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16h
comment Is their any clue where gravitons come from?
Note that there's no big problem in quantizing gravity at low energies--it's when it's used at high energies approaching the Planck scale that it starts being genuinely broken. This means that the notion of graviton is at least more than just an analogy with electromagnetism, as it can be sensible part of an effective field theory.
1d
comment what is gravitational force?
@TheVoid Of course it would (as strange as such taking such a shape or being able to hold it against its own gravity would be). But your question is such a bizarre non-sequitur that I suspect you're just trolling me, so I won't bother replying to you further.
1d
comment what is gravitational force?
@TheVoid What are you on about? Gravity has been described by a massless spin-2 field since 1915. I recommend you check e.g. Feynman's Lectures on Gravitation (initially done in 1962), which includes an argument that a massless spin-2 field implies the equivalence principle (the pillar of general relativity) for point particles or bulk unpolarized matter. This was shown more rigorously using quantum field theory by Weinberg in 1972. These things are well-known features of gravity.
1d
comment what is gravitational force?
Gravitational force is mediated by a massless spin-2 field that couples to energy, similarly to how electromagnetic force is mediated by a massless spin-1 field that couples to electric charge. That much has been understood for quite a long time now. Beyond that, I'm not sure what you're intending to ask.
2d
answered What is spacetime 'made' of?
2d
comment What is spacetime 'made' of?
This answer is rather misleading because it suggests that curving a coordinate system is what spacetime curvature means. That would be very wrong, e.g. taking curvilinear coordinate system in flat spacetime in some sense represents a nontrivial change in gravitational field (specifically, in the sense of changing the connection coefficients), but it definitely isn't physically significant, nor it does not introduce any curvature. Coordinates just aren't physically important; they're labels we give events.
2d
comment What is spacetime 'made' of?
@Dean whether mathematics is discovered or invented is a philosophical matter that's certainly questionable in either direction, but neither claim has any scientific content. Let's just say your position on that is far from universally shared.
Feb
1
comment are modern flat earthers still believe the earth is flat not round?
Sometimes it's quite difficult to differentiate between honest belief and instances of Poe's law. ... But unless you reword your question to be specifically about some astronomical claims they make rather whether they're sincere, this question might be better fit for skeptics.SE instead.
Jan
31
reviewed Close Time travel - how far can we go back
Jan
18
comment What is the Maximum Speed that can be acheived Because of Acceleration Due to Gravity?
@RobJeffries Wouldn't Gullstrand-Painleve chart suffice? At an instant of infallee time, spatial geometry is Euclidean, so there shouldn't be a mismatch between lengths of freefalling ideal physical rods and coordinate differences.
Jan
11
awarded  Nice Answer
Jan
7
comment When I read that a system is located x light years away, why is there no direction?
Since the phrasing of your question also suggests a certain misunderstanding, you might find these useful: What is in the center of the universe? and Do we know the exact spot where big bang took place?.
Jan
6
awarded  Nice Answer
Jan
1
answered Is the duration of a sidereal year stable?
Jan
1
comment Camera reaching the event horizon
@Ricky I'm not going to discuss the validity of evidence for the existence of black holes in these comments (it's irrelevant here), but I will note that your attitude is completely backwards. One must first understand at least the bare basics of how black holes would behave (and a question like this counts) in order to be in any position to even start evaluating evidence of their existence, regardless of whether one accepts the evidence or not.
Dec
31
revised Camera reaching the event horizon
mostly fixing typos
Dec
31
answered Camera reaching the event horizon
Dec
30
comment What is the gravitational force felt on Earth from the other planets in our solar system?
Well, one could use $GM/r^2$, where $GM$ is the standard gravitational parameter and $r$ is some typical distance. So the question is basically equivalent to asking for a typical distance between Earth and the body in question. For Earth-Sun or Earth-Moon, it's sensible to use the semi-major axis of the relevant orbit, but... how do you want to measure the rest? It's essentially easy to get a rough figure, but potentially hard if you want some spatial or temporal average, etc.
Dec
29
answered A camera and time dilation?
Dec
27
answered Are black holes expanding?