The uncertainty relation does not refer to the past; if the velocity of the electron is at first known and the position then exactly measured, the position for times previous to the measurement may be calculated.
Interpretation
This quote explains the concept that knowing an electron's position does not retroactively affect its velocity in the past.
Werner Heisenberg's statement highlights a key aspect of quantum mechanics known as the uncertainty principle. It emphasizes that while we can measure and know certain properties of particles, such as the position of an electron, this does not imply knowledge about its past states or velocity before the measurement, illustrating the limits of our knowledge in the quantum realm.
In practice
In a lecture on quantum physics, to explain the nuances of the uncertainty principle.
Although the theory of relativity makes the greatest of demands on the ability for abstract thought, still it fulfills the traditional requirements of science insofar as it permits a division of the world into subject and object (observer and observed) and, hence, a clear formulation of the law of causality.
It was about three o'clock at night when the final result of the calculation [which gave birth to quantum mechanics] lay before me ... At first I was deeply shaken ... I was so excited that I could not think of sleep. So I left the house ... and awaited the sunrise on top of a rock.
It is generally believed that our science is empirical and that we draw our concepts and our mathematical constructs from the empirical data. If this were the whole truth, we should, when entering into a new field, introduce only such quantities as can directly be observed, and formulate natural laws only by means of these quantities.
When I meet God, I am going to ask him two questions: Why relativity ? And why turbulence ? I really believe he will have an answer for the first.
The end of the First World War had thrown Germany's youth into great turmoil. The reins of power had fallen from the hands of a deeply disillusioned older generation, and the younger ones drew together in larger and smaller groups to blaze new paths or, at least, to discover a new star to steer by.
The Same organizing forces that have shaped nature in all her forms are also responsible for the structure of our minds.
Nuclear energy, in terms of an overall safety record, is better than other energy.
The biogeographic evidence for evolution is now so powerful that I have never seen a creationist book, article, or lecture that has tried to refute it. Creationists simply pretend that the evidence doesn't exist.
Nuclear power plants must be prepared to withstand everything from earthquakes to tsunamis, from fires to floods to acts of terrorism.
You can make a stack high enough to reach the moon and back, and only then will you have used your 100 billion hamburgers. This is terrifying news to cows.
The laws of Congress and the laws of physics have grown increasingly divergent, and the laws of physics are not likely to yield.
Perhaps some day in the dim future it will be possible to advance the computations faster than the weather advances and at a cost less than the saving to mankind due to the information gained. But that is a dream.
Subscribe for the occasional hand-picked quote. No noise.