The Big Bang: What banged, why it banged, and what happened before it banged


The Big Bang theory was first conceived nearly a century ago. For many people, it seems to explain how the universe came to be. For cosmologists, however, it opens up many more questions. Neil Swidey of the Boston Globe writes, “The Big Bang theory offers an explanation for how the early universe expanded and cooled and how matter congealed, from a primordial soup into stars, planets, and galaxies. What it describes, then, is the aftermath of the Bang. But it is effectively silent on why or how that first massive expansion happened or where all the original matter came from.”

MIT professor Alan Guth has spent the past three decades hypothesizing about “what banged, why it banged, [and] what happened before it banged”. As a postdoctoral student, Guth developed the inflation theory, the “exponential expansion of the universe within its first fraction of a second”, which provided a solution to several major problems with the big bang theory – the monopole problem, the flatness problem and the horizon problem. Swidey explains the theory in everyday-English:

At extremely high energies, there are forms of matter that upend everything we learned about gravity in high school. Rather than being the ultimate force of attraction that Newton and his falling apple taught us, gravity in this case is an incredibly potent force of repulsion. And that repulsive gravity was the fuel that powered the Big Bang.

The universe is roughly 13.8 billion years old, and it began from a patch of material packed with this repulsive gravity. The patch was… one 100-billionth the size of a single proton. But the repulsive gravity was like a magic wand, doubling the patch in size every tenth of a trillionth of a trillionth of a trillionth of a second. And it waved its doubling power over the patch about 100 times in a row, until it got to the size of that marble. All that happened within a hundredth of a billionth of a trillionth of a trillionth of a second. As a point of comparison, the smallest fraction of time that the average human can detect is about one-tenth of a second.

The ingredients of what would become our entire observable universe were packed inside that marble. While the density of ordinary material being put through that kind of exponential expansion would thin out to almost nothing, a quirk of this repulsive-gravity material allowed it to maintain a constant density as it kept growing. But at a certain point — while the universe was still a tiny fraction of a second old — inflation ended. That happened because the repulsive-gravity material was unstable, and, like a radioactive substance, it began to decay. As it decayed, it released energy that produced ordinary particles, which in turn formed the dense, hot “primordial soup.”

The theory turned Guth into a celebrity in the scientific world and landed him a professorship at MIT but at the time it proved impossible to collect observational evidence to support the theory.

Until this past March when astrophysicist John Kovak and his multi-institution team were able to come up with “rock-solid” evidence to back Guth’s theory. In 2006, NASA scientists produced a map of the early universe which suggested that Guth was on the right track, but Kovak’s evidence seemingly solidifies the theory:

Kovak’s team found the smoking gun for inflation: evidence of gravitational radiation, or more specifically, swirling patterns in the polarization of the cosmic microwave background. In the viewfinder of their telescope on the South Pole was light formed just 380,000 years after our universe banged onto the scene. And in that ancient light they detected gravitational radiation that is far older, having been emitted during the universe’s first fraction of a second of existence.

Guth’s theory and Kovak’s supporting observations strengthen the overall theory of the Big Bang and provide a clearer understanding of the birth of the universe. The full article can be read on The Boston Globe.

On a side note, the inflation theory is not Alan Guth’s only achievement; he also won an award for the messiest office in Boston.


John Purrington posted on January 12, 2017 at 12:47 am

I stil don’t understand what existed before the bang. did space exist? Where did that tiny pre-marble thing come from? Where did repulsive gravity come from?

CAS Core Curriculum posted on January 12, 2017 at 8:15 am

Big questions! Can we suggest “A Universe From Nothing: Why There Is Something Rather Than Nothing” (Free Press, 2012) by Lawrence Krauss? Or we can rope in one of our science instructors or Core Peer Tutors to talk science with you right here in the comments section.

Bruce Camber posted on March 13, 2018 at 11:35 am

Since VPriest wrote this article, Neil Turok (Perimeter), Nima Arkani-Hamed (IAS), and Max Tegmark (MIT) have begun to plead for a fundamental re-orientation requiring a deep redefinition of space, time and infinity. They ask, “What are more fundamental concepts?”

I propose that we use more general concepts but with very specific meanings that we know well: continuity, symmetry and harmony. The redefinition goes something like this:
1. Continuity begets order begets numbers which beget time.
2. Symmetry begets relations which beget geometries which beget space.
3. Harmony begets dynamics begets systems begets space-time.

Continuity-symmetry-harmony redefine the infinite. Space and time are redefined as derivative, finite, and quantized. Our chart of the universe based on the power of 2 starts at the Planck units of Length/Time and Mass/Charge: By the 67th doubling there are real measurements within that space perhaps best described as the CERN scale. By the 84th doubling, there are real measurements of time.

By the 143rd notation there we are coming up on a measurement of one second. And, then by the 202nd notation, we have the whole universe in our hands! If we review just a small sampling of those 202 notations, there is a logic, a flow, and concrete numbers to examine: These numbers support the logic of a quiet expansion, plus the numbers support the current definitions of the cosmological epochs better than the estimates and guesstimates from within the infinitely-hot, infinitely-dense start proposed by Guth and Hawking.

Surely, I invite your comments.

-BECamber, BU STH ’75 and BU GRS ’75-’80

zakbos posted on April 21, 2018 at 9:22 pm

Not sure what you mean by “notations”; iterations of some sort of operation?

Jerome posted on November 20, 2018 at 4:12 pm

Bull were did any energy come from and how did the first particle come about?

Jerome posted on November 20, 2018 at 4:16 pm

Bull were did any energy come from and how did the first particle come about? If you say it always existed then you are admitting their is a GOD.

zakbos posted on November 20, 2018 at 4:19 pm

As above — I would suggest “A Universe From Nothing: Why There Is Something Rather Than Nothing” (Free Press, 2012) by Lawrence Krauss. It makes a good effort to answer exactly those sorts of questions!

zakbos posted on November 26, 2018 at 8:19 am

Did you take a look at the books we recommended?

Alan posted on December 11, 2018 at 2:25 am

I simply refuse to believe Lawrence Krauss idea that the universe created itself from nothing?

Or that nothing made everything! Any 8 year old child knows that is utter nonsense!!

If a highly intelligent person says something stupid, it is stupid! “period”

Anyway Krauss’s nothing is not nothing! It is sort of messy primordial soup or concentrated energetic fundamental particles, (it is a something from which he thought up, so that he could create everything out of nothing)

“Unprovable nonsense” And I am being “very polite”

Behind the universe is a “Mind”

The astronomer Sir James Jean quoted that the more he looked at the universe through his telescope, the less like a machine it seems to be and “the more like a great thought”


zakbos posted on December 11, 2018 at 9:08 am

“If a highly intelligent person says something stupid, it is stupid.”

One of the reasons I am glad that good college courses expose students to great and contentious questions, is so that they can gain experience using the principle that we CAN’T merely dismiss ideas that might, at the outset, seem stupid. Many intelligent people disagree about a great many things; but it is a foolish thing to attribute that disagreement to someone’s being “stupid.”

Was there any part of Krauss’ book that you found useful?

ButHow posted on April 13, 2019 at 9:24 pm

And this background gravitational radiation/gravity was caused by what?
Oh that’s right, they don’t know.
Science. No answers ever. Just theories. We think this. We think that. We proved this. Oh that was just disproven. We know this. Just kidding. We thought we knew, but now we know this. Til next time and a billion dollars wasted later. So annoying.

zakbos posted on April 18, 2019 at 9:26 am

Actually, science has a pretty detailed account of the origin and nature of the cosmic microwave background, or CMB: I’d love to know what you think of this article.

E.W. Stevenson posted on July 28, 2019 at 11:31 pm

The term “Space/Time” is like “Apple/Orange”. They are not the same thing and are not related –(Einstein notwithstanding).
Looking forward or backward, space has no beginning nor end. Likewise, time has no beginning nor end. The only thing that is real is infinity itself.
Matter is intangible, since the progressive smallness below electrons and protons suggests that everything is actually only energy, rather than tangible matter. So, “an exploding marble” ?

zakbos posted on July 29, 2019 at 10:17 am

How does the scale of physical reality smaller than particles suggest that “everything is energy”?

Rioen posted on October 2, 2019 at 3:37 pm

yea the universe is just a simulation. if something freaking banged, WHY?! like, the earth is soooo flat. And we live in a simulation. Ever wondered what would hapen if aliens looked through their telescopes on earth? they would see dinosaurs. It’s a simulation. PROVED.

zakbos posted on October 2, 2019 at 3:54 pm

Gotta wonder — if the universe is a simulation, on what kind of a system is it being simulated? What is *running* the simulation? Some interesting headlines were generated regarding this “simulation hypothesis” earlier this year…

Umra posted on December 27, 2019 at 2:18 pm

What about big crunch?
Is it similar?
And if first it was contracting , then from where did the contracting material came?

zakbos posted on January 3, 2020 at 10:57 am

Richard Bentley (a contemporary of Newton) had wondering along the same lines! He formulated a paradox, There are some interesting links there… check it out.

Grorge posted on November 12, 2020 at 7:16 pm

Why is is so hard to accept: “In the beginning GOD created the heavens and the earth?” I suppose arrogance is at the root. Which is harder to believe, a microscopic patch came out of nowhere and led to such sophistication that we see before us today or that and intelligent designer put it all in motion and maintains it?

zakbos posted on November 13, 2020 at 9:32 am

These are just the sorts of questions that come up in our first-year courses on Origins — both in the Humanities section, and the Natural Sciences. Keep asking, and keep exploring!

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