Since, we can only see "the observable universe", how do we know how much mass is beyond our view? If we don't know what is there, why do we think there is missing mass?
Black holes ruled out as universe’s missing dark matter
41–50 of 130 posts
Re: Black holes ruled out as universe’s missing dark matter
#42Earlier quoted context omitted.
Let's change this a little bit. We have observed specific phenomena but not that which created such phenomena. As far as "Black Holes" as per theoretical descriptions are concerned, they cannot exist in a finite time universe as far as we (the observers) are concerned. The theoretical models used all have as a basic assumption that increasing gravity (whatever that may be) will cause a slow down in time as observed a…
Black holes may not form true singularities in any finite amount of time, but event horizons that are indistinguishable from the outside can be formed.
It is the event horizon that never forms. The problem that is never dealt with is that when the density of material goes up, gravity goes up, time dilation throughout all the affected material increases. From our perspective, everything throughout the affected material and region slows down - that includes any compression effects to increase the density. There is no opportunity for the effects to generate an event horizon to occur in finite time. If the event horizon cannot form then you can forget about any singularity ever forming.
It is just assumed that the event horizon and all of the associated effects will occur in finite time. It is taken as a given that "Black Holes" exist without questioning all of the assumptions being made regarding these entities. When anyone questions this view, the amount of disdain and ridicule expressed to them is just ridiculous.
Those expressing such disdain and ridicule do not even attempt to answer the questions - it is immediate ad hominen attack. This is the attitude that encouraged me to investigate the matter further and the conclusion is that those experts who support the idea of "Black Holes" have a mindset of "we are the authority and who are you to question us". They are so blinded by there own brilliance that they cannot see the forest because they have their noses up against the ground. It is a sorry state of affairs when dogma gets in the road of investigation.
There are no stupid questions, ever. However, there are many non-answers given.
Re: Black holes ruled out as universe’s missing dark matter
#43Earlier quoted context omitted.
Let's change this a little bit. We have observed specific phenomena but not that which created such phenomena. As far as "Black Holes" as per theoretical descriptions are concerned, they cannot exist in a finite time universe as far as we (the observers) are concerned. The theoretical models used all have as a basic assumption that increasing gravity (whatever that may be) will cause a slow down in time as observed a…
We have observed matter falling into a black hole. We've watched "hot spots" in orbit of a black hole in the accretion disk shine their light at us as they orbited the black hole. We've watched as the orbit got tighter and tighter and the light was dimmed by gravitational red shifting, then we've watched the light blink out and disappear as the blob of gas fell below the event horizon. The evidence for the existence…
Then there's this video ESO's Very Large Telescope shot[0], of stars orbiting something that's a) very massive, and b) invisible. Does that constitute a direct observation of a black hole?
--
Re: Black holes ruled out as universe’s missing dark matter
#44Earlier quoted context omitted.
Let's change this a little bit. We have observed specific phenomena but not that which created such phenomena. As far as "Black Holes" as per theoretical descriptions are concerned, they cannot exist in a finite time universe as far as we (the observers) are concerned. The theoretical models used all have as a basic assumption that increasing gravity (whatever that may be) will cause a slow down in time as observed a…
We have observed matter falling into a black hole. We've watched "hot spots" in orbit of a black hole in the accretion disk shine their light at us as they orbited the black hole. We've watched as the orbit got tighter and tighter and the light was dimmed by gravitational red shifting, then we've watched the light blink out and disappear as the blob of gas fell below the event horizon. The evidence for the existence…
No. Incorrect. Wildly inaccurate.
We have made certain observations that are assumed to be the result of matter falling into a "Black Hole". We do not have any observations that show us this as a fact. Read the observational material very carefully.
Go back over the last few decades and see how many times it is declared "we have seen x for the first time", where x is the is the same entity each time, in this particlualr case "Black Holes".
Men (women, children) want to believe that they have a certain handle on the truth and reality. What is very unpleasant to most is not having that certainty. This applies to all people across the board and even more so to those whose expertise is dependent on their being right. Many scientists are in this category.
It is often difficult to sit in the place of recognising that we just don't know. We have some ideas which, on the evidence, give a handle to investigate further, but we should understand that our understanding can be turned on its head.
The evidence for the existence of something is there, yes. But, is it a "Black Hole" of the theory presented, hmmm, that is unknown and for the time being, unknowable. As we cannot get out there and actually do the appropriate experiments to test this. We can only do remote observations and these can be easily misinterpreted.
>>Nobody except cranks or extreme contrarians seriously disputes the theory these days.
The problem here with this view is that it has been "cranks" and "extreme contrarians" who have brought about the biggest changes in science. There are Nobel Prize winners amongst them. All views about the nature of our universe should have those who dispute it. This should spur on our investigations into the nature of the universe. If we are unable to handle someone disputing our models and theories of the universe, then what are we doing? We are not serious about expanding our knowledge, we are serious about our reputations and being right.
The biggest problem for science today is that people don't trust it because it keeps getting things wrong, yet all the while saying that it is the only source of truth.
Science is one of a group of tools we can and should use to investigate the universe around. It has its limitations as does all the other tools we have and we need to recognise that though this tool is helpful in understanding, it is not the tool that gives us the truth.
Re: Black holes ruled out as universe’s missing dark matter
#45Since, we can only see "the observable universe", how do we know how much mass is beyond our view? If we don't know what is there, why do we think there is missing mass?
When we measure the amount of mass in a galaxy, we see that the galaxy's rotation is way faster than the amount of mass would indicate.
Re: Black holes ruled out as universe’s missing dark matter
#46This spawned a question for me that seems like it must be nonsensical but I don’t know the answer. Why did the Big Bang not just produce a Big Hole? IOW, if all the current mass of the universe was in a small volume wouldn’t it have promptly created a black hole? I’m assuming the answer has something to do with mass not actually existing in its current form until the universe expanded enough. However I don’t have any…
The early universe was ridiculously homogeneous. We can infer this with reasonable certainty from the extreme homogeneity of the CMB and from the gravitational instability of density fluctuations: as you expect, they attract more mass and accrete to form stars and galaxies. So if you start from the universe as it looks now and run time backwards, you get ridiculous homogeneity at the bang. And that's why you didn't g…
So, are we assuming the universe is infinite? Otherwise there'd be a border to that.
Re: Black holes ruled out as universe’s missing dark matter
#47Earlier quoted context omitted.
The early universe was ridiculously homogeneous. We can infer this with reasonable certainty from the extreme homogeneity of the CMB and from the gravitational instability of density fluctuations: as you expect, they attract more mass and accrete to form stars and galaxies. So if you start from the universe as it looks now and run time backwards, you get ridiculous homogeneity at the bang. And that's why you didn't g…
So, are we assuming the universe is infinite? Otherwise there'd be a border to that.
The universe can be finite without a border. Think about living on the surface of a sphere or a torus (finite, no edge), as opposed to living on a sheet of paper
Re: Black holes ruled out as universe’s missing dark matter
#48Earlier quoted context omitted.
I'm absolutely not an expert, but I believe there wasn't any mass at first; it was all energy. It had to slow down to become mass, at which point it was spread out enough. Or something along those lines. Another possibility is that black holes are places where lots of mass accumulates in the same place in space, while the big bang was a rapid expansion of space itself. Even if there was enough mass in one spot to be…
> I believe there wasn't any mass at first; it was all energy. It had to slow down to become mass This is partly true. During inflation, the universe was vacuum; all of the energy was in the "false vacuum" state of whatever field caused inflation (it's usually called the "inflaton" field, which IMO is a very confusing name). When inflation ended, all of that energy got transferred to the Standard Model fields, formin…
But did it end?
Re: Black holes ruled out as universe’s missing dark matter
#49Earlier quoted context omitted.
"Mass" is just another name for "rest-energy". A single photon cannot have mass because it has zero energy in the reference frame where it is at rest (zero net momentum). But a pair of non-parallel photons can have rest-mass, and indeed the mass of the photons inside a star is considerable, for example.
> "Mass" is just another name for "rest-energy". Not if you're talking about what the source of gravity (spacetime curvature) is. Massless particles still have energy and still cause spacetime curvature.
The "source" of gravity is the stress-energy tensor. "Mass" (rest-energy) is a simplification that is useful for approximations and conceptualizations.
Re: Black holes ruled out as universe’s missing dark matter
#50Earlier quoted context omitted.
We have observed matter falling into a black hole. We've watched "hot spots" in orbit of a black hole in the accretion disk shine their light at us as they orbited the black hole. We've watched as the orbit got tighter and tighter and the light was dimmed by gravitational red shifting, then we've watched the light blink out and disappear as the blob of gas fell below the event horizon. The evidence for the existence…
No. Incorrect. Wildly inaccurate. We have made certain observations that are assumed to be the result of matter falling into a "Black Hole". We do not have any observations that show us this as a fact. Read the observational material very carefully. Go back over the last few decades and see how many times it is declared "we have seen x for the first time", where x is the is the same entity each time, in this particlu…
If you're trying to get me to take you seriously you've failed. Do you think that condescension mingled with evidence free assertions are the way to support an argument? Is that science in your eyes?