David Kirkpatrick

March 5, 2010

Multiple choice theories of everything

Filed under: Science — Tags: , , , , , , — David Kirkpatrick @ 5:30 pm

Back in January I blogged about “the most beautiful structure in mathematics,” the basis of a physics theory-of-everything proposed by Garrett Lisi, That theory is part of an article on “Knowing the mind of God” at NewScientist outlining seven different theories of everything.

From the last link, more on Lisi’s concept”

E8

In 2007 the physicist (and sometime surfer) Garrett Lisi made headlines with a possible theory of everythingMovie Camera.

The fuss was triggered by a paper discussing E8, a complex eight-dimensional mathematical pattern with 248 points. Lisi showed that the various fundamental particles and forces known to physics could be placed on the points of the E8 pattern, and that many of their interactions then emerged naturally.

Some physicists heavily criticised the paper, while others gave it a cautious welcome. In late 2008, Lisi was given a grant to continue his studies of E8.

And here’s the article’s synopsis of string theory, one of the better known ideas out there:

String theory

This is probably the best known theory of everything, and the most heavily studied. It suggests that the fundamental particles we observe are not actually particles at all, but tiny strings that only “look” like particles to scientific instruments because they are so small.

What’s more, the mathematics of string theory also rely on extra spatial dimensions, which humans could not experience directly.

These are radical suggestions, but many theorists find the string approach elegant and have proposed numerous variations on the basic theme that seem to solve assorted cosmological conundrums. However, they have two major challenges to overcome if they are to persuade the rest of the scientific community that string theory is the best candidate for a ToE.

First, string theorists have so far struggled to make new predictions that can be tested. So string theory remains just that: a theory.

Secondly, there are just too many variants of the theory, any one of which could be correct – and little to choose between them. To resolve this, some physicists have proposed a more general framework called M-theory, which unifies many string theories.

But this has its own problems. Depending how you set it up, M-theory can describe any of 10500 universes. Some physicists argue that this is evidence that there are multiple universes, but others think it just means the theory is untestable.

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