# Английский язык. Ч.3 (Tests 10,11,12). Ильичева Н.А - 10 стр.

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E. In a reference frame which was not at rest, extra terms would have to be
added to take into account the relative velocity.
F. Briefly, what they did was measure the difference in the speed of light in
different directions.
With the introduction of the theory of electromagnetism in the last half of the
nineteenth century it was assumed that light would have a different speed in
different frames of reference. Maxwell’s equations predicted the speed of light
to be c = 3
.
10
8
m/s. This seemed to imply there must be some special reference
frame where c would have this value (1;…).
Waves travel on water and along ropes or strings, and sound waves travel in
air and other materials. It was natural for nineteenth-century physicists to think
that light must travel in some medium (2;…). Therefore, another medium was
postulated, the ether. The ether was not only transparent, but because of
difficulty in detecting it, was assumed to have zero density.
Scientists soon set out to determine the speed of the Earth relative to this
absolute frame, whatever it might be. A number of clever experiments were
designed. The most direct were performed by A.A. Michelson and E.W. Morley
in the 1880s (3;…). The experiments thus hoped to find an absolute reference
frame, one that could be considered to be at rest.
One of the possibilities nineteenth-century scientists considered was that the
ether is fixed relative to the Sun, for even Newton had taken the Sun as the
centre of the universe. If this were the case (there was no guarantee, of course),
the Earth’s speed of about 3
.
10
4
m/s in its orbit around the Sun would produce a
change of 1 part in 10
4
in the speed of light (3
.
10
8
m/s). Direct measurement of
the speed of light to this accuracy was not possible. But A.A. Michelson, later
with the help of E.W. Morley, was able to use his interferometer to measure the
difference in the speed of light to this accuracy (4;…). They expected to find a
difference depending on the orientation of their apparatus with respect to the
10
   E. In a reference frame which was not at rest, extra terms would have to be
added to take into account the relative velocity.
F. Briefly, what they did was measure the difference in the speed of light in
different directions.

With the introduction of the theory of electromagnetism in the last half of the
nineteenth century it was assumed that light would have a different speed in
different frames of reference. Maxwell’s equations predicted the speed of light
to be c = 3 . 108 m/s. This seemed to imply there must be some special reference
frame where c would have this value (1;…).
Waves travel on water and along ropes or strings, and sound waves travel in
air and other materials. It was natural for nineteenth-century physicists to think
that light must travel in some medium (2;…). Therefore, another medium was
postulated, the ether. The ether was not only transparent, but because of
difficulty in detecting it, was assumed to have zero density.
Scientists soon set out to determine the speed of the Earth relative to this
absolute frame, whatever it might be. A number of clever experiments were
designed. The most direct were performed by A.A. Michelson and E.W. Morley
in the 1880s (3;…). The experiments thus hoped to find an absolute reference
frame, one that could be considered to be at rest.
One of the possibilities nineteenth-century scientists considered was that the
ether is fixed relative to the Sun, for even Newton had taken the Sun as the
centre of the universe. If this were the case (there was no guarantee, of course),
the Earth’s speed of about 3 . 104 m/s in its orbit around the Sun would produce a
change of 1 part in 104 in the speed of light (3 . 108 m/s). Direct measurement of
the speed of light to this accuracy was not possible. But A.A. Michelson, later
with the help of E.W. Morley, was able to use his interferometer to measure the
difference in the speed of light to this accuracy (4;…). They expected to find a
difference depending on the orientation of their apparatus with respect to the
10