Astronomy - Stephen Hawking

Old News

Cassini Completes Final Close Enceladus Flyby

NASA's Cassini spacecraft has begun transmitting data and images from the mission's final close flyby of Saturn's active moon Enceladus. Cassini passed Enceladus at a distance of 3,106 miles (4,999 kilometres) on Saturday, Dec. 19.
Although the spacecraft will continue to observe Enceladus during the remainder of its mission (through September 2017), it will be from much greater distances — at closest, more than four times farther away.

Christmas Eve Asteroid

Asteroid 2003 SD220 will safely fly past Earth on Dec. 24 at a distance of 6.8 million miles (11 million kilometres). Scientists at NASA's Jet Propulsion Laboratory in Pasadena, California, have generated the highest-resolution images to date of this asteroid using the Deep Space Network's 230-foot (70-meter) antenna at Goldstone, California. The radar images were acquired between Dec. 17 and Dec. 22, when the distance to this near-Earth object (NEO) was narrowing from 7.3 million miles (12 million kilometres) to almost the flyby distance.
Asteroid 2003 SD220 is highly elongated and at least 3,600 feet [1,100 meters] in length.
Three years from now, the asteroid will safely fly past Earth again, but even closer, at a distance of 1.8 million miles (2.8 million kilometres). The 2018 flyby will be the closest the asteroid will get to Earth until 2070, when it is expected to safely fly past our planet at a distance of about 1.7 million miles (2.7 million kilometres).

The first Full Moon on Christmas Day since 1977

This is the first Full Moon to occur on Christmas Day since 1977; another one won’t arrive until 2034.

Geminids set to light up winter sky in year's best meteor shower

From 13 to 15 December, weather permitting, sky watchers across the world will be looking up as the Geminid meteor shower reaches its peak, in potentially one of the best night sky events of the year.

New News

Venus and Saturn Conjunction

A very close conjunction between them occurring on Saturday, 9 January.
If the weather permits you to view Moon, Venus and Saturn in the same binocular field of view or just with the naked eye 7th Jan in the southeast.

Comet Catalina

Should be visible with binoculars if you have a dark sky, but a telescope would be ideal. Between the 14th and 17th the comet will pass by two stunning galaxies: M51, the whirlpool galaxy and M101, a fainter spiral galaxy.

The Constellation Orion

Winter is also the best time to view the constellation Orion in the south-eastern sky. Even in the city, you’ll see that its stars have different colours. Not telescope needed, just look up a few hours after sunset! The colourful stars of Orion are part of the winter circle of stars.

January 18th: Two Great Lunar Craters

This is a great night to observe two of the greatest craters on the Moon, Tycho and Copernicus.  Tycho is towards the bottom of Moon in a densely cratered area called the Southern Lunar Highlands. It is a relatively young crater which is about 108 million years old.  Copernicus is about 800 million years old and lies in the eastern Oceanus Procellarum beyond the end of the Apennine Mountains.   It is 93 km wide and nearly 4 km deep and is a classic "terraced" crater.   Both can be seen with binoculars.

Tim Peake Launch to International Space Station

Tim Peake successful launch to the International Space Station on the 15th Dec. They had a Problem with automatic docking guidance system and had to use manual docking, which delayed transfer from the Soyuz to the space station.

The Origin of the Universe
Stephen Hawkins

According to the Boshongo people of central Africa, in the beginning, there was only darkness, water, and the great god Bumba. One day Bumba, in pain from a stomach ache, vomited up the sun. The sun dried up some of the water, leaving land. Still in pain, Bumba vomited up the moon, the stars, and then some animals. The leopard, the crocodile, the turtle, and finally, man.

Aristotle, the most famous of the Greek philosophers, believed the universe had existed forever. Something eternal is more perfect than something created. He suggested the reason we see progress was that floods, or other natural disasters, had repeatedly set civilization back to the beginning.
If one believed that the universe had a beginning, the obvious question was what happened before the beginning?

The German philosopher, Immanuel Kant, felt there were logical contradictions, or antimonies, either way. If the universe had a beginning, why did it wait an infinite time before it began? He called that the thesis. On the other hand, if the universe had existed for ever, why did it take an infinite time to reach the present stage?

In 1915, Einstein introduced his revolutionary General Theory of Relativity. In this, space and time were no longer Absolute, no longer a fixed background to events. Instead, they were dynamical quantities that were shaped by the matter and energy in the universe. They were defined only within the universe, so it made no sense to talk of a time before the universe began.

Hubble found that stars are not uniformly distributed throughout space, but are gathered together in vast collections called galaxies. By measuring the light from galaxies, Hubble could determine their velocities. He was expecting that as many galaxies would be moving towards us as were moving away. This is what one would have in a universe that was unchanging with time. But to his surprise, Hubble found that nearly all the galaxies were moving away from us. Moreover, the further galaxies were from us, the faster they were moving away. The universe was not unchanging with time as everyone had thought previously. It was expanding. The distance between distant galaxies was increasing with time.

The expansion of the universe was one of the most important intellectual discoveries of the 20th century, or of any century. It transformed the debate about whether the universe had a beginning. If galaxies are moving apart now, they must have been closer together in the past. If their speed had been constant, they would all have been on top of one another about 15 billion years ago. Was this the beginning of the universe? Many scientists were still unhappy with the universe having a beginning because it seemed to imply that physics broke down.

The Steady State theory, proposed by Bondi, Gold, and Hoyle in 1948.
In the Steady State theory, as galaxies moved apart, the idea was that new galaxies would form from matter that was supposed to be continually being created throughout space. The universe would have existed for ever and would have looked the same at all times. This last property had the great virtue, from a positivist point of view, of being a definite prediction that could be tested by observation. But the observations showed more faint sources than predicted, indicating that the density sources were higher in the past. This was contrary to the basic assumption of the Steady State theory, that everything was constant in time. For this, and other reasons, the Steady State theory was abandoned.

If Einstein's General Theory of Relativity is correct, there will be a singularity, a point of infinite density and space time curvature, where time has a beginning. Observational evidence to confirm the idea that the universe had a very dense beginning came in October 1965, a few months after my first singularity result, with the discovery of a faint background of microwaves throughout space.
The only reasonable interpretation of the background is that it is radiation left over from an early very hot and dense state. As the universe expanded, the radiation would have cooled until it is just the faint remnant we observe today.
The other interpretation of our results, which is favoured by most scientists, is that it indicates that the General Theory of Relativity breaks down in the very strong gravitational fields in the early universe. It has to be replaced by a more complete theory. One would expect this anyway, because General Relativity does not take account of the small scale structure of matter, which is governed by quantum theory. This does not matter normally, because the scale of the universe is enormous compared to the microscopic scales of quantum theory. But when the universe is the Planck size, a billion trillion trillionth of a centimetre, the two scales are the same, and quantum theory has to be taken into account.

However, when one combines General Relativity with Quantum Theory, Jim Hartle and I realized that time can behave like another direction in space under extreme conditions. This means one can get rid of the problem of time having a beginning, in a similar way in which we got rid of the edge of the world. Suppose the beginning of the universe was like the South Pole of the earth, with degrees of latitude playing the role of time. The universe would start as a point at the South Pole. As one moves north, the circles of constant latitude, representing the size of the universe, would expand. To ask what happened before the beginning of the universe would become a meaningless question, because there is nothing south of the South Pole.
The beginning of the universe would be governed by the laws of science.

The picture Jim Hartle and I developed of the spontaneous quantum creation of the universe would be a bit like the formation of bubbles of steam in boiling water.

These would correspond to mini universes that would expand but would collapse again while still of microscopic size. They are possible alternative universes but they are not of much interest since they do not last long enough to develop galaxies and stars, let alone intelligent life. A few of the little bubbles, however, grow to a certain size at which they are safe from re collapse. They will continue to expand at an ever increasing rate.

The universe expanded by a factor of million trillion trillion in a tiny fraction of a second. Unlike inflation in prices, inflation in the early universe was a very good thing. It produced a very large and uniform universe, just as we observe. However, it would not be completely uniform. In the sum over histories, histories that are very slightly irregular will have almost as high probabilities as the completely uniform and regular history. The theory therefore predicts that the early universe is likely to be slightly non-uniform. These irregularities would produce small variations in the intensity of the microwave background from different directions. The microwave background has been observed by the Map satellite, and was found to have exactly the kind of variations predicted. So we know we are on the right lines.

The General Theory of Relativity and the discovery of the expansion of the universe shattered the old picture of an ever existing and ever lasting universe. Instead, general relativity predicted that the universe, and time itself, would begin in the big bang. It also predicted that time would come to an end in black holes. The discovery of the cosmic microwave background and observations of black holes support these conclusions. This is a profound change in our picture of the universe and of reality itself. Although the General Theory of Relativity predicted that the universe must have come from a period of high curvature in the past, it could not predict how the universe would emerge from the big bang. Thus general relativity on its own cannot answer the central question in cosmology: Why is the universe the way it is? However, if general relativity is combined with quantum theory, it may be possible to predict how the universe would start. It would initially expand at an ever increasing rate.

During this so called inflationary period, the marriage of the two theories predicted that small fluctuations would develop and lead to the formation of galaxies, stars, and all the other structure in the universe. This is confirmed by observations of small non uniformities in the cosmic microwave background, with exactly the predicted properties. So it seems we are on our way to understanding the origin of the universe, though much more work will be needed.

Despite having had some great successes, not everything is solved. We do not yet have a good theoretical understanding of the observations that the expansion of the universe is accelerating again, after a long period of slowing down. Without such an understanding, we cannot be sure of the future of the universe. Will it continue to expand forever? Is inflation a law of Nature? Or will the universe eventually collapse again? New observational results and theoretical advances are coming in rapidly. Cosmology is a very exciting and active subject. We are getting close to answering the age old questions. Why are we here? Where did we come from?   

A lively discussion took place on Steven Hawkins theory and alternative views.

Members of the group brought along items of interest which was shared with those present.