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Author Question: If astronauts could travel at v = 0.90c, we on Earth would say it takes (4.2/0.90) = 4.7 years to ... (Read 18 times) |
The first-known contraceptive was crocodile dung, used in Egypt in 2000 BC. Condoms were also reportedly used, made of animal bladders or intestines.
In 1844, Charles Goodyear obtained the first patent for a rubber condom.
Although the Roman numeral for the number 4 has always been taught to have been "IV," according to historians, the ancient Romans probably used "IIII" most of the time. This is partially backed up by the fact that early grandfather clocks displayed IIII for the number 4 instead of IV. Early clockmakers apparently thought that the IIII balanced out the VIII (used for the number 8) on the clock face and that it just looked better.
In the United States, there is a birth every 8 seconds, according to the U.S. Census Bureau's Population Clock.
Intradermal injections are somewhat difficult to correctly administer because the skin layers are so thin that it is easy to accidentally punch through to the deeper subcutaneous layer.