Astronomy

The Impact Of The Big Bang

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We have seen how Karl Jansky found radio waves from an unexpected direction in space, which were subsequently attributed to cosmic sources. The invention and use of radar and its jamming during the Second World War led to the emergence of the radio telescope, which searched outer space for radio waves. Following the work of Prof Martin Ryle, it became clear that the radio sources he identified are not stars but galaxies. If the radio galaxies were found to be common at greater distances than the average galaxies, it would mean that they should be younger at the early stages of the evolution of the Universe. This would support the Big Bang theory.

According to the Big Bang theory, all matter and energy came into being some 15 billion years ago. In contrast, the Steady State theory assumes that the Universe has no finite beginning. Radio waves from outer space have played a key role in resolving the claims of the two theories.

In the United States, radio astronomy provided critical evidence in favour of the Big Bang theory. Bell Labs as a gesture of honouring Karl Jansky (who died at the young age of 44 in 1950), supported research in radio astronomy. Accordingly, Arno Penzias and Robert Wilson pointed their antenna to a region in the sky believed to be devoid of radio sources. They were surprised to hear a constant hiss. They first thought that it was due to the dropping of pigeons inside the horn of the antenna. They got rid of the birds but the noise continued.

It soon became clear that the radio noise was nothing but cosmic whispers, predicted by George Gamow and two others in 1947. The scientists had calculated that the Universe would undergo a transition, 300,000 years after the Big Bang, when the light waves would have a wavelength of one millimeter, which is in the region of radio (microwaves) in the spectrum. What Penzias and Wilson discovered in 1965 was nothing but the cosmic microwave background (CMB) radiation, an afterglow of the Big Bang, at minus 273ºC or 2.7 K. Calculations showed that a black body cooled to 2 K would emit such radiation. The two scientists got the Nobel Prize for the discovery.

The Big Bang theory seemed to be real, but not for Prof Fred Hoyle, who remained unconvinced. Ironically, he had given the term Big Bang for the theory more to mock its proponents than to celebrate its validity. Confronted with the proof of background radiation, he still pointed out that the aftermath of the Big Bang would be a smooth, bland and thin matter which could not have led to the formation of galaxies and life as we know it. The Big Bang would have simply blown away everything with no possibility of recovery! They Big Bang advocates were again at their wits’ end. They secretly hoped that the early Universe would show some differences in density.

It was at this stage that George Smoot of the Lawrence Berkeley National Lab (California) and John Mather of the Goddard Space Flight Centre, Maryland (both got the 2006 Nobel Prize), stepped in. Smoot was keen to find out whether the post-Big Bang Universe was indeed smooth or nor. He tried some experiments kept in balloons and gained permission to put some instruments on a U2 spy plane. The results were not satisfactory.

He soon realized that only a satellite above the atmosphere would be able to detect the tiny differences, if any, in the temperature and density of the Universe. He developed instruments that would measure the differences through their corresponding frequencies. He pointed out that the radiation from the regions that are denser than the rest would lose some energy in escaping the gravity and would come out in the longer wavelength, while the less dense areas would radiate at shorter wavelengths.

Smoot’s grand plan to launch his instruments on a satellite received the green signal in 1982 but the Challenger tragedy in 1986 left him with no hope of getting a rocket for launching the satellite in the near term. He and his colleague, John Mather had to downsize the satellite configuration to comply with the rocket available, coordinating the work of 1000 scientists and engineers.

At last NASA launched it in 1989. The satellite, called Cosmic Background Explorer (COBE) went into a polar orbit of the Earth in eleven minutes at 900 km. The differential microwave radio found the differences in the frequencies at the level of 1 in 100,000 parts, corresponding to temperatures in the range of a one hundred-thousandth of a degree! Only at this level, did the differences in the wavelength varied by 0.001 per cent.

George Smoot measured the small differences in the temperature of the cosmic microwave background radiation that envelopes all of us all the time and explained their significance in validating the Big Bang theory. The Nobel Prize for physics in 2006 rewarded the work of the two astrophysicists in tracing the impact of the Big Bang on the formation of galaxies.

cmbr

Smoot conveyed the discovery in dramatic terms. He told newspersons that at the time when COBE captured the image, the Universe was smaller than the smallest dot on the TV screen and less time had passed than it takes for light to cross the dot since the birth of the Universe! The point was that until then, all the microwave radiation appeared uniform. But COBE found ‘ripples’ in the fabric of space that indicated variations in temperature, which over the eons, led to the formation of galaxies observed today. The Big Bang model estimated that the Universe should be at least 10 billion years old and when it was 300,000 year old, the cosmic background radiation must have begun.

According to Professor Fred Hoyle and Professor Jayant Narlikar, the Universe was not created in one bang but from time to time in what may be called mini bangs! It is like a bucket of water under a running tap appearing full, though water is flowing in and out constantly. Narlikar maintains that the Big Bang theory lacks verifiable proof and is based on speculation as the early Universe is not transparent at all beyond a point in its evolution.

Ultimately, if one were to ask about the ‘matter’ before the Big Bang, one comes up against a wall of uncertainly. For some, the wall can be scaled only with the ladders of philosophy, religion and belief in a creator. Quantum science, where the common experience of cause and effect does not apply, may still offer a clue by envisaging the spontaneous emergence of a phenomenon, albeit for a fleeting moment.

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