth he was younger than the first. This theory is connected to the second consequence of the Special Relativity (lack of simultaneity).