All Questions
40
questions
0
votes
2
answers
43
views
Stars that have fairly high gravitational redshift and calculation of their surface temperature by Planck emition spectra?
How high can the ratio between gravitational redshift and planck emition spectra be depending on the mass of the star so by how much this gravitational redshift could elongate the Planck spectra of ...
- 2,255
0
votes
2
answers
50
views
Observing an event horizon while approaching one
A thought crossed my mind that I realized was hard to conceptualize so I decided to simplify the question by putting it in terms of event horizons.
If I am an observer approaching black hole "A&...
- 101
0
votes
0
answers
51
views
Can gravitational waves be compared with a sinking water phenomena?
Let's say we have some water in the sink and open the closure. The water starts to move towards it in a whirlpool-like manner. If we have a table tennis ball and leave it near the hole of the sink it ...
- 2,255
0
votes
2
answers
92
views
Time of collapse of stellar dust cloud
A stellar gas cloud collapses onto itself once it reaches Jean's mass, and the time it takes for said cloud to collapse is given by: $t_{coll}=\sqrt{\frac{3\pi}{32G\rho_0}}$, where $\rho_0$ is the ...
- 1,616
0
votes
1
answer
186
views
Rotation affecting how spacetime is warped (according to general relativity)?
According to this excellent ScienceClic video, satellites don't fall straight towards the center of the Earth, but rather, take a curved path, due to the Earth rotating. A similar thing for black ...
- 1,090
1
vote
1
answer
47
views
Based on structure formation and the lifetime of the universe why is there an upper bound on the cosmological constant?
I understand that significantly greater values than the cosmological constant would result in difficulty for the formation of large gravitationally bound structures within the lifetime of the universe....
- 51
1
vote
0
answers
71
views
State of the art on relativistic perihelia precession in Solar System (other than Mercury)
The correct prediction of anomalous precession rate of Mercury perihelion is a classical test of General Relativity and one of its' big triumphs. How about other planets in the Solar System?
...
1
vote
1
answer
29
views
Doubt regarding solving an integration for radial flow of matter around a star in Newtonian gravity
The spherically symmetric flow of matter around a star in Newtonian gravity is governed by the equation
$$v\frac{dv}{dr}+\frac{1}{P+\rho}\frac{dp}{dr}+\frac{1}{r^2}=0$$
The equation of state is chosen ...
- 2,015
1
vote
4
answers
152
views
So what actual physical event would allow us to observe the speed of gravity?
I have read, if the sun disappeared it would take 8 minutes before this could be detected on Earth due to speed of gravity being $c$. Of course, the sun can't disappear. Perhaps realizing this ...
- 2,238
1
vote
2
answers
98
views
Will Earth be devastated when the orbit shifts 1 metre towards the Sun? [closed]
There are some arguments in my country from a population that they are "religious". Then, their argument is that there is a perfect balance in universe and solar system.
Hence they say that Earth ...
- 65
0
votes
0
answers
19
views
At what point in size does gravity force a celestial body to become "round"? [duplicate]
I am watching a video on asteroid size comparisons and I noticed that 2 Pallas (512 km) and 4 Vesta (525 km) are both "spherical" in shape (pretty much anyway). However 52 Europa (319 km) is also ...
- 2,706
3
votes
1
answer
47
views
Does the curvature of light around a "centre star" in gravitational lensing affect the age at which we view the object being "lensed"
It occurred to me that during gravitational lensing, the light curves around a given object, creating a curved path. Because the path of light is curved, and thus, longer than a straight path, would ...
- 33
1
vote
1
answer
160
views
What imparts the linear motion or the tangential velocity to natural satellites like the moon to enable them to be in orbit around the earth?
From Newton's laws of motion & gravitation, it is clear that the force of gravitation provides the necessary centripetal force which acts along the line joining the centre of masses of the earth &...
- 21
3
votes
1
answer
122
views
Why does stellar rotation not shred the Chandrasekhar limit?
Investigations in the 60'ies about the question how the Chandrasekhar limit is modified by allowing a self-gravitating mass of cold fermions to rotate seem to have come to the conclusion that the ...
- 643
0
votes
1
answer
161
views
How does gravity affect lower dimensional objects (1D - 2D)?
How does gravity affect lower dimensional objects such as 1-dimensional strings or a BH's 2-dimensional event horizon, knowing already that it warps the 4D construct of space-time?
