Understanding the Redshift of Light from Distant Stars and Galaxies
The redshift observed in the light from distant stars and galaxies has long been a subject of intense study, particularly in the context of modern physics. This phenomenon, also known as the Doppler effect, allows us to infer not only the chemical composition of distant stars but also their motion relative to Earth.
Observation and Detection of Redshift
Using spectroscopes on telescopes, scientists can detect dark absorption lines in the spectrum of light from distant stars. These lines, which correspond to the wavelengths absorbed by specific elements, either shift towards or away from the red end of the spectrum. A shift towards the red end indicates that the light source is moving away from us, while a shift towards the blue end indicates movement towards us. This allows astronomers to determine whether a star is moving away or towards us and at what speed.
For example, when some starlight was emitted billions of years ago, there was no relative motion between the emitter and the observer (Earth). Therefore, the light propagated outward at the speed of light, c, and arrived at Earth also at speed c. However, this simple addition of speeds raises a challenge when reconciling with the principles of special relativity.
Challenges with the Second Einstein Postulate
The second postulate of special relativity states that the speed of light, c, is constant in all inertial frames of reference. If we apply this principle, the simple addition of speeds would suggest that the light from a moving source appears to have a different speed relative to us, which contradicts the postulate. Additionally, the common assumption that the Doppler effect is given by the formula ( c pm v / c ) or ( 1 pm v / c ) also conflicts with special relativity.
Controversially, it is argued that the Doppler effect is defined instead by ( c / c pm v ). This scaling affects the apparent wavelengths, frequencies, clock rates, and distances, leading to observed redshifts in the light from distant stars. This is known as the Doppler redshift and is a virtual phenomenon, not causing physical slowing of atomic clocks or changes in physical line spectra.
Rational Explanation Based on Relativistic Mechanics
To fully understand the redshift phenomenon, we need to address the key differences between Newtonian mechanics and relativistic mechanics. The relativistic approach includes the finite speed of light, ( c ), replacing the infinite speed of light implied in Newtonian physics.
The observed redshift is due to the propagation delay of light. When observing a remote object, the light travels to us, and the observer experiences a delay. This delay causes the remote clock to appear to run slower or faster, depending on the direction of the propagation.
The fundamental cause of this relativistic time dilation is the propagation delay between the emitter and the observer. If the propagation delay is increasing, the remote clock appears to lag and run slower. Conversely, if the propagation delay is decreasing, the remote clock appears to run faster.
Propagation Delays and Speeds
The speed of light, ( c ), is defined as the ratio of propagation distance (plus or minus ( pm x )) to propagation delay (time difference ( t' - t )). The valid linear definition of ( c ) is ( ct' ct pm x ). The Lorentz space-time transform, often used to explain the invariant speed of light, is problematic and does not provide a valid solution.
A linear Doppler alternative using ( ct' ct pm vt' ) offers a more accurate description, with the scale factor becoming ( c / c pm v ) for receding stars and ( c / c pm v ) for incoming stars. This interpretation avoids the issues with the second order premise in special relativity and provides a clearer explanation of the redshift phenomenon.
Experimental Evidence and Future Research
The James Webb Space Telescope (JWST) has provided evidence of significant redshift and time dilation, with a scale factor of ( lambda' / lambda Delta t' / Delta t c / c - v 14.2 ) corresponding to ( v 0.93c ). This suggests that some objects in the universe might exceed or have exceeded the speed of light.
Further research is needed to investigate these phenomena and their implications for our understanding of the universe. The apparent violation of the speed of light limit may point to new theories or explanations that go beyond current relativity.