Category:	Science and Technology
Domain:	Physics
Keywords:	Theoretical physics - Theory of Everything, Grand Unified Theory, string theory, quantum mechanics, general theory of relativity
Outlook:	Experimental physicists may finally converge on a single underlying theory that describes all the fundamental workings of the universe, from subatomic particles ruled by quantum mechanics to the gravitational forces so elegantly explained by Einstein's general theory of relativity.
Summary Analysis:	Our universe is made up of building blocks much smaller than atoms. These particles, such as electrons, leptons, and quarks, are governed by three forces: electromagnetism and strong and weak nuclear forces. What about gravity, though? That's the question that Einstein asked for the last thirty years of his life, and physicists are still unable to answer it. The goal is a Grand Unified Theory, a 'theory of everything' that ties together all of these phenomena in a single equation or expression that explains the nature and behaviour of all matter. Building such a theory, Einstein suggested, would be like 'reading the mind of God'. This theory of everything could illuminate some of the biggest mysteries at the heart of physics, from the origins of space and time to the secrets of black holes to the cause of the universe's accelerating expansion. In the last two decades, many scientists have converged on a branch of physics called string theory as the most likely way to explain it all. The basic idea is that at the heart of every particle is a tiny vibrating string that's a millionth of a billionth of a billionth of a billionth of a centimeter long. Unlike the three-dimensional world that we perceive, the strings vibrate in ten dimensions. Every kind of particle and force corresponds to a particular vibrational pattern of a string. Michio Kaku, a physicist at City University of New York and cofounder of string field theory, explains it this way: 'Much as pulling on a rubber band changes its vibration frequency, altering a string's mode of vibration transforms an electron into a neutrino, a quark, or another particle. As they vibrate, they force space and time to curl around them, giving rise to gravity in exactly the manner that Einsitein described in his theory of relativity.' The problem is that so far, there is no experimental proof that string theory is correct. However, massive efforts are now under way to develop technology and instruments that could aid these scientific detectives in their quest for the one true Grand Unified Theory.

	Implications:	Unification of general relativity and quantum mechanics Better understanding of where the universe came from and where it may be headed Clarification of the nature of the dark matter that accounts for about 23% of the universe's matter and energy Examination of predictions that there are hidden dimensions and parallel universes Potential for applications in the very far future (more than 100 years from now) including interstellar travel and teleportation technology
	Early Indicators:	Calculation by Harvard scientists in 1995 of the 'information' held in a black hole, thought to be a massive tangle of strings Theoretical discovery that the topology of space is not smooth as general relativity predicts but actually can tear and repair itself Massive university and institutional programs to support string theory research
	What to Watch:	NASA and ESA launch the Laser Interferometer Space Antenna before 2010 to detect gravity waves that, if found, may have been caused by the vibration of strings shortly after the Big Bang. The Large Hadron Collider particle accelerator comes online near Geneva, Switzerland, in two years, with the goal for string theorists being to discover unknown massive particles produced by strings vibrating at very high 'pitches'. Laboratory gravity tests conducted by more than a dozen teams indicate gravity leaking from three dimensions into the higher dimensions predicted by string theory. The multiuniversity Cyrogenic Dark Matter Search captures particles of dark matter, predicted by string theory, in deep underground mines shielded from the Earth's atmosphere. Other teams in Japan and Europe also find dark matter in their own dark matter hunts.
	Parallels/Precedents:	Einstein's formulation of his theories of relativity Max Planck's introduction of quantum theory
	Enablers/drivers:	'Big Science' projects such as satellites and particle accelerators for experimental physics Encouragement of interdisciplinary collaboration between science and engineering, and within those fields, such as collaboration within science among astrophysics, mathematics, and particle physics
	Leaders:	Organisations: Particle Physics and Astronomy Research Council (UK) [link] Institute of Physics (UK) [link] Royal Astronomical Society [link] Institutions: California Institute of Technology (work of John Schwarz) Cambridge University (work of Michael Green and Paul Townsend) UC Santa Barbara (work of David Gross and Joseph Polchinski) Princeton University (work of Edward Witten and Juan Maldacena) University of Toronto (work of Amanda Peet) Harvard University (work of Cumrun Vafa) UC Berkeley (work of Raphael Bousso)] University of Liverpool [link] University of Durham [link] Royal Holloway, University of London [link] University of Southampton [link] CERN (home of the LHC) [link]
	Figures:
	Sources:	Kaku, Michio. "Testing String Theory." Discover August 2005 Seife, Charles. "Can the Laws of Physics Be Unified?" Science 1 July 2005 [link] Overbye, Dennis. "String Theory, at 20, Explains It All (Or Not)." The New York Times 7 December 2004 [link] Green, Brian. "NOVA: The Elegant Universe" PBS 2004 [link] 't Hooft G, Susskind L, Witten E, Fukugita M, Randall L, Smolin L, Stachel J, Rovelli C, Ellis G, Weinberg S, Penrose R, A theory of everything? Nature. 2005 Jan 20;433(7023):257-9 [link] Hawking, Stephen W, The Theory of Everything: The Origin and Fate of the Universe, Phoenix Books 2006, ISBN 1597775088 UK research on Theory of Everything [link]

	At A Glance:	When:	11–20 years
		Where:	Global
		How Fast:	Years
		Likelihood:	Medium-Low
		Impact:	Medium-Low
		Controversy:	Medium

Related Outlooks: