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Author Topic: Science vs. Religion  (Read 28137 times)

Offline rosy

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Re: Science vs. Religion
« Reply #50 on: 19/05/2005 21:02:58 »
quote:
Now, what question would a respectable scientist - being impervious to dogma - ask first, before investigating the matter any further?

I think actually a respectable (say) chemist would say "Oh really? Is that unusual? Would you like to explain why?"
I take the approach that the "last man to know everything there was to know", whether that was Goethe, da Vinci, J S Mill or Milton, died some time ago, that there's no way I can understand everything, and that unless it goes sharply against my prejudices about how the world works (or I know that there's a debate going on as to the validity of the results) I'll assume that the experts have more idea than I have in most fields.
That's not to say I'd be particularly surprised to find anything I'd assumed was accurate from such sources had been re-evaluated.
 

Offline chimera

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Re: Science vs. Religion
« Reply #51 on: 19/05/2005 21:24:28 »
I think the best scenario is when people are able to question the validity of ANY thing, which is not the same as trying to be a walking encyclopedia. There is such a thing as common sense, or there should be... funny thing is children seem to have more of it than grownups, even  :)

And respectable has nothing to do with it, really. Nor are the best physics teachers by default the best physicists, quite the contrary even.

Also remember the fate of Lord Kelvin, who was such an overwhelming personality and general Mr. Know-it-all he singlehandedly put scientific progress in the second half of his life to a virtual standstill. So, equally try to see someone who has made a career of explaining stuff over half a century old as not exactly the best  source or judge even for bleeding-edge technology. You cannot have it all...


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Offline rosy

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Re: Science vs. Religion
« Reply #52 on: 19/05/2005 22:19:19 »
Um, my apologies. I may have been being slightly flippant. I would, of course, agree with you that questionning the validity of an assertion is a generally useful thing to do (I might go so far as to be offended that you seem to have assumed otherwise, but possibly that degree of hamming risks being taken seriously if put down in text).

All I was suggesting was that, as you point out, people are often orders of magnitude out in how big they think things are. But on the other hand, if someone tells me (a chemist, of sorts) "oh, that black hole is n lightyears across" I don't really see that it's of much immediate interest to me unless I know, or have just had it explained, that the largest known black hole to date is (n-5) or n/10 lightyears across.
That was why I made the point about *unless I know it's a subject of debate, or I find it very surprising*... I wouldn't personally know how even to approach the maths!

I wasn't suggesting that anyone *should* know everything. That was my point... that the assertion you cite about the enormous black hole is *of course* perfectly believeable until you do the maths unless you're tuned into that area of thought anyway.

Oh, and I used the term "respectable scientists" because you did. In my book they are the ones who haven't ossified into thinking their theories are right and stopped looking at the evidence... which is to say scientists worthy of respect. Did you mean something different? My comment about respectable chemists was intended to mean that a chemist who might be doing terrific cutting edge science in, say, molecular orbital interactions, might need to be prompted to query the size of a black hole. If you work on the nanometer scale, anything over about a micron can be classed as "big" and left at that... unless you happen to be discussing black holes with a flatmate.
 

Offline chimera

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Re: Science vs. Religion
« Reply #53 on: 20/05/2005 11:29:49 »
quote:
Originally posted by rosy

.. I wouldn't personally know how even to approach the maths!


Oh, that's relatively simple, you can even use google for it these days...

OK, let's put r= 1 lightyear.

(2 * G * ((3 203 * (10^9)) * (1.9891 * ((10^30) kg)))) / (c^2) = 1.00001814 lightyears

To create a black hole with a lightyear radius you need (just over) a whopping *3200* billion solar masses. That's over thirty of your average run-off-the-mill galaxies. So that's out.

Similarly, you can do calculations on how long it would take to create the incredibly large collections of galaxies known as superclusters. That's about 80 billion years, give or take a few. Considering the universe is supposed to be only 15 billion years old or thereabouts, quite a feat.

No astronomer has any answer to that, btw.



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Offline daveshorts

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Re: Science vs. Religion
« Reply #54 on: 20/05/2005 12:55:12 »
Did you actually find a report of this somewhere?

My guess is that the scientist wasn't talking about schwartzchild radius when they mentioned the size, - maybe it is the size of the acretian disk. A reporter then heard size, black hole and 3.5-5 lightyears and missed out the important bit...
 

Offline chimera

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Re: Science vs. Religion
« Reply #55 on: 20/05/2005 13:33:48 »
Yes, probably. But then still, the black hole would roughly be about 0,4 lightyears in diameter (1/12,5th following 4pi*d^2) , and that's still 1282 billion solar masses. Still way too many galaxies for comfort.

The living are the dead on holiday.  -- Maurice de Maeterlinck (1862-1949)
 

Offline daveshorts

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Re: Science vs. Religion
« Reply #56 on: 20/05/2005 14:59:20 »
Are the radio sources that shoot out of the top or bottom of an accretian disk related to black holes as they can be a few light years long can't they?
 

Offline chimera

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Re: Science vs. Religion
« Reply #57 on: 20/05/2005 19:53:33 »
Longer even, but I don't think they meant those... anyway, even 'supermassive' black holes turn out to be rather puny, if you take a closer evaluation, unless they've been eating outdoors in secret, of course... :)

Say a big whopper, that you sometimes read about, like 3 billion solar masses, would be a measly 0.000936638904 lightyears.

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Offline rosy

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Re: Science vs. Religion
« Reply #58 on: 21/05/2005 00:33:59 »
0.000936638904 lightyears

Wow, what precision.
 

Offline chimera

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Re: Science vs. Religion
« Reply #59 on: 21/05/2005 10:07:13 »
Don't forget those are approximate formulas, they'll never be precise to the exact cm or even kilometer, mind you, and these numbers are much, much longer in reality.

But lets put them a bit back into 'normal' perspective. The black hole supposedly at the centre of this galaxy is estimated to be 1 billion solar masses. That would mean it would have a radius of 2.95369965 10^9 = nearly 3 billion kilometers, so a diameter of twice that.

Now 6 billion kilometers at a distance of 8 kiloparsecs (2.4685442 10^17 kilometers) means trying to see an object of  0.0790660366 nanometers at 1 lightyear (9.4605284 10^12 kilometers) distance. An average atom has a diameter of 0.1 to 0.5 nanometers.

So basically you're trying to see something less than a tenth of an atom across at a distance way, way beyond Pluto.

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Offline rosy

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Re: Science vs. Religion
« Reply #60 on: 21/05/2005 10:59:29 »
Um, OK, what I meant was"I can't quite believe you can justify quoting anything like that degree of precision" possibly I should rephrase that as a question...

So... what.... that 9 significant figure number you've quoted is approximate? Or do you mean that the black hole you're talking about with mass three billion solar masses is somewhere round about 1E-3 lightyears across, give or take some.
 

Offline chimera

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Re: Science vs. Religion
« Reply #61 on: 21/05/2005 11:19:57 »
We just have a standard formula, and out rolls a size, but we do not have any visual confirmation of exact size, or the size of the accretion disk - several formulas for that, even -, and even those impressive lighthouse beams. All artists impressions are just that, without their incredible effects on their environment, making those at least visible, we wouldn't even know they were there... for a infinitesimal speck on the horizon, they have quite a 'drag'.

Oh and don't be impressed with a bit of google magic: here's the formula for the radius of a black hole (half of its diameter)

(2 * G * ((billions of solar masses * (10^9)) * (1.9891 * ((10^30) kg)))) / (c^2) in lightyears

(just cut and paste it into the google bar, and replace 'billions of solar masses' with any number) where google already knows what you mean with G and c, and can of course do it in  kilometers as well as lightyears or whatever measure you need. The rest of the formula are just pretty well known constants and values.

So fill in a 1000, and you have a pretty precise number for the black hole at the centre of this universe. Hope that makes you try out more stuff with it, it can be pretty awesome.

The living are the dead on holiday.  -- Maurice de Maeterlinck (1862-1949)
« Last Edit: 21/05/2005 11:22:18 by chimera »
 

Offline rosy

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Re: Science vs. Religion
« Reply #62 on: 21/05/2005 11:39:54 »
Yeah... to be honest I'm less impressed than, um, sceptical... infact now I've checked I'm outright disbelieving.
you have a precise number, but I don't believe you have an accurate number.
According to this website (the people who build NASA satelites, apparently)
http://ssd.jpl.nasa.gov/astro_constants.html
G is only known to an accuracy of 4-5 sig fig and so any calculations based on G will have an ABSOLUTE MAXIMUM accuracy of 4 SF depending on the accuracy of the other values you've plugged in. In this instance, you're using a mass accurate to 1-2 sig fig.
G = 6.67259 ( 0.00030) x 10-11 kg-1 m3 s-2

Given that I know you're rightly keen on questioning everything, it's proabably worthwhile to think twice bfore copy-pasting out of a calculator ;)
« Last Edit: 21/05/2005 11:49:56 by rosy »
 

Offline chimera

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Re: Science vs. Religion
« Reply #63 on: 21/05/2005 12:47:04 »
That's the spirit. It is the official formula tho, not googles or HP's... r = 2GM/c^2.

here's the different ones for the accretion disk:
http://scienceworld.wolfram.com/physics/AccretionDisk.html

Also M is taken here as 1,9891 and is mostly given as 1,989

http://en.wikipedia.org/wiki/Solar_mass

so yes, it depends on what you toss in, and you might as well cut off the last few million kilometers. If you look carefully at that table you used btw, and scroll to the mass estimates for the solar system, you'll see that the bigger the mass, the more confident the estimate.

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Offline rosy

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Re: Science vs. Religion
« Reply #64 on: 21/05/2005 12:53:47 »
;) Sorry... I'm not questioning that it's the official (and *presumably* most rigorously tested) formula!
All I meant was that the last few sig figs were pretty much meaningless (except possibly for misleading the unwary as to how accurately it's currently possible to measure this stuff).
 

Offline chimera

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Re: Science vs. Religion
« Reply #65 on: 21/05/2005 13:23:59 »
Good point. It's only the official, surviving one in a sense, though. There have been others, slightly different, and rejected for different reasons. And testing, ah, testing. Now there's a good point. :D

Also all those nice round rough estimates (1000 billion solar masses, why not 956), the fact some of these objects are hundreds of millions of lightyears away and we are roughly estimating all those 'facts' based on observations of disturbances of much greater regions, and it is obvious that this kind of precision would not get you to the moon and back.

But people eat it like pie, and what's worse, they NEED that kind of semi-certainty, as if it made some kind of a difference.

(Even if my calculation about comparative size at a lighyear was trillions of times off, say the thing would be as big as a pea at one lightyear, would it make any difference? Not much in this case, for all practical purposes, but next time as for my calculation, too. ;)

Even scientists fall for it. Their need to appear so confident and infinitely precise is just filling in a niche, and of course they oblige. They can fulfill the same kind of psychological need for *reassurance* in our knowledge as priests do, and not only purely in our *knowledge*.

Therefore scientists should always be aware of the important difference, and Joe and Jane Public a lot less demure in his or her questioning.

added:

an example of such an article that I hope people will now read differently than before:

http://www.obspm.fr/messier/more/m087_hst.html

The living are the dead on holiday.  -- Maurice de Maeterlinck (1862-1949)
« Last Edit: 21/05/2005 13:44:19 by chimera »
 

Offline daveshorts

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Re: Science vs. Religion
« Reply #66 on: 21/05/2005 13:35:47 »
I think Rosy is making a far more fundamental point, which was drummed into me in Physics A-level and during my degree...
"If you put rubbish into a formula you get rubbish out" so if you are putting figures in that are +/- 30%, the answer will be (depending on the exact formula) +/- 30%, so quoting the answer to .00000001% is pointless and very misleading.
 

Offline chimera

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Re: Science vs. Religion
« Reply #67 on: 21/05/2005 13:49:20 »
Mmm. Where'd you get that 30% from? My calculations were deceptively precise, but not off by more than a relative whisker, certainly not that.

Calling an object 'solar system sized', or pretending that it is any kind of exact measure, now that's misleading. What kind of definition is that?

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Offline daveshorts

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Re: Science vs. Religion
« Reply #68 on: 21/05/2005 14:06:47 »
I was talking in more general terms, but you are picking an arbitrary mass of about 1000 billion solar masses surely it is not meaningful to quote the answer to more than 1-2 significant figures?

I am not saying that there is anything wrong with your calculation, just that you are quoting the answer to a ridiculous accuracy... possibly a bit picky but you did start it ;)
 

Offline chimera

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Re: Science vs. Religion
« Reply #69 on: 21/05/2005 14:49:13 »
The difference in G is a max of 30 per 10,000, that's the closest I can think of. Anyway.

Using more than 2 decimal places in these matters is not what it's about, though. Remember the name of the thread? It's about gullibility more than anything else.

I didn't pick the number of 1 billion
  • solar masses, or 3 billion. Those are numbers used in documents by scientists. Why these? Probably because it is a nice round percent of the weigth of your average galaxy, and gravitational disturbances are more likely to be measured in those terms. 'We have a 3-percent mass disturbance here', like.


Fact remains, that ANY direct mention of such sizes, has very little to do with direct observation, but are derived via yet another calculation/guesstimate. Fact number two remains, tho: the sizes mentioned are not only questionable, but if they are anything, they are too big. In that sense the calculations are very valid and not misleading.

Which leads us back to my original proposition that dogma has its counterpart in pulp science, where the need for reassurance wins on factuality/inquisitiveness by a knock-out.


[* edit late typo - that was what the whole argument was about: you cannot have objects that need 1000 billion or 3000 billion, like a 1/2 - lightyear-big black hole - sorry for the late edit but I had to leave in a rush and realised it only later, I'll stick to exponential notation in future, sigh.]

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« Last Edit: 21/05/2005 19:30:16 by chimera »
 

Offline chimera

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Re: Science vs. Religion
« Reply #70 on: 22/05/2005 11:29:21 »
quote:
Originally posted by daveshorts

I was talking in more general terms, but you are picking an arbitrary mass of about 1000 billion solar masses surely it is not meaningful to quote the answer to more than 1-2 significant figures?

I am not saying that there is anything wrong with your calculation, just that you are quoting the answer to a ridiculous accuracy... possibly a bit picky but you did start it ;)


Summarising:
Dave, with rosy's comments calculated in, there would be only a marginal difference between my answers and the ones that would be used in an official paper, where cutting off at a certain decimal is more of an editorial function, or adding a +/- uncertainty to avoid any nitpickery.

Again, because of the numbers used, this would be millions of kilometers different in reality, but as for the calculation still be more in the order of 1/30th of a procent, than 30.

Also don't forget that the calculation is done in kilometers, before converting to lightyears. That's only done in the end, of course.

As to your question about sizes of suspected accretion disks:

"This 130 light-year diameter disk encircles a suspected black hole which may be one billion times the mass of our Sun."

http://bustard.phys.nd.edu/Phys171/lectures/smbh.html

so you can work out how large the object would have to be according to the accretion disk formula, and see for yourself it cannot correspond to an object weighing only 10^9 kg, especially not it if the objects's lightyears across.
 

Offline daveshorts

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Re: Science vs. Religion
« Reply #71 on: 22/05/2005 12:06:00 »
We are not critising your calculation, just how accurate it is worth quoting the answer. 30% as I said earlier was just a number picked out of the air with no particular relevance to your calculation to make a point. However if you are going to be awkward I will:

You may be correct if you actually meant to calculate the schwartzchild radius of a black hole of mass 1billion +/- 1 solar mass - but I don't think there is any point unless you are considering building the black hole. I think what you meant was about 1 billion solar masses - in which case the implied precision is 1-2 sig fig, so although you may be technically correct, there is still no point in quoting so much precision.

If you read http://bustard.phys.nd.edu/Phys171/lectures/smbh.html carefully the 130 light year thing may be feeding into a smaller inner acretian disk - I would guess that the outer disk is not in hydrostatic equilibrium, and therefore doesn't fit with your equation. It is therefore not stable but I don't see why there should be a maximum size of a cloud of gas and dust that is gently falling into a black hole- I am not sure what the exact semantics are, but I would guess the problem is in the definition of accretian disk rather than the physics.
 

Offline chimera

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Re: Science vs. Religion
« Reply #72 on: 22/05/2005 12:21:13 »
I'm sorry, but that's not the same kind of caveat's I'm reading from those texts, but instead only roaring enthusiasm - make that cock-certainty - for something that MUST be a black hole, cannot be something else, whatever the slight (!) differences with observational data.

So, suddenly its not strictly 'allowed' to use a math formula given by physicists as their best effort at calculating mass and size of a black hole, because we have to make allowances for all kinds of uncertainties and possible varations on a theme.

OK, fine by me, as long as we all know our place, I guess.

Funny how if someone postulates something more common than a black hole, like a variation on a neutron star, all hands are called on deck to burn heretics using the same formulas, in essence. Did you know the word heretic originally simply meant 'doubter', btw?

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Offline daveshorts

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Re: Science vs. Religion
« Reply #73 on: 22/05/2005 16:33:39 »
relax, I am not complaining about your calculation just making a picky, but quite fundamental, point about how you should present the result...  

ps can I please not be on board the ship that burns heritics aboard - I find building fires somewhere less flamable ob balance a little better ;)
 

Offline chimera

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Re: Science vs. Religion
« Reply #74 on: 22/05/2005 18:37:35 »
There's nothing fundamental in blowing up a supposed error by a order of 4, it's just erroneous, and your tenacity about it is honestly getting a bit tedious by now. If you did not mean to say it, or meant anything else, why react at all? Could have saved yourself the whole thing.

I really wish you were so tenacious about seeing the the importance of a difference between observation and theory when it concerns a difference of an order of 3, a 1000 times,  as observed, instead of going on about something maybe differing at 4 digits behind the comma.

One thing they even acknowledged in the bible, something with a mote in the other's eye  while missing out on the beam in your own.

This is not some political debate where it's your taken position that decides your acceptance of facts and figures or negative polls or not, it's science. Dammit.

Oh, I like to do my heretic-burning preferably aboard oil-tankers filled with the best high-octane stuff, btw. And then take the chopper out. What you take me for, barbaric?  :)

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Re: Science vs. Religion
« Reply #74 on: 22/05/2005 18:37:35 »

 

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