Gravitational Blueshift Lumbar Pillow

A multi-coloured, fractal representation of gravitational blueshifting; the shifting of light toward the blue end of the spectrum that occurs as photons become more energetic when falling into a gravity well. Customize by adding your own text on the reverse side. Unlike the more commonly known Doppler blueshift, an apparent effect which is the result of motion towards the observer, gravitational blueshift is real, independent of the received angle of the photon. Gravitational blueshift is a natural consequence of conservation of energy and mass-energy equivalence.