Breakthrough Announced in Dark Matter Detection Technology • Hacker News Board

Re: Breakthrough Announced in Dark Matter Detection Technology

#41

Post by dbasedweeb » Wed, Apr 11, 2018, 1:40 AM UTC

truantbuick wrote: post #20

davidcuddeback wrote: post #16

Earlier quoted context omitted.

Modified gravity theories don't fit all the evidence, such as the distribution of mass in the Bullet Cluster [1] or the large-scale structure of the CMB [2]. [1] https://en.wikipedia.org/wiki/Bullet_Cluster [2] https://en.wikipedia.org/wiki/Dark_matter#Cosmic_microwave_b...

Some would disagree: http://backreaction.blogspot.com/2018/04/no-that-galaxy-with... As a non-scientist, it seems like dark matter has been relentlessly adjusted and overfitted and still appears very inadequate to fit all the evidence.

Theories are tested and observations are made. If we’re lucky a positive result emerges, but more often what you get are results which just put constraints on the theory. For example MACHO theory was once seen as very plausible, but observations of gravitational lensing have placed strict limits on it so that it seems increasingly unlikely. Sometimes the process of constraining theory leads to a reformulation of the theory, sometimes to its abandonment. Other theories which more agreeably fit the constraints may come forward (i.e. WIMP theory on the case of DM), and they may in turn be abandoned or reformulated.

That’s science working as intended, or as people here like to say, a feature and not a bug. The more a theory has to make assumptions or introduce things like new particles and fields to make predictions, the less popular it tends to be. Of course once you constrain the solution space to the point where the simplest theories can’t hold, you have to consider the more complex ones. The important thing to remember is that none of this happens in a vacuum, and while personal preferences play a role, they do so only insofar as the constraints placed on theory by observation allow for it.

Incidentally that’s also why falsifiablility is such a big deal, because in its absence you can assert or believe any old thing.

Re: Breakthrough Announced in Dark Matter Detection Technology

#42

Post by lulmerchant » Wed, Apr 11, 2018, 1:52 AM UTC

dbasedweeb wrote: post #40

lulmerchant wrote: post #39

Earlier quoted context omitted.

>relentlessly adjusted and overfitted and still appears very inadequate to fit all the evidence Welcome to physics. The Copenhagen Interpretation is the most concise and robustly tested theory in all of physics. Yet it was dreamt up by a literal absurdist who thought that the universe itself has no objective state of existence. For all we know about the universe, we can still not answer many of the most basic questio…

Incomplete in very extreme conditions such as the interiors of black holes or the first instants after the Big Bang. I’m not really sure that’s “woeful” in a sense that matters to almost anyone other than a particle physicist or a cosmologist. For example the confidence in QED has been tested and found that the theory makes accurate predictions to within 10^-8. I’d also argue that you’re substituting “basic” for “fun…

An argument between ‘basic’ and ‘fundamental’ is a semantic one, and bordering on pointless.

QED works quite well in most cases, but only if you don’t look too closely, and only if you ignore one of the fundamental forces. QED offers no explaination for gravity, which even non-physicists know exists.

What is gravity? What is a particle? What is space? These are all quite basic questions that were not even close to having complete answers for. QED provides a “good enough” explaination for how particles and space work, just as relativity gives a “good enough” explaination of gravity. But any physicist who’s being intellectually honest knows that we only have a rudimentary understanding of these concepts. The wave function is just an excellent tool we use to smooth out our lack of understanding. Your comment is a perfect example of the arrogance that pervades the scientific community, and the inability to acknowledge the limits of our own understanding. Which I think only inhibits the wider community’s ability to communicate effectively with the general public.

Re: Breakthrough Announced in Dark Matter Detection Technology

#43

Post by dbasedweeb » Wed, Apr 11, 2018, 1:54 AM UTC

lulmerchant wrote: post #42

dbasedweeb wrote: post #40

Earlier quoted context omitted.

Incomplete in very extreme conditions such as the interiors of black holes or the first instants after the Big Bang. I’m not really sure that’s “woeful” in a sense that matters to almost anyone other than a particle physicist or a cosmologist. For example the confidence in QED has been tested and found that the theory makes accurate predictions to within 10^-8. I’d also argue that you’re substituting “basic” for “fun…

An argument between ‘basic’ and ‘fundamental’ is a semantic one, and bordering on pointless. QED works quite well in most cases, but only if you don’t look too closely, and only if you ignore one of the fundamental forces. QED offers no explaination for gravity, which even non-physicists know exists. What is gravity? What is a particle? What is space? These are all quite basic questions that were not even close to ha…

Basic = simple

Fundamental = bedrock

QED works to the best ability of any test, down to one part in ten billion, so looking very close indeed. Then in order...

What is gravity? The geometry of spacetime.

What is a particle? A localized excitation of a field.

It may be that you don’t like or understand the answers, but they exist and allow people to make precise predictions, build machines that work based on said principles. Maybe you’re confusing scientific answers with philosophical ones?

Re: Breakthrough Announced in Dark Matter Detection Technology

#44

Post by lulmerchant » Wed, Apr 11, 2018, 2:30 AM UTC

dbasedweeb wrote: post #43

lulmerchant wrote: post #42

Earlier quoted context omitted.

An argument between ‘basic’ and ‘fundamental’ is a semantic one, and bordering on pointless. QED works quite well in most cases, but only if you don’t look too closely, and only if you ignore one of the fundamental forces. QED offers no explaination for gravity, which even non-physicists know exists. What is gravity? What is a particle? What is space? These are all quite basic questions that were not even close to ha…

Basic = simple Fundamental = bedrock QED works to the best ability of any test, down to one part in ten billion, so looking very close indeed. Then in order... What is gravity? The geometry of spacetime. What is a particle? A localized excitation of a field. It may be that you don’t like or understand the answers, but they exist and allow people to make precise predictions, build machines that work based on said prin…

Basic

Adjective

1. forming an essential foundation or starting point; fundamental.

Your answers to those questions are either deliberately over-simplifying to avoid the question, or you don’t understand QED yourself. Your definition of a particle describes a possible outcome of a measurement, and ignores the existence of a wave function. Your description of gravity cannot be created in QED. You have provided no explanation of space whatsoever, which is so woefully unexplained by quantum mechanics, that it is referred to as the ‘vacuum catastrophe’.

Anybody who investigates these concepts can see that our understanding of them is woefully incomplete. However scientists tend to have a very hard time acknowledging these limits of our understanding, and will often respond to such acknowledgements with thinly veiled contempt. Just as you have done by trying to undermine my opinion on them, rather than responding to what I have said. I think that by failing to acknowledge the limits of scientific understanding, maybe you are confusing science with religion?

Re: Breakthrough Announced in Dark Matter Detection Technology

#45

Post by davidcuddeback » Wed, Apr 11, 2018, 3:00 AM UTC

lulmerchant wrote: post #44

dbasedweeb wrote: post #43

Earlier quoted context omitted.

Basic = simple Fundamental = bedrock QED works to the best ability of any test, down to one part in ten billion, so looking very close indeed. Then in order... What is gravity? The geometry of spacetime. What is a particle? A localized excitation of a field. It may be that you don’t like or understand the answers, but they exist and allow people to make precise predictions, build machines that work based on said prin…

Basic Adjective 1. forming an essential foundation or starting point; fundamental. Your answers to those questions are either deliberately over-simplifying to avoid the question, or you don’t understand QED yourself. Your definition of a particle describes a possible outcome of a measurement, and ignores the existence of a wave function. Your description of gravity cannot be created in QED. You have provided no expla…

> scientists tend to have a very hard time acknowledging these limits of our understanding

That couldn't be further from the truth. Scientists have been very upfront about the limits of our understanding, particularly when it comes to combining gravity with quantum physics. Listen to Neil DeGrasse Tyson or any other science communicator talk about general relativity or quantum physics and you'll hear them drive this point home.

We know that quantum physics and general relativity don't combine well, yet both are among the most thoroughly tested theories in science. We know we need new physics to combine them, but they're still useful in their own domains. Just like before we had general relativity, we knew that Newtonian gravity was incomplete because it didn't correctly explain the orbit of Mercury. But Newtonian gravity was (and is) still useful, even with those limitations. The key is knowing where the limitations apply.

General relativity applies to scenarios of high mass/energy. Quantum physics applies at small scales. They both work great in their respective domains. It's when you have high mass/energy in a small volume that things break down, because both quantum physics and general relativity apply, but we don't know how to combine them.

> I think that by failing to acknowledge the limits of scientific understanding, maybe you are confusing science with religion?

I don't see dbasedweeb failing to acknowledge anything. dbasedweeb wrote, "incomplete in very extreme conditions such as the interiors of black holes or the first instants after the Big Bang," which happen to be two places where quantum physics and general relativity are both applicable and we therefor run into the limitations that I mentioned above.

Re: Breakthrough Announced in Dark Matter Detection Technology

#46

Post by raattgift » Wed, Apr 11, 2018, 3:37 AM UTC

lulmerchant wrote: post #42

dbasedweeb wrote: post #40

Earlier quoted context omitted.

Incomplete in very extreme conditions such as the interiors of black holes or the first instants after the Big Bang. I’m not really sure that’s “woeful” in a sense that matters to almost anyone other than a particle physicist or a cosmologist. For example the confidence in QED has been tested and found that the theory makes accurate predictions to within 10^-8. I’d also argue that you’re substituting “basic” for “fun…

An argument between ‘basic’ and ‘fundamental’ is a semantic one, and bordering on pointless. QED works quite well in most cases, but only if you don’t look too closely, and only if you ignore one of the fundamental forces. QED offers no explaination for gravity, which even non-physicists know exists. What is gravity? What is a particle? What is space? These are all quite basic questions that were not even close to ha…

> QED offers no explanation for gravity

It does; gravitation in perturbative QED on time-dependent curved backgrounds has exactly the same explanation as General Relativity. [1] This generalizes very well. [2]

One can look at it the other direction too: General Relativity guarantees flat spacetime in the neighbourhood of every point on the manifold with signature 1,3 or 3,1. As long as the radius of curvature is large compared to the system under study there is no trouble at all (QED systems are usually pretty tiny, so you're good down to and through astrophysical black hole apparent horizons). This is implicit in laboratory tests of QED.

> But any physicist who’s being intellectually honest knows that we only have a rudimentary understanding of these concepts

Everyone should be honest about how much she or he really knows, and how much he or she can judge how much someone else really knows.

"The first principle is that you must not fool yourself — and you are the easiest person to fool" -- Feynman

- --

[1] [BirrellDavies] N.D. Birrell and P.C.W. Davies, Quantum fields in curved space, Cambridge University Press, Cambridge U.K. (1982).

[2] [BGZV] A.O. Barvinsky, Yu.V. Gusev, V.V. Zhytnikov, and G.A. Vilkovisky, SPIRES-HEP:Print-93-0274(Manitoba), (1993). https://arxiv.org/abs/0911.1168

Re: Breakthrough Announced in Dark Matter Detection Technology

#47

Post by lulmerchant » Wed, Apr 11, 2018, 3:51 AM UTC

davidcuddeback wrote: post #45

lulmerchant wrote: post #44

Earlier quoted context omitted.

Basic Adjective 1. forming an essential foundation or starting point; fundamental. Your answers to those questions are either deliberately over-simplifying to avoid the question, or you don’t understand QED yourself. Your definition of a particle describes a possible outcome of a measurement, and ignores the existence of a wave function. Your description of gravity cannot be created in QED. You have provided no expla…

> scientists tend to have a very hard time acknowledging these limits of our understanding That couldn't be further from the truth. Scientists have been very upfront about the limits of our understanding, particularly when it comes to combining gravity with quantum physics. Listen to Neil DeGrasse Tyson or any other science communicator talk about general relativity or quantum physics and you'll hear them drive this…

The theories are incompatible at all energy levels, it's simply that those are two examples where we can't use them to accurately predict outcomes. Another not-extreme-at-all example where quantum physics completely breaks down is empty space. However, this discussion is deliberately missing the point, which is that it's not making predictions in everyday scenarios where physics fails. It's in describing the basic nature of our universe, which are two completely different things all together.

You're right that there are examples of scientists who highlight these gaps in our knowledge, there are more who simply pay some lip service to them, and then there's a much larger group of people, like dbasedweeb, who irrationally suppress all criticisms of scientific theories as if they were literally religious beliefs.

Re: Breakthrough Announced in Dark Matter Detection Technology

#48

Post by [deleted] » Wed, Apr 11, 2018, 5:28 AM UTC

lulmerchant wrote: post #39

truantbuick wrote: post #20

Earlier quoted context omitted.

Some would disagree: http://backreaction.blogspot.com/2018/04/no-that-galaxy-with... As a non-scientist, it seems like dark matter has been relentlessly adjusted and overfitted and still appears very inadequate to fit all the evidence.

>relentlessly adjusted and overfitted and still appears very inadequate to fit all the evidence Welcome to physics. The Copenhagen Interpretation is the most concise and robustly tested theory in all of physics. Yet it was dreamt up by a literal absurdist who thought that the universe itself has no objective state of existence. For all we know about the universe, we can still not answer many of the most basic questio…

[deleted]

Re: Breakthrough Announced in Dark Matter Detection Technology

#49

Post by russdill » Wed, Apr 11, 2018, 6:23 AM UTC

andrewflnr wrote: post #32

piptastic wrote: post #25

Earlier quoted context omitted.

I'm curious, why would you root for anything in particular?

Why do people root for anything? Emotions, aesthetics, etc. You can't always stop yourself from having that reaction, so you may as well let it out. Myself, I'm rooting for the spacetime-from-entanglement family of quantum gravity theories, because they're frickin cool.

I'm rooting for the various dark matter particle candidates. It really seems completely unsurprising that there would be particles that react very little if at all to the EM field. It's true of other field and particle combinations. In short, I root for it because it's completely unsurprising. I'm great at parties btw.

Re: Breakthrough Announced in Dark Matter Detection Technology

#50

Post by dbasedweeb » Wed, Apr 11, 2018, 5:50 PM UTC

lulmerchant wrote: post #47

davidcuddeback wrote: post #45

Earlier quoted context omitted.

> scientists tend to have a very hard time acknowledging these limits of our understanding That couldn't be further from the truth. Scientists have been very upfront about the limits of our understanding, particularly when it comes to combining gravity with quantum physics. Listen to Neil DeGrasse Tyson or any other science communicator talk about general relativity or quantum physics and you'll hear them drive this…

The theories are incompatible at all energy levels, it's simply that those are two examples where we can't use them to accurately predict outcomes. Another not-extreme-at-all example where quantum physics completely breaks down is empty space. However, this discussion is deliberately missing the point, which is that it's not making predictions in everyday scenarios where physics fails. It's in describing the basic na…

I want you to engage in a thought experiment. I don’t code, and couldn’t program my way out of a wet paper bag. I assume that you can do much better than that, right? If I try to bullshit you about something you know a great deal about, from my position of ignorance, how long would it take for you to realize that I just knew little bits and pieces, but not the big picture? A sentence? Two?

And yet you seem to think that when it comes to physics, this same rule won’t apply. If you really care about the subjects you’re talking around, take some intro courses, really learn about it, or accept that you can only bullshit people who know less about the subject than you.

Phrases like, “the basic nature of our universe” sound good if you don’t know the first thing about the topic at hand, and probably impress people with no education or experience on said topic. To others, they’re huge giveaways that you don’t know what you’re talking about. Other red alerts are, “What is space?” “Empty space” and broad, substance-free critiques.

If you care about the subject and not just projecting a particular image of yourself, then bother to actually learn about them beyond the level of pop science. Critiquing something you demonstrably don’t have a deep knowledge of is a pointless exercise unless you’re just trying to impress people who know even less about it than you.

Here are some resources.

Intro To SR: https://ocw.mit.edu/courses/physics/8-20-introduction-to-spe...

Intro to GR: http://www.staff.science.uu.nl/~hooft101/lectures/genrel_201...

Further reading on GR: Gravitation by Misner, Thorne, Wheeler.

Intro to QED: http://sophia.dtp.fmph.uniba.sk/~peterp/QED_A.pdf

http://hepwww.rl.ac.uk/hepsummerschool/Evans%2008%20Intro%20...

https://www-thphys.physics.ox.ac.uk/people/FrancescoHautmann...

Intro to QFT: QFT Demystified is a great starting point...

Quantum Field Theory by Claude Itzykson and Jean-Bernard Zuber

Anything by Zee, especially “For The Gifted Amateur”