Q: How come the creatures on other inhabited planets know of us and even refer to our planet as the planet of the cross while we have no idea of them?
A: Thanks for this question.
Well, we do have some idea of these other planets since receiving The Urantia Book, but you are right. We do not know of these other planets as they know of us. They know enough about us to know what has happened here—that Christ Michael of Nebadon incarnated here as a mortal of the realm and died here on a cross. We only know that there are many other planets "out there" who know of us as "the world of the cross." We are told something of these other planets in The Urantia Book, but precious little, really; only enough to know that we are pretty backward in comparison.
(188:4.1) It is a fact that Urantia has become known among other neighboring inhabited planets as the “world of the cross.”
The reason for this lack of knowledge on our part is due to the Lucifer rebellion, and our one-time Planetary Prince's participation in it. Once Caligastia threw his support behind Lucifer's efforts to unseat the Father's rule, our planet—and our whole system—was placed under "spiritual quarantine;" in other words, we were isolated from the rest of the planetary systems, so as not to allow the rebellion to spread unchecked. It is like what happens when a person comes down with a contagious disease. That person is placed under quarantine and isolated from the rest of the population until they get well, or else many, many people might also contract the same disease.
From The Urantia Book :
As to why we are able to know little or nothing of other worlds, even with the Urantia revelation:
(67:3.1) The outbreak of rebellion on Jerusem, the capital of Satania, was broadcast by the Melchizedek council. The emergency Melchizedeks were immediately dispatched to Jerusem, and Gabriel volunteered to act as the representative of the Creator Son, whose authority had been challenged. With this broadcast of the fact of rebellion in Satania the system was isolated, quarantined, from her sister systems. There was "war in heaven, " the headquarters of Satania, and it spread to every planet in the local system.
And why other planets (not under quarantine) know so much about us:
(50:6.1) The isolation of Urantia renders it impossible to undertake the presentation of many details of the life and environment of your Satania neighbors. In these presentations we are limited by the planetary quarantine and by the system isolation. We must be guided by these restrictions in all our efforts to enlighten Urantia mortals, but in so far as is permissible, you have been instructed in the progress of an average evolutionary world, and you are able to compare such a world's career with the present state of Urantia.
So, the other planets receive broadcasts informing them of the goings-on around the universe. We here on Urantia are denied such broadcasts.
(33:6.5) From Salvington, broadcasts are simultaneously directed to the constellation headquarters, the system headquarters, and to individual planets. All higher orders of celestial beings are able to utilize this service for communication with their fellows scattered throughout the universe. The universe broadcast is extended to all inhabited worlds regardless of their spiritual status. Planetary intercommunication is denied only those worlds under spiritual quarantine.
Even Jesus terrible death on the cross was broadcast to the universe:
But, there is a silver lining to all of this dreary news, and we find words of comfort here:
(187:6.3) Thus ended a day of tragedy and sorrow for a vast universe whose myriads of intelligences had shuddered at the shocking spectacle of the crucifixion of the human incarnation of their beloved Sovereign; they were stunned by this exhibition of mortal callousness and human perversity.
(50:7.1) On first thought it might appear that Urantia and its associated isolated worlds are most unfortunate in being deprived of the beneficent presence and influence of such superhuman personalities as a Planetary Prince and a Material Son and Daughter. But isolation of these spheres affords their races a unique opportunity for the exercise of faith and for the development of a peculiar quality of confidence in cosmic reliability which is not dependent on sight or any other material consideration. It may turn out, eventually, that mortal creatures hailing from the worlds quarantined in consequence of rebellion are extremely fortunate. We have discovered that such ascenders are very early intrusted with numerous special assignments to cosmic undertakings where unquestioned faith and sublime confidence are essential to achievement.
On Jerusem the ascenders from these isolated worlds occupy a residential sector by themselves and are known as the agondonters, meaning evolutionary will creatures who can believe without seeing, persevere when isolated, and triumph over insuperable difficulties even when alone. This functional grouping of the agondonters persists throughout the ascension of the local universe and the traversal of the superuniverse; it disappears during the sojourn in Havona but promptly reappears upon the attainment of Paradise and definitely persists in the Corps of the Mortal Finality
We here on Urantia are still in the process of getting well from the effects of our terrible disease of rebellion. One hopes that in the not-too-distant future, we will once more be reconnected to the system circuits. But in the meantime, we must soldier on as agondonters, with our indwelling adjusters and living faith to guide our way. We have also been blessed by the revelation of The Urantia Book, and in time, its truths will seep into humanity's spiritual consciousness to lead us into a new age of spiritual evolution. In time, our quarantine will be lifted...
(108:4.4) When a world is isolated by rebellion, when a planet is cut off from all outside encircuited communication, as was Urantia after the Caligastia upheaval, aside from personal messengers there remains but one possibility of direct interplanetary or universe communication, and that is through the liaison of the Adjusters of the spheres. No matter what happens on a world or in a universe, the Adjusters are never directly concerned. The isolation of a planet in no way affects the Adjusters and their ability to communicate with any part of the local universe, superuniverse, or the central universe. And this is the reason why contacts with the supreme and the self-acting Adjusters of the reserve corps of destiny are so frequently made on quarantined worlds. Recourse is had to such a technique as a means of circumventing the handicaps of planetary isolation.
Thanks again for this great question! Please click on any of the links to find out much more about all of these issues of quarantine and isolation.