How big is the universe?



How big is the universe?

No one knows how big the universe would be, as the light beyond the furthest and observable edge of the universe has yet to reach us. We can wonder if the universe is infinitely large, or if ours is the only universe out in the space. Astronomers have secondary evidence and some physical models to predict that the universe of galaxies spreads far beyond the region we can observe. How big this universe is and its billions of years of existence will blow our minds and imaginations!

The physical parameters of the observable universe can be estimated for its mass and size, assuming different types of materials fill it. The critical density of the universe is calculated to be 0.85×10−26kg/m3 (commonly quoted as about five hydrogen atoms per cubic meter)[1]. This density includes four significant types of energy/mass: ordinary matter (4.8%), neutrinos (0.1%), cold dark matter (26.8%), and dark energy (68.3%).[2] The density of ordinary matter, as measured by Planck, is 4.8% of the total critical density or 4.08×10−28kg/m3. To convert this density to mass we must multiply by volume, a value based on the radius of the “observable universe.” Since the universe has been expanding for 13.8 billion years, the comoving distance of the cosmological scale is now projected to about 46.6 billion light-years for the radius of the universe. Thus, volume (4πr3/3) equals 3.58×1080 m3 and the mass of ordinary matter equals density (4.08×10−28kg/m3) times volume (3.58×1080 m3) or 1.46×1053kg. Note that the average human weight is about 60kg or 6 ×101kg. Therefore, the weight ratio of a human to the observable universe is ~ 1/(2.43×1051).

For a mental model of shrinking the observable universe down to the weight scale of the Earth (5.972×1024kg), the weight of the human would appear to be in the order of a hydrogen atom (1.674 ×10-27kg), which is incredibly small in a microscopic view.

These calculations and mental models present us with the fact that humans are extremely small. We are negligible in terms of size, relative to the space beyond our Earth.



The New York Times published a press release in 2016 stating the number of galaxies in the universe is at least two trillion.[3] The scale of the universe, already unfathomable, just became even more so: there are about ten times as many galaxies as previously thought. The new number, two trillion galaxies, is the result of work led by Christopher J. Conselice, an astrophysicist at the University of Nottingham in England, published in The Astrophysical Journal[4]. Our Milky Way solar system, where humans live, is only one of the two trillion galaxies!

On the other hand, there are trillions of cells inside each human being. Each cell stores about three billion pairs of DNA that hold information for the development of physical structures in human beings. The latest research about the universe and human body is still in its infancy as it relates to understanding science and life. The evolution theory proposed by Darwin and others could not explain how the information inside the DNA became available at the beginning. The astounding discoveries of the vastness of this universe and the complication of the biology/chemistry/physics inside a human being open our eyes to the mysterious and marvelous works created by the wisest Creator.

Psalm 8, written about three thousand years ago, tells us the universal and amazing response to the vastness of the heaven and Earth. Lord, our Lord, how majestic is your name in all the earth!

You have set your glory in the heavens. Through the praise of children and infants you have established a stronghold against your enemies, to silence the foe and the avenger.

When I consider your heavens, the work of your fingers, the moon and the stars, which you have set in place, what is mankind that you are mindful of them, human beings that you care for them?[5]

[1] Observable universe,, Assessed on June 24, 2019.

[2] Planck collaboration (2013). “Planck 2013 results. XVI. Cosmological parameters.” Astronomy and Astrophysics. 571: A16

[3], Accessed on June 24, 2019.

[4] Christopher J. Conselice, et al. (2016). “The Evolution of Galaxy Number Density at z < 8 and Its Implications.” The Astrophysical Journal. 830 (2): 83.

[5] Psalm 8:1–4

Image credit for the universe of Big band expansion in 13.7 billion years: NASA/WMAP Science Team

Note: Excerpt from my book PHYSICIST’S PERSPECTIVE ON GOD  



How Big is this Universe?


I have written many articles on science and faith here on Science and Life Blogs

How big is the universe?
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How big is the universe?
The astounding discoveries of the vastness of this universe and the complication of the biology/chemistry/physics inside a human being open our eyes to the mysterious and marvelous works created by the wisest Creator.
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Science and Life
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