Astronomy and Cosmology

At first I thought it was fake but then I went to the Nasa site and saw this animation of the Moon passing in front of the Earth. http://www.nasa.gov/feature/goddard/from-a-million-miles-away-nasa-camera-shows-moon-crossing-face-of-earth And then i thought, if the satellite is always facing the daylight on Earth, it means the sun is behind. And if the sun is behind, doesn't that mean that this is actually a solar eclipse going on?

If the expansion of the universe is uniform throughout and is less than c, how is it that beyond the Hubble Limit (HL) a photon will never reach the observer? I can understand, at great distances, that it gives a certain measured or apparent expansion rate that may exceed c, causing a photon to redshift, but locally, around the photon, the expansion rate still matches, objectively, the expansion rate at the locality of the observer. As it stands atm, in my current - wrong, no doubt - understanding, it seems that, beyond the HL, the expansion actually increases incrementally faster than c locally, resulting in the photon never reaching the observer i.e. it doesn’t just se…

I came upon this statement about gravity lensing the other day. It reads: "The ratio of a planet's radius squared to its mass lets us calculate the distance a spacecraft must reach to take advantage of gravity lensing." It's the first part of this statement that I can't understand - "The ratio of a planet's radius" especially. While I know the meaning of each individual word, I simply cannot string them together in any meaningful sense. Neither can Google apparently. Any suggestions?

Hello, it's my first post here I wanna discuss an idea that has come to my mind, when I was thinking about how an advanced civilization (> type 2 in Kardashev scale), could develop. So if an civilization, wants to win competition in advancement of technology with other civilizations, then one way would be to use time dilation effect for advantage. There are at least 2-3 ways to use this effect. Method 1 - use time dilation to make your civilization time run faster, compared to other civilizations, to increase speed of advancement in technology compared to other civilizations. There are few ways to make time run faster (if I'm not wrong). First would be to slow down…

Gravity is the attraction of two masses as discovered by Newton and we know that the “rate” of gravity is inversely proportional to the square of the distance of the two masses, however this does not include any third party masses eg atmosphere, other things of large mass. So surely when measuring gravity at a fairly accurate rate not using the universal gravitation constant, we would never be able to accurately replicate a reading of g. This would be due to the interference of other sizeable enough planets causing some mass of the measured object to be “attracted” to their gravitational field. This alongside of the constant flux of the composition of the atmosphere,…

Space is a form of matter viz-a-viz the final structure (it includes time after all time is but just a flux of perception perceived by matters as it moves and changes the course of it's physical state one after the next second).

Now I suppose this is totally speculative but I was wondering what you guys all thought could be beyond space and time. It is very difficult for us to imagine what no space and time would be like but I know you are all kind of geniuses so I thought you would probably have some great ideas that may even have evidence

Hello all, I am hoping that you may be able to save my skin. I have tried to find the information out myself as a layman in this, but the only resources I can find are terribly basic or beyond my understanding. Basically, I am writing a piece of fiction and I have a background environment within which I need certain things to occur, but they must be as plausible as possible. In order for me to accomplish this I need to know a couple of things… which is where you come in! The environment: a) A star roughly 1 solar mass has entered into its Red Giant phase and has expanded enough to make a particular planet (not earth, but roughly the sam…

Imagine we look in one direction and see a galaxy 10 billion years away. Then we look in the opposite direction and see a different galaxy 10 billion years away It appears like they are 20 billion light years apart and we are directly inbetween these two galaxies from 10 billion years ago and the CMB looks like a big sphere of 27BLY diameter where we are at the center. I understand this must be an illusion of spacetime. As a child I used to think it was because spacetime must be curved like a sphere and we were looking around all sides of the sphere to the other side. This was back when closed space was defined a cyclicle universe and not a sphere. But since scien…

I have seen a couple of references on EM forces creating galactic structure such as spiral arms and perhaps even intergalactic structure such as galactic filaments. https://public.nrao.edu/news/pressreleases/galaxy-magnetic-field Or in the documentary: "The Universe Forces of Mass Construction" But, it seems to me that a structure such as a spiral arm should explain the velocities. Imagine EM forces tying the SMBH to stars in a spiral arms, and every star in each arm connected in a lattice work of EM forces creating a semi-rigid spiral arm structure. Then you would expect the same kind of swept back arm that we see. Then the structure, in turn would create a…

http://www.jpl.nasa.gov/news/news.php?release=2016-154 http://edition.cnn.com/2016/06/16/us/nasa-asteroid-circles-earth/ 50 years ago gives 1966 so it could be another Saturn V S-IVB third stage like J002E3 from Apollo 12? It would be easy to test. https://en.wikipedia.org/wiki/J002E3 Maybe the modified stage 3 of AS-203, launched on July 5, 1966 wasn't inadvertently destroyed along with stage 2 after all. The modified stage 3 used would have to be very close to the weight of a normal stage 3 for the results to be useful. https://en.wikipedia.org/wiki/AS-203 It could also be the third stage from Apollo 8, 9, 10 or 11 which are all recorded to have reached…

What if time is but the heart of the universe, and matter, the body? It's beats and rhythms keeping perfect time. It's limbs and sensing parts being subordinate, though more completely apparent, more accessible. More apparently useful. What if that brief window of time we view the clouds swiftly passing by the vivid moon, pretending its swift motion, really portend the hidden frame of the universe? What if the universe is but a moment in time?

Having stumbled upon Wikipedia's article about the Darian Calender intended for use on Mars, I'm interested to know how this calendar corresponds with our own one here on Earth. More precisely, if the first day of the Martian year begins on Sol 1 in the month of Sagittarius (warning: this itself is very much a stab in the dark) does this coincide, temporally speaking, with our first day of the new year - due allowances made for the smallish, if variable time-lag existing between Earth and Mars? Or am I barking up the wrong planet? Many thanks https://en.wikipedia.org/wiki/Darian_calendar

Hello, I have not been around SFN for quite some time. I was focusing on my studies and also flying to different orbits using Orbiter Space Flight Simulator. Nice to see all of you again. Here I would like to start a new thread for those who use Orbiter and love to share their beautiful screenshots. I will start first. Here are 2 (beautiful, or maybe opposite; beauty is in the eye of the beholder) screenshots captured using Orbiter. The first is ThaiCom 8 launched to elliptical transfer orbit after SECO of Falcon 9. The second is GAIA of ESA in Largrange Point 2 or L2 after launched from Kourou Spaceport aboard a Soyuz rocket. The black …

Mainly trying to show the other superclusters increasingly separating from our own(blue line) and each other. Time is from the center outwards. Space is along any radius circle with the same center as the black circle. Got it looking like I had hoped. The Arcs are the main concern. Want to make them as accurate as possible. If there is a general formula anyone can provide that would be appreciated. Pleas note that this is just a picture and should not be taken too seriously or used for intercluster travel.

In 1700, French mathematician (Laplace) came out the theory that if there was attractive to the body field that was strong enough, the light and somehow he can not escape from this field and as a result will seem dark. This theory has been no proof until he came Albert Einstein’s theory of general relativity in 1915. Physicists began to study in detail and equivalents, which began in support of Laplace theory. According to the general theory of relativity, the gravitational curvature of space where the light straight walks. Which means that the light is affected and deflects under the influence of gravity. The black hole it space arched to the extent that it absorb…

Is the current/popular beliefs wrong that 1- the universe is expanding and expanding at an ever increasing rate, 2- dark energy or dark matter must exist to explain expansion? Einstein's equations/theory and subsequent based beliefs explained the universe as stable; Hubble's redshift caused a (expansion) constant be inserted, and again a later/recent 'redshift' required another change to an ever increasing constant be included in the equation...in effect proving both the stable and increasing assumptions/beliefs wrong already. Could the ever increasing constant be wrong also? And if they are all wrong, what is the…

I haven't put much thought into this question (and don't have much evidence for it, if any at all), so please poke holes in it, it's fun to see what you think . I've been thinking recently that our universe is a 4D object/shape. Whenever in my physics class, or on the internet, someone asks why everywhere is the centre of expansion for the universe, the analogy I hear a lot is that of a balloon inflating (I'm not going to explain it, so feel free to watch this video https://youtu.be/i1UC6HpxY28?t=57). Basically could our universe be the same concept as the balloon inflating; a 4D object expanding and our 3D world is on the surface. I think this would…

I can't remember what it was, but supposedly proponents of Dark Matter were challenged to predict the accuracy of Dark Matter theory by predicting where satellite galaxies around the Milky Way would be in 5 years. Their opponents were a group of scientists who claimed that dark matter didn't exist but only that the gravitational constant varied with distance. Despite all the hype of dark matter, the gravitational constant group came out ahead with amazing accuracy while the dark matter group was very far off. First question is: does anyone know the name of this experiment? Second question is: I don't have a particular preference for dark matter theory, but var…

We all know what would be the effect if we block emission of infrared radiation from earth. Actually we call this global warming . But let imagine a hypothetical situation that because of some strange reason someday someone decide to build a shield and wrap up entire earth in some more distant orbit even than that of the moon. The cage around the earth would be from some exotic material allowing the passage of all other electromagnetic spectrum except for microwave region. So in this scenario what would be the consequence for our planet and life eventually ?

Hello, would it be possible/reasonable for a planet to have a core made of Cobalt? Sorry if this is in the wrong area, I'm new here.

why does the daylight Moon appear to have a 'horizonal' shadow? I know it's know exactly horizonal but certainly it isn't vertical. It does not appear to have phases such as new moon, waxing crescent, first quarter, waxing gibbous, full moon, waning gibbous, third quarter or waning crescent. But it does appear that the daylight moon's lower quarter or lower third is shadowed by the Earth. What is the spatial orientation of the Earth, Moon and Sun to create this effect?

One cannot speak about the trajectory of a cannonball until it flew along this trajectory. One can speak about a calculated trajectory of the cannonball once a cannon is pointed at the target. However a real cannonball can leave this calculated trajectory. For example if it meets another cannonball. Now let's proceed from a cannonball to the universe. Cosmological theories present it as a four-dimensional continuum. It encloses in itself our past, our present and our future. But the future has not yet come. Therefore the four-dimensional continuum of the universe is similar to the calculated trajectory of a cannonball at those parts that correspond to the future. Only th…

So Planet X is real apparently. Or at least in the same sense as the finding of the chupacabra. Why are we so bad at locating this thing? Why is this happening now instead of a hundred years ago when the math was still there? And will we ever hear the end of it from conspiracy theorists?

Simple question: In our Local Group there are three main spiral galaxies: Milky Way, Andromeda Galaxy and Triangulum Galaxy. Andromeda is quite close to Triangulum Galaxy, while our distance to Andromeda is significantly longer (2.54 Mly). Therefore, it is quite clear that the gravity force between Andromeda and Triangulum should be much stronger than the gravity force between Andromeda and Milky way - due to the distance. Somehow, it seems that Adromeda is moving away from Triangulum while both of them are moving in the direction of the Milky way. So, if those two galaxies are so close together, why they are not moving closer to each other? Why do they prefer t…