class Moment
  include Mongoid::Document

  field :location, type: Array

  index({ location: "2dsphere" }, background: true)

  scope :near_by, lambda {|location, distance| geo_near(location).spherical.distance_multiplier(6371.39).max_distance(distance / 6371.39)}
end

Moment.near_by([ 51.545099, -0.0106 ], 1.083).each {|a| p a}
NoMethodError: undefined method `to_criteria' for #<Mongoid::Contextual::GeoNear:0x007f84a71cb550>