A submarine communications cable is a cable laid on the sea bed between land-based stations to carry telecommunication signals across stretches of ocean. The first submarine communications cables, laid in the 1850s, carried telegraphy traffic. Subsequent generations of cables carried telephone traffic, then data communications traffic. Modern cables use optical fiber technology to carry digital data, which includes telephone, Internet and private data traffic. 

Modern cables are typically about 1 inch (25 mm) in diameter and weigh around 2.5 tons per mile (1.4 tonnes per km) for the deep-sea sections which comprise the majority of the run, although larger and heavier cables are used for shallow-water sections near shore. Submarine cables connected all the world's continents except Antarctica when Java was connected to Darwin, Northern Territory, Australia in 1871 in anticipation of the completion of the Australian Overland Telegraph Line in 1872 connecting to Adelaide, South Australia and thence to the rest of Australia. 

After William Cooke and Charles Wheatstone had introduced their working telegraph in 1839, the idea of a submarine line across the Atlantic Ocean began to be thought of as a possible triumph of the future. Samuel Morse proclaimed his faith in it as early as 1840, and in 1842, he submerged a wire, insulated with tarred hemp and India rubber, in the water of New York Harbor, and telegraphed through it. The following autumn, Wheatstone performed a similar experiment in Swansea Bay. A good insulator to cover the wire and prevent the electric current from leaking into the water was necessary for the success of a long submarine line. India rubber had been tried by Moritz von Jacobi, the Prussian electrical engineer, as far back as the early 19th century.
When were the first submarine communication cables placed?
Where do they lay?
What kind of communications did they initially carry?
What technology do they currently use?
Can they provide internet service?
When was the telegraph first introduced?
By whom?
Did Samuel Morse believe in a oceanic submarine line?
Crossing which ocean?
What year did he express his support in the project?
What year did he perform a test of his own?
Which body of water did he use?
Who else performed a similar test?
Where?
How wide are modern cables?
Do they reach all of the continents?
Which one is excluded?
Which continent was the most recent to be connected?
What year did it join?
Where did it connect?
1850s
The first submarine communications cables, laid in the 1850s, carried telegraphy traffic.
on the sea bed
 submarine communications cable is a cable laid on the sea bed between land-based stations to carry telecommunication signals across stretches of ocean. 
telegraphy
The first submarine communications cables, laid in the 1850s, carried telegraphy traffic
optical fiber
Modern cables use optical fiber technology to carry digital data, 
yes
Modern cables use optical fiber technology to carry digital data, which includes telephone, Internet and private data traffic. 

1839
After William Cooke and Charles Wheatstone had introduced their working telegraph in 1839, 
William Cooke and Charles Wheatstone
After William Cooke and Charles Wheatstone had introduced their working telegraph in 1839, 
yes
 Samuel Morse proclaimed his faith in it as early as 1840,
the Atlantic
the idea of a submarine line across the Atlantic Ocean began to be thought of as a possible triumph of the future. Samuel Morse proclaimed his faith in it as early as 1840, 
1840
Samuel Morse proclaimed his faith in it as early as 1840,
1842
in 1842, he submerged a wire, insulated with tarred hemp and India rubber, 
New York Harbor,
n the water of New York Harbor,
Wheatstone
 Wheatstone performed a similar experiment in Swansea Bay. 
Swansea Bay.
Wheatstone performed a similar experiment in Swansea Bay.
1 inch
Modern cables are typically about 1 inch (25 mm) in diamete
no
 Submarine cables connected all the world's continents except Antarctica when Java was 
Antarctica
Submarine cables connected all the world's continents except Antarctica 
Australia.
 Submarine cables connected all the world's continents except Antarctica when Java was connected to Darwin, Northern Territory, Australia in 1871 in anticipation of the completion of the Australian Overland Telegraph Line in 1872 connecting to Adelaide, South Australia and thence to the rest of Australia. 
1872
Submarine cables connected all the world's continents except Antarctica when Java was connected to Darwin, Northern Territory, Australia in 1871 in anticipation of the completion of the Australian Overland Telegraph Line in 1872 connecting to Adelaide, South Australia and thence to the rest of Australia. 
Darwin
 Submarine cables connected all the world's continents except Antarctica when Java was connected to Darwin, Northern Territory, Australia in 1871 in anticipation of the completion of the Australian Overland Telegraph Line in 1872 connecting to Adelaide, South Australia and thence to the rest of Australia. 