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Sri Guru Granth Sahib Ji describes what was before creation:

ਅਰਬਦ ਨਰਬਦ ਧੁੰਧੂਕਾਰਾ ॥
ਧਰਣਿ ਨ ਗਗਨਾ ਹੁਕਮੁ ਅਪਾਰਾ ॥
ਨਾ ਦਿਨੁ ਰੈਨਿ ਨ ਚੰਦੁ ਨ ਸੂਰਜੁ ਸੁੰਨ ਸਮਾਧਿ ਲਗਾਇਦਾ ॥੧॥
"(Before the creation of the world) for endless eons, there was only utter darkness. There was no earth or sky; there was only the infinite Command of His Hukam. There was no day or night, no moon or sun; Vaheguru sat in primal, (like) in profound undisturbed meditation. ||1||"
(Ang 1035)

The universe did not come into existence by itself. The Creator created it:
ਸਾਚੇ ਤੇ ਪਵਨਾ ਭਇਆ ਪਵਨੈ ਤੇ ਜਲੁ ਹੋਇ ॥
ਜਲ ਤੇ ਤ੍ਰਿਭਵਣੁ ਸਾਜਿਆ ਘਟਿ ਘਟਿ ਜੋਤਿ ਸਮੋਇ ॥
ਨਿਰਮਲੁ ਮੈਲਾ ਨਾ ਥੀਐ ਸਬਦਿ ਰਤੇ ਪਤਿ ਹੋਇ ॥੩॥
“From the True Lord came the air (gases), and from the air came water. From water, He created the three worlds (metaphor or common term for the universe and all within); in each and every heart He has infused His Light. The Immaculate Lord does not become polluted. Attuned to the Shabad, honor is obtained. ||3||”
(Ang 19)

According to Sri Guru Granth Sahib jee the creation was manifested from the Sunn (void) in which the creator eternally existed:
ਸੁੰਨ ਕਲਾ ਅਪਰੰਪਰਿ ਧਾਰੀ ॥
ਆਪਿ ਨਿਰਾਲਮੁ ਅਪਰ ਅਪਾਰੀ ॥
ਆਪੇ ਕੁਦਰਤਿ ਕਰਿ ਕਰਿ ਦੇਖੈ ਸੁੰਨਹੁ ਸੁੰਨੁ ਉਪਾਇਦਾ ॥੧॥
ਪਉਣੁ ਪਾਣੀ ਸੁੰਨੈ ਤੇ ਸਾਜੇ ॥
ਸ੍ਰਿਸਟਿ ਉਪਾਇ ਕਾਇਆ ਗੜ ਰਾਜੇ ॥
ਅਗਨਿ ਪਾਣੀ ਜੀਉ ਜੋਤਿ ਤੁਮਾਰੀ ਸੁੰਨੇ ਕਲਾ ਰਹਾਇਦਾ ॥੨॥
“In the Primal Void, the Infinite Lord assumed His Power. He Himself is unattached, infinite and incomparable. He Himself exercised His Creative Power, and He gazes upon His creation; from the Primal Void, He formed the Void. ||1|| From this Primal Void, He fashioned air and water. He created the universe, and the king in the fortress of the body. Your Light pervades fire, water and souls; Your Power rests in the Primal Void. ||2||”
(Ang 1037)

There are three distinct functions that Vaheguru continually performs through his creation:
ਏਕਾ ਮਾਈ ਜੁਗਤਿ ਵਿਆਈ ਤਿਨਿ ਚੇਲੇ ਪਰਵਾਣੁ ॥
ਇਕੁ ਸੰਸਾਰੀ ਇਕੁ ਭੰਡਾਰੀ ਇਕੁ ਲਾਏ ਦੀਬਾਣੁ ॥
ਜਿਵ ਤਿਸੁ ਭਾਵੈ ਤਿਵੈ ਚਲਾਵੈ ਜਿਵ ਹੋਵੈ ਫੁਰਮਾਣੁ ॥
“Vaheguru, the One Divine Mother, emanated three functions. One, the Creator of the World; One, the Sustainer; and One, the Destroyer. He makes creation perform these functions to the Pleasure of His Will. Such is His Celestial Order.”
(Ang 7)

Guru Granth Sahib jee also tells us that the universe is not permanent:
ਨਿਸਿ ਬਾਸੁਰ ਨਖਿਅਤ੍ਰ ਬਿਨਾਸੀ ਰਵਿ ਸਸੀਅਰ ਬੇਨਾਧਾ ॥
ਗਿਰਿ ਬਸੁਧਾ ਜਲ ਪਵਨ ਜਾਇਗੋ ਇਕਿ ਸਾਧ ਬਚਨ ਅਟਲਾਧਾ ॥੧॥
"Night and day, and the stars in the sky shall vanish. The sun and the moon shall vanish. The mountains, the earth, the water and the air shall pass away. Only the Word of the Holy Saint shall endure. ||1||"
(Ang 1204)

ਮ: ੧ ॥
ਨ ਸੂਰ ਸਸਿ ਮੰਡਲੋ ॥ ਨ ਸਪਤ ਦੀਪ ਨਹ ਜਲੋ ॥
ਅੰਨ ਪਉਣ ਥਿਰੁ ਨ ਕੁਈ ॥ ਏਕੁ ਤੁਈ ਏਕੁ ਤੁਈ ॥੪॥
"Neither the sun, nor the moon, nor the planets, nor the seven continents, nor the oceans, nor food, nor the wind-nothing is permanent. You alone, Lord, You alone. ||4||"
(Ang 144)

Furthermore Sri Guru Granth Sahib jee tells us:
ਕਈ ਬਾਰ ਪਸਰਿਓ ਪਾਸਾਰ ॥
“Many times has the creation been created (the universe been created) and expanded.”
(Ang 276)

One question, which someone may ask, is “Who created the Creator?” To Guru jee tell us:
ਨਿਰਭਉ ਸੋ ਸਿਰਿ ਨਾਹੀ ਲੇਖਾ ॥
ਆਪਿ ਅਲੇਖੁ ਕੁਦਰਤਿ ਹੈ ਦੇਖਾ ॥
ਆਪਿ ਅਤੀਤੁ ਅਜੋਨੀ ਸੰਭਉ ਨਾਨਕ ਗੁਰਮਤਿ ਸੋ ਪਾਇਆ ॥੧੨॥
“Vaheguru alone is fearless, who has no destiny written on His head. God Himself is unseen; He reveals Himself through His wondrous creative power. He Himself is unattached, unborn and self-existent. O Nanak, through the Guru's Teachings, He is found. ||12||”
(Ang 1042)

Fundamentally, one must understand and accept that humans cannot understand the limits of God’s creative power, creation and wonder:
ਕੋਇ ਨ ਜਾਣੈ ਤੁਮਰੀ ਗਤਿ ਮਿਤਿ ਆਪਹਿ ਏਕ ਪਸਾਰਾ ॥
“No one knows Your state and extent. You alone created the expanse of the Universe.”
(Ang 1220)

ਨਾਨਕ ਕਰਤੇ ਕੀ ਜਾਨੈ ਕਰਤਾ ਰਚਨਾ ॥੨॥
“O Nanak, the Creator alone knows the workings of His creation. ||2||”
(Ang 275)

Thus it has been shown Sri Guru Granth Sahib Ji gives Sikhs an understanding of the creation of the world that is very scientific and matches the views of contemporary scientists.