The First Light

Welcome to the very first post on my Torah & Astronomy blog!

In honor of Chanukah, the Festival of Lights, I have written about light – an important topic much loved by both astronomers and Judaism! It also happens to be the very first thing of all, so what better place to begin? (A more general intro to follow in a future post.)


The First Light

The supposed conflict between the narrative of Ma’aseh Bereishit – the Creation – in Genesis and modern science, including cosmology, planet formation and evolution, is a popular topic, with controversies periodically grabbing headlines.

Here, I will share with you some midrash aggadah from the Babylonian Talmud that, when considered alongside modern science, sound strikingly similar. I am not claiming that the ancient rabbis knew modern science long before it was discovered, of course.

But I am saying that if the rabbis of the Talmud were not only willing, but happy, to interpret Biblical verses in a way that goes far afield from the pshat (the straightforward meaning of the words) then we too should feel comfortable with understanding the Bible in consonance with scientific understandings that may seem far from the biblical text. Ancient rabbinic midrashim already have such an understanding in consonance with modern scientific ideas! (I’m not saying that the Talmudic and scientific explanations are exactly the same; you can’t expect perfect and complete explanations of all this material here in a blog post.)

Let’s begin at the very beginning, the first verses of Genesis:

Genesis 1: 1-5

1: In the beginning God created the heaven and the earth.

2: And the earth was without form, and void; and darkness was upon the face of the deep. And the Spirit of God moved upon the face of the waters.

3: And God said, Let there be light: and there was light.

4: And God saw the light, that it was good: and God divided the light from the darkness.

בראשית פרק א

א) בראשית, ברא א-להים, את השמים, ואת הארץ

ב) והארץ, היתה תהו ובהו, וחשך, על-פני תהום; ורוח א-להים, מרחפת על-פני המים

ג) ויאמר א-להים, יהי אור; ויהי-אור

ד) וירא א-להים את-האור, כי-טוב; ויבדל א-להים, בין האור ובין החשך

Most people who read these verses understand the narrative fairly straightforwardly: The first thing God created was light. However, the Talmudic rabbis have a question on these verses, which we find in Tractate Hagiga:

Hagiga 12a

Was light created on the first day? Is it not written [Gen. 1:17]: “And God set them in the expansion of the heaven,” and also [ibid. 1:19]: “And it was evening and it was morning the fourth day”? This is as R. Elazar said: The light which the Holy One created on the first day, one could see by it from one end of the universe to the other. When the Holy One observed the generation of the flood and the generation of the dispersion, and that their actions were corrupt, He took it from them and concealed it from them, as it says “He kept from the wicked their light” [Job 38:15] And for whom did He hide it away? For the righteous in the world to come…

.חגיגה י”ב

ואור ביום ראשון איברי והכתיב ויתן אותם א-להים ברקיע השמים וכתיב ויהי ערב ויהי בקר יום רביעי כדר’ אלעזר דא”ר אלעזר אור שברא הקב”ה ביום ראשון אדם צופה בו מסוף העולם ועד סופו כיון שנסתכל הקב”ה בדור המבול ובדור הפלגה וראה שמעשיהם מקולקלים עמד וגנזו מהן שנאמר (איוב לח) וימנע מרשעים אורם ולמי גנזו לצדיקים לעתיד לבא

The verses referred to describing Day Four are Genesis 1:14-19:

Genesis 1:14-19

14: And God said, Let there be lights in the firmament of the heaven to divide the day from the night; and let them be for signs, and for seasons, and for days, and years:

15: And let them be for lights in the firmament of the heaven to give light upon the earth: and it was so.

16: And God made two great lights; the greater light to rule the day, and the lesser light to rule the night: he made the stars also.

בראשית פרק א

יד) ויאמר א-להים, יהי מארת ברקיע השמים, להבדיל, בין היום ובין הלילה; והיו לאתת ולמועדים, ולימים ושנים.  (טו) והיו למאורת ברקיע השמים, להאיר על-הארץ; ויהי-כן.  (טז) ויעש א-להים, את-שני המארת הגדלים:  את-המאור הגדל, לממשלת היום, ואת-המאור הקטן לממשלת הלילה, ואת הכוכבים.  (יז) ויתן אתם א-להים, ברקיע השמים, להאיר, על-הארץ  

The contradiction is that, based on subsequent verses describing the creation of the heavenly lights (the Sun, Moon and stars) the creation of light must be referring to some light other than those created on the fourth day.

The resolution of this “contradiction” is that the light created by God on day one of creation is not the light of the heavenly bodies that we see today. Rabbi Eliezer, the Talmud explains, says that the light that was the very first thing created on day one was a super-powerful light by which one could see from one end of the universe to the other.

God, upon seeing that this light was good, and that future generations of humanity would become terribly evil, decided to hide the light from humans, and to save it as a reward for the righteous in the future.

Here Comes Science

Cosmology, the branch of Astronomy that deals with the origin of the universe, has, over the past century, arrived at a generally accepted theory often called “Big Bang Cosmology”.

The Big Bang refers to the beginning of the entire universe, over 13 billion years ago. This well established and scientifically proven theory explains that the entire universe began to expand from a single point, and has been expanding ever since.

Edwin Hubble

This expansion was first measured by Edwin Hubble (in the 1920’s), who observed that almost all galaxies are receding from us, and from each other. It has since been measured many times, and with much greater accuracy. By measuring the distance to galaxies and the speed at which they are receding, we can calculate the age of the universe since everything  began to move apart, which has been measured to be ~13.2 billion years.[1]

Hubbles law plot
Hubble’s measurements of galaxies used to calculate age of universe

Another crucial observation that verified the Big Bang theory was the observation (in the mid-1960’s) by Penzias and Wilson of what is called the “3 degree (Kelvin) microwave background radiation”.


Penzias & Wilson
Penzias & Wilson
CMB uniformity
Sky Map of Cosmic Background Radiation (in false color) from COBE satellite, c. 1990s; note the near uniformity

This is light in the low energy radio wave part of the spectrum (similar to kitchen microwaves) that fills the sky in all directions almost uniformly. Its existence was predicted by the Big Bang theory, as it is the (much cooled) “leftover” uniform radiation from a short time after the Big Bang.[2]

The bigger the universe gets, the more its (average) density and temperature go down[3]. Extrapolating back, scientists can calculate the temperature and density of the early Universe. From these conditions, an understanding of the behavior of matter and energy can be derived going back to a fraction of a second after the Universe’s began.

Graph of universe's temperature over time (from The Cosmic Perspective, Pearson)
Graph of universe’s temperature over time

Here is a description of the early conditions of the Universe, from Astronomy: The Solar System and Beyond  (by Michael A. Seeds, 3rd ed, pp.423-4; footnotes are my explanations):

Modern cosmologists have been able to reconstruct the history of the early universe… the big bang did not occur in a specific place. The big bang filled the entire volume of the universe from the first moment.

… If we could visit the universe when it was only 10 millionths of a second old, we would find it filled with high-energy photons having a temperature well over 1 trillion (1012) degrees Kelvin and a density greater than 5 x 1013 g/cm3. The photons in the early universe were gamma rays of very short wavelength and therefore had very high energy.[4]

The Eletromagnetic Spectrum i.e Light, including much more than the visible spectrum (from The Cosmic Perspective, Pearson)
The Eletromagnetic Spectrum


In the early universe, the photons had enough energy to produce proton-antiproton pairs… Thus the early universe was a dynamic soup of energy flickering from photons into particles and back again.[5]

While all this went on, the universe was expanding and the wavelengths of the photons were lengthening by the expansion. This lowered the energy of the gamma rays and the universe cooled. By the time the universe was 0.0001 seconds old, its temperature had fallen to 1012 K. … so the gamma rays could no longer produce such heavy particles.

Particle pair creation & annihilation: photons and electron-positron pairs take each others' place (from The Cosmic Perspective, Pearson)
Diagram of particle pair creation & annihilation

… they could produce electron-positron pairs, which are about 1800 times less massive than protons and neutrons. This continued until the universe was about 4 seconds old… The protons, neutrons and electrons of which our universe is made were produced during the first 4 seconds of its history.



At first, the universe was dominated by radiation. The gamma rays interacted continuously with the matter, and they cooled together as the universe expanded. The gas was ionized because it was too hot for the nuclei to capture electrons to form neutral atoms, and the free electrons made the gas very opaque. A photon could not travel very far before it collided with an electron and was deflected. Thus radiation and matter were locked together.

Transition from era of opacity to light traveling freely (from The Cosmic Perspective, Pearson)
Transition from era of opacity to light traveling freely
Timeline of early universe (from The Cosmic Perspective, Pearson)
Timeline of early universe

When the universe reached an age of about 300,000 years, it was cool enough for nuclei and electrons to form neutral atoms. The free electrons were captured by atomic nuclei, the gas became transparent and the radiation was free to travel through the universe. The temperature at this time of recombination was about 3000 K. We see these photons arriving now as primordial background radiation.

Cosmological Confluence

Now that we have explained the conditions in the beginning of the Universe according to cosmology, let’s compare with the midrash we have just studied.

R. Elazar said: The light which the Holy One created on the first day, one could see by it from one end of the universe to the other. Regarding cosmology we read that “The big bang filled the entire volume of the universe” and that “If we could visit the universe when it was only 10 millionths of a second old, we would find it filled with high-energy photons”. The similarity is remarkable! Both R. Eliezer and cosmology say that light filled the entire universe at the very beginning of creation.

Furthermore, in both, this initial light is a “super-light”: In cosmology, it is the most energetic light ever, high energy gamma rays. In midrash, the initial  light was sogood” – “better” or more powerful than the light we see today – somewhat akin to the way gamma radiation is a far more energetic light than we typically see today.

Both describe how the initial super-light is no longer visible today. The midrash says it is hidden away for the righteous to enjoy in the future. There are multiple possible correspondences in cosmology. Shortly after the Big Bang, there was an era of opacity, during which light could not propagate due to free electrons. It was “hidden” everywhere, but it could not “shine forth”. One could also draw an analogy to the “cooling” of the initial “super-light” to much lower wavelengths, either the 3 K background radiation detectable today, or the 3000 K light that finally was able to shine freely after the initial 300,000 years during which light was trapped. Incidentally, that would be light that could be visible to the human eye, were any humans in existence at that time to see it.

We have seen the light! Rather than contradicting modern cosmology, the creation of light in Genesis – studied with midrash from the Talmud– is actually quite close to it!

May we merit to continue to be enlightened by study of Torah – particularly Torah she’ba’al peh – and science (i.e. read my future posts!), especially now, on Chanukah, the Festival of Light.
Chanukah sameach!


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