This lesson introduces the development of ideas about the universe’s beginning, from Georges Lemaître’s early proposal to the modern understanding of the hot, expanding universe. It matters because scientific models change as evidence and knowledge improve.
General relativity implies that the universe has expanded from an earlier, denser state. Describing that beginning, however, required a physical model. Belgian priest and cosmologist Georges Lemaître proposed that the universe began in a concentrated state he called the primeval atom. He imagined it fragmenting into smaller pieces, eventually becoming the atoms found in the universe today.
All flashcards
Who proposed the primeval atom?
Georges Lemaître, a Belgian priest and cosmologist, proposed a concentrated beginning he called the primeval atom.
What was Lemaître’s primeval atom model?
It pictured the universe’s matter beginning together in a concentrated state and then fragmenting into smaller pieces. Its fission-like explanation is not the modern model.
How does nuclear fusion differ from fission in this historical context?
Fusion combines lighter nuclei to make heavier nuclei. Lemaître’s original proposal instead pictured the primeval material breaking apart in a process resembling fission.
What did Gamow and Alpher contribute?
They developed an early model in which the hot early universe could form elements through nuclear fusion; Alpher worked out key details for the 1948 paper.
What is the modern view of the universe’s early state?
The universe was once much hotter and denser than it is now, and it cooled as it expanded. Early fusion made mainly hydrogen and helium, along with a little lithium.
Quiz questions
About 0.01 second after the universe began expanding, what temperature did physical models estimate?Answer: Approximately 1011 K.
At a temperature around 6×109 K, what particle pair could typical photon collisions produce?Answer: An electron and a positron.
When did neutrinos largely stop interacting with ordinary matter in the early universe?Answer: A little more than one second after the beginning.
How did higher early ordinary-matter density affect the amount of deuterium that survived?Answer: More deuterium interacted with protons and became helium, leaving less deuterium.
What present-day density of ordinary matter is indicated by deuterium measurements?Answer: About 5×10−28 kg/m3.
Based on Astronomy 2e by Andrew Fraknoi, David Morrison, Sidney Wolff (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.