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Light's Colorful Quirks

As many of you are aware, I am a huge science nerd, particularly for astronomy and astrophysics. I love reading about the cutting edge mind-bending concepts that new observations of the universe beget, and am inspired to see the everyday world differently because of them. (I also use them as bases for composition, but that is a different post entirely.) One of my favorite of these seemingly-science-fiction ideas is called “rainbow gravity,” which describes the behavior of light as it is influenced by gravity, and has been used as evidence that the universe is eternal. I know, right?!


To prepare: the current model of our universe is that space-time resembles a giant flat surface whose expansion is accelerating. Matter creates ‘dips’ in that surface, much like how you’d create a dip in the surface of your mattress if you stood on your bed. The more density and/or mass a clump of matter has, the deeper this indent, and the stronger the gravity: if you were to place a bowling ball and a golf ball on the surface of your mattress, they would create different-sized dips. Gravity, here, is illustrated by rolling another object along the surface of the bed near the various balls - it will tend toward the heavier & denser object (the bowling ball) as it creates the larger and deeper dip. Out in the universe, even light cannot escape these gravity wells, even though it takes an enormous amount of gravitational exertion to alter light in observable ways. (One of my favorite telescope photos shows two galaxies merging, creating enough gravitational force to visibly lens light around them.)


The theory of Rainbow Gravity thus proposes that an object with a sufficiently strong gravitational force will act as a prism on the light passing it, affecting the different wavelengths (which we perceive as colors) with different strengths and influencing each slightly differently. This causes the light to fracture, and, when observed, the beam presents as a rainbow, with different wavelengths hitting us at different times. The idea is born from the disparity between relativity and quantum mechanics, specifically the mathematics of how space-time curves, and the incompatibility between locality (from relativity), wherein one entity can affect another if they are close enough, and the seemingly random, distance-ignoring tenets of quantum mechanics. Extrapolating: rainbow gravity precludes the pre-Big Bang point of infinite density known as the singularity. If one were to reverse the flow of time, the universe’s expansion eventually reaches zero, but gravity lensing in this way, if true, suggests the universe does not have a single point of origin (and thus one singularity cannot have existed).


I find this absolutely fascinating. The image of a beam of light passing a galaxy and fanning its colors out like a prismatic peacock tail leaves me breathless. And the idea that it might point to the eternal nature of the universe just raises more questions, at once scientific, philosophical, and spiritual. It reminds me of the way one’s imagination can also fracture into a mosaic of beauty, and, so far as we know, there is no single point of origin for dreams either.

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