Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Newton's law of gravity passes its biggest test

science.org

Post reply on HN
Print view View original

121–130 of 162 posts

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

#121

Post by davrosthedalek »

glitchc wrote: post #120
davrosthedalek wrote: post #76

Earlier quoted context omitted.

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")

It's one thing to be electromagnetically inert, but if it is matter, it has mass, and if it has mass then it must be possible to collide with it. That we can't suggests it does not exist.

Yes, and dark matter will interact with visible matter gravitationally. When we say "doesn't collide with normal matter", it is not exact. It just means "the interaction length is very very long". Same for neutrinos. Their interaction length is huge as well: 1 TeV Neutrinos have an interaction length of 2.5 million kilometers.

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

#122

Post by kergonath »

fooker wrote: post #30
wongarsu wrote: post #29

Earlier quoted context omitted.

But at least the experimental results disproving these incremental fixes should be exactly the kind of thing the next Einstein should need for coming up with an entirely new way of looking at things

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.

> Some once-in-a-generation scientist has an intuition that turns out to be true and mathematically elegant.

That’s a bit simplistic. There was a lot of research activity around the aether in the late 19th century that was ultimately useful for the foundation of special relativity. Like the Michelson-Morley experiment, which was supposed to measure aether winds, but showed it did not actually seem to exist. Lorentz developed his transform as a theory of the aether, but it became a cornerstone of special relativity. Einstein based his ideas on a lot of things that were done a couple of decades before, some of which were supposed to be part of a theory of the aether.

There was actually quite a lot of activity and vigorous debate between aether and something else, unknown at the time, that turned out to be relativity. Einstein did not just show up and invent everything. There is a very quick overview of this here: https://en.wikipedia.org/wiki/History_of_special_relativity

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

#123

Post by whateverboat »

glitchc wrote: post #119
cactacea wrote: post #84

Earlier quoted context omitted.

Because stuff like the Bullet Cluster exists. Dark matter is in fact the simplest answer. https://en.wikipedia.org/wiki/Bullet_Cluster

I feel compelled to point out that (a)ether was the simplest answer until we confirmed that space is a vacuum and that light can travel in the absence of a medium.

aether was not the simplest explanation since it was disproved by Michelson-Morley experiment. Nothing as of now yet has disproved Dark matter as thoroughly.

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

#124

Post by whateverboat »

hammock wrote: post #99
cactacea wrote: post #84

Earlier quoted context omitted.

Because stuff like the Bullet Cluster exists. Dark matter is in fact the simplest answer. https://en.wikipedia.org/wiki/Bullet_Cluster

Angry gods used to be the simplest answer for a lot of things. Inevitably we find a better model

Simplest in this sense does also imply predictability for Dark matter, which cannot be said for angry gods. Angry gods is anything but a simple theory.

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

#125

Post by bsder »

throwaway27448 wrote: post #73
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.

> 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.

> Occam's razor would point towards some general misunderstanding on which we have no evidence to reasonably speculate a cause.

Dark matter is the Occam's Razor theory. It explains almost all of the observations while assuming the least.

Why do you assume we have no evidence just because we don't have direct observations? Black holes were a similar phenomenon that we had no direct evidence for a fairly long time even though we had lots of other indirect phenomenon that really couldn't be explained any other way.

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

#126

Post by bsder »

glitchc wrote: post #119
cactacea wrote: post #84

Earlier quoted context omitted.

Because stuff like the Bullet Cluster exists. Dark matter is in fact the simplest answer. https://en.wikipedia.org/wiki/Bullet_Cluster

I feel compelled to point out that (a)ether was the simplest answer until we confirmed that space is a vacuum and that light can travel in the absence of a medium.

Abandoning aether was NOT a "simple" answer. One you abandon aether, all manner of weirdness suddenly pops in.

Light being the same speed irrespective of observer is weird. Velocity dilating length and time is weird. Not having a preferential observation point is weird. Not needing a medium for transmission is weird. Not being able to agree on simultaneity is weird. etc.

Aether wasn't just something that a bunch of dullards clung to. You have to abandon some very long held common-sense understanding when you give it up.

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

#127

Post by glitchc »

bsder wrote: post #126
glitchc wrote: post #119

Earlier quoted context omitted.

I feel compelled to point out that (a)ether was the simplest answer until we confirmed that space is a vacuum and that light can travel in the absence of a medium.

Abandoning aether was NOT a "simple" answer. One you abandon aether, all manner of weirdness suddenly pops in. Light being the same speed irrespective of observer is weird. Velocity dilating length and time is weird. Not having a preferential observation point is weird. Not needing a medium for transmission is weird. Not being able to agree on simultaneity is weird. etc. Aether wasn't just something that a bunch of d…

That's my point exactly.

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

#128

Post by towledev »

bsder wrote: post #125
throwaway27448 wrote: post #73

Earlier quoted context omitted.

> 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.

> Occam's razor would point towards some general misunderstanding on which we have no evidence to reasonably speculate a cause. Dark matter is the Occam's Razor theory. It explains almost all of the observations while assuming the least. Why do you assume we have no evidence just because we don't have direct observations? Black holes were a similar phenomenon that we had no direct evidence for a fairly long time even…

The razor is commonly misunderstood.

William of Ockham objected to his fellow theologians inventing things out of whole cloth (like dark matter question mark). That’s the point, not that a simpler explanation is more likely to be true.

The common understanding would have us believe that creationism, being simpler, outshines evolution, or that there is no such thing as a color revolution because the simplest explanation is that the mass protests are earnestly aggrieved locals.

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

#129

Post by fooker »

kergonath wrote: post #122
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.

> Some once-in-a-generation scientist has an intuition that turns out to be true and mathematically elegant. That’s a bit simplistic. There was a lot of research activity around the aether in the late 19th century that was ultimately useful for the foundation of special relativity. Like the Michelson-Morley experiment, which was supposed to measure aether winds, but showed it did not actually seem to exist. Lorentz d…

Did I write invent?

If you revisit what I wrote, you'll find that I agree with you.

There was vigorous debate about a wrong and an unknown thing (both was basically wrong) and it took Einstein's intuition and the new GR math to turn it into science.

I was drawing a parallel between this and the current MOND, string theory, dark matter debate. More specifically, I'd even say dark anything is our generations aether!

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

#130

Post by dnautics »

firebot wrote: post #115
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…

2. It's called relativistic MOND. That exists as a category. RelMOND(for short) includes TeVeS, Einstein–Aether variants, BIMOND, and others. 3. I would wager that what we call the CMB is more of a local effect than a big bang remnant. I lack the karma to downvote, don't blame me. :)

2. not a physicist but iiuc the relativistic MONDs have been disappointing? but not enough to rule out
Post reply on HN