The Formation Of The Light Elements 115y3d

THE FORMATION OF THE LIGHT ELEMENTS IN THE BIG BANG THEORY NUCLEOSYNTHESIS: THE BEGINNING OF ELEMENTS

Objectives In this lesson, you should be able to give evidence for and explain the formation of the light elements in the big bang theory.

What elements were produced during the big bang expansion?

Big Bang Theory The big bang theory is a cosmological model stating that the universe started its expansion about 13.8 billion years ago. Pieces of evidence ing this theory are (1) occurrence of redshift, (2) background radiation, and (3) abundance of light elements.

Redshift In the 1910s, Vesto Slipher and Carl Wilhelm Wirtz measured the wavelengths of light from spiral nebulae, which are interstellar clouds of dust and ionized gases. They discovered that the light from the nebulae increased in wavelength. They explained their discovery as a Doppler shift. The Doppler shift or Doppler effect explains that when an object gets closer to us, its light waves are compressed into shorter wavelengths (blueshifted, because blue light has the shortest wavelength in the visible region). On the other hand, when an object moves away from us, its light waves are

Slipher and Wirtz then explained that the redshift or increase in wavelength was due to the increase in the distance between the Earth and the nebulae. They concluded that the redshift occurred due to the expansion of space. In 1929, Edwin Hubble used the redshift of light from galaxies to calculate the velocities and distances of these galaxies from the Earth. He discovered that they were moving away from the Earth and from each other. His

Cosmic Microwave Background Radiation In 1965, Robert Wilson and Arno Penzias discovered a low, steady “hum” from their Holmdel Horn antenna (an antenna built to NASA’s Project Echo). They concluded that the noise is Cosmic Microwave Background Radiation (CMBR), the remains of energy created after the big bang expansion. Abundance of Light Elements The observed abundance of light elements s the big bang theory. The theory predicts that the universe is composed of 73% hydrogen and 25% helium by mass. The prediction correlated to the measured

Formation of Light Elements Big bang nucleosynthesis is the process of producing the light elements during the big bang expansion. In the beginning, the universe was very hot that matter was fully ionized and dissociated. Few seconds after the start of the big bang, the universe was filled with protons, neutrons, electrons, neutrinos, and positrons. After the first three minutes, the universe cooled down to a point where atomic nuclei can form. Protons and neutrons combined to form atomic nuclei such as deuterium.

However, the temperature of the universe was still much greater than the binding energy of deuterium. Binding energy is the energy required to break down a nucleus into its components. Therefore, deuterium easily decayed upon formation.

When the temperature cooled down 10 below 10 K, deuterium nuclei combined with other nuclei to form heavier ones. Helium-3 was formed from the fusion of two deuterium nuclei and a release of a neutron.

Tritium or hydrogen-3 was produced from the fusion of two deuterium nuclei and a release of a proton.

Helium-4 was also synthesized deuterium and helium-3.

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Helium-4 was produced from the fusion of deuterium and tritium.

Learn about it! For the first three minutes, a substantial amount of neutrons was converted into helium-4 nuclei, before their decay. Helium then combined to other nuclei to form heavier ones such as lithium-7 and beryllium-