Question

13. The observation of what overall characteristic of the CMBR left, "... no real doubt we are seeing the residual radiation left behind from the hot, dense beginning of the early universe."

14. The tiny fluctuations in the early universe due to gravity redshifts from concentrations of mass eventually led to what?

16. List two processes or events that formed the elements heavier than helium: a) those that make carbon, nitrogen, and oxygen, and b) those that make iron, nickel, gold, and even heavier elements.

17. The discovery of what aspect of the Universe restores Einstein’s “biggest blunder” (his fudge factor in his equations) to general relativity

Answer 1

13. The observation of what overall characteristic of the CMBR left, "... no real doubt we are seeing the residual radiation left behind from the hot, dense beginning of the early universe."

In 1965, pair of radio astronomers named Arno Penzias and Bob Wilson was working at Bell Labs, New Jersey using an antenna sensitive to microwave radiation, they discovered a mysterious source of static or noise. They did everything to reduce the noise (including shooing away a pair of pigeons who had roosted in their telescope), but the static persisted. It was realized later that the microwaves had a blackbody spectrum, with a characteristic temperature of only T = 2.725 Kelvin (and thus having lambdamax = 1 millimeter). These ubiquitous microwaves, seen in every direction, are called the Cosmic Microwave Background Radiation (CMBR). The Cosmic Microwave Background is a relic of the time when the universe was hot, dense, and opaque and result from density fluctuations in the early universe

For example:

• The Sun is made of hot, dense, ionized gas, opaque because it is ionized. (Free electrons scatter photons, preventing them from zipping straight through the Sun.) emits blackbody radiation.

However, the Big Bang theory states that the universe was once hotter and denser than it is today.

• The early universe was full of hot, dense, ionized gas, opaque because it was ionized, emitted blackbody radiation.

As the universe expanded, however, it became cooler and less dense. About 300,000 years after the start of expansion, the temperature of the universe had cooled to 3000 Kelvin. At this temperature:

• Protons and electrons combined to form neutral hydrogen atoms. (This process is known to physicists as recombination.)
• The universe, lacking free electrons to scatter the photons, suddenly became transparent.
• The liberated photons started streaming freely in all directions.

Thus, the photons in the Cosmic Microwave Background are relics of the early, hot, dense, ionized, opaque universe. They have been traveling through space for over 13 billion years, and hence are sometimes called ``the oldest light in the universe''

14. The tiny fluctuations in the early universe due to gravity redshifts from concentrations of mass eventually led to what?

In its early days, the universe was extremely smooth and homogenous but not quite perfectly. Although the temperature of the CMB is almost completely uniform at 2.7 K, there are very tiny variations, or anisotropies in the temperature on the order of 10-5 K. The anisotropies appear on the map as cooler blue and warmer red patches. These anisotropies in the temperature map correspond to areas of varying density fluctuations in the early universe. Eventually, gravity would draw the high-density fluctuations into even denser and more pronounced ones. After billions of years, these little ripples in the early universe evolved, through gravitational attraction, into the planets, stars, galaxies, and clusters of galaxies that we see today. This lumpiness affects the CMB largely because of gravitational redshifting. Radiation emitted from a dense spot in the sky has to fight against a bit of extra gravity as it heads toward our detectors.

16. List two processes or events that formed the elements heavier than helium: a) those that make carbon, nitrogen, and oxygen, and b) those that make iron, nickel, gold, and even heavier elements.

A star's energy comes from the combining of light elements into heavier elements in a process known as fusion, or nuclear burning. Most of the elements in the universe heavier than helium are created, or synthesized, in stars when lighter nuclei fuse to make heavier nuclei. The process is called nucleosynthesis.

Nucleosynthesis requires a high-speed collision, which can only be achieved with very high temperature. The minimum temperature required for the fusion of hydrogen is 5 million degrees. Elements with more protons in their nuclei require still higher temperatures. For instance, fusing carbon requires a temperature of about one billion degrees! Most of the heavy elements, from oxygen up through iron, are thought to be produced in stars that contain at least ten times as much matter as our Sun.

Our Sun is currently burning, or fusing, hydrogen to helium. This is the process that occurs during most of a star's lifetime. After the hydrogen in the star's core is exhausted, the star can burn helium to form progressively heavier elements, carbon and oxygen and so on, until iron and nickel are formed. Up to this point the process releases energy. The formation of elements heavier than iron and nickel requires the input of energy. Supernova explosions result when the cores of massive stars have exhausted their fuel supplies and burned everything into iron and nickel. The nuclei with mass heavier than nickel are thought to be formed during these explosions.Elements up to and including iron are made in the hot cores of short-lived massive stars. Elements heavier than iron—the majority of the periodic table—are primarily made in environments with free-neutron densities in excess of a million particles per cubic centimeter.

17. The discovery of what aspect of the Universe restores Einstein’s “biggest blunder” (his fudge factor in his equations) to general relativity

In 1915, after the completion of his General Theory of Relativity, Einstein was chagrined to find a near-fatal flaw in the theory. The thought of an expanding Universe with a beginning, the Big Bang, struck at the very core of his belief in an “unchanging,” steady-state model of the cosmos.
He introduced a “fudge factor” in the equations and fine-tuned its value to make the Universe static, neither expanding nor contracting. He coined the term “cosmological constant” for the factor and interpreted it as a repulsive force required to stabilize the Universe and make it motionless. Einstein probably was unaware of physicists' mantra: “No theory should agree with all the data, because some of the data are sure to be wrong.” In 1929, the great astronomer Edwin Hubble's discovery of an expanding Universe gave Einstein the goose bumps. Much to his consternation, Hubble's observation supporting the Big Bang Model made Einstein go back to the chalkboard and rethink about the cosmological constant. In 1931, he realized his mistake and embraced the Big Bang Theory as “the most beautiful and satisfactory explanation of creation which I have ever listened.” He referred to the fudge factor as “the biggest blunder of my career.”