8.962  General Relativity

Dear class ---

With apologies for the delay (one of the TAs fell ill), all psets have now been graded.  I will turn these into letter grades and submit to the registrar later today.  Please check to make sure that there are no errors that you know of.

We will make arrangements to get the graded psets back to you (should you want them) later next week.

Happy weekend,

scott

Dear class ---

The solution to problem set 11 has now been posted.  I meant to do this earlier today, but had a packed afternoon.

The remaining psets will be graded soon, and final grades determined soon after that.  Please make sure that the grades in the gradebook are accurately, and let us know as soon as possible if there are any concerns (some of you already have sent in minor corrections and overlooked psets that were handed in electronically earlier -- thank you for this).  I will send a final message once that is all done.

scott

Dear class --

Please note that problem 2(b) should read "You should be able to convince yourself that circular orbits satisfy $V_{\rm eff} = \hat E^2$, $\partial V_{\rm eff}/\partial r = 0$"; it should be obvious by inspection that $V_{\rm eff} = 0$ is a nonsensical condition.

The posted PDF has been updated to reflect this correct.  Many thanks to Bidisha Sen for catching this error!

scott

Dear class ---

I've at last had some time to write up a page of notes explaining a better way to think about what happens to light as it propagates from some radius deep inside the Schwarzschild spacetime to an observer far away.  See under "Materials / Readings".  (Note, I'm sending this message a second time, since I updated these notes to add some additional points related to what the "energy" of the beam means.)

Many thanks to Enrique Mendez for the question which inspired this re-thinking, and to everyone for your patience as I waded through an extremely dense week to get to the point where I could write this up.

scott

Dear class --

Following up on my last announcement: this is a packed time for faculty as well as students!  Today is particularly packed, with a lot happening during the day followed by an evening event for physics faculty.  My wife is away on a work trip, so I'm (temporarily) single parenting.  I need to leave promptly following today's lecture in order to go home, pick up my daughter from her after school program, make dinner for her and the babysitter, change into fancy-ish clothes, then return to Cambridge for the event.  It will be fine -- but I've got essentially no slack in the schedule.

As such, I will not be able to chat with students like I normally do after class.  Please save your questions until we can talk again next week; I'm much less constrained then.  (Speaking of which -- Enrique Mendez asked a very good question in the last lecture about how energy is defined when we are a "strong field" region, near r = 2GM.  I will be posting a page of notes addressing this question soon -- but need another day or so before I will have time to put them together.)

cheers,

scott