Posts Tagged ‘space-time’

The detailed, all-sky picture of the infant universe created from nine years of WMAP data. The image reveals 13.77 billion year old temperature fluctuations (shown as color differences) that correspond to the seeds that grew to become the galaxies. The signal from our galaxy was subtracted using the multi-frequency data. This image shows a temperature range of ± 200 microKelvin.CREDIT: NASA/WMAP SCIENCE TEAM

by Jesse Shanahan

In a study published earlier this month, a team of theoretical physicists is claiming to have discovered the remnants of previous universes hidden within the leftover radiation from the Big Bang. Our universe is a vast collection of observable matter, like gas, dust, stars, etc., in addition to the ever-elusive dark matter and dark energy. In some sense, this universe is all we know, and even then, we can only directly study about 5% of it, leaving 95% a mystery that scientists are actively working to solve. However, this group of physicists is arguing that our universe isn’t alone; it’s just one in a long line of universes that are born, grow, and die. Among these scientists is mathematical physicist Roger Penrose, who worked closely with Stephen Hawking and currently is the Emeritus Rouse Ball Professor of Mathematics at Oxford University. Penrose and his collaborators follow a cosmological theory called conformal cyclic cosmology (CCC) in which universes, much like human beings, come into existence, expand, and then perish.

As a universe ages, it expands, and the constituent parts grow farther and farther apart from each other. Consequently, the interactions between galaxies that drive star formation and evolution become rarer. Eventually, the stars die out, and the remaining gas and dust is captured by black holes. In one of his most famous theories, Stephen Hawking proposed that this isn’t the end; black holes might have a way to slowly lose mass and energy by radiating certain particles. So, after many eons, the remaining black holes in the universe would disappear, leaving only disparate particles. Seemingly a wasteland, this end-state eventually mirrors the environment of our universe’s birth, and so, the cycle starts anew.

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Artist’s logarithmic scale conception of the observable universe with the Solar System at the center, inner and outer planets, Kuiper belt, Oort cloud, Alpha Centauri, Perseus Arm, Milky Way galaxy, Andromeda galaxy, nearby galaxies, Cosmic Web, Cosmic microwave radiation and Big Bang’s invisible plasma on the edge.CREDIT: WIKIPEDIA/PABLO CARLOS BUDASSI

When our universe was very young, before any recognizable components like stars, planets, or galaxies formed, it was filled with a dense, hot soup of plasma. As the universe expanded, it cooled, and eventually, particles could combine to form atoms. Eventually, the interaction and fusion of these atoms resulted in all of the matter that we observe today. However, we can still observe the leftover radiation from that initial, dense period in our universe’s history. This leftover glow, called the Cosmic Microwave Background (CMB), is the oldest electromagnetic radiation, and it fills the entirety of our universe. If the CCC theory were true, then there would be hints of previous universes in our universe’s CMB.

At the end of a universe, when those final black holes dissolve, CCC theory states they should leave behind a signature that would survive the death of that universe and persist into the next. Although not definitive proof of previous universes, detecting that signature would be strong evidence in support of CCC theory. In searching for these “Hawking points”, cosmologists face a difficult obstacle as the CMB is faint and varies randomly. However, Penrose is claiming that a comparison between a model CMB with Hawking points and actual data from our CMB has proven that Hawking points actually exist. If true, this would be the first-ever detection of evidence from another universe.

Unfortunately, as groundbreaking as this discovery seems, the scientific community has largely dismissed it. One of the fundamental characteristics of the CMB is that, although it has patterns, the variations are entirely statistically random. In fact, Penrose’s former collaborator, Stephen Hawking, spotted his own initials in the CMB while others have found a deer, a parrot, and numerous other recognizable shapes in the noise. Similarly, the Wilkinson Anisotropy Microscope Probe that mapped the CMB released an interactive image where you can search for familiar shapes and patterns. An avoidable result of both these random fluctuations and the sheer size of the CMB is that if scientists look hard enough, they can find whatever pattern they need, like the existence of Hawking points, perhaps. Another criticism of Penrose’s claim is that if CCC theory holds true, our universe should have tens of thousands of Hawking points in the CMB. Regrettably, Penrose could find only about 20.

Still, the possibility of alternate universes, whether long-dead or existing in parallel to our own, is tantalizing. Many other theories also claim to find traces of other universes hiding in the patterns of the CMB as well. Although it sounds like science fiction, we are left to wonder: is this just the cosmological equivalent of seeing shapes in random clouds or will scientists one day discover that we are one among many infinite universes?

Jesse Shanahan is an astrophysicist, EMT, and science communicator. For more space and language news, follow her on Twitter here.


By Clara Moskowitz

The universe we live in may not be the only one out there. In fact, our universe could be just one of an infinite number of universes making up a “multiverse.”

Though the concept may stretch credulity, there’s good physics behind it. And there’s not just one way to get to a multiverse — numerous physics theories independently point to such a conclusion. In fact, some experts think the existence of hidden universes is more likely than not.

Here are the five most plausible scientific theories suggesting we live in a multiverse:

1. Infinite Universes

Scientists can’t be sure what the shape of space-time is, but most likely, it’s flat (as opposed to spherical or even donut-shape) and stretches out infinitely. But if space-time goes on forever, then it must start repeating at some point, because there are a finite number of ways particles can be arranged in space and time.

So if you look far enough, you would encounter another version of you — in fact, infinite versions of you. Some of these twins will be doing exactly what you’re doing right now, while others will have worn a different sweater this morning, and still others will have made vastly different career and life choices.

Because the observable universe extends only as far as light has had a chance to get in the 13.7 billion years since the Big Bang (that would be 13.7 billion light-years), the space-time beyond that distance can be considered to be its own separate universe. In this way, a multitude of universes exists next to each other in a giant patchwork quilt of universes.

Space-time may stretch out to infinity. If so, then everything in our universe is bound to repeat at some point, creating a patchwork quilt of infinite universes.

2. Bubble Universes

In addition to the multiple universes created by infinitely extending space-time, other universes could arise from a theory called “eternal inflation.” Inflation is the notion that the universe expanded rapidly after the Big Bang, in effect inflating like a balloon. Eternal inflation, first proposed by Tufts University cosmologist Alexander Vilenkin, suggests that some pockets of space stop inflating, while other regions continue to inflate, thus giving rise to many isolated “bubble universes.”

Thus, our own universe, where inflation has ended, allowing stars and galaxies to form, is but a small bubble in a vast sea of space, some of which is still inflating, that contains many other bubbles like ours. And in some of these bubble universes, the laws of physics and fundamental constants might be different than in ours, making some universes strange places indeed.

3. Parallel Universes

Another idea that arises from string theory is the notion of “braneworlds” — parallel universes that hover just out of reach of our own, proposed by Princeton University’s Paul Steinhardt and Neil Turok of the Perimeter Institute for Theoretical Physics in Ontario, Canada. The idea comes from the possibility of many more dimensions to our world than the three of space and one of time that we know. In addition to our own three-dimensional “brane” of space, other three-dimensional branes may float in a higher-dimensional space.

Our universe may live on one membrane, or “brane” that is parallel to many others containing their own universes, all floating in a higher-dimensional space.

Columbia University physicist Brian Greene describes the idea as the notion that “our universe is one of potentially numerous ‘slabs’ floating in a higher-dimensional space, much like a slice of bread within a grander cosmic loaf,” in his book “The Hidden Reality” (Vintage Books, 2011).

A further wrinkle on this theory suggests these brane universes aren’t always parallel and out of reach. Sometimes, they might slam into each other, causing repeated Big Bangs that reset the universes over and over again.

4. Daughter Universes

The theory of quantum mechanics, which reigns over the tiny world of subatomic particles, suggests another way multiple universes might arise. Quantum mechanics describes the world in terms of probabilities, rather than definite outcomes. And the mathematics of this theory might suggest that all possible outcomes of a situation do occur — in their own separate universes. For example, if you reach a crossroads where you can go right or left, the present universe gives rise to two daughter universes: one in which you go right, and one in which you go left.

“And in each universe, there’s a copy of you witnessing one or the other outcome, thinking — incorrectly — that your reality is the only reality,” Greene wrote in “The Hidden Reality.”

5. Mathematical Universes

Scientists have debated whether mathematics is simply a useful tool for describing the universe, or whether math itself is the fundamental reality, and our observations of the universe are just imperfect perceptions of its true mathematical nature. If the latter is the case, then perhaps the particular mathematical structure that makes up our universe isn’t the only option, and in fact all possible mathematical structures exist as their own separate universes.

“A mathematical structure is something that you can describe in a way that’s completely independent of human baggage,” said Max Tegmark of MIT, who proposed this brain-twistin gidea. “I really believe that there is this universe out there that can exist independently of me that would continue to exist even if there were no humans.”

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