Philosophy Now Forum

Another one tarted up. http://willijbouwman.blogspot.co.uk/201 ... -work.html

uwot wrote:Another one tarted up. http://willijbouwman.blogspot.co.uk/201 ... -work.html

Gravity as diffraction of matter moving through bang-stuff. Hmm.... It would seem to predict the greatest bending of path given the greatest difference between the 'resistance' at the top vs. bottom of the object being deflected by gravity. So the car pitches a lot because there is a huge friction difference between the top (air) and the bottom (tires on road, braking hard), and the airplane has an imperceptible tendency to pitch due to the trivial difference in air density over the thickness of the aircraft.
Hence one would expect the greatest gravitational deflection in areas of greatest gravity differential, not the strongest gravitational field. The differential is tidal-force. Gravity would be strongest near a moderate mass that you can get close to (say a very dense star, where tidal forces would be fatal to a human in freefall), vs. a much stronger field that does not vary so much from one end of you to the other (say near the event horizon of the galactic black hole) where the tidal forces are so weak that one might not even notice one is in mortal danger.

Noax wrote:Gravity as diffraction of matter moving through bang-stuff. Hmm....

Who knows? In my defence, readers were warned about the dangers of philosophy.

Noax wrote:Hence one would expect the greatest gravitational deflection in areas of greatest gravity differential, not the strongest gravitational field.

Inverse square law, Noax.

uwot wrote:

Noax wrote:Hence one would expect the greatest gravitational deflection in areas of greatest gravity differential, not the strongest gravitational field.

Inverse square law, Noax.

Nope. Inverse square law describes the pull on my feet, or the pull on my head, which is much greater near the event horizon of the galactic black hole than it is near the dense star, but tidal forces are the difference between the pull on the head vs. the pull on the feet. That is much greater near (10 km say) the star since there is a far greater percentage change of distance from the mass in question to either my head or feet. The difference in force (tidal force) is enough to rip me apart, and thus would have greater gravitational-diffraction according to your posting.
Around the black hole, the force at either my head or feet is much stronger due to the far greater mass of the super-massive black hole, even despite the 23 million km distance from it, but the difference in distance between my head and feet is negligible at that radius, and your post equates that difference as the magnitude of the curvature of object's path as it goes by. Tidal force does not follow an inverse-square relationship. More like inverse-cubed or more, kind of like the Roche-limit calculations, which only account for tidal forces overcoming the gravity that holds moons together, rather than the EM forces that hold a human together.

Edit: Radius of 23mkm is a vague estimate. Apparently science approximations of the radius of the event horizon vary quite a bit around this figure.

both your quarks are clockwise

-Imp

Noax wrote:Inverse square law describes the pull on my feet, or the pull on my head, which is much greater near the event horizon of the galactic black hole than it is near the dense star, but tidal forces are the difference between the pull on the head vs. the pull on the feet.

Well, yes, but the difference between the pull on the head vs. the pull on the feet is expressed by an inverse square law anywhere in the universe; even black holes, as far as we know.

Noax wrote:Tidal force does not follow an inverse-square relationship.

I think you'll find it does.

Impenitent wrote:both your quarks are clockwise

Actually, it is misleading to imply that 'spin'...

Impenitent wrote:-Imp

Oh, it's you, Impenitent.

Again, I enjoyed the concepts but don't know enough to offer constructive criticism.

Where might dark energy fit into this picture?

Greta wrote:Again, I enjoyed the concepts but don't know enough to offer constructive criticism.

That doesn't stop some people. Years ago, when I was studying physics, I asked what electrons are made of. The lecturer looked aghast: "Made of?" he said, "Well they're made of their mass, charge and spin." "Yeah, but what are they actually made of?" I replied. "Oh, that's philosophy; you don't need to know that." And for the purposes of physics, you don't. Gravity is a case in point; no one knows what causes gravity, but that is no hinderance to Newton's laws being applied successfully.
The point is, you can make up any story you like to explain gravity, as long as it isn't contradicted by the overwhelming evidence that it behaves pretty much as Newton and Einstein predict. As a rule, physicists tend to steer clear of describing what they deal with in anything but mathematical terms except when they are feeling extremely confident. For instance, 6 months after the eclipse which 'proved' general relativity, Einstein gave a lecture at the university of Leiden called 'Ether and Relativity', which he summed up thus: "we may say that according to the general theory of relativity space is endowed with physical qualities; in this sense, therefore, there exists an ether. According to the general theory of relativity space without ether is unthinkable". (You can read the whole thing here: http://www-history.mcs.st-andrews.ac.uk ... ether.html ) The physics community shuffled their feet and got on with the business of formulating quantum mechanics.
As I said, physicists do generally have a working model and all I'm trying to do is express one of those in a way that some people might get. The model I'm trying to depict is based on the 3 pillars of 20th century physics: relativity, quantum mechanics and the standard model, but it is just one view. There are plenty of people who think string theory is a better model. Maybe it is, but someone else can explain how that works.

Greta wrote:Where might dark energy fit into this picture?

Page 10 of 'What is the universe made of?'

uwot wrote:

Greta wrote:Where might dark energy fit into this picture?

Page 10 of 'What is the universe made of?'

That's just the expansion aspect. I was hoping for something like your description of what subatomic particles are, ie. of rippling vortices etc of big bang stuff. It seems that the main quality of space (or spacetime?) is that it always rapidly expands. That energy would seem to be the driver of entropy and time, gradually pulling everything apart.

I still wonder about a multiverse, as there's supposedly much math that supports it and the universe could easily be one small eddy of "multiverse stuff", a megacluster of megaclusters rather than a universe. That still leaves a regression problem. My understanding is that string theory (which predicts a multiverse) has probably suffered a fatal blow in some of the more recent LHC runs, but loop quantum gravity has run into its own problems in panning out from "spacetime stuff" to the stuff in spacetime, which can apparently be solved by taking on aspects of string theory.

As always, feel free to correct any misconceptions.

Greta wrote:That's just the expansion aspect. I was hoping for something like your description of what subatomic particles are, ie. of rippling vortices etc of big bang stuff.

Sorry to disappoint you, but that's it, I'm afraid. Dark energy is just the name given to explain the acceleration of the expansion of the universe, that was noticed in the 90's.

Greta wrote:It seems that the main quality of space (or spacetime?) is that it always rapidly expands.

Space, spacetime, quantum foam, the vacuum of space, the brane; it has many names and subtly different attributes. Bit like god, if you happen to believe in some version of it or them. There has always been this tendency to anthropomorphise, which is why forces of nature all used to be gods. There is also our ability to abstract. The stories people tell about the world is usually some swirling cocktail of anthropomorphism and abstraction, christianity just about nailed it with the trinity. What can god do? Everything that all the other gods in a bucket can do. How does it do it? Well, it's also this abstract force, the holy ghost. Yeah, but who's gonna worship that? Ah, well; then there's this bloke called Jesus.
Some of the physicists I know have some very weird ideas, but usually the only thing that can extract them is alcohol. For some of them, things like sub-atomic particles, forces, dark energy and whatnot, have 'personalities'. Mad as a box of frogs, but it doesn't stop them being first rate physicists. I even know at least one mathematician who claims to 'love' numbers. Isn't beer amazing?

Greta wrote:That energy would seem to be the driver of entropy and time, gradually pulling everything apart.

Yeah, entropy and time are other things that otherwise sane scientists attach unlikely properties to. One way of looking at entropy and time is as pretty much the same thing. I don't know if you've ever seen a tightly wound spring suddenly being released. It goes bonkers for a bit, lots of crazy loops and eddies, bit like quarks, until all the energy is used and it goes flat, a bit like heat death.

Greta wrote:I still wonder about a multiverse, as there's supposedly much math that supports it and the universe could easily be one small eddy of "multiverse stuff", a megacluster of megaclusters rather than a universe.

Who knows? This is one of my favourite quotes, it's from Michael Faraday: "All this is a dream. Still examine it by a few experiments. Nothing is too wonderful to be true, if it be consistent with the laws of nature; and in such things as these, experiment is the best test of such consistency."

Greta wrote:That still leaves a regression problem.

We will never know what's beyond the horizon.

Greta wrote:My understanding is that string theory (which predicts a multiverse) has probably suffered a fatal blow in some of the more recent LHC runs, but loop quantum gravity has run into its own problems in panning out from "spacetime stuff" to the stuff in spacetime, which can apparently be solved by taking on aspects of string theory.

Well, it doesn't have to be true to be useful. String theory might still come up with something.

uwot wrote:

Greta wrote:That's just the expansion aspect. I was hoping for something like your description of what subatomic particles are, ie. of rippling vortices etc of big bang stuff.

Sorry to disappoint you, but that's it, I'm afraid. Dark energy is just the name given to explain the acceleration of the expansion of the universe, that was noticed in the 90's.

I thought that quarks were just little hyper-intense bits of energy too, so I was hoping for an equivalent eye opener with dark energy.

uwot wrote:

Greta wrote:That energy would seem to be the driver of entropy and time, gradually pulling everything apart.

Yeah, entropy and time are other things that otherwise sane scientists attach unlikely properties to. One way of looking at entropy and time is as pretty much the same thing. I don't know if you've ever seen a tightly wound spring suddenly being released. It goes bonkers for a bit, lots of crazy loops and eddies, bit like quarks, until all the energy is used and it goes flat, a bit like heat death.

I'm already well aware of the entropy = time = change situation. The spring example would posit dark energy as cosmic kinetic energy, which doesn't work at all if dark energy, as the math suggests, preceded (and perhaps triggered) the big bang.

uwot wrote:

Greta wrote:My understanding is that string theory (which predicts a multiverse) has probably suffered a fatal blow in some of the more recent LHC runs, but loop quantum gravity has run into its own problems in panning out from "spacetime stuff" to the stuff in spacetime, which can apparently be solved by taking on aspects of string theory.

Well, it doesn't have to be true to be useful. String theory might still come up with something.

String theory is already being useful https://www.theatlantic.com/science/arc ... ry/500390/

uwot wrote:Another one tarted up. http://willijbouwman.blogspot.co.uk/201 ... -work.html

Don't brake for the stupid cat, that way it won't walk in front of you again, and that much stupidity will be removed from the gene pool.

uwot wrote:

Noax wrote:Tidal force does not follow an inverse-square relationship.

I think you'll find it does.

I played with it since I could not find a quote. Turns out tidal force follows an inverse-cubed law. All calculations are in MKS units, and I worked from a rounded value of 6.7e-11 for the gravitational constant.

For just plain gravitational force, I place a 1kg object in freefall in three places (Earth, Neutron star, and Sgr-A), and a 2nd 1kg object 2 meters further away. The difference in force between the closer and the farther object is the tidal force over the typical height of a human. If we tied the two objects together with string, the tidal force would be the tension on that string as the assembly orbits the object in question.

On Earth, we have mass of 6e24 kg, distance 6.4e6 meters, resulting in about 9.8 newtons of force from Earth's gravity.
Tidal force required a few more significant digits, but I got 9.814453n-9.814446n = 7 micro-newtons. The 2nd figure 9.814446 was from an altitude of 6400002 meters.

Neutron star, orbiting at a distance of 1000km: mass 4e30 kg is about 260 million newtons from gravity.
Tidal force over the 2-meter difference was 268000000-267998928 = 1072 newtons. Considering a human's mass-moment is about 40-50 times that, 40000 newtons would indeed rip you apart unless you took great care to flatten yourself horizontally in relation to the star you're orbiting, thus minimizing said mass-moment.

I also figured it out for 100km orbit and the tidal force was 1.071 million newtons. Hence n-cubed.

Then I put our two objects a million km from Sgr A (mass 8e36 kg). Out there you get 536 million newtons from gravity, a bit more than twice that from a 1000km from the Neutron star, but tidal force was 536000000-535999997 = 3 newtons, which admittedly is enough to be noticed, but hardly dangerous. Twice the gravity there, but less than 1% of the gradient compared to the Neutron-star case, and your explanation of gravity seems dependent on diffraction due to that gradient.

Greta wrote:I'm already well aware of the entropy = time = change situation. The spring example would posit dark energy as cosmic kinetic energy, which doesn't work at all if dark energy, as the math suggests, preceded (and perhaps triggered) the big bang...String theory is already being useful.

String theory is great for talking about things which may exist, but are too small to see, or possible situations that might be the case, but are too far away to see. Maths is a huge field and there's only a tiny corner of it that we know applies to what we can see. As the article says: “They have all these hammers and they go looking for nails.” That’s fine, he (Sean Carroll) said, even acknowledging that generations might be needed to develop a new theory of quantum gravity. “But it isn’t fine if you forget that, ultimately, your goal is describing the real world.”
String theory has occupied some of the most brilliant mathematicians of the last couple of generations. If none of it looked anything like the visible universe, I doubt that physicists would have taken much. But while, as the article points out, string theory can be useful for tackling some problems, it hasn't, to my knowledge, made any predications that are unique to it, and have been confirmed by experiment.
It may well be that every mathematical permutation is real somewhere in a multiverse, but the bit I'm trying to describe is the bit we can see. Inevitably some of the simplifications and analogies will irritate some, and all the bits that are left out will annoy others, but there's a limit to what you can describe with stick men and women.