* Constant Speed: Light travels at a constant speed in a vacuum, approximately 299,792,458 meters per second (often rounded to 300,000 km/s). This is known as the speed of light (c).
* Special Relativity: Einstein's theory of special relativity states that the speed of light in a vacuum is the same for all observers, regardless of the motion of the source or the observer.
* No Rest Mass: Light has no rest mass. This means it can't be accelerated from a state of rest. It's always traveling at the speed of light.
What can change about light from a star:
* Frequency and Wavelength: The light emitted by a star can be shifted in frequency and wavelength due to the Doppler effect. If the star is moving towards us, the light will be shifted towards higher frequencies (blue shift), and if it's moving away, the light will be shifted towards lower frequencies (red shift). This is how we determine if stars are moving towards or away from Earth.
* Intensity: The intensity of light from a star can change based on its distance from us and its intrinsic brightness.
In summary: Light from a star travels at a constant speed (the speed of light) and does not accelerate. The Doppler effect can change the frequency and wavelength of the light we observe, but not the speed of the light itself.
