Cosmology: Mass and Energy I

Interesting physics explained with many thought experiments and little math.
User avatar
Science Officer
Posts: 113
Joined: Sat Dec 05, 2009 1:06 am
AKA: Abhi
Location: Michigan Tech

Cosmology: Mass and Energy I

Postby SsDd » Thu Nov 04, 2010 4:59 am

The lecture video is embedded below.

Additionally, slides used in the lecture are embedded below, or can also be downloaded directly from here

Questions after the lecture? Please feel free to post them in the same thread.

Click to play embedded YouTube video.


User avatar
Serendipitous Sleuthhound
Posts: 717
Joined: Mon Apr 21, 2008 4:51 am
Location: Redmond, WA

Re: Cosmology: Mass and Energy I

Postby alter-ego » Mon Nov 08, 2010 6:22 am

I think it is better to say that energy conservation is not defined (currently) over cosmological distance scales.

However, Wiki claims a stress-energy-momentum pseudotensor (Landau–Lifsh*tz pseudotensor) is a valid means of incorporating gravity energy-momentum into a total conserved "current" for a compact space-time (4-vector) region. I understand that an asymptotically flat space-time region (e.g. very far from a black hole) is a special case for energy conservation, but I don't know how non-flat or how compact a region is typically considered, and to what extent conserved current (energy conservation) calculations are approximations within the GR framework.

A very lively, and recent, blog discussion can be found here ( with UK physicist Phil Gibbs as the proponent for cosmic scale "energy" conservation. I'm not claiming Phil is right, as I understand this site is controversial because anything goes here(?). Though the discussion is interesting and stimulating (includes some math). It makes me wonder whether there is further understanding and interpretation to be had within the classical theory of GR.
A pessimist is nothing more than an experienced optimist

Posts: 2
Joined: Sat Apr 13, 2013 2:49 am

Re: Cosmology: Mass and Energy I

Postby juanacsanford » Sun Apr 14, 2013 5:05 am

Would it be fine if I could use some of your slides for my school presentation?

Return to “Classroom: Extraordinary Concepts in Physics”

Who is online

Users browsing this forum: CommonCrawl [Bot] and 0 guests