56 votes
Accepted

Farthest point from the center of the Earth

It's Chimborazo, Ecuador, but only just, beating Huascarán, Peru, by less than 50 metres. Both are over 2 km 'higher' than Everest. I made a plot of some mountains — height above centre of the earth ...
  • 10.8k
56 votes

Why is the pond in my backyard not frozen when it is -15 °C (5 °F) outside?

Water is a rather strange substance. With most substances, the solid phase is denser than is the liquid phase. This is not the case with water. Ice is less dense than liquid water. A side effect of ...
  • 20.7k
55 votes
Accepted

Does gravity increase the closer to the core you get?

The below figure, taken from Wikipedia shows a model of the free fall acceleration, i.e., 'gravity'. The left-most point corresponds to the center of the Earth; then further right at $6.3\cdot1000$ km ...
  • 1,969
53 votes
Accepted

Why is the pond in my backyard not frozen when it is -15 °C (5 °F) outside?

Water melts at 0 °C (32 °F) but freezing is a more complicated affair. It is safe to say water gains the ability to freeze at 0 °C, but it can get much cooler before it actually does so resulting in ...
  • 14k
42 votes
Accepted

Where on Earth is the magnetic field intensity stronger?

If we consider only the magnetic field generated by natural sources, and not the ones generated by human activities. The general trend is that higher intensities of the magnetic field happen close to ...
  • 17.1k
30 votes

What are these undersea lines all around Hawaii?

Short answer: The lines radiating from the island are artifacts from a mapping process that superimposes high-resolution sonar data from standard ship tracks on top of r low- or average sonar data ...
  • 3,144
28 votes
Accepted

Where is the calmest place on Earth?

The main resistance that winds have to their movements comes from the topography and surface obstacles. Therefore, as a general rule the closer to the surface the less wind you will find. But I guess ...
  • 17.1k
26 votes
Accepted

Is it true that earthquakes are not felt in a cave?

Ground motion results due to passage of elastic waves. Now there are different kinds of waves, e.g., P waves, S waves, surface waves, etc. Most of the shaking (and therefore damage) is caused by ...
  • 2,361
23 votes

Farthest point from the center of the Earth

Mount Chimborazo, which is 6,268 meters above sea level and within 1.5 degrees of the equator. More specifically, according to Dr. Milbert, Chief Geodesist, NOAA, National Geodetic Survey and Dr. ...
  • 5,912
23 votes

What would be the first thing which will render the Earth uninhabitable?

I'll try to put time scales on each of these events. The Sun as a red giant - 5 to 6 billion years$^1$ The Sun is currently on the main sequence, which means that it's a "full grown" star - think of ...
23 votes
Accepted

Why does sea level correspond to boundary between oceanic and continental crust?

Sea-level only sort-of corresponds to the oceanic–continental crust boundary. In depth, they don't correspond at all: It's the same story at an active margin: the plate boundary at a subduction zone ...
  • 10.8k
22 votes

Why is the pond in my backyard not frozen when it is -15 °C (5 °F) outside?

Due to convection (the cold water sinks while the warm water rises), the entire pond needs to be brought to near-freezing temperatures before the surface can freeze. With only the top of the pond in ...
22 votes
Accepted

Does gravity differ from place to place on Earth

There is an entire field of Geophysics called gravimetry dedicated to measuring the magnitude of the gravitational field. First, we should distinguish between weight (a force) and gravity (an ...
  • 14.8k
22 votes
Accepted

Taking into account the decay products of transuranic elements, are the world's uranium reserves growing or shrinking?

Let's start with the easy question: given our current known reserves of transuranic elements and again taking into account their decay products, where will the greatest uranium reserves be in, say, ...
  • 22.3k
21 votes
Accepted

How long until Earth's core solidifies?

Global warming has to do with the surface only, and at best involves changes of 20 degrees at the outside extreme, in comparison to the earth's core, which is as hot as the surface of the sun. For ...
19 votes
Accepted

Can ultrasounds be used to map the density of large underground regions?

Sound-like waves are routinely used to image the subsurface, but mostly well below the ultra-sound band. Several methods involve sound-like vibrations: Reflection seismic — the most important ...
  • 10.8k
18 votes
Accepted

Change in earth mass since the time of the dinosaurs

I gather, but may be wrong, that the mass of earth at present increases by around 108kg/day. All else being equal, one would expect the earth to have gained a mass, since 75 million years ago, of: $$ ...
  • 20.7k
18 votes
Accepted

How to quickly or easily prove the world is spherical?

To answer my own question based on the useful comments here, my favorite methods were: The earth's shadow cast on the moon during an eclipse. It is easy to observe and the flat earth counter argument ...
  • 361
18 votes

How to quickly or easily prove the world is spherical?

I'm sorry that this answer will be unsatisfactory and, strictly spoken, off topic, but I want to give it anyway. The answer is: You can't. Don't waste your time. Your relative has developed a ...
17 votes
Accepted

Can the overuse of geothermal energy become an environmental concern?

No, this seems highly unlikely. According to online sources: Average human power consumption in 2008 was estimated at 15 TW. Total annual heat loss from the Earth due to the surface heat flux is ...
  • 3,780
17 votes
Accepted

What are the non-anthropogenic causes of The Netherlands' low elevation?

Forming of coastline During the last ice age, the North Sea was dry. When the ice melted sea levels slowly started to rise again and due to tides and currents a barrier of dunes was formed along what ...
  • 420
17 votes

Is it true that earthquakes are not felt in a cave?

There are three main types of waves produced during an earthquake: P, S, and L waves, which stands for Primary, Secondary, and Love. (There was a mnemonic I read many years ago that went P=pressure, S=...
  • 2,137
17 votes
Accepted

How bad is geo-engineering?

The bad part about geo-engineering are the unknown unknowns, to paraphrase a certain US politician. Our climate models are wrong. All models are wrong, but some are useful.. Our models are useful, ...
  • 11.2k
17 votes

Why is the temperature between the earth core and surface not distributed linearly?

The temperature does indeed increase with depth, something that is a problem in deep mines or deep drilling, but a benefit for geotermal heating. The heat originates mostly from radioactive decay, but ...
  • 5,906
17 votes
Accepted

How did the Ural mountains form?

The Ural mountains are one of the oldest mountain ranges on Earth. They started forming about 300 Ma ago by the subduction of the oceanic crust once attached to the Kazakhstania plate under the ...
  • 17.1k
16 votes
Accepted

Why won't Yellowstone explode?

This is a complex question, and I cannot give you a complete answer I'd like to point out that there is a very important article published in February of this year on the subject: volcanoes are in an ...
  • 6,386
15 votes

Why does New Zealand and cold countries have volcanoes?

Surface temperatures on Earth are a consequence of solar heating and radiative cooling - in other words, the heat energy which drives climate comes from sunlight falling on the Earth "now". On the ...
  • 439
15 votes

Is it true that earthquakes are not felt in a cave?

Googling leads to a very old document: EFFECTS OF AN EARTHQUAKE IN A MINE AT TOMBSTONE, ARIZONA stating that in many cases, mine workers did not notice earthquakes which were felt above ground. A ...
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15 votes

Why is the pond in my backyard not frozen when it is -15 °C (5 °F) outside?

The water in a pond is in contact with the ground and the ground is not even close to freezing even if the air temperature is 27° below freezing.
  • 2,137

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