javascript - Infinite $digest loop in the rootScope

In the rootScope of my project i have defined a function that realizes an $http call.

angular.module('rsa',['ngRoute', 'ngCookies', 'ngMaterial'])
.config(function($routeProvider, $httpProvider){
    $routeProvider.when('/chapters', {
        ...
    });

    $routeProvider.when('/themes', {
       ...
    });

    // ... more routes

    $routeProvider.otherwise('/home');
  })
.controller(...)
.run(['$rootScope', 'UserService', '$location', '$cookies','$http', '$q', 
  function(rootScope, UserService, location, cookies, http, $q){
      rootScope.isAdmin = function(){
      return $http.get('/isAdmin').then(function(resp){...}, function(resp)
      {...})
   }
}])

rootScope's isAdmin method causes an infinite digest loop error.
Meanwhile, the same $http call (from isAdmin methods) works well inside other controllers.

I've read a little about what can be the problem and i found out that the $http service calls the $apply to force the $digest cycle but i don't understand what happens exactly with the $http service that drove me to get the following result in the console.

console

This is th html snippet:

 Administration 

Q1: Why is $http.get() causing an infinite number of $digest cycles.

Q2: Why does it only happen on rootScope and not in any other scope.

BTW xhr syncronous work fine and i am using angular 1.6.4