Earth Definition and 1000 Threads

I am interested in theoretical (what if) possibility of our Earth having more than one moon, I wonder if they can be arranged at the same orbital resonance as the Galilean moons 1:2:4 If yes, would such system be stable? If yes, should our Moon be the first, second or third satellite out of the...

Homework Statement Two small, equal masses are attached by a lightweight rod. This object orbits a planet; the length of the rod is smaller than the radius of the orbit, but not negligible. The rod rotates about its axis in such a way that it remains vertical with respect to the planet. • Is...

I was thinking about a situation where we lived in a cubical earth! (Gravity is such that people at each surface will still feel that they are standing upright). I came up with some interesting situations like when a ship crosses an edge or throwing a ball from the edge of surface... What would...

I read that a non rotating planet like Lubricon VI does not have equator because it does not rotate. So why only rotating planets have equator?

Homework Statement Does that container full of water gives a torque on Earth ? http://imageshack.com/a/img537/6733/9Y0Hqq.png Homework Equations -- The Attempt at a Solution I drawn all interesting forces : http://imageshack.com/a/img540/9315/ymwwvW.png Like that there is a torque...

Tangential speed is the linear speed of something moving along a circular path. So for a satellite the tangential speed of the satellite is just right so that gravity only has the effect of changing the direction of travel. So now can we compare this satellite to the Earth? Since the Earth has...

I was thinking of the conditions exerted at the center of our Earth. If a man let's say in America falls toward the Center of the Earth and a man on the opposite side of the Earth falls, where would they meet? I read that the gravitation force at the center of the Earth is at 0. If they both...

Homework Statement I'm trying to show that any tunnel through the Earth (not necessarily through the center) will have a free-fall time that is the same. I heard this was true somewhere. Homework Equations acceleration of free-fall = GM / r^2 where r is changing I believe this involves trig...

Hi, I wonder if anyone can answer the following: - What constellation would our sun appear in if viewed from Epsilon Indi? Thanks in advance Chinspinner

Hello! I am currently starting my thesis, and I would be pleased if you could help me. As it is an ficticious force for non inertial frame, the Euler force affects every movement measured from the surface of the Earth. But, it is related to the angular acceleration changes of our planet, so...

I think I read somewhere that Feynman once said that if we could measure the earth’s diameter, it would be maybe an inch short of what we would expect from the circumference and Euclid. Is that correct? (Did he actually say that?) It seems to me that it would be a tad longer?? I see a clock...

Hi guys, There are many calculators and applications out there that can calculate you the distance between Earth and Mars at every time, but I'm trying to find the actual function that gives me so and draw the path of it. My objective is finding the distance R (and Phi of t), as shown below...

Hi all. The answer to this might be trivial. If it is, sorry for posting. If you calculate the acceleration due to gravity of an orbiting satellite, it could be around 8.5-9.5m.s-2, depending. So, it's tangential velocity is such that as it falls towards earth, Earth curves away and the...

Homework Statement So, if the Earth stopped moving(supposing Earth's orbit is a circle) how much time would it have to pass before it hit the Sun? Homework Equations I've tried with Kepler, and Newton's derivations of Kepler's 3th law The Attempt at a Solution Well I'm pretty sure you need to...

Hi guys, My professor showed us in class how to find the final velocity of an object as it hits the the atmosphere of earth(Rf=6.37e6) and I think he might have made a mistake. I have been trying to solve the same problem but I get different answer than the one my professor showed in class. The...

Hello, Gravitational length contraction inside Earth means, the measuring rod is also shortened and in consequence inside is more space than according to the mathematical circumference of an empty geoid. I´d like to know something about this discrepance: mathematical diameter - physical...

The question is simple, was life able to recover from the very long and cold "snowball earth" epoque, which means that Earth was not completely sterile during that period, or, when climate became warmer, life simply reborn again - from scratch?

I've been playing Kerbal Space Program. I have found the simplest way to get to an outer planet is to launch straight up at dawn and the simplest way to get to an inner planet is to launch straight up at dusk, and in neither case to mess about with going into Kerbal orbit. This got me to...

If we travel 100 km vertically from the surface of the earth, will we no longer be pulled by Earth's gravity and float into space? Same question as above yet with 1000 km. How far up vertically do we have to go to escape Earth's pull and how wide/long is the Earth's gravitational influence. Does...

Homework Statement I already searched for solution and i found similar one but I'm still confused. -In which point between Earth and Moon gravity field equals 0 if distance between moon and Earth is 60.3 * radius Earth and mass of the Earth is 81 * mass of the moon. Homework Equations...

Good Evening to everyone! I'm currently a student of theoretical physics. I have a Bachelor Degree in Physics and I'm from Italy. When you finish your B.D. you can choose to go on with your studies in order to get a Master Degree (other 2 years of study) and here you can choose your curricula...

Hi all, This is a bit of a bizarre question, but: If some way, some how, the moon crashed into Earth... then (oh so many) years later humanoid life appeared, what might its bone structure be like in contrast to ours? That is all

If there was no Sun then the Earth would move in a straight line with constant velocity. This is because the space has vacuum and there is no friction in space. This is because if you observe on Earth where there is friction we need to apply force against this friction. But in space there is...

Hello all, I have a question about space debris. The number of space debris in the low Earth orbit is huge.There are more than 170 million pieces of space debris which is greater than 1mm. So in the orbit of the Earth, what is the average distance between 2 pieces of space debris?

Homework Statement A) Suppose you are on Earth's equator and observe a satellite passing directly overhead and moving from west to east in the sky. Exactly 12.0 hours later, you again observe this satellite to be directly overhead. How far above the Earth's surface is the satellite's orbit...

Puma Punku in bolivia and Peru amazing stone cutting make me suspect aliens had done that , cuts are so precise and so impossible to realize today with our ''modern technology incline to think of a desintegrator cutting tool ( energy field that break atoms bonding )

I know that the the satellite will lose speed(due to perhaps small air resistance), and therefore lose centripetal force? I am not sure how losing centripetal force and speed causes the satellite in orbit to lose radius. If force is the same, and velocity is lowered, than radius would increase...

According to this video, a bowling ball and a feather fall at the same rate because according to Einstein, they aren't falling: https://testtube.com/dnews/which-falls-faster-a-feather-or-a-bowling-ball/?utm_source=FB&utm_medium=DNews&utm_campaign=DNewsSocial What does this mean exactly? The...

Homework Statement On Earth, an average person's vertical jump is 0.40m. What is it on the Moon? Homework Equations Fg 1 on 2 = G(m1m2/r^2) G= 6.67 x 10^-11 The Attempt at a Solution r= 0.40m F Earth on person on Earth's surface = 6.67x10^-11(m Earth x m person)/(0.40)^2 r=? G moon = ? F moon...

If aliens collapse a previously stable traversable wormhole that is situated at roughly the location where the ISS is located, and that wormhole then becomes a black hole, how long would it take for the Earth to be drawn into its singularity and utterly destroyed? Also, let's say humans have...

If we take in account that magnetic and geographical Earth poles are not completely identical and therefore magnetic poles suppose to rotate around geographical with some speed, could we harness at least a bit of energy from it? For example if you are on the South geographical pole, the South...

Homework Statement Hey guys, I have a problem where we measured the gravity on separate floors of a building using a gravometer. It gave us values in mgals. So each floor has a distance of 0.5m. How do we take this into account as we move up and down the floors? As we move up, there's and...

Hi all I just started doing some research on special relativity and I figured something. If two people both reset their watches. One person goes around the Earth once, doesn't matter at what speed, and the other person stays there. The watch of the person that went around the Earth will run...

Apart from the the gravitational pull of the Moon and the Sun on the Earth, does the rotation of moon contribute to the tides?

Homework Statement In this question, the Earth is modeled as a uniform sphere of radius 6400km. Objects are released from points just above the Earth's surface at the equator and at the North Pole. Which will fall to the Earth with the greater acceleration and by how much? Homework Equations...

Homework Statement A small ball of mass 'm' is released at a height 'R' above the Earth's surface. The maximum depth of the ball to which it goes is R/2 inside the Earth through a narrow groove before coming to rest momentarily. The groove contains an ideal spring of spring constant K and...

This problem is actually an example I'm working through... 1. Homework Statement We are trying to estimate the (magnitude of the) electric field in the light waves from the sun hitting the surface of the Earth. Homework Equations The Poynting vector for a sinusoidal EM wave has magnitude...

Homework Statement The acceleration of gravity on the Moon is 1/6 what it is on Earth. The radius of the Moon is 1/4 that of the Earth. What is the Moon's mass compared to the Earth's? Homework Equations F_g = \frac{GMm} {r^2} => mg = \frac{GMm} {r^2} => g = \frac{GM} {r^2} => M = \frac{gr^2}...

Homework Statement The temperature within the Earth's crust increases about 1.0 C∘ for each 30 m of depth. The thermal conductivity of the crust is 0.80 W/C∘⋅m. A)Determine the heat transferred from the interior to the surface for the entire Earth in 9.0h . B)Compare this heat to the amount of...

I have a friend who vigorously believes in hollow Earth theory. Your typical dreaded up conspiracy theory hippie type. I've looked around the internet and know there are threads similar to this but I'd like to open up a discussion here. How would one disprove hollow Earth theory? I can't imagine...

Hello, I am looking for a website that contains information such as the interval between Earth and uranus' closest approach. I can't seem to find exactly what I am looking for, so I was wondering how difficult it would be to calculate this. I am at a loss where to start though... Any pointers...

Homework Statement A satellite has a circular orbit 500 km above earth. A ball is thrown directly downwards radially at 20 m/s. Find the path of the ball relative to the satellite. Homework Equations mv^2/r=GMm/r^2 The Attempt at a Solution From the height of the orbit you can easily solve...

I was wondering If anyone knows if this is possible, or why it might be a silly idea.

It's generally said that a moon walker should be able to jump six times higher on the moon, than he can on Earth, which sounds sensible since gravity is one sixth , but consider this... Two men , one on the Earth, one on the moon, both bend their knees the same amount ready to do a 'standing'...

Not sure if this is the right place or if I can even frame this question sensibly. But here goes. I notice when driving in my car that the sensation of heat on my skin from the sun shining through my windsreen seems to be different between the seasons. Much hotter in summer versus cooler in...

Just finished this series on DVD. That was spectacular! I'm a little sad/surprised it didn't mention Apollo docking to Mir, or the shuttle visiting Mir. But it was great to see that bit about Skylab; I never knew that. And I always thought the Hubble repair mission happened after Columbia. I...

I am trying to understand why is the surface of the Earth negative. From the internet search, I found -105 C. I make a sequence according to the conventional model and question at each step. 1. The surface is slightly negative: here I just accept and start. 2. Atmosphere is positive: Some...

Homework Statement If the Earth did not spin on its axis, would the other planets still appear to move across the sky? Justify your answer. Homework Equations N/A The Attempt at a Solution If the Earth continued to rotate around the sun but NOT on it's own axis then wouldn't...

I have some confusion understanding some concepts of Earth moon system . Why conservation of momentum requires both the Earth and the Moon to revolve around the centre of mass ? What happens if they do not revolve around the centre of mass ? Plz clarify and guide me .

Homework Statement A pendulum has a period of 4.50s on Earth. What is its period on Mars, where the acceleration of gravity is about 0.37 that on Earth? (2 sig figs) Homework Equations T= 2Pi(L/g)^.5 The Attempt at a Solution first must solve for the length on earth L =...