Lord Kṛṣṇa instructs that all the planets within the material universe are destroyed at the end of 4,300,000 x 1,000 x 2 x 30 x 12 x 100 solar years. And all the living beings inhabiting these material planets are destroyed materially along with the destruction of the material worlds. The living entity, however, is constitutionally an antimaterial particle. But unless he elevates himself to the region of the antimaterial worlds by cultivation of antimaterial activities, he is destroyed materially at the annihilation of the material worlds and is subject to take rebirth in a material shape with the rebirth of a new material universe. In other words, he is subject to the pains of repeated birth and death. Only those living entities who take to the loving service of the Personality of Godhead during the manifested stage of material life are undoubtedly transferred to the antimaterial worlds after quitting the material body. Immortality is obtained only by those who return to Godhead by practice of antimaterial activities.
What are these antimaterial activities? They are medicines. For example, when a man falls ill, he goes to a physician who prescribes medicines which eventually cure the suffering patient. Similarly, the materialist is ailing, and he should consult an expert transcendentalist-physician. What is his ailment? He is suffering the tribulations of repeated births, deaths, diseases and old age. Once he agrees to put himself under the "back to Godhead" treatment, he is able to transfer himself to the antimaterial world, where there is eternal life instead of birth and death.