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No, negative masses have not revolutionized cosmology

backreaction.blogspot.com

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Re: No, negative masses have not revolutionized cosmology

#71

Post by chongli »

sgt101 wrote: post #58
khawkins wrote: post #12

Occam's razor is a heuristic used in the investigative process, not a principle. While it's fair to point out that a theory makes everything more complicated and thus might make it less likely to be sound, it's not fair to push back on the first bit of research into a theory because they haven't had the time to fully develop it. Indeed, a scientific revolution generally starts by treating as false an assumption previ…

History : Dun Scotus (really) probably invented Ockham's razor - William was his student and used it to avoid the thing that all medieval philosophers needed to avoid, namely being tied up and put on a bonfire. Why did Dun invent it (probably)… well here's the thing, Christianity has a God with three faces, son, father and holy ghost thing. Why? The answer is - don't multiply entities beyond necessity, so God has the…

You ought to read a little bit into the history of astronomy, particularly planetary motion. If the ancient Greeks had applied Occam's razor then we would've abandoned geocentrism long before Copernicus.

We should've listened to (and built on) Aristarchus of Samos instead of Ptolemy's deferent/epicycle contraption. All of this because everyone wanted to hang on to Plato's assertion that the heavens obeyed the mathematical beauty of circular forms.

Re: No, negative masses have not revolutionized cosmology

#72

Post by diffeomorphism »

> These equations tell you that like masses attract and unlike masses repel. We don’t normally talk about this because for all we know there are no negative gravitational masses, but you can see what happens in the Newtonian limit.

I feel like I am misunderstanding what the author wants to say here. It seems to me that this would only be the case if you change the sign of the gravitational mass (F[-m_1,-m_2]=F[m_1,m_2]), but not of the inertial mass?

In the Newtonian case you get that the force is proportional to m_1m_2, so ++=+, +-=- and --=+, but then F=ma flips the direction of the acceleration, right?

++ gives F>0 and a>0, so attraction.

-- gives F>0, but negative inertial mass yield a+*- gives F0 and is attracted.

What am I missing here?

Re: No, negative masses have not revolutionized cosmology

#73

Post by AlexCoventry »

sgt101 wrote: post #58
khawkins wrote: post #12

Occam's razor is a heuristic used in the investigative process, not a principle. While it's fair to point out that a theory makes everything more complicated and thus might make it less likely to be sound, it's not fair to push back on the first bit of research into a theory because they haven't had the time to fully develop it. Indeed, a scientific revolution generally starts by treating as false an assumption previ…

History : Dun Scotus (really) probably invented Ockham's razor - William was his student and used it to avoid the thing that all medieval philosophers needed to avoid, namely being tied up and put on a bonfire. Why did Dun invent it (probably)… well here's the thing, Christianity has a God with three faces, son, father and holy ghost thing. Why? The answer is - don't multiply entities beyond necessity, so God has the…

Occam's razor has a practical interpretation in Bayesian statistics, in that a more complex hypothesis will tend to have exponentially lower prior probability, because in comes from a more heavily parametrized component of the hypothesis space.

That doesn't mean much without a concrete probability model, though, and there probably isn't one in this case.

Re: No, negative masses have not revolutionized cosmology

#74

Post by rudolfwinestock »

sgt101 wrote: post #58
khawkins wrote: post #12

Occam's razor is a heuristic used in the investigative process, not a principle. While it's fair to point out that a theory makes everything more complicated and thus might make it less likely to be sound, it's not fair to push back on the first bit of research into a theory because they haven't had the time to fully develop it. Indeed, a scientific revolution generally starts by treating as false an assumption previ…

History : Dun Scotus (really) probably invented Ockham's razor - William was his student and used it to avoid the thing that all medieval philosophers needed to avoid, namely being tied up and put on a bonfire. Why did Dun invent it (probably)… well here's the thing, Christianity has a God with three faces, son, father and holy ghost thing. Why? The answer is - don't multiply entities beyond necessity, so God has the…

Although it's attributed to him, William of Ockham did not come up with Occam's Razor.

My metaphysics teacher showed me a line in the Summa Contra Gentiles where St. Thomas Aquinas enunciated the same idea behind the Razor almost a hundred years before Ockham did. Sorry, I don't have the reference handy. Furthermore, the Wikipedia article on Ockham's Razor traces the basic idea all the way back to Aristotle's Posterior Analytics.

Re: No, negative masses have not revolutionized cosmology

#75

Post by gnulinux »

simonh wrote: post #43
mbell wrote: post #14

I'm not a physicist, just an interested bystander but some of these arguments don't seem to hold water to me: > There’s a more general point to be made here. The primary reason that we use dark matter and dark energy to explain cosmological observations is that they are simple. > A creation term is basically a magic fix by which you can explain everything and anything. Dark matter is an unknown 'substance' that inter…

I don’t know about dark matter, but the case for dark energy or something like it is pretty compelling. The expansion of the universe is accelerating. Things don’t generally accelerate unless there is something pushing them. So what is it that’s pushing everything in the universe apart? Maybe it isn’t a ‘thing’ doing it, who knows, but there must be a reason.

As an extension of this argument. What caused the initial acceleration of the Big Bang? Isn't it possible the current acceleration of the universe is an extension of this force?

Re: No, negative masses have not revolutionized cosmology

#76

Post by [deleted] »

mcguire wrote: post #69
mbell wrote: post #23

Earlier quoted context omitted.

Maybe? We don't know, also Einstein wasn't a fan: > Einstein originally introduced the concept in 1917 [2] to counterbalance the effects of gravity and achieve a static universe, a notion which was the accepted view at the time. Einstein abandoned the concept in 1931 after Hubble's discovery of the expanding universe. > Einstein reportedly referred to his failure to accept the validation of his equations—when they ha…

It turns out that, when he thought he was wrong, he was mistaken.

[deleted]

Re: No, negative masses have not revolutionized cosmology

#77

Post by pfdietz »

duality wrote: post #11

"[T]he gravitational interaction is exchanged by a spin-2 field, whereas the electromagnetic force is exchanged by a spin-1 field. Note that for this to be the case, you do not need to speak about the messenger particle that is associated with the force if you quantize it (gravitons or photons). It’s simply a statement about the type of interaction, not about the quantization. Again, you don’t get to choose this beha…

If negative mass experiences an attractive force (that is, one that adds momentum toward the source of the force), doesn't that push it away? After all, with negative mass, the momentum vector and the velocity vector point in opposite directions.

Re: No, negative masses have not revolutionized cosmology

#78

Post by 8bitsrule »

"highly problematic to introduce negative inertial masses .... This fits badly with our observations."

Science news is not scarce. Click-bait titles aren't either. There's no shortage of catchy on-paper theories that 1)are not backed by evidence, 2) make no predictions.

Cosmology has a big problem, and thrashing around in desperation is not becoming.

Re: No, negative masses have not revolutionized cosmology

#79

Post by Izkata »

guitarbill wrote: post #60
rwilson4 wrote: post #41

Earlier quoted context omitted.

I believe the author's argument is: however simple or complicated dark matter and energy are, negative (inertial) mass just makes things even more complicated, without offering any new (testable) insights. The author herself points out that she (and the GR community) may be wrong about a lot of this stuff (e.g. that gravity is mediated by a spin-2 field), but absent a testable hypothesis, negative masses don't actual…

> "it’s highly problematic to introduce negative inertial masses because this means the vacuum becomes unstable. If you do this, you can produce particle pairs from a net energy of zero in infinitely large amounts. This fits badly with our observations." Basically, if you mess the the equation, you have to be very sure you aren't simulating something silly. Which is easy to do, unfortunately I've done it often. I sti…

Waaait a minute, isn't that describing something we've already observed - spontaneous creation of virtual particle pairs in a vacuum?

Re: No, negative masses have not revolutionized cosmology

#80

Post by kjeetgill »

rwilson4 wrote: post #41
mbell wrote: post #14

I'm not a physicist, just an interested bystander but some of these arguments don't seem to hold water to me: > There’s a more general point to be made here. The primary reason that we use dark matter and dark energy to explain cosmological observations is that they are simple. > A creation term is basically a magic fix by which you can explain everything and anything. Dark matter is an unknown 'substance' that inter…

I believe the author's argument is: however simple or complicated dark matter and energy are, negative (inertial) mass just makes things even more complicated, without offering any new (testable) insights. The author herself points out that she (and the GR community) may be wrong about a lot of this stuff (e.g. that gravity is mediated by a spin-2 field), but absent a testable hypothesis, negative masses don't actual…

That's the thing, I think it's exciting because that researcher does believe it to be testable. My comment from the last negative mass thread:

My favorite bit from the author on Twitter: https://threadreaderapp.com/thread/1070302359325151233.html > The next-generation radio telescope - the Square Kilometre Array @SKA_telescope will be able to test this theory, and directly confirm or invalidate its predictions. 13/17 It is rather surprising that the model predicts the properties of a LambdaCDM universe.

As a casual observer this is is what gets me excited! We'll get our answers one way or another

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