copes is al a premium and orically measuring red ss ably costly in telescope time. It could take all nigo get a single exposure. Inconsequence, astronomers imes been compelled (or o base conclusionson notably scanty evidence. In cosmology, as t Geoffrey Carr ed,  on a molein Rees  it:

    “Our present satisfaction [ate of understanding] may reflect ty of taratheory.”

    tainty applies, incidentally, to relatively nearby to tantedges of tes,  t-years a do not often stress to t it is someitled to  exactly by quot;a constant of 50quot; or quot;a constant of 100.quot; tronomical units of measure. Except conversationally, astronomers dont use ligance called traction of parallax and second), based on a universal measure called tellar parallax and equivalent to 3.26 ligant is expressed in terms of kilometers per second per megaparsec.

    tronomers refer to a ant of 50, ;50 kilometers per second permegaparsec.quot; For most of us t is of course an utterly meaningless measure, but tronomicalmeasures most distances are so o be utterly meaningless.

    quite t large, matters are naturally magnified. Bearing allt in mind, t bets to be fixed on a range ofabout 12 billion to 13.5 billion years, but y.

    One interesting recently suggested t t nearly as big as , t ance some of tions, g images created by rebounded light.

    t is, t deal, even at quite a fundamental level, t  knoleast ists calculate t of matter needed toogetely s. It appears t at least 90 percentof t, is