Aliens: Possibility and Science

 

Although no conclusive evidence of life has yet been found on any planet or moon beyond Earth, many people believe that life exists on other worlds and that such beings are more advanced than humans. In ancient folklore, the arrival on Earth of various creatures from other planets and stars was treated as an entirely natural occurrence. Those imaginative stories have been recast with scientific elements in modern science fiction. Many people, however, regard the aliens of science fiction as real. Although the literal meaning of the word “alien” is “a person from another country,” in common usage it has come to mean a living being from another planet.

White Holes – Theoretical Foundations and Evolution

 

Many of us are familiar with black holes. We know that when a star with a mass more than three times that of our Sun dies, it keeps collapsing under its own gravitational pull and eventually turns into a black hole. Professor Jamal Nazrul Islam defined a black hole in his famous book Black Hole in the following way:

“If the mass of a star exceeds three times the mass of the Sun, the Fermi pressure of neutrons and other

শ্বেতবিবর: তাত্ত্বিক ভিত্তি ও ক্রমবিকাশ

 

ব্ল্যাকহোল বা কৃষ্ণবিবর সম্পর্কে আমাদের অনেকেরই ধারণা আছে। আমরা জানি যে আমাদের সূর্যের ভরের তিনগুণেরও বেশি ভরবিশিষ্ট নক্ষত্রের মৃত্যু হলে তা অভিকর্ষণ বলের টানে সংকুচিত হতে হতে ব্ল্যাকহোল বা কৃষ্ণবিবরে পরিণত হয়। প্রফেসর জামাল নজরুল ইসলাম তাঁর বিখ্যাত ‘কৃষ্ণবিবর’ বইতে ব্ল্যাকহোলের সংজ্ঞা দিয়েছেন এভাবে, “একটি নক্ষত্রের ভর সূর্যের ভরের তিন গুণের বেশি হলে নিউট্রনের ফার্মি চাপ এবং অন্যান্য বহির্মুখী চাপ অন্তর্মুখী মাধ্যাকর্ষণ বল সামলাতে পারে না। তাই

Carl Sagan: the great hero of space

 

By presenting science in language easily understandable to ordinary people, Carl Sagan played a leading role in making science popular — he was one of the brightest among such scientists. Time magazine described him as America’s most successful science communicator. Among world-renowned scientists, only a handful have, alongside complex and rigorous scientific research, also written about science in simple language for the public. Carl Sagan was one of those few — in addition to publishing