What physical phenomenon, resulting from the Doppler effect, was crucial for determining the recession speed of distant objects?
Answer
Redshift of the light spectrum
The speed at which remote astronomical objects move away from an observer is determined almost entirely through analyzing the light they emit using spectroscopy. When a light source recedes, the wavelengths of that light are stretched, causing the spectral lines—the dark lines caused by specific elements absorbing certain wavelengths—to shift toward the longer, red end of the electromagnetic spectrum. This observable shift, termed redshift, serves as the direct indicator of the object's recessional velocity.
Related Questions
What framework did Edwin Hubble successfully apply and calibrate in the 1920s to measure galactic distances?What physical phenomenon, resulting from the Doppler effect, was crucial for determining the recession speed of distant objects?Who was responsible for the initial heavy lifting in measuring the recessional velocities of spiral nebulae decades before Hubble related velocity to distance?What mathematical relationship, represented by $v = H_0 d$, defines the correlation Hubble found between recession velocity ($v$) and distance ($d$)?What term is used to describe astronomical objects whose known intrinsic brightness allows astronomers to calculate their distance using apparent brightness?What specific luminous, pulsating star was Hubble’s primary tool for deriving distances to remote galaxies like Andromeda (M31)?What crucial physical link concerning Cepheid variables was discovered by Henrietta Swan Leavitt?Which geometric method was necessary for the initial calibration step to determine the true baseline luminosities of nearby Cepheid variables?What was the approximate numerical value for the Hubble Constant ($H_0$) calculated by Hubble in his early publications around 1929?What brighter standard candles, which must be calibrated using Cepheid distances, are now used to measure objects billions of light-years away?