Anything can become a black hole, and yes, that includes light
Black holes are both extremely horrifying and captivating. I mean, they can possibly DESTROY INFORMATION, DESTROY WHOLE SOLAR SYSTEMS AND CAN BE MADE BY ANY OBJECT IN THE UNIVERSE! That is utterly awesome but also incredibly scary at the same time. And yes, you heard me correctly, ANYTHING can become a black hole! A dog, cat, airplane, that one weird dude on the subway, you and even light can become a black hole if compressed tightly enough! I guess you could make some very broad categories of black holes. One could be that black holes can be made from pure electromagnetic radiation, aka light, which is called a Kugelblitz,and another can be that black holes can be made from all matter which are called, well, black holes.
First we must define what a black hole is, and how they originate for those that do not entirely know what they actually are. A black hole, quite simply, is a point in spacetime (called a singularity) with an escape velocity that of or greater than the speed of light (for black holes with angular momentum, the singularity is theorized not to be a single point, but a ring with zero width). That means nothing, not even light itself, can escape its gravitational pull. “That is pretty terrifying to be completely honest, but how are black holes made?” some may ask. Well, black holes are simply reminisce of large, dead stars. Stars die in two ways: one is the star becomes a red giant and then dissipates into a white dwarf, and the other is the star blows up in a cosmic version of a fireworks show, aka a supernova. This happens because a star is in a constant battle with gravity, and it fights gravity with nuclear fusion, the fusion of light atoms into heavier atoms. Everything is in an equilibrium until the star starts to fuse iron, that is when gravity starts winning because iron cannot be fused into any other element in a star. Once iron becomes insanely common in the core, no fusion can occur, thus the equilibrium is broken. Now, when this happens in a big enough star, that star will implode violently which results in a supernova. In turn, a supernova results in either a neutron star or a black hole depending on the mass of the star. The mass needed for a star to go supernova is about 1.4 times the mass of the Sun. This is called the Chandrasekhar Limit named after astrophysicist Subrahmanyan Chandrasekhar who was born in Lahore, British India, present day Pakistan. This limit states that any star at or over 1.4 times the mass of the Sun will end its life in a supernova.
Similarly, a Kugelblitz is a black hole, but it is not made from dead stars, oh no, it is made by light (kugelblitz in German means “ball lightning”). This may may confuse some because, as some may or may not know, photons are massless particles. “How may this confuse some people” I hear some asking, well, gravity is best known by people being caused by objects with mass which can be backed up by Newton’s equation:
where F is the gravitational force between the two objects, m1 and m2 represent the masses of the two objects, r is the distance between the two objects from center of mass and G is the gravitational constant: 6.673×10^-11 N m2kg-2
Now in this case, Newton did not know that photons can warp spacetime, and this was not said, really, until Einstein’s time. In fact, Newton didn’t even know that photons even existed, for photons were discovered in the early 1900s and first proposed by Albert Einstein, himself, in 1905 as “a quantum of light”. Anyways, Einstein said it best with his E = mc^2 equation. However, this equation is only simplified to motionless objects. The full equation is:
E² = (mc²)² + (pc)²
where E is energy, m is mass, p is momentum and c is the speed of light, 299,792,458 m/s in a vacuum. If the mass of some particle is zero, the particle can still be energetic because of the momentum part of the equation. This is important because Einstein stated that both mass and energy warp spacetime, thus allowing light to warp spacetime. But don’t just take Einstein’s word for it, take the Universe’s. The phenomenon of gravitational lensing is the bending of light by the gravity of a more massive object (i.e. a star, black hole, galaxy etc.). This event has been recorded numerous times and can be seen extremely well in this picture taken by The Hubble Space Telescope (the bent lines in the center is light from other galaxies being bent by the gravity of other galaxies in front of them .
If light were to not bend spacetime, then it would not interact gravitationally with other objects, therefore light must bend spacetime.
Now since we went through how light can manipulate spacetime, we must talk about what exactly a Kugelblitz is. To start, you are going to need a lot, and I mean A LOT of energy to create a Kugelblitz. To get an Earth-size Kugelblitz, you must store all the light emitted over a 10 year period by all the stars in a 350 light years range from Earth into an area the size of a mosquito, A DANG MOSQUITO!! By picking 50 random nearby stars, recording their classification and recording the average luminosity for each star class, I came up with a combined luminosity of 582.72 suns each year. Multiplying that by 10 and you get a luminosity of 5,827.2 suns per 10 years. To give you an idea about how much energy that is, the Sun gives off around 1.19852e+34 Joules per year ( that is 1.19852 followed by 34 zeros)!! Per year for the other 50 stars, it is 6.9840157e+36 Joules!! Take into note that, as said before, I only picked 50 stars out of 243 that are in a 100 light year range. To create a Kugelblitz the mass of the Earth, all the light emitted in 10 years by all stars in a 350 LIGHT YEAR DISTANCE from Earth will have to be compressed into an area the size of a mosquito. So to say that is a lot of energy is a major understatement
Schwarzschild Radius and Black Holes
As I stated earlier in this article, any object can become a black hole if compressed small enough. The length at which an object must be in order to become a black hole is called the Schwarzschild Radius.The Schwarzschild Radius can be found by using the equation
where R is the Schwarzschild Radius, G is the gravitational constant which was mentioned earlier, M represents the mass of the object and c is the speed of light which was also mentioned earlier . Doing the calculations, the average human male, weighting at 70kg, would have to be squeezed into the space of 1.03959078301e-25 meters to become a black hole! That is way bigger than strings from The String Theory (1e-34 meters) but way, way smaller than protons which are 10e-15 meters! May I add that strings are said to compose quarks and other elementary particles which are extremely small, smaller than a proton!!! Another good example can be the Sun. For the Sun to become a black hole, it would need to be compressed down into a size of 2.9539 kilometers! That is around one third the size of Mt. Everest!
In the end, anything, and yes, even light, can become a black hole if it is compressed beyond belief! Not only that, but as I was writing this, I came to the realisation that one little math equation could say rather beautiful and elegant things. I mean, to have an equation this simple, compared to others, yet one that says a lot is just mind boggling!!
: My name is Jason Pusic and I am a 15 year old science enthusiast. My interests primarily lay in physics, astronomy and astrophysics, but I am a fan of all sciences such as neuroscience, chemistry, evolutionary biology, etc. I hope everyone is loving what not only I post, but what all authors post on this magnificent website!