Origin of the Universe: From Big Bang to Planet Earth

Charlene Estrada and Chris Johnson, Matthew D. Affolter, Paul Inkenbrandt, Cam Mosher

The picture has over 1500 galaxies.
The Hubble Deep Field. This image, released in 1996, is a composite long-exposure picture of one of the darkest parts of the night sky. Every light on this image that does not have diffraction spikes is believed to be an entire galaxy, with hundreds of billions of stars, demonstrating the immense size and scope of the universe.

The universe appears to have an infinite number of galaxies and solar systems and our solar system occupies a small section of this vast entirety. The origins of the universe and solar system set the context for conceptualizing the Earth’s origin and early history.

Big-Bang Theory

It starts small, then explodes outward
Timeline of the expansion of the Universe

The mysterious details of events before and during the universe’s origin are subject to great scientific debate. The prevailing idea about how the universe was created is called the big-bang theory. Although the ideas behind the big-bang theory feel almost mystical, they are supported by Einstein’s theory of general relativity. Other scientific evidence, grounded in empirical observations, supports the big-bang theory. The big-bang theory proposes that the universe was formed from an infinitely dense and hot material core. The bang in the title suggests there was an explosive, outward expansion of all matter and space that created atoms. Spectroscopy confirms that hydrogen makes up about 74% of all matter in the universe. Since its creation, the universe has been expanding for 13.8 billion years, and recent observations suggest that this expansion is increasing.
COSMIC MICROWAVE BACKGROUND RADIATION

The map is blue with slight bright spots of green/yellow
Heat map showing slight variations in background heat, which is related to cosmic background radiation.

A strong indication of the big bang is cosmic microwave background radiation. Cosmic radiation was accidentally discovered by Arno Penzias (1933–) and Robert Woodrow Wilson (1936–) when they were trying to eliminate background noise from a communication satellite. They discovered very faint traces of energy or heat that are omnipresent across the universe. This energy was left behind from the big bang, like an echo.

Stellar Evolution

This shows the period table. Some elements are made in the big bang, some are made in stellar processes.
The origin of the elements on the periodic table shows the star life cycle’s important role.

Astronomers think the big bang created lighter elements, mostly hydrogen, and smaller amounts of elements helium, lithium, and beryllium. Another process must be responsible for creating the other 90 heavier elements. The current model of stellar evolution explains the origins of these heavier elements.

BIRTH OF A STAR

It is several large column of gas
Section of the Eagle Nebula known as “The Pillars of Creation.”

Stars start their lives as elements floating in cold, spinning clouds of gas and dust known as nebulas. Gravitational attraction or perhaps a nearby stellar explosion causes the elements to condense and spin into a disk shape. In the center of this disk shape, a new star is born under the force of gravity. The spinning whirlpool concentrates material in the center, and the increasing gravitational forces collect even more mass. Eventually, the immensely concentrated mass of material reaches a critical point of such intense heat and pressure it initiates fusion.

Origin of the Solar System: The Nebular Hypothesis

It is a small cloud
Small protoplanetary discs in the Orion Nebula

Our solar system formed at the same time as our Sun, as described in the nebular hypothesis. The nebular hypothesis is the idea that a spinning cloud of dust made of mostly light elements, called a nebula, flattened into a protoplanetary disk and became a solar system consisting of a star with orbiting planets. The spinning nebula collected the vast majority of material in its center, which is why the sun Accounts for over 99% of the mass in our solar system.

Planet Arrangement and Segregation

The disc is lop sided
This disk is asymmetric, possibly because of a large gas giant planet orbiting relatively far from the star.

As our solar system formed, the nebular cloud of dispersed particles developed distinct temperature zones. Temperatures were very high close to the center, only allowing condensation of metals and silicate minerals with high melting points. Farther from the Sun, the temperatures were lower, allowing lighter gaseous molecules such as methane, ammonia, carbon dioxide, and water condensation. This temperature differentiation resulted in the inner four planets of the solar system becoming rocky, and the outer four planets becoming gas giants.

The orange disk has zones that are darker, indicating the planets are growing by using that material in the disk.
Image by the ALMA telescope of HL Tauri and its protoplanetary disk, showing grooves formed as planets absorb material in the disk.
Image by the ALMA telescope of HL Tauri and its protoplanetary disk, showing grooves formed as planets absorb material in the disk.

Both rocky and gaseous planets have a similar growth model. Particles of dust, floating in the disc were attracted to each other by static charges and eventually, gravity. As the clumps of dust became bigger, they interacted with each other—colliding, sticking, and forming proto-planets. The planets continued to grow over the course of many thousands or millions of years, as material from the protoplanetary disc was added. Both rocky and gaseous planets started with a solid core. Rocky planets built more rock on that core, while gas planets added gas and ice. Ice giants formed later and on the furthest edges of the disc, accumulating less gas and more ice. That is why the gas-giant planets Jupiter and Saturn are composed of mostly hydrogen and helium gas, more than 90%. The ice giants Uranus and Neptune are composed of mostly methane ices and only about 20% hydrogen and helium gases.

 

It shows a ring of ice around the star
This artist’s impression of the water snowline around the young star V883 Orionis, as detected with ALMA.

This artist’s impression of the water snowline around the young star V883 Orionis, as detected with ALMA.

The planetary composition of the gas giants is clearly different from the rocky planets. Their size is also dramatically different for two reasons: First, the original planetary nebula contained more gases and ices than metals and rocks. There was abundant hydrogen, carbon, oxygen, nitrogen, and less silicon and iron, giving the outer planets more building material. Second, the stronger gravitational pull of these giant planets allowed them to collect large quantities of hydrogen and helium, which could not be collected by the weaker gravity of the smaller planets.

The meteorite is polished showing the Widmanstätten Pattern.
A polished fragment of the iron-rich Toluca Meteorite, with octahedral Widmanstätten Pattern.
Jupiter’s massive gravity further shaped the solar system and growth of the inner rocky planets, including our planet Earth. As the nebula started to coalesce into planets, Jupiter’s gravity accelerated the movement of nearby materials, generating destructive collisions rather than constructively gluing material together. These collisions created the asteroid belt, an unfinished planet located between Mars and Jupiter. This asteroid belt is the source of most meteorites currently impacting the Earth. The study of asteroids and meteorites help geologist determine the age of Earth and the composition of its core, mantle, and crust. Jupiter’s gravity may also explain Mars’ smaller mass, with the larger planet consuming material as it migrated from the inner to the outer edge of the solar system.

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Introduction to Historical Geology Copyright © by Charlene Estrada and Chris Johnson, Matthew D. Affolter, Paul Inkenbrandt, Cam Mosher is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License, except where otherwise noted.

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