Questions tagged [earth]

Earth is the planet on which we live, the 3rd planet from the Sun. Questions using this tag should be about Earth the planet and not Earth-like planets nor earth, as in dirt or soil.

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154
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15answers
56k views

How do I explain to a six year old why people on the other side of the Earth don't fall off? [closed]

Today a friend's six year old sister asked me the question "why don't people on the other side of the earth fall off?". I tried to explain that the Earth is a huge sphere and there's a special force ...
153
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26answers
22k views

Simple check for the global shape of the Earth

I have been on a date recently, and everything went fine until the moment the girl has told me that the Earth is flat. After realizing she was not trolling me, and trying to provide her with a couple ...
75
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9answers
193k views

Why doesn't the Moon fall onto the Earth?

Why doesn't the Moon fall onto the Earth? For that matter, why doesn't anything rotating a larger body ever fall onto the larger body?
62
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17answers
128k views

What is the simplest way to prove the Earth is round?

Assume you've come in contact with a tribe of people cut off from the rest of the world, or you've gone back in time several thousand years, or (more likely) you've got a numbskull cousin. How would ...
60
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6answers
35k views

Why has Earth's core not become solid?

The Earth is billions of years old, yet its core has not yet cooled down and become solid. Will this happen in the foreseeable future?
55
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8answers
12k views

Is it possible to send all nuclear waste on Earth to the Sun?

If we neglect the danger of unsuccessful lift-off of the rocket and the cost, would it be physically possible to send all nuclear waste on Earth to the Sun? Will there be an obstacle that prevents ...
54
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8answers
38k views

Proof that the Earth rotates?

What is the proof, without leaving the Earth, and involving only basic physics, that the earth rotates around its axis? By basic physics I mean the physics that the early physicists must've used to ...
52
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4answers
132k views

How does gravity work underground?

Would the effect of gravity on me change if I were to dig a very deep hole and stand in it? If so, how would it change? Am I more likely to be pulled downwards, or pulled towards the edges of the hole?...
51
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2answers
8k views

Was the 2013 meteor over Russia stronger than an atomic bomb?

Reports of the Russian meteor event (2013) say that it released more energy than 20 atomic bombs of the size dropped on Hiroshima, Japan: Scientists estimated the meteor unleashed a force 20 times ...
47
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9answers
19k views

Why is air not sucked off the Earth?

People said outside earth is a vacuum. But the air does not get sucked from the Earth's surface. Some said it is due to gravity and some said the speed of air molecules are not high enough to escape....
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10answers
10k views

Why can't the Earth's core melt the whole planet?

Earth core temperature is range between 4,400° Celsius (7,952° Fahrenheit) to about 6,000° Celsius (10,800° Fahrenheit). Source Why can't the Earth's core melt the whole planet? In other words, what ...
41
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4answers
25k views

Why is a new moon not the same as a solar eclipse?

Forgive the elementary nature of this question: Because a new moon occurs when the moon is positioned between the earth and sun, doesn't this also mean that somewhere on the Earth, a solar eclipse (...
40
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7answers
8k views

Why does the full Moon appear?

I know that the full Moon appears when Sun, Moon and Earth are in a straight line, but if we consider that they are in straight line, why is the Moon illuminated? I mean to say that Earth should ...
40
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3answers
8k views

Why wouldn't the part of the Earth facing the Sun a half year before be facing away from it now at noon?

The Earth takes 24 hours to spin around its own axis and 365 days to spin around the Sun. So in approximately half a year the Earth will have spun around its axis 182.5 times. Now take a look at the ...
40
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6answers
8k views

How can the Earth keep spinning with a liquid core?

In regards to the 'conservation of angular momentum' being the explanation of why celestial objects spin... If you fill a ball or any other container with a liquid and try to spin it, you will not ...
40
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5answers
32k views

Would you be weightless at the center of the Earth?

If you could travel to the center of the Earth (or any planet), would you be weightless there?
39
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5answers
27k views

If the Earth is a good conductor of electricity, why don't people get electrocuted every time they touch the Earth?

Since the Earth is a good conductor of electricity, is it safe to assume that any charge that flows down to the Earth must be redistributed into the Earth in and along all directions? Does this also ...
39
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8answers
70k views

If the gravity at the center of the Earth is zero, why are heavy elements like iron there?

If gravity is zero at the center of the earth, why is there a core of heavy elements, such as iron? Alternate question for the opposite hypothesis: If gravity is greatest at the center of the earth,...
38
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7answers
10k views

Why don't we feel the subtle speed change of Earth's elliptical orbit?

Earth's orbit is a slight ellipse, so to conserve momentum its speed increases when it is closest to the Sun. If the speed changes there is an acceleration. If there is an acceleration there is a ...
38
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8answers
15k views

Would it matter if the Earth rotated clockwise?

In the Futurama episode "That Darn Katz!" they save the world by rotating the Earth backwards saying it shouldn't matter (which direction Earth rotates). If Earth rotated clockwise and remained in it'...
37
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4answers
6k views

Why is Earth's climate so stable?

Earth wasn't always the only water-world in the solar system. Mars also appear to have started out wet but, as conditions changed, Mars lost its oceans. So, how has Earth managed to avoid a similar ...
37
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7answers
6k views

How fast a (relatively) small black hole will consume the Earth?

This question appeared quite a time ago and was inspired, of course, by all the fuss around "LHC will destroy the Earth". Consider a small black hole, that is somehow got inside the Earth. Under "...
36
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6answers
11k views

If the moon had a mirror surface, would the earth be equally illuminated as by the sun during full moon, or would it require a different mirror shape?

Suppose the apparent diameters of the sun and the moon are exactly the same (which in fact very close to the real situation). If the moon had a perfect mirror surface, would the reflected visible ...
36
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5answers
19k views

Why can't we feel the Earth turning?

The Earth turns with a very high velocity, around its own axis and around the Sun. So why can't we feel that it's turning, but we can still feel earthquake.
35
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12answers
11k views

If a jet engine is bolted to the equator, does the Earth speed up?

If a jet engine is bolted to the equator near ground level and run with the exhaust pointing west, does the earth speed up, albeit imperceptibly? Or does the Earth's atmosphere absorb the energy of ...
35
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3answers
13k views

Why does the Earth cool at night time?

I do understand that open water and open ground cools by the means of convection — lower air takes the heat and goes up, where it cools. But why does the Earth lose energy and where does it go? Does ...
35
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2answers
20k views

What is the net charge of the Earth?

This question arose in a seminar today about the solar wind... This is my vagueish understanding of the problem - please correct if you see errors! The 'classical' picture of atmospheric electricity ...
28
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2answers
2k views

Why doesn't Earth's atmosphere form bands due to different rotational speeds?

If the Earth's atmosphere is rotating at the same speed as Earth, then the atmosphere must be rotating much faster at the equator than at the poles. If you spin a ball covered in oil, it will form ...
27
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5answers
10k views

Build a ring around Earth, then remove the supports

What would happen if we decided to build a giant ring that managed to wrap around the whole world, end to end that was supported with pillars all along the ring and then the supports all suddenly ...
27
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2answers
10k views

How long until we fall into the Sun?

As a planet moves through the solar system, a bow shock is formed as the solar wind is decelerated by the magnetic field of the planet. Presumably the creation of this shock wave would cause drag on ...
26
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2answers
7k views

How much additional mass does the Earth gain each day from solar radiation?

According to this answer, energy has some (minimal) mass associated with it. Therefore, when lots of energy hits the earth (such as solar radiation in a 24 hour period) shouldn't the earth gain some ...
25
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2answers
4k views

How fast is the Earth-Sun distance changing

This is inspired by Evidence that the Solar System is expanding like the Universe?, which referenced an article by G. A. Krasinsky and V. A. Brumberg, "Secular Increase of Astronomical Unit from ...
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4answers
1k views

What would happen if somebody dropped a small black hole into the Earth?

Suppose we drop a small black hole, but large enough that it accumulates mass more quickly than it radiates it, into the Earth. What happens? This question has already been asked here and here, but ...
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11answers
11k views

Backyard experiments to falsify the Flat Earth theory [duplicate]

I recently became aware that the flat Earth theory still exists in the 21st century, and has colored the views of a friend of mine. Roughly speaking, the tenets are: The Earth is a flat disk, with ...
23
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5answers
20k views

Can helium disappear from Earth?

Helium is lighter than air, so it should fly off from Earth. Is it possible that in the future we will run out helium?
22
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2answers
6k views

What is the scientific explanation for radio waves bending around the Earth?

The experiment This experiment is documented in a documentary called Convex Earth. The exact location the following information is taken from starts at 14:25. High frequency directional antennas are ...
22
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4answers
5k views

Why is the South Pole Telescope located exactly at the South Pole?

I read that there is less atmospheric interference for the telescope at the South Pole because the atmosphere is thin and there is less water vapor in the air. However this seems to be true for many ...
21
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7answers
4k views

Finding how much time it takes for a complete Earth revolution around the Sun

Long story short, my brother made a joke about how stupid it is to celebrate the Earth making one "trip" around the Sun: New Year's Eve. So I got curious and was wondering: how could the first ...
21
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3answers
9k views

How quickly was the Earth rotating 250 million years ago?

The Earth is slowing at a rate of $4.7\times10^{-4}$ miles per second every 100 years due to tidal forces of the moon. See: http://en.wikipedia.org/wiki/Earth%27s_rotation http://imagine.gsfc.nasa....
21
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3answers
1k views

Are the air particles in today's wind on earth (more or less) the same as the air 2/3 billion years ago?

So the air pressure on earth remains relatively constant, right? Is there air gained or lost through transitions of any sort? e.g. plumes going out into space, earth gaining new air particles with ...
20
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5answers
2k views

Does the Moon's core still contain significant heat?

On earth, using earth-sheltering techniques can significantly reduce the temperature fluctuations on a structure. Would the same statement be true as well on the Moon? Does the Moon's core still ...
19
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3answers
5k views

How can a full moon be seen south of an observer's location?

I know this seems like a simple question, but I'm trying to debate with a flat earth theorist. I asked him to explain why can the ISS visibly be seen orbiting the Earth with the naked eye, and he put ...
18
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7answers
13k views

Why isn’t the center of the Earth cold? [closed]

If the pressure of the Earth is keeping the inner core solid, keeping it rigid to take up the least space, and temperature is dependent on how much the atoms are moving, why isn’t the inner core cold? ...
18
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3answers
3k views

I was told that if the Moon had a retrograde orbit, tides would have a faster rhythm. Why is that?

Would this be because tidal deceleration causing the Earth to spin faster or are there other actions in play that I haven't considered? Would the Earth even spin faster because of the tidal ...
18
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5answers
121k views

Why is Earth's gravity stronger at the poles?

Many sources state that the Earth's gravity is stronger at the poles than the equator for two reasons: The centrifugal "force" cancels out the gravitational force minimally, more so at the equator ...
18
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3answers
4k views

Do mankind and manmade activities/constructions have any effect on the rotation of the Earth?

We walk or ride on our vehicles to our destinations daily. Does our movement have any effect on the rotation of the earth according to Newton's law? What will be the effect if we move all the peoples ...
17
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4answers
13k views

How can a day be exactly 24 hours long? [closed]

The longest solar day of year is approximately 24 hours 0 min 30 seconds (occurs at mid to late December) while the shortest solar day of year is approximately 23 hour 59min 38 seconds. If I average ...
17
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8answers
9k views

How do stars from far away affect Earth?

I know that we obviously get light (or we wouldn't be able to see them), but are there any other ways that they affect Earth and maybe just our solar system in general?
17
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2answers
8k views

If you hold a compass needle vertical does it point down or up differently on which hemisphere you are?

Usually our compass is hold horizontally, and in the northern hemisphere it will point in the direction of to the north of the earth (actually to the South pole of the Earth's 'magnet'). But looking ...
17
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1answer
399 views

Impact location that created the moon

I was reading an article today about the 1000th orbit of the Lunar Reconnaissance Orbiter, and as many of you know NASA created an animation that simulates the history of the moon. It is speculated ...

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