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Ron Cowen
More books by Ron Cowen…
“Speed is measured as distance divided by time (miles per hour
or meters per second). For the speed of light to remain constant,
distance and time have to change.
Let’s go back now to Galileo’s shipboard experiment, using a
beam of light instead of a stone. On a boat that’s moving at a
uniform speed across the water, shine a flashlight down the
mast, and it will strike the deck at the base of the mast. The observer on the dock agrees with that. But from her vantage point
on the dock, if she had a precision measuring tool, she would
see the light travel a tiny extra distance, the distance the ship
has moved in the time it took the light to reach the bottom of
the mast.
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Authenticated
Download Date | 5/11/19 3:47 PM
12 • GRAVITY’S CENTURY
But the speed of light, which is measured in meters per
second—again, distance divided by time—is a constant. So if the
observer on the dock finds that light traveled an extra distance,
the only way its speed can remain constant is if the light also took
a longer time to travel.
Time, therefore, is not immutable. The duration of time—
measured as the ticks of a clock—is different for observers who
move at different speeds. Each sees the other’s clock slow down.
Even more strangely, distance is not absolute either; it appears to
contract in the direction of motion.”
― Gravity’s Century: From Einstein’s Eclipse to Images of Black Holes
or meters per second). For the speed of light to remain constant,
distance and time have to change.
Let’s go back now to Galileo’s shipboard experiment, using a
beam of light instead of a stone. On a boat that’s moving at a
uniform speed across the water, shine a flashlight down the
mast, and it will strike the deck at the base of the mast. The observer on the dock agrees with that. But from her vantage point
on the dock, if she had a precision measuring tool, she would
see the light travel a tiny extra distance, the distance the ship
has moved in the time it took the light to reach the bottom of
the mast.
Brought to you by | University of Wisconsin Madison Libraries
Authenticated
Download Date | 5/11/19 3:47 PM
12 • GRAVITY’S CENTURY
But the speed of light, which is measured in meters per
second—again, distance divided by time—is a constant. So if the
observer on the dock finds that light traveled an extra distance,
the only way its speed can remain constant is if the light also took
a longer time to travel.
Time, therefore, is not immutable. The duration of time—
measured as the ticks of a clock—is different for observers who
move at different speeds. Each sees the other’s clock slow down.
Even more strangely, distance is not absolute either; it appears to
contract in the direction of motion.”
― Gravity’s Century: From Einstein’s Eclipse to Images of Black Holes
“Speed is measured as distance divided by time (miles per hour
or meters per second). For the speed of light to remain constant,
distance and time have to change.
Let’s go back now to Galileo’s shipboard experiment, using a
beam of light instead of a stone. On a boat that’s moving at a
uniform speed across the water, shine a flashlight down the
mast, and it will strike the deck at the base of the mast.
The observer on the dock agrees with that. But from her vantage point
on the dock, if she had a precision measuring tool, she would
see the light travel a tiny extra distance, the distance the ship
has moved in the time it took the light to reach the bottom of
the mast. But the speed of light, which is measured in meters per
second—again, distance divided by time—is a constant. So if the
observer on the dock finds that light traveled an extra distance,
the only way its speed can remain constant is if the light also took
a longer time to travel.
Time, therefore, is not immutable. The duration of time—
measured as the ticks of a clock—is different for observers who
move at different speeds. Each sees the other’s clock slow down.
Even more strangely, distance is not absolute either; it appears to
contract in the direction of motion.”
― Gravity’s Century: From Einstein’s Eclipse to Images of Black Holes
or meters per second). For the speed of light to remain constant,
distance and time have to change.
Let’s go back now to Galileo’s shipboard experiment, using a
beam of light instead of a stone. On a boat that’s moving at a
uniform speed across the water, shine a flashlight down the
mast, and it will strike the deck at the base of the mast.
The observer on the dock agrees with that. But from her vantage point
on the dock, if she had a precision measuring tool, she would
see the light travel a tiny extra distance, the distance the ship
has moved in the time it took the light to reach the bottom of
the mast. But the speed of light, which is measured in meters per
second—again, distance divided by time—is a constant. So if the
observer on the dock finds that light traveled an extra distance,
the only way its speed can remain constant is if the light also took
a longer time to travel.
Time, therefore, is not immutable. The duration of time—
measured as the ticks of a clock—is different for observers who
move at different speeds. Each sees the other’s clock slow down.
Even more strangely, distance is not absolute either; it appears to
contract in the direction of motion.”
― Gravity’s Century: From Einstein’s Eclipse to Images of Black Holes
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