Everything about Astronomy & Astrophysics.

• Prudvi Tej

  What will be there in the absence of universe?

  if we pour the tea out of a tea cup then, the cup would be empty. if we destroy the cup the place occupied by the cup previously would be now filled up with air, if that air is evacuated vaccume isif we pour the tea out of a tea cup then, the cup would be empty. if we destroy the cup the place occupied by the cup previously would be now filled up with air, if that air is evacuated vaccume is created. NOW JUST LIKE THIS WHAT WOULD BE THERE IN THE ABSENCE OF OUR UNIVERSE? IS IT THERE INSIDE SOMETHING OR IS IT THE EVERYTHING?
• Anirudh Kumar Satsangi

  Did the universe originate from 'nothing' or from 'something'?

  If it originated from nothing then it goes against the Law of Conservation of Mass and Energy and if it originated from something then what was the 'something'? Whether it was infinite expanse ofIf it originated from nothing then it goes against the Law of Conservation of Mass and Energy and if it originated from something then what was the 'something'? Whether it was infinite expanse of gravitational force field?

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    Rauli Laakso replied

    Dark energy is created from nothing: the universe expands, but the energy density of dark energy is a constant.

    1 hour ago
• Josjo Kodian

  Is a multiverse possible?

  What do people think?

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    Louis Brassard replied

    Our Universe has expanded dramatically. The existence of other galaxies was confirmed only recently, although it was speculated a long time before that by the first atomists. Now the cosmologicalOur Universe has expanded dramatically. The existence of other galaxies was confirmed only recently, although it was speculated a long time before that by the first atomists. Now the cosmological microwave background is the further we can see with our instruments. But theoretical physics allows us to see further away. But theoretical physics is far from being completed and unified. Different branches of theoretical physics perceives different multiverses. One of the problem with cosmology is the fine tuning of the fundamental constant of physics for the evolution of life. One of the solution for that strange fine tuning has been to assume that there are so many other universes, all with different fundamental constants, so that it is not surprising we end up in the Universe where life exist. I find such reasoning unconvincing. I think that the fine tuning problem arises from having a deterministic model which has to explain everything in terms of initial conditions. The more you have to explain the more fine tuning become your initial conditions. A emergent based cosmic model would avoid the fine tuning problem at the same time of including the evolution of the laws of nature within the model.

    1 day ago
• Mattia Galiazzo

  Why Einstein-theory should not be wrong?

  (open question to "open" points of view: as to say again: relativity.......)

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    Louis Brassard replied

    General Relativity (GR) is our best model of gravitation. It fails to describe the rotation of galaxies and the attraction between galaxies in local groups. In order to explain these gravitationalGeneral Relativity (GR) is our best model of gravitation. It fails to describe the rotation of galaxies and the attraction between galaxies in local groups. In order to explain these gravitational phenomena within GR framework we had to assume the existence of dark matter. General Relativity predicts the expansion of the Universe at a constant rate. Ten years ago we found out that the expansion is accelerating. To explain this phenomena within GR we assumed the existence of dark energy. So far we have found no experimental evidences of dark matter! We keep looking! It is also known that quantum mechanic is incompatible in fundamental ways with GR and most physicists think that it will be eventually replaced by a quantum gravity theory. A lot of theoretical work in done in order to eventually build a quantum gravity theory but we are only at the stage of digging the fondations. For now we are stuck at fixing the old car as best as we can!

    3 days ago
• Sruthi Sasi

  Can anyone explain in simple terms the concept of spacetime?

  Can gravitational waves be detected or are they just a concept ?

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• Judit Camacho

  Could dark matter originate from normal stars in unknown nuclear processes, before being released?

  Really I can't see any other possible source for it, unless these dark particles have been present since the origin of the Universe. What does the scientific community say about this? What isReally I can't see any other possible source for it, unless these dark particles have been present since the origin of the Universe. What does the scientific community say about this? What is more, I have heard about hydrogen plasma (core of most stars), which under certain conditions may occupy abnormal level states such as hydrinos, which break actual physics laws.
• Judit Camacho

  Has the quantity of stellar mass of the Milky Way changed much since its formation?

  I just was wondering how much the quantity of stellar mass (still burning hydrogen) has changed since its formation, from the different parts of our galaxy: disk, halo, bulge, solarI just was wondering how much the quantity of stellar mass (still burning hydrogen) has changed since its formation, from the different parts of our galaxy: disk, halo, bulge, solar neighborhood. Some stars explode but they are the fewest, some others interact but they are the fewest - is this correct?
• Jamahl Peavey

  Why does Hawking attack philosophy and endorse M-Theory?

  Scientist should not be selective about what is considered philosophy. M-Theory is a philosophy and Hawking's work is also a philosophy. Hawking Radiation has never been detected and most likelyScientist should not be selective about what is considered philosophy. M-Theory is a philosophy and Hawking's work is also a philosophy. Hawking Radiation has never been detected and most likely never will.

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    Robert Toshiyuki Morrell replied

    You cannot test what you cannot hypothesize so if you cannot dream up a new idea or new "philosophy" as you put it, you cannot design an experiment to even attempt to prove it. Let me explainYou cannot test what you cannot hypothesize so if you cannot dream up a new idea or new "philosophy" as you put it, you cannot design an experiment to even attempt to prove it. Let me explain something. Say you work for intel and currently they have 22nm processors. If you wanted to create 16 or 12 nm processors would that not be philosphy since it does not exist and we do not know if this is possible because we have not tested it? (Understand that unless you have built it you cannot say with 100% certaintly, in the scientific perspective that it is possible, only that it may be or should be because there may be a variable you are taking into account). If a rocket in space can already travel at a given speed what is not to say there is a better way to make the rocket move? Say bending space? Dont focus on the problem as much as the idea behind the point im trying to make. Now as an engineer you typically dont invent new ideas. If you did, you would have created a theoretical idea until you have built it. Engineers along with many of fields of science tend to think in a forward or progressive perspective. Forgive me if i sound condescending, it is not my intention. We tend to think of how to improve something instead of how to create a better way. If i need to get to the other side of the wall, why should I build a better vehicle to crash through when I could simple walk around it? The difference between these two is that "walking around it" requires applying a methodology that does not improve one we currently use. Its like trying to scale a wall and as an engineer you would build a device to lift you to the top, then the theoretical physicist says, what if?, what if there was a staircase a mile away from us that we couldnt see? If we are to improve science we must think in a manner that promotes the finding of new ideas. If you say string theory or M theory will never be proven, remember we once said we would never travel in space, or carry a handheld computer, or communicate with someone on the other side of the world. These things were once theoretical. Transmit information using radio waves? ya right! thats impossible! In all areas of science passion and goals drive progress and the theoretical fields provide that much needed ideology so that we have a sense of direction. The reason those fields seem like they are drying up is because these fields are not revenue driven and we are unfortunately cursed with that necessity of making money. Forgive my babble everyone but I hope I have made my point.

    Apr 13, 2012
• Arun Upadhyay

  There has been search for unified field theory for past 100 years. But it has proliferated into at least 22 theories including five 10-dimensional string-theories. After Godel's IncompletenessThere has been search for unified field theory for past 100 years. But it has proliferated into at least 22 theories including five 10-dimensional string-theories. After Godel's Incompleteness Theorem in 1931, should we not search 2 or 3 complementary theories? Another question is that how many dimensions are sufficient to describe universe? There is some answer in Vedic concept.

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    William Jackson replied

    "After Godel's Incompleteness Theorem ... should we not search 2 or 3 complementary theories? " ... how many dimensions are sufficient to describe universe? -------------- Godel's Theorem only"After Godel's Incompleteness Theorem ... should we not search 2 or 3 complementary theories? " ... how many dimensions are sufficient to describe universe? -------------- Godel's Theorem only applies to axiomatic systems (computable), - assuming that we are 'stuck' with axiomatic descriptions, - perhaps we should make use of several alternative geometries, - selecting according to context. - (there is a possibility of a non axiomatic description.) ---------------- Geometric Algebra (GA) can express much of physics in a framework of 4 'complex vector' dimensions, - however, GA is not a conformal geometry, and falls short in certain contexts. The more comprehensive, Conformal Geometric Algebra (CGA), - makes use of a framework of 5 'complex vector' dimensions. More work is required to 'fit' physics in all contexts to these frameworks; - from a practical engineering perspective, GA is neat and tidy, and appears sufficient, - but, in contexts outside the classical domain (theoretical physics), - perhaps CGA will be more appropriate. --------------- Go here for formal descriptions: https://en.wikipedia.org/wiki/Geometric_algebra http://en.wikipedia.org/wiki/Conformal_geometric_algebra

    21 days ago
• Geethanjali m.a.

  Is it possible to destroy the asteroid in space itself? If it is, how can we do this?

  i came across about the asteroids and their chances of drastic effects to our planet in nearby (or far away) future.Additionally i read about the techniques which handled by several spacei came across about the asteroids and their chances of drastic effects to our planet in nearby (or far away) future.Additionally i read about the techniques which handled by several space organizations including NASA to combat the effects.These things are well known to you....but i have small doubt regarding this.,.since we have cloud of satellites over globe,why we not able study these celestial objects in an efficient manner?even the techniques which handled by NASA didn't completed the desired task.is it possible to destruct the asteroids in space itself,if it so what are the drawbacks?

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    Dr Dean Kos replied

    deflection will not work for larger type objects simple it takes years in advance to work in this design when time that it is discovered is short at best a few years at most let alone the speed itdeflection will not work for larger type objects simple it takes years in advance to work in this design when time that it is discovered is short at best a few years at most let alone the speed it travels at not going to work, and as far as smaller objects left over scattered over the globe would be just as bad as the big event if it hit even small blocks 30 k wide that will expolde in the atmos will cause mass fire balls over the globe and you see were thats going ! But it has been noted that NASA will try to land on a large astro in due time to monitor its projectory to earth but we yet have the tech to see more than a few years in advance of the object let alone devert it, blast it, or have the time to do much about it if it is on its way with earth let alone you or me geting told about it in the first place ! So at this stage in answer too your Q. no i dont think we can at this stage in 2012

    Apr 24, 2012
• Judit Camacho

  Good Initial STELLAR functions for Our Galaxy? How accurate are they?

  There are different models, which model is better? The Initial Mass Function (IMF) is an function which gives us the mass of the stars when they were formed. The Star Formation Rate (SFR) gives usThere are different models, which model is better? The Initial Mass Function (IMF) is an function which gives us the mass of the stars when they were formed. The Star Formation Rate (SFR) gives us the age of the born star. To my knowledge, any IMF or SFR is derived from the observed present-day mass function of single field stars in the solar neighborhood, and it is assumed to be invariant with time, space and environment. Although these assumptions are clearly unjustified, the resultant IMF can be tested by means of detailed models of chemical evolution. I am working on Monte-Carlo simulations to find out the history of observed stars, so it requires of initial conditions such the IMF and SFR. According to Paul Crowther, actual models based on the Kroupa's function (obtained from clusters) would lead into error to certain masses if I applied it to Milky Way, since the truly IMF for Our Galaxy would have different slope. Can I say that higher masses are underestimated? How reliable can these Initial Stellar function be?.

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    Shylaja Bangalore replied

    Kroupa 's paper supersedes all previous discussions.

    Apr 24, 2012
• Arpit Banka

  What actually is a black hole?

  A black hole is present in center of each galaxy . What it is isn't perfectly known yet...

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    Judit Camacho replied

    Difficult definition for something what really we do not what is inside, many mathematical suggestions but little physics...the only thing that can we be sure is get by means of measuring theirDifficult definition for something what really we do not what is inside, many mathematical suggestions but little physics...the only thing that can we be sure is get by means of measuring their effects to neighborhood objects

    Apr 22, 2012
• Prakash Kumar

  Why do gamma-ray sources exhibit greater red-shift?

  If red-shift is an indicator of distance and recession then at least some gamma-ray sources must exhibit lesser red-shift. If this is not so then we have to think over again.

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• Aleksandar-Saša Nedeljković

  Sun's radiation VS Galactic radiation intensity

  While reading an article about Voyagers entering "magnetic foam" part of Solar system, I've read that intensity of electrons in the foam increased 100 times in intensity (so far), as heliopause (orWhile reading an article about Voyagers entering "magnetic foam" part of Solar system, I've read that intensity of electrons in the foam increased 100 times in intensity (so far), as heliopause (or its foam part) acts as a shield against outer radiation. Now if hypothetically Sun heliosphere didn't exist, how intense would be that galactic radiation on Earth, as opposed to Sun's daily radiation at current distance from Earth?

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    Jürgen Kiener replied

    The galactic radiation of energetic electrons and ions outside the solar system's heliosphere is only partly known. What is relatively well known is the high-energy part above a few GeV, resp. GeVThe galactic radiation of energetic electrons and ions outside the solar system's heliosphere is only partly known. What is relatively well known is the high-energy part above a few GeV, resp. GeV per nucleon. These particles are only slightly affected by the solar system's magnetic field and are measured by instruments on satellites or balloons. Below these energies, I think that we have to wait that Voyager leaves the heliosphere and measures these particles (if it is still active then) to know exactly what their intensity is. There are indirect observations for electrons, the electromagnetic radiation they produce when interacting with the galactic magnetic field and interstellar gas and dust, that give an idea of their average intensity in the Galaxy (see e.g. Astrophysical Journal 739, 29). For ions, there are less indications (interesting is the H3+molecule in diffuse clouds, Astrophysical Journal 745, 91). Standard models for cosmic-ray propagation in our Galaxy predict at least a factor of four more low-energy protons (0.002 - 1 GeV) than high-energy protons (above 1 GeV), but there are indications that there may be many times more (reference above: ApJ 745, 91). The Sun can also create energetic electrons and ions, but only in bursts and a comparison is then difficult. The intensity of low-energy protons can, however, increase by more than a factor of thousand w.r.t. to quiet levels during those events (one recent event like that to see in the archive data of http://www.swpc.noaa.gov/today.html starting March 7, 2012).

    Apr 18, 2012
• Ronald Stewart

  Could this be an image of spherically shaped scarlet colored new minor planet in our solar system's asteroid belt ?

  As can be seen in the image-(image credit-(Ronald Stewart-(C) 2012) one side of this spherical-like shaped space anomaly has a similaritiy to it that one side -(like earth on the light and dark sidesAs can be seen in the image-(image credit-(Ronald Stewart-(C) 2012) one side of this spherical-like shaped space anomaly has a similaritiy to it that one side -(like earth on the light and dark sides of out planet) faces toward the sunlight. yet it also appears to have possible ice on the lighted side as well.