Brian Greene yes but string theory no

Tuesday 15 March 2016

Dr Brian Greene

In summary

Commentary for The Conversation by Dr Alan Duffy, Centre for Astrophysics and Supercomputing, Swinburne University of Technology.

‌Alan Duffy, Swinburne University of Technology

Saturday 19th March will see me standing on stage at Melbourne Park chatting to one of the most famous figures in physics and string theory, Professor Brian Greene, as part of his Think Inc tour of Australia.

While I may like the man, I’m not such fan of string theory. But more on that later.

On that stage I will be nervous not just because of the thousand faces watching, but because this scientist has done more for the popularisation of science than almost any other figure. I am going to be a professional and not let him realise it but, just between you and me, I will be fan-boying pretty hard.

Brian Greene has written one of the great popular science books of the 20th century, The Elegant Universe, on String Theory. He followed it up with a brilliant discussion of the nature of reality from the world imagined by Newton, to that of Einstein and then beyond in The Fabric of the Cosmos.

If you haven’t read these, or his more recent works (The Hidden Reality or for kids Icarus At The Edge of Time), I would recommend them. If you’re pressed for time, at least catch the TV series of these books. These are fantastically informative and he manages to not pull any scientific punches, instead using imaginative story telling to make the extreme seem approachable.

He took this accessibility to the Stephen Colbert show, giving one of the best explanations I’ve seen of the recent gravitational wave discovery.

Brian Green on the Late Show with Stephen Colbert.

As if all that wasn’t enough, he and co-founder Tracy Day established the World Science Festival (currently running in Brisbane). WSF celebrates science on a world stage, with over a million visitors since 2008. Suffice to say Brian Greene will be interesting to chat to. That he has done all this while having amassed over 80 published, peer-reviewed articles accumulating over 3,000 citations in total is simply incredible.

Is this all there is to it? xkcd

However, while I clearly admire the man and his efforts, I’m not such a fan of one of his major research topics, string theory. The idea is that all the subatomic particles of nature can be represented as different vibrations of higher dimensional strings. It is hoped that this may link the two pillars of modern science, Einstein’s general relativity and the Standard Model of particle physics (quantum mechanics), into the long-sought after Unified Theory. String theory is arguably one of the most audacious mathematical feats humanity has ever attempted.

It’s also unfortunately a feat that, at this time, has little predictive power which is the bedrock of any compelling theory. Or rather it predicts too much suggesting that our universe is but one of an unimaginably large number of potential universes (10 followed by around 500 zeroes) called the String Landscape.

In each of the universes the various parameters that make up our universe may change giving a very different looking universe even if the laws are unchanged. You can explore these yourself and see if stars like our sun live long enough to produce life for example.

It’s not clear whether there is a way to select or devise our universe from amongst these options. Or we can appeal to the anthropic principle that we find ourselves in one that is suitable for life, else if it weren’t we wouldn’t be here to wonder. This latter issue has caused huge battles between greater minds than mine, such as the Smolin-Susskind debate.

While Shakespeare’s Hamlet may once have remarked that “there are more things in Heaven and Earth, Horatio, than are dreamt of in your philosophy”, he was clearly excepting string theory from these philosophies as it contains everything and more.

Whether you see this as a strength, or as I, a weakness for a theory might be a subjective matter of taste. Objectively however it is clear that thousands of brilliant minds have been dashed against the rocky cliffs of the String Landscape, with no end in sight.

As a physicist I use less ambitious (though still astounding) but more predictive theories such as general relativity and the Standard Model rather than string theory, as I want answers to my questions. Which makes it so exciting to be able to ask a great mind such as Brian Greene all about this theory and more!

The Conversation

Written by Alan Duffy, Research Fellow, Swinburne University of Technology.This article was originally published on The Conversation. Read the original article.