Questions tagged [earth]

Questions of the science and space exploration related to Earth.

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64
votes
9answers
14k views

Which country borders are visible from space?

You can see the borders of North Korea with China and South Korea at night from the ISS since unlike their neighbours, they have almost no light. That got me thinking, which other country borders (of ...
36
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4answers
14k views

Why is my Earth simulation slower than the reality?

It took me a long time to create a simulation of the Earth like that. I wanted to show the real spinning speed of the Earth. Here's my video: From this NASA live ...
36
votes
2answers
5k views

Was the “Earthrise” witnessed by Apollo 8 the first available “full” photo of the Earth?

Was the video/photos taken during the earth-rise on the Apollo 8 flight the first "blue marble"-esque photo? I've heard the image equated to the "earth's first selfie" and question the technical ...
33
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4answers
5k views

What is the largest piece of space debris volumetrically?

What is the largest piece of space debris currently in Earth orbit by volume? Space debris is not limited to defunct satellites, but also includes things like spent upper stages. Bonus points for ...
32
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2answers
8k views

Is it true that NASA is hiring a new 'planetary protection officer'?

NASA is hiring a new 'planetary protection officer' to defend Earth from alien matter, and the pay is a six-figure salary: as much as $187,000 a year. When we are not sure whether aliens exist, why ...
31
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3answers
6k views

Does it make any scientific sense that a comet coming to crush Earth would appear “sideways” from a telescope and on the sky (from Earth)? [closed]

In multiple different movies and fiction, there's the threat of a burning space comet heading for Earth, threatening to kill everyone and destroy the planet. One example is the animated Comet in ...
27
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3answers
5k views

What does the Sun-Earth-Moon system look like from the Sun-Earth L-2 point?

The L-2 point of the Sun-Earth system is away from the Earth on the night-side of the Earth; i.e. it's always local midnight at the sub-satellite point. This is an attractive property for some ...
27
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3answers
7k views

How are astronauts in the ISS protected from electric shock?

On Earth, most of the electrical appliances having exposed metal parts, such as electric iron, are grounded, to protect the user from electric shock when an uninsulated-wire accidentally comes into ...
26
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9answers
8k views

Can a satellite orbit Earth so that it always has the Moon in line of sight?

Could a satellite, without too much fuel consumption for station keeping, orbit the Earth so that it always has a line of sight to the Moon? It would need a near polar orbit which precesses in tandem ...
26
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3answers
3k views

Is it possible to have an orbit around the earth and the moon

I was just wondering if it were possible to A) Orbit the moon and earth B) To orbit any two celestial bodies really?
19
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5answers
5k views

Is a midspace space station between Earth and Mars practical?

A recent answer included the following: For example if you were to start a colony on mars, in this order for supplies and other necessities to be delivered there would need to be a network of space ...
17
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5answers
3k views

Is Mohs scale of mineral hardness applicable for rocks and minerals of terrestrial planets other than Earth?

The Mohs scale of mineral hardness is a qualitative ordinal scale characterizing scratch resistance of various minerals through the ability of harder material to scratch softer material. Now there is ...
17
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3answers
4k views

If the Earth spun clockwise, how would that affect Space Exploration?

If viewed from the North Pole, the Earth spins counter-clockwise. Because of this, many satellites also orbit in the same direction as you can take advantage of the Earth's rotation and essentially ...
14
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3answers
3k views

Earth Moon Pork chop plot

Does pork-chop plots exist for Earth-Moon System? I could only find pork-chop plots for Earth-planet systems.Could someone please shed some light on this topic?
14
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2answers
2k views

Why does the Earth lose rotational velocity in the vacuum of space?

I think it is a well-known fact here that the Earth is slowly losing rotational velocity over time (some 1.4 milliseconds of the day are gained per hundred years). Eventually, this means that the ...
14
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1answer
5k views

How does the efficacy of solar cells on Mars compare with Earth?

Mars gets less than half the light that we get on Earth and there are dust storms, but the atmosphere is much thinner and there are no clouds. After all factors have been considered, how effective are ...
13
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1answer
1k views

Are there any proposals for a permanent orbital interplanetary ferry?

I believe I read in a book once a description of a kind of interplanetary ferry that would orbit the sun and regularly pass different planets like Mars and Earth. The idea of the ferry is to have a ...
12
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2answers
697 views

What existing life on Earth is best suited for the Martian environment?

What existing life on Earth is best suited for the Martian environment? By best suited, I mean it could theoretically be placed on Mars and easily adapt or thrive within the existing environment the ...
11
votes
2answers
511 views

Why is the surface of Mars oxidized?

Before 2.5 to 2Gya, Earth's surface was a chemically reducing environment (evidence includes reduced forms of iron, sulfur, and uranium in rocks before that time). It is believed to have become ...
10
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2answers
219 views

Why do many Mars missions launch now, if the Hohmann transfer orbit is the most propellant-saving one?

The Hohmann transfer orbit is the most propellant-saving transfer orbit to Mars. When using this kind of transfer, the rover/rocket/etc. starts from Earth when Earth and Mars are in conjunction. But ...
10
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1answer
1k views

How would changes in the Earth's magnetic field affect space exploration?

It is well-known that the Earth's magnetic field may flip (geomagnetic reversal), and some data suggests it is weakening or distorting. The following shows the Earth's magnetic field at its surface in ...
9
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2answers
3k views

What is the effect of gravity slingshots around Earth on Earth's rotation and orbit time, and is this effect worth considering?

Several space probes have used gravitational slingshots around Earth as part of their mission plan to get to other places in our solar system. Some examples I could find quickly are Galileo, Messenger ...
8
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4answers
7k views

Is it possible to touch stars with our bare hands?

Well I'm new to Space SE and have gone through many questions but I couldn't help but notice that is it even remotely possible that one can touch the stars without burning him/her self ? Is there any ...
8
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3answers
3k views

Why is the earth so small when observed from the moon?

I recently discovered the pictures from DSCOVR taken at the Lunar Transit in 2016. The earth appears very massive behind the moon, which is a little unintuitive if you consider how small it is when ...
8
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1answer
1k views

What materials are naturally released into space from earth?

I am wondering what kinds of materials that are released by Earth into space due to natural processes. If possible, what are their approximate rates in kg per day or year?
8
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1answer
2k views

What is the brown band in which we find the pale blue dot that is Earth?

In the famous "pale blue dot" picture: we see Earth in a brown band. What is that band? Is it an artifact of the camera? Is it a ring of dust orbiting around the Sun akin to the rings of Saturn and ...
8
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2answers
1k views

Could you launch rocks from the Moon to hit Earth?

In the Robert A. Heinlein novel, The Moon is a Harsh Mistress, the plot famously revolves around sending rocks from the Moon to Earth, launched via electromagnetic rail gun and the impacts looked like ...
7
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3answers
1k views

Could the Apollo astronauts distinguish Earth's continents and oceans from the moon?

This article "Earthshine Reflects Earth's Oceans And Continents From The Dark Side Of The Moon" indicates that the difference in reflection of light from the Earth’s land masses and oceans can be seen ...
7
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4answers
1k views

Wasn't the moon landing + reentry much harder to do than SpaceX's reusable rockets/boosters?

Over 45 years ago, we know that USA/Russia were able to send satellites/humans and return them to the Earth. Isn't that supposed to be much more difficult to do than what SpaceX is doing now by ...
7
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2answers
884 views

What Earth gravity model is used for different types of calculations?

When performing orbital calculations, under what circumstances should I assume: a perfectly spherical Earth a reference ellipsoid a geoid no particular format at all
7
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1answer
1k views

Is it possible that the earth is in a nebula?

From this question in World Building, it is speculated that planets in nebulas are not greatly affected by the presence of the nebula. This being the case, how do we know that the earth itself is not ...
7
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0answers
301 views

Why doesn't jupiter look bigger than our moon? [closed]

If Jupiter is 365 million miles away from earth. Our moon is about 238,900 miles away from earth. that means Jupiter is 1527.8 times farther away from the earth than the moon. Jupiter is 5285.2 times ...
6
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2answers
668 views

If there was a probe orbiting at the edge of Earth's Sphere of influence, how slow would it orbit?

Would it orbit very slowly? It's kinda been stuck in my head lately...
6
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2answers
762 views

Physical meaning of perigee advance

I'm starting to study orbital perturbations and I can't find any physical explanation about the perigee advance (apsidal precession) when considering Earth oblateness effects. Can someone give a ...
6
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1answer
348 views

At what altitude do the effects of atmospheric drag completely disappear?

The spate of K-questions got me thinking: At what point does atmospheric drag disappear1 with the pressure from sunlight, solar wind, or other forces becoming overwhelmingly dominant? I'm guessing it'...
6
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0answers
62 views

Could Breakthrough Starshot be used to deflect asteroids and comets?

Would Breakthrough Starshot be able to deflect an asteroid or comet? I have seen thoughts about using the lasers that would launch Breakthrough Starshot to deflect asteroids or comets: https://www....
6
votes
1answer
120 views

Do astronauts on ISS notice Earth's seasons?

Has anyone stationed on the ISS for some months reported noticing the changing seasons on Earth in any way like people on the surface do, subconsciously without needing to look up numbers for anything?...
5
votes
1answer
381 views

Is there any life from Earth that can live on Mars?

Does Mars have any environment in which a plant, virus or otherwise would be capable of living on Mars without an artificial environment? Is there anything that can live below the Armstrong Limit on ...
5
votes
1answer
347 views

Are L1 to L2 and back “cheap” transfers/cyclers possible?

This paper studies transfers from halo orbit to halo orbit in the Jovian system. I wonder if there are any locally stable orbits connecting Earth-Moon L1 and L2 points. EDIT: One should also consider ...
5
votes
2answers
893 views

Extinction asteroid (10-100 km) impact avoidance

With the present "state-of-the-art" of space technology what is possible to do to avoid an Earth impact by rocky bodies 10 km to 100 km in diameter? Is there any international project to develop a ...
5
votes
1answer
331 views

Is it possible to take another Pale Blue Dot image?

Pale Blue Dot is a photograph of planet Earth taken on February 14, 1990, by the Voyager 1 space probe from a record distance of about 6 billion kilometers (3.7 billion miles, 40.5 AU), as part of ...
5
votes
1answer
363 views

How has the angular velocity of Earth changed over the past 100 years?

What is the total change in the Earth's Angular Velocity over the past 100 years? I have read other posts that discuss how much mass has been lifted out of Earth's Atmosphere. I'm trying to get an ...
4
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4answers
2k views

How to respond to the case against space? [closed]

I am an avid space advocate and even studied aerospace engineering in college, however, I still struggle with a great answer to this question: "Why explore space?" A few days ago an old professor who ...
4
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2answers
4k views

Earth angular size looking from the ISS

Imagine you're, well, actually on the ISS so you're 395 km up. We've all seen many photos roughly like this... however this can be deceptive; They might be all fisheye lenses. A great many of these ...
4
votes
1answer
707 views

Are we changing Earth's rotation?

Can rockets launching change Earth's rotation, and can going into orbit do the same?
4
votes
1answer
228 views

At what point when travelling faster and faster around the earth are you not gonna be falling back again (7km/s? 8km/s?)

My dad and I thought about a problem we had when discussing Earth's gravitational field. This wasnt the original question but I still would like to know the answer. So essentially my question is: ...
4
votes
1answer
334 views

Earth-based microwave radiometer for the Moon

Microwave radiometers (MWR) can be used passively, to get regolith's thickness, brightness temperature and dielectric constant. Apart from that, I have little idea of how the instrumentation's ...
4
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0answers
10k views

Earth's rotation speed vs latitude [duplicate]

The above question may sound naive. Still I would be thankful to someone who helps me in understanding the concept. In the following link it is mentioned that earth's rotation speed with respect to ...
3
votes
2answers
1k views

Would an asteroid collision affect Moon's orbit, and what consequence would that have for Earth?

If an asteroid collided with the Moon, or an atomic bomb was blasted on it, would it affect the orbit of the Moon? The Moon's gravity plays a major role in ocean tides. If the Moon's orbit changed, ...
3
votes
1answer
1k views

Why doesn't all space debris burn up? [duplicate]

Man-made satellites have to use boosters to accelerate to maintain orbit around the Earth. Space debris and old satellites with depleted boosters should be either pulled by Earth's gravity, or slowed ...