37
votes
Can a magnetic field of an object be stronger than its gravity?
It depends on what object it's acting on. There are many objects, including stars, that have magnetic fields where Lorentz forces on charged particles like electrons and protons are stronger than the ...
- 5,142
23
votes
Accepted
What would the night sky look like if the Milky Way were the only galaxy in the universe?
I feel sure this is a repeat, but couldn't immediately find it. The only things in the night sky we can see (with the naked eye) that are not part of our own Galaxy are (on a good night) the Andromeda ...
- 114k
18
votes
What would the night sky look like if the Milky Way were the only galaxy in the universe?
It wouldn't be too apparent, but there are a few objects that you can see in good viewing conditions with the naked eye that would disappear.
Here they are in order of brightness. I marked the ...
- 844
17
votes
Accepted
Can a magnetic field of an object be stronger than its gravity?
Let's look at the proper magnetic force (as opposed to the Lorentz force on a moving, charged object described in @KenG's answer) on a specimen $S$ of magnetized material with mass $M_S$ as a way to ...
- 31.4k
16
votes
Accepted
Are there more stars than all the words ever spoken by humans?
Number of stars in the observable universe
There are about 100 to 200 billion galaxies in the observable universe. Galaxies range in size from a few billion to hundreds of trillions stars. Using 100 ...
- 27.1k
14
votes
Accepted
On what basis is the information about the distance and velocity of the Voyager probes determined?
On what basis is the information about the distance and velocity of the Voyager probes determined?
For distance: round-trip travel time of radio signals
For velocity: Doppler-shift of round-trip ...
- 31.4k
13
votes
What was the length of the solar day 73 million years ago?
There is evidence from Silurian coral fossils that, 430 My ago, there were 420 daily rotations in each annual season, compared to 365 days per year now. If we assume that the year (fixed by mean ...
- 971
12
votes
Accepted
How to discover Neptune from the Uranus orbit (by computer simulation)
Here is what I did:
Based on their masses, it is safest to initially consider Jupiter and Saturn as well as Uranus. It might also be fruitful to include the Earth in the analysis, to get relative ...
- 401
11
votes
Accepted
Why do we use FITS format for scientific images especially in astronomy? How is it different from formats such as JPEG, PNG etc?
File formats tend to be industry/field-specific, with the format, tools, and expectations of the field coevolving to become more dependent on each other over time. JPEG co-evolved with amateur digital ...
- 425
11
votes
How to know that the 21cm Hydrogen line is the actual emission and not any other redshifted line?
No, not really. The first thing is that we know that ${H}$ is far more abundant than other elements or simple molecules in the universe. The next thing is that the 21 cm line comes from a ...
- 3,529
11
votes
Accepted
What liquids can be found in the void space?
No liquid can be completely stable in a vacuum, since all liquids have some non-zero vapour pressure, and so will evaporate at some rate. However some liquids have an exceptionally low vapour pressure,...
- 87.7k
9
votes
Which is more rare: Lunar eclipse or Solar eclipse?
Solar and lunar eclipses occur about equally often - between two and four times per year.
However, when you do not intentionally travel around the world chasing solar eclipses, you are more likely to ...
- 747
9
votes
Accepted
How can I contribute to the scientific community using my telescope?
Amateurs do useful scientific work by being many-handed and widely spread.
Many Supernovae are discovered by amateurs. You need a set-up that can image one galaxy after another and look for any "new ...
- 87.7k
9
votes
Can a magnetic field of an object be stronger than its gravity?
It isn't impossible, but the short answer is "no".
A gravitational field will accelerate all matter and energy equally while a magnetic field will only accelerate moving electric charges (other ...
- 91
8
votes
Power of the James Webb Space Telescope
It all comes down to the brightness of objects (not their size). For all intents and purposes we can assume that the most distant galaxies and the small, but much closer, objects in the Oort clouds ...
- 114k
8
votes
Accepted
Astronomical ABCD...!
Seems a little contrived, essentially you just have to dig deep enough to find a specific enough category that matches the letter. But here you go :
K - KBO (Kuiper Belt Object) , if you still don't ...
- 196
8
votes
What do the months and hours mean in Tomas Filsinger's Map of The Universe
I am Tomás the guy that designed it following astrocartography traditions. The thing that makes it confusing is that the position of the little suns in the Ecliptic are plotted against the stars at 12 ...
- 111
8
votes
Accepted
Have there been studies of "old photons" to see just how constant things like Planck constant has been?
You can not check if a dimensional constant has changed because you can always reverse that change by a smart change of coordinates (system of units). Despite that, since the current Physics assumes ...
- 450
7
votes
Why didn't Johannes Kepler use data about more planets?
Kepler could, with a lot of work, apply his analysis to other planets of course - but it won't help in proving his point of elliptical path. There are only two planets where this elliptical path could ...
- 1,248
7
votes
Why didn't Johannes Kepler use data about more planets?
I know that quoting Wikipedia is frowned upon here, but as there has been no other answer posted, this is what the Wikipedia article on Kepler has to say about the matter:
He then set about ...
- 3,236
7
votes
Requesting book references for a non-expert person with math background or just a non-expert person
I personally found Stephen Hawking's "A Breif History of Time" to be very interesting and informative. It is a little bit advanced, but is put forward in plain English. Here is a link to it on ...
- 3,919
7
votes
How would the night sky look from inside a globular cluster?
In fact, some people had looked at it more seriously recently and conducted a computer simulation to visualize the night sky as seen from within a globular cluster.
The article has appeared recently ...
- 2,651
7
votes
Can some stars not emit any energy in the visible spectrum?
Light that is not light
That's meaningless. All light is electromagnetic radiation. A finite part of the infinitely large range of the electromagnetic spectrum is visible light. So you should talk ...
- 5,641
7
votes
Accepted
When black holes forms out of a supernova do they have a very high velocity?
There is no specific answer to this -- anything from "just sits there" to flys away at high speed is possible.
It all depends on the symmetry of the supernova (SN) explosion. Extensive modelling ...
- 7,380
7
votes
Accepted
What do the months and hours mean in Tomas Filsinger's Map of The Universe
The hours show the lines of right ascension, where right ascension is one of two coordinates used to specify a point on the sky. (The other coordinate is declination, measured in degrees from the ...
- 7,073
7
votes
Accepted
Why the more-luminous star has larger surface area when two stars have the same temperature?
I'd say your problem is that you are imagining the light rays emanating out from the center of the star. Try it again with light emanating from each square area on the surface, and you will see that ...
- 5,142
6
votes
Accepted
A curious relationship between lunar periods and the solar year
The synodic month is the "average period of the Moon's revolution with respect to the line joining the Sun and Earth". However, the Earth also moves in its orbit around the Sun during this month. ...
- 778
6
votes
How and when did we learn about the universe?
Throughout man's history, we have been learning things about the universe we live in.
Probably one of the most interesting discoveries that let us know how amazingly large the universe really is was ...
- 3,204
6
votes
How many astronomers are there in the world today?
"The worldwide community of professional astronomers is only about 10,000; most are located in the us (with about 1,000 in the UK and 250 in Australia)." From So You Want to Be an Astronomer by Duncan ...
- 401
6
votes
Equations for coordinates of solar system objects
It depends a bit on how precise you would want to be. A very good discussion on how to calculate the orbits of solar system objects is given in the book by Jean Meeus, Astronomical Algorithms (1999), ...
- 3,311
Only top scored, non community-wiki answers of a minimum length are eligible