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107 votes
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Which country borders are visible from space?

The border between India and Pakistan is one of the most heavily guarded and well-lit borders in the world, so much so that it can be seen from space at night. It covers an immense distance from the ...
karthikeyan's user avatar
  • 4,479
98 votes

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)?

The comet's tail always points away from the Sun. Yes, even when the comet is heading back into the outer solar system. This is because the tail isn't a 'trail' of where the comet has been, like a ...
Ingolifs's user avatar
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82 votes
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Is it true that NASA is hiring a new 'planetary protection officer'?

You're observing shamefully bad journalism. The "protect Earth from aliens" bullet point in the "Highlights" section of the article was put there by an editor who either ignorantly ...
Russell Borogove's user avatar
78 votes
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Shouldn't space junk fall back to Earth on its own? How long will take for a ~1 cm piece of junk in LEO to fall back to Earth on its own for example?

It depends on the altitude. Here is a chart from ESA and UNOOSA. Basically, anything under 500 km will fall relatively quickly, maybe 25 years. Everything under 800 km should fall within a century or ...
PearsonArtPhoto's user avatar
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72 votes
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Why is my Earth simulation slower than the reality?

In your simulation, the camera (or the viewers perspective) is stationary in what seems like in an altitude of a geostationary orbit. However the ISS is not stationary, it is travelling 7.6 km/s. It ...
Star Man's user avatar
  • 5,908
51 votes
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Are pictures of Earth' space junk realistic?

No, it's entirely unrealistic. The Earth is very large by the standards of what you deal with in day to day life -- it's about 13 million meters in diameter. Satellites are typically only a few meters ...
Russell Borogove's user avatar
44 votes
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Was the "Earthrise" witnessed by Apollo 8 the first available "full" photo of the Earth?

No; the first full views of Earth from high-altitude satellites predate Apollo 8 by at least two years. This web page has a nice progression of pictures of Earth from space from 1959 on. A Soviet ...
Russell Borogove's user avatar
41 votes

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

Primarily, locations of spaceports would change. California, not Florida would host the NASA's main launch site. Russia would be in slightly better position, able to send rockets over the Black Sea, ...
SF.'s user avatar
  • 55k
37 votes

Is a midspace space station between Earth and Mars practical?

You're right: this has issues. You can insert a station into a circular orbit halfway between Earth and Mars, but because this has an orbital period also in between those of Earth and Mars, your ...
Hobbes's user avatar
  • 127k
36 votes
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Is it possible to have an orbit around the earth and the moon

The simple answer is yes. The more complicated answer starts to look at types of orbit. You could have a figure-8 orbit, which has centres around both. You could have an orbit that goes around ...
Rory Alsop's user avatar
  • 13.6k
36 votes
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How are astronauts in the ISS protected from electric shock?

It isn't the actual level of charge (potential) that causes electric shock. but being connected to two things (like your iron and the ground) that are at different levels. Hence why birds can sit on a ...
Steve Linton's user avatar
  • 19.6k
36 votes

Are pictures of Earth' space junk realistic?

The "actual data" is that for every one of their dots, there is probably a real debris fragment, the mix of satellites/rocket bodies etc is probably broadly right, and so on. However, the ...
Andrew is gone's user avatar
31 votes
Accepted

Earth Moon Pork chop plot

So let's break down the answer into bite sized chunks... How do you transfer a spacecraft from one solar system body to another? There are two main things you need to do. Set up an orbit that ...
Ingolifs's user avatar
  • 6,428
30 votes
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Why all the 'dust' on liftoff?

I took some screenshots of the linked video. At T+1 seconds watch the water spray nozzles, four on the left and the right side of the rocket. At the right side of the image a mixture of water and ...
Uwe's user avatar
  • 48.9k
28 votes
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What is the largest piece of space debris volumetrically?

Initial and Bonus Answer: With a volume of 609.31 M^3 and an empty mass of 15,500kg (13,500 kg empty weight plus 2,000kg for the attached Instrument Unit), J002E3 is Apollo 12's S-IVB stage (...
Justin Braun's user avatar
  • 2,275
28 votes

Shouldn't space junk fall back to Earth on its own? How long will take for a ~1 cm piece of junk in LEO to fall back to Earth on its own for example?

Space debris poses a real risk for spacecraft in LEO. From the Technical Report on Space Debris UN Committee on the Peaceful uses of Outer Space (Table 5), a satellite in orbit can expect to collide ...
Woody's user avatar
  • 21.4k
23 votes

What is the largest piece of space debris volumetrically?

I would say it's probably Envisat. It is definitely the heaviest although i'm not sure if it is also the largest piece volumetrically. We had a full scale 'mock up' at our faculty and I can confirm ...
Alexander Vandenberghe's user avatar
23 votes
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Why do many Mars missions launch now, if the Hohmann transfer orbit is the most propellant-saving one?

The thing your're missing is that the Hohmann Transfer orbit takes time, and both Mars and Earth are moving around the sun. For the Hohmann Transfer orbit to work, the position of Mars at arrival has ...
notovny's user avatar
  • 5,429
22 votes

Why is my Earth simulation slower than the reality?

As others have noted, the ISS orbits the earth extraordinarily quickly, and that explains the discrepancy. However, there may still be a small error in your simulation. Whether or not there is an ...
Eric Lippert's user avatar
22 votes

How are astronauts in the ISS protected from electric shock?

"Earth" doesn't work the way you might think. In any case, on a vehicle of almost any kind, "earth" is replaced by "metal chassis". Your question is based on a very common misconception: that ...
Harper - Reinstate Monica's user avatar
21 votes

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

Although not a blue marble as it's in black and white, Lunar Orbiter 1 took an earlier Earthrise photo on August 23, 1966. This is the first picture of the Earth from Lunar orbit. In 2008, the Lunar ...
David Moews's user avatar
21 votes

Earth Moon Pork chop plot

Does pork-chop plots exist for Earth-Moon System? No, because the concept doesn't make much sense. The Earth-Mars configuration and Mars' eccentricity makes the cost to send a vehicle from Earth to ...
David Hammen's user avatar
  • 73.8k
21 votes
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If we had a video livestream of a clock being sent to Mars, what would we see?

The main idea here is just that it takes time for light to travel, which is the same thing as the Doppler shift (the longitudinal version which applies at all speeds, not the relativistic transverse ...
Ryan C's user avatar
  • 7,852
19 votes
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Is Mohs scale of mineral hardness applicable for rocks and minerals of terrestrial planets other than Earth?

Yes, because for the vast majority of minerals you can find in space, they are the same as those you can find (or synthesize) on Earth. A pyrite in space is a pyrite just like on Earth. A wollastonite ...
Anton Hengst's user avatar
  • 10.7k
18 votes

Which country borders are visible from space?

Another border which is visible due to the lack of light is the Haitian border with the Dominican Republic: The area highlighted on the left is Haiti, of which only Port Au Prince can be seen at ...
A Gibb's user avatar
  • 181
18 votes

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

Yes, but with a couple modifications. On some planets, notably Venus within our Solar Systen, different conditions from those on Earth, especially temperature, can affect mineral hardness. Pyrite is ...
Oscar Lanzi's user avatar
  • 8,495
18 votes

Are pictures of Earth' space junk realistic?

We cannot depict the space junk to scale. Neither the human vision, nor modern imaging technology can have both Earth and whatever human-made orbiting object visible at the same scale, without having ...
fraxinus's user avatar
  • 2,249
17 votes

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

A reasonably accurate1 rendering can be made with Celestia. Here we are at 1,500,000 km from Earth's center, on August 26, 2018 (the next full moon as I write this), at approximately the Earth-Sun L2 ...
Phil Frost's user avatar
  • 1,033
17 votes

Which country borders are visible from space?

Most of the answers were concerning night time pictures. Let me add some nice example of day time pictures, of Israel. Plenty of grazing animals on the Egyptian side of the border, but none on the ...
Gimelist's user avatar
  • 271
16 votes
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Is it possible to touch stars with our bare hands?

Surprisingly, yes, for some of them. Small, old stars can be at room temperature ex: WISE 1828+2650, so you could touch the surface without getting burned. Any star you can see in the sky with the ...
Antzi's user avatar
  • 12.7k

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