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 ...
- 129k
48
votes
Accepted
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 ...
- 3,964
45
votes
Accepted
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 ...
- 5,064
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 ...
- 129k
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 ...
- 15.7k
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 ...
- 461
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 ...
- 129k
26
votes
Accepted
Are spacecraft visits to Uranus and Neptune hard to plan?
Uranus and Neptune are far - in orders of light-hours away. It took Voyager 2 nearly a decade to reach Uranus since its launch, costing almost $1B to build it in the first place.
It's not that we can'...
- 1,144
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 ...
- 2,877
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 ...
- 36.3k
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&...
- 162k
16
votes
Accepted
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 ...
- 129k
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 ...
- 3,054
14
votes
Accepted
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 ...
- 498
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 ...
- 129k
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.
...
- 15.1k
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. ...
- 211
11
votes
Accepted
Voyager spacecraft distance from Earth
We can access trajectory data for the Voyagers via the Horizons system of JPL. For various reasons, Horizons didn't have great trajectory data for these spacecraft. However, in 2022, R. Jacobson (...
- 16.7k
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 ...
- 30.7k
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 ...
- 4,823
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 ...
- 400
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 ...
- 1,076
9
votes
Attach a visible light telescope to the outside of the ISS
Attach a visible light telescope to the outside of the ISS
This is a reasonable idea and it has been thought of before, but usually for other-than-visible light. Other answers do a good job of ...
- 30.7k
9
votes
Is space really empty?
No. Space isn't empty. There are atoms. The density varies quite a lot, from a million atoms per cubic centimeter to fewer than one per 100000 cm³. Mostly this is in the form of hydrogen.
And there ...
- 129k
8
votes
Accepted
The photos of the outer space
The same way I can take photos of my neighbourhood without leaving my house; light travels from the surrounding houses, through my windows, and I capture that light in a photograph. No need to leave ...
- 2,630
8
votes
Has THC been detected in space?
The detection of complex organic molecules, often abbreviated as COM in astrochemical literature, has only taken up pace in the last couple of decades since substantial advances were only made ...
- 183
8
votes
In a planetary system close to the galactic core, would it be possible to see the supermassive black hole?
There's a thing called gravitational lensing, which means that light coming from behind the black hole would bend towards it, and since the galactic core has a lot of stars, it might be that instead ...
- 181
8
votes
Accepted
How much of the Universe is subatomic?
First things first ...
Tachyons
These are entirely hypothetical and no evidence for them exists.
How much does subatomic particles such as photons, tachyons, and electron being the biggest ...
- 6,401
Only top scored, non community-wiki answers of a minimum length are eligible