Is the universe infinitely complex? Will every magnification reveal yet another level of complexity?
Are atoms the basic building blocks? protons, nuetrons, electrons… do yet smaller elements constitute those bodies?
any thoughts?
is this a subject previosuly tackeld on these boards?
Well, we already know that protons and neutrons and the like aren’t the fundamental building blocks (that is, assuming that one accepts the Standard Model). So to revise your question a bit, are what we currently believe to be fundamental particles truly fundamental or not?
My gut instinct is that at some point, we will reach an end to the layers of complexity. We may not have reached it YET, but I feel that there must be a finite number of fundamental interactions and hence, sooner or later, you can’t go any further down.
Can I prove or even justify this? Not at all. I just take it as a matter of faith, because otherwise my job as a physicist is going to be exceedingly frustrating.
g8rguy,
are you a florida gator guy? a university fo florida garduate or professor?
I’m a UF grad.
I don’t think it matters whether the universe is infinitely complex. Our measurements are necessarily limited, so beyond a certain level, we can’t tell.
AFAIK scientists have identified the basic building blocks of matter. While this claim has been made in the past (such as with the discovery of the atom which means indivisible) I recall reading somewhere that scientists have good reason to think they have reached the bottom of the barrel.
The smallest elements of matter are called Quarks and they come in six varities (NOTE–The names are not representative of anything…the’re just names):
Top
Bottom
Strange
Charmed
Up
Down
I believe there are three other particles that fit in here called the Muon Neutrino, Tau Neutrino and the Electron Neutrino (all forms of an electron I think).
That’s it. Along with these and the four forces of the universe (strong nuclear, weak nuclear, electromagnetic and gravity) you have pretty much everything you need to describe what is around you.
As for verification I think all of the quarks have been found save one (one of the first jobs of the Superconducting Super Collider that was cancelled in Texas was to find that last quark…the energies necessary to get there are beyond current particle accelerators). All of the four forces are well known. The only problem with the four forces is that gravity doesn’t fit into quantum mechanics. A quantum theory of gravity is still being sought and is considered one of the Holy Grail’s of physics right now.
As to how far you can dig down into the universe there is a bottom limit. You cannot keep getting smaller forever. The bottom limit is known as the Planck Length. At 4x10[sup]-33[/sup]cm Planck Length is quite small. There is also a limit called Planck Time that is the smallest time slice that can be measured. Planck Time is how long it takes for light to travel the Planck Length and works out to be 10[sup]-43[/sup] seconds.
So, in short, the Universe is inherently grainy and not perfectly smooth. This graininess is sometimes referred to as Quantum Foam upon which all ‘ordinary’ matter is hung.
very informative, whack
What shape are the ‘grains’ - does anyone know?
Wouldn’t they have to be a cuboctahedrons?
I don’t think so. 10[sup]-33[/sup]cm is really small. I’m unsure of what our current technological limits are but I think probing to these scales is still WAY beyond our capabilities. Maybe there are some mathematical models or geometric reasons that would suggest a preferred shape but I don’t know what those are (or if they even exist).
Seems like someone should be able to deduce it from their knowledge of quantum forces, just as it should be easy to deduce that in the macro universe, things would tend to be spherical due to forces of gravity (if they don’t rotate, in which case they’d be squashed in proportion to their speed of rotation). Is that right?
The statement “the universe is grainy at small scales” is a metaphor, not a literal statement. There aren’t any actual grains. I don’t know what a cuboctahedron is, but I rather doubt that the universe is made out of them. Also, the Planck limits aren’t hard limits. It’s not like everything’s fine at 510^-33, and then at 310^-33 suddenly you can’t see anything. We have reached the limit of constituent elements in the common understanding of the term. If we somehow found something that was more basic than quarks, quarks wouldn’t be “made out” of them in the normal sense.
Also, in a way the question “Is the universe infinitely complex?” is backwards. At first we had thousands of different substances. Then we found that they all were made up of a few hundred atoms. Then we found that each atom was made up of a few dozen partcles. Then we found that the particles were made up of six quarks. So we kept finding that the universe was actually simpler than we thought, not more complicated. So maybe we should be asking “Is the universe infinitely simple?”
[…applauding The Ryan…]
A magnficent expostion of scientific matters for the layman. Thanks, Ryan!
First, to Lolo: yes indeedy! I’m actually a grad student there now.
On to the sciency part. To be thoroughly pedantic, I’ll list all hypothesized fundamental particles (I don’t THINK I missed any).
We have 6 quarks, all of which have been indirectly observed (as WAM stated, up, down, charm, strange, top, bottom); these 6 quarks each come in three “colors,” conventionally taken to be red, blue, and green. There are also the anti-particles.
We have 6 leptons: the electron, the muon, and the tau, plus the corresponding neutrinos. All of these also have anti-particles.
There are several particles that mediate the fundamental interactions: 8 gluons that mediate interactions between quarks, the W[sup]+[/sup] and W[sup]-[/sup], the Z, and the photon.
Two hypothesized particles haven’t yet been seen: the graviton (which carries gravity), and the Higgs (which allows for mass).
We think this is everything, but we can’t be sure. The reason for this is, basically, we can only look so closely at things, because we’ve only built accelerators up to a finite size. It’s possible that entirely new physics happens at very high energies (and correspondingy small distances), and no one really knows what happens there. As far as we know, all particles that I listed above are point particles, so we have reached the bottom of the barrel, but all that really means is that they’re smaller than we can resolve currently.
It’s turtles all the way down!
What do you mean by they aren’t hard limits?
Are they hard limits for humans but not in reality (i.e. the universe can happily do ‘stuff’ below Planck limits but humans are forbidden from seeing that closely)?
Are they not very well defined limits (i.e. we kinda think the limit is down there somewhere…just not sure exactly where)?
Is it that some things down at those scales per force must abide by higher limits while other items can squeeze into smaller limits?
Just curious because I always thought the Planck limits were close to gospel when considering the universe at these scales.
My understanding is that the Planck scale is the smallest at which classical theories have any validity. But I’m not a quantum theorist, so take that with a grain of salt.
Planck scales are scales at which quantum effects become important in looking at the shape of spacetime. They are not hard numbers in the same way that atomic scales are not hard numbers in saying that quantum mechanical effects are important. They give you a guideline as to what sizes one might expect “quantum foam” to be significant, but as with almost everything quantum mechanical in nature, they’re merely guesses as to approximately when you have to worry about something.
Really, the Planck length is just the unique length scale that can be formed by appropriate combinations of Planck’s constant, Newton’s constant, and the speed of light. It’s an order of magnitude kind of thing, nothing more.
Am I the only one here who gave out a dirty little giggle when he read this?
Sooo…what are these grain thingies made of?
g8rguy,
Would you care to enter the stringy realm? Perhaps you could answer the question with an explanation of Calabi-Yau manifolds and how only certain sets n-dimensional solutions exist which define the “shapes”. I get lost somewhere before winding numbers.