Gravity Definition and 1000 Threads

What I understood is that The Schwazschild metric is obtained by setting spherical symmetry in the metric and solves the field equation in vacuum. But is the flat metric a solution too, or does it mean that changing the coordinates induces gravity ?

I'm armchair knowledgeable about GR, but I've come up against something I can't eloquently explain (to someone who asserts otherwise and wants an unassailable answer). What property results in time dilation even when net gravity is zero?The net gravity at the centre of the Earth is zero, but...

Thought you all might be interested in this article. It could just be hype, but there also might be something deeper to it. You hear of so many schemes of tying together quantum mechanics with a relativistic understanding of gravity, that it's easy to respond to yet another announcement like...

I am wondering why gravity needs to be unified with the other three forces into a super-force. Why can't the three forces be seen as interactions between particles in a space-time fabric whose geometry gives the impression of gravity?

This is probably a fairly simple question, but I am struggling with it. My question is: Would you experience the effects of gravity if orbiting in a stable or circular orbit close to a black hole? This stems from my mental image of the International Space Station (ISS). There is obviously...

Greetings: I can understand that an object's trajectory curves about a greater mass (e. g., satellite in Earth's orbit). The spacetime is curved via the great mass and the moving object simply follows the curvature. My problem is this: Why does a stationary object at a short distance from...

This has been bothering me for some time, and would like to get a physicist's view of it. If my understanding or contention is in error, please correct me (gently). I only have under grad physics from 1970, and was a microbiologist, though am interested in quantum physics, cosmology. My...

Warning: I'm a freshman chemistry student. My math skills are elementary at best. Image a ball in deep space. A baseball sounds nice. Assume this ball had no initial velocity but suddenly finds itself caught in the sphere of influence of a massive body. A black hole sounds fun. The ball begins...

The equations for gravity vary differently depending on the distances involved: Inside a body, such as a planet, the weight varies directly with the distance from the center - as r. Outside of the planet or sun, gravity varies as the inverse square law - as 1/r^2. At distances at the edges of a...

Salutations, I have been trying to approach a case about projectile motion considering variation of gravity acceleration and air resistance: A spherical baseball with mass "m" is hit with inclination angle $\theta$ and launching velocity $v_0$, then, the wind has a drag force equals to ##F=kv##...

Ok so I've asked my physics teacher and a statics teacher as well and I couldn't get a straight answer from either. So here's my questions... Correct me if I'm wrong, but isn't the gram a unit of mass? Not weight? I thought that for mass to become a unit of weight, it has to have to...

In Einstein's thought experiment (if I understand it correctly) a person in a sealed elevator in space accelerating at 9.807 m/s2 would not be able to tell the difference between that and the effect of gravity on Earth. Is there any sort of experiment the person in the elevator could do that...

Homework Statement In a distant galaxy, a planet orbits its sun at a distance of m with a period of 108 s. A second planet orbits the same sun at a distance of m. What is the period of the second planet? Select one: a. s b. s c. s d. s e. Homework Equations T^2=constant * r^3 The...

To date, the most accurate verification of the time effect of gravity is where two satellites were accidentally put into elliptical orbits where the altitude varied by 8,500 kilometers ( 5,282 mi). Their atomic clocks ran slower near Earth and faster at higher altitude. The agreement with GR was...

I have read in several popular physics texts that general relativity predicts that gravity deflects light, but that Newtonian mechanics, in contrast, predicts that the trajectory of light is not affected by gravity. However, I am very skeptical and confused about this result. We of course have...

Is there any thing like perceived gravity in circular motion?? If I consider that it is in opposite direction to centripetal force, then both perceived gravity and centripetal should cancel each other and object should move in a straight line. Why does it nit happen?

Why do I keep hearing gravity does not fit into the standard model of physics?

One approach that has been proposed to replicate the description of dark matter phenomena in galaxies with a gravity modification that is set forth in a simplified manner in the phenomenological toy model theory MOND is to do so through a variation on Einstein's General Relativity known as...

Hi, It is usually claimed that a person in an accelerating elevator with an acceleration equals to the gravity of the earth; this person cannot make any experiment that makes him know whether he is in the elevator or on the surface of earth. However, if this person project two light beams...

I would like to know if this group http://www.quantumgravityresearch.org/ and its Emergence Theory has any standing in main stream Physics. Thanks Andrew

Is there a connection between the inverse square law of gravity and the time-squared rate that bodies fall (i.e. (32ft/second)/second))?

since it is known that ##\vec{A_\perp} = -{mG \over R^2}## why did the professor write it as ##\vec{A_\perp} = {- R G \rho \over 3}## for perfect sphere with perfect mass distribution ? Shouldn't it be ##\vec{A_\perp} = -{4 \over 3} \pi R G \rho##? I need help thanks.

Take some sort of system accelerating with respect to an inertial reference frame: let's take a spherical mass on the end of a string forming a simple pendulum with the ceiling of a car, and allow that car to accelerate uniformly. Could someone share with me how they interpret the concept of a...

I need help with a question on my homework about circular motion. It goes like this: - Starting from Newton's Second Law, develop an equation for the stopper that relates the force of gravity to the period.

I'm working on a story set on the moon post-industrialization. The moon has an orbital ring with a spinning exterior to simulate Earth gravity. People work on the surface in lunar grav, then go up to live on the ring under conditions more favorable for human bodies. Two questions I need to...

Consider a spherical planet of uniform density ρ. The distance from the planet's center to its surface (i.e., the planet's radius) is R. An object is located a distance R from the center of the planet, where R < Rp. (The object is located inside of the planet.) 1) Find an expression for the...

I am still learning general relativity (GR). I know we can find the path of a test particle by solving geodesic equations. I am wondering if it is possible to derive/convert metric tensor to gravity, under weak approximation, and vice versa. Thanks!

I have a question related to MOND and DM that I will post here rather than create a new thread. My thought stream begins with doesn't Energy create gravity as well as matter due to the E = MC^2 equation? Which leads to my question of whether or not empty space generates gravity due to the energy...

So I'm trying to help someone get an idea of the 'scale' of some of the most massive black holes, but, I'm at best a laymen when it comes to this stuff. Because ISCO for a non-rotating black hole is just 3 times it's radius, and I can calculate apparent arc radius from ISCO, I could tell them...

I just read a couple articles discussing the surface gravity of Saturn and Jupiter. I would expect the "surface" gravity of these planets to be much higher than that of Earth. I understand how the low densities of these planets has influence on that, but I thought mass was related to gravity in...

If a photon does the 4 things listed below, why do we say it doesn’t have mass? I guess I’m asking if there’s a clear definition of mass. follows geodesics in spacetime (classically: accelerated in a grav field), curves spacetime (classically: creates a gravitational field), has momentum /...

Homework Statement Block A is on top of Block B, both are of equal mass and size. Block B is being pulled by a hook at a constant velocity. There is friction between the table and block B. Homework Equations [/B] What will each FBD look like? Is there friction between Block A and Block B...

My teacher say: Comparisons between the pressure of an object on the inclined plane and the gravity of the object But idk what is sin and cos means I need help THANKS from: vietnam

Hey I have a question and I’m sorry if some of you might find it too easy xD... How did people calculate or discover the gravity constant, and how do they know how much do planets weigh? Thanks for answers

They say gravity is because mass stretches space time and it makes matter fall to it and can prove it. And that makes sense when there is a lot of mass. But they say stars are made from gas clouds mostly hydrogen and helium very small atoms that start to clump together. So a star starts out a...

After I read Martin_K's post of 4:14 Oct. 30 on the frozen image of an object just before it fell through a black hole's event horizon, the next few minutes I was jumped by a handful of related ideas. First, the frozen image scenario is illustrative because when photons are frozen in place...

We get this type of question now and then, even in the main physics forums. One such question in the Sci Fi forum is from this one: https://www.physicsforums.com/threads/what-is-the-largest-possible-rotating-wheel-space-station.950770/ So I don't know of people have seen this video from a few...

Homework Statement We drill a hole from the surface of the Earth to the other side through the center, drop a test particle and measure the time it takes to come back. How does this time depend on the radius and density of the Earth? Homework EquationsThe Attempt at a Solution The gravitation...

If gravity of the Earth is so powerful to hold the moon in orbit, why does she not drag in & squash to smitherings all on its surface? Please forgive my ignorance, ......nick

Hello, In the wikipedia article about solar sails the lightness number is mentioned and the calculation is the characteristic acceleration ac divided by the Sun´s local gravity (distance: 1AU): λ = ac / 5.93 why do they use 5,93 m/s^2 for the sun´s gravity and not 274 m/s^2?

So I have sort of a conceptual question about the big bang and gravity. Imagine yourself in a universe, in which existed about the number of particles/energy in a 3X3 metre room at any given moment. This universe has the same laws of physics, constants and is identical in every way to our...

Zero gravity. We can hear about the zero gravity chamber , zero-g flights on aeroplane and lots of other stuffs about zero gravity on earth. How does it actually works? Can it be possible for us to make it?

Hey there, If body 1, mass M1 has escape velocity V_e1 = (2GM1/r)**.5 but M2 is more massive than M1 is this relation still valid? In this case, the subordinate body really isn't the subordinate body so does this still hold? And r (distance b/t the two) changes not only due to the motion of M2...

There is a an encyclopaedia of all the different inflationary models. But I am wondering is there is a similar list of modified gravity models ?

Homework Statement G= 6.67 *10^-11 M= 5.97*10^24 kg m= 430 kg Orbital speed=6800m/s I'm supposed to find radius of satellite orbit. Homework EquationsThe Attempt at a Solution I don't know where to start because in order to find radius, I have to find period as well

I just read a book by nuclear physicist Carlo Rovelli on the subject of "Time" and he says that 'entropy' is the only non-reversible process in the basic equations of physics, and he believes time and entropy are related (if I understand him correctly). So this started me thinking on entropy...

If the Earth orbits the Sun due to the difference in their mass and their distance, then do atoms like air particles orbit humans due to the same reasons?

I have several questions about the Newtonian equation for Gravity Gm1m2/r^2. First, I want to point out this equation is only valid for point masses or when the two objects are sufficiently far apart.This is because the r squared term on bottom means that the relationship between force and...

Homework Statement https://i.hizliresim.com/Bzp05M.jpg " spacecraft " Now you're in other space.No gravity at all.You 're going to make your own artifical gravity R = 100m Quest 1-) With which angular velocity, g is equal to 10 (g = 10) 2-)Can you walk from b to a? Why is that 3-)Can you...

It is often proposed that gravity could be simulated on a space station by rotating around an axis, such that the astronaut experiences the centripetal force of the space station wall, analogously to gravity. It is usually mentioned that the radius of rotation must be very large to avoid...