How the Oort may unlock the secrets of gravity
There two leading theories of our time which attempt to describe how the warm infant universe took a bunch randomly distributed stars careening throughout the cosmos and organized them into beautiful varieties of pinwheel and elliptical shapes are Milgrom’s laws and Cold Dark Matter.
Each has their strengths and each has their weaknesses, one often excels precisely where the other fails and vice versa. As such a stalemate exists within the scientific community despite any loud exaltations you may hear to the contrary.
When I think about this problem I find myself coming back to Emma Noether, who I think would point out a thing cannot exist without some inherent symmetry within another area of the system of which it’s a part.
When I consider the two theories in the context of symmetry, it is easy to find symmetry with Milgrom’s laws and many of the fundamental laws and phenomena we can observe and measure in the universe. Dark matter on the other hand has no precedent, no symmetry, with anything in the universe we can find. All of our attempts to prove it’s existence have been governed by the need to not violate the symmetry of our understanding of the universe, and it has remained stubbornly asymmetric or we would have seen it by now.
Milgrom’s laws propose the force of gravity changes at vast distances similar to the way an electromagnetic field experiences a near and far field signal intensity loss distribution. So the question is how could we prove or disprove through experiment the assertions contained in MoND.
The answer it seems is eerily similar to the way we prove or disprove the existence of dark matter, by measuring things we cannot yet see.
For Milgrom’s law, this means finding an analogous gravitational system and measuring the velocities of objects orbiting at vast distances from the center. If we take our solar system as the analog, then we need to measure the mass and speeds of stable Oort cloud objects.
This however is much trickier than it sounds, we’ve never actually observed the Oort cloud directly. We infer it’s presence from the abundance of comets that swoop into the inner solar system, but we have yet to see it for ourselves.
Undertaking a survey of the Oort cloud is no small task and would challenge us in ways that building dark matter detectors at the bottom of mine shafts never will. It would, as once so notably stated, organize and measure the best of our energies and skills. It would require imagination and ingenuity, force us to develop new tools, create an environment where we can hope to discover something no matter what.
If we find a way to survey the Oort cloud we can both place further constraints on Milgrom’s law or prove them valid, as well as discover the what secrets the universe holds in the place comets are born.
Personally I believe the high orbital velocities of comets are a tantalizing clue to the effects of Milgrom’s law. After all it is assumed they get knocked into the inner solar system and it’s this interaction that helps boost their speed. Yet if you think about it something as small as a few kilometers orbiting many times faster than the planets at far greater orbital distances could in fact be consistent with Milgrom’s law.
It seems possible to me to look at the size and orbital period and velocity of some comets and see if there is any analog to predictions made by MoND of such an object orbiting at extreme distances, but I don’t know if any serious work has been done on it.
Either way it seems to me we are far better served by imagining ways to illuminate and observe the Oort cloud or the Kuyper belt and turning those ideas into manifest reality than we are dropping tons of ultra pure water down the bottom of a mine shaft and looking for sparks. We have been doing that for years already, and other than the oddball neutrino or cosmic ray reaction the elusive dark particles have yet to be observed, so we stare at nothing, we already know everything there is to know about that tank under that mile of solid rock.
But out there. Out there we don’t know anything. No matter what happens we learn, we discover, we push ourselves until we know something we didn’t if we go out there and try to map the local neighborhood. Maybe we can’t prove Milgrom’s law by making a detailed survey of the Oort cloud but we can become much more well acquainted with our local gravitational environment, and we will certainly put new constraints on a variety of already accepted theories.
If we find Oort cloud objects orbit faster than what relativity predicts for them we will have opened a new chapter in the story of scientific exploration and expanded our understanding the universe we observe, if we don’t, we will still have pushed ourselves to new limits of exploration, ideas and technology. Exactly the way Kennedy said we would if we accept the challenge, we refuse to postpone it, and we rise to meet it as we have done, so very many times before…