Eduardo Guerras Valera

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2,240 reputation
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location Spain
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visits member for 1 year, 6 months
seen Nov 25 '13 at 13:37

I am an astrophysicist who loves GR and Cosmology, with an additional amateur interest in Particle Physics.


Apr
9
awarded  Nice Question
Mar
23
awarded  Nice Question
Jan
7
awarded  Notable Question
Oct
29
awarded  Self-Learner
Oct
28
comment Intuitively, how can the work done on an object be equal to zero?
@annav, Thanks (+1) Yes, I know it is cold. It is supposed to have decoupled from the other components when the temperature of the universe was in the order of MeV and after that, it has no means of loosing energy by interacting with anything, it is only affected by the increase of volume due to the expansion (you surely know the details way much better than me). I erased the question because I was a bit ashamed, I realized it was very stupid. I even had assisted to a whole winter school about LCDM cosmology a few years ago. I don't know, I am tired, and mindlessly posed a stupid question.
Oct
28
comment Classical EM neglects electron recoil?
I'm sorry I use this unorthodox way to communicate with you. I erased my question about dark matter, because your comment made me remember and I realize how stupid the question was. But I wanted to tell you thanks for that comment. In fact, you are right about your guess. I even assisted to a whole winter school a few years ago about cdm. I have written that question in a weird moment of confusion, being tired.
Oct
28
awarded  Disciplined
Oct
27
comment Intuitively, how can the work done on an object be equal to zero?
@MikeDunlavey and probably -1 for my horrible english, ha ha ha
Oct
26
comment Intuitively, how can the work done on an object be equal to zero?
@MikeDunlavey I think a heavy object leant against the wall is a better example. When you are pushing, there is chemical work inside your muscles. In fact you can exercise and become stronger by means of isometric exercises, with no movement at all (I think Qmechanic was thinking about something in that sense). That is why, if you push hard against a wall, you become tired. There is (another kind of) work involved.
Oct
26
comment Dark Energy Explanation Found
The source of gravitational forces is the mass in Newtonian gravity. It is somehow "natural" for you to think that after a particle is annihilated, gravity abruptly "disappears". But in General Relativity (where the words "curved spacetime" make sense) the source of gravity is not only mass, but a more complex entity called the energy-momentum tensor that takes into account not only mass, but also flux of energy from one place to another. Thus, the energy released when a mass "disappears" produces no abrupt "vanishing" of gravity.
Oct
25
revised Intuitively, how can the work done on an object be equal to zero?
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25
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25
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Oct
25
answered Intuitively, how can the work done on an object be equal to zero?
Oct
21
awarded  Revival
Oct
19
awarded  Yearling
Oct
3
comment Way to become a physicist
@LarryHarson You would win a lot of personal satisfaction by picking up one of McMahon's book, paper and pencil and go through it, instead of showing disrespect for them. They are the only thing around that can take somebody who is not a theoretical physicist into some depth of knowledge. There is absolutely nothing but McMahon books to fill the gap between pop science and high-level books like Polchinski or Peskin&Schroeder. You may find more convincing this Lubos review on String Theory Demystified if you want a reputed physicist point of view
Oct
2
comment Is “A Brief History of Time” still up to date?
@SystemDown That dog is part of an effort to explain something impossible to explain without maths and in such a short text. The "Six Easy Pieces" or "The Character of Physical Law" by Feynman are much more meaninful and enlightening things to read for the non-physicist than Hawking's "Brief History of Time", no matter how much I admire how courageous as a person and brilliant as a scientist Hawking is. But the book seemed to me nonsense.
Oct
2
comment Is “A Brief History of Time” still up to date?
Horrible book (some highlights are the yellow-press alike personal critics against Newton in the appendix or the bi-dimensional dog, to name just a few). If you want to enjoy some popular science books, read "QED - The Strange Theory of Light and Matter" by Feynman or "Relativity - The Special and the General Theory" by Einstein (though obviously much older than 25 years), or "A Short History of Nearly Everything" by Bill Bryson. But the intended scope of "A Brief History of Time" is too ambitious, and the resulting product is nearly unreadable.