Earth is the planet on which we live. 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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Why a day is divided by 12/24 hours? Why the number 12?

Why a day is divided by 12/24 hours? Why the number 12? Why not using 10 or 6 or 14, 16? Who invented this? Any physical reasons behind this?
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2answers
2k views

How far into space does one have to travel to see the entire face of earth?

Virgin Galactic will take passengers aboard SpaceShipTwo as high as 65 miles above the surface of the earth. But from this altitude, passengers will only be able to see a certain segment of the ...
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1answer
210 views

Measuring temperature at a distance

http://www.youtube.com/watch?v=gKYrXHZwtPw In this video it is explained that Land Skin Temperature (LST) are measured by NASA's Aqua and Terra satellites. It seems it works by collecting the ...
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2answers
229 views

Is it possible to use a balloon to float so high in the atmosphere that you can be gravitationally pulled towards a satellite?

A recent joke on the comedy panel show 8 out of 10 cats prompted this question. I'm pretty sure the answer's no, but hopefully someone can surprise me. If you put a person in a balloon, such that ...
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4answers
2k views

Does the moon affect the Earth's climate?

So, this morning I was talking to a friend about astronomical observations, and he told me that lately there has only been good weather when there was a full moon in the sky, which was a shame. I ...
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4answers
94 views

Bulk flow of air in a long tube between Antarctica and Australia?

I have a 5km diameter clear plastic tube which is open at each end and runs from the center of Antarctica to Lake Eyre in Australia. The tube is on the ground where it can be and at sea level on the ...
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2answers
232 views

Will I get a shock when I try to use my hair-dryer under water?

Occasionally people get killed in their bathtubs by having an electrical device such as a hair-dryer take the bath with them - in movies. It seems to be a common belief that this is realistic, even ...
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1answer
173 views

Axial Tilt and precession rate of exoplanets

The Earth's axis is 23.5 degrees away from othogonality to the ecliptic, and it takes about 26 000 years for it to precess fully. I have neither an intuitive sense nor the formula for precession ...
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4answers
780 views

Why doesn't the Earth leave you as soon as you escape it?

I've always wondered, that since the Earth is moving at a very fast velocity around the Sun, why is it that when astronauts leave the Earth, the Earth doesn't immediately move away from them at ...
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5answers
1k views

Video of Earth spinning?

If the Earth is spinning or rotating at a really fast speed, why haven't we seen any videos from space of it spinning when we get a lot of photos of it?
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2answers
2k views

how far away can something be from the earth and still be in orbit?

Just as the title asks, How far away can, say, a satellite be and still be in "orbit" ? How about for a given velocity? Fun Facts 200 miles (320 km) up is about the minimum to avoid atmospheric ...
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2answers
2k views

What does the phrase “limb of the earth” or “atmospheric limb” mean?

What does the term limb of the earth (see this question, for example) or atmospheric limb mean? The phrase strikes me as very odd, since earth is nearly spherical. Do other planets with atmospheres ...
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3answers
484 views

Does the conversion of crude oil to greenhouse gases have any measurable effect on earth's gravitational pull?

Oil underground is much denser than greenhouse gas in the atmosphere. Does the conversion in anyway effect the gravitational force from earth.
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3answers
5k views

Can the Earth's magnetic be used to generate electricity?

Since the Earth has a magnetic field, can it, in theory, be run through a conductive metal coil to create electricity?
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1answer
537 views

If the Moon had gravity as good as the Earth and a magnetic field could it have supported life?

If the Moon had gravity as good as Earth and a magnetic field could it have supported life? Because if the Moon had gravity, it could have retained water more than is present today on the surface. ...
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3answers
2k views

If there was a black hole on earth, what would it look like?

If an answer does exist, I'd love to hear it. I'm trying to incorporate a doomed earth story in something I'm writing, and the end of the world I'm going for is a black hole. Let's say the black hole ...
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2answers
235 views

Proofs that Earth is not flat? [duplicate]

Well, I do not believe that Earth is flat, but I met some conspirationistas believing that all physics we learn in school is twisted, all the Earth's pictures from space are photoshopped by NASA, etc, ...
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2answers
89 views

Does the Earth's core have tides?

Does the moon produce a measurable tidal-effect on the Earth's (liquid) core? If so, how strong is it? Would it play a factor in other geological effects like earthquakes, volcanoes, etc?
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1answer
1k views

Why does the sun “shine brighter” some days?

Today, the sun seems extremely bright; more dazzling than usual, and even the roads seem to be brighter so it's not just when you look up in the sky. Is more light actually getting through (perhaps ...
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3answers
461 views

Gravitational force of the Earth [duplicate]

Why does gravitational force of the Earth decrease as we move towards the centre of the Earth? Where as inverse square rule says that distance is less than gravitational force is more.
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2answers
399 views

Effect on length of day as the polar ice caps melt

If the polar ice caps of the earth melt, how will the length of the day be affected?
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2answers
102 views

If Earth was the size of an orange, what consistency would it be? [closed]

I understand that the Earth is composed of a thin crust "floating" over a semi-solid layer of mantle. I was wondering how it would feel at a human scale, say the size of an orange in your hand. Could ...
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1answer
126 views

How long did the first rainshowers on Earth last?

When I was a child, I read many times over with fascination about the formation of the Earth in a large illustrated encyclopedia of sorts for adults (one of at least two volumes, though I will ...
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2answers
284 views

Why does earth's magnetic field change its direction?

I know that the earth's magnetic field is due to molten metal and ions flowing in its core. It has been found that the Earth's magnetic field changes its direction and it has even flipped once! But, ...
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1answer
647 views

How much negative charge do I accumulate by touching the earth?

The Earth carries a negative electric charge of roughly 500 thousand Coulombs (according to different sources I've seen). If I touch the Earth I should therefore pick up some of this electric charge ...
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5answers
261 views

Would dropping large blocks of ice into the ocean mitigate global warming?

This amusing Futurama sketch 'solves' global warming by dropping increasingly larger blocks of ice into the ocean. Presumably the blocks of ice are harvested from a different planet. Would this ...
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1answer
694 views

Does the Earth rotate vertically too?

We know that the earth has seen several Ice Ages. And we know the Earth's magnetic poles seem to flip once in a while. Could all of this be explained by a once every 250 Million Years or so the ...
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2answers
715 views

Cancel out Earth's Magnetic field

Is there any tools except helmholtz coil to cancel out earth's magnetic field to calibrate magnetometers in practice.
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2answers
610 views

How is the Earth heated by a Full Moon?

While the moon is certainly not a good reflector of solar radiation, surely the radiation it reflects back heats the Earth (even if it is a terribly small amount). How would one go about calculating ...
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1answer
954 views

What if the earth's core goes cold?

What effects would occur if the earth's core goes cold? Would the planet stay liveable after this happens?
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1answer
795 views

Formula for getting time of sunrise at a particular location?

Is there a formula that can get sunrise at a particular latitude and longitude (and elevation from sea level)? If so, what it is? (Why does it work?)
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1answer
113 views

Could moving land mass alter Earths gravity?

This is potentially a very stupid question but I'm going to ask it anyway. With all these huge buildings such as the Abu Dhabi Mosque, where an unbelievable amount of materials such as marble was ...
4
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1answer
123 views

Effect of Earth's magnetic field on aeroplanes?

As an aeroplane accelerates through the Earth's B-field, it experiences a changing flux $d\phi \over dt$ and a potential difference is induced along its wings. Given the wings are made of metal and ...
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2answers
216 views

Why aren't solar panels efficient?

Why can't solar panels produce 1 Kw per 1 square meter? This is the energy of the Sun's radiation per square meter on Earth but solar panels don't come close. Why can't we trap all that energy? ...
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1answer
33 views

What weathering mechanism leads to reduction of Carbon Dioxide in the atmosphere?

Wikipedia says: The global temperature of the Earth will climb because of the rising luminosity of the Sun, the rate of weathering of silicate minerals will increase. This in turn will decrease ...
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2answers
137 views

Assuming that the Sun wouldn't evolve into a red giant, how long would the Earth's atmosphere last?

It's not going to last forever - Jeans Escape is going to eventually act on the atmosphere after trillions of trillions of years: see http://faculty.washington.edu/dcatling/Catling2009_SciAm.pdf
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2answers
250 views

Attenuation mass-thickness for sunset light

We are able to look directly at the sun near sunset and sunrise, which clearly demonstrates the fact that our atmosphere attenuates visible light. Let's imagine it follows the typical attenuation ...
4
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1answer
126 views

Link between Earth and Mars

I am trying to the calculate the link budget for link between a ground station on Earth (with a particular latitude and longitude) and a rover at a particular location on the surface of Mars, either ...
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2answers
109 views

Antipodes are mostly ocean - so what happens after digging that hole through earth?

Digging a hole through earth is a common thought experiment, often used to explain effects of gravity. But what would happen if someone finally dug the hole? Sure, he took care to stabilize and ...
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4answers
143 views

Why is earth on an axial tilt of 23.4 degrees?

What were the influences for this to occur? Did some things play a bigger part that others?
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1answer
189 views

What do you call the period after sunrise when the sky is bright?

At sunrise, the sky isn't actually up in the sky yet. Twilight occurs before sunrise, then at sunrise the leading part of the sun crosses the horizon. But, the sky isn't bright yet. It takes some time ...
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1answer
328 views

How would gravity change on a planet rotating around itself very fast?

Let's take a planet identical to Earth, but with rotation speed multiplied by ten thousand. What would happen with the gravity if it was spinning madly around itself? Would the centrifugal force make ...
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2answers
382 views

Deviation from Earth's orbit

How much orbital deviation is required for the Earth to get knocked out from current orbit so it either moves away from Sun or towards the Sun?
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2answers
1k views

What would the effect be of a small black hole colliding with the earth?

If a small black hole (say about .1 mm radius or 1% of Earth's mass) came flying along at the speed of a comet or higher and impacted the earth, what would happen? Would it pass through the earth (and ...
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4answers
877 views

Angular momentum power plant on Earth

If tidal power plants are slowing down Earth's rotation then is it theoretically possible to build a power plant that would drain energy from Earth's angular momentum (thus slowing down it's ...
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6answers
4k views

Where on Earth can you find plasma?

Ok, so not that 'where on earth', like literally - 'Where on Earth'. Where on Earth, can you find matter in the 4th state, i.e. the plasma state?
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3answers
264 views

How would normal matter behave under conditions found in the core of the sun?

Considering how low the power density is at the sun's core, I seem not to be able to expect what would happen to matter in case it was thrown inside the sun's core. For example, let's assume an ...
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1answer
2k views

How much energy would it take to blow up the earth?

There is a common statement running around that we as a species has enough nuclear weapons to blow up the earth several times over. What I want to know is: by how many orders of magnitude is that a ...
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3answers
322 views

Would a sea level rise (on the other side of the Earth) if you would dip your finger into the ocean?

(I'm not a physicist & I hope this question isn't too basic/lame) The question says it all & assuming: No atmosphere No Earth rotation Not a single object in the ocean(s) Ignore all other ...
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1answer
166 views

Under what practical conditions would Earth's atmosphere be a dilatant?

I have read and heard in many places that when the astronauts of Apollo were coming back to Earth, they had to determine the best angle of attack to re-enter the atmosphere. This is usually indicated ...