Dark Matter Black Holes?

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Dark Matter Black Holes?

Postby markstar » Wed Jul 22, 2015 1:27 pm

On the basis that Dark Matter exhibits the property of mass is there a theoretical possibility that dark matter could therefore ultimately form a Singularity and if so how might this present itself?

Thanks
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Re: Dark Matter Black Holes?

Postby david48 » Mon Aug 10, 2015 7:21 pm

markstar wrote:On the basis that Dark Matter exhibits the property of mass is there a theoretical possibility that dark matter could therefore ultimately form a Singularity and if so how might this present itself?

Thanks


Shouldn't we be intensely sceptical that there's any such thing as "Dark Matter". Doesn't it sound like something invented as an excuse for not being able to account for observations?

However, if it did exist, and had mass, this would presumably result in concentrations of Dark Matter.
Drawn together by the mutual gravitational attraction of the particles of DM.

I'm assuming that the DM particles are subject to gravitational force. (If not, they might just stay in the same position, or fly apart from each other, or loop round in triangles. And we'd be off in fairy-land)

So these DM particles would form a DM Black Hole. What would that be like?

I've no idea. It's hard enough to accept that ordinary-matter Black Holes and Singularities actually exist. I think that they don't, really. Aren't they just the figments of mathematicians' imaginations, accepted only because physicists can't yet travel into space to find the facts?
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Re: Dark Matter Black Holes?

Postby voyager » Tue Aug 11, 2015 10:51 am

Every observation thus far suggests they are frictionless and they likely annihilate upon collision, which suggests no DMBH could form.
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Re: Dark Matter Black Holes?

Postby david48 » Thu Aug 13, 2015 4:56 pm

voyager wrote:Every observation thus far suggests they are frictionless and they likely annihilate upon collision, which suggests no DMBH could form.

Or "Dark Matter" could be a figment of imagination.
These figments have come up often in the history of Science. And they were sometimes valuable. Like in the 17th century there was "Phlogiston", which explained combustion. Then in the 18th century there was "Caloric Fluid" which explained heat. In the 19th century we got the "Universal Aether", and in the 20th century "Land Bridges" which supposedly rose and fell between continents, before Plate Tectonics was found out.

All these theories, though now debunked, should not be despised. They were at least a good attempt at explaining things rationally.

But "Singularities" and "Dark Matter" seem so inherently implausible - from a rational viewpoint - that shouldn't we only regard them as nothing but mathematicians' imagination.
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Re: Dark Matter Black Holes?

Postby voyager » Fri Aug 14, 2015 12:19 am

david48 wrote:But "Singularities" and "Dark Matter" seem so inherently implausible - from a rational viewpoint - that shouldn't we only regard them as nothing but mathematicians' imagination.


I actually agree with you concerning singularities - they are most likely a failure of mathematics in dealing with infinities and are unlikely to exist in the real world. Dark Matter, on the other hand, is very plausible, in my opinion (we can't see radio waves with our eyes, but they exist, and no doubt people living centuries ago would think radio waves were pure fantasy). Of course, it may be that our understanding of gravity is at fault and therefore there is no need for Dark Matter, but we still have much to learn...
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Re: Dark Matter Black Holes?

Postby The Man with the Corrugated Iron Roof » Sun Aug 30, 2015 9:27 pm

Dark matter may well turn out to be like epicycles. As for singularities, I don't believe they can exist in reality either. I find the idea from String Theory that black holes are very very small (much smaller than an electron) more plausible.

However, if dark matter does exist, there is no reason why it cannot form black holes and no reason why it cannot fall into a black hole that was created from ordinary matter. On very small scales that black holes are, dark matter and ordinary matter particles would simply combine,
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Re: Dark Matter Black Holes?

Postby david48 » Wed Sep 02, 2015 3:32 pm

The Man with the Corrugated Iron Roof wrote:Dark matter may well turn out to be like epicycles. As for singularities, I don't believe they can exist in reality either. I find the idea from String Theory that black holes are very very small (much smaller than an electron) more plausible.

However, if dark matter does exist, there is no reason why it cannot form black holes and no reason why it cannot fall into a black hole that was created from ordinary matter. On very small scales that black holes are, dark matter and ordinary matter particles would simply combine,


Thanks Iron Roof for mentioning "epicycles". These were the most notorious example of mathematicians winning out against observation, for 2,000 years.

Observation showed, even to the Ancient Greeks, that the planets do not move in pure circular orbits. The orbits are actually elliptical.

Yet the mathematicians claimed that the orbits "ought to be" circular. So the mathematicians "corrected" observation, by theorising that the planets moved in a embedded series of circles, within circles, within circles - the "epicycles". With enough "epicycles", an approximation to the true elliptical orbit could be obtained.

With hindsight, this "epicycle" theory was illusory. But it dominated Astronomy for ages.

Perhaps "Singularities" are the modern equivalent
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