Astronomy and Cosmology

I'm currently reading a book by Jeremy Robinson of which the premise is that our solar system passes through some kind of massive interstellar cloud containing huge quantities of iron (in the form of snowflake-like flakes) that, to simplify a complicated story, hits the Earth and rains down like snow, becoming oxidized in the process, and ultimately removing all the oxygen in the lower atmosphere and wiping out millions of people by asphyxiation. I was just wondering whether this idea even comes close to approximating being possible, or if along with some of Robinson's other ideas is pure fiction? Can anyone tell me?

I am curious to know what the rate of time on Mars is with that of Earth time. So, for example, if the Curiosity rover were able to flash a strobe of light powerful enough for us on Earth to see it, and the rate of the strobe is 1000ms (according to Spacecraft Event Time...which in this case would be Mars Time), would that strobe of light appear faster or slower than 1000ms Earth time to an observer on Earth? I didn't quite know how to search for my question on Google, because the answers that I received were along the lines of offset time (if it is 1pm Eastern time on Earth, what time is it on Mars for the Curiosity rover). Also, is it possible to calculate thi…

If the entire universe really was smaller than a proton when it started expanding, and it has been expending at a finite rate. Even if explansion during inflation was a number of times faster than light speed, the expansion rate was a finite number. Then how can it reach an infinite size in a finite period of time? Therefore, it appear that the size of the universe is finite.

The curvature of universe is -ve or +ve How to determine it?

If we had a universe which was full of copies of our Local Group throughout the entire universe I would have thought that given the tremendous distances in the universe that eventually objects far away would be too small to resolve. So why do we still see objects like Quasars that are far more massive more brighter and more powerful than anything we have in our neighbourhood.

I'm uncertain of the definition of the universe but I would assume that it includes empty space as well as the celestial bodies that are in it. If one were to travel through space for an infinite amount of time would it be possible to come to the end of the Universe? If it were possible what would there be at the end? Nothing? Empty space? Is empty space not 'something'? How about a brick wall. What is on the other side of said wall? In my own personal opinion infinity is......... period. Space and therefore the universe must be infinite. If this thinking is flawed please explain. Thank you.

Our Sun's Oort Cloud seems to extend at least a light-year away from the Sun. QUESTION: Arguing from the Cosmological Principal ("what's here is there"), could other stars have colossal cometary "Oort Clouds" too ? If so, comets could, conceivably, populate an appreciable fraction of the inter-stellar space between stars -- the disk of the Milky Way Galaxy might be a "blizzard" of such icy bodies*. * The Outer Oort Cloud was once believed to boast about a Jupiter's mass worth of comets (~0.001 Msol). The Inner Oort Cloud is believed to boast "tens or hundreds of times as many cometary nuclei as the outer halo" (~0.1 Msol). Thus, there is an outside chan…

It is pretty clear that the universe is expanding because of the galaxies moving away from one another. But how does that work? I read that is what dark matter or dark energy does. I'm curious how dark energy could use gravity as a repulsive force, or is there another idea of how this might be happening?

I would immensely appreciate it if fellow colleauges can examine a decade or so of studies by R.M. Santilli (See his CV: http://www.world-lecture-series.org/santilli-cv) establishing that the redness of the sun at the horizon is due to an apparent new mechanism for direct sunlight losing energy to a cold medium (or gaining energy in the case of a hot medium.) I feel that Prof. Santilli is correct with his mechanisms and am looking for additional comments to point out any holes. More specifically, to my attentive understanding, part of sunlight is lost due to scattering resulting in the colors of Earth's atmosphere that are beautifully represented by Rayleigh scattering…

Since the Kepler Mission search for other earth-like planets is such an efficient method, why not send up more? Technology is always improving. Within a few more years a more powerful Kepler-style telescope can detect even smaller planets. "Kepler is a space observatory launched by NASA to discover Earth-like planets orbiting other stars. The spacecraft, named in honor of the 17th-century German astronomer Johannes Kepler, was launched on 7 March 2009, and has been active for 3 years, 9 months and 20 days as of December 27, 2012. "The Kepler mission is "specifically designed to survey a portion of our region of the Milky Way galaxy to discover dozens of Eart…

Be in permanent daytime and the other in permanent nightime. If you understand me? If it stopped spinning on its axis thing, would half of us always see the sun an the other half only see moon....

New here. A physics school teacher recommended this forum on Twitter. In the last century astronomers and cosmologists have put forward evidence that space itself is expanding -- not just that matter is moving away from other matter, but that the space itself in between is expanding. Questions: (1) If space itself is expanding, is that expansion homogenous with respect to all four dimensions, x, y, z and t? In other words, is that expansion uniform throughout the universe? What does observation and evidence suggest? (2) Is the expansion of space necessarily the same at all scales? Should the same effects of expansion observed on a grand cosmological scale also…

If stars attract everything,and that too with a very high gravitational force, objects like planets would've fallen into the star. But how did they start orbiting the stars?

When it comes to deep space travel, the problem of solar radiations arises, or more precisely how to shield the astronauts from it. I know that we are protected by the magnetic field of the Earth, but what's the main issue in using the same principles in space? Couldn't we generate a magnetic field around a spaceship? Would it be too heavy? Or would it need too much power? I'm sure the answer is pretty obvious to physicists because I never even heard of this possibility. Thanks in advance.

There is an observed relation, between the brightness & power of relativistic jets, common to Quasars & GRBs: http://phys.org/news/2012-12-common-physics-black-holes.html Could the following calculations help explain the same? [math]P = \frac{e^2}{6 \pi \epsilon_0 c} \left( \gamma^3 \dot{\beta} \right)^2[/math] [math] = \frac{d}{dt} \left( \gamma m_e c^2 \right) = m_e c^2 \left( \gamma^3 \beta \dot{\beta} \right) [/math] So: [math]\gamma^3 \dot{\beta} = \frac{3 c}{2} \frac{m_e c^2}{\left( \frac{e^2}{4 \pi \epsilon_0} \right) } = \frac{3 c}{2 r_e} \beta [/math] [math]\frac{\gamma^3}{\beta} d\beta = \frac{3 c}{2 r_e} dt[/ma…

I am writing a research review on dark matter and cosmology. I ran into a paper http://arxiv.org/abs/1104.0539 describing the problems faced by LCDM cosmology. One such problem related to the alignment of the low multipoles of the CMBR (as L. Perivolaropoulos puts it). The exact phrase used in the paper is I am comfortable with the idea of octopoles and quadrupoles as higher order terms of the same multipole expansion that gives the dipole fields, but I do not understand what is meant by the plane of the quadrupole and octopole. Can anybody help me to understand this? Thanks cohen990

The dark matter concept arose when astronomers measured rotation speed of the galaxies and they deduced that there must be more matter than we can see. And then appeared solution Dark matter. I'm curious how they can measure the rotation speed of the galaxies since in terms of a human lifetime its rotation is very slow. For example our solar system completes its orbit every 225 million years or so. Our rotation speed (220 km/s I don't know how acurate is this data) is fast but Galaxies is very large and I cannot figure out how can you detect its rotation through telescope since you cannot see moving stars unless very close ones to the centre.

I am fairly new to astronomy but very interested in learning all I can. Right now I'm on my own and teaching myself until I get to college. Does anyone have any references that can get me started in understanding. I have read a brief history of time and other simple books, but I know nothing about any of the math and I'm hoping to learn more in the topic of astronomy. Also I have been outside with a telescope looking around. I found some planets and major star constellations. But I'm curious in what else I can look for and maybe some books showing me what I'm even looking at. Greatly appreciated thank you!

For sake of simplicity, assume a flat cosmology. Then, from the Friedmann equations: [math]H^2 = \frac{8 \pi G \rho}{3}[/math] [math]\dot{\rho} = - 3 H \rho = - \sqrt{24 \pi G} \; \rho^{3/2}[/math] If, at one moment of time, two separate regions of the universe have slightly different densities; then they will have slightly different scale factors, and expansion rates, according to the above equations. Seemingly, the density difference would evolve as: [math]\frac{\partial}{\partial t} \left( \rho - \bar{\rho} \right) = - \sqrt{24 \pi G} \; \left( \rho^{3/2} - \bar{\rho}^{3/2}\right)[/math] [math]\approx - \sqrt{24 \pi G} \; \left( \ba…

According to the Saha equation, applied to a pure hydrogen gas: [math]n \frac{f^2}{1-f} = \mathcal{N}_0 \tau^{\frac{3}{2}} e^{-\frac{1}{\tau}} \equiv \mathcal{N}(\tau)[/math] where: [math]f \equiv \frac{n_e}{n}[/math] [math]\mathcal{N}_0 \equiv \frac{1}{ \lambda_C^3 } \left( \frac{ 2 \pi \chi }{ m_e c^2 } \right)^{\frac{3}{2}}[/math] [math]\tau \equiv \frac{k_B T}{\chi}[/math] [math]\chi \approx 14 eV[/math] and where i have attributed ions (protons) two degrees of freedom (g+ = 2), and neutrals (hydrogens = protons + electrons) four degrees of freedom (g0 = 4). Ancient Greek scholar Pythagoras gives the ionization fraction: [math]f =…

Many factors contribute to making current solar system. Is this one of the causes making small planet in the solar system?

What would happen, to the expansion of the universe, if Structure stopped stretching (as fast as the Voids)? Qualitatively, assuming a flat cosmology; and assuming that, in recent epochs (z<2) Structure has been expanding more slowly than Voids; so that by present epoch (z=0) Structure occupies only a quarter of the volume of space, whereas Voids occupy three quarters: [math]\rho = \frac{M_S + M_V}{V_S + V_V} \approx \frac{M_{tot}}{V_{tot} \left( \frac{1}{4} \alpha^2 + \frac{3}{4} \alpha^3 \right) } = \frac{\rho_0}{\frac{1}{4} \alpha^2 + \frac{3}{4} \alpha^3} [/math] where [math]\alpha \equiv a(t)/a_0[/math] is the normalized scale factor. So, from the first…

i have very little knowledge of these things so i wanted to ask the community a couple of questions that have been bothering me lately. first question. If there are billions upon billions of stars, why when i look up at the sky, I do not see a star exploding by the second or minute? Billions of stars would mean that thousands of stars are exploding per day every day right? Why do we never see this happening? Why in my 29 years of life, have we not had a star that has blown up remotely close to and just extinguish our lives? To me this would make sense given the fact there are countless stars. Given all the stars, there HAS to be a star close to us about …

If gravity is a force acting between anything that has mass, why does gravity from black holes pull in light (photons) which have no mass at all? And even if we consider light as a particle and not a wave, any particle with a finite mass needs infinite energy to accelerate to light speed. And one more thing. If gravity can pull in light, what happens to a beam of light coming towards a black hole? Would it accelerate due to gravity? And would light break its own top speed?

I was thinking about what the shape of the universe must be if it had a shape which it should be more or less a large ball shape that is ever expanding at the speed of light--if the Big Bang Theory were true. However, I thought maybe since our universe seems relativey young and the galaxies seem to have no set orbit around anything and no one can seem to answer what is really at the center of our universe maybe there is no center that exploded. Could it be a ball with a tunnel in the middle; overall a ridiculously large black hole in the center of our universe much larger than any galaxy. A black hole that spews the "ever expanding" universe out one side, the side the Mil…