Question

How did scientists come up with the theory of Big Bang? Where do we even get the idea that there used to be nothing?

Answer 1

The theory of the Big Bang emerged as a scientific explanation for the origin and evolution of the universe based on observational and theoretical evidence. Here's a general overview of how scientists arrived at the concept:

1. Observations of the Universe: In the early 20th century, astronomers made observations that suggested the universe was expanding. Edwin Hubble's discovery of the redshift in the light from distant galaxies provided evidence for this expansion.

2. General Relativity: Albert Einstein's theory of general relativity, formulated in 1915, provided a mathematical framework for describing the behavior of gravity on a cosmic scale. Solutions to Einstein's equations by physicists like Alexander Friedmann and Georges Lemaître suggested that the universe could have originated from an extremely dense and hot state.

3. Cosmic Microwave Background (CMB): In the 1960s, Arno Penzias and Robert Wilson accidentally discovered the cosmic microwave background radiation, which is a faint radiation permeating the entire universe. This radiation is considered a remnant of the hot and dense early universe, and its discovery provided strong evidence for the Big Bang theory.

4. Nucleosynthesis: The theory of Big Bang nucleosynthesis explains the formation of light elements (hydrogen, helium, and a trace amount of lithium) in the early universe. The relative abundances of these elements observed in the universe today align with the predictions made by the Big Bang theory.

5. Cosmic Expansion and Hubble's Law: The observation of the ongoing expansion of the universe, coupled with Hubble's law linking the recessional velocity of galaxies to their distance, further supported the Big Bang model.

It's important to note that the Big Bang theory does not propose that there was "nothing" before the Big Bang. Instead, it suggests that the universe was in an extremely hot, dense, and compact state from which expansion and subsequent cosmic evolution occurred. The precise nature of what preceded the Big Bang is an area of ongoing scientific investigation and remains a subject of active research and theoretical speculation.