Linked Questions

68
votes
7answers
22k views

Moon's pull causes tides on far side of Earth: why?

I have always wondered and once I even got it, but then completely forgot. I understand that gravity causes high and low tides in oceans, but why does it occur on the other side of Earth?
55
votes
5answers
9k views

Why is the Moon considered the major cause of tides, even though it is weaker than the Sun?

You have likely read in books that tides are mainly caused by the Moon. When the Moon is high in the sky, it pulls the water on the Earth upward and a high-tide happens. There is some similar effect ...
52
votes
9answers
16k views

Are we slightly lighter during the day and slightly heavier at night, owing to the force of the Sun's gravity?

Using $g = \frac{Gm}{r^2}$, the force on a point mass located at 1 AU from the Sun ($m = 2 \cdot 10^{30} \text{ kg}$) is about ~0.006 N/kg. Does that mean that, e.g., a 70 kg person is ~42g lighter ...
48
votes
3answers
3k views

Are there tides in the atmosphere?

Analogous to the tides of Earths oceans, do the Moon and Sun cause our atmosphere to bulge in what could be described as a low and high tide?
47
votes
4answers
11k views

Why do some location on Earth have only one tidal maximum per day instead of two?

Most places in the ocean have two high tides and two low tides per "day" (~25 hours). But I remember reading that some locations only have one of each per day. This answer has some great explanations ...
41
votes
7answers
7k views

If the ground's normal force cancels gravity, how does a person keep rotating with the Earth?

When I am on earth, the weight of my body is countered by the reaction of the ground. So, there is no net force acting on me. But I am spinning with earth. But if there is no centripetal force then ...
17
votes
1answer
8k views

Why don't lakes have tides?

There's a tidal effect that we can clearly observe in oceans, which is the effect of gravity from the Sun and the Moon. If gravity affects everything equally, why don't lakes have tides?
11
votes
2answers
2k views

Explanation of the waves on the water planet in the movie Interstellar?

We will ignore some of the more obvious issues with the movie and assume all other things are consistent to have fun with some of these questions. Simple [hopefully] Pre-questions: 1) If the water ...
8
votes
1answer
2k views

What is the reason of the semidiurnal pressure oscillation in the atmosphere?

It appears that in many (most) places on earth, a pressure oscillation of a 100-200 Pa takes place twice a day : that is, with maxima around 12AM and 12PM and minima around 6AM and 6PM. I've found ...
7
votes
3answers
2k views

Relative size of the 2 tidal bulges

I am interested in making a simplified model that represents only the effect that the moon has on Earths tides. In this model I am going to assume that the earth is completely spherical (with no ...
5
votes
2answers
1k views

How does angular momentum transfer between a planet and its moon?

Could you explain how a moon draws angular momentum from a planet? I know that the gravitational force transfers momentum, but I don't understand the mechanics behind it.
5
votes
1answer
6k views

Conservation of angular momentum in Earth-Moon system

We all know about the fact that tidal friction is slowly slowing down the Earth's rotation about its axis, and that subsequently the Moon is slowly drifting away, in order for the angular momentum of ...
5
votes
1answer
153 views

Will extracting power from ocean tides affect the moon's orbit in the LONG run?

Conservation of energy says that any energy extracted from our ocean's tides would have to come from somewhere. Since these tides are a gravitational effect due to the moon, it would seem that the ...
5
votes
3answers
1k views

Tidal Forces Misunderstanding [duplicate]

I'm sure there are several misconceptions here and I'd greatly appreciate it if someone could help me identify and correct them. When calculating tidal forces across an object, the earth for example, ...
3
votes
2answers
1k views

How does the Moon cause the tides?

I am considering the following question, but I can't quite figure it out... I have looked up differential gravity, but I cannot derive the equation for the effect on Earth, and I haven't found any ...

15 30 50 per page