MORE ON BLACK HOLES

 Stars come in various sizes. Our Sun is an average star in the Universe. Stars can vary with masses ranging from 0.08 solar masses to 100 solar masses.

It is found that stars with 1 solar mass is 10 times more common than stars with 2 solar masses, stars with 2 solar masses are 10 times more common than stars with 4 solar masses, and so on. The most common type is the Dwarf star with about 0.25 of the solar mass.

Like humans, stars too die, but a star's death does not mean the end of the star. It means the star has used up all the matter, the thermonuclear reactions have stopped, and the star loses its luminescence.

The more, the size of the star, the faster it uses up its matter and dies. For example, our Sun with a surface temperature of 5500 degrees K has a life span of 10 billion (1000 crore) years while the Red Dwarf star with about half the Sun's mass with a surface temperature of only 4000 degrees K can live for trillions of years.

There is a class of stars known as Super Giants. They are the largest known stars in the Universe but they are rare. The star Betelgeuse in the Constellation of Orion is a Super-giant. It has a diameter of 100 crore KM compared to just 14 lac KM for our Sun. However, the density of this star is negligible enough to be zero compared to 1.4 for our sun and its mass is just over 20 times that of the Sun. 

When these super giant stars which have masses over 20 solar masses die they become Super Novae and then form Black Holes. 

In both Novae and Super Novae a massive explosion would blow apart the matter in them. 

A Nova expends only a part of its matter in the explosion and has recurrent explosions and becomes a White Dwarf. 

A Super Nova explosion would blast massive amounts of matter with a mass of several times the sun into space and at that time it outshines an entire galaxy consisting of 10,000 crore stars. 

However, not all Supernovae explosions give rise to black holes. Stars with masses up to 20 times the sun turn into Neutron stars. Only those stars that is more massive than that turn into Black holes.

Any stellar object that collapses to the point where its radius is less than a certain limit must ultimately become a black hole. This critical radius is called the Schwarzschild radius. Only a star that has a mass of over 3 times that of the Sun can theoretically turn into a black hole. However, such conditions exist only in the most massive stars which are over 20 times the mass of the Sun.  

The Event horizon of a Black hole is its special outer boundary loosely considered to be its surface. It is the point where the gravitational attraction of the Blackhole becomes so great that even light cannot escape from it. That is why we can never receive a signal from the Event Horizon into the Black hole. The laws of Physics known to us break down inside the Event Horizon of the Black hole.

 

 

 

 

THE GREAT DYING OF SPECIES.

 

This is an event that took place 252 million years ago and is known as the Permian-Triassic extinction or the Great Dying. As the human species was born only 300,000 years ago and is still in its infancy that is a huge-huge amount of time for us. During this extinction event 81% of the marine species and 70% of the terrestrial vertebrate species died out.

However, please do not confuse this with the 65 million year old Dinosaur dying phenomena in the Cretaceous-Tertiary extinction which is totally different and happened at a different time altogether. The later event when the Dinosaurs died out had a much smaller effect on earthly life than the former event.

The Permian- Triassic event proved far more devastating to life on Earth. Trees, plants, lizards, proto mammals, insects, fish, molluscs and microbes, all were nearly wiped out. This is clearly visible through the fossils of that period.

Scientists have postulated many causes for the event; like severe volcanism, a nearby supernova, environmental changes, and the impact of an asteroid or a combination of those. However, proving anyone of them has been extremely difficult.  

Luan Becker, a Geologist from the University of California led a NASA funded research team to sites in Hungary, Japan and China where 250 million year old rocks still exist and are exposed. They found tell-tale signs of a collision between the Earth and an asteroid 6-12 Km across.

Becker’s evidence is direct and persuasive. In the rocks Becker’s team found soccer ball shaped molecules known as Fullerenes with traces of Helium and Argon gas trapped within them. They held an unusually large number of He³ and Ar³⁶ atoms which are isotopes more common in space than on Earth. It is highly probable (if not certain) that an Asteroid or a Comet must have brought in the Fullerenes when it collided with the Earth.  

Scientists believe that by the time the Asteroid/Comet hit the Earth was already suffering from high Volcanism and change of climate. The hit provided further impetus to the event and caused more devastation rather than being the sole cause itself.

If such a rock as proposed by Becker hits the earth, the blast would sweep over a large area on the Earth killing everything in its path. It would also throw up huge debris into the atmosphere that would obscure the Sun and hinder Photosynthesis. The atmospheric debris slowly rains back creating poisonous compounds on the Earth which can kill life.

The Palaeontologists have clearly shown that such hits by asteroids and other events detrimental to life may happen on the Earth and there are 2 big examples of that.

However, in the Geological timescale the human race is only born yesterday and has existed for a mere 300,000 years, thus there is hardly any chance that such a cataclysmic event would occur in such a short span of time in which the human species existed. But again, there is no guarantee that it would not either, which is the reason why a body like NASA continuously searches for the possibility of such a hit (if at all). Rather than the event, the way the human race is going; it is possible that it may wipe itself out with its own actions much before such an external factor hits us.     

ASTEROID THAT WOULD ZIP PAST THE EARTH ON 17th SEPTEMBER 2024

 

Before starting on this write up I want to make one thing very clear ...and that is, the Asteroid I am writing about below would not come anywhere near the Earth or affect us in any manner.....nevertheless, it is an interesting object to study.... 

An asteroid named 2024 ON that has an estimated diameter between 220 to 480 meters will zip past the Earth at a speed of about 32000 Km/hr on the coming Tuesday or 17th September. 

At the closest approach this asteroid would be around 1 million Km away from us which is 2.6 times the average distance between the Earth and the Moon.

 NASA does a great job of tracking 28000 asteroids which are termed as NEO( Near Earth Objects)   those objects that come within 193 million Km of the Earth. 

NASA also terms those coming within 7.5 million Km as Potentially Hazardous Objects ( PHO). 

All these NEO's and PHO's are being continuously tracked by a telescopic system known as ATLAS( Asteroid Terrestrial-impact Last Alert System) which is an array of 4 telescopes that perform a scan of the entire night sky every 24 hours. 

NASA has estimated the trajectories of all these NEO's even beyond the end of this century and as per their studies, the Earth faces no known danger from a dangerous asteroid collision for at least the next 100 years.

 However after all this still the YARKOVSKY EFFECT has to be accounted for which is a force by thermal photons that is acting on a rotating body which can affect its orbit. 

Its significance is felt most for smaller asteroids with a dia of 10 Cm to 10 Km. This effect makes the asteroids alter their orbits but hopefully NASA would be studying that aspect as well.

AI AND GEOFFREY EVEREST HINTON.

 

Geoffrey Hinton was born in 1947 and is considered as one of the pillars of Deep Learning. He is a Computer Scientist and Cognitive Psychologist noted for his work on artificial neural networks. He has published 200 peer-reviewed research papers on AI and neural networks and also guided a host of students to their PhD of which some are very well known in AI. A Neural Network is a network of connected artificial neurons, simulated within a computer and organized in layers 

He is a British Scientist who is currently located in Canada. Till the year 2018 he remained very optimistic about AI but later he moved away from that thinking as he felt that AI technologies would take away most jobs He worked for Google Brain (Google Brain was a deep learning artificial intelligence research team that served as the sole AI branch of Google before being incorporated under the newer umbrella of Google AI) for 10 years from 2013 onwards. He resigned from it in 2023 to speak freely about AI to the Public. By 2024 Hinton expressed the view that AI would generate more wealth but it would only make the rich richer and also hurt the people who lose their jobs.

Hinton is the great-great-grandson of the mathematician Mary Everest Boole and the logician George Boole. It was George Boole who first developed the Boolean Algebra which uses 0 and 1 and has been fundamental in developing Digital Electronics.  He is also the descendant of Sir George Everest, who was the then Surveyor General of India whose name has been given to Mt Everest.

George Hinton received the ‘Tuning Award” in 1918 referred to as the Nobel Prize in computing along with Yoshua Benzio and Yann LeCun (Chief AI Scientist for Meta) for Deep Learning. These 3 are often referred to as the Godfathers of Deep Learning and give public talks together. Currently, he is a Professor of Computers at the University of Toronto.  

Hinton now notes that “a part of him regrets his life’s work” due to his concerns about AI. He previously believed that AI is 30 to 50 years away but now he believes that it is only 20 years away and it would bring about drastic changes in our life comparable to the Industrial Revolution.

In 2023 Hinton said in an interview that AI might soon overtake the information capacity of the human brain. Hinton also expressed concerns about an AI takeover and that it is not inconceivable that AI could wipe out humanity. He has concerns that AI could be misused by malevolent persons.

 

ASTEROID APHOPHIS-A CLOSE CALL TO THE EARTH IN 2029

It is astronomy’s most notorious asteroid. In less than five years, Apophis - the “God of Chaos” - will come very close to the Earth but it will not hit.

When first discovered in 2004, initial orbital calculations for Asteroid 99942 Apophis put Earth in a collision “danger zone” during its 2029 and 2036 passes. By Dec 27 2004 calculations indicated that it has a probability of 2.7% to hit the earth in its 2029 pass. The asteroid set a record when it was upgraded to risk level number 4 on the Torino impact scale, which is the highest rating given to any asteroid on that scale.  

However, additional observations have eliminated the possibility of an impact. Till Aug 2006 a small possibility of it hitting the earth remained which kept at a risk level of 1 on the Torino scale but that was later brought down to zero.   

Apophis is a clump of rocks about 350 metres across. The mass of the asteroid is about 4*10⁷ tons at an assumed density of 2.6 gm/cm³. It was measured to be traveling at a speed of 30.70 Km/Sec. On an average, an asteroid of this size impacts Earth every 80,000 years.  

It packs a kinetic energy equivalent to 1200 Megatons of TNT. That is about 80,000 times the power unleashed by the Hiroshima Atom Bomb. Any such impact could be extremely dangerous to an area of thousands of square kilometres and it would create a 5.1 kilometre crater. However, it would leave no lasting impact on Earth. If it hits the sea then it would cause Tsunamis in the surrounding areas.  

But additional observations and radar ranging have since considerably refined its orbital projections.

We now know that, on April 13, 2029, it will miss Earth by 32,000 kilometres. That would be the closest approach to earth by Aphophis. It would be the closes asteroid to the Earth of that size to be ever recorded. The closest approach would be visible from Europe, Africa and Western Asia when it can be seen as a 3.1 magnitude object and is visible to the naked eye.  

Because of its close approach to the earth, tidal forces are likely to alter Aphophis’s rotational axis. The earth can therefore also alter the orbit of Aphophis.

Calculations of the Jet Propulsions laboratory, California indicate that there is no risk of it hitting the earth for a further 100 years. This laboratory was founded by Caltech but is now under NASA.

The geostationary satellites that power the GPS on our mobiles are at a distance of 35,800km from us.  So, cosmically speaking, Apophis is still going to be a very close call.

The European Space Agency (ESA) wants to take a good look at it as it catapults by.