Now, put a light emitting object in your mind far, far away.
In a lengthy 1977 song, the musicians proclaimed Cygnus X-1, an x-ray emitting object thousands of light-years away, a black hole where voyagers venture "through the void to be destroyed"—even though physicist Stephen Hawking had bet against the black hole's existence.
A region of the Andromeda galaxy, as imaged by Hubble's Panchromatic Hubble Andromeda Treasury, along with the unusual, X-ray emitting object J0045+41, now known to be an ultra-distant binary supermassive black hole.
It turns out that just like for sound waves, the wavelength of light emitted by an object that is moving away from you is longer when you measure it than it is when measured in the rest frame of the emitting object.
In the same way, light also has a Doppler shift, whereby its frequency is shifted depending on the motion of the emitting object.
After the light is emitted, it doesn't matter what happens to the emitting object - it won't affect the wavelength of the light that is received.
Practically speaking, the difference between the two (Doppler redshift and cosmological redshift) is this: in the case of a Doppler shift, the only thing that matters is the relative velocity of the emitting object when the light is emitted compared to that of the receiving object when the light is received.
When you look out at the distant Universe, the light has to travel through the Universe from the emitting object to your eyes.
However, Dan Flavin gave continuity to his precedents practices by utilizing the light emitting object itself.
The X-ray emitting objects discovered by the research team are a distant galaxy thought to contain a central giant black hole, three elliptically shaped galaxies, an extremely red distant galaxy, and a nearby spiral galaxy.
At the Modern Institute, Joanne Tatham & Tom O'Sullivan had just finished a bewildering creation somewhere between an improbably serpentine desk and a vast question mark, an object emitting a long and comic chain of art-world banalities.
