- published: 22 Oct 2015
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In physics, a virtual particle is a particle that exists for a limited time and space. The energy and momentum of a virtual particle are uncertain according to the uncertainty principle. The degree of uncertainty of each is inversely proportional to time duration (for energy) or to position span (for momentum).
Virtual particles exhibit some of the phenomena that real particles do, such as obedience to the conservation laws. If a single particle is detected, then the consequences of its existence are prolonged to such a degree that it cannot be virtual. Virtual particles are viewed as the quanta that describe fields of the basic force interactions, which cannot be described in terms of real particles. Examples of these are static force fields, such as a simple electric or magnetic field, or the components of any field that do not carry information from place to place at the speed of light (information radiated by means of a field must be composed of real particles). Virtual photons are also a major component of antenna near field phenomena and induction fields, which have shorter-range effects, and do not radiate through space with the same range-properties as do electromagnetic wave photons. For example, the energy carried from one winding of a transformer to another, or to and from a patient in an MRI scanner, in quantum terms is carried by virtual photons, not real photons.
William Lane Craig (born August 23, 1949) is an American analytic philosopher, philosophical theologian, and Christian apologist. He is known for his work in the philosophy of religion, philosophy of time, and the defense of Christian theism. One of his most notable contributions to the philosophy of religion is his defense of the Kalām cosmological argument, which is the most widely discussed argument for the existence of God in contemporary Western philosophy. In theology, he has also defended Molinism and the belief that God is, since Creation, subject to time.
Craig has authored or edited over 30 books, including The Kalām Cosmological Argument (1979), The Cosmological Argument from Plato to Leibniz (1980), Theism, Atheism, and Big Bang Cosmology (with Quentin Smith, 1993), Philosophical Foundations for a Christian Worldview (with J.P. Moreland, 2003) and Reasonable Faith: Christian Truth and Apologetics (3d edition, 2008).
Craig received a Bachelor of Arts degree in communications from Wheaton College, Illinois, in 1971 and two summa cum laude master's degrees from Trinity Evangelical Divinity School in Deerfield, Illinois, in 1975, in philosophy of religion and ecclesiastical history. He earned a Ph.D. in philosophy under John Hick at the University of Birmingham, England in 1977 and a Th.D. under Wolfhart Pannenberg at the University of Munich in 1984.