The classic example of the supreme accuracy of QM (actually QED) is the determination of the magnetic moment of the electron. Theory and experiment agree to an accuracy of .00000001 per cent.
But as you say there have been so many gazzilions of tests of both that arguing as to which is more thoroughly tested is silly.
I think you mean GR not SR.
I read that and fun as it was trying to recompile my brain I can’t help but think they are playing a bit fast and loose with what exactly “nothing” means (they even say as much in one part). They also mention that the universe could not quite have started from literal nothing but rather a tiny amount of energy. Miniscule as that may have been it is not literal nothingness.
It seems they want you to think we are talking about:
0 = 0
The reality seems to be more:
<Really, Really Small Number as to be practically, but not, zero>=2+3+4+5-14=0
Perhaps those two are mathematically equivalent but in the second you are playing with actual numbers (or things if we extend the metaphor to our universe) while the first is nothing to nothing. Replace the numbers with apples and anti-apples if you like. Even the anti-apples have a reality. That it all evens up into a nice mathematical symmetry that equals zero is pretty cool but doesn’t make everything nothing. Even if the whole universe is one apple and one anti-apple you still have apples.
So in the end I think you are still left with my two choices.
Thanks for the catch. I started with SR and got my brain stuck on it added to the fact I conflate the two often (I know they are very distinct…just a lazy brain mixing the names up).
In my layman’s understanding, one of the biggest problems with String Theory (besides the fact that it’s untestable, therefore unfalsifiable, by many accounts), is that it’s looking like String Theory allows so many possibilities within its framework, that hardly anything is ruled out.
Not really, for example String Theory hasn’t been tested at all. I like the phrase “big-picture explanation” to describe the scientific meaning of Theory in layman’s terms.
I’m not sure it is fair to characterize String Theory (or M-Theory I think it is now) as wholly untestable. Certainly there are important aspects to it that are untestable making for one of its main criticisms but I doubt scientists (some reputable ones at that) would continue to hammer away on it unless they had reason to believe they were on to something.
From what I understand they can feel they are on the right track if String Theory produces results that are in line with already tested and established data. So, if they run some numbers through for a situation that match the results given by doing the math in General Relativity they have some reason to think something is working right. That by no means makes it conclusive and far from the end of the road but better than getting nonesense answers out of it.
The way I remember it explained (I think by a book by Michio Kaku) was that each more advanced theory essentially encompasses the theories “below” it. So, you could use Relativity equations to describe two balls being rolled together here on earth. When the numbers are all plugged in and the equation is simplified out pops Newton’s equations that describe the same thing. Newton’s equations are far easier to cope with so for day-to-day things most people use that rather than Relativity equations. However, under more extreme circumstances Newton’s equations fail and we need Relativity to get a good answer. So it is with String Theory that (if it pans out) it should agree with QM and Relativity equations but should succeed in the areas those fail.
I do not know if it is truly reasonable to say that String Theory can be considered worthwhile if it gives correct answers where QM and Relativity reign supreme but it seems a good start if it does. If String Theory then pops out answers (rather than nonesense/infinities) where QM and Relativity fall apart is it not reasonable to suppose maybe it is getting something right there too? Granted we may never know for certain as testing at those extremes where they falter is seemingly impossible but then what theory ever could pretend to describe what happens in conditions only seen at the near instant of the beginning of time itself? If that is the case we may as well stop here and be content with QM and Relativity.
Human language simply has not evolved to properly frame these ideas. The universe has become cooler and less dense as time has progressed. From any local point of view, all other points appear to be moving away. The best description of this phenomenon is “expansion”.
Naturally, we want to ask “Expanding into what?”, since all of our mundane experience with expansion involves expansion into the surrounding space (or spacetime, if you prefer). Our minds conjure up a context.
Personally, I believe our universe does indeed have a hyperdimensional context within which its development can be said to take place. However, we will only be able to detect this context indirectly. Hell, we now understand that we can’t even detect the full scope of our own universe directly – a fact which saddens me profoundly.
Unfortunately, as someone mentioned above, even if we are able to come up with verifiable theories that describe the Big Bang, it only removes the problem another step. No matter what we do, our species is doomed to perish only knowing that “it’s elephants all the way down”. The fundamentally unanswerable question is: “Why is there anything, instead of nothing?”
But as to your specific question, imagine the collision of two hyperdimensional entities. Their intersection might spawn a 4-D (or 11-D for you string theorists out there) dynamic universe, just as the collision of 2 planes would spawn a dynamic line which changes and evolves as the planes move in relationship to one another.
Or imagine a hyperdimensional space which undergoes a rapid expansion, like carbonated water when its container is uncapped. Bubbles form, expand, and burst on the surface or break into smaller bubbles. Our universe may be very similar to such a bubble.
I would be surprised if our universe actually can be accurately described as a Euclidian shape. My guess is that it’s probably a much fuzzier, messier thing.
Yes and no. The best tests of both come in tests of Quantum Electrodynamics (QED) and the other quantum field theories. Quantum field theories are constructed out of a combination of quantum mechanics and Special Relativity (not General, which is incompatible with quantum mechanics), so any test of QED is a test of both SR and of QM. There are also tests of SR which do not involve QM, and tests of QM which do not involve SR; it’s a bit subjective to say which set of tests is more conclusive.
And precisely because it has not made testable predictions not previously made by other theories, I would argue that the term “string theory” is a misnomer, and that it should more properly be called the “string model”. Certainly, it’s far less deserving of that title than is, say, evolution.
Given that QM is so good at describing what happens back to a tiny fraction of a second post Big Bang what GUT (or TOE…never sure which fits) will ever be testable beyond making predictions QM already has. I thought the whole point of a GUT was to merge QM and GR and the only time those two things really need to be merged is in the stupendous energies where quantum gravity effects become important. Since it is not foreseeable for humans to ever build something that could produce such conditions for testing (where the fundamental forces start to unify) can we ever expect any theory beyond QM and GR to pass muster?
[totally gratuitous interjection]
It appears that the Jovians built a GUT energy collider on Iapetus.
Perhaps if we asked real nice they’d let us borrow it?
[/totally gratuitous interjection]
One way to describe it in simple terms, it’s all of space that is expanding. It’s not necessarily expanding ‘into’ anything, it’s just…, getting bigger.
Kinda like imagining you have this sheet of rubber with some dots on it. Now stretch this piece of rubber and the dots will move farther apart. That’s kinda like what the universe is doing.
This is supported, if I recall correctly, by the fact that the energy contained within a volume of nothingness in the universe is decreasing with time. That’s to say, the average temperature of the universe is falling. Or something. I’m sure some cosmologist will come around and either expand on this or just correct me altogether.
It’s not expanding into anything. You have to divorce yourself from the notion that there is something outside the universe. The universe is everything. Dimension is a property of the universe; it doesn’t continue beyond the universe.
To picture this on a gut level, the best analogy I’ve heard is to imagine that you are an ant, living in only 2 dimensions on a surface of a balloon. As an ant, you can travel in any direction along the surface of the balloon, but you can never travel beyond the balloon. The balloon itself can expand, but in your 2 dimensional “ant universe”, there is no outside. Everything just becomes more expanded; it doesn’t “go” anywhere. We lack the ability to intuitively picture a 3-dimensional expanding universe, which is why it helps to subtract one dimension in order to get a feel for the concept.
Scientists have a way to explain the unexplainable. And infinity is probably the most unexplainable reality.
Not sure exactly what you mean there, Gymnopithys, but blowero’s got it as far as my understanding goes. There’s nothing for the universe to expand into because the universe is everything. The universe itself is getting bigger.
While the universe can be described as self-contained, we’re not on safe ground saying that it is “everything” or that there is “nothing outside of it”.
The history of astronomy and cosmology has been marked by a progressive de-centering of our position in the Big Picture. People once thought the Earth stood at the center of the array of sun/planets/stars. People once thought ours was the only solar system. The existence of other galaxies had to be proved. Now we understand that there really is no center at all – “the Big Bang happened everywhere”.
There is no reason to think that our little universe is the only one. It may well be a subdimensional intersection of larger-dimensional universes. There may be self-contained micro-dimensional entities lurking within our own.
And we may be able to some day measure the indirect effects of these contextual spaces. In fact, I’m looking forward to it.
But it has:
Planck-mass relic particles (not found)
Fractionally charged particles like 1/5, 1/11 of electron charge (not found)
Deviations from inverse-square law of gravity on small scales (not found)
Fuzzing of images of distant supernovae due to light scattering of Planck-scale fluctuations in spacetime (not found)
The real problem is the one the CurtC mentioned - that there are so many versions of string theory that failure to find these effects still leaves millions (literally) of theories that might be true.
BTW: GUTs don’t have anything to do with unification of QM and GR. They only unify the three other forces: EM, strong, weak.
Right, I wasn’t completely precise. What I should have said, is that there has been no case yet where:
String theory (or any other proposed quantum gravity model) has made a prediction,
which prediction had not previously been made by established theories,
and a subsequent observation or measurement had been made,
which confirmed that prediction.
To date, most of the predictions of String Theory fall into one of two categories: Either they’re “predictions” of things which we already knew, and which were therefore deliberately incorperated into the model, or we’re nowhere near a level of technology which would be able to test the predictions. It’s conceivable that there exists some simple test which could be performed with current technology, and which could support or refute various quantum gravity models, and physicists (myself included) are trying to find such tests, but thus far, there’s not much to go on.
It’s still incorrect to say the universe is expanding into anything. If there are other universes, they would exist in parallel to ours, not inside or outside. Other universes would not be part of our spacetime continuum, so our universe would not expand “into” them. We didn’t say the universe is “everything” with the intention of excluding the possibility that other realms exist; the intention was simply to explain why it is unneccessary to posit a medium into which the universe expands. I didn’t want to bring up other universes because it just confuses the issue.
But it is correct to say there is nothing outside the universe, or even better, there is no “outside” the universe. “Inside” and “outside” are words that descibe objects in relation to each other. The concept requires matter and dimension to make sense; and matter and dimension are properties of the universe. To think that you could somehow travel to the “edge” of the universe, and then continue beyond it is the same lack of understanding that led people in the past to question what would happen when you got to the edge of the Earth. The Earth isn’t flat; it doesn’t have an edge. So to say another universe is “outside” ours makes no more sense than saying Jupiter is “to the left” of Saturn.
I essentially agree with you (see post #46 above) – although the balloon analogy, while apt, usually doesn’t satisfy folks who don’t grok the concept to begin with, because the only way to picture a balloon expanding is to picture it expanding into 3-D space.
What I disagree with is this:
While “inside” and “outside” become metaphors when we talk of these concepts, as you well know, it is not true that other universes must be parallel only. It is entirely possible that our universe may be “bounded” hyperdimensionally at all points by another universe, just as a point can be said to be bounded by a surrounding 3-D volume. In other words, if it were possible to make the hyperdimensional leap, the leaper would find him/herself necessarily in a particular context (the “surrounding” universe) no matter where s/he lept from.
If our X-dimensional universe was spawned by the collision/intersection of X±dimensional entities, then I suppose the leaper might find him/herself in either of two (or more?) possible “surrounding” universes.
There is no evidence that this is the case. But when we explore possibilities, we can’t (and shouldn’t) discount it.
Then what is a law? As in, the second law of thermodynamics, etc…
IANAS, but I believe the term “law” is used for regular relationships, such as Boyle’s law (a relationship b/t pressure and volume) and the first law of thermodynamics (the change in internal energy of a system = heat added to the system - work done by the system), while “theory” is used for an explanatory framework underlying a wider array of phenomena, such as quantum theory.
But in any case, I don’t think the terms are applied rigorously. The terms are conventions which are not required to be as precise as the laws or theories themselves. But I could be wrong – maybe there’s more to it than that.