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What about time ? What about their traces ?
How do particles move ??? What about time ? What about their traces ? 5/6/2019 Dora Wagner HST 2001 Dora Wagner
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What do we measure? What do we know ? 5/6/2019 Dora Wagner HST 2001
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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.” 5/6/2019 Dora Wagner HST 2001
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Now the formula : V = Ds ------- Dt Dt : time interval
Ds : distance travelled 5/6/2019 Dora Wagner HST 2001
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… the steeper, the faster !
How fast? How slow ? distance … the steeper, the faster ! time 5/6/2019 Dora Wagner HST 2001
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But nothing can go faster than light !
The speed of light is c = m/s, and... … all the particles inside the bubble chamber were travelling nearly as fast as light ! 5/6/2019 Dora Wagner HST 2001
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Particles are interacting and decaying in a bubble chamber !
… are all particles recorded ? … are there some, which don’t leave traces ? 5/6/2019 Dora Wagner HST 2001
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… 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 ? 5/6/2019 Dora Wagner HST 2001
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What is the smallest interval of time you can imagine ?
5/6/2019 Dora Wagner HST 2001
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Then it materialized into an electron…
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. 5/6/2019 Dora Wagner HST 2001
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Can you calculate the time taken by the photon?
Ds = cm Dt = ? 5/6/2019 Dora Wagner HST 2001
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REMEMBER ! Ds v = ------- Dt c = 300 000 000 m/s, 5/6/2019
Dora Wagner HST 2001
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Unbelievable ? Dt = Check your result 5/6/2019 Dora Wagner HST 2001
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… less than a billionth of a second !
Dt = 383 ps (picoseconds) … less than a billionth of a second ! 5/6/2019 Dora Wagner HST 2001
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