Oge Ụwa

Oge terrestrial ( TT ) bụ ọkọlọtọ oge mbara igwe nke ọgbara ọhụrụ nke International Astronomical Union kọwapụtara, nke bụ isi maka nleba anya oge nke ndụ mbara igwe emere site na elu ụwa.  [1] ihe atụ, Almanac Astronomical na-eji TT maka nkọwa nke ọnọdụ ya ( ephemerides ) nke Sun, ọnwa na mbara ala dị ka ihe ngosi site na aṅụ.  Na ọrụ a, TT na-aga n'ihu n'oge Terrestrial Dynamical Time (TDT ma ọ bụ TD), [2] nke gara nke ọma oge ephemeris (ET) .  TT na-ekerịta mbụ e mere ET, ka ikpe onwe ya na iguzo iwu na ntụgharị nke ụwa .

Nkeji nke TT bụ SI nke abụọ, dabere ugbu a na elekere atomiki cesium, [1] mana adịghị TT n'onwe ya site na elekere atọ.  Ọ bụ echiche dị mma, na ezigbo elekere nwere ike were naanị ya.

TT dị iche n'usoro oge a na-dị ka ihe ndabere maka obodo, Oge Nchikota Universal Time (UTC).  TT bụ n'ụzọ doro anya ndabere nke UTC, site na International Atomic Time (TAI).  N'ihi isi ihe mere eme dị n'etiti TAI na ET mgbe TT mgbasa, TT bụ 32.184 s n'ihu TAI.

.International Astronomical Union (IAU) nakweere kaadị nke ọkọlọtọ oge terrestrial na 1976 na XVI General Assembly ma agbara Terrestrial Dynamical Time (TDT).  Ọ bụ ihe ibe ya na Barycentric Dynamical Time (TDB), nke bụ ikike oge maka ọmụmụ ephemerides, ka dabere n'ọtụtụ oge na-agbanwe agbanwe .  akpa oge a tụ ifụre nke onye nke ọma.  Ekwupụtakwara obi abụọ gbasara ihe 'dynamical' dị n'aha TDT