On the Science and theology blog, Matt Donnelly describes better than I could ever, the difference between Intelligent Design and String theory. While some ID activists have claimed that ID is as ‘scientific’ as String theory (or multiverses or …), they miss a few points. Matt Donnelly’s posting is based on an Editorial in the Philadelphia Inquirer titled “A scientific leap, but without the faith”written by Amanda Gefter.
In my own words:
ID is an ad hoc argument to explain something we do not understand. String theory or multiverses follow logically or mathematically from observations.
ID is in principle unfalsifiable, string theory and mutliverses are just hard to falsify
String theory and multiverses fall into a category which is best described as
But the real danger is not string theory’s lack of experiments — it is the misrepresentation of what scientific theories are all about. Sure, falsifiability is a key component of the scientific method. But there is something that matters more: the power of explanation. History reveals that the structure of a theory itself — its internal mathematical consistency, its scope, and its beauty — often determines whether it is accepted as science.
That ID is scientifically vacuous is once again beautifully exposed:
The theory of intelligent design is not only not falsifiable; there is simply no way to test it. But that is not the main reason it is not science. The main reason is, that ID does not actually explain anything. When we ask, “Why is the world the way it is?” it answers, “Because it was designed that way.” The world is the way it is because it is that way. That might be the furthest from a useful, satisfactory explanation you can get.
Or “As Columbia University physicist Brian Greene says, “
Brian Greene wrote:
“String theory is a work in progress. It is science because in its decades of development it has always adhered to the well-established methodology of theoretical physics. So far, we have not revealed enough about string theory to extract detailed predictions that are within reach of today’s technology. If, however, we believed that this latter goal of testing string theory were permanently unattainable - as it most certainly is for ID as currently presented - we would no longer work on the theory. As of now, there is no way to tell how things will pan out. But that’s what theoretical physics is all about: Devise theories, analyze them with rigorous mathematical tools, do your best to extract experimental predictions, and test them. No one can predict how long each individual step in this progression will take.” So be patient!
For an indepth interview with Brian Greene on Nova click this link
At the “He Lives” website David Heddle who describes himself as a ‘reformed nuclear physicist” discussed Susskind’s latest book titled “The Cosmic Landscape: String Theory and the Illusion of Intelligent Design “. In Susskind’s Sophie’s Choice, Heddle describes his ‘objections’ to Susskind’s solution to the anthropic principle. Since Heddle has much invested in his Cosmological argument, it should not come as a surprise that Heddle objects to Susskind’s arguments. Ironically however he seems to miss the irony in the following statement:
David Heddle wrote:
Susskind has presented the physics community with what is, for some (not this writer), a Sophie’s Choice: a hidious, complictated, unfalsifiable String-Theory Landscape, or Intelligent Design.
What Heddle forgets to mention is that Susskind’s ‘multiverses’ are a direct consequence of the well supported inflationary theory. Intelligent Design however has no such basis in theory. In other words, why should David’s cosmological argument for ID be seen as scientific when it fails the same standards?
Let me try to give my best understanding of string theory. String theory tries to combine Relativity and Quantum Mechanics into a single theory. Since there are occasions where we need to apply both relativity and quantum mechanics, such a theory is needed.
An early attempt to extend space to 5 dimensions was the Kaluza-Klein compactification. By expanding space to 5 dimensions, electro magnetic force and gravity could be unified. The 5th dimension’s size was so small however that it remains invisible to direct observation. When the weak and strong forces were discovered, the Kaluza Klein solution seems to have failed as it could not explain these additional forces. By extending the dimension to 10 or 11, string theory however can explain and unify these forces. At the moment most work is done to reconcile these models with known principles and observations.
One of the aspects String theory deals with better than particle physics is the treatment of particles of having zero size, leading effectively to singularities. In String theory the particles interact at a Planck distance which resolves the problem with particles.
In the original work of Kaluza it was shown that if we start with a theory of general relativity in 5-spacetime dimensions and then curl up one of the dimensions into a circle we end up with a 4-dimensional theory of general relativity plus electromagnetism! The reason why this works is that electromagnetism is a U(1) gauge theory, and U(1) is just the group of rotations around a circle. If we assume that the electron has a degree of freedom corresponding to point on a circle, and that this point is free to vary on the circle as we move around in spacetime, we find that the theory must contain the photon and that the electron obeys the equations of motion of electromagnetism (namely Maxwell’s equations). The Kaluza-Klein mechanism simply gives a geometrical explanation for this circle: it comes from an actual fifth dimension that has been curled up. In this simple example we see that even though the compact dimensions maybe too small to detect directly, they still can have profound physical implications. [Incidentally the work of Kaluza and Klein leaked over into the popular culture launching all kinds of fantasies about the “Fifth dimension”!]
An interesting overview of String theory and what has been accomplished is given here
Another major flaw of the standard model is that it describes the interactions of elementary particles but not where they come from. This knowledge is known through experimental data only. String theory should explain where the four forces come from, why the particles that we see exist, why these particles have the masses and charges that they do, why there are four spacetime dimensions that we live in, and the nature of spacetime and gravity 3. As strings move through time, they trace out a worldsheet similar to the worldlines of point theory. They vibrate, and these different vibrational modes give rise to the various particles that we can “see”. The different modes are seen as the different masses and spins. String theory possesses the necessary degrees of freedom to describe all known interactions–something that cannot be said about the standard model. These degrees of freedom arise from the spacetime dimensions that strings live in. Whereas we can only see four spacetime dimensions, string theory has ten or eleven. Six or seven of these dimensions are curled and thus effectively invisible; the idea is that motion in these compacted dimensions gives rise to the properties of the particles 2. Kaluza-Klein showed that if a fifth dimension were compacted and added to our spacetime, it would allow a four dimensional theory of general relativity plus electromagnetism. If the electron is allowed this extra degree of freedom, then the photon arises and the electron obey’s Maxwell’s equations 3. Elimination of the extra dimensions through Kaluza-Klein compactification or constrainment of matter and gravity into a three-dimensional subspace called the three brane is called braneworld theories 5. In the case of Kaluza-Klein compactification, the extra dimensions are wrapped on Calabi-Yau Manifolds and Orbifolds that are far too small to be seen with modern technology 2. The extra degrees of freedom afforded by string theory explains more than electrons. They predict the existence of the graviton, include the same gauge theories as the standard model, and predict supersymmetry at low energies such as the electroweak scale. Current particle accelerators are only reaching to about 10^(-16)cm, so point-particle approximations are still successful as approximations. Once accelerators reach smaller scales, however, supersymmetry may be revealed and point-particle approximations may prove to be incorrect 4.