Cosmology: Mass and Energy I

Interesting physics explained with many thought experiments and little math.
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Cosmology: Mass and Energy I

Post by 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.


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Re: Cosmology: Mass and Energy I

Post by 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.
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Re: Cosmology: Mass and Energy I

Post by juanacsanford » Sun Apr 14, 2013 5:05 am

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

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Re: Cosmology: Mass and Energy I

Post by eurbelts » Thu Aug 09, 2018 9:25 am

One of example of the energy conversion is the solar system driven clean and it is the pure energy taken from the sun.Sun is the mass storage of different gases like helium,nitrogen is the source for solar energy. With simple devices and in cheaper rate we can arrange the solar panels to generate energy is one of the renewable resource.