The earth is very old or recent; it does not matter.
What is important is that they misunderstood the word of God.
The earth was created in 6000 years: it means
the earth was transformed from a flaming sun to an earth with a cold crust within a period of 6000 of our years.
But when this transformation occurred? God only knows: it happened since long time: certainly more than 6000 years; but I think it is less than these billions of years.
God –be exalted –said also in the Quran 41: 9-12
قُلْ أَئِنَّكُمْ لَتَكْفُرُونَ بِالَّذِي خَلَقَ الْأَرْضَ فِي يَوْمَيْنِ وَتَجْعَلُونَ لَهُ أَندَادًا ذَلِكَ رَبُّ الْعَالَمِينَ . وَجَعَلَ فِيهَا رَوَاسِيَ مِن فَوْقِهَا وَبَارَكَ فِيهَا وَقَدَّرَ فِيهَا أَقْوَاتَهَا فِي أَرْبَعَةِ أَيَّامٍ سَوَاء لِّلسَّائِلِينَ . ثُمَّ اسْتَوَى إِلَى السَّمَاء وَهِيَ دُخَانٌ فَقَالَ لَهَا وَلِلْأَرْضِ اِئْتِيَا طَوْعًا أَوْ كَرْهًا قَالَتَا أَتَيْنَا طَائِعِينَ . فَقَضَاهُنَّ سَبْعَ سَمَاوَاتٍ فِي يَوْمَيْنِ...
The explanation:
( [O Mohammed] say [to the idolaters]: “Do you, then, disbelieve in [God] Who created the earth
in two days, and do you ascribe to Him opponents? –That is the Lord of [all] the worlds!”
“And He made [mountains] that landed upon it, blessed it, and apportioned therein its sustenance
in four days; alike for those who ask [provision.]”
“Then He tended to [build]
* the sky and it had been smoke; He said to it and to the earth, ‘Come, both of you, willingly or loath.’ The two said, ‘We [all] have come obedient.’
“And He separated them into seven firmaments
in two days …etc.” )
[
*i.e. to make the layers of the gaseous sky distinctive, and to build or to arrange it in successive layers.]
The interpretation:
>> (created the earth in two days) means: in two thousand years; for one day of God’s days equals one thousand of our years, according to our days,
as is it mentioned
in the Psalms 89: 3-4
“3… saying, “Return to dust, O sons of men.”
4 For a thousand years in your sight are like a day …”
The ‘creation’ is the transformation from one thing [or form] to another;
therefore, (Who created the earth in two days) means:
He transformed it into an earth after being a sun, and that lasted a period of two thousand years; this is the time during which the surface of that sun became cold, that sun whose life had ended.
>> (and He made [mountains] that landed upon it); that which heavily landed upon the earth, are the mountains. This can be explained as follows:
That sun had been transformed into an earth after the cooling of its surface, then the meteorites started to fall down on it to become the mountains. Therefore, most of the mountains on the earth surface were originally meteorites.
>> (and blessed it) means: He increased its size, and that was by many factors:
First: The crust of the earth started gradually to be more and more cold; so this increased its thickness.
Second: The falling down of meteorites upon it increased its mass and volume.
Third: The falling down of minute particles upon it (these are the fine particles that we see in a beam of sun rays entering a dark room through a window.) The origin of these particles are from meteorites which were broken up after their Doomsday, so that their parts scattered in the space.
Fourth: The metals increased its volume and size by combination with other elements, e.g. the oxygen may combine with iron, so it will increase in its volume, and ferric oxide will result; and carbon dioxide combines with calcium forming calcium carbonate; and nitrogen combines with sodium and potassium resulting in sodium nitrate and potassium nitrate; and so on gases combine with most of the metals so increasing their volume, and by this way the Earth size goes on increasing with the passing of time and years.
>> (and apportioned therein its sustenance) means: He made the fall of rain upon it, and created the plant, trees and animals; to be as sustenance and provision for man; in other words: He apportioned these things as sustenance for man when He would create him on Earth; because He –be exalted –had created these things and prepared them for man before did He create man upon it, exactly just as had He created the breast of the woman before did He create the fetus in her womb.
>> (in four days) means: He created all these things during a period of four thousand years; so
the total is six thousand years; because the cooling of the Earth lasted two thousand years,
as He said –be exalted –in the Quran 32: 4
اللَّهُ الَّذِي خَلَقَ السَّمَاوَاتِ وَالْأَرْضَ وَمَا بَيْنَهُمَا فِي سِتَّةِ أَيَّامٍ ثُمَّ اسْتَوَى عَلَى الْعَرْشِ...
The explanation:
(It is God Who created the heavens and the earth and that which is between them
in six [of the] days [of the Hereafter.] Then He mounted the throne …)
‘The heavens and the earth’ means the planets
The Universe and the Quran