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Relativity/Anti gravity and expansion of space


I would like to 1.)clarify what is meant by anti-gravity, 2.)If anti-gravity exist,3.)clarify the meaning of space-time expansion. My na´ve understanding is that anything that has mass/energy gets accelerated and move through space-time towards each other as a result of space-time curvature. So I would think of anti-gravity as something that do the opposite, that is perhaps things with mass/energy accelerating in opposite direction as a result of anti-gravity field, if such things exist. Regarding dark energy, from what I've read from lay people writings, it is responsible for the expansion of space. So is it right for me to say that the stuff in space is not moving apart as a result of the expansion, just that the space in between the stuffs is being "stretched" or created(?) and hence the observation that distance between galaxies increases? Oh, another thing is that when we talk about big crunch, are we talking about just the mass being pulled together or does it includes space-time(space?) being pulled together as well? If so, does that mean that gravity result in space-time being pulled together? There's like a lot of things I'm asking. Thanks a lot in advance.

ANSWER: Ken, there is no anti-gravity.

---------- FOLLOW-UP ----------

QUESTION: Are you really here as an expert? Your answer is very disappointing. I understand that a lot of what I've said must be filled with misconceptions, but your reply is downright disrespecting me because it seems like you don't even care to explain anything. I am vaguely aware that anti-gravity does not exist, but there is such a concept as anti-gravity which is worth thinking about. I am not that uneducated, in fact I have a degree in mathematics and what you did is a disservice for people like me who are genuinely interested in the subject but have limited formal education in that area.

Ken, I am sorry that I seemed disrespectful. It is just that I have nothing to contribute on the subject of anti-gravity.  I do not know of any serious work on the subject.  It seems to be a subject of discussion in science fiction.

There is a phenomenon in the behavior of the universe in that the universe seems to be expanding, and people have hypothesized the existence of "dark matter" and "dark energy" to explain it, but I know of no successes in these fields that I can explain to anybody. And they do not fall into the category of anti-gravity as far as I know.

If you have any less exotic questions, I am happy to discuss them with you.  


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Uncle Ben


I can answer questions regarding Einstein's Theory of Relativity, particularly in Special Relativity. I will not answer homework questions or mathematical problems that require special symbols.


I have taught physics at the college level, undergraduate and graduate, for many years including Special Relativity. I have taught at Johns Hopkins, Case-Western, and MIT. I have also served as a staff member of the Commission on College Physics, which was supported by the National Science Foundation to recommend improvements in the curriculum of college physics departments in the US. I am also the author of a textbook titled Vector Calculus, which was used at MIT in the teaching of electromagnetic theory and relativity. My research interests were mainly in solid state physics, especially the properties of metals at low temperatures. I am listed in the publication known as American Men of Science.

I have dozens of papers published in the Physical Review and in the American Journal of Physics.

I hold a Ph.D. degree in physics from the Johns Hopkins University.

Past/Present Clients
Johns Hopkins University, Case-Western Reserve University, Massachusetts Institute of Technology, Empire State College, Georgetown University, Commission on College Physics, and UNESCO.

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