Black Friday: lifetime access is on a special offer in the app, until November 30. Black Friday: special offer on lifetime access, until November 30. Download
허블정수는 우주의 팽창 속도를 측정하는 데 사용됩니다.Heobeuljeongsuneun ujui paengchang sokdoreul cheugjeonghaneun de sayongdoemnida.Hubble's constant is used to measure the expansion rate of the universe.