What Are Black Holes?
How Black Holes Are Formed: A Story About Stars
Stars are massive collections of gases (mostly H2 and He) that collapse from very large gas clouds under their own gravity.
In the star's core, Hydrogen atoms are fused together (nuclear fusion) into Helium atoms, releasing a huge amount of energy in the process (in the form of photons*).
*Okay, so in one of our A Level Physics classes, we learned about mass defect, a consequence of nuclear fusion. Basically, when you fuse two nuclei together, you'd expect the end product to have the same mass as those two nuclei, right? Not really. It turns out that the reactants (in this case, the H2 atoms) will weigh slightly more than the products - The Helium atoms formed. This difference is what we call the mass defect. This "missing mass" is converted into energy. Einstein's mass defect equation shows us how: E = Δmc^2, and this energy is released in the form of photons (Photon, also known as light quantum, is a minute energy packet of electromagnetic radiation. Think exact amounts of energy packed into "boxes").
Where E = Energy released from nuclear fusion.
Δm = Mass difference.
c = Speed of Light.
Now, this energy's (in the form of photon radiation) thermal pressure pushes against the gravity that forced the gases into a star in the first place. This keeps the balance of the star, and it remains stable, so long as there is fusion within the core.
Stars much larger and heavier than our star, however, have cores that allow them to fuse elements until they reach iron (Fe).
Image from: University of Alberta
This is where the fun begins.
Once the core hits iron, there is no more nuclear fusion. The iron just keeps building and building within the star, depleting its "fuel", until it reaches a critical amount. Meaning there is no more photon radiation to balance out the gravity compressing the star.
In an instant, the star implodes. At a speed of up to 0.25cms^-1 (a quarter the speed of light), only adding more mass into the star. The star then blows up, adding matter into the space at which it occupied in the universe.
We have a few scenarios that could come forth from this. Either:
The collapsed star is transformed into a neutron star*.
If the star was as big as our sun, it would turn into a white dwarf star*.
If the star was big enough, the entire mass collapses into a black hole.
*I could get into neutron stars, white dwarfs and red dwarfs, but this is about black holes. Maybe at a later date.
A bit of history: Albert Einstein wrote a paper in 1939 claiming that stars could never collapse under their own gravity because matter could only be compressed by so much. But American scientist John Wheeler pointed out that stars could collapse via his research in the 1950s and 1960s and pointed out many problems within the field of theoretical physics.
Image of John Wheeler from: Nuclear Museum.
Wheeler is actually the scientist who coined the name "black hole". They were originally called "frozen stars". It took a while before the French adopted the name. There's a joke in there if you look hard enough.
So, then. Now that we do know that stars indeed can collapse under their own gravity, what happens to them?
What's the fate of collapsing stars too large and heavy to turn into dwarf or neutron stars?
The Singularity
Robert Oppenheimer (yes, the atom bomb guy) in 1939, along with George Volkoff and Hartland Synder showed that a star could not be supported by outward pressure - and that if you take pressure out of the calculations, a uniform spherically systematic star would contract to a single point of infinite density. The singularity.
A singularity is what you end up with when a giant star is compressed to an unimaginable small point. It not only marks the end of a star's life, but also the idea about the starting point for the formation of the universe*.
*I want to talk more about the universe in general, along with all its heavenly bodies and monstrosities. If you're into that, let me know.
All theories of space are formulated on space-time* being smooth and nearly flat, but they break down at the singularity, where the curvature of space-time is infinite.
*Space-time - Think of a trampoline. Flat and uniform. Now add a bowling ball to it. The trampoline curves into the bowling ball, allowing for smaller objects to move closer to the bowling ball. This is how we can describe how gravity works. How the Sun keeps the planets orbiting around it and how the Earth keeps the moon orbiting around it. The problem is the heavier the object, the deeper space-time will curve, to eventual infinity - where our regular laws of physics start to break. The deeper the curve, the greater the pull of gravity. Time also works differently around here (for example, if you fell into a black hole, the observer would just see you fall, turn red and disappear instead of you actually getting sucked into the thing), but that's also a topic for another day.
Image from: Simon's Space
Now, the force of gravity of blackholes is so large that nothing can escape from its pull once it's crossed a certain threshold. Nothing. Not even light. If that's the case, how do we know what to look out for if not even light can escape black holes?
What Black Holes (sorta) Look Like
If you actually ventured into space and found a black hole, what you'd actually be looking at is the event horizon, the black hole's boundary.
Image from: Google Images
At the event horizon, gravity is just strong enough to drag anything (including light) back into itself. Since nothing is faster than light, nothing can make it passed the event horizon due to its immense gravitational pull*.
*During one of our A Level physics classes, we learned (from chapter 13) how to calculate gravitational force. F = (G*M1*M2)/r^2, where:
F is the gravitational force acting on the body due to the second body.
G is the gravitational constant (6.67 * 10^-11 Nm^2kg^-2).
M1 is the mass of the first object.
M2 is the mass of the second object.
r is the distance between the two masses centre points.
Image from: Energy Wave Theory
You experience a large gravitational pull on Earth (your mass * 9.81ms^-2), but because we have evolved to live on Earth, it doesn't feel like anything out of the ordinary. However, consider the kind of gravitational pull you'd feel the closer you got into a black hole. A black hole with a mass of about 10 times that of the sun would have a mass of roughly 60 trillion trillion kilograms (6 x 10^25 kg). And as you get closer to the singularity, the force of the black hole grows exponentially larger. If you moved even a centimetre too close to a black hole, the gravitational force may just rip your skin off, and that's if you're lucky. Usually, you'd be crushed with so much force that once you'd have reached the singularity, you would be a hot stream of matter with the diameter of an atom (spaghettification). But this is a case-by-case situation, as smaller black holes will do this to you almost instantly and larger ones may let you float around the event horizon for a bit more time before you are eventually pulverised.
Now since nothing can go faster than the speed of light (at least for now), all we see is a black sphere reflecting nothing (since even light cannot escape from it).
The Death of Black Holes
As powerful as black holes are, they will eventually die via a process called Hawking Radiation.
To get a proper look at what this is, one has to look at empty space.
Empty Space
Alright, so empty space isn't actually empty. It's full of virtual particles popping into existence and annihilating each other.
When this happens next to the event horizon, one of the particles will be sucked into the black hole and the other will escape to become a real particle. The black hole is losing energy this way. Because the energy from annihilation is no longer being provided to the black hole. Think when electrons (β-) and positrons (β+) annihilate each other to convert their mass into gamma photons for PET Scans.
This process gets faster and faster the longer it goes on for, and the smaller the black hole gets (the black hole also radiates with hotter temperatures the smaller it gets).
This is a very slow process, though, so black holes will still be here long after the human race has died.
. . .
Hopefully you enjoyed reading up on what I discovered. Leave a comment if anything doesn't make any sense.
I plan on writing some more on topics like these, so please check out the site whenever you feel like learning something new.
Til next time.
What Are Black Holes?
How Black Holes Are Formed: A Story About Stars
Stars are massive collections of gases (mostly H2 and He) that collapse from very large gas clouds under their own gravity.
In the star's core, Hydrogen atoms are fused together (nuclear fusion) into Helium atoms, releasing a huge amount of energy in the process (in the form of photons*).
*Okay, so in one of our A Level Physics classes, we learned about mass defect, a consequence of nuclear fusion. Basically, when you fuse two nuclei together, you'd expect the end product to have the same mass as those two nuclei, right? Not really. It turns out that the reactants (in this case, the H2 atoms) will weigh slightly more than the products - The Helium atoms formed. This difference is what we call the mass defect. This "missing mass" is converted into energy. Einstein's mass defect equation shows us how: E = Δmc^2, and this energy is released in the form of photons (Photon, also known as light quantum, is a minute energy packet of electromagnetic radiation. Think exact amounts of energy packed into "boxes").
Where E = Energy released from nuclear fusion.
Δm = Mass difference.
c = Speed of Light.
Now, this energy's (in the form of photon radiation) thermal pressure pushes against the gravity that forced the gases into a star in the first place. This keeps the balance of the star, and it remains stable, so long as there is fusion within the core.
Stars much larger and heavier than our star, however, have cores that allow them to fuse elements until they reach iron (Fe).
Image from: University of Alberta
This is where the fun begins.
Once the core hits iron, there is no more nuclear fusion. The iron just keeps building and building within the star, depleting its "fuel", until it reaches a critical amount. Meaning there is no more photon radiation to balance out the gravity compressing the star.
In an instant, the star implodes. At a speed of up to 0.25cms^-1 (a quarter the speed of light), only adding more mass into the star. The star then blows up, adding matter into the space at which it occupied in the universe.
We have a few scenarios that could come forth from this. Either:
The collapsed star is transformed into a neutron star*.
If the star was as big as our sun, it would turn into a white dwarf star*.
If the star was big enough, the entire mass collapses into a black hole.
*I could get into neutron stars, white dwarfs and red dwarfs, but this is about black holes. Maybe at a later date.
A bit of history: Albert Einstein wrote a paper in 1939 claiming that stars could never collapse under their own gravity because matter could only be compressed by so much. But American scientist John Wheeler pointed out that stars could collapse via his research in the 1950s and 1960s and pointed out many problems within the field of theoretical physics.
Image of John Wheeler from: Nuclear Museum.
Wheeler is actually the scientist who coined the name "black hole". They were originally called "frozen stars". It took a while before the French adopted the name. There's a joke in there if you look hard enough.
So, then. Now that we do know that stars indeed can collapse under their own gravity, what happens to them?
What's the fate of collapsing stars too large and heavy to turn into dwarf or neutron stars?
The Singularity
Robert Oppenheimer (yes, the atom bomb guy) in 1939, along with George Volkoff and Hartland Synder showed that a star could not be supported by outward pressure - and that if you take pressure out of the calculations, a uniform spherically systematic star would contract to a single point of infinite density. The singularity.
A singularity is what you end up with when a giant star is compressed to an unimaginable small point. It not only marks the end of a star's life, but also the idea about the starting point for the formation of the universe*.
*I want to talk more about the universe in general, along with all its heavenly bodies and monstrosities. If you're into that, let me know.
All theories of space are formulated on space-time* being smooth and nearly flat, but they break down at the singularity, where the curvature of space-time is infinite.
*Space-time - Think of a trampoline. Flat and uniform. Now add a bowling ball to it. The trampoline curves into the bowling ball, allowing for smaller objects to move closer to the bowling ball. This is how we can describe how gravity works. How the Sun keeps the planets orbiting around it and how the Earth keeps the moon orbiting around it. The problem is the heavier the object, the deeper space-time will curve, to eventual infinity - where our regular laws of physics start to break. The deeper the curve, the greater the pull of gravity. Time also works differently around here (for example, if you fell into a black hole, the observer would just see you fall, turn red and disappear instead of you actually getting sucked into the thing), but that's also a topic for another day.
Image from: Simon's Space
Now, the force of gravity of blackholes is so large that nothing can escape from its pull once it's crossed a certain threshold. Nothing. Not even light. If that's the case, how do we know what to look out for if not even light can escape black holes?
What Black Holes (sorta) Look Like
If you actually ventured into space and found a black hole, what you'd actually be looking at is the event horizon, the black hole's boundary.
Image from: Google Images
At the event horizon, gravity is just strong enough to drag anything (including light) back into itself. Since nothing is faster than light, nothing can make it passed the event horizon due to its immense gravitational pull*.
*During one of our A Level physics classes, we learned (from chapter 13) how to calculate gravitational force. F = (G*M1*M2)/r^2, where:
F is the gravitational force acting on the body due to the second body.
G is the gravitational constant (6.67 * 10^-11 Nm^2kg^-2).
M1 is the mass of the first object.
M2 is the mass of the second object.
r is the distance between the two masses centre points.
Image from: Energy Wave Theory
You experience a large gravitational pull on Earth (your mass * 9.81ms^-2), but because we have evolved to live on Earth, it doesn't feel like anything out of the ordinary. However, consider the kind of gravitational pull you'd feel the closer you got into a black hole. A black hole with a mass of about 10 times that of the sun would have a mass of roughly 60 trillion trillion kilograms (6 x 10^25 kg). And as you get closer to the singularity, the force of the black hole grows exponentially larger. If you moved even a centimetre too close to a black hole, the gravitational force may just rip your skin off, and that's if you're lucky. Usually, you'd be crushed with so much force that once you'd have reached the singularity, you would be a hot stream of matter with the diameter of an atom (spaghettification). But this is a case-by-case situation, as smaller black holes will do this to you almost instantly and larger ones may let you float around the event horizon for a bit more time before you are eventually pulverised.
Now since nothing can go faster than the speed of light (at least for now), all we see is a black sphere reflecting nothing (since even light cannot escape from it).
The Death of Black Holes
As powerful as black holes are, they will eventually die via a process called Hawking Radiation.
To get a proper look at what this is, one has to look at empty space.
Empty Space
Alright, so empty space isn't actually empty. It's full of virtual particles popping into existence and annihilating each other.
When this happens next to the event horizon, one of the particles will be sucked into the black hole and the other will escape to become a real particle. The black hole is losing energy this way. Because the energy from annihilation is no longer being provided to the black hole. Think when electrons (β-) and positrons (β+) annihilate each other to convert their mass into gamma photons for PET Scans.
This process gets faster and faster the longer it goes on for, and the smaller the black hole gets (the black hole also radiates with hotter temperatures the smaller it gets).
This is a very slow process, though, so black holes will still be here long after the human race has died.
. . .
Hopefully you enjoyed reading up on what I discovered. Leave a comment if anything doesn't make any sense.
I plan on writing some more on topics like these, so please check out the site whenever you feel like learning something new.
Til next time.
What Are Black Holes?
How Black Holes Are Formed: A Story About Stars
Stars are massive collections of gases (mostly H2 and He) that collapse from very large gas clouds under their own gravity.
In the star's core, Hydrogen atoms are fused together (nuclear fusion) into Helium atoms, releasing a huge amount of energy in the process (in the form of photons*).
*Okay, so in one of our A Level Physics classes, we learned about mass defect, a consequence of nuclear fusion. Basically, when you fuse two nuclei together, you'd expect the end product to have the same mass as those two nuclei, right? Not really. It turns out that the reactants (in this case, the H2 atoms) will weigh slightly more than the products - The Helium atoms formed. This difference is what we call the mass defect. This "missing mass" is converted into energy. Einstein's mass defect equation shows us how: E = Δmc^2, and this energy is released in the form of photons (Photon, also known as light quantum, is a minute energy packet of electromagnetic radiation. Think exact amounts of energy packed into "boxes").
Where E = Energy released from nuclear fusion.
Δm = Mass difference.
c = Speed of Light.
Now, this energy's (in the form of photon radiation) thermal pressure pushes against the gravity that forced the gases into a star in the first place. This keeps the balance of the star, and it remains stable, so long as there is fusion within the core.
Stars much larger and heavier than our star, however, have cores that allow them to fuse elements until they reach iron (Fe).
Image from: University of Alberta
This is where the fun begins.
Once the core hits iron, there is no more nuclear fusion. The iron just keeps building and building within the star, depleting its "fuel", until it reaches a critical amount. Meaning there is no more photon radiation to balance out the gravity compressing the star.
In an instant, the star implodes. At a speed of up to 0.25cms^-1 (a quarter the speed of light), only adding more mass into the star. The star then blows up, adding matter into the space at which it occupied in the universe.
We have a few scenarios that could come forth from this. Either:
The collapsed star is transformed into a neutron star*.
If the star was as big as our sun, it would turn into a white dwarf star*.
If the star was big enough, the entire mass collapses into a black hole.
*I could get into neutron stars, white dwarfs and red dwarfs, but this is about black holes. Maybe at a later date.
A bit of history: Albert Einstein wrote a paper in 1939 claiming that stars could never collapse under their own gravity because matter could only be compressed by so much. But American scientist John Wheeler pointed out that stars could collapse via his research in the 1950s and 1960s and pointed out many problems within the field of theoretical physics.
Image of John Wheeler from: Nuclear Museum.
Wheeler is actually the scientist who coined the name "black hole". They were originally called "frozen stars". It took a while before the French adopted the name. There's a joke in there if you look hard enough.
So, then. Now that we do know that stars indeed can collapse under their own gravity, what happens to them?
What's the fate of collapsing stars too large and heavy to turn into dwarf or neutron stars?
The Singularity
Robert Oppenheimer (yes, the atom bomb guy) in 1939, along with George Volkoff and Hartland Synder showed that a star could not be supported by outward pressure - and that if you take pressure out of the calculations, a uniform spherically systematic star would contract to a single point of infinite density. The singularity.
A singularity is what you end up with when a giant star is compressed to an unimaginable small point. It not only marks the end of a star's life, but also the idea about the starting point for the formation of the universe*.
*I want to talk more about the universe in general, along with all its heavenly bodies and monstrosities. If you're into that, let me know.
All theories of space are formulated on space-time* being smooth and nearly flat, but they break down at the singularity, where the curvature of space-time is infinite.
*Space-time - Think of a trampoline. Flat and uniform. Now add a bowling ball to it. The trampoline curves into the bowling ball, allowing for smaller objects to move closer to the bowling ball. This is how we can describe how gravity works. How the Sun keeps the planets orbiting around it and how the Earth keeps the moon orbiting around it. The problem is the heavier the object, the deeper space-time will curve, to eventual infinity - where our regular laws of physics start to break. The deeper the curve, the greater the pull of gravity. Time also works differently around here (for example, if you fell into a black hole, the observer would just see you fall, turn red and disappear instead of you actually getting sucked into the thing), but that's also a topic for another day.
Image from: Simon's Space
Now, the force of gravity of blackholes is so large that nothing can escape from its pull once it's crossed a certain threshold. Nothing. Not even light. If that's the case, how do we know what to look out for if not even light can escape black holes?
What Black Holes (sorta) Look Like
If you actually ventured into space and found a black hole, what you'd actually be looking at is the event horizon, the black hole's boundary.
Image from: Google Images
At the event horizon, gravity is just strong enough to drag anything (including light) back into itself. Since nothing is faster than light, nothing can make it passed the event horizon due to its immense gravitational pull*.
*During one of our A Level physics classes, we learned (from chapter 13) how to calculate gravitational force. F = (G*M1*M2)/r^2, where:
F is the gravitational force acting on the body due to the second body.
G is the gravitational constant (6.67 * 10^-11 Nm^2kg^-2).
M1 is the mass of the first object.
M2 is the mass of the second object.
r is the distance between the two masses centre points.
Image from: Energy Wave Theory
You experience a large gravitational pull on Earth (your mass * 9.81ms^-2), but because we have evolved to live on Earth, it doesn't feel like anything out of the ordinary. However, consider the kind of gravitational pull you'd feel the closer you got into a black hole. A black hole with a mass of about 10 times that of the sun would have a mass of roughly 60 trillion trillion kilograms (6 x 10^25 kg). And as you get closer to the singularity, the force of the black hole grows exponentially larger. If you moved even a centimetre too close to a black hole, the gravitational force may just rip your skin off, and that's if you're lucky. Usually, you'd be crushed with so much force that once you'd have reached the singularity, you would be a hot stream of matter with the diameter of an atom (spaghettification). But this is a case-by-case situation, as smaller black holes will do this to you almost instantly and larger ones may let you float around the event horizon for a bit more time before you are eventually pulverised.
Now since nothing can go faster than the speed of light (at least for now), all we see is a black sphere reflecting nothing (since even light cannot escape from it).
The Death of Black Holes
As powerful as black holes are, they will eventually die via a process called Hawking Radiation.
To get a proper look at what this is, one has to look at empty space.
Empty Space
Alright, so empty space isn't actually empty. It's full of virtual particles popping into existence and annihilating each other.
When this happens next to the event horizon, one of the particles will be sucked into the black hole and the other will escape to become a real particle. The black hole is losing energy this way. Because the energy from annihilation is no longer being provided to the black hole. Think when electrons (β-) and positrons (β+) annihilate each other to convert their mass into gamma photons for PET Scans.
This process gets faster and faster the longer it goes on for, and the smaller the black hole gets (the black hole also radiates with hotter temperatures the smaller it gets).
This is a very slow process, though, so black holes will still be here long after the human race has died.
. . .
Hopefully you enjoyed reading up on what I discovered. Leave a comment if anything doesn't make any sense.
I plan on writing some more on topics like these, so please check out the site whenever you feel like learning something new.
Til next time.
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