What Came Before the Big Bang?
Based on Second Thought's video on YouTube. If you like this content, support the original creators by watching, liking and subscribing to their content.
The Big Bang is the leading origin model, supported by evidence of cosmic expansion and observations of early-universe light about 300,000 years after the event.
Briefing
The most honest answer to what came before the Big Bang is still “we don’t know”—because physics can’t currently describe a “before” in a way that can be tested. The Big Bang remains the leading explanation for the universe’s origin, with strong observational support: the universe is expanding, and telescopes can see back to extremely early times, including light emitted roughly 300,000 years after the Big Bang. With the Large Hadron Collider at CERN, scientists also try to recreate tiny, short-lived conditions that resemble the early universe, but only on scales far removed from the true beginning.
That gap matters because humans naturally look for cause-and-effect. If the universe began at a single moment, the question becomes what set that moment in motion. One popular line of speculation treats the “before” as meaningless: perhaps the Big Bang was the start of time itself, with no prior state where “before” could exist. Another idea flips the story into a cycle. In a “big bounce” scenario, a previous universe collapsed into an ultra-dense state—sometimes likened to a singularity or black-hole-like endpoint—then rebounded into a new expansion. Some versions of this picture suggest the bounce could have been repeating for an arbitrarily long time, raising the same problem: what started the first cycle, if any.
Other hypotheses move the question outward rather than backward. Einstein is quoted comparing the attempt to understand “before the Big Bang” to finding “more north than the North Pole,” underscoring how the usual concepts may break down at the boundary of time. Some theorists propose a multiverse: our universe could be one of infinitely many universes existing in higher dimensions. In that framework, collisions between universes might leave detectable fingerprints in the cosmic microwave background—the afterglow of the early universe. Yet no such distinctive signal has been found so far.
A related multiverse idea goes further: universe collisions could trigger a cataclysmic event that effectively creates a new Big Bang, producing an entirely new universe. But this line of reasoning depends on string theory being correct, and string theory—while influential—has not reached full consensus acceptance.
Looking ahead, the search for evidence is tied to better data from early-universe observations. The upcoming James Webb Space Telescope is expected to peer farther back than ever, potentially clarifying how the earliest galaxies formed and shedding light on the conditions around the beginning of space and time. Whether Webb resolves the “before” question or simply sharpens it, the core message remains: current science can describe the early universe remarkably well, but it still can’t say what came before the Big Bang with the same level of certainty. Until that changes, the riddle stays open—alongside competing possibilities like a timeless origin, a cyclic bounce, or a multiverse created through collisions.
Cornell Notes
The Big Bang is the leading explanation for the universe’s origin, supported by evidence of expansion and observations of light from about 300,000 years after the event. But the question “what came before” runs into a fundamental limitation: physics may not define a meaningful “before” if time itself began with the Big Bang. Several speculative frameworks attempt to bypass that barrier, including a timeless origin, a cyclic “big bounce” where earlier universes collapse and rebound, and multiverse ideas where collisions or higher-dimensional dynamics create new Big Bangs. Many of these concepts remain unconfirmed because predicted observational signatures—such as distinctive patterns in the cosmic microwave background—haven’t been detected. Future observations, especially from the James Webb Space Telescope, may tighten constraints on early-universe models and potentially bring the field closer to an answer.
Why does the “what came before the Big Bang?” question feel different from ordinary cause-and-effect questions?
What are the main speculative answers to what came before the Big Bang?
How do multiverse and collision ideas try to become testable?
Why does the transcript link some multiverse ideas to string theory?
What observational progress could change the situation?
Review Questions
- What does it mean for “time” to begin with the Big Bang, and how does that affect the question of a “before”?
- Compare the “big bounce” and multiverse-collision ideas: what prior-universe mechanism does each propose, and what evidence would be expected?
- Why might cosmic microwave background observations be central to testing some multiverse hypotheses?
Key Points
- 1
The Big Bang is the leading origin model, supported by evidence of cosmic expansion and observations of early-universe light about 300,000 years after the event.
- 2
Current physics cannot reliably describe a meaningful “before” if time and the laws of physics began with the Big Bang.
- 3
Speculation includes a timeless origin (“nothing” before), a cyclic “big bounce,” and multiverse scenarios where our universe is one among many.
- 4
Big bounce models face an unresolved question of what started the first cycle, even if cycles continue indefinitely.
- 5
Some multiverse collision ideas predict detectable signatures in the cosmic microwave background, but no such distinctive evidence has been found.
- 6
Several multiverse mechanisms depend on string theory, which remains influential but not fully accepted across the field.
- 7
The James Webb Space Telescope is expected to improve observations of the earliest galaxies and early-universe conditions, potentially tightening constraints on origin theories.