I posts this article
today, 18th April 2017. It is exactly (plus minus leap year) 62
years since the death of Albert Einstein on 18th April 1955. I can’t
wait to watch National Geographic Series entitled Genius about the life of Einstein! (premier 25th April
2017)
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German-born physicist of
Swiss parentage, Albert Einstein (1879-1955) became a naturalised American in
1935, after leaving Hitler’s Germany to avoid persecution as a Jew. After an
unpromising start to his academic career, at one time declaring, “I have given up the ambition ever to get to
a university,” he accepted a job in Bern patent office, where he conceived
the theories of general and special relativity which were to found modern
physics. Einstein was also politically active, both in the cause of world peace
and Zionism. In 1952 he was offered the presidency of Israel but declined,
claiming he was too naïve in politics. On the relation between his scientific
and political interests he once said, “Equations
are more important to me, because politics is for the present, but an equation
is something for eternity.”
The philosophical import
of Einstein’s work is enormous. His theory of relativity assigns an
unprecedented importance to the role of the observer in his description of the
physical world, threatening the received notions of space and time, as found in
Isaac Newton, John Locke, Immanuel Kant and others. The central aspect of Einstein’s works is that the speed of light is
constant. It gives rise to the two most famous ideas of relativity physics:
the equivalence of mass and energy expressed in the equation E = mc2
(where E = energy, m = mass and c = the constant speed of light), and the law
that nothing can travel faster than the speed of light.
These have at least two philosophically
important consequences. First, it follows from relativity that one cannot speak of an event occurring at
precisely the same time for different observers. Each observer’s time frame
is relative to himself. Imagine an observatory in Jupiter looking at an
observatory on Earth. In each an astronomer looks through his eyeglass at the
other at, we might suppose, exactly the same time. Since light takes 35 minutes
to travel from Jupiter to Earth, the event on Jupiter in which the astronomer
looks through his telescope must have taken place 35 minutes before the
astronomer on Earth observes the event. Equally, the same applies to the
astronomer on Jupiter: as he observes the astronomer on Earth he is observing
an event that took place 35 minutes prior to his own time frame. It is tempting
to think there is some absolute position in which the two events could be
observed as simultaneous, but this is exactly the possibility ruled out by
relativity theory. Space and time are not independent dimensions, but form a
four-dimensional unity, space-time, in which every event can only be recorded
relative to a local time-frame.
The second philosophically
interesting consequence of relativity is that although the speed of light is constant, its frequency (the number
of waves of light per second) varies
closer to massive objects like planets. This means time appears to run
slower near a massive body than farther away. In 1962 physicists confirmed this
prediction by using two very accurate clocks, one at the base and one at the
top of a water tower. The clock at the base was found to run slower than the
other.
This gives rise to the
famous ‘twin paradox.’ Suppose one twin goes for a lengthy journey into space
while the other stays on Earth. When he returns he would appear to be much
younger than his twin. The paradox arises from the assumption of an absolute
time frame. The relativity thesis means that each body carries around its own
personal time scale which does not, in general, agree with the time scale of
other entities. Relative to each other, 50 years near a massive gravitational
body is a shorter duration than 50 years far away from massive body. Thus while
50 years might have passed on Earth the space travelling twin might find he has
only been away in space for 35 years. The exact difference depends on the
gravitational influences on the two twins throughout their lives.
The philosophical
consequences of Einstein’s relativity theory, like the empirical consequences,
are yet to be fully known. Issues about time-travel, the passage or ‘flow’ of
time, the asymmetry between past and future and between cause and effect, are
all issues that require an understanding of Einstein’s momentous work.
[Summarized from Philosophy 100 Essential Thinkers by
Philip Stokes, 2012.]
Lord, Give
Us Today Our Daily Idea(s)
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