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Questions tagged [earth]

Questions of the science and space exploration related to Earth.

60
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9answers
11k 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 ...
5
votes
1answer
82 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'...
1
vote
1answer
64 views

Would a debris field on Mars look like one on either the Earth or the Moon?

I am assuming there are no photographs, with enough resolution, of the any of the debris fields of Mars probes that crashed into the surface of Mars to indicate what the debris field looks like. I am ...
2
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1answer
70 views

Hypersonic Inflatable Aerodynamic Decelerator entry to Mars' atmosphere

Is it known whether or not a Hypersonic Inflatable Aerodynamic Decelerator inflation and entry into Mars' atmosphere would produce more violent vibrations and lateral movements than was experienced by ...
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 ...
0
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1answer
199 views

How long was the trip from Earth to Mars for Insight?

How long was the trip from Earth to Mars for Insight from blastoff to landing?
4
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1answer
113 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: ...
0
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1answer
68 views

How to match orbital speeds of 2 or more satellites in different orbits?

Satellite ME is orbit around the Moon and Earth. Satellites E is around Earth. I understand the low orbit satellites orbit at higher speeds. Can Sat ME match the speed of any of Satellites E at any ...
0
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1answer
81 views

How large would a alien spaceship have to be to affect the earths gravitational orbit? [duplicate]

Would a large enough ship generate enough gravity to affect earths course?
5
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1answer
261 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 ...
3
votes
1answer
124 views

Which mission delivered the first ever complete photograph of the Earth?

So far, I found a picture made from a captured V missile launched in US to image part of the Earth. Which mission did deliver a full view of the Earth from the space? Note. Of course it's ...
1
vote
1answer
110 views

How much asteroid can we divert from the Earth?

There are many movies with the Earth being saved by sending a bomb out blow up the asteroid. What realistically could we do to that degree today? Do we have interplanetary missiles? if so how much of ...
3
votes
1answer
403 views

How to calculate GEO (geostationary) satellite eclipse time?

The positions of satellites in geostationary orbits can be characterized by their longitude, the longitude of a point on Earth's equator that is nadir to the spacecraft. Satellites in GEO will ...
0
votes
1answer
66 views

Can an Earth like planet support life by building a Dyson Sphere across a White Dwarf? [closed]

(Hypothetical Concept) But is it possible to depend on a white dwarf as our power source? Provided we harness its 99% of energy? Can life be sustained?(If it is possible we can easily colonize an ...
1
vote
0answers
40 views

If earth span fast? [closed]

Imagine earth spinning at very high angular speed. What it would feel like at various latitudes from 0 to 90 degree ? Like at 0 degree one may feel lighter than his weight. At 45 degree one is going ...
1
vote
2answers
134 views

Help computing solid angle subtended by the Earth as seen from LEO

I would need to compute the solid angle of the Earth from a spacecraft when close to the Earth, where no small angles approximation can be made. I thought it wouldn't be that hard but I feel actually ...
2
votes
1answer
58 views

Plotting error values between simulated and JPL data

I'm attempting to compare values between my simulated data for the solar system and the official JPL data, to find errors for the position, velocity, inclination and azimuth. The simulated data was ...
0
votes
2answers
119 views

How do constellations appear to stay constant despite Earth's spin and orbit? [closed]

Our Earth is spinning and also orbiting the Sun, so how do the constellations appear fixed and constant? Almost all galaxies and stars are said to be fixed relative to constellations.
0
votes
1answer
95 views

Earth Habitable zone

The question is "Find the maximum orbital eccentricity that the Earth would be allowed to have if it stays in the “habitable zone” all the time. Be careful to define what you mean by “habitable zone""....
2
votes
0answers
41 views

Why did DSCOVR increase its pictures rate on February 3rd 2018?

On February 3rd for some reason NASA tuned up DSCOVR to send images of the Earth every 20min instead of the regular 2 hours interval. Last time they did this was for the great USA solar eclipse, in ...
7
votes
1answer
458 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 ...
1
vote
1answer
423 views

Finding the true anomaly

I've read from a page that you can find the distance from the Sun to the Earth via the following equation: $$r = a\frac{1-e^2}{1+e\cdot \cos(θ)}$$ where r is the distance from the Sun, a is the semi-...
3
votes
1answer
344 views

What's the unshielded radiation dose in mSv in Low Earth Orbit?

Say we have a guy orbiting Earth in LEO with no spacesuit (I know, I know), what would be the millisieverts he would be receiving?
1
vote
2answers
283 views

What is the Fischer 1960 Mercury Ellipsoid, and why is it called that?

Don't be distracted by the 1960 Mercury shown below. Reading about Irene Fischer (also here, and mentioned in this answer) and seeing the Fischer 1960 Mercury Ellipsoid turn up in tables of ellipsoid ...
2
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2answers
182 views

Are there any protocols the space station follows if there is an Earth-wide catastrophe?

Are there any protocols the space station (or any space explorer) follows if there is a massive catastrophe on Earth where the responsive parties on the ground would not be available for support/...
5
votes
2answers
345 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 ...
3
votes
1answer
813 views

Roughly, how fast do rockets travel?

I know that different rockets are built with different a range of different sizes or purposes, but there must be some kind of range of typical speeds for those things when leaving the Earth. So how ...
3
votes
1answer
4k views

Does escape velocity apply to rockets? [duplicate]

I know so far that escape velocity on the surface of Earth is 11.2 km/s Wikipedia says that escape velocity is the minimum speed needed for an object to escape from the gravitational influence of a ...
7
votes
1answer
251 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 ...
32
votes
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 ...
2
votes
2answers
911 views

Launching a rocket from a weather balloon for a very small payload

I am new to the site and am unaware of the correct formation of my question. That being said, I wanted to know if this is plausable and what would be the correct way of tackling this idea. If I had a ...
6
votes
4answers
2k 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 ...
0
votes
1answer
133 views

What would happen to communication if we stayed in contact with a person going to mars?

If we talk to a person on mars it would take about 30 minutes before they would see the communication, but lets say we stayed in contact 24/7 by video calling starting from Earth, what would happen? ...
7
votes
0answers
183 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
581 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
3
votes
1answer
234 views

How big (broad) is GEO orbit?

This post got me thinking about something I've never quite been able to picture about geostationary orbit. In a perfect model of a spherical earth, there is an infinitesimal circle in the plane of the ...
1
vote
1answer
156 views

Smallest planet where human type life could evolve and survive?

Most exoplanets making the news are larger than Earth. I wonder about the smaller worlds, how small is too small? Reword to keep the question narrow enough to be answerable. When the Earth was ...
14
votes
1answer
2k 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 ...
6
votes
1answer
858 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 ...
1
vote
0answers
141 views

What is the highest resolution of infrared photography of Earth available from satellites?

What is the best resolution of infrared photo taken from space of earth? Is it possible to see on this picture, for example, animals or humans (temperature of body is different than ground)? Is it ...
1
vote
2answers
334 views

synchronized orbit between Earth and Moon

Is it possible to have a synchronized orbit between the Moon and the Earth, using the gravity of both bodies to hold its position (with some assistance, since the Moon's orbit is not circular). This ...
2
votes
2answers
91 views

How far could material from Earth or Mars be transported due to asteroid impact?

NASA has issued reports to the effect that small bits of Mars have come to Earth due to asteroid impacts - asteroid hits Mars, chunks are ejected into space far enough to eventually fall into Earth's ...
4
votes
2answers
4k views

Earth's rotation speed vs latitude

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 ...
1
vote
0answers
51 views

How slingshot is used to increase the speed of Juno [duplicate]

I have gone through the slingshot for the Juno with the earth. I have also seen the train and ball example as given by NASA. [http://solarsystem.nasa.gov/basics/grav/primer.php] But, I am still ...
1
vote
1answer
705 views

How to calculate Earth's velocity vector in ECEF?

I would like to write some AR mobile app that will show Earth velocity vector, but I have no any experience with astrodynamics. So how to calculate Earth's velocity vector in ECEF, having date and ...
18
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2answers
2k 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?
4
votes
1answer
321 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 ...
7
votes
1answer
254 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 ...
0
votes
2answers
118 views

Faster alternative to travel to any location in the west

Suppose one needs to travel to Somalia from Indonesia(which are approximately at a distance of $4000$ miles from each other on the line of equator). To accomplish this task, I suggest the following ...
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 ...