52

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 you are at the Earth's surface; and then further out you move into space. You can follow the blue line for PREM to get an idea of the average (expected) ...


32

Depends on your eye. You can realise the curvature of the Earth by just going to the beach. Last summer I was on a scientific cruise in the Mediterranean. I took two pictures of a distant boat, within an interval of a few seconds: one from the lowest deck of the ship (left image), the other one from our highest observation platform (about 16 m higher; ...


21

This is a companion to the other answer. The other answer gives values for what the acceleration actually is based on knowledge about the composition of the planet. In this answer I want to introduce some of the mathematical tools that allow you to reason about how gravity varies in and around planets. David Hammen's answer, which I think he wrote ...


18

A quick Google turned up a published article answering precisely this question (Lynch, 2008). The abstract states: Reports and photographs claiming that visual observers can detect the curvature of the Earth from high mountains or high-flying commercial aircraft are investigated. Visual daytime observations show that the minimum altitude at which ...


17

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 is so insane that if it is offered you should just walk away. Shadows differ from place to place. The same experiment as Eratosthenes but you can carry this ...


17

the horizon is a circle centered at the viewer's position There are two things wrong with this. The first is the assumption that the Earth is entirely spherical - there are no hills, mountains or other bulges to block the view. But let's make that assumption, because there's a more fundemental misunderstanding in the geometry. The horizon is a circle that ...


16

The sun is really far away. Thus its rays are essentially parallel at the earth's orbit. So, while the diagram you posted is clearly a bit off in terms of the relative size and distance between the sun and the earth, the parallel rays are about right.


16

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 paranoia. Not only is this not an isolated earth science issue; it is not even an issue with science at all. Instead, she has dismissed our common everyday frame of ...


15

It's hard to see the curvature of the earth from an altitude of 7 miles or 37,000 ft (typical cruising altitude of a jetliner) but easy to see from 250 miles (typical altitude of the ISS). The line of sight from an aircraft at 37,000 feet = 235 miles. That's only about 3.4 degrees of the earth's surface. From the ISS at 250 miles, the line of sight is 1,...


14

CERN is a scientific site developed to create anti matter The scientific activity at CERN involves many things, anti matter being just one of them. For more information you can read their anti matter page. Does this have any negative impact on the environment? No. The amount of anti matter is negligible. Any anti matter produced in CERN is also ...


11

The sun is about 100 times the size of the Earth (in diameter), and the distance from the sun to Earth is about 100 times the diameter of the sun. Below is an image showing the sun, Earth, and the distance between them to scale. It looks at first like nothing more than a black bar. This image in the original is 4000 pixels (the limit of my Pixlr Editor) by ...


10

[I am going to preface this by saying that I am not in one camp or the other in this discussion, as I think there are pros and cons to each side] This links to the "Gaia Theory" proposed by James Lovelock, wherein the Earth is considered a self regulating organism. In this hypothesis, Earth is an organism in that it will try to maintain certain conditions....


10

In addition to @Michael's excellent answer, keep in mind that fields from charges drop off with the inverse of the distance squared and from dipoles (like those of the Earth and a lot of CERN's larger experiments) with inverse distance cubed. Take for example the magnet used in the LHCb experiment at CERN. It is a large dipole magnet with a maximum field ...


10

Your question is simple enough, but the answer depends on what exactly you're looking for. Who is emitting where right now? Real-time global monitoring of greenhouse gas emissions with a high spatial resolution is an emerging technology. We have very useful satellites (see Jean-Marie Privals answer), but they have limitations: All existing public ...


9

From a list & map of known seamounts and submarine volcanoes it is unlikely the orange region in your picture is a submarine volcano. The average depth of the Pacific Ocean is 4280 m. At such a depth, a submarine volcanic eruption would not produce such a large area of illumination. It is more likely that the orange region in your picture is sunglint, ...


9

Those are Sun/Moon multispectral photometers and ski radiometers. These are instruments that can scan the sky or track the Sun/Moon for direct measurements. They measure light intensity at multiple narrow wavelength bands, and are designed to measure atmospheric aerosols content and characteristics. The ones in the third image seem to be a CIMEL CE-138 Sun ...


9

I can imagine a satellite observation-based model that calculates emissions on a spatial basis but I am not sure if our technology is advanced enough to do that accurately. It is. The first satellite designed to measure GHG is GOSAT, from the Japanese space agency, launched in 2009 and still active today. It was followed by Nasa's OCO-2 in 2014. GOSAT ...


9

Given the weather patterns, it looks like Google Earth is generating those cloud overlays from some recent (i.e., the current day) satellite images. That line is suspiciously close to the edge of disc line for Meteosat 8, which is located over the equator at 41.5 °E. I suspect that it's just an artefact of how they're stitching together the various images ...


8

The biggest flaw I see in a cursory look at this work is failure to compensate for atmospheric refraction. Density varies in the atmosphere enough that the refractive index varies. At low angles above the horizon the temperature structure of the atmosphere becomes very important in determining optical refraction and at low angles very close to the ground ...


8

In theory, if the Earth was a solid object, the Chandler wobble would be easy to understand. It's simply a result of the polhode rolling without slipping on the herpolhode lying in the invariable plane. In other words, $\mathrm I \dot \omega + \omega \times (\mathrm I \omega) = 0$, where $\mathrm I$ is the Earth's inertia tensor and $\omega$ is the Earth's ...


8

Skype. Skype someone at least 10 time zones away. Ask them to point the camera at the sky. Proven. This actually works really well for a psychological reason as well. Its easy to deny abstract arguments, its difficult talking to someone and denying what they claim is their experience.


8

The latitudes today are 66°33′46.1″ N and S, the Arctic and Antarctic Circles. By definition, north of the Arctic circle, and south of the Antarctic circle, everywhere gets at least one day with no sunset, which I guess is what you mean by 'exactly 24 hours of daylight'? From the linked article: North of the Arctic Circle, the sun is above the horizon ...


7

But if you scale up the Sun to it's real size compared to the Earth, Is pretty big. But then to be realistic in that manner you would also have to scale up the distance from the earth to the sun. But you don't have to even do that, as there is a much simpler way of seeing how large the sun is from the perspective of a position on the earth. Be on or very ...


7

A cold front lies in a trough of low pressure and separates air masses. As you mention in your question there are differences in temperature and the winds on either side of the front, though these can be subtle depending on latitude and season. A "classic" (mid-latitude NH) cold frontal passage might be recorded as southerly or southwesterly winds, ...


7

This stack exchange is about Earth Science. The scientific position is unequivocal in verifying the reality of climate change. One is free to take a contrary skeptical position, but it isn't supported by climate data, ecological data, glaciology, atmospheric and oceanographic science, modelling, theoretical studies, feedback mechanisms, peer review scrutiny,...


7

Make your own numbers... I will take one sample, just change your figures. I have one 4K resolution dron camera. So I can register 3840 x 2160 pixels in one shot. Considering the Earth as an spherical body, the distance from you to the horizon depends on Earth Radius and your height by: Distance = (Radius + height) * Sinus {arc-cosinus [Radius / (Radius ...


6

Further to DrGC's excellent answer, a subjective assessment of visibility of the Earth's curvature can be gleaned from pilot's experioence over many decades. These can be summarized as: Commercial aircraft normal maximum ceiling of 13.7 kilometres : The curvature isn't apparent. Concorde's ceiling was 18.3 kilometres, and reports are inconsistent. Some ...


6

Given the known average distance to the Sun, and the radii of Sun and Earth, the basic trigonometry is simple. If the Earth and Sun were exactly the same size, and there was no atmospheric refraction, then exactly half the planet, or 180 degrees, would be illuminated. But since the Sun is so much bigger, again assuming no atmospheric refraction, then ...


6

The simplest method I can think of is to observe a hand-held global positioning system ('GPS'), which shows the position of visible satellites, directly overhead, and at various angles from the vertical. Once satellites disappear over the horizon, they reappear again exactly in accordance with an orbital trajectory around a sphere. Secondly, go to Google ...


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