space exploration

Destination: Titan



“This volume is a compendium of six works that includes Latin translations of portions of the Zīj-i Sulṭānī by Muḥammad Ṭaraghāy ibn Shāhrukh ibn Tīmūr (1394–1449), known as Ulugh Beg. The other works include an excerpt from the Taqwīm al-Buldān (entitled “A Description of Khwārazm and Transoxiana from the Tables of Abū al-Fidāʾ”) by Abū al-Fidāʾ Ismāʿīl Ibn ʿAlī (1273-1331), and a star table by Muhammad ibn Muhammad Tizīnī. Ulugh Beg (“Great Commander” in Turkish) was a grandson of Tīmūr (known in the West as Tamerlane) and the governor of Transoxiana. In the brief period following the death, in 1447, of his father, Shāhrukh ibn Tīmūr, Ulugh Beg was sultan of the Tīmūrid realms. He is known as a patron of poetry, literature, and especially of architecture. He built madrasahs in Bukhara and in his capital city of Samarqand, both of which were supported by substantial waqfs (religious endowments). His other building projects included those at Gur-Emir, Shahrisabz, and Shah-i Zindah. His most famous act of patronage, however, was the building, in circa 1420, of the observatory at Samarqand, of which he also served as director. There he assembled a large number of scientists, the most famous of whom were the renowned astronomer Jamshīd ibn Masʻūd Kāshī and the head professor in Ulugh Beg’s madrasah, Mūsá ibn Muḥammad Qāḍīʹzādah. The observational program was led by Kāshī and Qāḍīzāda until their deaths (Kāshi in 1429 and Qāḍīzāda in 1436).

The astronomical observations were continued under ʻAlī Qūshchī, a student of Qāḍīzāda and Ulugh Beg. Ulugh Beg completed his astronomical tables, the Zīj al-Sulṭānī or Zīj-i Ulugh Beg, in about 1441. Based largely on observations carried out at his observatory, this work became the standard star table well into the following century. The sections from the Zīj-i Ulugh Beg included in this book were translated by John Greaves (1602–52) and Thomas Hyde (1636–1703) and printed at the Oxford University Press in London in 1655. Greaves was an English mathematician, astronomer, orientalist and antiquary. Hyde was professor of Arabic and Persian and Bodley’s librarian at Oxford.”



One of the challenges faced by astrophysicists is that you can’t repeat your experiments.  If you observe a supernova explosion, you can’t put the star back together and watch it explode again. We can watch other stars explode, and from these combined observations we can gain a deeper understanding of just how stars explode, but a single star explodes only once.  With cosmology, that poses a particular challenge because we only have one observable universe. Not only can’t we repeat the experiment, we only have one experiment to observe.  What we can do, however, is simulate the universe and see how it compares to the real one. Recently a team did just that, making the most extensive computational simulation of the universe thus far.  The results were published in Nature, but you can see a summary of the simulation in the video.  The team started with an initial state representing the universe only 12 million years old (before any stars or galaxies had formed) and 350 million light years wide. The then simulated cosmic evolution over 13 billion years.  This included not only the effects of gravity, dark matter and dark energy, but also effects such as active galactic nuclei and the enrichment of elements. The simulation produces a range of galaxy types consistent with our own universe, as well as a cosmic structure that matches our own. The simulation wasn’t perfect, and some discrepancies with our universe appeared, such as the formation of low mass galaxies earlier than is observed in our universe. Still, it is a clear demonstration that the ΛCDM cosmic model (that of a universe with matter, dark matter and dark energy) is an accurate model of our universe. Paper: M. Vogelsberger, et al. Properties of galaxies reproduced by a hydrodynamic simulation. Nature 509, 177–182 (2014)