APOD: Inside the Coma Cluster of Galaxies (2015 Mar 01)

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APOD: Inside the Coma Cluster of Galaxies (2015 Mar 01)

Post by APOD Robot » Sun Mar 01, 2015 5:05 am

Image Inside the Coma Cluster of Galaxies

Explanation: Almost every object in the above photograph is a galaxy. The Coma Cluster of Galaxies pictured above is one of the densest clusters known - it contains thousands of galaxies. Each of these galaxies houses billions of stars - just as our own Milky Way Galaxy does. Although nearby when compared to most other clusters, light from the Coma Cluster still takes hundreds of millions of years to reach us. In fact, the Coma Cluster is so big it takes light millions of years just to go from one side to the other! The above mosaic of images of a small portion of Coma was taken in unprecedented detail in 2006 by the Hubble Space Telescope to investigate how galaxies in rich clusters form and evolve. Most galaxies in Coma and other clusters are ellipticals, although some imaged here are clearly spirals. The spiral galaxy on the upper left of the above image can also be found as one of the bluer galaxies on the upper left of this wider field image. In the background thousands of unrelated galaxies are visible far across the universe.

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Re: APOD: Inside the Coma Cluster of Galaxies (2015 Mar 01)

Post by geckzilla » Sun Mar 01, 2015 5:17 am

To me it looks like a good bunch of those bigger galaxies are neither spirals nor ellipticals but rather lenticulars.
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Re: APOD: Inside the Coma Cluster of Galaxies (2015 Mar 01)

Post by ta152h0 » Sun Mar 01, 2015 5:32 am

if we take Andromeda and the Milky way and lay them out to scale on this image, which two would be an accurate scale distance apart ?
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Re: APOD: Inside the Coma Cluster of Galaxies (2015 Mar 01)

Post by alter-ego » Sun Mar 01, 2015 6:10 am

ta152h0 wrote:if we take Andromeda and the Milky way and lay them out to scale on this image, which two would be an accurate scale distance apart ?
At the image scale, the Milky Way and Andromeda don't fit. Their separation ≈2,500,000 light years, about 25% larger than the image diagonal.
Coma Cluster Scale.JPG
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Re: APOD: Inside the Coma Cluster of Galaxies (2015 Mar 01)

Post by Ann » Sun Mar 01, 2015 6:40 am

Thanks, alter-ego!

That spiral galaxy, IC 4040, is interesting. How can it have held on to its gas supply and managed to turn into such recent and widespread star formation, when all the other galaxies are either completely yellow or mostly very yellow?

The wider field image of the Coma Cluster shows the spiral galaxy NGC 4911 in the lower left corner. NGC 4911, like IC 4040, is also quite vigorously forming new stars. But some distance away from NGC 4911 and IC 4040 is another galaxy, NGC 4921, that does look like a spiral caught in the death grip of a massive, star formation-quenching cluster. NGC 4921 is an anemic spiral.

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Re: APOD: Inside the Coma Cluster of Galaxies (2015 Mar 01)

Post by Dad is watching » Sun Mar 01, 2015 2:24 pm

Looking at this image, I was wondering if it would be possible to estimate the density/amount of inter-galactic material (gas, dust, etc) exists, on the average, throughout the entire universe based on perceived data? And given that information, how far could we possibly 'see' through it? Being a theoretical question, some conditions would have to be assumed that are otherwise not supported by our current knowledge; such as the age/size of the universe (infinite time and space) as we understand it. If there was another 'universe' out there, much older and beyond the edge of our 'universe', how far would it have to be away from us before we couldn't see it any more? I guess the units of measure would have to be something like 'universe radius/diameter' or something like that. Any ideas?

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Re: APOD: Inside the Coma Cluster of Galaxies (2015 Mar 01)

Post by BDanielMayfield » Sun Mar 01, 2015 3:39 pm

Dad is watching wrote:Looking at this image, I was wondering if it would be possible to estimate the density/amount of inter-galactic material (gas, dust, etc) exists, on the average, throughout the entire universe based on perceived data?
Yes, this has been done. One of the reasons that the distant galaxies appear redder than the large nearby galaxies is that we have to look through more inter-galactic material to see them.
And given that information, how far could we possibly 'see' through it? Being a theoretical question, some conditions would have to be assumed that are otherwise not supported by our current knowledge; such as the age/size of the universe (infinite time and space) as we understand it.
I don't have an answer to that question, but "our current knowledge" pegs the age of the universe at 13.8 billion years, which is much much less than an infinite timeline.

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Re: APOD: Inside the Coma Cluster of Galaxies (2015 Mar 01)

Post by Chris Peterson » Sun Mar 01, 2015 3:57 pm

Ann wrote:That spiral galaxy, IC 4040, is interesting. How can it have held on to its gas supply and managed to turn into such recent and widespread star formation, when all the other galaxies are either completely yellow or mostly very yellow?
As a rule, I don't think yellow, inactive galaxies have failed to "hold on" to their gas supply. These galaxies usually have plenty of hydrogen available for star formation. It's just too homogeneous. All you need is a bit of tidal interaction with another galaxy, a few nice supernovas to seed some dust, or the right kind of shock front along a spiral arm edge to get things rolling again. My understanding is that there's a lot of evidence that galaxies (especially those still the spiral stage) can cycle through periods of inactivity and periods of star formation.
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Re: APOD: Inside the Coma Cluster of Galaxies (2015 Mar 01)

Post by Ron-Astro Pharmacist » Sun Mar 01, 2015 4:00 pm

Images like this paint a picture of a universe that shows the vastly overwhelming state of increasing randomness. The only entities proven to exist which are capable of decreasing entropy are people and other living organisms on our planet. Despite the size of our observable universe it seems the only hope to reverse the randomness is through interventions manipulating energy to, one day far in the future, bring it back to the way it all began.

Perhaps that’s the reason we are all here, perhaps not. But it does occur to me that nothing beside life is likely ever to reverse even a gravitationally bound but expanding universe. Maybe the anthropic principle is alive, well and capable of so much more than any of us could begin to imagine.
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Re: APOD: Inside the Coma Cluster of Galaxies (2015 Mar 01)

Post by Chris Peterson » Sun Mar 01, 2015 4:10 pm

Dad is watching wrote:Looking at this image, I was wondering if it would be possible to estimate the density/amount of inter-galactic material (gas, dust, etc) exists, on the average, throughout the entire universe based on perceived data?
Yes. The baryonic density of the Universe is a key parameter in cosmology models. It is estimated to be on the order of 10-31 grams per cubic centimeter, or a few baryons per cubic meter. This is very, very small. Indeed, it is so small that the Universe is highly transparent. We can see all the way to the edge of the visible Universe to the point where it became transparent- those are the photons that we detect as the cosmic microwave background. Very few are absorbed, and the amount of scatter (reddening) is extremely small, as well.

How far we can see is limited by the point at which the Universe is receding from us at greater than c, not by any intervening material.
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Re: APOD: Inside the Coma Cluster of Galaxies (2015 Mar 01)

Post by Ann » Sun Mar 01, 2015 4:26 pm

Chris Peterson wrote:
Ann wrote:That spiral galaxy, IC 4040, is interesting. How can it have held on to its gas supply and managed to turn into such recent and widespread star formation, when all the other galaxies are either completely yellow or mostly very yellow?
As a rule, I don't think yellow, inactive galaxies have failed to "hold on" to their gas supply. These galaxies usually have plenty of hydrogen available for star formation. It's just too homogeneous. All you need is a bit of tidal interaction with another galaxy, a few nice supernovas to seed some dust, or the right kind of shock front along a spiral arm edge to get things rolling again. My understanding is that there's a lot of evidence that galaxies (especially those still the spiral stage) can cycle through periods of inactivity and periods of star formation.
Maybe you are right, Chris, but maybe not.

Take a look at this splendid picture by Adam Block of the Perseus Cluster of galaxies. At top right you can see a pair of yellow galaxies involved in a "dry merger", a merger or interaction of two yellow galaxies that doesn't result in any significant star formation. Other yellow galaxies in the cluster are also very close to one another and almost certainly interacting, and they are surrounded by large, faint yellow halos. But we can see no sign of any significant star formation.

Also, in the widefield image of the Coma Cluster we see many galaxies that are very close to one another. Certainly they must be interacting, but we see no obvious signs of recent star formation in these galaxies.

I agree that elliptical galaxies contain a lot of gas. But they have lost their ability to pile up that gas in large, dense, cold molecular clouds. That is why they can't form new stars.

I believe that isolated small galaxies may undergo a burst of star formation and then "settle down" as dwarf ellipticals. But these small galaxies almost certainly don't contain a supermassive black hole. If they suddenly interact with another galaxy again, they may well undergo significant renewed star formation. There are signs that the Large Magellanic Cloud may have undergone "quiet" periods between bursts of star formation, judged by the age of the clusters in this galaxy. See "The Gaalxies of the Local Group" by Sidney van den Bergh, Cambridge Astrophysics Series 35, © Cambridge University Press 2000. See the chapter about The Large Magellanic Cloud, part 6.7, Evolutionary history of the Large Cloud.

Have you read that large galaxies containing supermassive black hole may still suddenly experience bursts of star formation? And have you read that "red and dead" galaxies in large clusters may suddenly start forming significant numbers of stars again? If so, where have you read it?

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Re: APOD: Inside the Coma Cluster of Galaxies (2015 Mar 01)

Post by ta152h0 » Sun Mar 01, 2015 4:28 pm

reminder of how small we are and how we can create giant problems
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Re: APOD: Inside the Coma Cluster of Galaxies (2015 Mar 01)

Post by Chris Peterson » Sun Mar 01, 2015 4:31 pm

Ann wrote:I agree that elliptical galaxies contain a lot of gas. But they have lost their ability to gather significant portions of that gas in large, dense, cold molecular clouds. That is why they can't form new stars.
Elliptical galaxies seem more stable than spirals, being intrinsically more homogenous. The active galaxy in this group is a spiral, however. So it's not too surprising to see it as active in the midst of a bunch of ellipticals. Nevertheless, I think it is best to view the inactive galaxies here as dormant, rather than extinct. Any could probably have new star formation triggered by the right kind of interaction.
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Re: APOD: Inside the Coma Cluster of Galaxies (2015 Mar 01)

Post by Ann » Sun Mar 01, 2015 5:33 pm

Chris Peterson wrote:
Ann wrote:I agree that elliptical galaxies contain a lot of gas. But they have lost their ability to gather significant portions of that gas in large, dense, cold molecular clouds. That is why they can't form new stars.
Elliptical galaxies seem more stable than spirals, being intrinsically more homogenous. The active galaxy in this group is a spiral, however. So it's not too surprising to see it as active in the midst of a bunch of ellipticals. Nevertheless, I think it is best to view the inactive galaxies here as dormant, rather than extinct. Any could probably have new star formation triggered by the right kind of interaction.
IC 4040 is on the outskirts of the Coma cluster, and it may in fact have been incorporated there moderately recently. Admittedly we see no signs of a "violent infall" which will strip galaxies of their gas, so IC 4040 must have approached the Coma Cluster more gently.

Still, it is obvious from the pictures of almost all large galaxy clusters except the Hercules Cluster that ellipticals dominate very strongly, and that the very frequent interactions with other galaxies in these clusters don't generally generate significant numbers of new stars.

I found this discussion on the difference between the central parts of galaxy clusters and the outer parts of them, but I don't think it is the most convincing discussion I have read. Nevertheless, I think it backs up my belief that starforming galaxies will be far more common in the outskirts of galaxy clusters than in the center of them. Clearly the Hercules Cluster does show a lot of starforming galaxies even in the apparent center of it, but I think the Hercules Cluster is rather atypical. It may be a particularly young cluster, or maybe two different clusters that have recently merged.

Chris, what makes you think that 1) large galaxies whose star formation has "dried up" are likely to experience enhanced star formation again and
2) cluster galaxies dominated by old stars are likely to produce significant amounts of new stars again, given the right sort of interaction?

Do you have any literature to back you up, or are you going with your gut feeling?

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Re: APOD: Inside the Coma Cluster of Galaxies (2015 Mar 01)

Post by Chris Peterson » Sun Mar 01, 2015 5:52 pm

Ann wrote:Chris, what makes you think that 1) large galaxies whose star formation has "dried up" are likely to experience enhanced star formation again and
2) cluster galaxies dominated by old stars are likely to produce significant amounts of new stars again, given the right sort of interaction?

Do you have any literature to back you up, or are you going with your gut feeling?
Just stuff I've read. No references handy. Not just gut feeling, though. And it makes sense- there's still plenty of free hydrogen, and in some cases dust. For star formation, you simply need to create shocks. Why wouldn't we expect something like a merger between two of these dormant galaxies to result in regions of star formation? I think it would be harder to explain things if that didn't happen.
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the age of blue live galaxies

Post by isblech » Sun Mar 01, 2015 7:33 pm

It is clear that the blue spiral galaxy is (as most of spiral, live galaxies) a young one, may be
even younger then our Milky Way, means that it is about a half of the age of the elliptical
'dry' galaxies, but its bulge and global clasters are of the same age as the elliptical
galaxies around, as it is in our Milky Way also.

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Re: APOD: Inside the Coma Cluster of Galaxies (2015 Mar 01)

Post by Ann » Mon Mar 02, 2015 12:29 am

I disagree with you, Chris. First of all I've never heard the expression "dormant galaxy". I made a quick search, but nothing turned up on the first page except dormant black holes in galaxies.

It is a known fact that star formation in the universe is on the decline.
http://www.space.com/18370-universe-sta ... cline.html wrote:

The rate of star formation in the universe has dropped to just 3 percent of its long-ago peak, and there's no end in sight to the decline, a new study finds.

A team of astronomers has determined that the rate of star birth peaked around 11 billion years ago, just 2.7 billion years after the Big Bang that created the universe. It has been dropping ever since, and the rate now stands at just just one-thirtieth its historic high, researchers said.

"You might say that the universe has been suffering from a long, serious 'crisis:' cosmic GDP output is now only 3 percent of what it used to be at the peak in star production," study lead author David Sobral, of the University of Leiden in the Netherlands, said in a statement.
Not only is the overall cosmic star formation rate on the decline, but astronomers have also found a likely culprit in the quenching of star formation in galaxies, namely their central black holes:
https://public.nrao.edu/news/pressrelea ... black-hole wrote:

High-energy jets powered by supermassive black holes can blast away a galaxy’s star-forming fuel, resulting in so-called "red and dead" galaxies: those brimming with ancient red stars yet containing little or no hydrogen gas to create new ones.

Now astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have discovered that black holes don’t have to be nearly so powerful to shut down star formation. By observing the dust and gas at the center of NGC 1266, a nearby lenticular galaxy with a relatively modest central black hole, the astronomers have detected a “perfect storm” of turbulence that is squelching star formation in a region that would otherwise be an ideal star factory.

This turbulence is stirred up by jets from the galaxy’s central black hole slamming into an incredibly dense envelope of gas. This dense region, which may be the result of a recent merger with another smaller galaxy, blocks nearly 98 percent of material propelled by the jets from escaping the galactic center.

“Like an unstoppable force meeting an immovable object, the particles in these jets meet so much resistance when they hit the surrounding dense gas that they are almost completely stopped in their tracks,” said Katherine Alatalo, an astronomer with the California Institute of Technology in Pasadena and lead author on a paper published in the Astrophysical Journal. This energetic collision produces powerful turbulence in the surrounding gas, disrupting the first critical stage of star formation. “So what we see is the most intense suppression of star formation ever observed,” noted Alatalo.
Because of the cosmic decline in star formation, mergers in the present universe don't always produce star formation.
S Kaviraj, J Devriendt, Y Dubois, A Slyz, C Welker, C Pichon, S Peirani, DL Borgne wrote:

While almost all major mergers at z>3 are 'blue' (i.e. have significant associated star formation), the proportion of 'red' mergers increases rapidly at z<2, with most merging systems at z~1.5 producing remnants that are red in rest-frame UV-optical colours.
I have searched, quite unsuccessfully, for articles about the low rate of star formation in galactic clusters. But even if I haven't found any articles about it, color pictures of almost all massive galaxy clusters show that the members of these clusters are almost all yellow ellipticals and lenticular galaxies. And if jets from supermassive black holes can disrupt and quench star formation in individual galaxies, it makes good sense that powerful jets can disturb and disrupt star formation in the crowded environment of massive clusters of galaxies.

Given this kind of star formation decline, I don't think we can just assume that vigorous star formation is quite likely to switch on again in large yellow galaxies with supermassive black holes, or in most yellow galaxies in massive clusters.

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Re: APOD: Inside the Coma Cluster of Galaxies (2015 Mar 01)

Post by Chris Peterson » Mon Mar 02, 2015 5:13 am

Ann wrote:I disagree with you, Chris.
Fine. But I don't find that anything you've added here contradicts what I've suggested.
Given this kind of star formation decline, I don't think we can just assume that vigorous star formation is quite likely to switch on again in large yellow galaxies with supermassive black holes, or in most yellow galaxies in massive clusters.
What I've suggested is entirely consistent with a decline in star formation. And we have examples of star formation occurring in colliding elliptical galaxies. I agree that star formation isn't going to spontaneously turn on in these evolved galaxies. That's very different from suggesting it wouldn't happen with a strong interaction of some kind to seed discontinuities. The raw materials are still there.
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Re: APOD: Inside the Coma Cluster of Galaxies (2015 Mar 01)

Post by Ann » Mon Mar 02, 2015 7:09 am

Chris wrote:
And we have examples of star formation occurring in colliding elliptical galaxies.
Maybe. It doesn't happen, I think, if two elliptical galaxies collide with each other, unless perhaps if they are small elliptical galaxies with large reservoirs of gas and small central black holes.

We have a spectacular example of an elliptical galaxy colliding with something and creating a burst of new stars, while remaining essentially an elliptical galaxy. But this is a very unusual case, particularly in view of the fact that the galaxy, NGC 1275, is in the thick of the Perseus Cluster of galaxies. Centaurus A is doing something slightly similar, although this galaxy is not located in a cluster, certainly not in a supermassive cluster. And again, this is an unusual case.

Maybe giant elliptical galaxy M60 will form stars when it collides with its small spiral satellite galaxy, NGC 4647. But so far, even though NGC 4647 is clearly approaching, we see no signs of new stars in M60.

But yes, a collision with a gas-rich spiral might produce new stars in an elliptical galaxy. Nevertheless, it is an unusual occurrence.

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Re: APOD: Inside the Coma Cluster of Galaxies (2015 Mar 01)

Post by geckzilla » Mon Mar 02, 2015 7:12 am

Chris Peterson wrote:The raw materials are still there.
What do you mean by this, actually? I've seen small, diffuse patches of star formation in ellipticals which have very obviously gone through a recent merger but nothing like one might expect if there were somehow a lot of raw materials out there to work with. Maybe you just mean there's some and that star formation is still possible but from the word "dormant" it sounds like you mean there is still a lot of raw material and that it's possible to reignite a large scale burst in star formation.
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Re: APOD: Inside the Coma Cluster of Galaxies (2015 Mar 01)

Post by Chris Peterson » Mon Mar 02, 2015 2:51 pm

geckzilla wrote:
Chris Peterson wrote:The raw materials are still there.
What do you mean by this, actually? I've seen small, diffuse patches of star formation in ellipticals which have very obviously gone through a recent merger but nothing like one might expect if there were somehow a lot of raw materials out there to work with. Maybe you just mean there's some and that star formation is still possible but from the word "dormant" it sounds like you mean there is still a lot of raw material and that it's possible to reignite a large scale burst in star formation.
I just mean that there is still free hydrogen present (it shows up in radio images). It is too diffuse to coalesce into star forming regions, particularly without the catalyst of dust. But as long as there's hydrogen, any mechanism that can create turbulence or shock fronts is likely to lead to star formation. A galactic collision is the obvious possibility, but there are probably others.
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Re: APOD: Inside the Coma Cluster of Galaxies (2015 Mar 01)

Post by Ann » Mon Mar 02, 2015 4:45 pm

Chris wrote:

I just mean that there is still free hydrogen present (it shows up in radio images). It is too diffuse to coalesce into star forming regions, particularly without the catalyst of dust. But as long as there's hydrogen, any mechanism that can create turbulence or shock fronts is likely to lead to star formation. A galactic collision is the obvious possibility, but there are probably others.
Maybe the elliptical galaxies are suffering from a sort of "heat death" or a very high degree of entropy. It is generally agreed upon that if the universe keeps accelerating, all matter that it contains will eventually become so smoothly distributed that it won't be able to form any important new structures, and it won't be able to generate any new energy.

Similarly, the gas in elliptical galaxies seems to be extremely smoothly distributed. Collisions seem to do nothing to create the kind of shock fronts that can generate new star formation in their thin, smooth broths of gas. Yes, I do remember (although I'm too lazy to search for it now) that some star formation takes place in most elliptical galaxies, which means that some compression of the gas is possible. But we are talking about minuscule amounts.

Like I said, collisions seem to do nothing to push the gas in ellipticals into star forming mode. That's why so very many galaxies in almost all massive clusters are so relentlessly yellow. What we do see in galaxy clusters is spirals being destroyed by ram pressure, not ellipticals blooming into star factories.

By the way, check out this soon-to-be-a-collision between giant elliptical M60 and small spiral galaxy NGC 4647. Adam Block's splendid pictures shows the huge, faint yellow halo of M60. But despite the approach of NGC 4647, the halo of M60 seems completely smooth and undisturbed.

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Re: APOD: Inside the Coma Cluster of Galaxies (2015 Mar 01)

Post by Ron-Astro Pharmacist » Mon Mar 02, 2015 8:02 pm

Ron-Astro Pharmacist wrote:Images like this paint a picture of a universe that shows the vastly overwhelming state of increasing randomness. The only entities proven to exist which are capable of decreasing entropy are people and other living organisms on our planet. Despite the size of our observable universe it seems the only hope to reverse the randomness is through interventions manipulating energy to, one day far in the future, bring it back to the way it all began.

Perhaps that’s the reason we are all here, perhaps not. But it does occur to me that nothing beside life is likely ever to reverse even a gravitationally bound but expanding universe. Maybe the anthropic principle is alive, well and capable of so much more than any of us could begin to imagine.
I was trying for an example of type of an Ontological argument with this statement. If anyone could find a way to meld science and religion – I would hope our world would be better for it.

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

If there is a way to turn mass, volume and E=MC2 into something unitive, a "god" particle or a God – I might suspect it would really help our current state of events with a T.O.E. that might eventually lay both famous apples in our past to a united rest. Better to shoot for the stars than at each other in my opinion. :thumb_up:
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Re: APOD: Inside the Coma Cluster of Galaxies (2015 Mar 01)

Post by Chris Peterson » Mon Mar 02, 2015 8:38 pm

Ron-Astro Pharmacist wrote:I was trying for an example of type of an Ontological argument with this statement. If anyone could find a way to meld science and religion – I would hope our world would be better for it.

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

If there is a way to turn mass, volume and E=MC2 into something unitive, a "god" particle or a God – I might suspect it would really help our current state of events with a T.O.E. that might eventually lay both famous apples in our past to a united rest. Better to shoot for the stars than at each other in my opinion. :thumb_up:
Ontology. The ultimate mental masturbation. Jolly fun for pot-fueled college bull sessions, but utterly useless when it comes to reality.
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Re: APOD: Inside the Coma Cluster of Galaxies (2015 Mar 01)

Post by rstevenson » Mon Mar 02, 2015 9:58 pm

Ron-Astro Pharmacist wrote:... If anyone could find a way to meld science and religion – I would hope our world would be better for it.
Ron, that's like looking for a way to meld dentistry and tooth fairies. For children, it may be helpful in quelling their perfectly natural fear of drilling for cavities, but it's not the way forward if you're looking for an increased understanding of dental health and well-being.

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