Who gave the first evidence of the Big-Bang theory?

The first observational evidence for the Big Bang theory, also known as the expanding universe hypothesis, was provided by Edwin Hubble in 1929 [c3][c4]. By observing the redshift phenomenon in distant galaxies, Hubble demonstrated a correlation between a galaxy's distance and its radial velocity, proving that the universe is expanding [c1][t5]. This empirical discovery, known as Hubble's Law, marked a turning point in cosmology by providing the first physical proof that galaxies are moving away from each other [t6]. While Georges Lemaître had theoretically proposed the 'primeval atom' earlier, it was Hubble's data that provided the essential observational confirmation [t5]. Other critical evidence, such as the Cosmic Microwave Background (CMB) radiation, was not discovered until 1965 by Penzias and Wilson, long after Hubble's initial findings [c2][t4].

Sources

1. [1] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 1: The Universe, The Big Bang Theory, Galaxies & Stellar Evolution > Doppler-Shift or Redshift and Blueshift > p. 3
2. [2] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 1: The Universe, The Big Bang Theory, Galaxies & Stellar Evolution > Cosmic Microwave Background (CMD) > p. 4
3. [3] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 2: The Solar System > Earlier Theories > p. 17
4. [4] FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 1: Geography as a Discipline > Origin of the Universe > p. 13
5. [5] https://pmc.ncbi.nlm.nih.gov/articles/PMC314128/