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  • 109 votes cast
Apr
2
comment What is the definition of “deep space”?
@Dean You miss my point, which is that any definition of relative terms like 'deep' and 'far' are **completely arbitrary. Ten feet below the water's surface is deep if you are in a swimming pool, but quite shallow if you are in an ocean. Similarly, the question of whether or not the Sun is in deep space or not has no fixed answer if no reference unit of length is first specified.
Apr
2
answered What is the definition of “deep space”?
Mar
22
awarded  Popular Question
Mar
1
comment Is it safe to watch solar eclipse's reflection in water?
No. There will be a very brief period where is could potnentially be safe, but in order to watch for that moment you would need to watch the reflection while it is damagingly bright. There are better low-tech methods available. But good on you for planning this event with your son! I was in my mid-20s when I brought my dad along to see our first eclipse together. It was special even then. :)
Feb
5
awarded  Quorum
Dec
29
awarded  Yearling
Nov
30
comment Are we sure there are no planets inside Mercury's orbit?
Using the IAU definition of a planet, I'm pretty sure we can. Observations of Mercury's orbit place significant upper bounds on the mass of any additional bodies potentially existing between Mercury and Sun, while part of the IAU definitional criteria for being a planet stipulates that it must be massive enough to reach hydrostatic equilibrium.
Jul
13
comment Energy required for light speed
It's not quite correct to say that traveling at light speed would require infinite energy. Rather, it's that acceleration to lightspeed from a rest frame that requires infinite energy for a massive object. No finite transfer of energy/momentum is sufficient to boost the velocity up to lightspeed. Note that photons are in similar position. No finite transfer of energy is capable of slowing a photon down to below lightspeed. Only it's frequency and wavelength change.
Jun
27
comment Dark Matter Detection
Perhaps arxiv.org/abs/1503.02320 ?
Jun
27
comment What to do after first year of amateur astronomy?
Once you've learned how to make basic measurements, it's always fun and satisfying to prove to yourself that you can actually put those measurements to good use and deduce other things. See if you can derive accurate values for a planet's basic orbital parameters. If you are particularly ambitious, you could try to verify Kepler's laws, or determine Newton's constant.
Jun
27
comment Abbreviations for days of the week
I'd be surprised if there was any set standard convention. The day of the week by itself has no use in astronomy unless you also know the corresponding calendar date. And since the day of the week is computable from the calendar date, it's really just superfluous information. Nevertheless, most astronomy apps such as Sky Safari seem to use the first three letters abbreviating the names for the days of the week, so you're probably safe going with that.
Jun
9
accepted Coordinate transformations between reference frames in spherical astronomy
Jun
9
accepted How might Thales have predicted a solar eclipse?
Mar
27
comment How did water get on Earth
Well, of course the water would have been vaporized on impact. The result is water vapor, which eventually becomes rain.
Mar
1
comment What are the cloud-like blobs in the Martian southern hemisphere?
I'm not sure how I feel about questions like these. As the article says, there doesn't seem to be any consensus within the astronomical community yet on the nature of these clouds, so any answer we might give you would just be repeating speculations...
Feb
18
comment Did we ever actually see the earth revolving around the sun? Is the geocentric model completely disproved?
In a similar vein, we also have a couple of probes crawling around the surface of Mars at the moment, and every indication so far is that there is no argument in favor of geocentric models that wouldn't work just as well to justify a Marti-ocentric model.
Feb
7
comment If Kepler-444 planets existed for 11.2 billion years, why fear for life on Earth after six billion years?
Scientists don't fear for the Earth. They fear for the life on it, specifically for the human variety. High surface temperatures will render the Earth uninhabitable in a billion years or so, but the planet itself will be just fine for a while after that.
Feb
7
comment How do moons get captured?
And I personally would appreciate a source for the third paragraph (not because I doubt it, but because I was I was ignorant of it). I was aware of the dissipating effect of tidal forces on the Moon's spin-angular momentum, but I hadn't considered influences on orbital-angular momentum.
Feb
6
comment How do moons get captured?
Short answer: the Sun. The hyperbolic path is derived by solving the gravitational two-body problem. If Earth and Moon were the only two objects in the universe, then yes the Moon would have continued along that hyerbola. Once you add a third body into the mix, the resulting trajectories become radically more complicated.
Feb
6
comment Why there are other planets in our solar system?
@user804401 I would suggest you edit your question to make it more clear that you are asking what effects other planets might have on the earth, because that's actually an interesting question to ask.