In the 20th century, physicist Dopper studied the sound phenomena and discovered the Doppler effect. The Doppler effect is observed whenever the sound source is moving with respect to an observer. Doffler effect is only a audible phenomena.The application of the effect is a redshift in astronomy, but to use the change of frequence is the same.

Scenabro effect, however, is a visible phenomena. When an object(or person) is moving away, then the length of the object is less than the inital length of the object. Until now, we cannot explain this phenomena mathematically or physically. If Doppler knew the length theory, he could explain the phenomena.

As the above figure shows, there is a difference between the mathematician's space and the physicist's space. Without time and light, the mathematicians determine the distance of space and always think that the geometrical size is the same in anywhere. Their assertions are correct.

But, physicists don't think that. Because they are not existing in abstract world but in real world. If the rod a moves with velocity v, after time t , the displacement of the rod A is d. the observer will see the more small rod A. These phenomena can be discoverd in the attendance road or in the train tour or in the harbor. The motorcycle passing by our side may be a good example that we can experience the Doppler effect and Scenabro effect at the same time. The stars in the night sky are too plentiful to try an example.

Also, you can find out Scenabro effect through a TV why these phenomenon occur? Using the length of general object L, we can theoretically explain the Scenabro effect.

As shown in figure, k is a ratio of natural contraction of the length. Length is continuosly contracted and its contraction is not a discontinuity. And the time must be substituted for the distance . Because time is only existing in physists's mind and they cannot see time.

If S approaches the infinite, then L=L'. This means that the length is always invariable in everywhere . This may be a mathematicain's thinking .But physicsts will have a question why it is seen as a small rod when the rod is at center.

As mentioned, the mathematicians don't consider the displacement d because there is no concept of relative motion. They think about the only one geometrical structure and its position. But, physicists always think about time and relative motion in space. They always have a difficulty that mathematicians cannot solve by themselves And Doppler effect dose not occur in the universe where there is no air. But Scenabro effect occurs wherever light is. Also, there is no Scenabro effect in light.