A defining feature of a black hole is that because of it's gravity nothing will escape it, not even light. This clearly doesn't hold for atoms. They can be bombarded by photons and electrons and split and fused.
> A defining feature of a black hole is that because of it's gravity nothing will escape it, not even light
One could say that not all events in space time are sufficiently curved to be that of a black hole; the curved space time representing a few atoms may not be as curved as the curved space time representing a black hole.
Wouldn't they if the existence of them is defined by the curvature of spacetime itself (if energy densities in various configurations is composed of spacetime that is curved to various degrees [maybe like how another commentator here, id call this "knottedness"], how the energy densities evolve in a given spacetime configuration is also curved?)?
That is an event as described when spacetime structure is defined as orientable, where as i'm trying to get at what would it be described as if spacetime was non-orientable, and it doesn't seem like its just "Never"[0]
I've seen something that seems similar like what some are talking about here described as[1]:
"If a spacetime is not time-orientable then a closed path exists round which the direction of time reverses. The simplest example of non-orientability is the Mobius strip. On the Mobius strip left-handed and right-handed cannot be consistently defined over the whole surface. A left-handed coordinate basis changes to a night- handed one when going round the circumference of the strip.
The Mobius band can also be thought of as a spacetime diagram for a circular space, S1, and a non-orientable time. The direction of time reverses on a path around the circumference S1 of the band. Note that our usual image of a Mobius strip is as a 2D surface embedded in 3D. However the embedding is not unique and the Mobius can be defined in a number of ways without resorting to any embedding at all.
More importantly, it has topological properties (The non orientability) that can be described independently of the embedding. Of particular interest is a model of a particle as an asymptotically flat spacetime manifold with a region of non trivial topology where time is not orientable."
But its hard for me to come up with a term that can encompass a particle and a black hole (i'm sure there has to be one out there), in different regions in an asymptotically flat spacetime manifold, but exist in the same non trivial topology where time is not orientable.
That means that cinquemb is using the wrong term for what s/he is trying to say. Once you stop thinking of the technical definition of "event", though, there may be the germ of a point there...
Gravity is a strange thing, because as far as I can intuit, it is not constant (even though classical Newtonian Mechanics tells us it is, and even has a constant for it, G) -- but as far as I can intuit, Gravity is relative to both scale and wavelength...
That is, it will bend different electromagnetic wavelengths differently, like a Prism...
To understand this, consider smaller attractive phenomena, for example, magnetism, and electrostatic attraction (you rub a balloon, it "sticks" to surfaces). Those are both attractive phenomena similar to Gravity, just at much smaller scales.
If you have a water wave pool, there are ways to get objects in the water to be attracted or repulsed, via different wave forms.
In fact, maybe this is the problem. We're calling Gravity "Gravity", rather than "attractive/acceleration force at large scale (which again is a law of the squares phenomena, that is, it drops off as the square of the distance, but the distances involved in gravity are very large, planetary sized (or larger) in effect).
So you're right -- it wouldn't hold for light, but perhaps there are smaller analogous, attractive phenomena, that it would hold up for.
And perhaps there are smaller in scale, yet analogous phenomena to light -- like sound or vibration.
See this is the problem in physics... we're calling PRINCIPLES (in this case, the attractive principle) by different names... Gravity, Magnetism, Electrostatic, Strong and Weak Nuclear Forces, etc.).
Every single thing, and every single principle in the Universe -- has analogues of it at different SCALES.
The knowledge of these principles (which can be deduced by simple observation "what is the unifying principle behind these phenomena?") should come before math equations, especially those with constants, BEFORE we make a serious inquiry into physics.
We should ask HOW something would be possible -- rather than trying to figure out WHY (based on current knowledge) it is (or seems) impossible... then we'll start making great strides in physics...
Gravity and electromagnetism are basically the same from a mathematical perspective if you’re just looking at the forces produced: they’re both inverse square, proportional to some intrinsic property of the objects involved. The main differences are the constant in front (gravity is kind of wimpy) and the fact that “electrical mass” can be negative and its force has a minus sign in front. The only reason you see gravity at large scales is that charges mostly cancel out at larger scales, while gravity cannot.
There is a difference though: a test-mass moving freely in a gravitational field does not experience that field (it feels the same as a test-mass in empty space). A test-charge moving freely in an electrical field however will experience an acceleration (it feels something is pulling on it).
I see where you’re coming from (with the naive formulation of the proportional charges/masses and inverse square law) but at relativistic and microscopic level they are very different (including, as another poster observed, the remarkable property that a test-mass accelerated by a gravitational field is unable to observe that field, which is a formulation of the famous Equivalence Principle).
