GMAT RC #1

Let's see how these tips might help. Here is a Reading Comprehension exercise from Manhattan Review's Study Companion. The subject matter is the historic transition from classical physics to quantum physics.  It is intellectually difficult; so the challenge is to read quickly AND to get a handle on the author's central argument on the first read through:

However inventive Newton's clockwork universe seemed to his contemporaries, by the early twentieth century, it had become a sort of smugly accepted dogma. Luckily for us, this deterministic picture of the universe breaks down at the atomic level.

The clearest demonstration that the laws of physics contain elements of randomness is the behavior of radioactive atoms. Pick two identical atoms of a radioactive isotope, say naturally occurring uranium 238, and watch them carefully. They will begin to decay at different times, even though there was no difference in their initial behavior. We would be in big trouble if these atoms' behavior were as predictable as expected in the Newtonian world-view, because radioactivity is an important source of heat for our planet. In reality, each atom chooses a random moment at which to release its energy, resulting in a nice steady heating effect. The earth would be a much colder planet if only sunlight heated it and not radioactivity. Probably there would be no volcanoes, and the oceans would never have been liquid. The deep-sea geothermal vents in which life first evolved would never have existed.

But there would be an even worse consequence if radioactivity were deterministic: after a few billion years of peace, all the uranium 238 atoms in our planet would presumably pick the same moment to decay. The huge amount of stored nuclear energy, instead of being spread out over eons, would all be released simultaneously, blowing our whole planet to kingdom come. (This is under the assumption that all the uranium atoms were created at the same time. In reality, we have only a general idea of the process that might have created the heavy elements in the gas cloud from which our solar system condensed. Some portion may have come from nuclear reactions in supernova explosions in that nebula, some from intra-galactic supernova explosions and others still from exotic events like the collisions of white dwarf stars.)

The new version of physics, incorporating certain kinds of randomness, is called quantum physics. It represented such a dramatic break with the previous, deterministic tradition that everything that came before is considered classical, even the theory of relativity.

The first paragraph informs us that the deterministic picture of the universe fails at the atomic level. The second paragraph focuses on the importance of randomness in the universe. The third paragraph continues with the theme of the importance of randomness and spells out the catastrophic consequences that would transpire were randomness not the rule the universe. The fourth and last paragraph introduces us to quantum physics, which partially supplanted the Newtonian world and offered a picture of the universe based on randomness