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IM Egdall

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  1. Maybe start with a community college and take some courses in remedial math and introductory physics to get you started. Then try to get into a 4-year college or university and major in physics. From there, you would do graduate work in astrophysics.


    And read, read, read everything you can get your hands on related to astrophysics. There are lots of books, web articles, and web videos on the topic. Try reading popular science books on the subject. This should give you an understanding of the basic concepts and terminology in the field.


    If you Google "cosmology" and "astrophysics" and "astronomy" etc, you'll find a great many sources from which you can learn. Be sure to look for sources which are from people from reputable universities, so you know what they are saying is legit. You can also join Twitter and go to Tweetchat and #cosmology, where you'll see a number of links on recent discoveries in the field.


    One thing I have learned which I wish I was told when I was young is that persistence is generally even more important than talent.


    I wish you the best of luck!


    No such line should exist if the source of the x-rays "bumps" have their basis in atomic transitions. As stated, it is just speculation as to what the cause might be. Galactic Black holes, stellar black holes, and neutron stars can be sources of gamma rays and x-rays. Most of this type of radiation is thought to be related to interactions of these entities or their jets, with matter. Such forceful entities as black holes and their jets, when interacting with matter, produce gamma rays for reasons that are still only speculative. My guess is that this OP x-ray radiation energy absorption lines are related to black holes or their jet interactions of some kind. Since these radiation "bumps" are observed within only a small range of energy levels, the source may be only one particular type of interaction the absorbs the x-ray radiation creating the observed absorption edges.


    I asked Esra Bulbul, lead author of the paper, whether the mysterious X-ray spectral line could be from black holes or neutron stars. She said:

    “We are sure (the emission line) is not caused by black holes (or neutron stars),” Bulbul said. “These are considered point sources. They look like dots in the image and are removed from the data. Even if some few remain, there is so much bulky gas that the black hole signals would wash out.”


    Full article: http://www.decodedscience.com/mysterious-emission-galaxy-clusters-dark-matter/48320

  3. Per E=mc2, energy is also found in matter itself.


    From Einstein Relatively Simple:


    "Consider a matter particle such as an electron, which has a certain amount of mass. According to Einstein, this mass is a form of energy. How much energy? Measure the mass of the particle and multiply it times the speed of light squared. The calculated energy is called the particle’s rest energy."

  4. Enthalpy stated "An idea becomes a physical law if its in a book . . . " Sorry, it isn't that simple.


    A scientific idea or theory is called a theory no matter how much or how little evidence there is to support it. The theory of general relativity, for example, has an enormous amount of evidence which confirms its predictions. String theory has no such evidence. Yet they are both called theories. And they both appear in a number of books.


    Plus we can find arguments against these and most any theory in a some book or scientific paper.


    No group of scientists meets to decide which theory is a physical law and which is not. We have to take science courses, read and study existing literature, and hear from experts to learn which theory is currently considered mainstream physics. And what is established physics today may not be in the future.

  5. As ajb said, locally is a small enough region of space-time. This is a region which is so small that the effects of gravity are negligible. So you can use special relativity here.


    Local space-time: Put simply, imagine you are inside a small enough elevator which is in free-fall above the Earth. You feel weightless. Any objects in the elevator fall at the same rate of acceleration as you do (ignoring air effects). So these object appear to be floating alongside you. It feels the same as if the elevator is in outer space with no gravity. This is a local region of space-time.


    Global space-time: Now imagine a second elevator at the same height above Earth but far away. The two elevators fall towards the center of the Earth. Thus they get closer together as they fall. Here the effects of gravity are observable. If you look from your elevator to the other, you see it getting closer to you over time. So you can tell that you are in a gravitational field and not floating in space. This is a global region of space-time. Over this region, general relativity is required.


    As I say in Einstein Relatively Simple, "gravity does not show its effects locally -- over a small enough space and time. The effects of gravity are only seen on a global scale."

  6. The new paper cited said "the throat closes slowly enough that its central region can be safely transmitted by a pulse of light." So maybe with a long enough wormhole, we could send a signal of some kind through it. Where do we find such elongated wormholes? And if we send this signal, will we get one back from beings in some other part of our universe, or from some other universe? Is fun to speculate.


    How this might helps with warp drive I have no idea.

  7. In science today, no one knows how the universe was created. But let me take a wack at explaining Krauss's proposal. (His theory is based on quantum gravity, which has no compelling evidence to support it. So its speculation):


    Per general relativity, the overall geometry of the universe can be open, flat, or closed.


    Per Krauss, there is only one type of universe where its “total energy is precisely zero.” This is a closed universe. In his theory, a closed universe can “appear spontaneously with impunity, carrying no net energy, Krauss writes.” But if the big bang began with a closed universe, it would have had a very short lifetime. “A closed expanding universe filled with matter will in general expand to a maximum size and then recollapse just as quickly.” This tiny closed universe would last perhaps about 10-44 seconds.


    But what if inflation occurred during the oh-so-brief period when our baby closed universe was still alive? Our closed universe would expand by a stupendous factor in a fraction of a second. As a result, the visible universe would now appears flat.


    We see a flat visible universe today. So, per Krauss, an initially closed universe made flat by inflation is a possible scenario for our universe — a universe created from nothing.


    See article below for more details:


  8. I have been less active on ScienceForums lately because I have been writing a book. It's called Einstein Relatively Simple: Our Universe Revealed in Everyday Language. The book is based on courses I teach at Lifelong Learning Institutes at several universities here in South Florida. The book is now published by World Scientific Publishing and available on Amazon, Barnes & Noble, etc.


    I think the book would be helpful to a number of forum members in explaining the basics of special and general relativity. I know there are forum rules on promoting a book, and the last thing I want to do is violate them. So please advise as to what I can and cannot do. Can I mention the book in a posting? Can I leave my website link at the end of a posting? Can I write about the book in my blog (It's Relative)? Are there other permitted ways to let members know the book is available?


    If you'd like to know more about the book and some early reviews, please check out my website: iramarkegdall.com

  9. I'd say, based on the evidence, that most astrophysicists support the idea of a flat observable universe. Again whether the entire universe beyond what we can see is flat is an open question.


    For example, in his book, A Universe from Nothing, Lawrence Krauss proposes that the entire universe may be positive curvature -- a closed universe. He says a closed universe has a total energy of zero, hence "a universe from nothing". Inflation expanded this closed universe exponentially, so what we observe in our tiny part of the universe today is nearly zero curvature or flat.


    Krauss says he based this idea on quantum gravity theory, which, as far as I know, has no supporting evidence. So I think his idea of a universe from nothing remains speculation.

  10. Back to the original link. Latest observations indicate "the universe appears to be quite flat." They are talking about the observable universe being flat. We can only see that part of the overall universe where light from stellar objects has had time to reach us.


    I think our best understanding is that there may be an overall non-flat curvature to the universe, e.g positive or negative. Inflation has enlarged the universe exponentially, so the part we can see appears to be very close to flat. An analogy is a balloon blown up to stupendous size. We ants on its surface see only a tiny portion -- which appears flat to us.


    So you cannot just assume the entire universe is flat. We just don't know.

  11. Thanks for the reply J.C MacSwell.


    Gravitationally what's the difference between relativistic mass and rest mass?

    A particle's rest mass, mo is a source of gravity or spacetime curvature. A particle's relativistic mass, mr is also a source of gravity. It is given by mr = m0 / sqrt (1 - v2/c2) where v is relative velocity and c is the speed of light. Here a particle's "apparent" mass approaches infinity as its relative velocity approaches the speed of light.


    However, as ajb points out, relativistic mass is not so popular with physicists. Relativistic momentum, p is preferred, where p = m0 v / sqrt (1 - v2/c2). Here a particle's mass remains constant and its momentum approaches infinity as its relative velocity approaches the speed of light. This method better represents the underlying physics.


    For gravity, it is best to think in terms of energy, which is a source of gravity:


    - A particle's rest energy, E0 is E0 = m0 c2.


    - A particle's total energy, E is E = E0 / sqrt (1 - (v2/c2). So its total energy also approaches infinity as its relative velocity approaches the speed of light. This is one reason why no particle with mass can travel at the speed of light.



  12. Dr. Houghton could be overstating the case, or she could be right. This may be one of those times when a new discovery is valid but doubted by the general community of physicists at first. If so, what a discovery!


    And I haven't heard of any other explanations for the data anomalies in the Planck CMB. I guess we'll just have to wait and see how this plays out.


    I would like to know some specific numbers on this, like what are the exact predictions and how do they compare numerically with actual measurements. (And what are the error bars in the measurements,)


    Anyone have any more info or thoughts on this?

  13. In her video, cosmologist and astrophysicist Laura Mersini-Houghton says the Planck Space Telescope has found evidence for multiple universes predicted by string theory. They are:

    • Cold spot where 1/6th of the Cosmic Microwave Background (CMB) is empty.
    • Suppression of the CMB at the largest scales.
    • Monopoles, dipoles, and quadripoles aligned with each other (the so-called axis of evil).

    If this is so, it has to be the greatest scientific discovery of the century.


    So why isn't there more about this in the news?


    Video link: How to Find a Multiverse http://iai.tv/video/how-to-find-a-multiverse


    Link discussing this issue http://www.math.columbia.edu/~woit/wordpress/?p=5907

  14. Quantum mechanics (QM) and general relativity (GR) have fundamentally different views of reality:


    For one thing, GR sees the world as deterministic. If you know an object's position and velocity (speed and direction), you can predict exactly where it was in the past and where it will be in the future (assuming nothing has disturbed it.)


    But QM is probabilistic. The more accurately you know a particle's position, the less accurately you can know its velocity, and vice versa. This is the Uncertainty Principle. So you cannot not know exactly where the particle was in the past or where it will be in the future. The best you can do is calculate the probability of it being at a certain place at a certain time.

  15. Dear David Levy: If you want your theories to be given credibility by cosmologists, you must make detailed predictions with specific numbers, which no other theory makes. And then you must wait for observations and measurements by independent scientists which confirm your predictions. Unless and until this happens (if ever), no amount of arguing by you will be effective. Its not personal, this is pretty much what all scientific theories go through.


    An example: Based on his and George Gamow's big bang theory, in the 1940s, physicists Ralph Alpher predicted a residual Cosmic Microwave Background (CMB) exists everywhere in the sky. And Alpher predicted its current temperature should be several degrees above absolute zero. In the 1960's, just such a CMB was found -- with a temperature of less than 3 degrees above absolute zero. (I talked about a number of additional specific predictions of the big bang theory which have since been verified as well.)

  16. It is not a matter of "believing" in the big bang theory or any scientific theory, it is how well it predicts what we observe and measure.


    The big bang theory coupled with inflation theory is our current best model of the origin and evolution of the universe. Why? Because it makes a number of predictions which are verified by independent observations, like the amount and abundance of helium and other light elements in our universe, the homogeneity of the universe, the expansion of the universe, the Cosmic Microwave Background (CMB) and the fluctuations in the CMB, the large scale structure of the universe, the evolution of galaxies, the age of stars, and a number of other more esoteric measurements. That is why it has such strong support among cosmologists.


    That is not to say there are no issues. The specifics of inflation theory, such as exactly how it started, how it came to an end, and whether it has or will happen again are still open questions.


    Per general relativity, the expansion of the universe is inherent in space itself. Space is unstable and cannot remain static. This means the distance between two points in space will stretch over time. But gravity overcomes this expansion force within galaxy clusters, so it is only over the enormous distances between clusters that space is expanding.


    There are two additional issues. The expansion of space is accelerating and no one knows why. So the source of this speed up is called "dark" energy. Plus there seems to be additional matter out there holding galaxies and clusters of galaxies together -- matter which does not give off light. Hence the term "dark" matter. No one knows what this dark matter is either.


    To me, the big bang plus inflation model is amazing. It does an incredible job predicting how our universe behaves and behaved in the past. But science is a continuing work in progress, and there is still much out there we don't know.

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