Different religions have different myths or stories about how the world was made. Guru Ji questions whether these are really truthful.

"What was that season, and what was that month, when the Universe was created?
The Pandits, the religious scholars, cannot find that time, even if it is written in the Puraanas.
That time is not known to the Qazis, who study the Koran.
The day and the date are not known to the Yogis, nor is the month or the season.
The Creator who created this creation—only He Himself knows.
How can we speak of Him? How can we praise Him?
How can we describe Him? How can we know Him?
O Nanak, everyone speaks of Him, each one wiser than the rest.
Great is the Master, Great is His Name. Whatever happens is according to His Will.
O Nanak, one who claims to know everything shall not be decorated in the world hereafter. || 21 ||
There are nether worlds beneath nether worlds, and hundreds of thousands of heavenly worlds above.
The Vedas say that you can search and search for them all, until you grow weary.
The scriptures say that there are 18,000 worlds, but in reality, there is only One Universe.
If you try to write an account of this, you will surely finish yourself before you finish writing it.
O Nanak, call Him Great! He Himself knows Himself. || 22 ||" (page 4-5)

Guru Ji tells us that there are millions of worlds and universes, but most interestingly, these are all controlled by One God. The most cutting edge scientific theory we have today is called string theory. Everything we see is really energy and is therefore unified. Gurbani tells us that really, at the heart of all being, is God Himself.

Everything is strung on His string. He is contained in each and every heart. || 2 (page 387)

Also, we have another verse,

You are the Creator; all is created by You. Without You, there is no other at all.
You alone, God, are in the beginning, the middle and the end.
You are the root of the entire expanse. || 14 || (page 1079)

With regard to the beginning of creation, we have a whole hymn.

MARU, FIRST MEHL:
For countless ages, there was only total darkness.
There was no earth or sky; there was only the infinite Command of His Law.
There was no day or night, no moon or sun; God sat in primal, profound Samaadhi. || 1 ||
There were no sources of creation or powers of speech, no air or water.
There was no creation or destruction, no coming or going.
There were no continents, nether regions, seven seas, rivers or flowing water. || 2 ||
There were no heavenly realms, earth or nether regions of the underworld.
There was no heaven or hell, no death or time.
There was no hell or heaven, no birth or death, no coming or going in reincarnation. || 3 ||
There was no Brahma, Vishnu or Shiva. No one was seen, except the One Lord.
There was no female or male, no social class or caste of birth; no one experienced pain or pleasure. || 4 ||
There were no people of celibacy or charity; no one lived in the forests.
There were no Siddhas or seekers, no one living in peace.
There were no Yogis, no wandering pilgrims, no religious robes; no one called himself the master. || 5 ||
There was no chanting or meditation, no self- discipline, fasting or worship.
No one spoke or talked in duality. He created Himself, and rejoiced; He evaluates Himself. || 6 ||
There was no purification, no self-restraint, no malas of basil seeds.
There were no Gopis, no Krishna, no cows or cowherds.
There were no tantras, no mantras and no hypocrisy; no one played the flute. || 7 ||
There was no karma, no Dharma, no buzzing fly of Maya.
Social class and birth were not seen with any eyes.
There was no noose of attachment, no death inscribed upon the forehead; no one meditated on anything. || 8 ||
There was no slander, no seed, no soul and no life. There was no Gorakh and no Maachhindra.
There was no spiritual wisdom or meditation, no ancestry or creation, no reckoning of accounts. || 9 ||
There were no castes or social classes, no religious robes, no Brahmin or Kh'shaatriya.
There were no demi-gods or temples, no cows or Gaayatri prayer.
There were no burnt offerings, no ceremonial feasts, no cleansing rituals at sacred shrines of pilgrimage; no one worshipped in adoration. || 10 ||
There was no Mullah, there was no Qazi. There was no Shaykh, or pilgrims to Mecca.
There was no king or subjects, and no worldly egotism; no one spoke of himself. || 11 ||
There was no love or devotion, no Shiva or Shakti — no energy or matter.
There were no friends or companions, no semen or blood.
He Himself is the banker, and He Himself is the merchant.
Such is the Pleasure of the Will of the True Lord. || 12 ||
There were no Vedas, Korans or Bibles, no Simritees or Shaastras.
There was no recitation of the Puraanas, no sunrise or sunset.
The Unfathomable Lord Himself was the speaker and the preacher; the unseen Lord Himself saw everything. || 13 ||
When He so willed, He created the world.
Without any supporting power, He sustained the universe.
He created Brahma, Vishnu and Shiva; He fostered enticement and attachment to Maya. || 14 ||
How rare is that person who listens to the Word of the Guru's Shabad.
He created the creation, and watches over it; the Hukam of His Command is over all.
He formed the planets, solar systems and nether regions, and brought what was hidden to manifestation. || 15 ||
No one knows His limits. This understanding comes from the Perfect Guru.
O Nanak, those who are attuned to the Truth are wonderstruck; singing His Glorious Praises, they are filled with wonder. || 16 || 3 || 15 || (page 1035-6)

All things were united in God. Then God gave all beings a chance and so created the creation. As God remains the heart-beat and life- support of the universe, guiding it as the Inner Tutor in each heart, there is a unity of being, a unity of Creator and creation, as well as the separation which gives us the chance to live. Another hymn focuses on creation as a unique choices, which we can use or waste. This hymn tells us stuff about human birth.

MARU, FIRST MEHL:
For many ages, only darkness prevailed; the infinite, endless Lord was absorbed in the primal void.
He sat alone and unaffected in absolute darkness; the world of conflict did not exist. || 1 ||
Thirty-six ages passed like this. He causes all to happen by the Pleasure of His Will.
No rival of His can be seen. He Himself is infinite and endless. || 2 ||
God is hidden throughout the four ages — understand this well.
He pervades each and every heart, and is contained within the belly.
The One and Only Lord prevails throughout the ages.
How rare are those who contemplate the Guru, and understand this. || 3 ||
From the union of the sperm and the egg, the body was formed.
From the union of air, water and fire, the soul is made.
He Himself plays joyfully in the mansion of the body; all the rest is just attachment to Maya's expanse. || 4 ||
Within the mother's womb, upside-down, the mortal meditated on God.
The Inner-knower, the Searcher of hearts, knows everything.
With each and every breath, he contemplated the True Name, deep within himself, within the womb. || 5 ||
He came into the world to obtain the four great blessings.
He came to dwell in the home of the Shiva and Shakti, energy and matter.
But he forgot the One Lord, and he has lost the game.
The blind person forgets the Naam, the Name of the Lord. || 6 ||
The child dies in his childish games.
They cry and mourn, saying that he was such a playful child.
The Lord who owns him has taken him back. Those who weep and mourn are mistaken. || 7 ||
What can they do, if he dies in his youth?
They cry out, "His is mine, he is mine!" They cry for the sake of Maya, and are ruined; their lives in this world are cursed. || 8 ||
Their black hair eventually turns grey. Without the Name, they lose their wealth, and then leave.
They are evil-minded and blind — they are totally ruined; they are plundered, and cry out in pain. || 9 ||
One who understands himself, does not cry. When he meets the True Guru, then he understands.
Without the Guru, the heavy, hard doors are not opened.
Obtaining the Word of the Shabad, one is emancipated. || 10 ||
The body grows old, and is beaten out of shape.
But he does not meditate on the Lord, His only friend, even at the end.
Forgetting the Naam, the Name of the Lord, he departs with his face blackened.
The false are humiliated in the Court of the Lord. || 11 ||
Forgetting the Naam, the false ones depart. Coming and going, dust falls on their heads.
The soul-bride finds no home in her in-laws' home, the world hereafter; she suffers in agony in this world of her parents' home. || 12 ||
She eats, dresses and plays joyfully, but without loving devotional worship of the Lord, she dies uselessly.
One who does not distinguish between good and evil, is beaten by the Messenger of Death; how can anyone escape this? || 13 ||
One who realizes what he has to possess, and what he has to abandon, associating with the Guru, comes to know the Word of the Shabad, within the home of his own self.
Do not call anyone else bad; follow this way of life.
Those who are true are judged to be genuine by the True Lord. || 14 ||
Without Truth, no one succeeds in the Court of the Lord.
Through the True Shabad, one is robed in honor.
He forgives those with whom He is pleased; they silence their egotism and pride. || 15 ||
One who realizes the Hukam of God's Command, by the Grace of the Guru, comes to know the lifestyle of the ages.
O Nanak, chant the Naam, and cross over to the other side.
The True Lord will carry you across. || 16 || 1 || 7 || (1026-7)