Tagged Questions
2
votes
1answer
96 views
What are we all falling towards?
One meteorite fell on the ground in Russia, last week. In different circumstances, it could have orbited the earth, or perhaps pass close to the earth and then disappear into the space.
It seems that ...
13
votes
2answers
268 views
Why aren't gas planets and stars fuzzy?
The edge of Jupiter looks very sharp.
Even more bothersome, the edge of the sun looks sharp, aside from kind of a soup of particles floating above it.
The sun's surface has an incredibly low ...
1
vote
1answer
99 views
If there was no Earth, what would be the acceleration of gravity from here from the Sun?
Suppose there were no Earth to pull us back and we're hanging in the solar system. Assuming no other force of gravity from other bodies, what would be the $g$ from the Sun?
6
votes
3answers
230 views
Tidal force on far side
I have a question about tidal forces on the far side of a body experiencing gravitational attraction from another body.
Let's assume we have two spherical bodies $A$ and $B$ whose centers are $D$ ...
1
vote
1answer
726 views
What is the relationship between mass, speed and distance of a planet orbiting the sun?
After reading this fascinating story about a new exoplanet, I was wondering about how mass, speed and distance determine a circular orbit of a planet around a star.
Given the mass of the sun and ...
2
votes
1answer
290 views
Combined Gravitational Force Vectors in a Spherical Coordinate System
Asking a question here is quite intimidating for me -- while I love Physics, my high-school understanding only allows me to go so far... I've been trying to solve this problem for the last couple of ...
3
votes
1answer
367 views
About binary stars and calculating velocity, period and radius of their orbit
I saw somewhere about being able to measure the velocity, period and radius of a binary star orbit by looking at red shift and blue shift.
I understand it but can someone give me an example of ...
2
votes
1answer
117 views
Gravitational sphere
I was reading this article that mentions a blackhole as having a gravitational sphere of 4,000 light-years.
I'd not heard of the term (gravitational sphere) before ...
3
votes
2answers
44 views
Computing period, semi-major axis of binary
I have mass, $g$, and luminosity of each of the stars in a binary system, extracted from a model. I calculated the individual radii from $g$ and the mass. I am trying to compute $a$, but I seem to be ...
8
votes
5answers
3k views
Stephen Hawking says universe can create itself from nothing, but how exactly?
Stephen Hawking says in his latest book The Grand Design that,
Because there is a law such as gravity, the universe can and will create itself from nothing.
Is it not circular logic? I mean, how ...
1
vote
2answers
434 views
What is meant by positive and negative gravity/energy/spactimecurvature?
I have recently come across some cosmological assertions (based on empirical data) about the universe being self contained in the sense that it is entirely capable of coming into existence from a ...
4
votes
1answer
831 views
Gravity and Planetary Differentiation
During solar system formation, many bodies achieved hydrostatic equilibrium, a spherical shape where their self gravitational force was balanced by internal pressure. Many also achieved ...
7
votes
2answers
2k views
Why does Venus rotate the opposite direction as other planets?
Given: Law of Conservation of Angular Momentum.
Reverse spinning with dense atmosphere (92 times > Earth & CO2 dominant sulphur based).
Surface same degree of aging all over.
Theoretical large ...
7
votes
1answer
148 views
Mass Needed to Clear an Orbital Neighborhood
In 2006 the IAU deemed that Pluto was no longer a planet because it fails to "clear" the neighborhood around its Kuiper Belt orbit. Presumably, this is because Pluto (1.305E22 kg) has insufficient ...
3
votes
5answers
1k views
How do we know that earth moves around sun and that too in elliptical orbit
I know the basics of solar system like how earth moves around sun, and that we have so many planets, elliptical orbit of earth, and how far is sun from earth etc etc. I want to take a step back and ...
-2
votes
1answer
412 views
History of Man Acquired knowledge of solar system [closed]
I know the basics of solar system like how earth moves around sun, and that we have so many planets, elliptical orbit of earth, and how far is sun from earth etc etc. I want to take a step back and ...
