Hebrews 1:2 - through whom also he made the universe?

 Hebrews 1:2 (KJV)  Hath in these last days spoken unto us by his Son, whom he hath appointed heir of all things, by whom also he made the worlds;

Worlds is really not a great translation. It should be ages. It's the word aionas, from aion where we get our English word aeon from, which means age or era.

165. aión ►
Strong's Concordance
aión: a space of time, an age
Original Word: αἰών, ῶνος, ὁ
Part of Speech: Noun, Masculine
Transliteration: aión
Phonetic Spelling: (ahee-ohn')
Definition: a space of time, an age
Usage: an age, a cycle (of time), especially of the present age as contrasted with the future age, and of one of a series of ages stretching to infinity. Its a time frame.

Word Origin
from a prim. root appar. mean. continued duration
Definition
a space of time, an age
NASB Translation
age (20), ages (6), ancient time (1), beginning of time (1), course (1), eternal (2), eternity (1), ever* (2), forever (27), forever and ever (20), forevermore (2), long ago (1), never* (1), old (1), time (1), world (7), worlds (1).

Here's the literal translation...

Young's Literal Translation
in these last days did speak to us in a Son, whom He appointed heir of all things, through whom also He did make the ages;

So,  God made the ages through Christ. This is talking about the risen Jesus, exalted and sitting at the right hand of the Father as God's appointed Lord over the heavens and earth.

Observe the below parallel verses that use the same word aion, age.

Ephesians 3:10-11 (Young's Literal Translation)
...that there might be made known now to the principalities and the authorities in the heavenly places, through the assembly, the manifold wisdom of God, according to a purpose of the ages (aiōnōn), which He made in Christ Jesus our Lord,

Hebrews 6:4-5 (New International Version)
It is impossible for those who have once been enlightened, who have tasted the heavenly gift, who have shared in the Holy Spirit, who have tasted the goodness of the word of God and the powers of the coming age (aiōnos).

Ephesians 1:20-22 (NIV)
...when he raised Christ from the dead and seated him at his right hand in the heavenly realms, far above all rule and authority, power and dominion, and every name that is invoked, not only in the present age (aiōni) ibut also in the one to come. And God placed all things under his feet and appointed him to be head over everything for the church

Heb 1:2-3 is not about the genesis creation. It's about the man Jesus, risen.... made superior to angels by his God, and upholding the ages by the word of God's power.