Day 3 Science Text Set

What makes text complex?

Excerpts from Physical Science

Text 1

As we have seen, a neutron star would be small and dense. It should also be rotating rapidly. All stars rotate, but most of them do so leisurely. For example, our Sun takes nearly one month to rotate once about its axis. A collapsing star speeds up as its size shrinks, just as an ice skater during a pirouette speeds up when she pulls in her arms. This phenomenon is a direct consequence of a law of physics known as the conservation of angular momentum, which holds that the total amount of angular momentum in a system remains constant. An ordinary star rotating once a month would be spinning faster than once a second if compressed to the size of a neutron star.

In addition to having rapid rotation, we expect a neutron star to have an intense magnetic field. It is probably safe to say that every star has a magnetic field of some strength.

What makes text complex?

Excerpts from Physical Science

Text 2

In this way, a general explanation of the different types of galaxies begins to emerge. In an elliptical galaxy, the stars all formed before the gas had time to flatten into a disk; the more spheroidal the galaxy, the more rapidly this formation occurred. In a spiral galaxy, the stars of population aII formed before the end of the flattening phase. When the gas was concentrated in the shape of a flat disk, the stars formed from the gas where the gas was located – i.e., in the disk. It remains to be explained why the formation of stars took place more rapidly in the elliptical than in the spiral galaxies. Inasmuch as we cannot explain in detail how stars form, it is not easy to answer that question. It seems that the rate of formation of stars is related to the density of the gas; the denser the gas, the faster the rate of formation of stars. Therefore, some people have believed that the density of the gas making up the protogalaxy was higher in elliptical galaxies than in spiral galaxies. However, when we consider the average density of matter, currently in the form of stars that are contained in a galaxy, that average density does not seem to be significantly higher in the ellipticals.

What makes text complex?

Excerpts from Physical Science

Text 3

Since the invention of GUTs in 1974, particle theorists have been vigorously working on attempts to construct the ultimate theory of nature – an elegant theory which would include a quantum description of gravity. The characteristic energy scale of such a theory is presumably the Planck scale, 10¹⁹GeV, a point at which the gravitational interactions of elementary particles become comparable in strength to the other types of interactions. It is then hoped that a GUT would emerge as a low-energy approximation.

The latest and most successful of these attempts at unification is a radically new kind of particle theory known as ‘superstring theory.’ Superstrings represent a dramatic departure from conventional theories in that particles are viewed as ultramicroscopic strings (length = 10^-33 centimeters). Furthermore, according to this theory, the universe has nine spatial dimensions. Early in the history of the universe, when the temperature cooled below 10³² degrees Kelvin, all spatial dimensions, except the three we know today, stopped expanding and remained curled up with an unobservably small extent. As bizarre as the theory may sound, the superstring theory has been shown to possess a number of unique properties crucial to a quantum theory of gravity, and it has totally captured the attention of a large fraction of the worldwide particle theory community.

DMU Timestamp: February 21, 2017 15:38