Science Reference Guide for Hollow Earth Theories.
And let us not forget Admiral Byrd Admiral Byrd Expedition
In 1964, Raymond W. Bernard, an esotericist and leader of the Rosicrucians published The Hollow Earth – The Greatest Geographical Discovery in History Made by Admiral Richard E. Byrd in the Mysterious Land Beyond the Poles – The True Origin of the Flying Saucers.
Admiral Richard E. Byrd of the United States Navy flew to the North Pole in 1926 and over the South Pole in 1929.
In his diary, he tells of entering the hollow interior of the earth, along with others and traveling 17 miles over mountains, lakes, rivers, green vegetation, and animal life. He tells of seeing tremendous animals—resembling the mammoths of antiquity moving—through the brush. He eventually found cities and a thriving civilization. The external temperature was 74 degress F.
His airplane was greeted by flying machines of a type he had never seen before. They escorted him to a safe landing area where he was graciously greeted by emissaries from Agartha. After resting, he and his crew, were taken to meet the king and queen of Agartha. They told him that he had been allowed to enter Agartha because of his high moral and ethical character. They went on to say that they worried about the safety of planet due to he bombs and other testing done above the surface by goverments. After the visit Byrd and his crew were guided back to the surface of the planet.
In January of 1956 Admiral Byrd led an expedition to the South Pole. On that expedition he and his crew penetrated down 2,300 miles into the center of the earth. Admiral Byrd stated that the North and South Poles are only two of many openings into the center of the Earth. He wrote about seeing a sun below the Earth.