Astrophysicist Dr. Charles Liu --- host of The Liuniverse podcast, author of the new book ‘The Cosmos Explained,’ an associate at the American Museum of Natural History, and co-author (along with Neil deGrasse Tyson and Robert Irion) of One Universe: At Home in the Cosmos --- recently joined CJ Dearinger, Smitty Neaves, and me on the All Things – Unexplained podcast. Amongst many startling revelations, Dr. Liu revealed that our universe is not only expanding, but its rate of expansion is increasing!

The Big Bang, the singularity, and expansion

According to Dr. Liu, “When we try to compute time in the cosmos, one of the most intuitive ways to think about time is measuring how much the universe has expanded since time equals zero - the Big Bang, the moment that time began to run. As a result, the expansion of the universe is an increase in space as well as in time.”

In his new book, ‘The Cosmos Explained: A History of the Universe From Its Beginning To Today And Beyond,’ Dr. Liu describes the moment of the Big Bang as a singularity of zero volume and infinite density. It was a place where the laws of nature as we understand them did not work.

So, when will the universe stop its expansion and return to this mysterious singularity? Dr. Liu surprised everyone with his answer. As it turns out, never.

Dr. Liu added, “It’s still expanding today, and it continues to do so, and that’s why we can keep track of cosmic time the way that we do.”

The Big Crunch

"For some reason, space itself, as it expands, it gains speed in its expansion. If it did not, if for every cubic inch of space there were not just a tiny, tiny bit of extra expansion energy built into it, then eventually, yes, all of the matter in the universe, not just the black holes, all the stars, all the dark matter - which is way more massive put together than the stars - would eventually draw us down together. It would slow down our expansion, and it would reverse the expansion, and we would fall into something called the Big Crunch."

This notion of the Big Crunch, that one day the universe will just stop expanding and smash us all back into a new singularity, has been around for a while.

“As late as 20-ish years ago, that was a very real possibility. Our observations just weren’t solid enough to know how much expansion power space had. But since about 1997 - first with the Hubble space telescope of nearby galaxies, then followed by measurements of the cosmic microwave background and its geometry, and then followed by cosmological distances measured by exploding stars called Type Ia supernovae (read: “type one-A”) - we are now quite certain that space itself has so much power in its expansion that its driving all the galaxies so far apart it will overwhelm gravity, and within a few billion years…all of those objects will be driven so far apart that there will no longer be any hope of pulling them back together again.”

Dark energy and the multiverse

Dr. Liu continued, “This drive is called dark energy. It is three times more powerful than the gravity of even dark matter. That’s what’s really driving the motion of the universe today.”

So, the edges of our universe are not only expanding, but their rate of growth continues to mysteriously expand as well. What lies beyond the edges of our universe? What are we expanding into?

Dr. Liu said, “We’re pretty sure that whatever it is expanding into, it’s not more universe. In other words, we are in a four-dimensional space-time. We have three dimensions of space - length, width, and height - plus this dimension of time that we are travelling through. When the universe is expanding, it must be expanding into something that has additional dimension. It could be, for example, this five-dimensional membrane, to which I referred to earlier - the Randall-Sundrum Theory - which sort of tried to explain that our universe is connecting to five-dimensional structures, and thus we wind up being a four-dimensional space-time that sort of bridges the gap between them.

Another idea that has recently come about…people were trying decades ago as to figure out certain aspects of the geometry of the universe. Why was it the way it is? By doing that, people came up with the idea, that at one point very early in the universe, right around that quadrillionth of a quadrillionth of a second moment, the universe for some reason didn’t just expand, but it inflated. So, for a moment, instead of just regular kind of expansion, it went whoosh! And then went back to its normal expansion. That whoosh! thing we call inflation. That kind of inflation, if it happens in a multidimensional universe, it could happen over and over and over. So, we could be, what we see right now, is an inflationary space-time within a larger more-than-four-dimensional universe, or we could be this membrane-bridging four-dimensional space-time, in, again, something that is larger than what we would consider our universe.”

To help everyone visually understand, Dr. Liu described the following scenario:

Just imagine a flag. Two flags, fluttering in the breeze and every once in a while, one of them touches. A spot touches here, or here and we might be that touch point.

Go forth into the infinite

One of the incredible things about astrophysicist Dr. Charles Liu is his ability to make the most complex of topics welcome to everyone. His book, 'The Cosmos Explained,' allows you to go on a palatable journey through the realm of astrophysics and come away with nothing less than a better understanding of how our universe works. That is a powerful accomplishment for an author and his book.

As William Butler Yeats - one of the foremost figures of 20th-century literature - said, “Education is not the filling of a pail, but the lighting of a fire.”

It could be your fire that finally shines a light on the truth of dark energy. Your fire that illuminates beyond this universe and into the universes beyond.


All Things – Unexplained podcast is available wherever you podcast: Apple, Google, Spotify, Amazon, and many more. They’re also on Facebook, Instagram, Twitter, and YouTube. Their show depends on listener support. You can donate on Venmo @bigfootufo.
Liu, C., & Malowichko, M. (2022). The cosmos explained: A history of the universe from its beginning to today and beyond. Ivy Press.
The Liuniverse podcast can be found on YouTube.
Tyson, N. deGrasse., Liu, C., & Irion, R. (2000). One universe: At home in the cosmos. Joseph Henri Press.