How have scientists determined the age of the Earth?
What will be an ideal response?
Answer: Eighteenth-century geologists, including James Hutton, applied scientific observations and principles to conclude that the geologic rock record requires that Earth be extraordinarily ancient. Lord Kelvin calculated Earth's age based on a conceptual model of how much the planet has cooled since its origin. His calculations suggested an age in the range of 20-40 million years. John Joly calculated the age of the oceans based on a conceptual model of how long it would take Earth's rivers to transport enough salt to account for the current saltiness of the ocean. His calculations suggested an age of 80-100 million years. Kelvin's and Joly's calculations were correct but included assumptions that could not be verified at the time of their work. Reconsideration of their assumptions shows that the ages they calculated are minimum values and, therefore, Earth must be still older.
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If you plug a 110-V electric toaster into a 220-V outlet, current in the toaster will be about
A. more than twice what it should be. B. half what is should be. C. the same as if it were plugged into a 110-V outlet. D. twice what it should be.
How do wave trains travel? How do they interact with each other?
A farmer extending his farm field bulldozes the banks of a creek, greatly disturbing the creek bed and stirring up clay and humus. The higher levels of clay and humus in the water just downstream will most likely result in
A) fewer plants, fewer fish, and cloudy water. B) more plants but fewer fish and cloudy water. C) more plants and more fish but cloudy water. D) more plants and more fish and clearer water.
The Solar System, Sun, and Earth formed about 4.6 billion years ago
Indicate whether the statement is true or false