For hundreds of years before the seventeenth century, thinkers explained that sudden appearances of life, such as mold on food or moss on rocks, were caused by "spontaneous generation,” which is the idea that life frequently springs up from non-living material. to the use of scientific experiments, which required repeatable tests, and the invention of the microscope, scientists such as louis pasteur discovered that these appearances of life were actually caused by microscopic organisms in the air that could stick to surfaces and grow into large populations we can see with our eyes. what is shown about scientific theories by the shift in belief of spontaneous generation to the use of other observations to explain where mold and moss come from? theories usually are false. theories are not useful. theories change over time. theories can be completely proven.

Dry ice is solid carbon dioxide that is used in the transport of food and medicine. dry ice becomes a gas at –78.5°c without becoming a liquid first.

In a thunderstorm, charge builds up on the water droplets or ice crystals in a cloud. thus, the charge can be considered to be distributed uniformly throughout the cloud. for the purposes of this problem, take the cloud to be a sphere of diameter 1.00 kilometer. the point of this problem is to estimate the maximum amount of charge that this cloud can contain, assuming that the charge builds up until the electric field at the surface of the cloud reaches the value at which the surrounding air breaks down. this breakdown means that the air becomes highly ionized, enabling it to conduct the charge from the cloud to the ground or another nearby cloud. the ionized air will then emit light due to the recombination of the electrons and atoms to form excited molecules that radiate light. in addition, the large current will heat up the air, resulting in its rapid expansion. these two phenomena account for the appearance of lightning and the sound of thunder. take the breakdown electric field of air to be eb=3.00ă—106n/c. part a estimate the total charge q on the cloud when the breakdown of the surrounding air is reached. express your answer numerically, to three significant figures, using ďµ0=8.85ă—10â’12c2/(nâ‹…m2) .

What are similarities and differences between refraction, reflection, diffraction and absorption?