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How do particles move ???

How do particles move ???. What about time ? What about their traces ?. What do we measure? What do we know ?. What does velocity mean ?. “How quickly an object moves from one point to another !” “The distance moved per unit of time.” “The rate of change of displacement.”.

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How do particles move ???

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  1. How do particles move ??? What about time ? What about their traces ? Dora Wagner HST 2001

  2. What do we measure? What do we know ? Dora Wagner HST 2001

  3. What does velocity mean ? • “How quickly an object moves from one point to another !” • “The distance moved per unit of time.” • “The rate of change of displacement.” Dora Wagner HST 2001

  4. Now the formula : • Dt : time interval • Ds : distance travelled Dora Wagner HST 2001

  5. How fast? How slow ? distance … the steeper, the faster ! time Dora Wagner HST 2001

  6. But nothing can go faster than light ! The speed of light is c = 300 000 000 m/s, and... … all the particles inside the bubble chamber were travelling nearly as fast as light ! Dora Wagner HST 2001

  7. Particles are interacting and decaying in a bubble chamber ! … are all particles recorded ? … are there some, which don’t leave traces ? Dora Wagner HST 2001

  8. … the particles… ? … where do they come from ? … where are they going to ? … how do they move ? … what do their traces look like ? … are they going straight or curved ? … how long do they stay ? Dora Wagner HST 2001

  9. What is the smallest interval of time you can imagine ? Dora Wagner HST 2001

  10. LOOK ! A photon travelled between the two marked points. The distance was exactly 11.5 cm! Then it materialized into an electron… …and a positron. Dora Wagner HST 2001

  11. Can you calculate the time taken by the photon? Ds = 11.5 cm Dt = ? Dora Wagner HST 2001

  12. REMEMBER ! c = 300 000 000 m/s, Ds v = ------- Dt Dora Wagner HST 2001

  13. Unbelievable ? Dt = Check your result Dora Wagner HST 2001

  14. Dt = 383 ps (picoseconds) … less than a billionth of a second ! Dora Wagner HST 2001

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