In the 19th century, scientists knew that light was some kind of wave. And every kind of wave science had yet described needed a medium to travel through—the way that sound waves travel through matter. But scientists had never observed light's medium. As they searched for evidence of it, scientists decided to call light's theoretical medium the luminiferous ether.

Albert Michelson Edward Morley

In 1887, Albert A. Michelson and Edward W. Morley conducted an experiment to measure the speed at which the Earth moves through the ether. Their experiment was so refined that it should have finally detected the luminiferous ether. But it didn't. Repeated trials verified the surprising result that the ether did not exist.

Dna is colied into chromosomes in a cell

In 1959, doctors began using the powerful antibiotic methicillin to treat infections of staphylococcus aureus, but within two years, methicillin-resistant strains of s. aureus (mrsa) appeared. how did the resistant strains of s. aureus emerge? in 1959, doctors began using the powerful antibiotic methicillin to treat infections of staphylococcus aureus, but within two years, methicillin-resistant strains of s. aureus (mrsa) appeared. how did the resistant strains of s. aureus emerge? staphylococcus aureus bacteria that were able to synthesize cell walls using a protein that was not affected by methicillin survived the methicillin treatments and reproduced at higher rates than did other individuals. over time, these resistant individuals became increasingly common. in response to treatment of staphylococcus aureus infections with methicillin, some bacteria began to synthesize cell walls using a protein that was not affected by methicillin. these bacteria survived the methicillin treatments and reproduced at higher rates than did other individuals. over time, these resistant individuals became increasingly common. in response to treatment of staphylococcus aureus infections with methicillin, bacterial populations gradually began to synthesize cell walls using a protein that was not affected by methicillin.

Which of the follow describes a disadvantage secondary sources have compared to primary sources?