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Newton's law of gravity passes its biggest test

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Re: Newton's law of gravity passes its biggest test

#71

Post by hansvm »

cowl wrote: post #28
gus_massa wrote: post #26

Earlier quoted context omitted.

We make a similar guess for the stuff that is in the center of Earth. We measure local gravity and speed of sound velocity, and we guess here is liquid, here is solid, here is this rock, here is this another rock [1]. See for example https://www.livescience.com/64943-nobody-understands-the-gia... nobody has seen them, we guess they are there. Dark matter is another guess. We guess there is more matter in galaxies tha…

Dark matter is not another Guess. is no guess at all. its the same as saying the center of the earth is made of Dark Core. and when someone proposed liquid core, there would be papers how a liquid core doesnt explain 100 %, and neither does rock or solid so Dark Core it is because it's sIMpLer to have just one Dark Something than 3 different somethings to explain anything. The fact that there are tentatives to identi…

The "it looks like there's stuff we didn't previously know about here" class of guesses has historically been fruitful, yielding, among other things, the discovery of several planets. Maybe dark matter isn't the answer, but it's not "no guess at all."

Re: Newton's law of gravity passes its biggest test

#72

Post by lukan »

dnautics wrote: post #60
pessimist wrote: post #53

Earlier quoted context omitted.

There are multiple independent observations pointing toward dark matter: 1. Galaxy rotation curves. 2. Galaxy cluster mass measurements from gravitational lenses and infrared. 3. Cosmic Microwave Background models (mass measurements from inhomogeneities that correspond to acoustic waves, for eg). MOND only explains 1. Dark matter accounts for all 3. Only catch is that it hasnt been directly observed.

MOND explains 1. 2 is "who can say" because nobody has reconciled MOND with Relativity (not that it's impossible, it's just hard and annoying math, could be a lack of effort thing, could also be a real theoretical constraint that invalidates MOND). 3 is subject to questions like "is the CMB really what we think it is" -- if it's early thermalized dust, then that ALSO resolves hubble tension, e.g. MOND explains severa…

"HM. people have been downvoting. Anyone care to post a substantive rebuttal?"

Just that asking this might get you more downvotes. I upvoted as I found your input interesting. I would suggest to edit that out (then I will delete my comment)

Re: Newton's law of gravity passes its biggest test

#73

Post by throwaway27448 »

pessimist wrote: post #53
rappatic wrote: post #41

When I see dark matter in the news I'm always reminded of the story of Vulcan. In the 1800s, detailed observations of the planet Mercury showed that its orbit was slightly different than Newtonian mechanics predicted-- a difference of about 43 arcseconds per century. The study was rigorous enough to rule out any observation errors. Le Verrier, the astronomer who made these observations, wondered how to explain the di…

There are multiple independent observations pointing toward dark matter: 1. Galaxy rotation curves. 2. Galaxy cluster mass measurements from gravitational lenses and infrared. 3. Cosmic Microwave Background models (mass measurements from inhomogeneities that correspond to acoustic waves, for eg). MOND only explains 1. Dark matter accounts for all 3. Only catch is that it hasnt been directly observed.

> Only catch is that it hasnt been directly observed.

Ok, so... why do people take it seriously as a concept? Occam's razor would point towards some general misunderstanding on which we have no evidence to reasonably speculate a cause.

Re: Newton's law of gravity passes its biggest test

#74

Post by dnautics »

lukan wrote: post #72
dnautics wrote: post #60

Earlier quoted context omitted.

MOND explains 1. 2 is "who can say" because nobody has reconciled MOND with Relativity (not that it's impossible, it's just hard and annoying math, could be a lack of effort thing, could also be a real theoretical constraint that invalidates MOND). 3 is subject to questions like "is the CMB really what we think it is" -- if it's early thermalized dust, then that ALSO resolves hubble tension, e.g. MOND explains severa…

"HM. people have been downvoting. Anyone care to post a substantive rebuttal?" Just that asking this might get you more downvotes. I upvoted as I found your input interesting. I would suggest to edit that out (then I will delete my comment)

I don't really care (i'm doing just fine fake-internet-points-wise), just if I made a mistake it would be nice to know. Otherwise worth it to know that there are people out there who find "alternative explanations by professional scientists" threatening. for some reason.

Re: Newton's law of gravity passes its biggest test

#76

Post by davrosthedalek »

htx80nerd wrote: post #37
GuB-42 wrote: post #2

If you follow Sabine Hossenfelder's channel, she has a MONDOmeter. With MOND (modified Newtonian gravity) on one side and dark matter on the other side. As new papers come out the needle goes back and forth, and I guess that she will make a new video if she hasn't already, with the needle moving one step towards dark matter. I find it interesting how it doesn't seem to settle. Dark matter is still the favorite, but t…

Dark Matter : supposedly makes up a big amount of the mass of the universe, but cant be seen, does not emit, absorb, or reflect light. Also it can 'pass through' other normal matter, and other dark matter. It's basically magic aka not actually real, just something in vogue to pretend is real at the present moment.

The "pass through matter" is a consequence of not interacting electromagnetically. That's not that uncommon. Think neutrinos. (Also, "not" might just mean "very much reduced")

Re: Newton's law of gravity passes its biggest test

#77

Post by davrosthedalek »

dnautics wrote: post #63
pixl97 wrote: post #57

Earlier quoted context omitted.

I mean it's easy to say it's fake, but to counter this, why can a particle that only interacts with gravity not exist? The neutrino is a good example of a particle that almost doesn't exist. They are produced in solar reactions in spectacular amounts. Trillions of them are flitting through you right now as if you don't exist. You'd need a light year block of lead to ensure you could stop one. Mind-boggling amounts of…

I mean sure nature has no obligation to not have a unfalsifable particle, but you wind up in weird places, like, there exists a distribution of dark matter that explains the poltergeist that knocked over your coffee cup last week.

If there would be a distribution of dark matter that explains the poltergeist, we could measure that distribution of dark matter.

We can measure the mass distribution on astronomical scales. We "see" the dark matter. Just not with light.

Re: Newton's law of gravity passes its biggest test

#78

Post by lukan »

dnautics wrote: post #74
lukan wrote: post #72

Earlier quoted context omitted.

"HM. people have been downvoting. Anyone care to post a substantive rebuttal?" Just that asking this might get you more downvotes. I upvoted as I found your input interesting. I would suggest to edit that out (then I will delete my comment)

I don't really care (i'm doing just fine fake-internet-points-wise), just if I made a mistake it would be nice to know. Otherwise worth it to know that there are people out there who find "alternative explanations by professional scientists" threatening. for some reason.

Well, I rather meant there are guidelines to keep this space meta debate free and I do think they make sense.

(And apart from that, HN is not free of dogmatic ideologists of all sorts who feel triggered by anything straying off from mainstream theory. That is my guess here and my advice to ignore it, but I would be also curious if there is something clearly wrong with your comment deserving downvotes.)

Re: Newton's law of gravity passes its biggest test

#79

Post by fooker »

messe wrote: post #45
fooker wrote: post #30

Earlier quoted context omitted.

Interestingly, more often than not it happens the other way. Some once-in-a-generation scientist has an intuition that turns out to be true and mathematically elegant. It gets proven experimentally years or decades later. Relativity was exactly like this.

It was far from exactly like that. GR was in part prompted by the precession of the perihelion of mercury for which there was plenty of data.

Look at the timeline here https://en.wikipedia.org/wiki/Tests_of_general_relativity

Re: Newton's law of gravity passes its biggest test

#80

Post by fooker »

anthonypasq wrote: post #31
fooker wrote: post #19

Earlier quoted context omitted.

We are likely going to find out that both are unfixably faulty. It'll take either the next Einstein or some groundbreaking experimental observation to get there in my opinion. If it was possible to incrementally fix these theories, the army of postdocs working on these would have already done so in the last decade or so.

you think the deepest mysteries of reality and the universe should just reveal themselves because we have a couple thousand smart people working on it for... 10 years?

If you could get there with minor modifications of the current state of the art, yes.

My point is that you likely can not.

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