We kick off our informal video series on The Biggest Ideas in the Universe with one of my favorites — Conservation, as in “conservation of momentum,” “conservation of energy,” things like that. Readers of The Big Picture will recognize this as one of my favorite themes, and smile with familiarity as we mention some important names — Aristotle, Ibn Sina, Galileo, Laplace, and others.
The Biggest Ideas in the Universe | 1. Conservation
Remember that for the next couple of days you are encouraged to leave questions about what was discussed in the video, either here or directly at the YouTube page. I will pick some of my favorites and make another video giving some answers.
Update: here’s the Q&A.
The Biggest Ideas in the Universe | Q&A 1 - Conservation
Dear Sean,
I’m a graduate student in physics and since last night that I heard in your Q&A video (38:30) that energy of a quantum system+ measuring device is not conserved after measuring the location of the system , you could say I’m restless!!:)) the whole system is classical and should obey the energy conservation principle!!! I wish I could see some calculations. what do you mean? In a more technical term I guess you are saying that when we are not in a position Eigenket and we measure the position, the state of the system changes and so does the expectation value of Energy. that’s OK, but how do you calculate the change of energy in the apparatus? if you write down an interaction hamiltonian the changes obey schrodinger’s Eq. and can’t account for the measurement, unless you are using some revised version like GRW’s…
If there’s anything writen about what you said please tell me about it.
Many Thanks,
Mehdi
Paper is being written and coming soon!