# Tag Info

## New answers tagged earth

0

The Earth's orbit remains pretty much the same from year to year. Each year takes the same amount of time - about 365.24 x 24 hours. The trouble for calendar makers is that this is not a whole number of days. If we just rounded it off to the nearest day then, over time, New Year's Day would arrive a bit earlier each year compared to the seasons. For ...

2

No. It's due to inaccuracy in the calendar. In a nutshell, Earth's orbit actually takes 365 and 1/4 days. So every four years, we add an extra day so the calendar doesn't get all out of whack. Of course, it gets more interesting than that. When I said it took 1/4 of a day longer than the calendar allows for, it actually takes a few minutes longer (11, to ...

1

Is Earth's orbit changing? Yes. But not large enough to alter our calendar in near future Well, there are some long-period oscillations, but those are very small, and don't imply that we're systematically moving towards or away from the Sun. There is an effect which is making us move very slowly away from the Sun. That is the tidal interaction between the ...

0

Have a read of Wikipedia Leap year A common year has 365 days and a leap year 366 days, with the extra, or intercalary,day designated as February 29. A leap year occurs every four years to help synchronize the calendar year with the solar year, or the length of time it takes the earth to complete its orbit about the sun, which is about 365¼ days. So ...

1

Coriolis force on a moving object originates when you look at its motion from a non-inertial reference frame. Earth is a non-inertial reference frame, but that fact alone is not sufficient to cause Coriolis force on air. Air must also be set into radial motion by some agency, that agency being our Sun, as pointed out by @James Rowland and @CuriousOne.

4

The Earth+windmill system has conserved angular momentum. When the windmill starts spinning the angular momentum of Earth must change in response. However this change is marginal. Furthermore the windmill system will stop spinning when the wind dies down and this will restore the original angular momentum of Earth (when I say Earth I mean everything inside ...

1

Short answer: the changing composition between silicate-rich mantle and iron-rich core means the melting temperature does not increase sufficiently for the iron/nickel outer core to remain solid. The ability of something to solidify is a competition between the potential energy associated with the atoms that would occupy a solid lattice versus the thermal ...

1

This is an interesting question and one that probably needs detailed simulation to settle. But one can make the following broad prediction: the shape of the meteorite would have minimal effect on the outcome, for the following reasons: At the kinds energies let slip in the moments of impact and the kinds of pressures and temperatures that prevail, all ...

4

If I understand correctly, you are asking if a meteor impact could (i) slow the Earth's rotation on its axis or revolution around the Sun enough to account for the 8 to 12-fold decrease in longevity of human-kind measured in Earth days/years; and (ii) cause 40 days of torrential rain, resulting in sufficient inland flooding to float a large wooden boat. An ...

1

Slight radioactivity inside the earth continues to produce heat - and given the size of the earth, this heat cannot easily get out. As a result, the deeper parts of the earth are very, very hot (think volcanoes) - and most phase diagrams will tell you that at sufficiently high temperatures, most things are liquid. Entropy favors it.

9

The Earth has a liquid outer core, a solid mantle exterior to that, and a solid core interior to it! So that’s how come the Earth has the heaviest, densest elements at its core, and how we know its outer core is a liquid layer. Like all elements, whether iron is solid, liquid, gas or “other” depends on both the pressure and temperature of the iron. Iron, ...

1

Simple answers like "pressure keeps substances in solid state" are gross simplifications. If you look at any scientific source, a phase diagram often shows $p$ and $T$ (pressure and temperature) on the axes. This is because at different temperatures but at equal pressures, substances can have different states and vice versa for different pressures and ...

1

You definitely don't need to use General Relativity to answer this question. It depends upon what you mean by "feel". If "feel" means "detectable by sophisticated instruments" then, yes, it can be "felt". But your body is not a very sophisticated detection instrument. According to what I've read elsewhere, the Earth speeds up by $1000$ $m/s$ as it moves ...

0

Earth's gravitational field causes Earth to retain a gaseous atmosphere, which both absorbs light itself and refracts light towards the surface. Estimating the altitude of the optically thick part of the atmosphere as somewhere between 6 km and 60 km, this atmosphere effectively increases the cross-sectional area of the Earth for interacting with sunlight ...

4

Even if the orbit were a perfect circle, there's some acceleration towards the sun. If there weren't acceleration then the earth would move in a straight line (instead of a circle); but it doesn't move in a straight line therefore there's acceleration. In a sense, the earth doesn't feel the acceleration because it doesn't try to resist it: if you stand on ...

4

The Earth "compells" an aircraft to rotate with it through the fluid drag of its atmosphere. So a practical answer to your question is then "above the atmosphere", which is at about a $100{\rm km}$ height. This is the von Kármán line, which is often taken as the definition of the edge of space. The definition is made because at this height, a standard ...

1

As soon as you get above the atmosphere (about 100 km off the surface of Earth, give or take), then there's nothing in particular that compels you to follow the Earth's rotation. Of course, once you get there, you will probably already be moving to some degree, depending on which mechanism you use to get yourself up. If you do, however, you can bring along ...

0

It doesn't depend on the height. Now you are on the rotating Earth, so you rotate with it (around the axe of Earth's rotation). Its speed is between 0 (on the poles) and around 1.5 Mach on the Equator (1 Mach = the sound of speed). If you want to compensate this rotation, there are many ways, for example, you can simply sit on an airplane capable to go ...

0

If you were at the equator, your ground speed, due to the rotation of the Earth, is around 460 m/s (1 000 mph) so you are really moving. Now say you jump into the air and somehow you delay your fall by 10 secs. Will the earth have rotated a bit under you? No, because you have the same horizontal speed as you had on the ground. This is why rockets are ...

4

Do radio waves from the Sun reach Earth? Of course they do. It's just another form of electromagnetic radiation. If so, do they penetrate the atmosphere or are they reflected, absorbed, or scattered? That depends on frequency (or wavelength). The atmosphere reflects, absorbs, or scatters most incoming electromagnetic radiation. There's a window in ...

1

Offhand I'm not sure where to find information about how much is absorbed, reflected and scattered, but the waves certainly do reach Earth, and some, at least, penetrate the atmosphere and end up in solar radio observatory detectors, otherwise we wouldn't have so many of them.

-3

My answer is more metaphysics than physics. The reason we do not "feel" the acceleration is that the change is within the tolerances of our bodies. That said, I am sure there have been people born who are more attuned to these forces. But for the most part, for most of use, there are so many forces acting on our senses that the acceleration of the earth is ...

49

John Rennie's answer is right from the viewpoint of General Relativity -- but since the question is tagged with Newtonian mechanics, it deserves a Newtonian answer too. In the Newtonian framework, I think the best answer to "why don't we experience this force" is that we can't feel forces that apply to our body at all. What we actually experience with our ...

4

John Rennie has answered the question in terms on general relativity, but it can also be answered with Newtonian physics. Your question is very similar to this one: Why does the moon stay with the Earth? and I can refer you to my answer there. In short, the Sun isn't only pulling on the Earth itself, it's pulling on everything on it as well, including us, ...

12

According to the Equivalence Principle a free falling system cannot locally detect a gravitational field. However Earth is a large enough system such that non-local effects turn out to be appreciable. Solar tides are - although small - detectable. So in principle one can experience the Sun's gravitational field even though we are in free fall. What I claim ...

61

We don't feel any acceleration because the Earth and all of us humans on it is in free fall around the Sun. We don't feel the centripetal acceleration any more than the astronauts on the ISS feel the acceleration of the ISS towards the Earth. This happens because of the way general relativity describes motion in gravitational field. The motion of a freely ...

0

A curious result of the physics involved is that the dropped mass oscillating up and down through the hole (say from North Pole to South Pole and back) would be matched exactly by a mass in a polar circular orbit at ground level. Note that the max velocity in the answer above is the same as the circular orbital velocity. If the object were dropped at ...

3

This is a surprisingly simple thing to calculate. It is a well known result that a consequence of the inverse square law is that there is no force inside a symmetrical hollow shell. This means that as the object falls into the hole, it will appear to be attracted by a sphere of decreasing radius - the mass outside "doesn't count." The acceleration of ...

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