Neutrinos got that mass!
- Thread starter Reynard
- Start date
A
Anonymous
Guest
phavoc said:
But you are not testing gravity, nor are you observing it. You are detecting only the influence of gravity on objects by the fact that they fall. We cannot detect gravity waves, nor can we determine if gravitons exist. We would say this is an "indirect detection". The only reason you believe in the theory of gravity instead of pixie dust, is that the equations appear to correctly predict the speed at which things fall.
How is this different from dark matter, for which we also have an indirect detection? We know it's there because we see its effect on the rotation rates of galaxies. And it also relies on theory of gravity.
And what's more, we haven't been able to directly detect gravity for 500 years, yet you find 70 'upsetting' for dark matter?
Moppy said:
We can test for it at any time. We even have a formula for it (force = mass * acceleration). Which, of course, varies depending on where in the 'verse you are measuring it. Acceleration on the surface of the Earth is 9.8 meters/second squared. Acceleration on the moon would be different, just as it would be different on Mars or Venus. And, I dunno, there's also the gravitometers that can measure changes in gravity. They aren't as neato as say a densitometer, but at least they aren't fictional.
I see where you are going with your argument though. Where is the magical 'gravity' wave, or graviton (which is hypothetical) that I can detect with my instrument. The fallacy with your argument against measuring it is that it IS an observable force. If you interchange it with other parts of the equation the answer remains the same. Gravity was theorized and has been proven - in as much as anything in science can be proven. All of Einstein's work (and indeed, even dark matter itself) rests upon the confirmed concept of the existence of gravity. I could argue, how do I measure color? It's just an arbitrary concept and it's not even universal because different people view color differently. But the majority of science and society seem to agree on certain definitions (except for that pumpkin spice color... jury is still out on that one).
So it goes back to the same question - how do you measure the mass of something you can't measure? You estimate it. And when your equation doesn't seem to balance, you put something in there to make it balance. What is the mass of a quasar? We haven't a clue. Why are quasars the brightest objects in space, outshining an entire galaxy of stars? Well..... we THINK it's because they are tied to blackholes (what's the mass of a black hole? why can super-massive black holes exist when so far the math is pointing to them supposedly collapsing upon themselves to form a white hole?)
Yes, I still question the idea behind dark matter. Who knows, maybe I'm wrong and it will get proven. Yet I still have no qualms about placing some reasonable limits to blind acceptance of unproven theories when it's already proven we've got many other mysteries and unknowns within the physical universe. And these mysteries also lend themselves to answering the conceptual idea that dark matter exists. Like I keep saying, there's so much out there we have barely scratched the surface in terms of understanding. I think it's a wee bit early to say we know how much a universe can mass.
A
Anonymous
Guest
You have said (paraphrasing) the following:
(1) We can observe dark matter it by its effect on galactic rotation speeds. This is the same as observing gravity by seeing its effect on the acceleration of falling objects. We experience the effect of dark matter daily in the rotation rate of our own galaxy.
Why are these are different?
(2) If you beleive gravity is "correct", then gravity does not correctly predict the rotation rate of galaxies unless we either (a) modify gravity or (b) add additional mass.
(3) If you have problems with the mass of the universe, and need to add more matter, then this matter has to be very hard to detect or we would have seen it already, and you have now invented dark matter.
Conclusions: Either you require dark matter to balance the mass of galaxies to match observation, or you must admit theory of gravity is incomplete. Now the majority of people who have studied this problem find the first more likely, because they understand how solid general relativity is.
Now to respond:phavoc said:
(1) We can observe dark matter it by its effect on galactic rotation speeds. This is the same as observing gravity by seeing its effect on the acceleration of falling objects. We experience the effect of dark matter daily in the rotation rate of our own galaxy.
Why are these are different?
(2) If you beleive gravity is "correct", then gravity does not correctly predict the rotation rate of galaxies unless we either (a) modify gravity or (b) add additional mass.
(3) If you have problems with the mass of the universe, and need to add more matter, then this matter has to be very hard to detect or we would have seen it already, and you have now invented dark matter.
Conclusions: Either you require dark matter to balance the mass of galaxies to match observation, or you must admit theory of gravity is incomplete. Now the majority of people who have studied this problem find the first more likely, because they understand how solid general relativity is.
We haven't observed ANY dark matter. We have observed things that don't quite fit our model, and there are only a handful of "good" examples where observations may indicate dark matter exists, and even those aren't universally agreed upon within the community. We have, however, observed many other things (that you conveniently keep avoiding) that we can't explain either.
I haven't a clue behind the math for Einstein's work. I do know, however, that the quantum theory is presented as a separate, parallel explanation to his work, and that the scientific field has yet to reconcile the two theories. And no, I can't do the math for quantum theory either. Einstein's work is still considered incomplete, and it's also part of the same field that posits that dark matter does exist. Why? Because many scientists feel that there is still more to learn, and possibly even a whole new field of physics that has yet to be quantified and invented.
So again we come back to the same things - we don't know what yet we don't know, and we've yet to explain things fully for what we kind of know.
I haven't a clue behind the math for Einstein's work. I do know, however, that the quantum theory is presented as a separate, parallel explanation to his work, and that the scientific field has yet to reconcile the two theories. And no, I can't do the math for quantum theory either. Einstein's work is still considered incomplete, and it's also part of the same field that posits that dark matter does exist. Why? Because many scientists feel that there is still more to learn, and possibly even a whole new field of physics that has yet to be quantified and invented.
So again we come back to the same things - we don't know what yet we don't know, and we've yet to explain things fully for what we kind of know.
A
Anonymous
Guest
Ah I see what you're saying. You're saying you don't fully trust general relativity (effectively the theory of gravity) and this is why you have a problem with dark matter. That's OK - that's not actually inconsistent. If you don't think gravity is correct, you aren't required to think about dark matter.
What I don't understand is why you believe gravity is "proven" in this case (where you don't trust general relativity). All we can say about it is that we have some equations that define how it works, and that it appears to behave as they say it does, so we conclude the force we feel that pulls things downwards is gravity. We've yet to actually see it in the way that you require we see dark matter - we can't detect gravity waves, for example. How do you know the theory is correct? As I asked before, how do you know it's not pixie dust? The equation says it isn't but you've said you don't trust the equation.
What I don't understand is why you believe gravity is "proven" in this case (where you don't trust general relativity). All we can say about it is that we have some equations that define how it works, and that it appears to behave as they say it does, so we conclude the force we feel that pulls things downwards is gravity. We've yet to actually see it in the way that you require we see dark matter - we can't detect gravity waves, for example. How do you know the theory is correct? As I asked before, how do you know it's not pixie dust? The equation says it isn't but you've said you don't trust the equation.
Moppy said:
Ah, you are incorrect good sir! Please re-read what I typed and you'll notice that is never mentioned. All I did was say that those in the field believe it's incomplete AND a parallel area of science (quantum theory) has yet to bridge the gap between the two school's of thought.
Moppy said:
My whole and entire issue related to dark matter is that somebody couldn't balance an equation when trying to estimate the mass of the universe. And regardless of who or what you are, I would think trying to estimate the mass of something that, in theory, has no boundary, is a bit silly. If the universe truly is infinite, then it has infinite mass. Even measuring the visible universe with it's thousands of known galaxies is something we simply don't have enough knowledge of. You continue to ignore the mysteries and unexplained phenomena of the universe and refuse to acknowledge that there is much we don't know. Yet you seem very confident in the knowledge that these other things are not only well known, but totally understood (when those in the field of cosmology are still discovering and refining theories). Did you notice where I said gravity can be measured? And that's not ME personally saying that. Crack a science book and you'll see that science says that. Lots of people smarter than me haven't figured out how to build a gravity wave detector, but they have figured out how to measure and prove it exists. The jury is still out on Pixie dust though. That might be one for the Disney folks to solve.
You can read whatever you like in to my replies, but I think it's a bit pointless to go further from here. I address your questions, you ignore mine. It's fine to agree to disagree. This isn't the Royal Astronomical Society and we aren't playing out the roles of Chandra and Eddington. I would rather talk Traveller than continue this.
phavoc said:
You missed that part.
We already know from other sources how much normal matter there is in the universe. Finding atomic hydrogen (where it was predicted to exist 80 years ago, I might add) does not change the fact that we know the amount of matter in the universe.
IOW: We already know how much stuff is in the beaker, even if we found unexpected stuff in the beaker, it wouldn't mean that the amount of stuff has changed, just its composition.
Here's a quick primer on what's known and unknown about dark matter: https://medium.com/starts-with-a-bang/10-facts-everyone-should-know-about-dark-matter-1ce2b222cf08
Reynard
Emperor Mongoose
We didn't put Dark Matter into the equation, we put a placeholder called 'dark matter' to remind science there is a gap in the equation that needs more study to discover what the actual missing element is. This is a little different than people historically plugging an unknown phenomenon with magic explanations and reminding people don't question it or else.
Dark matter as an actual substance is the work of imaginary fiction somewhat akin to universal aether ships could sail in between the planets or stars.
Dark matter as an actual substance is the work of imaginary fiction somewhat akin to universal aether ships could sail in between the planets or stars.
Reynard said:
Not quite.
We know that there's something that acts in ways that identify it as matter as opposed to energy - it has mass, it generates a gravitational field that we can detect, but what we don't know is what it is because whatever it is, it doesn't interact with itself or with other matter much, if at all. It could be a standard model particle of some sort, but most likely it isn't.
There's something there, we can see its presence, we haven't identified it yet.
A
Anonymous
Guest
PUTS ON SCIENCE HAT.
WALL OF TEXT INCOMING.
I apologise if I have offended your religion (meaning personal beliefs about how fundamental things like gravity are and the limits of knowlege - not about Gods).
As someone with a scientific education, I am going to shock you now by saying science does not prove anything. What it does is disprove false theories. We cannot actually prove anything (except in maths). What we can do is demonstate that our theories are consistent and have support from experimental observations. Science is about making a model of "reality" and it would be nice if that model represented actual reality, but we understand this is an impossibility to guarantee.
This is part of the scientific method, and is taught when you take a "real" science at degree level. (Like, a science that doesn't have science in its name, like physics, as opposed something like 'computer science' which isn't really a science but added the world to make it sound like one).
Scientists do not like to use the word "proof". That's more for journalists to sell the discovery. For example if you read a science paper, the language will be something like "These results show 99.999% agreement with theoretical prediction". It's the newspaper that says "scientists prove X".
We can't prove it for a number of reasons: the easiest to describe is that we don't know if we live in an advanced computer simulation. In which case we are able to make zero truthful statements about "true" reality. "Theory works when tested" is the best we can do.
The classic example taught is the white swans. We can say "all swans are white" but we can't observe all swans for eternity to verify. We say that we've never seen a black one in N years, and that we have a genetic rule that makes them white. (Yes, Austraila does have non-white swans: it's a thought experiment - but think how we "prove" the genetic rule without using some other rule, that's also only supported by a lack of counter-observations?)
So I'm not making any false assumptions of knowledge. In fact, I have just defined the upper limit of scientific knowledge as being: "We don't know jack. All we know is our model works when we test it. Here's a useful model you can use."
If you want "truth" you need to see a priest. Only religion claims to have all the answers written on infallible tablets of stone by a supreme authority.
The reason I appear to be ignoring some of the things you have said is that they have been shown to be incorrect by direct observation. However this is bad style to ignore them, for which I apologise again, and I will address all points in future.
Here is an actual example:
The concept of "the observable universe" (observable meaning "interactable") is quite central to cosmology and places finite bounds on the size of the U that we need to consider. If we leave the observable U we lose the ability to test our theories and we have to rely on faith.
Let's look into why this claim is being made and why you have problems with it.
You are not understanding the difference between detecting something directly, and detecting its effects.
Imagine if technology did not exist to view cats remotely. Say we're in the medieval age.
Imagine if we said "cat exists because dead mice appear and milk vanishes when I am out of the house". Each time we test this by leaving milk out and exiting the house, milk vanishes and dead mouse appears. Later I refine theory to calculate size of cat by the amount of milk consumed and portion of dead mice eaten. Everything is completely consistent and the equation is always right when it is tested.
I then theorise that if I put cat repellant in the house, milk consumption and mouse corpse accumulation will decrease, and again I am shown to be correct.
We can exclude a malicious human intruder who is able to recognise cat repellant by putting in an alarm (our equipment is not sensitive enough to detect an intruder the size of cat).
Now there's nothing else of that size that drinks milk and murders mice so I conclude cat theory is correct.
Every test of cat theory is consistent with theory, even down to the exact amount of milk consumed.
I've never seen the cat.
This is where we are with gravity and why we're operating gravity wave detectors (to correct a further inaccuracy: we know how to build them, and they're currently operating but have yet to achieve success).
We also do have dark matter detectors, and at least one of them is seeing something, but we aren't sure what that is yet (it could be a bug in the detector).
Now those same equations of gravity are saying there must be additional mass in galaxies, in certain locations.
The equations of gravity could be wrong. But thinking back to the cat, it's more likely we have a cat than a mouse-murdering-pixie with a taste for milk, or that the equation is subtly wrong. Further, all alterantive equations have even more problems (they directly contradict current observations) and ALSO require additional mass.
The world does not have not make intuitive sense to us, and there's no philisophical reason that 95%+ currently evades direct detection. In fact, most of it already does (think back to gravity).
WALL OF TEXT INCOMING.
I apologise if I have offended your religion (meaning personal beliefs about how fundamental things like gravity are and the limits of knowlege - not about Gods).
As someone with a scientific education, I am going to shock you now by saying science does not prove anything. What it does is disprove false theories. We cannot actually prove anything (except in maths). What we can do is demonstate that our theories are consistent and have support from experimental observations. Science is about making a model of "reality" and it would be nice if that model represented actual reality, but we understand this is an impossibility to guarantee.
This is part of the scientific method, and is taught when you take a "real" science at degree level. (Like, a science that doesn't have science in its name, like physics, as opposed something like 'computer science' which isn't really a science but added the world to make it sound like one).
Scientists do not like to use the word "proof". That's more for journalists to sell the discovery. For example if you read a science paper, the language will be something like "These results show 99.999% agreement with theoretical prediction". It's the newspaper that says "scientists prove X".
We can't prove it for a number of reasons: the easiest to describe is that we don't know if we live in an advanced computer simulation. In which case we are able to make zero truthful statements about "true" reality. "Theory works when tested" is the best we can do.
The classic example taught is the white swans. We can say "all swans are white" but we can't observe all swans for eternity to verify. We say that we've never seen a black one in N years, and that we have a genetic rule that makes them white. (Yes, Austraila does have non-white swans: it's a thought experiment - but think how we "prove" the genetic rule without using some other rule, that's also only supported by a lack of counter-observations?)
So I'm not making any false assumptions of knowledge. In fact, I have just defined the upper limit of scientific knowledge as being: "We don't know jack. All we know is our model works when we test it. Here's a useful model you can use."
If you want "truth" you need to see a priest. Only religion claims to have all the answers written on infallible tablets of stone by a supreme authority.
The reason I appear to be ignoring some of the things you have said is that they have been shown to be incorrect by direct observation. However this is bad style to ignore them, for which I apologise again, and I will address all points in future.
Here is an actual example:
If the unverse is infinite, we can still only interact with a small portion of it due to the fact that all interactions take place at light speed or lower. Given that it also has to be heterogenous (similar all over, our part is not special: otherwise we live in a simulation) then whatever is beyond the light speed horizon can have no effect on us.phavoc said:
The concept of "the observable universe" (observable meaning "interactable") is quite central to cosmology and places finite bounds on the size of the U that we need to consider. If we leave the observable U we lose the ability to test our theories and we have to rely on faith.
Really? I am telling you we don't know what gravity is, and have not detected it directly. This is a pretty fundamental thing to not know, right?phavoc said:
Let's look into why this claim is being made and why you have problems with it.
phavoc said:
You are not understanding the difference between detecting something directly, and detecting its effects.
Imagine if technology did not exist to view cats remotely. Say we're in the medieval age.
Imagine if we said "cat exists because dead mice appear and milk vanishes when I am out of the house". Each time we test this by leaving milk out and exiting the house, milk vanishes and dead mouse appears. Later I refine theory to calculate size of cat by the amount of milk consumed and portion of dead mice eaten. Everything is completely consistent and the equation is always right when it is tested.
I then theorise that if I put cat repellant in the house, milk consumption and mouse corpse accumulation will decrease, and again I am shown to be correct.
We can exclude a malicious human intruder who is able to recognise cat repellant by putting in an alarm (our equipment is not sensitive enough to detect an intruder the size of cat).
Now there's nothing else of that size that drinks milk and murders mice so I conclude cat theory is correct.
Every test of cat theory is consistent with theory, even down to the exact amount of milk consumed.
I've never seen the cat.
This is where we are with gravity and why we're operating gravity wave detectors (to correct a further inaccuracy: we know how to build them, and they're currently operating but have yet to achieve success).
We also do have dark matter detectors, and at least one of them is seeing something, but we aren't sure what that is yet (it could be a bug in the detector).
Now those same equations of gravity are saying there must be additional mass in galaxies, in certain locations.
The equations of gravity could be wrong. But thinking back to the cat, it's more likely we have a cat than a mouse-murdering-pixie with a taste for milk, or that the equation is subtly wrong. Further, all alterantive equations have even more problems (they directly contradict current observations) and ALSO require additional mass.
The world does not have not make intuitive sense to us, and there's no philisophical reason that 95%+ currently evades direct detection. In fact, most of it already does (think back to gravity).
Reynard
Emperor Mongoose
Let me get this straight, and I do have a college degree without the word science in it, we don't really exist because we can't prove 'absolutely' we exist. Pixies, angels and magically floating castles do exist because someone (who doesn't exist as above) stated so and wrote it down.
This is one of those 'chair in a closed room' examples, isn't it?
This is one of those 'chair in a closed room' examples, isn't it?
Condottiere
Emperor Mongoose
There are holes in the void that are filled with ether.
A
Anonymous
Guest
You can prove to yourself that you exist, but that's one for philisophy and not science.Reynard said:
An Fhuiseog
Mongoose
Do you happen to know the name of this equation?phavoc said:
Okay, so first of all, you seem to be under the impression that it was by measuring the weight of the entire universe that we came to conclude that Dark Matter existed. It's much simpler. We just take the Milky Way and we can see that under the equations of General Relativity the visible matter of the Milky Way does not correctly give the rotational speeds for stars on the outer edge of the Milky Way. Hence either:phavoc said:
(a) General Relativity is wrong (Modified gravity hypothesis)
(b) General Relativity is correct but there is additional non-visible matter (Dark Matter hypothesis)
Neither (a) or (b) involve hubris, they're just the two possibilities. Neither involves balancing an equation (that's not a well-defined term) and balancing their equations isn't more necessary be they are theoretical. In fact they're not that theoretical at all. Remote from everyday human experience, but they involve a well understood piece of mathematics (General Relativity) and solid observational facts (Milky Way's rotational velocity).
Since both were initially proposed, all evidence that has come to light supports (b) rather than (a). The bullet cluster for example, shows significant gravitational lensing by some invisible matter when two galaxies collided, not only that, but the total mass of this matter is what General Relativity predicts the total mass of two galaxies worth of dark matter should be.
In the abstract, yes there is nothing to say that Einstein got something in General Relativity wrong, it just seems to not be case based on evidence.
An Fhuiseog said:
I do not. It was something I read, in AV Week I think, years ago. It wasn't a huge issue for the change, but it did surprise a lot of engineers. As an aside, The Wrights found that some previous mathematical models related to drag coeffecients were incorrect (and also somewhat miss-applied since the equations were based on pure flat surfaces where their propellers were curved). More trivia!
An Fhuiseog said:
Between dark energy and dark matter, the parts of the observable universe only account for 5% of the total mass. We can't actually see a lot of our own galaxy because of our position and the many planetary objects blocking our views (thermal, radiation, as well as visual). So we extrapolate, and that's a reasonable assumption to make. We do it everyday in our normal lives as well as in other areas of science. Sometimes it works out, and sometimes it does not. Einstein was brilliant, but he made mistakes too in his models. As did Newton and I'm sure many others. Theory is fine, but openly questioning it rather than assume it's perfect is rather silly in my book. And the bigger the equation, the more likely you should question it until you can actually prove it, or at least continually show that something is out there. As it was pointed out up-thread, you can't "prove" anything (though personally I consider that semantical cop-out, as lawyers will do the same thing and avoid any unpleasant fact they can).
An Fhuiseog said:
Einstein got a number of things wrong (and most people can only wish to be as "wrong" as he was). Some of his mistakes opened up entire new thought fields that are still being explored. We have seen in science time and time again that what we originally thought was right was later proven to be wrong, or incomplete. Whether or not dark energy/matter is that way, or to what extent, remains to be proven. When 95% of the visible universe can't be seen or detected, one should have healthy skepticisim I think.
I keep re-iterating that we do NOT know how the universe works. We are still learning and taking baby steps in so many areas. Science loves to explore and understand the universe and I enjoy the journey. My opinion is that some things defy explanation at this point because we don't have the underlying knowledge to understand. It's akin to asking a 7yr old who just learned his multiplication tables to tell us how calculus works. He hasn't mastered nor understood all the things in between.
So in this case we have models for black holes, which have changed over time by the way. We have theoretical models that say white holes exist, but we can't explain how, or really why, nor have we seen one, but we have the maths and theory. That doesn't mean it exists. It just means we have a theory that seems to work out on a whiteboard.
A
Anonymous
Guest
He is PROBABLY referring to the Equal Transit Time fallacy that is often taught in school textbooks.An Fhuiseog said:
This states that airflow conforms to the shape of the wing and that since the path over the top of the wing is longer, the air must flow faster in order that the transit time for upper and lower surfaces is similar. And that because the flow is faster, the pressure must be lower above the wing, thus producing lift.
It is trivially proved false by imagining what happens if the aircraft flies inverted (shocker: it still has lift), yet for some reason school textbooks still love it.
Every few years someone has a rant about it and the newspapers sensationalise it. This comes up like once every few years on aviation sites. :-(
An Fhuiseog
Mongoose
Yes, but the point is nobody is assuming they are perfect. Rather, the possibility is that either General Relativity is wrong or there is Dark (i.e. non-photon emitting) Matter. When this was investigated via observation (i.e. not assuming, but checking), the observational evidence seems to favour the presence of Dark Matter and the correctness of General Relativity.phavoc said:
The field equations have an enormous amount of observational evidence in their favour:
Accurate predictions of Earth's gravitational field
Time dilation effects near Earth
Orbit of Mercury
Orbits of Neutron stars
Gravitational lensing of light
So it has been questioned, it's just it has been found to hold up to tests.
I am referring explicitly to General Relativity. Einstein seems to have been correct with General Relativity based on observation.
I'm also not aware of fields opened up by Einstein's mistakes.
Yes and scientists did. However, evidence seems to show that Dark Matter is the more correct hypothesis.
No they haven't. Black Holes are modeled as solutions of General Relativity, as they have been for 100 years at this point.
This isn't accurate. General Relativity states exactly when, why and under what conditions a white hole will form. It also predicts the matter required to create a white hole would have to break certain constraints that actual matter does not (the so called "Energy conditions").
