Astronomy

If a black hole has a mass of a universe what will be the volume of it?

If a black hole has a mass of a universe what will be the volume of it?

Will it suck the entire universe in? What will the black hole look like to us, assuming we do not immediately get sucked in?


According to measurements of the cosmic microwave background the universe is geometrically flat - which means that the mass/energy density of the universe is close to the "critical value" of $sim 10^{-26}$ kg/m$^{3}$.

The radius of the observable universe is 46.6 billion light years, so the mass/energy contained within it is equivalent to $3.6 imes 10^{54}$ kg.

The Schwarzschild radius of a black hole is $2GM/c^2$. If the mass/energy of the universe is spherically symmetric then its Schwarzschild radius is 560 billion light years and thus larger than the observable universe.

Note though that the Schwarzschild solution in General Relativity is static. The universe is definitely not static.


Before I answer this, it's important to correct a few assumptions:

(1) we can sit outside a universe-as-black-hole. This is impossible: since the universe includes everything that exists, then by definition we must be within it, so we can't look at it from the "outside".

(2) a black hole "sucks" matter into it. It doesn't, any more than a large star "sucks" matter. If the Sun somehow collapsed and became a black hole (it can't, this is just a thought experiment), all the planets would continue to orbit pretty much as usual, since the Sun's mass wouldn't have changed.

Now, to your core question:

If a black hole has a mass of a universe what will be the volume of it?

The Schwarzschild radius is the radius defining the event horizon of a Schwarzschild black hole. If we take the mass of the observable universe as roughly $10^{53}$ kg, then using the formula $$R=frac{2GM}{c^2}$$ the Schwarzschild radius of this mass is 15.7 billion light years [NB: by comparison, the comoving distance to the edge of the observable universe is about 46.6 billion light years]. The volume is then easily calculated as 1.6 x $10^{31}$ cubic light years or roughly $10^{79}$ $m^3$.

For comparison, this is less than 4% of the volume of the observable universe.


EDIT:

Wikipedia's "quick facts" on the observable universe give the mass as $10^{53}$ kg, but the body of the article contains the following qualification:

The mass of the observable Universe is often quoted as $10^{50}$ tonnes or $10^{53}$ kg. In this context, mass refers to ordinary matter and includes the interstellar medium (ISM) and the intergalactic medium (IGM). However, it excludes dark matter and dark energy. This quoted value for the mass of ordinary matter in the Universe can be estimated based on critical density. The calculations are for the observable universe only as the volume of the whole is unknown and may be infinite.

My calculations are based on the mass of ordinary matter in the observable universe, representing 4.9% of the total "mass/energy" derived from the observed critical density and volume. Rob's answer includes dark matter (26.8% of total mass/energy) and dark energy (68.3% of total mass/energy). Both answers are thought experiments, since it's not possible to have a black hole with the mass of the universe within our universe.

In a comment on the main question, userTLK makes an additional valid point that "the escape velocity at [a black hole's] event horizon is c. Dark energy might make that impossible. The vast distance and stretching of space and red-shifting of distant objects might make universe sized black holes impossible."


The Coevolution of Galaxies and Supermassive Black Holes: Insights from Surveys of the Contemporary Universe

We summarize what large surveys of the contemporary Universe have taught us about the physics and phenomenology of the processes that link the formation and evolution of galaxies with their central supermassive black holes. We present a picture in which the population of active galactic nuclei (AGNs) can be divided into two distinct populations. The radiative-mode AGNs are associated with black holes (BHs) that produce radiant energy powered by accretion at rates in excess of ∼1% of the Eddington limit. They are primarily associated with less massive BHs growing in high-density pseudobulges at a rate sufficient to produce the total mass budget in these BHs in ∼10 Gyr. The circumnuclear environment contains high-density cold gas and associated star formation. Major mergers are not the primary mechanism for transporting this gas inward secular processes appear dominant. Stellar feedback is generic in these objects, and strong AGN feedback is seen only in the most powerful AGNs. In jet-mode AGNs the bulk of energetic output takes the form of collimated outflows (jets). These AGNs are associated with the more massive BHs in more massive (classical) bulges and elliptical galaxies. Neither the accretion onto these BHs nor star formation in their host bulge is significant today. These AGNs are probably fueled by the accretion of slowly cooling hot gas that is limited by the feedback/heating provided by AGN radio sources. Surveys of the high-redshift Universe paint a similar picture. Noting that the volume-averaged ratio of star formation to BH growth has remained broadly constant over the past 10 Gyrs, we argue that the processes that linked the cosmic evolution of galaxies and BHs are still at play today.


If something is infinitely dense, must it not also be infinitely massive?

Nope. The singularity is a point where volume goes to zero, not where mass goes to infinity.

It is a point with zero volume, but which still holds mass, due to the extreme stretching of space by gravity. The density is $frac$, so we say that in the limit $volume ightarrow 0$, the density goes to infinity, but that doesn't mean mass goes to infinity.

The reason that the volume is zero rather than the mass is infinite is easy to see in an intuitive sense from the creation of a black hole. You might think of a volume of space with some mass which is compressed due to gravity. Normal matter is no longer compressible at a certain point due to Coulomb repulsion between atoms, but if the gravity is strong enough, you might get past that. You can continue compressing it infinitely (though you'll probably have to overcome some other force barriers along the way) - until it has zero volume. But it still contains mass! The mass can't just disappear through this process. The density is infinite, but the mass is still finite.

So everybody seems to fall into a logical trap here.

Black holes don't have infinite density at their singularity/center. This infinite density business is the physics way of saying that we don't know what is going on.

It gets even worse now that Higgs Boson/Field is apparently what gives particles their mass. If there are no particles in a Black Hole then what is there to interact with the Higgs Field to generate mass?

A black hole has an infinite density since its volume is zero, it is compressed to the very limit. So it also has infinite gravity, and sucks anything which is near it! Not everything there is!! Now above all when it sucks things it adds up to its mass, which remains finite and it always will, even if it did suck in the whole universe!! It's all for the formula: density in a black hole is mass divided by volume (0) so the density is infinite, not the mass. So thus a black hole has mass which is finite and will always be finite.

if it has infinite density, that would mean it has infinite gravity (or infinite space curvature in special relativity, which i believe in). so, it obviously doesn't have infinite density because that would suck the whole entire universe into itself. that would mean it would have to have an unmeasurably small amount of volume. and even if it did have infinite density, space curvature should be more powerful nearer to the singularity, but how can we add more to an infinite amount of gravity? if it had infinite density, its curvature should be equal everywhere, which is also impossible. What do you think of this theory?

I'm not going to claim any real knowledge on the topic, or most of what I bring up, so feel free to correct me for any extremely rash or impossible aspects, but here it goes.

A black hole to me, seems like it's just the epitomy of nothing. There's something, then general space, and then a black hole. It appears to me that something to nothing is relatively possible, as at one point nothing came to be something, however I feel that the universe itself wouldn't allow such a flaw, as the universe seems quite perfect in its design.

One theory I've stumbled upon is a theory that all atoms have a negative and positive form of which they can swap between. Kind of a matter and anti-matter deal, but all atoms experience this, and that we live in the positive.

This kind of interacts with the idea of a black hole, a massive explosion of something that created energy to powers beyond numbers we have words for (googlplex's), for a length of years we barely use the number for (billions). And it eventually explodes, and in the wake of such energy, a black hole is formed (If that's still what people believe). So a rediculous mass of positive energy goes out from a point in the universe, and in this point, it sucks in mass, everything, a perfect unescapable gravity pit.

Could it possibly be that after so much positive energy radiates from one point, it explodes, then begins sucking in all the positive energy that comes into it, to rebalance the rediculous amount of negative energy that would then be in the wake of such a thing?

I can kind of imagine it, more like an explosion under water (an implosion really). First it explodes, and then everything gets sucked in until it's at its natural point. Except this is on a massive (much bigger than any bomb we could ever make or imagine), yet scale so small (fills itself in to a sub-atomic level, if not to an electron level) it takes an unbelievably long time to go back to normal.

And even then that doesn't factor in to say that all this energy its taking in, isn't being vortex'd to another space or even time.

So, as a summary, I suppose what I'm concluding black holes to be, is an enormous sphere of negative. And as all things want to be neutral, it sucks in as much positive (the reality we live in) as possible, practically, indefinitely, all positive matter that goes near it to be sucked in without flaw, no possible escape. To anwser whether it has mass, I really don't know for sure, but from what I can tell, it has a Finite mass. But the time required for it to reach a neutral point is absolutely rediculous, seeing as how it would have to fill all that space flawlessly, to the absolute with the little bit of energy that it gets coming in from light, or small fragments of atoms.

But again, I have no real knowledge on the topic, its just my educated guess on what I've read and learned over a little while.


If a black hole has a mass of a universe what will be the volume of it? - Astronomy

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Black Holes And Cosmology

The classical solution for a black hole in the theory of General Relativity indicates that the time coordinate of 4-D space-time becomes the radial coordinate within the horizon of the black hole. That is, time as we know it no longer exists. In fact, if we examine the time coordinate just outside the horizon, we find that it goes into the infinite future. That is why our observation of an object entering the horizon goes on indefinitely into the future. It just becomes increasingly more difficult to observe the object as time goes on.

Now consider extrapolations of the same solutions for the Theory of General Relativity for the early universe. As we extrapolate backwards in time there comes a point where the density of the universe, on paper, is sufficient for it to be a black hole, long before we get to the 10**-34 sec regime where the strong forcesedly split from the electro-weak force. The difference between the early universe and a black hole is that the black hole has a central concentration of mass with lots of space around it whereas the early universe is a uniform distribution of mass under rapid expansion with no space around it. The mass fills all space but the volume of the space is unknown.


The Coevolution of Galaxies and Supermassive Black Holes: Insights from Surveys of the Contemporary Universe

We summarize what large surveys of the contemporary Universe have taught us about the physics and phenomenology of the processes that link the formation and evolution of galaxies with their central supermassive black holes. We present a picture in which the population of active galactic nuclei (AGNs) can be divided into two distinct populations. The radiative-mode AGNs are associated with black holes (BHs) that produce radiant energy powered by accretion at rates in excess of ∼1% of the Eddington limit. They are primarily associated with less massive BHs growing in high-density pseudobulges at a rate sufficient to produce the total mass budget in these BHs in ∼10 Gyr. The circumnuclear environment contains high-density cold gas and associated star formation. Major mergers are not the primary mechanism for transporting this gas inward secular processes appear dominant. Stellar feedback is generic in these objects, and strong AGN feedback is seen only in the most powerful AGNs. In jet-mode AGNs the bulk of energetic output takes the form of collimated outflows (jets). These AGNs are associated with the more massive BHs in more massive (classical) bulges and elliptical galaxies. Neither the accretion onto these BHs nor star formation in their host bulge is significant today. These AGNs are probably fueled by the accretion of slowly cooling hot gas that is limited by the feedback/heating provided by AGN radio sources. Surveys of the high-redshift Universe paint a similar picture. Noting that the volume-averaged ratio of star formation to BH growth has remained broadly constant over the past 10 Gyrs, we argue that the processes that linked the cosmic evolution of galaxies and BHs are still at play today.


Black Holes Influence Knowledge Of The Universe

University Park, Pa. -- Black holes have a reputation for voraciously eating everything in their immediate neighborhood, but these large gravity wells also affect electromagnetic radiation and may hinder our ability to ever locate the center of the universe, according to an international research team.

"Any attempt to discover what was happening a long time ago at the beginning of our universe must take into account what gravitationally assisted negative refraction does to the radiation being viewed," said Akhlesh Lakhtakia, distinguished professor of engineering science and mechanics at Penn State.

Electromagnetic radiation is affected by the material through which it travels. A material with a negative index of refraction transmits light or other wave energy differently than one with a positive index of refraction. Natural materials have positive index of refraction. When an energy beam -- light, radar, microwaves -- passes through water or glass or some other natural material, the material displaces the beam in the same direction. The amount of displacement depends upon how different the material is from air or vacuum. The displacement, due to a material with negative index of refraction, is in the opposite direction.

Previously, Lakhtakia and Tom G. Mackay, lecturer in mathematics at the University of Edinburgh, used Albert Einstein's Special Theory of Relativity to examine refraction by moving materials. They calculated that negative refraction can be concluded to have occurred by an observer moving at a very high relative velocity in certain directions.

Later they showed that no material is needed for negative refraction in outer space. Instead, when a beam passes through the gravitational field of a massive object such as a rotating black hole, negative refraction theoretically is possible.

When it comes to the influence of gravity caused by rotating black holes or other massive objects, it really depends on where one stands. A local observer can see only a very small piece of the universal picture of how large gravitational forces influence electromagnetic radiation. To the local observer, gravity is uniform and does not cause negative refraction.

However, Lakhtakia and Mackay, assisted by Sandi Setiawan, a postdoctoral researcher at the University of Edinburgh, decided to look at a global observer -- one who stands in space-time as described by Einstein in his General Theory of Relativity. A global observer sees a region around rotating black holes, called the ergosphere, as possibly bending electromagnetic radiation according to a negative refractive index.

These new derivations, reported in the March 7 issue of Physics Letters A, indicate that not only do the effects of the minute stuff of the universe have to be considered when mapping the universe, but the existence of large gravity wells also must be considered.

"When we are tracking light, we must take into account gravitational forces," said Lakhtakia. "Although the effect is only significant very close to rotating black holes."

The three researchers have extended their theory of negative refraction to even more general scenarios, in a paper published today (March 8) in the New Journal of Physics, an electronic journal. As we reach out in extrasolar space, for example via Pioneer 10, scientists are getting more interested in the actual existences of such scenarios.

Normal light bending by a gravity source such as our Sun is known as gravitational lensing. It has been suggested since Einstein&rsquos time and was experimentally shown by a British team of scientists in 1919. This gravitational lensing sometimes causes multiple images to be seen. The effect is taken into account in global positioning systems. However, this light bending is positively refracted.

When researchers search for the origin of the universe, multiple black holes and other massive objects can make the light beams bend in unexpected and unpredictable ways.

"We should not be disappointed if we cannot discover the origin of the universe," said Lakhtakia. &ldquoThe gravitational effect probably makes it so that we do not really know where we are looking.&rdquo

Nevertheless, Lakhtakia and his collaborators are optimistic that scientists eventually will overcome many of the obstacles put forward by negative refraction in outer space.

Story Source:

Materials provided by Penn State. Note: Content may be edited for style and length.


If a black hole has a mass of a universe what will be the volume of it? - Astronomy

General relativity predicts that as an object collapses to form a black hole, it will eventually reach a point of infinite density. What that really means is that the theory of relativity breaks down at this point, and no one knows what happens at the center of a black hole - we would need a viable theory of quantum gravity in order to understand this.

But here's something that you might find useful: when we talk about the "size" of a black hole, we usually talk about something called the Schwarzschild radius. The Schwarzschild radius is the "point of no return" - once you get closer to the black hole than it, you can never escape. Consequently, the escape speed at the Schwarzschild radius is equal to the speed of light, and the value of the Schwarzschild radius works out to be about (3x10 5 cm) x (M / Msun), where M is the mass of the black hole and Msun is the mass of the Sun. (Typically, M for a black hole in our galaxy is around 10 times the mass of the Sun, but for supermassive black holes at the centers of galaxies it can be millions or even billions.)

There is a rough analogy between a black hole and an atom. In both cases, the mass is concentrated in a tiny region at the center, but the "size" of the object is much bigger. You can use the Schwarzschild radius to calculate the "density" of the black hole - i.e., the mass divided by the volume enclosed within the Schwarzschild radius. This is roughly equal to (1.8x10 16 g/cm 3 ) x (Msun / M) 2 , where M is defined as above. From the point of view of an outside observer, this might as well be the actual black hole density, since the distribution of matter within the Schwarzschild radius has no effect on the outside.

This page was last updated June 27, 2015.

About the Author

Dave Rothstein

Dave is a former graduate student and postdoctoral researcher at Cornell who used infrared and X-ray observations and theoretical computer models to study accreting black holes in our Galaxy. He also did most of the development for the former version of the site.


Observations of the Lyman-α Universe

A typical Lyα emitter (LAE) at z ≳ 2 with a L * Lyα luminosity is a high-z counterpart of a local dwarf galaxy, a compact metal-poor star-forming galaxy (SFG) with an approximate stellar (dark matter halo) mass and star-formation rate of 10 8−9 M (10 10−11 M) and 1–10 M year −1 , respectively.

High-z SFGs ubiquitously have a diffuse Lyα-emitting halo in the CGM extending to the halo virial radius and beyond.

Remaining neutral hydrogen at the epoch of cosmic reionization makes a strong dimming of Lyα emission for galaxies at z > 6 that suggests the late reionization history.

The next-generation large-telescope projects will combine Lyα emission data with Hi Lyα absorptions and 21-cm radio data that map out the majority of hydrogen ( Hi + Hii ) gas, uncovering the exchanges of (a) matter by outflow and inflow and (b) radiation, relevant to cosmic reionization, between galaxies and the CGM/IGM.


If a black hole has a mass of a universe what will be the volume of it? - Astronomy

Photons (which are the "particles" that make up light) have zero rest mass. To understand why photons "fall" into a black hole, you need to know a bit of general relativity. What general relativity says is that any massive object warps the spacetime around it. You can think of this with a simple analogy. Imagine a stretched rubber sheet that is completely flat. This represents the spacetime when there is no mass. Now, if you put a heavy ball in the rubber sheet, it will cause a distortion in the sheet. This is exactly what happens in space, except that it is in 3 dimensions instead of two.

Further, a photon always travels by the shortest distance between two points. As spacetime is warped, the light appears to bend around a massive object. In reality, it is not that the object is attracting light, but it is just that the photons are traveling by the shortest distance in a curved spacetime.

Around a black hole, the distortion of spacetime is extreme. At the event horizon of a black hole, the spacetime curves into itself and as a result, light cannot escape from a black hole.

This page was last updated June 27, 2015.

About the Author

Jagadheep D. Pandian

Jagadheep built a new receiver for the Arecibo radio telescope that works between 6 and 8 GHz. He studies 6.7 GHz methanol masers in our Galaxy. These masers occur at sites where massive stars are being born. He got his Ph.D from Cornell in January 2007 and was a postdoctoral fellow at the Max Planck Insitute for Radio Astronomy in Germany. After that, he worked at the Institute for Astronomy at the University of Hawaii as the Submillimeter Postdoctoral Fellow. Jagadheep is currently at the Indian Institute of Space Scence and Technology.


The Faintest Dwarf Galaxies

Joshua D. Simon
Vol. 57, 2019

Abstract

The lowest luminosity ( L) Milky Way satellite galaxies represent the extreme lower limit of the galaxy luminosity function. These ultra-faint dwarfs are the oldest, most dark matter–dominated, most metal-poor, and least chemically evolved stellar systems . Read More

Supplemental Materials

Figure 1: Census of Milky Way satellite galaxies as a function of time. The objects shown here include all spectroscopically confirmed dwarf galaxies as well as those suspected to be dwarfs based on l.

Figure 2: Distribution of Milky Way satellites in absolute magnitude () and half-light radius. Confirmed dwarf galaxies are displayed as dark blue filled circles, and objects suspected to be dwarf gal.

Figure 3: Line-of-sight velocity dispersions of ultra-faint Milky Way satellites as a function of absolute magnitude. Measurements and uncertainties are shown as blue points with error bars, and 90% c.

Figure 4: (a) Dynamical masses of ultra-faint Milky Way satellites as a function of luminosity. (b) Mass-to-light ratios within the half-light radius for ultra-faint Milky Way satellites as a function.

Figure 5: Mean stellar metallicities of Milky Way satellites as a function of absolute magnitude. Confirmed dwarf galaxies are displayed as dark blue filled circles, and objects suspected to be dwarf .

Figure 6: Metallicity distribution function of stars in ultra-faint dwarfs. References for the metallicities shown here are listed in Supplemental Table 1. We note that these data are quite heterogene.

Figure 7: Chemical abundance patterns of stars in UFDs. Shown here are (a) [C/Fe], (b) [Mg/Fe], and (c) [Ba/Fe] ratios as functions of metallicity, respectively. UFD stars are plotted as colored diamo.

Figure 8: Detectability of faint stellar systems as functions of distance, absolute magnitude, and survey depth. The red curve shows the brightness of the 20th brightest star in an object as a functi.

Figure 9: (a) Color–magnitude diagram of Segue 1 (photometry from Muñoz et al. 2018). The shaded blue and pink magnitude regions indicate the approximate depth that can be reached with existing medium.


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