Questions about relativistic theory of gravity. General relativity describes gravity as a geometrical property of space and time.

learn more… | top users | synonyms

2
votes
1answer
116 views

Has the velocity of photons coming from black holes already been measured?

Has the velocity of photons, which are coming from black holes, already been measured? I am not aware of such measurements. The reason for the question is the following: If space-time near black ...
0
votes
1answer
54 views

Why is the CMB not simply travelling parallel to us? [closed]

When we look to the distant farthest reaches of the universe we see light that was emitted at the big bang 14 billion years ago. But the universe was tiny back then so that light, which is only ...
4
votes
4answers
621 views

How could a neutron star collapse into a black hole?

White dwarfs usually do not collapse, as they have electron degeneracy pressure due to the Pauli exclusion principle. However, if one accretes mass beyond the Chandrasekhar limit, it is energetically ...
0
votes
1answer
23 views

Can we measure/detect GR light bending during solar eclipse using ordinary equipment?

Suppose an amateur astronomer finds himself watching Solar Eclipse. He can see the stars around totality. Is Sun's GR effect strong enough for the amateur astronomer to be able to tell that a ...
2
votes
3answers
234 views

Does mass create space?

Imagine two cubes each with the side 1 light year. One of the cubes is empty of any matter. The other cube contains a massive star. Does the cube which contains the massive star have a larger volume ...
5
votes
1answer
85 views

What are the biggest problems about the numerical, finite-element GR models?

As I know, for example the modelling of the collapse of a neutron star (to a black hole) wasn't done correctly until now. Why? Yes, I know, the Einstein Field Equations aren't really easy to solve. ...
0
votes
2answers
202 views

How far into the future can we go by traveling close to a black hole?

If we sent someone on a path that passed as near as possible to a black hole without getting pulled in, how far into the future would they go due to time dilation? Let's assume the black hole is 5 ...
1
vote
1answer
67 views

Is it ever possible that the graviation from the mass of kinetic rotational energy will overcome centrifugal force?

This is, I think, somewhat intuitively obvious, but this comment got me thinking about this: what is gravitational force? "Rotation speed can create centrifugal force opposing gravity and making ...
0
votes
1answer
34 views

Would a Einstein–Rosen bridge change size and/or position in an expanding Universe?

I appreciate that a Einstein–Rosen bridge has never been observed but since there are some valid theories in General Relativity I thought I'd ask this. Would the start and end point of a Einstein–...
6
votes
2answers
419 views

What can we expect from the first accurate image of a black hole?

From recent news from the Max Planck Institute for Radio Astronomy: The European Research Council (ERC) has awarded 14 Million Euros to a team of European astrophysicists to construct the first ...
3
votes
1answer
73 views

How does an absolute horizon form before the apparent horizon?

If I understand it correctly, the apparent horizon is the boundary between where light directed outwards will move outwards, and light directed outwards will move inwards. Even if light is moving away ...
2
votes
2answers
66 views

Gravitational field released during supernovae

During the collapse of a star at the commencement of supernovae, the intense pressures force fusion and fission to create the heavier elements and release vast amounts of energy. As this energy/mass ...
1
vote
1answer
33 views

Could the Sun's bending of light be measured on photographic plates before Einstein's prediction?

It was predicted from Newtonian physics already in the 18th century that gravity should bend light, but not by as much as general relativity predicts. This was first confirmed during a solar eclipse ...
1
vote
1answer
49 views

Light that travels eternally because of inflation?

What happens with electromagentic waves that are emitted into intergalactic space, but reach not any object because of inflation? Lets assume that photon A and photon B are emitted. Photon B hits ...
3
votes
1answer
51 views

Gravitational Waves and the Big bang

The Ligo website says "Detecting the relic gravitational waves from the Big Bang will allow us to see farther back into the history of the Universe than ever before." I find this puzzling. How can a ...
0
votes
3answers
68 views

How can we tell that the sun is moving with theories such as the theory of relativity?

In a nutshell, the theory of relativity says that we cannot know that the ether is moving because if we were on the sun, the earth would seem to be moving and visa-versa. Apparently, we can't find <...
28
votes
5answers
4k views

Quantum Mechanics after the detection of Gravitational Waves

Of course everyone knows by now of the detection of Gravitational waves But, since General Relativity and Quantum Mechanics don't get along, can we say now that this detection proves that Quantum ...
3
votes
2answers
100 views

Why does mass naturally move closer toward's the center of other masses?

If general relativity is understood to mean that mass curves space such that objects are still traveling in a straight line, why does mass naturally move closer toward's the center of other masses?
0
votes
3answers
177 views

View from inside the black hole

If an observer is falling toward a black hole with its face away from singularity then what will he observe after crossing the event horizon? The reason that why I am asking this question because as ...
2
votes
1answer
69 views

How far should the source be, for the gravitation waves to be visible on Earth?

If I understand it well enough, gravitational waves cause ripples in the space-time fabric. To our eyes, that would look like those rippling-effects on amateur videos. Where does a source have to be,...
1
vote
0answers
85 views

are modern flat earthers still believe the earth is flat not round? [closed]

I saw a video in youtube and read few articles about how flat earthers believed that earth is actually flat but not round. They even presented facts about how everything which is true right now is ...
0
votes
1answer
66 views

Gravity assist: why is the velocity doubled? [closed]

The Wikipedia article has this terrestrial analogy: Imagine standing on a train platform, and throwing a [tennis] ball at 30 km/h toward a train approaching at 50 km/h. The driver of the train sees ...
0
votes
1answer
56 views

Black holes and time relation

Why Is it said that if someone is being sucked inside a black hole then he/she may see that time is running slowly?
1
vote
2answers
150 views

A camera and time dilation?

If I travelled near a black hole, my time would progress slower relative to someone on Earth. This is clear enough. However, what if we sent a probe with a camera to a black hole? When we watch the ...
3
votes
3answers
222 views

Why can't gravity repel things?

Gravity is the result of the curvature of space, so could the curvature actually send objects away from the source?
1
vote
1answer
91 views

What's the relation between Einstein's Gravitational Theory and Dark Matter?

I was reading an elementary book on dark matter (in fact, a historical perspective) and there were mentioned how the scientific community react to the idea of dark matter proposed as a solution to ...
1
vote
1answer
99 views

Understanding gravity

Forgive me if my question has an obvious answer, but I need to know the answer. I always thought that more massive/energetic objects had a stronger force of gravity than less massive ones; that is, ...
1
vote
1answer
94 views

What's the difference between the apparent horizon and event horizon of a black hole?

The Wikipedia page for apparent horizon is pretty sketchy and requires some GR knowledge. Is there any simple definition?
3
votes
1answer
138 views

What you would see in a wormhole?

Science fiction seems to depict the experience of traveling through wormholes (if possible of course) as seeing psychedelic colors or lines of light where stars once were (ie. 2001 or Contact). I ...
1
vote
0answers
36 views

Extra dimensions [closed]

String theory, Kaluza Klein theory etc. need extra-dimensions. For string theory these are compactified. My feeling is that these extra dimensions are not of our 4-D space, but are only of the space ...
1
vote
1answer
291 views

Why does Earth have more gravitational force than the Moon if I stand on it?

Perhaps this is a silly question but I am trying to understand Einstein's general theory of relativity. I would like to explain my question in more detail. The greater the mass of an object, the ...
0
votes
0answers
28 views

Does all of time already exist if so why can't we see it? [duplicate]

I've recently become fascinated with the theory of relativity and time. If all of time already exists, and there is no difference between past, present and future then what is preventing us from being ...
1
vote
2answers
95 views

Gravitation - Pulling or Pushing force?

According to Newton, gravity is the pulling - or in fact the attracting - force of any heavenly body towards any object to its center. But, to the contrary, Einstein once said that the four dimensions ...
2
votes
1answer
74 views

Travelling at light speed(inside water) [closed]

It is a said fact that 299792458 m/s is the speed limit,nothing can go faster than this speed, or it will take an infinite amount of energy for propulsion.What we perforce in vacuum is one thing.Can ...
4
votes
2answers
122 views

Gravitational lensing in Newtonian physics

Famously, when Eddington attempted to measure gravitational lensing during the Eclipse, it was the measured magnitude of the lensing that gave gravity [pun, obviously, intended] to General Relativity -...
9
votes
2answers
178 views

Is the diameter of the observable universe a relative quantity?

The diameter of my observable universe is 90 billion ly measured in proper distance. But isn't lenght a relative quantity in the theory of Relativity? Could an observer moving at a different velocity ...
2
votes
1answer
33 views

Question about extreme space distortion and creation of a new dimension

In all the illustrations regarding space distortion, I find an extra dimension that depicts space distortion. Is there any mathematical equation that proves the creation of an extra dimension ? ...
3
votes
1answer
94 views

Why is dark energy preferred to the cosmological constant?

Dark energy and the cosmological constant are often identified, but Peebles and Ratra explain that "Einstein did not consider the cosmological constant to be part of the stress-energy term... a ...
3
votes
1answer
37 views

Exoplanets and relativity [duplicate]

Ok, so I have read about how exoplanets are found using all sorts of genius methods. I also understand the further an obect in a telescope is the further into the past I am looking. So given that ...
3
votes
2answers
156 views

Looking for help in understanding how black holes can move

I'm looking for help in understanding how black holes can move through space. This is probably a trivial question for anyone who knows astronomy, but probably due to my lack of education on the topic, ...
16
votes
2answers
1k views

Age of the universe and time dilation

Given our knowledge and the standard cosmological model, we estimate that the age of the universe is about 13.7 billion years old. How much sense does it make to talk about the age of the universe ...
1
vote
3answers
119 views

What is our universe expanding into?

From inflation theory and other theories explaining the birth of the universe, the universe is expanding and recently it's been discovered that the expansion has been accelerating. My question is ...
1
vote
1answer
176 views

Is a black hole a 5 dimensional vortex?

We know that a black hole behaves like a whirlpool or a tornado or any of the other rotating phenomena we experience on Earth.But the thing is, all these phenomena, except the black hole, are 2-...
2
votes
1answer
194 views

Does one need to take into account finite gravity speed in N-body simulations?

Most small-scale N-body simulations (e.g., planetary systems, solar system, stellar clusters, ...) use classical Newtonian gravity. Most large-scale N-body simulations (e.g., galaxy clusters, ...) ...
4
votes
1answer
96 views

What are the exact physical parameters used to calculate Mercury precession with Einstein theory?

NASA measured 43,13 arc seconds per century. General relativity predicts 42,98 arc seconds per century. I try to find out what the parameters' values such as $G$, $M_{sun}$, $\omega_{min}$ at ...
5
votes
2answers
594 views

Observational Evidence for the Existence of Black Holes

What is the direct observational evidence that black holes exist? I have read that black holes have been detected through X-ray emission. What is some other observational evidence for black holes?
4
votes
1answer
92 views

How did the Hulse-Taylor Pulsar Provide Confirming Evidence of General Relativity?

What measurements and observations of the Hulse-Taylor Pulsar agreed precisely with the predictions of general relativity, and how did these measurements support the theory?
4
votes
1answer
363 views

Can A Black Hole Exist?

In 1939, Robert Oppenheimer and other concluded that a certain neutron stars could collapse to black holes and no known law of physics would intervene. As far as I can tell, there is no observational ...
5
votes
2answers
98 views

Are our 'observations' of or near a black hole affected by gravity induced time dilation?

This answer made me wonder if matter/energy/events near a black hole are viewed (by us) in a very different time frame, how might that affect our measurements? ...
6
votes
1answer
131 views

What it would look like to observe people with a different time flows?

As I learned, that the bigger gravity source you are influenced by the more slow time ticks for you, the farther away you are from a gravity source the faster times ticks. So Imagine two different ...