The Universe: Still Boggling The Minds of 'Finite Creatures' By Robert Roy BrittSenior Science Writerposted: 07:00 am ET12 June 2001
There may be nothing more mind-boggling than the universe. Imagine -- we're halfway through 2001, in the heart of the Information Age, nearly 400 years after the telescope was invented and we don't yet know how big the big house is nor what, if anything, lies beyond.

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"As much as we have progressed in science, we are still finite creatures with limited conceptual abilities and imperfect observational tools," said James Sweitzer, director of astrophysics education at the American Museum of Natural History's Rose Center for Earth and Space.
Humbling thought. But add one thing: We are highly curious creatures prone to speculation.
That in mind, we wanted to at least pose the questions that we suspect swirl through the minds of all who have ever been curious, who have ever looked up on a dark night and simply wondered.
How old is the universe? Does it have an edge? And, c'mon, truthfully -- How could it all have begun in some "Big Bang" that originated in a spot smaller than the dots under all these questions marks?
For answers, we pestered Sweitzer and Mario Livio, head of the science division at the Space Telescope Science Institute in Baltimore.
What a cosmic can of worms. Turns out even the word "universe" is elusive, having three meanings (two of which depend on whether or not you hit the shift key). So we start with the basics.
What does the word "universe" mean?
The "observable universe," Sweitzer explained, "is the one astrophysicists generally talk about because it's the one open to empirical measurements. In fact it's the only one we can or ever will be able to talk with any certainty about."
He goes on to explain that "universe" (sans the word "observable") is a larger concept that scientists think "conforms to our laws of physics and all the assumptions that go with them." Comprehending this universe, Sweitzer said, "requires a leap of faith into unobservable realms."
Finally, there is "the Universe," which, by virtue of its capital "U," includes "absolutely everything, even possibilities of dimensions, modes and regions that obey laws of physics we don't know or maybe even can't know."
Okay then. If we can't know it, let's move on to the next question.
How did the universe begin?
There is a very simple answer to this question: We don't know. And we may never know.
The leading theory for the formation of our universe is the Big Bang, of course. According to this theory, all the matter and energy in our present observable universe was compressed into a very small area, before, in a nanosecond, it exploded outward and expanded continually until the present time -- and will perhaps do so forever.
Unimaginable as it might seem, the Big Bang theory is tame compared to some recently emerging wilder ideas, speculations that pop up like parallel universes in a vacuum of understanding.
Some cosmologists say our observable universe is one of many that spring forth continually from a series of bubbles. In this scenario, one Big Bang begets another.
Another recently proposed scenario holds that instead of springing forth in a violent instant from a teensy point in space, our universe was created when two parallel membranes collided. These "branes," as theorists call them, would have floated like sheets of paper through a fifth dimension until slamming together and generating energy and heat that led to the same expansion described by traditional Big Bang theory.
This Ekpyrotic Universe theory, as it is called, does not replace Big Bang theory. Instead, it offers an alternative way that the currently observed expansion might have been jump-started.
In any case, the Big Bang theory does not actually explain how the universe began. It assumes that space, time and energy already existed. Accept that rather significant caveat and one can then discuss the leading theory for how our present observable universe came into being.
"It started from an extraordinarily dense and hot state, and it has been expanding ever since," said Livio, of the Space Telescope Science Institute, giving perhaps the world's most concise definition of the Big Bang model. But there's more to point out here, including the fact that "dense" is rather an understatement.
Everything that exists now, at least in the observable universe, was once all packed into a sphere one millionth of a meter across, Sweitzer said. Translation -- too small to see.
"That may seem pretty small, but it's only because of our human perspective," Sweitzer assured us, adding that today's universe is "extraordinarily empty." Imagine, as an example, that the area of our solar system -- with nine planets packed into a region less than 9 billion miles (14.5 billion kilometers) across -- is relatively crowded compared to the vast empty stretches between stars, where nothing but a few molecules hang out.
"So there's lots of room to compact what we already see," Sweitzer said. But there was a trade-off for all this miniaturization, like a car that's cheap to run but cramped to sit in. In the case of the universe, it was heat.
"Mighty hot," as Sweitzer put it. As in 10 degrees with 32 zeros after it.
Over time, the universe expanded, cooling as it did so. This expansion was discovered in the 1920s, when Edwin Hubble found that every galaxy he looked at, in any direction, was racing away from us. In fact, the Big Bang was initially suggested to explain this expansion.
Early on, things were smooth. Real smooth.
But the expansion had a ripple effect of major importance, triggering lumps and bumps in the otherwise uniform fabric of space, which led to the birth of the first galaxies.
The Big Bang theory long ago predicted that an aftereffect of these ripples should exist today, throughout the universe, in a faint glow of radiation called cosmic microwave background radiation. This was confirmed in 1964.