The correct answer is Red shift in the light coming from distant galaxies. Key Points • Red shift refers to the phenomenon where the light emitted by distant celestial objects shifts toward the red end of the spectrum due to the expansion of the universe. • This observation was first explained by Edwin Hubble in the 1920s, who discovered that galaxies farther from us are moving away at faster speeds, a concept now known as Hubble's Law. • The red shift is a direct consequence of the Doppler Effect, where the wavelength of light increases as the source moves away from the observer. Hence, the statement is correct. • The red shift provides strong evidence for the Big Bang Theory, which proposes that the universe began from a highly dense and hot state and has been expanding ever since. • This expansion is uniform, meaning galaxies are not moving through space but rather space itself is stretching. This is why light from distant galaxies appears red-shifted. Hence, the explanation confirms the expansion of the universe. • Other phenomena, such as blue shift (light moving to the blue end of the spectrum), occur when objects move closer, but such cases are rare in an expanding universe. Hence, option 2 is incorrect. • The bending of light near black holes (gravitational lensing) and the constancy of the velocity of light are unrelated to the expansion of the universe. Hence, options 3 and 4 are also incorrect. • Therefore, the correct answer is Red shift in the light coming from distant galaxies. Additional Information • Hubble's Law: • Formulated by Edwin Hubble, it states that the recession velocity of galaxies is directly proportional to their distance from the observer. • The mathematical expression is: v = H_(0) × d, where v is the recession velocity, H_(0) is the Hubble constant, and d is the distance. • The current value of the Hubble constant is approximately 70 km/s/Mpc, although it is still a topic of research and debate. • Big Bang Theory: • The Big Bang Theory explains the origin and expansion of the universe approximately 13.8 billion years ago. • The red shift observed in the light from distant galaxies is one of the strongest pieces of evidence supporting this theory. • Other evidence includes the Cosmic Microwave Background Radiation and the abundance of light elements like hydrogen and helium. • Doppler Effect: • This is the change in frequency or wavelength of a wave in relation to an observer moving relative to the wave source. • In the context of light, a red shift indicates the source is moving away, while a blue shift indicates the source is approaching. Important Points • Red Shift and Expansion: • The red shift is observed in almost all galaxies, indicating that the universe is expanding in all directions. • This expansion is not due to galaxies moving away but because space itself is stretching. • Cosmological Significance: • The red shift provides insights into the age, size, and ultimate fate of the universe. • It also helps in estimating the distances of faraway galaxies, crucial for mapping the large-scale structure of the universe.