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## Can anyone explain to me what 'string theory' is?

I know this is a stupid question, but I've heard about string theory many times, but have no clue what it really is. Please understand I have very little background in physic. Do you have a good explanation about what it is and why it matters a lot in our universe? Thanks!

• #### Thomas Reddy

• +7
May 23 2012: Here are the things that are likely to be most important for you to know about String Theory
1) It hasn't been observed experimentally, nor are there any experiments which have been conceived that could verify or falsify it. It is currently a mathematical framework that does a decent job of describing phenomena we know, and may tell us something about why certain things are the way they are.

2) String Theory is about the smallest of scales. Atoms are made up of Protons, Neutrons, and Electrons. Protons and Neutrons are made up of a range of Quarks. And the whole mess of them are theoretically made of tiny little vibrating strings.

3) Sting Theory may provide physicists with a way to unify all of the forces of nature into one basic force that just behaves differently in different situations... This is like how Electricity, Magnetism, and Light can appear to be three very different things, but when viewed in the correct way can be represented as different expressions of a single electro-magnetic force. In this way, scientists hope that string theory will be able to combine Gravity & electro-magnetism into one force. (It would also combine the Strong and Weak Nuclear forces which are the two other known fundamental forces.) This may not seem like a big deal, but it's huge.

4) In addition to understanding "HOW" the universe works the way it works, it could help us begin to answer some of the "WHY" questions... Or if not answer those questions, at least correctly frame the "why" questions. Why are there X fundamental particles, and why do they have the values they have? Why is value of the speed of light the value that it is? Why is gravity as strong/weak as it is? etc... String Theory probably won't answer many of these questions, but it's an attempt to try.

5) The mathematical framework of String Theory is really complex and un-intuitive, that doesn't mean it's wrong. But it is the source of much of the criticism of String Theory.
• #### Felippa Amanta

• 0
That actually explains a lot for me, I think I might have just the simplest idea of this very complicated concept.
I may not understand the whole String Theory, but it gives me a realization that our universe is beyond mind-blowing!

Thanks for the video too, I'll definitely take a look at that after my finals. :)
• #### peter lindsay

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May 24 2012: A very useful reply Mr Reddy maybe you should write for documentaries. If only they would stop discovering new stuff we might get a unified theory. It will be interesting to see how dark energy impacts on string theory if we have a fifth fundamental force bacause of it.
• #### Paul Limbers

• +3
May 23 2012: I'm no expert but my understanding is that string theory is trying to get to the smallest scale of physical matter. Originally atoms were thought to be the smallest particles of matter, but then we discovered protons, neutrons and electrons and then quarks, bosons, fermions etc. String theory suggests that electrons and quarks (which have been thought to be dimensionless objects) are actually vibrating one dimensional 'strings' that are the fundamental units of all matter and forces. It is a mathematical model rather than based on actual observation though, as there are inherent difficulties with trying to observe matter on that scale. The main benefit is that it allows for quantum field theory to be consistent with general relativity. I hope that makes some sense and actually helps.
• #### Felippa Amanta

• 0
It makes a lot of sense to me. I can start to imagine the idea of it.
Funny thing is, I just came out of my physic class which still explains how atoms are the smallest of all. This new revelation about the String Theory changes the way I think! Once again, thanks :)
• #### Thomas Reddy

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May 24 2012: Well, most of the world we interact with can be explained very well by saying that protons, neutrons, and electrons (the building blocks of atoms) are the smallest things. You can get through 4 years of Chemical Engineering which is heavy on Physics and Chemistry without having to talk about Quarks.

Get a handle on whatever physics class you're in. After you get through Mechanics and E&M, you'll be better equipped to start looking into some of this other stuff, but String Theory is really the end of the line on this stuff. Pick up Hawking's "Brief HIstory of Time", it's a good read and it goes a long way to introducing you to the more exotic stuff. Or go and find anything and everything by Neil DeGrasse Tyson when he's talking, he's electric. Brian Cox is also good at explaining things, take a gander at his stuff on here, or a 1 hour special he did in Britain: http://www.youtube.com/watch?v=4f9wcSLs8ZQ
• #### Felippa Amanta

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May 24 2012: Yeah I really love Neil DeGrasse Tyson. Michio Kaku is also my favorite.
Thanks for the recommendation :)
How about Hawking's The Grand Design? Which is better for a starter?
• #### Dyed All Hues

• +2
May 25 2012: This simplest explanation I know is to start to imagine a huge loaf of bread with infinite length, and that huge loaf of bread is sliced into its individual slices, and in each slice of that infinite loaf is something unique and different about that slice. Now look get your own loaf of bread and slice that bread into smaller individual pieces by hand. Investigate each slice and you will see that each slice is different, and that is the multi-verse definition for string theory.

The additional understanding I have realized it that music's effect on you is evidence enough to find that each Quark vibrates to a similar vibration, which is similar to the effect of listening to music we love or hate. Music tunes into our vibrations which connect with us deeply and the lyrics adds a bigger impact in addition to the music you find so catchy. =)

Thanks for reading my thoughts. Hope that helped. =)
• #### Felippa Amanta

• +1
May 26 2012: hahaha! Now this is a very interesting analogy.
And now you got me thinking about music too!
Thanks a lot :)
• #### Dyed All Hues

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May 29 2012: I'm happy to make you think of music. =)
No problem. =)
• #### TED

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May 24 2012: Hi Felippa,
It's not a stupid question. We're glad to see you use TED Conversations for learning purposes!
Thank You,
TED Conversations team
conversations@ted.com
• #### Felippa Amanta

• +2
May 26 2012: aw thanks for the encouragement!
I'm glad I stumble upon TED. TED has really change the course of my life. :D
• #### Ric Shanahan

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May 24 2012: Hi Felippa, String theory is one attempt to explain how matter gets its properties such as mass and gravity. It does this by attributing each known particle as if it were a string vibrating in different frequencies such that each vibration frequency ties in to a certain characteristic of the particle. No question is stupid!
• #### Felippa Amanta

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May 26 2012: Thanks for your answer Ric! It's very easy to understand :)
• #### Enrico Petrucco

• +1
May 26 2012: M-Theory is the unifying mathematical description of a theory of everything whereby a vibrating 1 dimensional string represents an energy unit that interacts with a subset of 11 dimensions to yield part of the observable (and unobservable) universe.

The first thing one learns in Quantum Physics is that matter is merely constructive interference of energy. M-Theory exhibits the case for all particles and attempts to rigorously describe each manner of energy interaction.

It only matters insofar that humans wish to understand the Universe and to do so in the most elegant manner possible. M-Theory is the mathematical means to that end and may aid human exploitation of the Universe.

Non-mathematical means seek to understand the Universe less explicity, yet are equally relevant.
• #### Benjamin Liu

• +1
May 26 2012: http://xkcd.com/171/ (A humorous, but perhaps truthful, answer that scientists give: "I dunno")
http://www.pbs.org/wgbh/nova/physics/conversation-with-brian-greene.html (If you like Brian Greene, check out this interview)
Also, you should watch Brian Greene's "The Elegant Universe" which seeks to educate the general public on the mysteries that physicists such as Stephen Hawking try to solve.

If you want to understand the universe you will encounter two branches of theoretical physics:
1. Quantum Mechanics
2. General Relativity

Quantum Mechanics seeks to understand the smallest particles in the universe, even smaller than the atom. In this realm, there is something called the "Uncertainty Principle." It says the closer you get to a particle, the less you know about its motion. Strange? Definitely--the quantum mechanics realm is perhaps as strange as you can get! Particles literally teleport from place to place all the time. In this realm, unreality blends with reality in a strange way. Unfortunately, you really do have to have a mathematical background to truly appreciate the phenomenon you see here.

General Relativity is a realm totally opposite of quantum mechanics, as it deals with objects in our universe. Partial differential equations are able to predict space and time of objects. Einstein is perhaps the pioneer of this study. General relativity introduces what Einstein called the 4th dimension known to us as time and made the amazing claim that gravitation is actually the curvature of space and time.

String theory tries to unite these two concepts into one theorem as part of the search to find "The Ultimate Equation," which I particularly doubt we will find. It's hypothesis is that electrons and the quarks that make up an atom (which make up elements, which then make up chemical structures, then cells) are 1-dimensional "strings" rather than simply points. As xkcd jokes, the theory does not have a useful stance...yet. But this IS the future of physics.
• #### Enrico Petrucco

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May 26 2012: I quite enjoy the idea that anywhere in the observable Universe that we find nothing, there is a non-negligible amount of destructively interfering energy and within unobservable dimensions (dark energy) and that within the Universe it is currently greater than the amount of constructive interference observed. The same applies to constructive interference of energy in unobservable dimensions (dark matter).

;-)
• #### Daxesh Degdawala

• +1
May 24 2012: Stephen Hawking is my favorite author. If v r interested in physics then v always eager to know about Hawking's theory. very good person he is!
• #### Daxesh Degdawala

• +1
May 24 2012: String theory refers to mathematical models in attempts to find an explanation for the four main physical forces. These forces are gravity, the electromagnetic force, the strong nuclear force and the weak nuclear force.
Classical physics describes the universe as made of small particles (points) which are static (not moving) and unchanging. In contrast, string theory describes the particle as a string or line (not a particle or point). The string forms the four different forces by vibrating in different ways.
• #### Robert Winner

• +1
May 23 2012: It has to do with wrapping presents at Christmas time. To tight the box gets crushed. To loose the wrapping paper falls off and your present looks bad and your wife gets mad at you. Glad I could help. Just a regular Joe. Bob
• #### Paul Mullins

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Jun 5 2012: all matter is made up of tiny tiny strings vibrating at various frequencies.
• #### lo xueyu

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May 26 2012: good question, but I'm not sure whether i am correct comprehension. so sorry to barely show you the explain.
• #### Benjamin Liu

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http://en.wikipedia.org/wiki/String_theory
http://superstringtheory.com/

And...you can actually watch the entire "Elegant Universe" here!
http://www.pbs.org/wgbh/nova/physics/elegant-universe.html
• #### Daxesh Degdawala

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May 26 2012: @ Felippa Nice question asked by you. I really appreciate with you.
• #### Felippa Amanta

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May 26 2012: Thank you for your encouragement, and for taking the time to answer my question. I really appreciate your answer too! :)
• #### Daxesh Degdawala

• +1
May 27 2012: @Felippa I have too many friends in china, very intelligent lady they are like you. Happy to meet you and especially for your interest in Physics. Its a very good subject. I always encourage to those people who really interested to know and to do something new in their life.
• #### Dan F

• 0

String theory is a creative and theoretical attempt to reconcile how the General Theory of Relativity and Quantum Mechanics can be incorporated into a single unifying theory.

I have found understanding physics gets acceleratingly wild as you work backward toward the fundamentals in an attempt to understand why our physical world behaves the way it does, or seems to.

You possess one of the most fundamental gifts of all - curiosity. Welcome to TED.
• #### Felippa Amanta

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May 26 2012: Thank you for the warm welcome!

It is really wild, but at the same time very exciting. Even when I know so little about physics, the broad possibilities of our universe is just mind-blowing!

Oh, and thanks for the recommendation :)
• #### Vidyardhi Nanduri

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May 24 2012: If you are inquisitive- you qualify for cosmos quest. I question stephen Hawking because , he has not understood the cosmic function of the universe. East west interaction helps you to search origins- Cosmology Vedas Interlinks.
multi-Universe concept is introduced by me dec 1999- Cosmologyreview [dot] com -available through
www [dot]scribd[dot]com/doc-27460496/THE-COSMIC-VISION-OF-THE-UNIVERSE-PART-1-BASIC-APPROACH-Dec-1999
• #### Orlando Hawkins

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May 24 2012: I am obviously far from being a scientist but from what I read about it in the past (and from what many have already mentioned) it is really attempting to explain matter to its basic atomic constituents.

also from what I read from Kaku, string theory may have some relation to explaining what dark matter is, so if you understand string theory it may give you some insight to the nature of and structure of dark matter...

• #### Felippa Amanta

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May 26 2012: So you've read Kaku's book? Would you recommend it?

And one more question, what's a dark matter?
• #### Orlando Hawkins

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May 29 2012: I cannot exactly say I read his book but I did read excerpts from it. The passages in his book were part of a larger anthology that I was reading but yes it was an excellent read and I would recommend it. The part that stuck out to me was when he mentioned how the government shut down studies for dark matter (or how the government stopped funding for this one device that would help scientist understand dark matter). This is interesting being that understanding the nature of dark matter would mean understanding much of our universe and its origins, which I am sure the government would have been interested in. the device was actually designed to understand more about string theory.

As for dark matter, in a nutshell it is unseen matter that seems to be attracted to gravity. As mentioned before, no one can see dark matter but you can see its effects or influence on other bodies from the universe. For example, light cannot pass through dark matter. it can only go around dark matter. Also without it, many things in space would just fly off randomly. Galaxies would also break apart. Many astronomers and physicist realized that the bodies on the outer parts of galaxies were moving just as fast as those closer to the center part of the galaxies. This was quite odd because the outer bodies, moving at such a fast speed should have flown off into unknown space but they didn't and this concluded that there was something keeping the galaxies together and calculations showed that there was more mass than what people could actually see.

String theory relates to this because many believe (or at least used to believe) that the constituents of dark matter, were actually sub-atomic, so seem theory in relation to dark matter is breaking down dark matter (or matter in general) to its molecular and basic constituents.
• #### Paul Limbers

• 0
May 23 2012: No worries Felippa, I'm glad I could help :) Though, it might be worth noting that it's not unanimously accepted at the moment, it's still a bit contentious. But yeh, strange about your physics class haha.
• #### Krisztián Pintér

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May 23 2012: sorry for disappointing you, but probably not. even to have a glimpse of it, you need advanced math.
• #### Thomas Reddy

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May 23 2012: I don't agree with that. There are a number of very skilled physicist/lecturer/science popularizers who can condense the general sense of String Theory into a form digestible by people without real knowledge of advanced science and math. It probably takes more than the 2000 characters we have here though :)

It wouldn't be enough for a person to make predictions, or really use the theory in any way, but it would be sufficient to understand the concepts in play.
• #### Krisztián Pintér

• 0
May 23 2012: can you give us an example?

i have a BSc degree in chemical engineering, and i work as a computer programmer, so math is kind of my my thing. i managed to somewhat understand special relativity, and i have a clue what general relativity is about. they tried to teach me quantum mechanics with little success, but i passed the exam. i watched the talk of brian greene here:

http://www.ted.com/talks/brian_greene_on_string_theory.html

but all i got is i don't get it. i understand the metaphors, but i have no clue how this theory actually works. i also read some book of stephen hawking, as he explained some new way to describe spacetime in order to get rid of the specialness of the time dimension. the guy struggled to make it available to the reader, but but basically he said what i described, and nothing else. everything else would be hopelessly abstract postgrad math.

einstein said: everything should be as simple as possible, but not simpler. i believe for these advanced theories, as simple as possible is way more complex than we can grasp.
• #### Thomas Reddy

• 0
May 23 2012: So, I was going to point to that video to help out the uninitiated. Another helpful one is: