Main content
Big History Project
Course: Big History Project > Unit 2
Lesson 1: The Big Bang | 2.0- WATCH: Unit 2 Overview - The Big Bang
- ACTIVITY: Unit 2 Vocab Tracking
- WATCH: A Big History of Everything
- READ: Complexity and Thresholds
- WATCH: Threshold 1 —The Big Bang
- ACTIVITY: This Threshold Today
- WATCH: Questions About the Big Bang
- ACTIVITY: Threshold Card — Threshold 1 The Big Bang
- Quiz: The Big Bang
© 2023 Khan AcademyTerms of usePrivacy PolicyCookie Notice
WATCH: Questions About the Big Bang
Astrophysics offers profound insights into the Big Bang, the birth of our Universe. Through scientific observations and mathematics, we can explore the Universe's evolution, its continuous expansion, and the lingering light from the Big Bang. Yet, questions remain about the Universe's inception and whether it sprang from nothing or a pre-existing state. Here, Janna Levin discusses what we know about the Big Bang, and ponders the profound questions that remain. Created by Big History Project.
Want to join the conversation?
If the universe is always expanding, what is the cause of that?(4 votes)
We don't know precisely what is causing the expansion of the universe. For now, we label that expansive force 'dark energy'.(7 votes)
How did the Big Bang form from nothing?(4 votes)
The big bang did not happen because there is a God that loves all of us soooooo much and he made everything including all of us. How could the earth form from nothing?(1 vote)
Are there any compelling counter-theories besides the Big Bang theory ?(6 votes)- There was the static state theory, which Einstein developed the cosmological constant to help explain it. However, Edwin Hubble's observations pretty much ended that theory.(2 votes)
Is the big bang really true or is it just a theory?(2 votes)
The big bang theory is the best explanation we have for a picture of the history of our universe which is consistent with our observations. It and the theory of evolution are theories, true, but they are supported by a great deal of evidence, just like the theory of gravity, electromagnetic theory, and many others.
Any statement made by a scientist has some level of uncertainty associated with it. However, as more and more experiments are done and reproduced with consistent results, the doubt surrounding an idea fades away. Being truly objective, we can never claim absolute certainty about anything, but at a certain point, we become convinced. The big bang theory is at this stage for those who have studied physics. There are still many unanswered questions, some of which are mentioned in this video, but that's what keeps things interesting!
Science depends on physical measurements, and it answers questions about the physical world. Because of this, our understanding of the big bang doesn't need to conflict with spiritual ideas. Since we do not have a way of making objective spiritual measurements, science cannot make claims about spiritual questions. These questions are left in the somewhat overlapping realms of philosophy and theology. Science is fun! And it's a shame that sometimes people are steered away from it because of philosophical misconceptions. They're missing out. :)(7 votes)
Why does Big Bang theory exist ?(3 votes)- It is currently the best explanation for how the universe formed based on the evidence we see.(1 vote)
if the universe formed 13.8 billion years ago, and started out really hot but then cooled, what will the universe look like in another 13.8 billion years?(1 vote)
When they say that the Big Bang happened 13.8 billion years ago, is that assertion based on the current rate of expansion of our universe ? What if the current rate of expansion was different in the past ? If it was, how can we tell ?(1 vote)
It is based on multiple measurements of the rate of expansion over time. The expansion rate WAS different in the past, we know that.(1 vote)
I have a question that why did the tiny mass of energy in which the whole universe was stored explode ? I mean that if that mass was infinitely dense and it had enough gravity to overcome the forces of repulsion between the particles then why did it inflate ? We don't see such things happen in black holes but that might be because we can't see them at all !(1 vote)- Maybe it is something like quantum tunneling, and the matter making up that universe now is only a tiny fraction of the amount in the tiny dot before the big bang, because anti-matter and matter annialated to leave befhind that matter that forms the whole universe now.(1 vote)
do we know the properties of the big bang(0 votes)
Video transcript
I think the real reason
I got interested in astrophysics was
to understand the Big Bang. That was the first really profound question
that I realized was answerable, at least in principle,
through mathematics and through
scientific observations and that kind of discovery, that you could sit there
with your pen and paper and then bring it
to an observer and say, "These are the list
of possibilities that we've predicted
for the Universe." And can you discriminate what's
true from what's not true by actually
looking at the cosmos? And today, we live
in a time where cosmology, the study of the early
Universe, is very precise in terms of what we know
about the very early Universe, the first few minutes
after the Universe began and what we know about the evolution
of the Universe since. And we're still surrounded
in this bath of light that's left over from
the Big Bang. It's cooler now
because it's been... the Universe has been expanding
in the 14 billion years since and it's cooled down
but it's there. It's everywhere around us. And we see galaxies are all moving away
from other galaxies, so it's as though the space
between them is stretching. And that's evidence
that the Universe continues to expand
after the initial Big Bang. And yet, there are
really profound questions that we can't answer
that I study, like, "What happened in the
very first moment?" And, "Was there really nothing and then instantaneously
something?" And, "When did that happen
and why did that happen? Why did the Universe suddenly
burst into existence?" Or, "Is that story just wrong?
Are we just confused about that? Is it really the case
that the Universe existed?" It just looked very different and a small patch of space
itself began to expand and grow and evolve and that that's
what we mean by the Big Bang, this moment when a little tiny
piece of a greater megaverse or multiverse began
to expand into our Universe, our observable history. And so, these are deep questions
that we're still wrestling with and we don't yet know
how to ask for evidence as to which one of these
possibilities is true and I just hope that
sometime in my, you know, scientific career
in my lifetime, that we'll figure out
a way to discriminate between these possibilities by actually looking at
the Universe that's out there.