This problem can combat a problem advocate, why do we see a lot of time 100000000 need besides 10 billion light-year? Problem advocate should know light-year is length unit, the distance that advances in the time that 10 billion light-year represents to light is in 10 billion years. Problem advocate since celestial body is apart from us,the likelihood thinks 10 billion light-year, our " the line of sight " the time that needs 10 billion years flies to this celestial bodies, see celestial body next. In fact, this kind of understanding is wrong completely, the light that sees because the object is given out,the essence of the object is or catoptric is smooth by binoculars or the eye is caught, undertake smooth signal resembling again next, such our ability see an object. Breath out suddenly aerospace binoculars to want to aim a sky only can observation reachs distant place, even besides 100 light-year, this is the light that gives out before 10 billion years because of celestial body has reached the earth through trudge. Nevertheless, the light that so distant celestial body place gives out is very faint, binoculars of haing suddenly aerospace needs to be as long as the ability of time of exposure of a few months gathers enough much light undertakes resembling.
Because the universe is expanding, according to Ha Bo constant is 70 (kilometre / second) / 1 million parsec have consideration, be apart from us the celestial body place of 10 billion light-year provides some to retreat a speed to be 215 thousand kilometre / second, 71.6% what reached velocity of light. The time ability transmission that the light that at present the celestial body place of 10 billion light-year gives out distance earth needs to exceed 100 many years arrives on the earth, because the space is in,this is outspread, light goes celestial body to the distance between the earth more than 10 billion light-year.
And the celestial bodies that exceeds 14 billion light-year to the distance, the speed that be far from the earth as a result of them and goes is more than velocity of light, the Guang Yongyuan that so they give out now also does not take celestial body to the distance between the earth, this means us to also cannot see those distant celestial body forever. Nevertheless, these distant celestial bodies still can reach the earth in the light that gave out in the past, so we can see the look that they go only, and cannot see now and prospective appearance.
