Have you ever thought how lucky we are to breath this fresh air and drink the sweet water? If you have some free time then why not take a ride with us on a trip to ‘Our past’!
It is always good to know more about our physical being, and the best way of doing so is to learn more about the evolution of our own Cosmos! Ready! Ok!With the development of science, the story of ‘The beginning of Cosmos’ also changed. The concept of physical law replaced the whimsy of the Gods as a controlling factor of Cosmos as a whole. The Universe began at least fifteen billion years ago, the first clouds consisting elements of hydrogen and helium were formed. In the next step, this cloud of Hydrogen & Helium, due to strong gravitational forces collapsed to form stars. Slowly, after some years these stars started altering hydrogen and helium into heavier elements viz. Carbon, nitrogen and oxygen.
Understandably, these three elements became the most vital for life on earth. This was followed by some explosions in some of the stars. Due to explosions these elements were then thrown up into the space in some of these stars. This material formed clouds, that contained molecules of water, carbon monoxide and hydrocarbons. And finally, these clouds collapsed, due to gravitational pull, to form new stars and solar systems and a host of other interstellar things like meteorites, asteroids, comets etc. You know , we are always lucky to be on Earth! It was nothing but a fortunate planet since its origin. Incidentally it was placed at the right distance from the Sun. This positioning has provided us with the right conditions for life! So you see how lucky we are to be born on this EARTH! You must have heard about the BIG BANG theory, no? Ok, listen to it now! Actually what happened was in the early 1920’s, Edwin Hubble proved that there were galaxies beyond the Milky Way.He also determined that these other galaxies were moving away from us and each other in all direction. His observations finally gave us a means of determining our distance from these galaxies and objects within our own. Combining early works of Einstein’s 1915 ‘theory of gravitation’ with Hubble’s observations led to the conclusion that all the galaxies, and the whole Universe, had originated in a great explosion. In the final analysis, just imagine, one moment there was nothing; the next all the elements that make up our universe were sent rushing outward away from the epicenter. This theory, commonly referred to as The Big Bang theory, began the story of modern Cosmology! This is how our universe was created approximately 15 billion years ago. Interesting, no !
THE STORY OF BLACK HOLE
We are not talking about Golf hole’s here! If you take a ride around our Cosmos you will come across some dead stars, which has so much mass concentrated in it due to it’s size, that there is no way for nearby objects to escape it’s gravitational pull. These are nothing but ‘Black Hole’s. Funny thing is that, you cannot escape a ‘Black Hole’. It’s a bit complicated to understand, ok, let me clarify in simple terms. Our horizon has very strange geometrical properties.Suppose you are an observer sitting somewhere far away from the black hole, you will find the horizon to be a nice, static, unmoving spherical surface. But as you get closer to the horizon, you will realize that it has a very large velocity. You’ll find it moving outward at the speed of light! That explains why it is easy to cross the horizon in the inward direction, but impossible to get back out. Since the horizon is moving out at the speed of light, in order to escape back across it, you would have to travel faster than light. And you can’t go faster than light, so you see I was not joking when I said ‘you can’t escape from the black hole’. Hey, do you have any idea how big this Black Hole can be? A typical mass of black hole would be about 10 times the mass of the Sun, or about 10^{31} kilograms. This means 10,000,000,000,000,000,000,000,000,000,000!How about that, beyond your imagination, I guess! Simply put, the more massive a black hole would be, the more space it will take up. In fact, a black hole’s the radius of the horizon and the mass are directly proportional to one another. Suppose, a black hole weighs 10 times as much as another, its radius is ten times as large. A black hole with a mass equal to that of the Sun would have a radius of 3 kilometers. So a typical 10-solar-mass black hole would have a radius of 30 kilometers, and so on it goes!
BLACK HOLES ARE NOT FICTIONS – IT’S A REALITY
Get out of the illusion that whatever I said about ‘Black Holes’ are fantasy. No doubt, people say ignorance is bliss! Of course you can’t see a black hole directly since light cannot get past the horizon. So you got to trust my words that black holes does exist! What? You don’t rely my words, ok, then let me approach in a more scientific way. You can easily check if there is a black hole or not. Suppose you bump on to a zone of space where you think there might be a black hole. The first thing you got to do is t o measure how much mass there is in that zone. Incase you find a large mass concentrated in a small volume, and if the mass is dark, then it’s a good guess that there’s a black hole there. Its simple logic based on scientific observation. Our own Galaxy also has a completely different class of black-hole possibilities. These are much lighter, stellar-mass black holes. These holes are thought to form when a massive star ends its life in a supernova explosion. You can find this out too, incase you can catch hold of a X-ray binary system, then can you tell whether the unseen compact object is a black hole. How? Well, first of all estimate its mass. By measuring the orbital speed of visible star (together with a few other things), you can figure out the mass of the invisible companion.If the mass of the compact object is found to be very large very large, then there is no kind of object we know about that it could be other than a black hole.
BLACK HOLE = EVAPORATION = ZERO
Due to quantum-mechanical effects Black Holes emits radiation. This energy that produces the radiation comes from the mass of the black hole itself. This results in a gradual shrink in the black hole. It turns out that the rate of radiation increases as the mass decreases, so the black hole continues to radiate more and more intensely and to shrink more and more rapidly until it presumably vanishes entirely. Look here, I can’t vouch on that statement. Frankly speaking, nobody is dead sure about what happens at the last stages of a black hole evaporation.
May be, a tiny, stable remnant is left behind, but I am not sure. Physicists often believe that they have the correct theories to make predictions about black hole evaporation, but without experimental tests, it’s impossible to be sure. And these experimental tests are very difficult to perform.
YES, WE HAVE WORM HOLES TOO!
Before reading any further, let me confess one fundamental fact that wormholes almost certainly do not exist. I know you are not dumb enough to believe onto something just because it is a valid mathematical solution to the equations! No that doesn’t mean it actually exists in nature. Still interested, ok then read on! Do not confuse yourself with a White hole, Black hole and a Worm hole. Just remember, there is a possibility to fall into a black hole that is rotating or charged. Basically what happens, the interior of a charged or rotating black hole joins up with a corresponding white hole in such a way that one can fall into the black hole and pop out of the white hole! No jokes it might happen. THIS COMBINATION OF BLACK AND WHITE HOLES IS CALLED A WORMHOLE. In case a wormhole is identified then perhaps it would provide a convenient and rapid way to travel very large distances, or even to travel to another Universe! Logically the exit to the wormhole would lie in the past, so you could travel back in time by going through one such whole. Science fiction, no! What’s more, even if a wormhole is formed, rest assured it cannot be stable. A slightest perturbation, including the perturbation caused by your attempt to travel through it, would cause it to collapse. Finally, even if wormholes exist and are stable, they are quite unpleasant to travel through. Radiation that pours into the wormhole (from nearby stars, the cosmic microwave background, etc.) gets blue shifted to very high frequencies. Watch out! as you try to pass through the wormhole, you will get fried by these X-rays and gamma rays. ENJOY YOUR TRIP!
THE BIG BANG!
The universe is thought to have started with a huge explosion called the Big Bang.The English astrophysicist Fred Hoyle in 1950 gave this term to the world. But don’t think that explosion was like any James Bond movie. It wasn’t really an “explosion” in the sense that we understand it. Space itself exploded. Try and understand the situation, space and time came into existence and all the matter in the cosmos started to expand. This ‘episode’ created space-time and so there was no time ‘before’ the Big Bang, and no space outside it. This was no ordinary earthly explosion starting from a definite center and spreading out to engulf more and more, but an explosion which occurred simultaneously everywhere, filling all Space from the beginning with energy. At the instant of the Big Bang, the universe was infinitely dense and unimaginably hot. It is believed that all forms of matter and energy, as well as space and time itself, were formed at this instant. One cannot ask what came before the Big Bang and therefore “caused” it. IN SUPPORT OF BIG-BANG THEORY1.Hubble discovered that the galaxies are receding from us in all directions is a consequence of this initial big bang explosion. Today, we have excellent evidence for Hubble’s law which states that the recessional velocity of a galaxy is proportional to its distance away from us.2. Big Bang theory predicts that 25 % of the total mass of the universe should be the helium that formed during the first few minutes, an amount that agrees with observations. Prior to about one second after the Big Bang, matter – in the form of free neutrons and protons (nucleons) – was very hot and dense. As the universe expanded, the temperature fell and some of these nucleons were synthesized into the light elements: deuterium, helium-3, and helium-4.Theoretical calculations predict that about a quarter of the universe consists of helium-4, this result is a good agreement with current observations. 3. About 100,000 years after the Big Bang, the temperature of the universe had dropped sufficiently for electrons and protons to combine into hydrogen atoms. From this time onwards, radiation was effectively unable to interact with the background gas; it has propagated freely ever since, while constantly losing energy because its wavelength is stretched by the expansion of the universe. Originally, the radiation temperature was about 3000 degrees Kelvin; today it has fallen to only 3K – a ghostly remnant of the unimaginably intense heat of the primeval fireball of the Big Bang.4. At about 10,000 years after the Big Bang, the temperature had fallen to such an extent that the energy density of the universe began to be dominated by matter, rather than the light and other radiation which predominated earlier. Gravitational forces between the particles began to take effect, and small perturbations in their density grew; 15 billion years later we see the results of this collapse.
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THE REDSHIFT
Just consider the fact , if the universe were expanding from a “big bang” then the material moving faster would now be farther away. The relative velocity between any two objects would be proportional to the distance between them. According to the Doppler principle, any radiation to be stretched to longer wavelengths with increasing relative velocity. Observed radiation from distant objects would then be red shifted in proportion to the distance of the objects. But obviously the converse is not necessarily be true. Observation of red shift increasing with distance does not necessarily mean that the more distant objects are moving faster. You can define The cause of RED SHIFT in a different method than the Doppler principle. Toss a pebble into a calm pond and observe closely the waves moving outward. Within the first few wavelengths, the distance between 2 adjacent crests increases by a small but observable amount as the waves move out. In this case, the shift is caused by an unsymmetrical medium. The wave crests do not have the same shape as the troughs. The dissymmetey is amplitude sensitive so that as the waves grow shallower the shift diminishes. Another form of non-linearity could produce a wavelength shift with distance traveled and might not be affected by either amplitude or frequency. Suppose the electric Permitivity, dielectric constant, for free space is not constant but varies by a small factor with change of electric flux density then electromagnetic propagation in space is not linear. If we substitute a function of electric flux density for the dielectric constant in Maxwell’s equations they become nonlinear. This is an important phenomenon which has to be taken into consideration while discussing on redshift.
QUASAR
Quite natural to expect burned out stars as well as burning stars to coalesce and produce giant objects at the centers of galaxies where star density is massive. If Quasars depended only on the mechanical energy of collapse and the fusion energy of remaining fusionable material of coalescing stars they could not last long. At the observed brightness all the available energy in an entire galaxy would last only a few years. Considering the above facts, then the observable Quasars would be very rare and probably unknown. When the mass becomes sufficiently great the structure of nuclear material will begin to break down allowing positive and negative electrons to annihilate and release tremendous energy. This energy will thermally support the outer material thus regulating the annihilation. The result then is a Super Star of thousands to millions of solar masses which runs on annihilation instead of fusion.
WE ARE NOT ALONE IN THE GALAXY
Astronomical knowledge cannot expand at a jet speed, at times it is frustratingly slow and painstaking. A small step in scientific understanding needs an effort of dozens of astronomers over many years. But sometimes, reverse is also possible when progress comes in giant leaps that revolutionize our knowledge of the universe. Best example of a giant leap of progress was the conclusion that the universe is filled with countless other galaxies. Exactly like our own galaxy, the Milky Way. Each of these galaxies contain millions or billions of stars. It all started with astronomer Edwin Hubble study on the autumn constellation Andromeda known as the Andromeda Nebula. It looks like a pinwheel, with bright streamers wrapping around a big bulge in the middle. At the time, most astronomers thought the Andromeda Nebula and similar objects were bright pockets of matter inside the Milky Way. But on October 6, 1923 , one of Hubble’s photographs revealed a star inside the Andromeda Nebula that he hadn’t seen before.Hubble soon realized that the star was a Cepheid variable, a type of star that astronomers use to measure distances in the universe. Hubble found that this new Cepheid and others that he saw on different photographs were far outside the Milky Way. When Hubble revealed this findings the following year, astronomers realized that they had misnamed the Andromeda Nebula. It’s not a nebula at all. Instead, it’s a galaxy, the first confirmed “city of stars” beyond the Milky Way. Since Hubble’s discovery, astronomers have found that galaxies come in many shapes, sizes, and colors. Like the Andromeda galaxy and our own Milky Way, many are spiral shaped. Others look more like eggs or footballs, and still others have no form at all. The universe may contain 50 billion galaxies, or even more, who knows! The smallest galaxies contain only a million stars or so. The Milky Way is home to several hundred billion stars while the largest galaxies contain more than one trillion stars. Galaxies also contain vast clouds of gas and dust, which are the raw materials for new stars. Galaxies are scattered throughout the universe. Only 3 galaxies outside the Milky Way are easily visible to the unaided eye :-
1. The great galaxy in Andromeda
2. The Large Magellanic Clouds
3. The Small Magellanic Clouds.
These clouds are our nearest galactic neighbors. Although they are so far away that the light their stars produce today won’t reach us for tens of thousands or even millions of years. Some of the galaxies formed soon after the universe itself was born. These are the farthest galaxies that lie as far away as our telescopes can see. Some of them may be 10 billion light years away or farther. Now the bad news for the galaxy lovers, in theory, if the universe lasts long enough, the galaxies will all fall apart. Their stars will burn out. Some of the stars will drift away, but some will fall into giant “black holes” that lurk in the hearts of most galaxies. Eventually, all galaxies will disappear from sight. And then.. and then and then.
