Observation

For the railroad use of the term observation, see observation car.

The role of Observation in the Scientific Method

The scientific method includes the following steps:

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• 'observe' a phenomenon,
• 'Hypothesize' an explanation for the phenomenon,
• 'predict' a logical consequence of the guess,
• 'test' for the prediction, and
• 'review' for any mistakes.

Observation takes place in the first and fourth steps. Reliance is placed upon the five physical senses: seeing, hearing, tasting, feeling and smelling, and upon techniques for measuring. Thus, it is understood that there are limitations in making observations.

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Example: The Big Bang

In cosmology, the original observation was that we seem to live in a firmament.

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The sun seemed to rise and set, travelling on a huge transparent bowl which was set around our world.

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Various paradigms which explained our world, came and went, but the universe seemed static. Even Einstein believed this.

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Observation: Hubble's redshift

In the 1920s Edwin Hubble of Mount Wilson observatory http://www.mtwilson.edu/his/art/g1a4.htm, observed that the galaxies, on the whole, were moving away from each other. Thus we live in an 'expanding universe'. The speed of expansion was apparently constant (Hubble's 'constant'), as evidenced by light from the galaxies, which was doppler-shifted in color toward the red side of the spectrum.

Related Topics:
1920s - Edwin Hubble - Mount Wilson observatory - Expanding universe - Hubble's 'constant'

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Einstein correspondingly modified his field equation. See Cosmological constant

Related Topics:
Field equation - Cosmological constant

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Hypothesis about the abundance of the elements

If the universe is expanding, then it must have been much smaller and therefore hotter and denser in the past. George Gamow hypothesized that the abundance of the elements in the Periodic Table of the Elements, might be accounted for by nuclear reactions in a hot dense universe. He was disputed by Fred Hoyle, who invented the term 'Big Bang' to disparage it. Fermi and others noted that this process would have stopped after only the light elements were created, and thus did not account for the abundance of heavier elements.

Related Topics:
George Gamow - Fred Hoyle - Big Bang - Fermi

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Gamow's prediction: One consequence of this hypothesis was a 5–10 kelvin black body radiation temperature for the universe, after it cooled during the expansion.

Related Topics:
Black body - Radiation

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Observation: the microwave background

In 1965, Arno A. Penzias and Robert W. Wilson announced that microwave radiation was surrounding us in all directions, at a level which was of the order of magnitude predicted by Gamow.

Related Topics:
1965 - Arno A. Penzias and Robert W. Wilson

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Penzias and Wilson got the Nobel Prize for this discovery.

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Big Bang Hypothesis now corroborated

After this piece of evidence, Gamow's hypothesis was now more likely. The age of the universe is currently estimated to be 13.7 billion years after the Big Bang.

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Current observations

More refined measurements, such as those from the COBE satellite, are best fit by radiation from a pure 2.7 kelvin black body.

Related Topics:
COBE - Black body

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Future observations

It is, of course, entirely possible that observations made in the future may enable a different understanding. People of the future, looking back on the Big Bang theory may, perhaps, regard it with as much derision as the people of today regard the apparent geocentric universe of previous observations. All that is possible is to keep looking at the evidence as it comes in.

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Reference: J.A. Peacock, A.F. Heavens, A.T. Davies (eds.), 1989. Physics of the Early Universe. Proceedings of the 36th Scottish Universities Summer School in Physics (SUSSP). ISBN 0905945190.

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