Expert: Ed - 4/21/2007

Question
QUESTION: according to POE mechanically acclerated field & gravitational field (GF) are equal , but for acc. system equations for free movement path of all objects emplyae that they can have only parabolic curves w.r.t co-or. where acc. is found,but for GF objects can follow other paths too (like hyperbolic etc.) then what's the equivalence btw them ?
ANSWER: Mohit,
I might be misunderstanding your question.  There are a few typos, and too many abbreviations, in the text of your question, for me to be sure what you're asking.  So, ask me again if I'm not being helpful.

For an object's orbit to be changed from a parabolic to a hyperbolic trajectory, an addition of kinetic energy is required.  Probably, the artificially accelerated systems that you have seen described in your textbooks are closed systems, which might not allow for additional kinetic energy, as it would violate basic assumptions.  However, in an open, celestial gravitational field, this may still be a possibility.
http://en.wikipedia.org/wiki/Escape_orbit

Does this answer your question?  I hope this is helpful.  Please tell me if you want to talk about this more, but if you do, be careful how you present your question.

Keep Looking Up,
--Ed




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QUESTION: SIR, Ist of all thanks for replying me.
Now I want to ask that now a days the hot big bang model is generally accepted model of beginning of universe.But it has some unanswered question like:
1. Why was early universe infinitely hot ? If it was, that means particles must have had very  very high energy so mustn't they have been escapen to infinity rather than remaining collected at one place ?
2. what was the cause of density flucation so that on expanding it accuired local irregularities like galaxies etc. ?
ANSWER: Mohit,

Your questions are very interesting.  Unfortunately, at the moment, the answer to both of them is "no one knows."  But there are good theories about the answers to both your questions.  I will try to get you started.

Well, the universe is still expanding, more and more quickly, so you could definitely say that particles from the early universe are doing exactly what you describe, that is, escaping to infinity.

The time when the conditions of the early universe were as you describe is called the Planck Era, or Planck Epoch.  If you are really interested in this topic, there is a probe being launched this year, to try to help us understand the subject of your question.  Look at this website sometimes, to understand better.
http://www.rssd.esa.int/index.php?project=Planck

Cosmologists are still trying to understand the reasons for primordial density fluctuations.  So, I can't answer your question with any real authority.  No one can.  At the moment, the most widely accepted theory to explain this phenomenon is called "cosmic inflation."  I recommend that you look at this article.  Scroll down to the part headed "Very early universe."
http://en.wikipedia.org/wiki/Structure_formation

You also might want to look at this website, for NASA's WMAP satellite.
http://map.gsfc.nasa.gov/m_uni.html

Keep Looking Up,
--Ed

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QUESTION: SIR,THANKS AGAIN FOR REPLYING
I want to ask that according to general relativity we have a equation that reads like this: c=c.(1+#/c.c) where # is gravitational potential. doesn't this eq. expels a concept that is very important to GR known as homogeneous gravitational field ?

Answer
Mohit,

To tell you the truth, I don't know if I can answer this.  I have not studied this math in a long time.  HOWEVER, please look at this website.  Scroll down, about 30 or 40 percent of the way down the website, and you will find a very, very, very detailed discussion of the problem.  Look for the paragraph that begins "Around 1911 Einstein proposed to incorporate gravitation..."
http://www.mathpages.com/rr/s6-01/6-01.htm

I am sorry, but I don't want to tell you something that would turn out to be wrong.  I will try to study this more carefully in the next few days, so if you want, you could ask me again then, and maybe (hopefully!) I could be more helpful.  Or, you could ask other AllExperts.

Keep Looking Up!
--Ed