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  1. alexg

    Relativity and Speed of Light

    On the wiki page, there is one line stating that photons in superconductor have rest mass. However, there are no citations supporting that statment, and as far as I know, there are no transparent superconductors. All the wiki page can give is an upper limit for any mass, meaning no mass has...
  2. alexg

    What theories exist that predict our universe to be a star in a 'galaxy' of universes

    No, theories, as the word is used in science are not hypothesis. Theories are hypothesis which have been verified by observation and experiment. And I answered your question.
  3. alexg

    What theories exist that predict our universe to be a star in a 'galaxy' of universes

    No. All ideas about a multiverse are strictly hypothetical.
  4. alexg

    Speed of light in relative frames and acceleration

    An inertial frame is one which is not undergoing acceleration.
  5. alexg

    Proton decay

    Extremely sensitive experiments to detect proton decay have yet to find any.
  6. alexg

    Dark energy and the big bang

    No. There was nothing 'here' before the BB. Neither space nor time.
  7. alexg

    Relationship between expanding universe and time

    I would suggest The Inflationary Universe by Alan Guth. Again, he's just using an analogy to show how something (the universe) can be finite and unbounded.
  8. alexg

    Relationship between expanding universe and time

    That's where your error lies. It's not a model. It's an analogy. In this analogy, only the surface of the balloon is considered. It is using a two dimensional ANALOGY of the three dimensional universe. So for the purpose of the analogy, there is no inside of the balloon.
  9. alexg

    Expansion of space

    Andromeda and the Milky Way are approaching each other, and will collide in about 4.5 billion years. On any scale less than the local galactic supergroup (200 million lys) the effect of gravity overwhelms the force of expansion. It's only when you get outside the supergroup that you see...
  10. alexg

    New distant galaxy detected

    In the paper they say I think what they're saying is that the image they have is of a galaxy which is 'now' 500 million years old and which first formed at 200 million yrs.
  11. alexg

    No universe center why ?

    I would just like to comment that the balloon analogy seems to have caused more confusion than any other explanation of universal expansion. Of course, most of the confusion is because of people who don't know what an analogy is.
  12. alexg

    Highest expansion rate during inflation.

    If I'm remembering correctly, in the Guth-Linde version of inflation, the universe expanded by a factor of 1080 in the period between 10-45 and 10-35 seconds.
  13. alexg

    Is gravity 'weak' because it leaks into higher dimensions?

    The idea is not that there are 'other universes'. It's that unlike electroweak and strong force, gravity is able to propagate into the additional dimensions called for by M-theory. All those dimensions are part of our universe, but only gravity can move in those 'directions'. It would explain...
  14. alexg

    Why the black hole density is called the infinite density.

    Peter, a minor point, almost a diversion, but doesn't the Shell Theorem state that the gravity inside the earth remains the same until you reach the center? While there is more mass above you, you are closer to the rest of the mass on the other side, and it balances out.
  15. alexg

    CERN team claims measurement of neutrino speed >c

    Nothing in the Universe moves faster than rumor.
  16. alexg

    Relativistic Space Matter Flows over near light speed ships

    There is the idea of the Bussard Ramjet. Science fiction authors Larry Niven and Poul Anderson (in a great book called Tau Zero) used the idea. A very large, very powerful electromagnetic field is used to funnel ionized interstellar hydrogen...
  17. alexg

    Big Bang Theory and Matter

    Alpha radiation doesn't. Neither does Beta particles. But we're talking about fundamental particles being massless before the Higgs field. If they suddenly acquire mass, they must instantly drop below the speed of light.
  18. alexg

    Is it possible that speed of a gravitational waves are greater than c?

    When the Black Hole formed, the gravitational field was already there, permeating space. It doesn't go away because an event horizon formed.
  19. alexg

    Big Bang Theory and Matter

    If the fundamental particles were massless, doesn't that imply they were moving at c?
  20. alexg

    Gravitational force of antimatter

    I'm trying to find something on Cern's website, but so far all I've got is the press piece. Ah, here's the Cern piece. [Broken]
  21. alexg

    Gravitational force of antimatter

    Antimatter has been created and stored for as long as 16 minutes. If it did not react normally in a gravitational field, it would have showed up in the containment unit.
  22. alexg

    Contracting Universe?

    You also want to read on dark energy.
  23. alexg

    Is there zero gravity?

    The term 'zero gravity' is often used when referring to things in free fall. It is inaccurate.
  24. alexg

    Neutrino Vs. Black Hole

    Because while neutrinos interact very weakly with matter, they are still subject to gravity, just as photons are.
  25. alexg

    The Real Meaning of MPH

    Wow, that really perpetuates that dumb blond thing, doesn't it? And this guy married this girl? Well I don't suppose it was for her mind.
  26. alexg

    Why should the speed of light be the same in every frame of reference.

    If you're sitting in the moving car, and you measure the speed of light, and if your sitting on the particle and you measure the speed of light, you will get the same speed. This is because time dilates and length contracts in the moving frame of reference WHEN MEASURED BY A FRAME AT REST...
  27. alexg

    Medical Preventing a heart attack while shoveling snow

    Pay the kid next door to do it.
  28. alexg

    Are galaxies moving faster than the speed of light?

    It is. The temperature variations are small, but they're there. Yea, 100 posts.
  29. alexg

    The Food Thread

    I just had a pizza delivered, and I think it would have been tastier if I'd eaten the cardboard box. I'm just too damn lazy to make my own.
  30. alexg

    Is the universe going to die?

    Light moves through mediums other than the vacuum at less than c. When the beam emerges from the medium back into the vacuum, it travels at c. Lost energy shows up as a lowering of the frequency.