In 1850, the French astronomer E. A. Roche (1820 – 1883) stated “no satellite can exist closer to a planet than 2.44x its radius or 1.44x from its surface.”
If a satellite or comet that is held together solely by its gravitational force (no tensile strength) passes within the planet’s Roche limit, it will break apart.
This
night looked at Beta-Persei (Algol) and was much amazed to find
its
brightness altered. It now appears to be fourth magnitude... I observed
it
diligently for about an hour upwards...hardly believing that it changed
its
brightness, because I had never heard of any star varying so quick in
its
brightness. I thought it might be perhaps owing to an optical
illusion,
a defect in my eyes or bad air, but the sequel will show that its
change
is true and that it was not mistaken.
(John
Goodricke, journal entry November 12, 1782)
A device that can use Wi-Fi (such as a personal computer, video game console, smartphone, tablet, or digital audio player) can connect to a network resource such as the Internet via a wireless network access point. Such an access point (or hotspot) has a range of about 20 meters (65 feet) indoors and a greater range outdoors. Hotspot coverage can comprise an area as small as a single room with walls that block radio waves or as large as many square miles — this is achieved by using multiple overlapping access points.