If I may intercede, Baha'is and Christians believe differently about the new Earth and how it will be established.
Baha'is believe that the new Earth will be established in the present age, which began with the return of Christ in the mid 19th century.
After the return of Christ the process of building the New Earth was set in motion..
The new Earth does not refer to a new physical earth, it refers to a new Earth of people who will be more spiritual.
The new Earth it will be established by people working together to build it with the assistance of God.
“Beseech ye the one true God to grant that all men may be graciously assisted to fulfil that which is acceptable in Our sight.
Soon will the present-day order be rolled up, and a new one spread out in its stead. Verily, thy Lord speaketh the truth, and is the Knower of things unseen.”
(Gleanings From the Writings of Bahá’u’lláh, pp. 6- 7)
Baha'is believe that the new Earth is a new world order in which we will see the spiritualization of the peoples of the world and man will become a noble being adorned with divine virtues and perfections.
You asked what will happen to the old Earth. The old physical Earth will still remain as always but the old systems will be replaced by new systems.
Baha'is refer to that as the New world order.
The “World Order” that Baha’is envision pertains to a number of subjects: politics and governance, economics, society, and religion, as is covered briefly in this blog:
If you have spent a considerable amount of time reading the Writings of the Baha'i Faith, it is likely that you have come across language regarding the relationship between the Faith and a new “World Order.” One of the passages that is most frequently quoted in relation to this theme is this...
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