All Questions
55
questions
1
vote
4
answers
160
views
Gravitational attraction between two bodies
While the gravitational force between two bodies is directly proportional to their masses, and inversely proportional to the distance between them is understandable / seems logical, how did Newton ...
- 123
1
vote
2
answers
47
views
Is it possible to determine if a planet can have a moon based on its mass and gravitational pull?
I'm curious, if based on what we know with Newton's law, can we determine if a random planet, knowing it's mass and gravitational pull, can hold a moon in it's orbit.
Or to phrase it another way, is ...
- 111
1
vote
0
answers
41
views
Did Newton derive Titius-Bode Law of the planets in his Principia? [closed]
In college I was taught that no one knows why the planetary orbits conform to the Titius-Bode Law.
Recently I read that Newton HAD figured that out in his Principia.
Right Now I can’t even find a ...
- 11
2
votes
1
answer
290
views
What is the rate of change of the Moon's eccentricity?
So I know the Moon's current average eccentricity is ϵ≈0.039±0.006, but was this always the case? Was it ever increasing or decreasing, and if so is it known what the current rate of change is for it? ...
- 161
0
votes
0
answers
43
views
Why are the orbit of planets usually ellipses? [duplicate]
There has been a similar question about planets' orbits being ellipses but the answer circulates around how the circle is a special type of orbit which doesn't really answer my question.
Elaborate ...
- 159
1
vote
4
answers
94
views
A problem Understanding how a two-body system of planets starts rotating around barycentre
Consider,We are Creating a Two-body system in free space,Where no other mass exists,Let's Take First Mass M1 and hold it,Now bring Second Mass M2,hold it up,Now we are giving a suddenly impulse To M1 ...
- 452
-2
votes
3
answers
149
views
Why is the shape of the orbit of the Earth as it is?
My View: I think that if the sun were only force acting on earth (as a centripetal force), the earth would have a circular orbit. Since other planets also exist , there also exists gravitational force ...
- 159
0
votes
0
answers
505
views
Does the formula $v = \sqrt{GM/r}$ work for elliptical planetary orbits?
Suppose we have a central mass $M$ and a smaller mass $m$ orbiting around the central mass in an ellipse:
The other point is the other focus. We know that elliptical orbits have the central mass in ...
6
votes
3
answers
745
views
Basic question about orbital speed
I was reading a Sci-Fi book recently and had a weird thought:
I know that objects closer to a gravitational well need to move faster to stay in orbit and objects further away move slower. But if you ...
- 81
0
votes
2
answers
753
views
How to derive Kepler's third law of planetary motion using angular momentum of Earth around the Sun?
While I was trying to derive Kepler's third law of planetary motion, I tried the gravitational force for the Earth method which goes something like this:
$$\frac{mv^2}{r}=\frac{GMm}{r^2}$$
$$\...
- 115
3
votes
2
answers
1k
views
Time spent by a comet inside the Earth's orbital (Kepler problem re-visit)
I come across this interesting problem comet-x-earth. It was an exam problem asking the time that a comet will be spent inside the Earth's orbital. I make an illustration for the problem:
The comet ...
- 4,276
1
vote
1
answer
60
views
Understanding the third Kepler law [closed]
Consider a system of two masse $M$ and $m$ with $m<<M$ and the mass $m$ orbiting around $M$. Then $m$ describes a elliptic orbit with period $P$ and the third Kepler law states that:
$$\frac{P^2}...
- 183
0
votes
1
answer
259
views
Orbit eccentricity and initial velocity
I was thinking about orbital velocities, and came across this question (Velocity of satellites greater than required velocity). Does the answer to this question imply that for planets going round the ...
- 141
1
vote
2
answers
5k
views
How do scientists calculate the orbital period of a planet?
It is known that you can calculate the distance to a planet using parallax, but how do scientists calculate the orbital period of a planet?
(Assuming they don't know the distance and can't use Kepler'...
2
votes
2
answers
479
views
What determines if an object will stay in a planet's orbit? [duplicate]
Say you threw an object 10 AU from a planet at a certain speed, would this object stay orbiting around the planet or would it shoot off into space? And does it depend of the speed the object when it ...
- 31