I've heard and read that our solar system lies near to the peripheral region of the Galaxy. Then accordingly we would have a greater probability of sustaining to eventual gulping down by the super-massive black hole. But how long ?
122988
I'm making several assumptions, not sure if any are correct:   there is a black hole at the center of a galaxy the black hole is eating the galaxy   Eventually the galaxy will be gone, right?  Has this been observed? Do we know what happens afterwards?  Posting here since astronomy got merged into physics
93613
Imagine, if you will, there exists somewhere out there a supermassive planet. For some reason, this planet is only a shell of its former existence and all that is left is a crust of substantial size to keep it from collapsing in on itself (let's imagine it is stable at 5000' thick). Now, this planet was HUGE! How large, you ask? Large enough that the remaining shell is still able to maintain a gravity well strong enough to keep you anchored to the surface.  Pretty neat, huh?  Well, since this is a sight to be seen by everyone, you stroll along and, not looking where you are going, you tumble into a chasm and straight down into a hole that permeates the thickness of the shell. As you are falling down and down and down, you think:  "At what point do I stop falling down and I start falling up? And would I be able to retain the velocity, since gravity is a conservative force, and fall back through another hole on the surface on the opposite side? Where would the center of gravity even exist? I mean, aaaaahhhhhhh!"  What say you, browsers and scientists? A stretch of the imagination, sure, but is it physically possible? Could there exists a configuration similar to this where gravity could be concentrated to a point but still allow free travel up to the focus?
11921
So I understand the concept of gravity, in that it's not actually a force, but more of a displacement in the spacetime grid. An object with a big enough mass will bend the spacetime, causing smaller objects to "attract" to it (not really, but good enough for what I am trying to figure out)   Ok so that makes sense, but what I am not understanding is, how come planets don't just get engulfed by the Sun? There must be something acting against the gravity for the planet to be a certain distance away from the sun. Am I not understanding this concept correctly?
53302
The observed paths and speeds of objects, part of some distant galaxy, do not match up with speed vs distance curves it seems - the observed speeds are not falling off in fact they're trending as increasing or constant with distance. Wikipedia explains the phenomenon far better -   Dark matter is one explanation but it isn't without it's faults and flaws, at times raising more questions than being helpful. Particularly when trying to answer what dark matter might be composed of, and that the theory needs fine-tuning for any such model to match observations; from a lay-person's POV the idea is nice but seems to involve some handwaving regarding fine-tuning or composition (specifically what the secondary effects might be, as they may differ between candidate compositions).  With that in mind it occurred to me that galaxies are very large, and rotating. I don't have a clear picture of scale in mind when it comes to this... However it does seem like one (or both) of these two effects may be contributing:   Ehrenfest Paradox - I'm not certain it is applicable, but it is remarkable that there are features in common between a galaxy and a relativistically-rotating disk, the latter being the subject of a paradox regarding geometry. Gravitational time dilation - because of the size and mass distribution of a galaxy, to an observer outside the galaxy, the center would gain time slower than the arms / edges; effectively the edges of a galaxy would appear to move faster than they should, when using inner orbital speeds (in a higher gravitational potential) as a reference.   To help understand why I suspect these effects, it is worth noting the sheer breadth of a galaxy, that it has to be measured in kpc (kiloparsecs)... It can take many 1000's of years for light from one side of a galaxy to reach the other (enough time for cumulative time dilation to become a noteworthy factor I would think), suggesting that a galaxy's internal dynamics may be taken for granted in explaining the observed orbital speeds.  In other words it may be the case that locally (in the remote galaxy), these excessive orbital speeds may not be excessive after all.  Which, if any of these effects, are or could be contributing to the discrepancy in expected orbital speeds of objects in a remote galaxy as observed here?
26506
Some (generous) assumptions:   We have a spaceship that can reach a reasonable fraction of light speed. The ship is able to withstand the high energies of matter impacting at that speed.   Given the amount of matter in inter-stellar space, at high speed, would it encounter enough of it and frequently enough that an aerodynamic shape would significantly reduce its drag (and thus save fuel)?
1453
How much extra distance would I have to travel through space to get from Earth to a stellar mass event horizon? (compared to the same point in space without a black hole)
72173
Some say we live in the golden age of the universe because there exits countless number of stars that shines in the dark universe. As the supply of gas for star formation is steadily being exhausted, it is estimated that star formation will cease in 100 trillion years.  Question: Will there be a day that the universe becomes completly dark when all the stars burn out? Does all the cooled bodies eventually collide due to gravitational forces? Will black holes eventually dominate the universe?
77494
Have any references ever been made to the existence of Earth, our solar system, or the Milky Way anywhere in Star Wars Legends?  EDIT:  Following @Trader's answer, I wanted to point out that "A long time ago in a galaxy far, far away...." in the starting scroll is a very obvious answer, but not the one I'm looking for.
106642
I have seen many articles that talk about a star's "habitable zone" as the ring around it which is just the right temperature for planets to have liquid water, which is necessary for life. My question is, why does a planet need to have liquid water in order to sustain life? Who says that extraterrestrial life can't live off of some other kind of sustenance?
11509
As the galaxy is moving and the solar system orbiting the galaxy and the Earth orbiting the sun. So how fast is each object moving and what is the fastest we move at?  Do we even know how fast the galaxy is moving that is not relative to another galaxy (although I guess velocity has to be measured relative to something).
95890
I've got a basic understanding of these facts:   The Universe is a little over 13 billion years old.  Our galaxy is almost that old. Our solar system is roughly 4.6 billion years old. The heavier elements (Carbon, oxygen, etc...) are only produced by stars.   When our solar system coalesced, the matter that makes up the planets came from a previous generation of stars.  (Meanwhile our Sun is busy making its own slightly-heavier elements, but those aren't ours.  Those belong to the next "generation" after our star dies.)  So we're all sitting on a rock whose matter was spewed out of a star (or stars) that preceded this solar system. But what I want to know is:  How many cycles of coalescing, fusing, nucleosynthesis, exploding -- and then repeating the cycle -- have this atoms in this ball of rock I'm standing on been through?    How do you know this?  Can you tell by the make-up of the matter in the solar system?  Looking around the Orion arm to see remnants of our former home?
36980
I have an intuitive scenario. Consider we have a spaceship just below the event horizon of a BH, which is merging with another black hole.  Finally, the singularities merge and we have a single black hole again.  But, in the transient stage, it is unclear to me if a timelike world-line would exist to leave the system.  I suspect, the metric is probably far too complex for an analytical solution, but in the worst case, it could be maybe solved numerically.  As far I know, black hole merges are examined mainly in an inspiral scenario. I suspect, maybe the escape is possible only if they have a hyperbolic-like orbit (i.e. there is no inspiral, but they simply collide).  Is it possible?
82528
The classical explanation of a black hole says that if you get to close, you reach a point - the event horizon radius - from which you cannot escape even travelling at the speed of light. Then they normally talk about spaghetti.  But here's a thought experiment. What if I have a BH with event horizon radius R such that the gravitational gradient at the event horizon is far too weak for creating pasta. I build a Ring with radius R+x around the BH. Then I lower a pole of length x+d from my ring towards the BH, so that the tip passes beyond the event horizon.  Now what happens when I try to pull the pole back?
48971
Does the Schwarzschild radius exist at the exact tipping point where neutron degeneracy pressure fails?  For example, consider a hypothetical neutron star that is being held up just below the limit of neutron degeneracy pressure. If the neutron star gains enough mass (assume a constant radius), it will collapse into a black hole. Does neutron degeneracy pressure fail at the exact point where the neutron star gains enough mass appropriate for the resultant black hole's Schwarzschild radius (where the escape velocity = c)? If so, why do these seemingly unrelated limits match?  Or... does the existing neutron star's radius exceed the resultant black hole's radius? In other words, does neutron degeneracy pressure fail, and as the the neutron star's radius decreases when collapsing, does it eventually reach a smaller (than in the previous scenario) Schwarzschild radius? If this is the case, what is the "in-between" state of matter as the neutron star collapses into a black hole?  Thank you!
2687
I was surprised to only recently notice that      An object of any density can be large enough to fall within its own   Schwarzschild radius.   Of course! It turns out that supermassive black holes at galactic centers can have an average density of less than water's.  Somehow I always operated under the assumption that black holes of any size had to be superdense objects by everyday standards.  Compare the Earth to collapsing into a mere 9mm marble retaining the same mass, in order for the escape velocity at the surface to finally reach that of light.  Or Mt. Everest packed into one nanometer.  Reading on about this , it increases proportionally with total mass.  Assuming matter is accumulated at a steady density into a spherical volume, the volume's radius will only "grow" at a cube root of the total volume and be quickly outpaced by its own gravitational radius.  Question: For an object the , what would have to be its diameter for it to qualify as a black hole (from an external point of view)?  Would this not imply by definition that:   The Earth, Solar system and Milky Way are conceivably inside this black hole? Black holes can be nested/be contained within larger ones? Whether something is a black hole or not is actually a matter of perspective/where the observer is, inside or outside?
30190
I am only an interested layman in cosmology and GR. In recent years, we have learned that black holes indeed exist in the universe and that almost all galaxies contain massive black holes in their centers. Black holes, in essence only devour other (stellar) matter and they also swallow each other as has been demonstrated by the gravitational wave discoveries. Is it possible that black holes eventually will "eat" most or even all normal and dark matter of the universe? And could this, and a merging of black holes, lead to a situation where all the universe ends up being a few or even only one black hole?
75856
As XKCD recently educated some of us in a "What If" blog post, playing (near) light-speed baseball on a planet with an atmosphere .  The TL;DR version translates to:  A baseball moving at 0.9c is traveling too fast for particles in the atmosphere to get out of the way.  The resulting atomic collisions set off a chain reaction that feeds off of the rest of the surrounding atmosphere, turning into a massive nuclear explosion.  This does not bode well for the batter, the pitcher, the catcher, or anyone else within a few miles of the reaction's epicenter.  Bringing this issue into context with the Star Trek universe, there was a point in the 2009 movie where the Enterprise came out of warp amidst the clouds of Saturn's sixth moon, Titan.  Presumably, this means that the Enterprise at some point was traveling through Titan's atmosphere near or above the speed of light.  Is there some principle of warp drive technology that allows the Enterprise to avoid the fate of the baseball in this situation, or should that interaction have actually destroyed (at least) a good part of the Enterprise and Titan?