Astronomy and Cosmology

I'm not sure if this is the correct forum to ask this question, given that it's more concerned with science fiction than science fact. Still, it does bring into play Newton's field equations. So here goes: assuming a spaceship or probe of some kind is travelling between (say) the Earth and the Moon and it happens to have a suitably advanced propulsion system that enables it to maintain a continual thrust throughout the voyage; this being so, would the craft make its mid-voyage 'turnover' at the halfway point between the Earth and Moon? Or would it be more advantageous to perform this manoeuvre at the gravitational 'null point' between these two bodies - that is to say, wh…

Tonight Horizon Program about the current visit of Comet ISON going around the Sun in the next few days/weeks Link to Horizon Program Now available for viewing Late Nov 2013 to Dec 2013 http://www.bbc.co.uk/iplayer/episode/b03k3881/Horizon_20132014_Comet_of_the_Century_A_Horizon_Special/ Mike Set off from the Ort Cloud .... some Four and a half billion years ago ... just coming by now 4.5 billion years later.Everybody should be able to see it in the northern hemisphere........ look east South East just above horizon DECEMBER 1st 2013, just below the Moon and Mercury. Thats this weekend ... rising by 10 degrees a day... I am over there view…

http://jersey.uoregon.edu/elements/Elements.html I recently stumbled upon this link while looking for a good tool to use to help identify elements by spectra, but I noticed some things I didn't quite understand. Why is it that Thorium and Uranium have such a wide ranged emission spectrum while plutonium has a much smaller one. I read that the more electrons and higher shell configurations give more possibilities to emit light, especially if the electrons are in higher shells. Could somebody clarify?

Is there a way we can estimate light (lux) levels in broad daylight on Titan? eg would it be like a cloudy day here on Earth, dusk or no more light than with a full moon? Would the clouds be thin enough for an astronaut to see Saturn? Do the clouds ever part to give a clear sky? I've heard the sky would be orange with green methane rain. Would it always be foggy or could we see long distances? I'm an art student and I want to do a landscape painting of the surface of Titan cheerz Gian x

I understand from Wikipedia that the apparent magnitude of the Sun, as viewed from Earth orbit, is about -24.74. This being so, and allowing for the well-known fact that one would risk permanent eye damage by staring up at the Sun for any length of time (other than during sunrise and sunset), would it be possible to safely gaze at a point source of light if it were shining at a magnitude of -17? I gather this magnitude is around a hundred times brighter than that of the Full Moon, but still extremely dim by Solar standards. Nevertheless, as anyone who has had a 40 lux LED dynamo lamp directed straight into one's eyes (my lamp and my eyes, as it happens) they will know jus…

So, based on the motion of stars in galaxies and galaxy cluster motion etc., there is roughly 5 times more "dark matter" than ordinary matter in the universe. No one knows what this dark matter is. But, presumedly, it is in our solar system. So how does it affect the orbits of our planets around the Sun and moons around the planets, not to mention comets etc. ? How is it that we can explain these orbits and motions to such great accuracy using general relativity and only the masses of the Sun, planets, moons, etc? These do not include the effects of dark matter. If there is 5 times as much dark matter as the ordinary matter which makes up our stellar objects, why does…

Space has no time. only the physical objects within the space seem to age. space does not age, it just changes. It has always been there, and always will be. Thats the thing humans will never be able to comprehend, there is no creator, because you cant create something that has no beginning or end, just like it has no boundaries, it will be endless.

how do cosmic rays interact with the earths magnetosphere? Are they deviated from their incident path?

Hi there, I really hope someone can help me with my stupid but urgent problem of understanding something crucial about the Friedman equations. So; one of them looks like this (forget about the constants; it is about the principles): change of the scale factor with time - density - cosmol. constant = -k (curvature term) Then this is sometimes rewritten in terms of densities, which gives: change of the scale factor with time - (density of matter + vacuum energy density) = -k (curvature term) Now; here is what I do not get. Generally the density of the vacuum (or equivalently the cosmol. constant) are treated just like the density of matter; so the…

why is it that planets and other heavenly bodies only follow the elliptical path. (eccentricity < 1)? And not circular? As a planet like earth would extend its gravitational field equally in all directions and produce a circular "ripple" in space-time? A circle when stretched, so as to change its eccentricity produces an ellipse. Does that tell us something about the space-time matrix? Please elicit your opinions. Thanks in advance.

Just like we have a two satellite system (eg. Mars has two satellites Deimos and Phobos), is it possible to have a 2 comet system around the Sun? i.e 2 comets sharing the same orbit in anti-phase. What are the odds of this happening?

There are several theories of gravity. What theories of gravity you know?

With respect to quasars - do they define the limits of the universe that we know? are they made up of dark matter? in an accelerating universe do they approach the speed of iight and acquire the status of supermassiv e black holes? Please shed some light on this issue. thanks in advance.

Quasars are said to define the limits of the observable Universe. Such an aggregation of mass (quasars are super-massive black holes) at the periphery of the observable Universe may curve space time back upon itself and actually define not only the limits of the observable Universe but of the Universe itself. How far is this true? Please elicit your opinion. Thanks in advance.

I have some rather uneducated simple questions about comets. First - are all comets made of the same things, and if not what are the possible compositions? Second - are the nuclei of all comets made of the same thing, and if not what are the possible compositions? Third - what thing (other than direct impacts) can affect the orbit or path of a comet? Fourth - do comets have a magnetic component? Fifth - in regard to rotation, why do some comets spin asymmetrically while others spin symmetrically. What would cause the difference? Would it be the composition or shape nuclei of the comet or something else? Sixth - what if any effect would a comet have…

Does the idea of a "big bang" make any sense? I don't know. Haw can this alleged start of time occur when there wasn't any time before time in which it would start? Is there like fifth dimensional hypertime or something?

Time is defined in dimensional analysis as L0M0T1. Time is measured in seconds and smaller and higher magnitudes. However as we all know time is not absolute. It merely exists in relation to a frame of reference. Also it "moves" along its axis as an object is translated through space. We then say that time has elapsed. How then is time a scalar? It behaves like a vector and as we all know is irreversible. Why then do we not interpret time as a vector in classical physics in the light of this knowledge? Also if time were absolute and scalar throughout the universe then the twins paradox would have been impossible. Different rates of motion elap…

I have a big confussion about this hypothesis some time I think thak we should make some amendments in this hypothesis....

For example,a black hqle compresses the stars,gas,atoms of its gravity begins to rotate them with a huge hole speed.Black hole behaves as an accelerator in the interactions and the multiple collisions of particles and the particles are generated from the vacuum.Thus, the massive body of the vacuum pulls all the particles,reculting in curved space-time is reduced, reduced, sinse space-time itself and is composed of these particles in the form of wave-particle duality.Curves,shrinking space-time is converted into the energy of gravitational waves propagating around the black hole.One can cite the comparison our Sun has been losing mass, which due to thermonuclear reactions …

I am having trouble understanding why, according to the Big Bang Theory, density at the point of singularity is infinite. Here is my train of thought. Volume at point of singularity = 0 Density = Mass / Volume Density at point of singularity = Mass / 0 Density is undefined. I don't understand why density is infinite at the point of singularity if the simple calculation above yields an answer that is undefined. Are my calculations incorrect?

I want to know if the universe had a beginning or it always existed without a beginning? if the universe had a beginning then the question is what was the cause of that beginning? Was it the "BIG BANG" that caused the beginning of the universe? We all know according to the big bang theory, in the beginning all the matter and energy was compressed to an area of zero volume and infinite density. Cosmologists call that state SINGULARITY. Now the explosion of that singularity is not a big deal for me, what troubles me is that where from that singularity come from? where from all those matter and energy that was stored as a singularity come from? did the singularity pop out …

Is there any physically hypothetical way that a massive object like the sun or a planet be moved out of its normal environments trajectory.

why there is more matter than matter why there cant be a universe with more antimatte than matter

With the discovery of the Higgs boson scientists have found the particle responsible for defining mass. The movement of this particle through the primordial soup aggregated mass unto itself and the product was a curved space time that we now experience. But was there a flat space time in existence prior to this explosion of gravitational potential energy? Or was there nothing at all? Please elicit your viewpoint.

Our solar system consists of one star and 8 planets (primarily) in equilibrium. Is there an upper limit to the number of planets and planetoids that can be sustained by a star like our Sun? For example if our solar system had say 15 planets of different masses could that have also constituted a stable configuration? Can all such configurations be practically conjectured? (Are there equations to define these relations?)