Gravity, Magnetism, and Other Dimensions...
An apple drops to the ground in an autumn breeze. Its mature stem gives way to the force of gravity. A compass
needle guides an ocean-going ship by aligning with the Earth’s magnetic field. Two forces of nature, so common
and permanent, they give a feeling of simplicity. Their explanation, however, eludes the most enduring and
exhaustive efforts of physicists to date.
Sir Isaac Newton is famous for his scientific study of gravity. Through astronomic and terrestrial observations he
learned its patterns of behavior, formulated a set of equations to explain and predict that behavior, and published
them in his Principia Mathematica in 1687. What he couldn’t explain though, was through what mechanism this force
Albert Einstein took up the challenge to explore how the force of gravity “transmits” or exerts itself on objects
of mass. There was no physical way to reveal it, such as through scientific instruments, and he was mostly limited
to thought experiments. He imagined that if space itself was warped by the mass of an object then other objects
within that warped space would move or behave as though there were a mechanical force acting on them. It was a
somewhat radical concept that was considered with a lot of skepticism from his scientific peers. In 1919, however,
an opportunity opened to test this theory in the real world.
In his general theory of relativity he predicted that light would bend when it passed through warped space, called
gravitational lensing, and that you could detect warped space by observing the bending of these light rays. The
experiment is not practically possible on Earth, but a total solar eclipse in 1919 provided the right conditions
to observe star light being bent by the gravity of the Sun. Sir Arthur Eddington, a British astrophysicist,
performed the observations and determined that the apparent gravitational lensing of the Sun displayed stars
(on photographic film) that were actually behind the Sun. They could not have been seen if their light rays had
not been curved.
This empirical evidence was enough to substantiate Einstein’s theory for much of the scientific community, and was
considered a plausible explanation for the force of gravity. Now what about the magnetic force? It too is
instantaneous without any detectable medium of transmission. Does it also require the existence of warped space or
dimensions in order to act?
Human awareness of magnetism – at some level – has existed for centuries. There is evidence in Chinese literature
that a magnetic south-pointing device, called a “sinan”, existed as early as 206 BC, though there is also dispute
of this. The invention of the navigation compass, however, has certainly been with us for a very long time
Michael Faraday’s obsessive observations of magnetism expanded science beyond just its passive use and into an
interactive study of it. He discovered, in 1831, that moving a magnetic field across a wire induced a current flow
through the wire. He also realized that the inverse was true: that current flow through a wire induced a
surrounding magnetic field. This is the basis for the science of electromagnetism, and the foundation for which
most electrical power is generated and used.
The relationship between electricity and magnetism is well understood. It’s been defined by James Clerk Maxwell's
famous set of equations, and studied and utilized by virtually all electrical engineers. Like gravity though, the
mechanism by which the force is actually transmitted is still unknown. Opposite magnetic poles will attract each
other instantaneously in the vacuum of space with nothing detectable to conduct the pull.
If Einstein’s general theory of relativity accurately explains the force of gravity, as it appears it does, then
how do you explain the force of magnetism? Einstein’s theory utilizes the dimensions of space that are known and
the distortions of that space give us the illusion of gravity’s “pull”. The magnetic force may also be the result
of distorted dimensions of space, but dimensions beyond the three that we already know about. It starts to sound a
little crazy but we must open our minds since conventional science cannot explain it otherwise.
The concept of “extra dimensions” actually began to arise in the early 1900s. Gunnar Nordström, a Finnish
theoretical physicist, imagined an additional dimension of space to explain the coexistence of gravity and
electromagnetism in 1914. In 1921 a German mathematician and physicist named Theodor Kaluza formulated a theory,
the Kaluza-Klein theory, which expanded on this idea and incorporated both Einstein’s ‘field equations’ of
general relativity and Maxwell’s equations of electromagnetism. There was a revived interest in the 1980s, and a
desire to combine the concept of ‘other dimensions’ with quantum particle physics has led to terms like string
theory, supersymetry, and unified field theory to be hot topics of modern science.
These ideas and theories to try to understand the mysterious wonders in our world, therefore, are not so new.
They are part of an ongoing process, slowed and frustrated by the limitations of our instruments, and maybe even
our capacity to imagine. Human thought tends towards “rational” thinking and some of these ideas are
counterintuitive in that respect. Common forces of nature should have a common explanation but apparently they
may not. Other dimensions, or string theory in which vibrating strings occupy those other dimensions and
constitute the fabric of space and matter, may become common knowledge to future generations. In the meantime we
should enjoy the mystery and opportunity for that discovery. □
Panel discussion - 2010 World Science Festival
"The Elegant Universe" - NOVA
Einstein’s general theory of relativity