Ever since early astronomers yanked Earth from center stage in the solar system some 500 years ago, scientists have been pulling the rug out from under people's basic beliefs.
"The history of physics," says Harvard physicist Andrew Strominger, "is the history of giving up cherished ideas."
No idea has been harder to give up, however--for physicists and laypeople alike--than everyday notions of space and time, the fundamental "where" and "when" of the universe and everything in it.
Einstein's unsettling insights more than 80 years ago showed that static space and fixed time were flimsy facades, thinly veiling a cosmos where seconds and meters ooze like mud and the rubbery fabric of space-time warps into an unseen fourth dimension. About the same time, the new "quantum mechanical" understanding of the atom revealed that space and time are inherently jittery and uncertain.
Now, some physicists are taking this revolutionary line of thinking one step further: If their theories are right, in the words of Edward Witten of the Institute for Advanced Study in Princeton, space and time may be "doomed."
Concurs physicist Nathan Seiberg, also of the institute: "I am almost certain that space and time are illusions. These are primitive notions that will be replaced by something more sophisticated."
That conclusion may not affect anyone's morning commute. But it is rocking the foundations of physics--as well as causing metaphysical reverberations that inevitably follow major changes in our fundamental understanding of how the universe works.
The impetus behind this tumult is an idea that has become increasingly dominant in modern physics: string theory. According to string theory, the most basic ingredients in the universe are no longer point-like particles, the familiar electrons and quarks. Instead, they are unimaginably small vibrating strings of some unknown fundamental stuff.
String theory suggests that different configurations of strings produce different harmonic chords--just as a piano produces a sound different from that of a flute. The vibrating string gives rise to the particles, and the way the string vibrates determines each particle's properties. This all takes place in a convoluted landscape of 11-dimensional space.
It is a concept so strange that even theoretical physicists struggle to understand it. String theory offers a universe bizarre beyond imagining: Under powerful enough magnification, every known particle in the universe would resemble a complex origami folded out of sheets or strings of the three familiar spatial dimensions, plus one dimension of time, plus seven extra dimensions of space.
While string theory is far from proven, or even well formulated, its consequences would be enormous. Among other things, it would:
* Reshape fundamental notions of space and time, energy and matter, expanding the number of dimensions to 11.
* Give the first comprehensive list of all the ingredients that make up the universe.
* Reveal that every tick of a clock, every barking dog, every dying star, can be described by one master mathematical equation.
Being Involved in a 'Scientific Revolution'
Which practical fruits will flow from the new view of the universe remain unknown. But in the past, fundamental revolutions in physics have--against everyone's wildest expectations--flowered into everything from cell phones to brain scans.
"I've been in physics for 35 years, and this is the first time I've felt I'm involved in a scientific revolution," said Stanford physicist Leonard Susskind. "In the last five or six years, I really have the feeling we're doing something as crazy, as interesting, as new as the revolution that Einstein wrought."
Perhaps most revolutionary of all, it appears that space and time aren't essential ingredients of a universe ruled by strings.
To grasp the extent of the current upheaval in physics, consider what has happened to our basic understanding of space and time over the past hundred years.
Until the early 20th century, scientists, like laypeople, assumed that space and time were fixed--like huge, metaphysical clocks and rulers in the firmament. Objects that moved in this unchanging background could be pinned down to definite positions.
"Everything was where it was when it was supposed to be, and that was all there was to it," said Strominger. "Space-time was out there. You could count on it."
Then, Einstein revealed that space and time were woven into a single fabric that deforms like so much Silly Putty; indeed, it is the warping of the fabric of space-time by massive objects that produces the force of gravity. We perceive gravity as a "force" only because we can't directly perceive the fourth dimension.
Because gravity affects everything, everything gets warped by its pervasive influence--including the clocks and rulers we use to measure time and space.