R. Windhorst, Arizona State Univ./H. Yan, Spitzer Science Center, Caltech/ESA/NASA
The idea that our Universe is part of a multiverse poses a challenge to philosophers of science.
Is string theory science? Physicists and cosmologists have been debating the question for the past decade. Now the community is looking to philosophy for help.
Earlier this month, some of the feuding physicists met with philosophers of science at an unusual workshop aimed at addressing the accusation that branches of theoretical physics have become detached from the realities of experimental science. At stake is the integrity of the scientific method, as well as the reputation of science among the general public, say the workshop’s organizers.
Held at the Ludwig Maximilian University of Munich in Germany on 7–9 December, the workshop came about as a result of an article in Nature a year ago, in which cosmologist George Ellis, of the University of Cape Town in South Africa, and astronomer Joseph Silk, of Johns Hopkins University in Baltimore, Maryland, lamented a “worrying turn” in theoretical physics (G. Ellis and J. Silk Nature 516, 321–323; 2014).
“Faced with difficulties in applying fundamental theories to the observed Universe,” they wrote, some scientists argue that “if a theory is sufficiently elegant and explanatory, it need not be tested experimentally”.
First among the topics discussed was testability. For a scientific theory to be considered valid, scientists often require that there be an experiment that could, in principle, rule the theory out — or ‘falsify’ it, as the philosopher of science Karl Popper put it in the 1930s. In their article, Ellis and Silk pointed out that in certain areas, some theoretical physicists had strayed from this guiding principle — even arguing for it to be relaxed.
The duo cited string theory as the principal example. The theory replaces elementary particles with infinitesimally thin strings to reconcile the apparently incompatible theories that describe gravity and the quantum world. The strings are too tiny to detect using today’s technology — but some argue that string theory is worth pursuing whether or not experiments will ever be able to measure its effects, simply because it seems to be the ‘right’ solution to many quandaries.
Silk and Ellis also called out another theory that seems to have abandoned ‘Popperism’: the concept of a multiverse, in which the Big Bang spawned many universes — most of which would be radically different fromour own.
But in the opening talk at the workshop, David Gross, a theoretical physicist at the University of California, Santa Barbara, drew a distinction between the two theories. He classified string theory as testable “in principle” and thus perfectly scientific, because the strings are potentially detectable.
Much more troubling, he says, are concepts such as the multiverse because the other universes that it postulates probably cannot be observed from our own, even in principle. “Just to argue that [string theory] is not science because it’s not testable at the moment is absurd,” says Gross, who shared a Nobel prize in 2004 for his work on the strong nuclear force, which is well tested in experiments, and has also made important contributions to string theory.
“Suggestions that we need ‘new methods’ have been made, but attempts to replace empirical testability have always failed.”
Workshop attendee Carlo Rovelli, a theoretical physicist at Aix-Marseille University in France, agrees that just because string theory is not testable now does not mean that it is not worth theorists’ time. But the main target of Ellis and Silk’s piece were observations made by philosopher Richard Dawid of Ludwig Maximilian University in his book String Theory and the Scientific Method (Cambridge Univ. Press, 2013). Dawid wrote that string theorists had started to follow the principles of Bayesian statistics, which estimates the likelihood of a certain prediction being true on the basis of prior knowledge, and later revises that estimate as more knowledge is acquired. But, Dawid notes, physicists have begun to use purely theoretical factors, such as the internal consistency of a theory or the absence of credible alternatives, to update estimates, instead of basing those revisions on actual data.
Dynamic discussion
At the workshop, Gross, who has suggested that a lack of alternatives to string theory makes it more likely to be correct, sparred with Rovelli, who has worked for years on an alternative called loop quantum gravity. Rovelli flatly opposes the assumption that there are no viable alternatives. Ellis, meanwhile, rejects the idea that theoretical factors can improve odds. “My response to Bayesianism is: new evidence must be experimental evidence,” he says.
Others flagged up separate issues surrounding the use of Bayesian statistics to bolster string theory. Sabine Hossenfelder, a physicist at the Nordic Institute for Theoretical Physics in Stockholm, said that the theory’s popularity may have contributed to the impression that it is the only game in town. But string theory probably gained momentum for sociological reasons, she said: young researchers may have turned to it because the job prospects are better than in a lesser-known field, for example.
Historian of science Helge Kragh of Aarhus University in Denmark drew on historical perspective. “Suggestions that we need ‘new methods of science’ have been made before, but attempts to replace empirical testability with some other criteria have always failed,” he said. But at least the problem is confined to just a few areas of physics, he added. “String theory and multiverse cosmology are but a very small part of what most physicists do.”
That is cold comfort to Rovelli, who stressed the need for a clear distinction between scientific theories that are well established by experiments and those that are speculative. “It’s very bad when people stop you in the street and say, ‘Did you know that the world is made of strings and that there are parallel worlds?’.”
At the end of the workshop, the feuding physicsts did not seem any closer to agreement. Dawid — who co-organized the event with Silk, Ellis and others — says that he does not expect people to change their positions in a fundamental way. But he hopes that exposure to other lines of reasoning might “result in slight rapprochement”. Ellis suggests that a more immersive format, such as a two-week summer school, might be more successful at producing a consensus.
- Journal name:
- Nature
- Volume:
- 528,
- Pages:
- 446–447
- Date published:
- ()
- DOI:
- doi:10.1038/528446a
........mass = [M] = kilograms ......length = [L] = meters ........time = [T] = seconds ...frequency = [T^-1] = seconds ^-1 .......speed = [L]/[T] ...... = m/s acceleration = [L]/[T^2] .... = m/s^2 ....momentum = [M][L]/[T] ... = kg_m/s .......force = [M][L]/[T^2] . = kg_m/s^2 ......energy = [M][L^2]/[T^2] = kg_m^2/s^2 .......power = [M][L^2]/[T^3] = kg_m^2/s^3Notice mass [M] is not equal to energy [M] [L^2] / [T^2] ...the vibration is missing Here is what Einsteins famous equation really looks like... [M] [L^2] / [T^2] = [M] [L^2] / [T^2] Energy already is a mass times speed^2. If you could just lop-off parts of an equation and claim whatever is left is equal... i.e. "energy equals mass" then you could also say that "power equals mass" and so does momentum and force. It is really stupid to think like that. Speed is NOT equal to length. Speed is equal to length divided by time. Energy is NOT equal to mass. Energy is equal to mass times speed squared.<-- stupidB) Stuff has always been here<-- insanityC3) Everything was created<--- possibleNOTE: if everything was created the only way to do it is either "1" or "B"~~~●~~~(that's one free string, 18 balled, one free string) A free neutron would look like this●~~~(19 balled, and one free string) A free electron would look like this---∗---(one free string, 18 free strings in a disc shape, one free string) A proton can grab a neutron and an electron.●~~~ ~~~●~~~ ---∗---(NPE on the loose)●●~~~∗---(NPE combined) (that's a neutron with its previously free string balled up together with one of the proton's previously free strings (now also balled up) and the other proton string is twisted with an electron string (that free proton string and electron string twists are still full length)) Two free protons~~~●~~~ ~~~●~~~can combine and still be 2 protons~~~●●~~~(that might look like 2 free neutrons but it is not because there are also balled up strings in the middle of the package holding them together. To clarify: two free neutrons●~~~ ~~~●that are now combined would look like this●●If you throw another free proton into that 2 proton package~~~●●~~~ ~~~●~~~you will get one changing into a neutron when they combine~~~●●●~~~that's Helium-3 If 4 free protons~~~●~~~ ~~~●~~~ ~~~●~~~ ~~~●~~~...grab each other 2 will change into neutrons~~~●●●●~~~And then the outer two that still have a free string can grab electrons...---∗~~~●●●●~~~∗---that's regular Helium, it can also be called Helium-4 If you understand the way this works... with a little thinking anyone can figure out isotopes. For instance why 3 protons would not make lithium-3 ... i.e. why there can be extra neutrons but not just a bunch of protons (or extra protons)... we've just seen that above the way Helium-3 was created. Nucleus 3 can only be helium-3~~~●●●~~~or Hydrogen-3 (tritium)●●●~~~(Lithium-3 would be a nucleus with 3 protons and zero neutrons... and that can't be a nucleus) "Lithium-4 contains three protons and one neutron. This is the shortest-lived known isotope of lithium. It decays by proton emission to helium-3 with half-life of about 10^−23 seconds."~~~●~~~ ~~~●~~~ ~~~●~~~ ~~~●~~~(start with 4)~~~●●●~~~ ~~~●~~~(combine in only way possible to make 3 protons, 1 neutron... notice one proton is on the loose... not attached to nucleus, say goodbye, it's unstable, eject it) Atom Something like an atom with Protons, Neutrons and Electrons has to be the correct model. Things are different weights, different colors, different properties, etc. but everything has to be made out of the same thing. An atom is the way to do it. They almost have the model correct... but everything is actually just strings and tension Electron---∗---An electron is shaped like the metal spines of an umbrella (without the hinges or fabric of course). One string extents from where your hand would hold it up to the center of axis. There, eighteen strings (or radii) extent out in the same curved disc type shape as the umbrella. The last string goes straight up (the same length as all the rest) and connects with the field in space (space is made of the same stuff by the way). Notice the way some elements in vertical columns in the Periodic table chart have an atomic number with difference of 18 between them. Most of the chart is like that (notice how many columns there are). It's because 18 is the determinant number in electron shell configuration. Every electron particle has 20 strings. One string is attached to the proton. One string connects with space (or an electron in the next outer shell). The other 18 strings form the electron disc. When electrons connect with each other they have 18 strings to play with. Check the larger noble gases: Argon 18, Krypton 36, Xenon 54, Radon 86, the amount of electrons in outermost shells will always sum to 18, the first three even have atomic numbers that are multiples of eighteen. Three groups of six radii from one electron can form (along with seven other electrons) the corners of a cube or the "Octet Rule" and seal off the package. Important note: Electrons are actually particles but they (the strings they are made from) form a mesh-like cage around the nucleus. They are also held in place by string connections to the protons. An electron is actually not moving... only the vibrations that are traveling around the strings are moving... and that's what everyone mistakenly thinks an electron is. Electrons (particles) cannot orbit around a nucleus. The protons are stationary and the (multiple) electrons that supposedly are orbiting would require a massive amount of bearings and axles. And they would also interfere with each others orbits. You can't use "force" as the holder (or carrier) because any force is also made from particles or their connection. To make matters worse... an equatorial orbit (supposedly happening) would need something like a circular track around the proton (actually the nucleus as a whole) with a sliding connection. That's ridiculous. Proton~~~●~~~The proton is 20 strings (like everything else) one string radii is attached to a neutron, one is attached to a electron and the other 18 remaining string radii are balled up or collapsed. If the strings collapse in groups of three each that would make 6 groups (3 * 6 = 18) or six types of (what they call) Quarks. And if they collapse in groups of six each that would make 3 groups (6 * 3 = 18) or three (what they call) Quarks in three flavors. Maybe the grouping during collapse happens in different numbers like... 3, 6 and 9 ...that still sums to 18 strings. The jury is still out on all of this Quark business. When they smash up protons they assume they have found different subatomic particles because of the different weights. That is just a different number of strings being smashed apart. If you magnified a proton until it was the size of the dot above the letter "i" then the strings could be compared to something a lot finer than the web of a spider extending out a few hundred meters. Fine enough where eighteen strings can curl into a space the size of the proton and have a spaghetti ball type configuration with a very loose string (or filament) pack. It is the way to make the most universe with the least amount of material. And only one type of material. Neutron●~~~A neutron is the same as proton but with 19 string radii balled up or collapsed. And when it is in the nucleus all 20 are collapsed (although one of the 20 is collapsed in unison with a proton string) One Proton string and one Neutron string balled up or collapsed together is called a Meson. neutron proton electron neutron proton electron on the loose = ●--- ---●--- ---∗--- neutron + proton + electron combined = ●●---∗--- Neutrino●A Neutrino is a completely balled up or collapsed particle●(all 20 strings) or a group of completely balled up particles●●NOT connected to the field or anything else. The speed of light is completely irrelevant to a Neutrino. The speed of light is field stuff, the neutrino is on its own. You could say the Neutrino is in the "ultimate time" zone.