Dark Matter : Is it science?

Discussion in 'Astronomy, Exobiology, & Cosmology' started by The God, Mar 8, 2017.

  1. The God Valued Senior Member

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    Vanished is too harsh. It is just that we do not know anything beyond EH. Second part is right, BH is BH, it will be indistinguishable.
     
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  3. rpenner Fully Wired Staff Member

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    Dusty hydrogen clouds communicate that heat to their dust particles by collision which can radiate away the heat by Planck's law, while transparent hydrogen gas is a very poor emitter of blackbody radiation. So dusty hydrogen clouds collapse faster than pure ones.

    As far as we know, nothing.
    As far as we know, no.
    Is WHAT due to WHAT?
    Since Dark matter is the larger component of galaxy clusters, it is more likely that clumping of dark matter formed galactic clusters and perhaps galaxies. At the star-level baryonic matter physics dominates.
    While collision with a black hole would cause dark matter to be eaten, without interactions angular momentum makes black holes a very hard target to hit and so most dark matter would treat it like any other source of gravity.
     
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  5. exchemist Valued Senior Member

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    Well that's what I mean by "vanished", I suppose - undetectable and destined to remain so.

    But...that makes me think....what about Hawking radiation and the idea that matter from pair-production, sucked into the BH from the vacuum, might eventually cause a BH to evaporate..... Presumably if the black hole were composed of DM this would not happen, as it would not interact with ordinary matter. Unless there could be dark matter pair-production (yikes!). I suppose we have no idea, yet.

    Probably a pointless speculation.
     
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  7. The God Valued Senior Member

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    This HR is...ok leave it. I will be trolled if I speak about HR being an old age nonsense by Sir SH.
     
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  8. rpenner Fully Wired Staff Member

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    Since pair-production happens at the event horizon, not where the DM hit the singularity, that does not follow. A 100% DM-created black hole, a 100% light-created black hole (possible?) and a 100% baryonic-matter created black hole should have identical thermal Hawking radiation spectra.
    Completely speculative for black holes of masses of more than 2×10^10 kg (based on Hawking radiation temp and assumed WIMP model of DM with mass of 10-3000 GeV/c^2, see section 26.1.2 of my second technical reference) since we have a cold dark matter cosmology, pair production of DM should only happen at ridiculously high temperatures.

    You should know that "trolled" is not the correct verb. Maybe now is the time to quit for the day and reconsider the PM.
     
  9. exchemist Valued Senior Member

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    Whatever was in that PM must have been good stuff. We have had a very good and well-tempered discussion. I really appreciate it.
     
  10. The God Valued Senior Member

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    What is this? Some kind of threat? Such open arrogance from a mod is despicable.
    And find out the correct verb and do the honor of correcting it.
     
  11. exchemist Valued Senior Member

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    OK, I won't get into that either - outside my expertise. But thanks for the good discussions today.
     
  12. The God Valued Senior Member

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    Since disclosing my banishment score is not an offense, for record sake I am at 95. 5 more and bye bye...
     
  13. exchemist Valued Senior Member

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    OK, sorry to hear that but listen, it has been a pleasure discussing with you today. You are off my Ignore list and on present evidence I will leave it that way. Perhaps we should give one another a chance.....
     
  14. The God Valued Senior Member

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    I never keep anyone on ignore, not even kristoffer. I look for ideas, beyond the standard copy book stuff, it can come from anyone. Problem is when it is opposed just because it is against well established.
     
  15. rpenner Fully Wired Staff Member

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    Clearly, I am warning you for your own benefit.
    Hawking radiation dates from 1974, when Hawking was in his 30s. Not only have you thrown an ad hominem attack on an idea, you predicated it on a lie and this was a completely unforced error on your part.
     
  16. The God Valued Senior Member

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    Thanks for correcting this early 30s part. I don't get this 'ad hominem attack on an idea', its my opinion. Many mainstream scientists are also not ok with HR. So what's your problem? Breath man breath, no need to treat scientific theories as gospel truth. Just couple of hours ago you conceded spin is ...metaphysics.
     
  17. rpenner Fully Wired Staff Member

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    You did not stop at stating an opinion or that the preconditions for Hawking radiation (a black hole of mass of less that 10^23 kg) have not been observed yet.
    The way to attack an idea is to 1) understand it, 2) apply it, 3) show how it fails to be satisfactory in some sense.
    What you did was say it was "old age nonsense", applying an offensive stereotype of senile dementia to the proponent of an idea you disfavor, and committing the fallacious argument of attacking the author of the idea rather than the idea. Even an old fool can be factually correct, so attacking the speaker is a foul, a breach.
    Finally, you are not in the position to have a qualified opinion on the topic, as you would need to be able to do thermodynamics of quantum field theory in curved space time to follow the idea from foundations to conclusion.
    That too is a fallacious attack on the idea. It doesn't go away because it's unpopular.
    I'm enforcing rules of civil behavior and the forum rules in particular. In particular, you are not allowed to advance your opinions in contradiction to scientific observation AND theory on the main science forums. Neither are you allowed to ignore your burden to carry your own argument and you engaged in exactly that behavior when you pooh-poohed an idea as "old age nonsense" that some are "not ok" with. That's how a politician deflects charges that he has been embezzling public funds, not how a scientist argues.
    If you want to battle scientific theories, you need to arm yourself in a battle of the empirical facts and the wits, not a battle of personal slurs and poorly sourced irrelevant opinions.
    That is your personal misunderstanding. Spin is observable. Spin is describable. Spin is not, without a more fundamental physical theory than we have today, decomposable into anything else that is observable or describable.

    If you want truth, go see a philosopher. In science we stick with what we can measure and what we can calculate. And if you don't have the background to keep up, your opinion is an unqualified one, unworthy of being rallied behind.
     
  18. The God Valued Senior Member

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    By referring to PM you irresponsibly conveyed an idea that you admonished me in PM, this is no mature mod action.

    You explicitly warned me not to discuss PM openly then why did you give away the PM impliedly? Where was the need for showing the stick? Grow up Rpenner, mere knowledge of maths and subsequent expertise in latex (or whatever) typing does not make you grand. Your fairness, maturity and dignity must show as mod.
     
  19. exchemist Valued Senior Member

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    Oh dear. It was good while it lasted, but I have a feeling you may be leaving us.
     
  20. The God Valued Senior Member

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    No, it should not happen. I was explicitly warned that I should not discuss about the content of his PM, so naturally he should have also honored not to directly or indirectly refer to that PM. He breached that implicit understandimg. So my last post is certainly not 'unforced error'.

    When he corrected me that HR was proposed by Hawking in his youth, I immediately acknowledged that. But the fact remains that HR is still not well established in mainstream circle. Saying this is no criticism of HR. Yes, calling it senseless was, but you know I restrained myself in that post.
     
  21. rpenner Fully Wired Staff Member

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    My sources say it is widely and generally accepted as provisionally true. So you have not correctly stated a fact. It's in textbooks, review articles and pop physics articles without a hint of fringe status.

    Example: Section 11.11 of https://books.google.com/books?id=xma1QuTJphYC
    Example: Section II.4c of http://pdg.lbl.gov/2016/reviews/rpp2016-rev-extra-dimensions.pdf
    Example: http://wiredcosmos.com/2015/05/29/the-science-of-black-holes-hawking-radiation-explained/

    The last group of people I saw rail against it: anti-LHC nutters.
     
    Last edited: Mar 10, 2017
  22. Xelasnave.1947 Valued Senior Member

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    I hope we settle down... things were really starting to become rather good... starting to look professional this place..
    Alex
     
  23. The God Valued Senior Member

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    Yes Xelasnave.

    Based on that PM, I assessed my behavior. Paddoboy's voluntary exit interview convinced me that its not worth arguing here, because higher the ignorance higher the resistance to change.

    So, I took a hard look and thought of pulling out the forum from Kittamaru sponsored Trumpforum. I wanted to populate this section with meaningful science content wherein people can enjoy without weirdo looking maths. But then Rpenner happened. Anyway, this will also pass.
     

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