See article at Astrobites.
As I was saying all along:
1. Gravity bends light, which is why we get gravitational lensing of light.
2. Gravity waves (in a vacuum) travel at speed of light (in a vacuum). This was measured twenty years ago, but it was a sensible assumption all along.
3. LIGO tells us that gravity waves and light waves from the same event arrive at the same time (give or take a fraction of a millisecond), therefore they must have taken the same path to get here.
4. If the light waves were bent before they got here, then so were the gravity waves.
5. Therefore, there must also be gravitational lensing of gravity, as shown in the second diagram down. Gravity gets focused along the plane of a spiral galaxy. There's less than you'd expect above and below the plane, and more than you would expect around the plane.
For calculation purposes, you can take the common sense approach and say that matter in a Galaxy distorts/creates gravity and shapes the gravitational field. Or the more esoteric view that a galaxy is a giant gravitational field with a certain shape and distribution, with stars trapped in it to balance it all out.
Tuesday, 18 August 2020
"The Alternative to Dark Matter May be General Relativity Itself"
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14 comments:
I quite like that. It's a good idea.
D, problem is, when they've done the calculations, they won't mean anything to mere mortals like me. But intuitively, it seems plausible.
Me neither. But your point about gravitational and light waves arriving at the same time makes a lot of sense to those of us that don't know the details of the maths.
D, yes, those LIGO people are doing sterling work. They have discovered - or confirmed - loads of interesting stuff.
1. What is gravity made of? Is it just an image of reality until we truly discover its nature? In which case it's not an axiom
2. Did you know the speed of light is not a constant? Neither is BigG. Both have been set in stone as a fudge to make the equations for above marry. So that is scientific question begging
3. I fear you're taking the quantum for granted here, where theres no material cause and effect measurable yet it still happens. Is your reasoning a post hoc logical fallacy?
4. Post hoc again from non axiomatic and acausal material events
5. Ditto
"They have discovered - or confirmed - loads of interesting stuff."
This is a quasi religious statement. Or scientific religiosity.
RS
1. Nobody knows, that's what makes it so fascinating
2. For sure, I was referring to speed of light in a vacuum.
3. I have no idea what you are talking about. I suspect neither do you.
4. Ditto
5. Ditto
The big difference is that science is about intellectual curiosity, observe the world without prejudice and willingness to revise explanations, do experiments and so on, it's a never ending process. In a few hundred years' time they'll probably laugh at our explanations and have something better, a few hundred years after that, their ideas will also be superseded, and so on for ever.
Religion is pretty much the opposite of all that. I'm not sure what religious tract tries to explain how to calculate the apparent speed of a distant galaxy and try to explain why it appears to be moving away from us that fast (we don't know why and probably never will, it is pretty irrelevant but at least we can come up with some formula to explain relative speeds of different galaxies - all to satisfy our intellectual curiosity).
Was 3 an ad him back there :)
Or was it just that your world view is limited to material cause and effect?
The rest is question begging from a limited world view: that unless something can be measured or repeated, it didn't happen, the opposite of curiosity
See Rupert Sheldrake's banned Ted talk and the scandal that follow by the skeptic stasi.
I'm not religious, but it certainly helps people find meaning where science fails more, the more time goes by.
If youre authentically curious, why not stop defending and ask for clarification? It's a tell tale red flag
RS, you haven't had an interesting insight into anything for years, science or otherwise, it's all quasi-religious clap trap.
There is no meaning or deeper purpose behind the speeds that stars or galaxies move. It's just INTERESTING in and of itself.
MW more ad hom and straw men. Should you moderate yourself? Why resort to rudeness and personal attacks.
If you want to be interesting and fun why not attack my ideas not my person?
And are you saying what you speak about is truth and reality? That sounds like a high priest preaching.
Have you watched the Rupert Sheldrake banned Ted talk. He discusses all this very well. And scientifically.
Is it not EVEN more interetesting that science BELIEVES just as much as religion does, just in different form?
I guess it all depends on how serious you are about your beliefs.
RS, you don't have any ideas. That's the problem, it's all vague pseudo-religious clap trap.
Come up with some actual sensible explanations, or some policy ideas or something.
RS, there are plenty of commenters here who don't agree with me on stuff, that's fine, they are Homeys or Alarmists or Neo-lib's or whatever. At least it's clear what we are discussing, even if we will never agree. That's all part of the fun.
With you, it's never clear what you are actually trying to express, apart from being arrogant and rude.
MW are you the only one who's allowed to be arrogant and rude? See your last comment.
The problem is in your limited view of the world, I'm asking the wrong question. So it seems non sequitur to you.
And this is because you're limiting your thought to what you already think is truth.
I remember at the pub once you fiercely declared "but I have the truth!".
That was a red pill moment for you. Others present noticed too.
I'm not saying I'm immune to this limited world view. I am saying I recognise that I suffer from it too.
The difference is I know, that I don't know.
Whereas, you don't know, that you don't know yet, largely because your thought is directed by an ideology,religion, politics etc.
Capiche?
RS, what's your view on whether the most likely explanation for the rotation speeds of stars in a galaxy is Dark Matter, MOND, relativity, primordial black holes or what Stacy McGaugh/Eric Verlinde say, or indeed something else?
That's what we are discussing here. There is no absolute 'truth' to science in your quasi-religious sense, it's a question of what seems most likely, given our limited knowledge. In a few decades or a few hundred years, they'll come up with something better, so what?
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