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...objects in [[Outer space|space]]. No one method works for all objects and distances, so astronomers use a number of methods. ...the problem. Several methods rely on a '''standard candle''', which is an astronomical object that has a known standard [[luminosity]]. ...

...t with respect to the Earth. While angles and relative sizes are to scale, distances are not. ...}km.<ref name="Seidelmann">{{Citation |title=Explanatory Supplement to the Astronomical Almanac |pages=696, 701 |year=1992 |editor-last=Seidelmann |editor-first=P. ...

...Barnard | year=1916| title=A small star with large proper motion| journal=Astronomical Journal | volume=29 | issue=695| page=181 | bibcode = 1916AJ.....29..181B| ...ive.org/details/sim_astronomical-journal_2004-05_127_5/page/2909 | journal=Astronomical Journal | volume=127 | issue=5| page=2909 | doi= 10.1086/383289 | bibcode = ...

The main challenge facing interstellar travel is the vast distances that have to be covered. This means that a very great speed and/or a very l ...f spacetime and gravity: the hard problem of interstellar travel| journal =Astronomical Review| volume =7| issue =2| page =5| doi =10.1080/21672857.2012.11519699| ...

...ime]] itself will be torn apart by the [[expansion of the universe]] until distances between [[Particle|particles]] will become [[Infinity|infinite.]] According ...e "Big Rip", in which the observable universe will reach zero size and all distances will reach into infinite value. ...

([[Astronomical unit|AU]]) ...4 |s2cid=11492499 }}</ref> This means that planets orbiting between these distances could be the right temperature to let [[organic chemistry|organic life]] (l ...

Ole Christensen Rømer used an astronomical measurement to make the first quantitative estimate of the speed of light.< ...ned. {{As of|2009}}, the best estimate, as approved by the [[International Astronomical Union]] (IAU), is:<ref name="Pitjeva09"> ...

* [[Gold Medal of the Royal Astronomical Society]] (1926) ...for [[cosmology]] (theories of the structure of our [[universe]] at large distances and over long times). Einstein thought that the universe may curve a little ...

| The length of the [[Julian day|day used for astronomical timekeeping]] reaches about 86,401 [[International System of Units|SI]] sec |journal= [[Monthly Notices of the Royal Astronomical Society]] ...