"Blessed is He in Whose hand is the Sovereignty, and, He is Able to do all things. (1) Who hath created life and death that He may try you which of you is best in conduct; and He is the Mighty, the Forgiving, (2) Who hath created seven heavens in harmony. Thou canst see no fault in the Beneficent One's creation; then look again: Canst thou see any rifts? (3) Then look again and yet again, thy sight will return unto thee weakened and made dim. (4) And verily We have beautified the world's heaven with lamps, and We have made them missiles for the devils, and for them We have prepared the doom of flame. (5)" Al-Mulk 67:1-5

وہ (خدا) جس کے ہاتھ میں بادشاہی ہے بڑی برکت والا ہے۔ اور وہ ہر چیز پر قادر ہے (۱) اسی نے موت اور زندگی کو پیدا کیا تاکہ تمہاری آزمائش کرے کہ تم میں کون اچھے عمل کرتا ہے۔ اور وہ زبردست (اور) بخشنے والا ہے (۲) اس نے سات آسمان اوپر تلے بنائے۔ (اے دیکھنے والے) کیا تو (خدا) رحمٰن کی آفرنیش میں کچھ نقص دیکھتا ہے؟ ذرا آنکھ اٹھا کر دیکھ بھلا تجھ کو (آسمان میں) کوئی شکاف نظر آتا ہے؟ (۳) پھر دو بارہ (سہ بارہ) نظر کر، تو نظر (ہر بار) تیرے پاس ناکام اور تھک کر لوٹ آئے گی (۴)اور ہم نے قریب کے آسمان کو (تاروں کے) چراغوں سے زینت دی۔ اور ان کو شیطان کے مارنے کا آلہ بنایا اور ان کے لئے دہکتی آگ کا عذاب تیار کر رکھا ہے (۵)

Particle horizon of the observable universe
The particle horizon of the observable universe is the boundary that represents the maximum distance at which events can currently be observed. For events beyond that distance, light has not had time to reach our location, even if it were emitted at the time the universe began. How the particle horizon changes with time depends on the nature of the expansion of the universe. If the expansion has certain characteristics, there are parts of the universe that will never be observable, no matter how long the observer waits for light from those regions to arrive. The boundary past which events cannot ever be observed is an event horizon, and it represents the maximum extent of the particle horizon.

The universe versus the observable universe

Some parts of the universe may simply be too far away for the light emitted from there at any moment since the Big Bang to have had enough time to reach Earth at present, so these portions of the universe would currently lie outside the observable universe.

In the future the light from distant galaxies will have had more time to travel, so some regions not currently observable will become observable in the future. However, due to Hubble's law regions sufficiently distant from us are expanding away from us much faster than the speed of light (special relativity prevents nearby objects in the same local region from moving faster than the speed of light with respect to each other, but there is no such constraint for distant objects when the space between them is expanding; and the expansion rate appears to be accelerating due to dark energy. Assuming dark energy remains constant (an unchanging cosmological constant), so that the expansion rate of the universe continues to accelerate, there is a "future visibility limit" beyond which objects will never enter our observable universe at any time in the infinite future, because light emitted by objects outside that limit can never reach points that are expanding away from us at less than the speed of light (a subtlety here is that because the Hubble parameter is decreasing with time, there can be cases where a galaxy that is receding from us just a bit faster than light does manage to emit a signal which reaches us eventually).

This future visibility limit is calculated to be at a comoving distance (comoving distance is defined to be constant with time, unlike proper distance which is used to define recession velocity due to the expansion of space) of 19 billion parsecs (62 billion light years), which implies the number of galaxies that we can ever theoretically observe in the infinite future (leaving aside the issue that some may be impossible to observe in practice due to redshift, as discussed in the following paragraph) is only larger than the number currently observable by a factor of 2.36.

Though in principle more galaxies will become observable in the future, in practice an increasing number of galaxies will become extremely redshifted due to ongoing expansion, so much so that they will seem to disappear from view and become invisible.

An additional subtlety is that a galaxy at a given comoving distance is defined to lie within the "observable universe" if we can receive signals emitted by the galaxy at any age in its past history (say, a signal sent from the galaxy only 500 million years after the Big Bang), but because of the universe's expansion, there may be some later age at which a signal sent from the same galaxy will never be able to reach us at any point in the infinite future (so for example we might never see what the galaxy looked like 10 billion years after the Big Bang), even though it remains at the same comoving distance which is less than the comoving radius of the observable universe. This fact can be used to define a type of cosmic event horizon whose distance from us changes over time; for example, the current distance to this horizon is about 16 billion light years, meaning that a signal from an event happening at present would eventually be able to reach us in the future if the event was less than 16 billion light years away, but the signal would never reach us if the event was more than 16 billion light years away.

 

سُوۡرَةُ البَقَرَة
بِسۡمِ ٱللهِ ٱلرَّحۡمَـٰنِ ٱلرَّحِيمِ

ٱللَّهُ لَآ إِلَـٰهَ إِلَّا هُوَ ٱلۡحَىُّ ٱلۡقَيُّومُ‌ۚ لَا تَأۡخُذُهُ ۥ سِنَةٌ۬ وَلَا نَوۡمٌ۬‌ۚ لَّهُ ۥ مَا فِى ٱلسَّمَـٰوَٲتِ وَمَا فِى ٱلۡأَرۡضِ‌ۗ مَن ذَا ٱلَّذِى يَشۡفَعُ عِندَهُ ۥۤ إِلَّا بِإِذۡنِهِۦ‌ۚ يَعۡلَمُ مَا بَيۡنَ أَيۡدِيهِمۡ وَمَا خَلۡفَهُمۡ‌ۖ وَلَا يُحِيطُونَ بِشَىۡءٍ۬ مِّنۡ عِلۡمِهِۦۤ إِلَّا بِمَا شَآءَ‌ۚ وَسِعَ كُرۡسِيُّهُ ٱلسَّمَـٰوَٲتِ وَٱلۡأَرۡضَ‌ۖ وَلَا يَـُٔودُهُ ۥ حِفۡظُهُمَا‌ۚ وَهُوَ ٱلۡعَلِىُّ ٱلۡعَظِيمُ (٢٥٥)

2:255 Al-Baqara
Allah! There is no God save Him, the Alive, the Eternal. Neither slumber nor sleep overtaketh Him. Unto Him belongeth whatsoever is in the heavens and whatsoever is in the earth. Who is he that intercedeth with Him save by His leave? He knoweth that which is in front of them and that which is behind them, while they encompass nothing of His knowledge save what He will. His throne includeth the heavens and the earth, and He is never weary of preserving them. He is the Sublime, the Tremendous. (255)

خدا (وہ معبود برحق ہے کہ) اس کے سوا کوئی عبادت کے لائق نہیں زندہ ہمیشہ رہنے والا اسے نہ اونگھ آتی ہے نہ نیند جو کچھ آسمانوں میں اور جو کچھ زمین میں ہیں سب اسی کا ہے کون ہے جو اس کی اجازت کے بغیر اس سے (کسی کی) سفارش کر سکے جو کچھ لوگوں کے روبرو ہو رہا ہے اور جو کچھ ان کے پیچھے ہوچکا ہے اسے سب معلوم ہے اور وہ اس کی معلومات میں سے کسی چیز پر دسترس حاصل نہیں کر سکتے ہاں جس قدر وہ چاہتا ہے (اسی قدر معلوم کرا دیتا ہے) اس کی بادشاہی (اور علم) آسمان اور زمین سب پر حاوی ہے اور اسے ان کی حفاظت کچھ بھی دشوار نہیں وہ بڑا عالی رتبہ اور جلیل القدر ہے (۲۵۵)