Yesterday, Quirks and Quarks (the Canadian Broadcasting Corporation's brilliant weekly science radio show) aired a fantastic segment on string theory and the origin of the universe, entitled "Before the Big Bang." I've been reading and hearing about string theory for a decade now, but haven't quite managed to make sense of it. After hearing yesterday's Quirks, I feel like I'm getting in the ballpark (it doesn't hurt that the production values for this episode are really high, with great, witty edits).
The Big Bang theory of the origin of our universe is widely accepted by the physics community. The idea that our universe started out as some infinitesimally small point, which expanded out to what we see today, makes a lot of sense. Except for one small thing. That initial point, called a singularity by physicists, is a physical impossibility. According to the models we have today, the temperature of the universe at that first moment would have had to be infinite, which mathematically makes no sense. Also, the singularity doesn't do a good job of explaining where all the matter and energy we see today in the universe came from. So, physicists are increasingly starting to look at other branches of physics to see what they can do to replace the singularity with a more reasonable proposition, one which can actually be explained by existing science.
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String theory, religion for scientists.
I was dozing while listening to this episode, and had quite possibly the most insane yet informative dreams of all time.
Is that a criticism or a bumper-sticker?
I am def. getting that printed as a bumper sticker:)
http://www.thetroublewithphysics.com/
Lee Smolin lays it out. Don't let string theory make you it's bitch.
Remember, String theory isn't testable, so it isn't a theory, it's a fantasy.
"In the beginning there was nothing, which exploded. "... Douglas Adams
Maybe physics itself changed at the moment of the big bang. Maybe these forces didn't always work the way they do today.
For now, it seems like there is no reasonable alternative to the Big Bang theory, flawed though it may be.
Q&Q is one of the best science programs available. When I compare it to NPR's pathetic "lowest possible denominator" attempt at bringing science to the public as exemplified by Ira Flatow's "Science Friday" it explains a lot of our lame public policy debates regarding our technological culture-scape.
The Flying Spaghetti Monster is sort of "stringy." Does that help?
•)
"That initial point, called a singularity by physicists, is a physical impossibility."
I think I have a lot of evidence to counter this...
On second thought, maybe new universes are merely shitty analog copies, and black holes are just giant analog copy machines (analog holes?). You now how each generation says that things-are-getting-worse/are-not-as-good as they used to be? This explains it. We started with the "digital studio master" edition, and now were down to "eight track."
Actually, this explains a lot of things.
•) - happy mutant emoticon
String theory isn't religion. It's pre-Enlightenment science. It's science from before the modern scientific method, where experiments and testing were less important and the people who wrote most persuasively (or had the most influential supporters) won.
@ZDepthCharge:
"I emphasize that string theory is among the ideas I believe are worth still exploring." -- Lee Smolin, http://www.thetroublewithphysics.com/Response%20to%20Polchinski.html
(in which he also admits that it is possibly falsifiable.)
Correction: Smolin admits, at the link above, that individual instantiations of free parameters in various kinds of string theories are sometimes testable, while maintaining that "string theory" as a whole is not falsifiable (because, for example, it encompasses an infinite number of specific theories, some of which are not testable; much like "logic" is an untestable-as-a-whole collection of different systems of reasoning).
Take a look at Newton's theory of gravitation--it does not explain what gravity is yet it provides a mathematical description of how it works, much like how string theory is a mathematical description of how the universe works. Einstein's theory replaced Newton's because it had greater explanatory power, not because Newton's was falsified.
Actually, Newton's law of universal gravitation has been falsified...
Here is the mp3 in a direct link
http://podcast.cbc.ca/mp3/quirksaio_20071103_3793.mp3
Quirks & Quarks also gets extra credit for offering an Ogg Vorbis version of the show.
XKCD provides a simple, concise and correct statement of string theory.
"String theory" is a family of theories that have proven to be a) mathematically interesting b) physically intriguing and c) extremely difficult to build models out of. The last point is what the punchline of the cartoon is referring to, and it is a huge problem for string theory as physics. There is a lot of lovely math, but no one knows if any of it describes (models) the universe we live in.
A longer but excellent account of the current state of modern physics (by a model builder, not a string theorist) is Lisa Randall's Warped Passages, which explores the problem of extra dimensions, which are critical to making string theory work, and which have been a feature of most grand unified theories since the '30's.
Not being falsifiable does not necessarily make something false.
It just makes it frustrating to think about.
There's a chance that in the future, it will become falsifiable.
It's worth thinking about, at least.
#1 String theory is a model, and if it can help to understand our universe then fine; if it predicts things that we did not know and can verify with experiment, then it can be validated as a useful model. So far, it's just a really neat idea.
#2 The temperature being infinite is meaningless, in that temperature is a relative measure of energy. When you have all of existence in a singularity, there's nothing for there to be a relative measurement to. It's like trying to comment on the wavelength of the sound of one hand clapping. :D
For completeness, the xkcd comic about string theory:
http://xkcd.com/171/
As an experimentalist, I like to mock string theory. But it is the leading theory that explains a lot of the universe.
A problem with string theory is that it can't predict which universe we're in. However, if you combine it with another idea of low intellectual merit - the anthropic principle - and you have a way of selecting the right universe.
As a physicist I hope it's wrong, but suspect it might be the best we'll see for a long while.
- FA
The question of what came before the Big Bang, or before Planck Time, is really interesting. Recently I read an article about one of the main problems confronting astronomers when they try to peer back in time 14 billion years. Right now we supposedly can see back 12 billion years, but since the Universe theoretically is 14 billion years old, once we see back 14 billion years we won't be able to see any further. This is because light itself came to be 14 billion years ago as did space-time. So to see 'before' the emergence of space-time is seemingly impossible.
Physics seems to be interested in what the fundamental 'stuff' is that makes up everything. Strings are one theory. They are supposed to be Planck Length vibrating strings instead of tiny points.
Since there are a number of different String Theories, M-Theory is thought to be the underlying theory of all string theories.
It's all quite complicated but M-Theory is supposed to be an alternative to the usual Big Bang Theory that implies the universe emerged out of a seemingly impossible infinite point. M-Theory suggests the whole universe is made of 4 dimensional Branes underlying 11 dimensional space-time.
It all sounds pretty spooky to me though.
I subscribe to the view that the rules of the game were different then. I think of the pre-bang state as being analogous to an unobserved quantum phenomenon, with an infinite number of conflicting potentialities. At the moment of the big bang, all of the other probability waveforms collapsed, leaving us with the dimensions, laws, constants, etc. that we now observe. And if you take time to be one of those things which settled into being at that “moment,” then there is no “before” to examine. Don’t that just bake yer noodle?
What I want to know is how the science radio show came before the Big Bang.
@21: "It all sounds pretty spooky to me though."
"spooky" as in "spooky action at a distance"? I think that's what Einstein called quantum physics.
Surprised nobody posted a link to this yet--
http://www.pbs.org/wgbh/nova/elegant/program.html
Best episode of Nova Ive seen
Im not too worried about it not being testable yet. It took 20 years for technology to advance enough to detect background radiation and prove that the big bang theory was right. This might take a little while too.
I strongly agree with the above, skip the popularized 15 minute gloss found in most media (and podcasts!), and look to much more detailed explanations like those offered by Lee Smolin.
I find it find extremely disappointing that, despite there being so many science programs available on the internet, they remain high level, popularized and without the detail and insight required to get a coherent picture of modern physics. I do like Q&Q, I have been a huge fan of Bob McDonald since I was about 5 yrs old when he hosted a kids science show on the CBC, it was brilliant - but this report was uninformative to knowledgeable laymen, and a mediocre introduction for initiates. I truly desire science programming, on the internet, on tv, or on the radio to be at a level sufficient to challenge those with a decent lay familiarity - like NOVA used to be.* Rather than attempt to pander to the uniformed masses, trying to draw them into something well beyond their scope with flashy graphics, soft metaphors, and fancy editing. Science for science sake, damnit! Its supposed to be hard.
For those interested in this topic, please do look to Lee Smolin's writing. His 'Trouble with Physics' and 'Three Roads to Quantum Gravity' are some of the most brilliant science writing I have ever encountered.
*NOT like the Elegant Universe - very disappointed in that series as it was a hyperventilating whirlwind barely scratching the surface. (Although, there were some very good interviews included)
the science show, on australia's abc radio national, is thoroughly worth listening to too. it's been going since i was a little kid, and it's still presented by robyn williams (who seems to show no signs of aging).
the 4 most recent 4 episodes are always downloadable and there are transcripts available for each story in all but the most recent episode. here's one, for example, on a giant radio telescope made from chicken wire.
it looks like you can subscribe to both audio and text versions, which is neat; both links are found here:
http://www.abc.net.au/rn/scienceshow/
I cleverly managed to mess up the link to XKCD above, so here it is again:
String theory in a nutshell.
Russell's description of the situation really is an accurate summary, as he says, on many levels.
When Stephen Hawking was asked "What came before the Big Bang?", he famously replied "What's north of the North Pole?"
Another really good science podcast is SETI's Are We Alone, hosted by Seth Shostak and Molly Bentley. Great interviews with scientists complete with purposely horrible science puns: http://radio.seti.org/
@28
XKCD is writting by Randall Munroe, not Russell.
As far as infinite temperatures goes, that's not inconceivable or impossible at all, at least in the broad view. See the sci.physics FAQ, Below Absolute Zero. Infinite and negative temperatures are possible under certain definitions of temperature. Granted, a temperature of exactly 0 still isn't achievable... you get to the negative temperatures by wrapping around past infinity.
If string theory is a partially non-falsifiable family of theories, it's a partially non-falsifiable family of theories that's taken seriously by well-informed people who are in the habit of thinking scientifically.
IanM (29), have you run into any of Chad Orzel's posts in which he attempts to explain quantum physics to his dog?
Cosmological observations provide an incredibly rich set of clues to the pre-big bang universe. Do you see any flaws in: The Pre-Big Bang Universe at BigCrash.org?
… In the beginning (in the pre-big bang universe) there was only the vast vacuum of space and time. But this vacuum was not sterile, it was seething with vacuum energy. This vacuum energy field permeates and defines the universe, an astronomically large sphere of energy. And just as matter generates gravity by warping space and time, so does energy and this is the force that defines the size and shape of the universe, and also the force that bestows mass on matter…
…When a virtual matter/anti-matter pair becomes a matter matter pair, the virtual particles are no longer able to mutually annihilate and they become real, stealing energy from the vacuum energy of space. This is the mechanism of slow matter creation in the first phase of the pre-big bang universe. Over perhaps a billion billion years, clouds of matter form over the entire universe, and eventually coalesce into cosmological bodies and eventually the first pre-big bang black hole, which starts the second phase of the pre-big bang universe, fast accretion of matter from vacuum energy by black holes…