As we gaze up into the vastness of outer space,
we are reminded of just how small we are in the grand scheme of the universe. We’ve only explored just a small fraction
of the universe, and even physicists know that there’s more that we don’t understand
about outer space than what we’ve figured out. A new paper that was published in the Journal
of High-Energy Physics in March twenty-twenty, called “Nothing Really Matters” - great
title - is why scientists are freaking out over “bubbles of nothing” that eat spacetime. Marjorie Schillo is one of the authors of
this amazing new study. She is a researcher at Sweden’s Uppsala
University in their Department of Physics and Astronomy where she studies theoretical
physics. Physics is the study of matter, energy and
the interactions between them, but it’s a much more exciting science than that description
makes it sound. Physicists try to answer big questions like
“How did the universe begin?” or “What are the basic building blocks of the universe”,
or even “How will the universe end?” Theoretical physics and math may not sound
very cool, but some of the biggest rock stars of science have come out of this field. Isaac Newton invented calculus and discovered
gravitation; Albert Einstein came up with the Theory of Relativity, among many other
important discoveries, and Stephen Hawking was one of the most recognizable scientists
of all time. Many physicists use experiments to test their
theories, but theoretical physics is different in that they use math to attempt to answer
these big questions in areas where scientists can’t yet perform experiments. Marjorie Schillo and her colleagues have spent
years studying the phenomenon of “spacetime decay”, trying to answer the big questions
about how the universe might end. This newest paper explores one possible answer
- a bubble of nothing that eats spacetime. As she explains it: “A bubble of nothing
describes a possible channel for universe destruction; in that the bubble of nothing
expands and can ‘eat’ all of spacetime, converting it into ‘nothing’.” Umm...OK. Translated from “science” to plain English,
what she and her team of researchers at the University of Uppsala in Sweden are saying
is that a bubble of nothing that eats spacetime is just one of the theoretically possible
ways that our universe could be destroyed. To be honest, that doesn’t sound much better... There’s plenty of things in the universe
worth freaking out about - black holes, supernovas, even rogue asteroids. But could a bubble of nothingness really eat
all of space and time, devouring the universe and ending life as we know it? Is the universe really eating itself from
the inside out? The idea of a “bubble of nothingness”
in space isn’t a new one. In nineteen-eighty-two, theoretical physicist
Edward Witten first posited that the universe could be devouring itself when he wrote about
a hole that “spontaneously forms in space and rapidly expands to infinity, pushing to
infinity anything it may meet.” To understand these bubbles of nothing, we
need to wrap our heads around vacuums. No, not that kind of vacuum…In physics,
a vacuum is an empty space devoid of all matter. In Quantum Field Theory, the theory that connects
quantum physics with spacetime, a vacuum is the lowest possible energy state. More ‘excited’ or higher-energy quantum
states tend to decay very quickly into lower energy states as they give off energy. Since a vacuum doesn’t have a lower energy
state to decay to, vacuums are relatively stable. It’s commonly accepted that outer space
is a vacuum, so the universe should be pretty stable, right? Well, it’s not quite that simple. Outer space certainly isn’t devoid of matter
- it’s full of stars, planets, particles and, umm ... people! It’s the extremely low density of the matter
that’s important - between the planets in our solar system there is an average of five
atoms per cubic centimeter. In interstellar space - between the stars
and molecular clouds - there is only one atom per cubic centimeter, and in intergalactic
space - between galaxies - there’s one-hundred times less matter per cubic centimeter than
in interstellar space. This extremely low density of matter, combined
with the incredibly low pressure in space, creates an almost perfect vacuum ... but not
quite. Quantum theory actually suggests that a perfect
vacuum is impossible, since energy fluctuations, known as ‘virtual particles’ happen even
in empty space. In the nineteen-seventies, some Russian physicists
were the first to suggest that there could be a middle ground between a stable vacuum
and an unstable non-vacuum. These ‘false vacuums’ stay in a metastable,
or semi-stable, state for an incredibly long time before decaying, giving them the illusion
of being a stable vacuum when in fact they are not. The quantum force field that pervades the
universe and gives all matter its mass is called the Higgs Field, and it was first detected
by the Large Hadron Collider at CERN. It would take a whole other video to even
begin to explain the Higgs field, but as far as understanding bubbles of nothing is concerned,
here’s why it matters: Recent research into the Higgs Field suggests that we may actually
be living in a false vacuum after all. If that’s true, our university is not the
safe and stable place we once thought - it’s actually unstable, and this is where the bubbles
of nothing have their opportunity. A bubble of nothing is one of the ways that
a false vacuum could theoretically decay to a more stable energy state. If a bubble of nothing were to form within
the apparently false vacuum that is our universe, it would start out as a small hole in the
fabric of our reality. The tiny space of emptiness would then quickly
begin to expand outward, picking up speed as it expands until it’s growing at the
speed of light. As it grows, the bubble of nothing would eat
all of the matter it encounters, gobbling up everything in its path and converting all
matter into nothingness until the universe is erased completely. So what are these ‘bubbles of nothing’
exactly? As you can imagine, describing ‘nothing’
is not exactly easy. It’s tempting to compare a bubble of nothing
to another phenomenon of ‘nothingness’ that we know exists in our universe - black
holes - but a bubble of nothing couldn’t be more different from a black hole. A black hole is an area of such intense gravity
that it sucks anything, including light, into its center. A bubble of nothing, on the other hand, expands
outward and devours everything in its path, turning anything it encounters into more nothing. If you threw something into a black hole,
it would disappear forever, and we would have no idea what happened to it once it passed
through the black hole, since we’ve never seen the inside of one. But if you could throw an object into a bubble
of nothing, it would bounce right back out - for all intents and purposes, it would have
hit the edge of the universe. A bubble of nothing is not the only kind of
bubble that might exist in space. A spacetime bubble is any area of space that
has different properties inside the bubble than the space outside the bubble. For example, some bubbles could have different
strengths of dark energy inside and out. Bubbles of nothing have no interior at all
- they are totally empty inside. As the bubble grows, it ‘eats’ all the
regular matter it encounters and converts it to ‘nothing’. So how could a bubble of nothing form in the
first place? To understand how bubbles of nothing might
form, we have to dive into string theory a bit. Don’t worry, it won’t be that bad… String theory attempts to tie together the
two most basic laws of physics: the theory of general relativity, or gravity - with quantum
physics, the study of the very smallest particles that make up the universe. String theory also attempts to unify the four
forces in the universe - electromagnetic force, strong nuclear force, weak nuclear force and
gravity - into one model. String theory may indeed turn out to be the
“theory of everything”, but it’s important to know that String Theory relies on a lot
of assumptions about particles and forces that can’t yet be proven. Don’t worry, scientists aren’t just blindly
guessing - these assumptions are all based on solid scientific evidence and complex mathematical
equations - needless to say, you’d need a PhD in physics to truly understand the intricacies
of String Theory. The biggest problem with string theory is
that it requires more than the four observable dimensions to work. We can easily observe the three dimensions
of space and the extra dimension of time, but for string theory to work there must be
at least a few other dimensions that are invisible to us. As cool as the idea of hidden dimensions sounds,
it’s not the parallel universe you might be picturing - you know, the one where you’re
you, but with money and power and good looks and….*coughs* anyway… Physicists theorize that these extra dimensions
could actually be incredibly tiny and curled up below the observable scale, making them
too small for us to see them. Scientists can still account for these extra
dimensions mathematically, but we have yet to actually prove they exist. For some reason, bubbles of nothing can’t
form in four dimensional spacetime - don’t ask us to explain the math behind why, it
would take years! But scientists believe that they can form
in stringy multidimensional spacetime like the spacetime described by string theory. In fact, one model of stringy space time,
the Kaluza-Klein model, states that across infinite space the probability of a bubble
of nothing destroying everything is one-hundred percent. So, should we be concerned about bubbles of
nothing appearing in space and devouring the entire universe? Apparently not. Most scientists believe that since the universe
hasn’t eaten itself in the thirteen billion years since the Big Bang, it’s an unlikely
scenario. One Czech string theorist named Lubos Motl
went so far as to say that we should use the idea of bubbles of nothing to rule out certain
descriptions of our universe, since if it was going to happen it would have happened
by now. That doesn’t totally negate the possibility,
but it’s also reassuring to know that scientists consider this to be something to rectify,
not something to agonize over. We’re not sure exactly how scientists would
suggest that we fix a bubble of nothing, but it’s nice to know that they at least think
we can...right? Perhaps most importantly, physicists think
that studying these bubbles of nothingness can give us important clues about the very
beginnings of our universe. The study authors think that the mathematical
models used to describe a bubble of nothing could also be used to model the birth and
expansion of the universe. Marjorie Schillo, the researcher we met at
the beginning of this video, has said “It would be interesting to work out under what
conditions an observer could ‘ride’ on the bubble of nothing and see a universe that
is similar to the one we live in. Because the bubble expands, such an observer
would see an expanding universe.” Riding on a bubble of nothing may be a bit
far-fetched, but this research is important for helping us understand our universe, according
to the researchers who authored the “Nothing Really Matters” paper. They argue that we can learn important lessons
from these bubbles of nothing that might help us better connect the current best theories
about fundamental building blocks of the universe with theories about space and time, and hopefully,
finally, help us finalize String Theory - the theory of everything. So, what are your thoughts on the bubble of
nothing that eats spacetime? Do you think we should be worried about the
universe eating itself from the inside out? Be sure and let us know in the comments! If you thought this video was interesting,
be sure and check out our other videos, like “Astronomers Discover Mysterious Radio Signal
From Another Galaxy”, or this other one instead. See you next time!
