CoachThe density-wave theory explains spiral arms as a wave of higher density in a disc, a spiral pattern that turns rigidly at its own angular speed, the pattern speed, while the stars and the gas move through it, slowing as they enter the crowded arm and speeding up as they leave, as cars move through a traffic jam.
বইগুলো এখনো বাংলা ভাষায় পাওয়া যায় না — ইংরেজি সংস্করণ দেখানো হচ্ছে।
Earth and Space Sciences · পরিভাষা