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Observation is an activity of a sapient or sentient living being (e.g. humans), which senses and assimilates the knowledge of a phenomenon in its framework of previous knowledge and ideas. Observation is more than the bare act of observing: To perform observation, a being must observe and seek to add to its knowledge. Observations are statements which are determined by using one of the five senses.^{[citation needed]} Observations aroused by self-defining instruments are often unreliable­¹. Such observations are hard to reproduce because they may vary even with respect to the same stimuli. Therefore they are not of much use in exact sciences like physics which require instruments which do not define themselves. It is therefore often necessary to use various engineered instruments like: spectrometers, oscilloscopes, cameras, telescopes, interferometers, tape recorders, thermometers etc. and tools like clocks, scale that help in improving the accuracy, quality and utility of the information obtained from an observation. Invariable observation requires uniformity of responses to a given stimulus, and devices promoting such observation must not give out rebellious output as if having "a mind (or opinion) of their own". In statistics, an observation, whether of a sample or the population, measures one or more properties (weight, location, etc.) of an observable entity enumerated to distinguish objects or individuals.

The accuracy and tremendous success of science is primarily attributed to the accuracy and objectivity (i.e. repeatability) of observation of the reality that science explores.

Contents 1 The role of observation in the scientific method 2 Example - The Big Bang 2.1 Observation: Hubble's redshift 2.2 Hypothesis about the abundance of the elements 2.3 Observation: the microwave background 2.4 Big Bang Hypothesis now corroborated 2.5 Current observations 2.6 Future observations 3 The role of observation in philosophy 4 See also

The scientific method includes the following steps:

1. 'observe' a phenomenon,
2. 'Hypothesize' an explanation for the phenomenon,
3. 'predict' a logical consequence of the guess,
4. 'Test' the prediction, and
5. 'review' for any mistakes.

Observation plays a role in the first and fourth steps in the above list. Reliance is placed upon the five physical senses: visual perception, hearing (sense), taste, feeling, and olfaction, and upon measurement techniques. It is therefore understood that there are always certain limitations in making observations.

In the 1920s Edwin Hubble of Mount Wilson observatory [1], 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.

Einstein correspondingly modified his field equation. See Cosmological constant

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. Enrico 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.

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.

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. Penzias and Wilson got the Nobel Prize for this discovery.

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.

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

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 with an open mind.

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 0-905945-19-0.

"Observe always that everything is the result of a change, and get used to thinking that there is nothing Nature loves so well as to change existing forms and to make new ones like them." Meditations. iv. 36. -Marcus Aurelius

Observation in philosophical terms is the process of filtering sensory information through the thought process. Input is received via hearing, sight, smell, taste, or touch and then analyzed through either rational or irrational thought. You see a parent beat their child; you observe that such an action is either good or bad. Deductions about what behaviors are good or bad may be based on no way preferences about building relationships, or study of the consequences resulting from the observed behavior. With the passage of time, impressions stored in the consciousness about many related observations, together with the resulting relationships and consequences, permit the individual to build a construct about the moral implications of behavior.

The defining characteristic of observation is that it involves drawing conclusions, as well as building personal views about how to handle similar situations in the future, rather than simply registering that something has happened. But according to J. Krishnamurti, observation does not imply drawing conclusions and building personal views. He stressed the non-accumulation of knowledge. Such an observation, he asserted, will make the mind free.

Observing can be part of the process of developing a morality.

• Naturalistic observation
• Observer effect
• Uncertainty principle
• Observational learning