Do we live in a multiple universe?
Do we live in a multiple universe?
For as long as humans have gazed skyward, a question has loomed in the back of our collective mind: How do we know everything that we see is everything there is?
Technology's horizon
Speed-of-iight horizon
TO THE EDGE AND BEYOND. With current instruments, we can see galaxies out to "technology's horizon." We can't observe galaxies past the "speed-of-light horizon," but they may become visible in the future if the universe's expansion decelerates. ASTRONOMY: ROEN KELLY
Multiverse
Decades of astrophysical research beginning in the late-19th century established the universe as we see it, culminating with the Big Bang theory. We now know the universe is about 13.7 billion years old and at least 150 billion trillion miles across. But in recent years, astronomers have begun to address a staggering possibility — the universe we can observe, and in which we live, may be one of many that makes up the cosmos.
The suggestive evidence for this comes from several directions, from the idea of cosmic inflation, from string theory, and the
Other universes
existence of the famous cosmological constant. Some of the notions that come out of these lines of evidence are pretty counterintuitive. Yet that doesn't worry astronomers.
"I fully expect the true nature of reality to be weird and counterintuitive,"says cosmolo- gist MaxTegmark of the Massachusetts Institute of Technology, "which is why I believe these crazy things."
The idea of multiple universes, or multi- verses, poses the notion of the universe existing like a giant sponge. Each bubble is a distinct universe, like ours, but others could exist separated by giant voids.
What's the evidence for all this? First, measurements of distant supernovae suggest the expansion of the cosmos is accelerating. Second, more and more evidence supports the inflationary scenario of the
◄ BIG PICTURE. Light's finite speed determines how far we can see, but as the visible universe (blue sphere) grows, it is an ever smaller part of a larger universe expanding even faster.
ASTRONOMY: ROEN KELLY
Our universe
Part visible to us
early history of the universe. (See "Does inflation theory govern the universe?" p. 62.) Third, ideas about inflation suggest many Big Bangs may have occurred. Fourth, recent notions about string theory suggest universes of very different types may have formed. (See "Does string theory control the universe?"p. 52.) Altogether, these notions suggest it was possible, if not probable, that
Universe in the balance
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▲ EXPANSION RATES. Our cosmic fate hangs on the universe getting the parameters right, or nearly so. How the universe expands,and at what rate, determines its ultimate fate.
V FORTUNATE UNIVERSE. Physical constants took on values given by chance processes when the universe was born. But if they were any different, we couldn't exist.
For as long as humans have gazed skyward, a question has loomed in the back of our collective mind: How do we know everything that we see is everything there is?
Technology's horizon
Speed-of-iight horizon
TO THE EDGE AND BEYOND. With current instruments, we can see galaxies out to "technology's horizon." We can't observe galaxies past the "speed-of-light horizon," but they may become visible in the future if the universe's expansion decelerates. ASTRONOMY: ROEN KELLY
Multiverse
Decades of astrophysical research beginning in the late-19th century established the universe as we see it, culminating with the Big Bang theory. We now know the universe is about 13.7 billion years old and at least 150 billion trillion miles across. But in recent years, astronomers have begun to address a staggering possibility — the universe we can observe, and in which we live, may be one of many that makes up the cosmos.
The suggestive evidence for this comes from several directions, from the idea of cosmic inflation, from string theory, and the
Other universes
existence of the famous cosmological constant. Some of the notions that come out of these lines of evidence are pretty counterintuitive. Yet that doesn't worry astronomers.
"I fully expect the true nature of reality to be weird and counterintuitive,"says cosmolo- gist MaxTegmark of the Massachusetts Institute of Technology, "which is why I believe these crazy things."
The idea of multiple universes, or multi- verses, poses the notion of the universe existing like a giant sponge. Each bubble is a distinct universe, like ours, but others could exist separated by giant voids.
What's the evidence for all this? First, measurements of distant supernovae suggest the expansion of the cosmos is accelerating. Second, more and more evidence supports the inflationary scenario of the
◄ BIG PICTURE. Light's finite speed determines how far we can see, but as the visible universe (blue sphere) grows, it is an ever smaller part of a larger universe expanding even faster.
ASTRONOMY: ROEN KELLY
Our universe
Part visible to us
early history of the universe. (See "Does inflation theory govern the universe?" p. 62.) Third, ideas about inflation suggest many Big Bangs may have occurred. Fourth, recent notions about string theory suggest universes of very different types may have formed. (See "Does string theory control the universe?"p. 52.) Altogether, these notions suggest it was possible, if not probable, that
Universe in the balance
r
p/i*i *
0$'
ZxPan*
▲ EXPANSION RATES. Our cosmic fate hangs on the universe getting the parameters right, or nearly so. How the universe expands,and at what rate, determines its ultimate fate.
V FORTUNATE UNIVERSE. Physical constants took on values given by chance processes when the universe was born. But if they were any different, we couldn't exist.
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