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58 votes

How can comets have tails if there's no air resistance in space?

There are two forces that can cause the formation of a tail: the solar wind and radiation pressure. The first misconception in your question is "the dust [travels] slower than the nucleus". The tail ...
James K's user avatar
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48 votes
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Could liquid water have existed in open space 15 million years after the Big Bang?

Let's interpret your question to be about whether the conditions would permit blobs of water to remain liquid, whether or not water existed yet. And the answer is No, because the pressure was by then ...
Mark Foskey's user avatar
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45 votes
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Why do astronauts move so slowly in zero gravity?

It's more for safety than anything else. Space is a very dangerous place for so many reasons. And making mistakes can very easily cause death. Being weightless does not mean you lose mass, so ...
Rory Alsop's user avatar
  • 5,073
38 votes

What would happen to a polished marble statue left in space for a million years?

There are three main space weathering processes that will affect the surface of the marble. Cosmic rays, high energy particle from the sun and beyond, will hit the surface. This can change the ...
James K's user avatar
  • 119k
37 votes

Why are there no stars visible in cislunar space?

It is a matter of exposure and dynamic range. A sensor like a camera can only handle inputs in a certain range of intensities, and much of photographic skill (or smart presets) is about mapping the ...
Anders Sandberg's user avatar
36 votes

How can comets have tails if there's no air resistance in space?

First, there is not just one tail, it is several, but when traveling far from a star, they are "aligned". When it gets closer the different materials behave differently, both depending on the ...
Viktor Mellgren's user avatar
29 votes
Accepted

Starting a fire in a cold planet that was full of flammable gas

The outer parts of Neptune are mostly hydrogen and helium. There are small amounts of other gases such as methane, ammonia and water vapour. However, there is no oxygen at all. If you took some of ...
James K's user avatar
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23 votes
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How cold is interstellar space?

You can stick a thermometer in space, and if it is a super-high-tech one, it might show you the temperature of the gas. But since the interstellar medium (ISM) is so dilute, a normal thermometer will ...
pela's user avatar
  • 37.6k
21 votes

Could liquid water have existed in open space 15 million years after the Big Bang?

As others have mentioned in the comments, there wouldn't have been any oxygen to form water. Soon after the Big Bang, the protons were hot or dense enough to fuse up to helium and some lithium but ...
Warrick's user avatar
  • 2,837
20 votes

Could an object enter or leave the vicinity of the Earth without being detected?

The Chelyabinsk meteor exploded over Chelyabinsk Oblast just shy of a decade ago. It was estimated after the fact to have been about 20 meters in diameter. No organization saw it before it entered the ...
David Hammen's user avatar
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18 votes
Accepted

Could the redshift of all incoming photons be explained by a massive ring of distant masses pulling the sources of the photons away?

You have identified the issues. The model does not explain the redshift-distance relationship, which is one of the primary pieces of evidence. Simply to say "our ideas about gravity are wrong&...
ProfRob's user avatar
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16 votes
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Space telescope located in outer solar system

The disadvantages would likely outweight the advantages. It's cold out there. This makes it easier to keep an infra-red telescope cool The sun's just a super-bright star. This means more of the sky ...
James K's user avatar
  • 119k
15 votes

Attach a visible light telescope to the outside of the ISS

A self-sufficient orbiting telescope is basically Hubble mkII and would never get off the ground, literally and metaphorically Hubble was expensive because it was state-of-the-art, requiring ...
Hobbes's user avatar
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14 votes
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Why are there no stars visible in cislunar space?

Anders's answer is entirely fine, but I'd like to add some extra information. As evidenced by the transcripts, reflected Earth light is quite strong even at this distance: The earthshine coming ...
Luaan's user avatar
  • 498
13 votes
Accepted

How can we hear the sound of the Sun?

Recently NASA has revealed that they have recorded the sound of Sun. They say that it produces a sound like "Om". I can't understand how they can hear it. It's not that recent (it was 2010), it wasn'...
David Hammen's user avatar
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13 votes
Accepted

How does the concept of a universe with no center work?

When we talk about the universe, we are really talking about one of two things: The observable universe, which is everything we can possibly see. The Universe, which is everything that has ever ...
Sir Cumference's user avatar
13 votes
Accepted

Is Universe Sandbox 2 realistic?

Not sure if these kinds of questions are allowed here, but I may as well answer it. Universe Sandbox 2 is mostly realistic. Its accuracy degrades as you increase the flow of time. The slower the time,...
Sir Cumference's user avatar
13 votes
Accepted

Why not build a swarm of space telescopes?

There are a mixture of factors here. Firstly the telescopes used to photograph the black hole were radio telescopes. Radio-waves are at a low enough frequency that we can process them directly as ...
James K's user avatar
  • 119k
12 votes
Accepted

Does the Sun have any atmosphere?

Yes the Sun has an atmosphere. Disclaimer: I'm not sure if you meant this, but your question implies the Sun is a planet. It, of course, is a star and not a planet. Just wanted to make that clear. ...
zephyr's user avatar
  • 15k
11 votes
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Why when we look through a telescope in space, do the billions of stars not block our view from seeing further?

OK, Imagine the stars at distance x block an area of the sky. At a distance of 2x there should be four times as many stars, but they would seem four times smaller in terms of area covered. Thus, the ...
SE - stop firing the good guys's user avatar
11 votes

How does the Earth not lose its atmosphere to space?

Your assertion that our atmosphere doesn't escape is wrong. Helium and Hydrogen atoms have a low enough mass that they do have an escape velocity at the temperatures on the edge of our atmosphere. ...
UKMonkey's user avatar
  • 211
10 votes
Accepted

Is it possible for a virus to come from a meteorite?

There is, believe it or not, a scientific theory regarding this: panspermia. According to the panspermia hypothesis, microbes "hitch" a lift on bodies leaving a planet. They then travel through space ...
HDE 226868's user avatar
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10 votes
Accepted

Which space telescope is the most distant?

Currently New Horizions is temporarily hibernating; it's last activity was two months ago. So I'm going to post a supplementary answer here because it is "operational" in the sense that it ...
uhoh's user avatar
  • 31.3k
10 votes

What is this object in this photo?

Almost certainly Jupiter, if the following are true: The title of the image: Inked20190904_194204.LI.jpg gives the accurate date and time of September 4 2019, 19:42:04. The orientation of the Moon in ...
notovny's user avatar
  • 4,770
9 votes

Is it possible for a virus to come from a meteorite?

Even if a virus came to Earth from space, it would likely be harmless to life on Earth. Let's look at some biology numbers: Life on Earth uses 20 amino acids (out of about 400 considered chemically ...
LocalFluff's user avatar
  • 11.4k
9 votes

How cold is interstellar space?

The title of the question asks about interstellar space, but the body asks about the interstellar medium. These are two very different questions. The temperature of the interstellar medium varies ...
David Hammen's user avatar
  • 33.7k
9 votes

In a planetary system close to the galactic core, would it be possible to see the supermassive black hole?

You couldn't see it as a black patch in the sky, because it's far too small. It's only 17 times the radius of our sun, which of course you can't see as a disc even from the outer reaches of our own ...
Mike Scott's user avatar
9 votes

How does the Earth not lose its atmosphere to space?

The underlying reason that the molecules of Earth's atmosphere do not fly away into the surrounding vacuum is that they are slower than the escape velocity, which would be 11200 m/s. The typical ...
Peter - Reinstate Monica's user avatar

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