Astronomy and Cosmology

this thread can be for stashing links to webpages with good explanations of astronomy stuff in Cosmology forum I just saw where aman asked about the slingshot effect (used a lot to save fuel on missions to the outer planets) and swansont gave this link: http://www.mathpages.com/home/kmath114.htm explaining clearly how the slingshot maneuver gains energy and angular momentum (taking away from the planet being used) and then Jenab confirmed having seen slingshotting in simulations he'd run http://www.scienceforums.net/forums/showthread.php?p=30823#post30823 I'm thinking of adding other good links i see to this thread, to have them handy. like link-answe…

In my spare time I will be writing a series of useful articles to help answer common questions. As these are being designed for forum reference I feel strongly on cooperative review. Here is the first. Please look over and feel free to make suggestions. Any solid contributions will be accorded credit at the end of the final product. (Key note all articles MUST comply with textbook descriptives, they are being designed as teaching aids) [latex]\textbf{The Cosmological principle}[/latex] is defined as "at sufficiently large scales, the universe appears as homogeneous and isotropic." [latex]\underline{Homogenous}[/latex] is oft defined as " no prefer…

Before posting on cosmo topics consider getting squared away on the conventional standard version. There are several great tutorials, for which I'll post link. And the standard model universe is embodied in some online calculators---playing around with them gives you some hands-on experience with redshifts, recession speeds, distances and so forth. Here's the authoritative up-to-date Einstein-Online tutorial on cosmology, written in understandable non-mathy language. http://www.einstein-online.info/en/spotlights/cosmology/index.html It is the cosmology part of a broad outreach site maintained by the Albert Enstein Institute, a worldclass science outfit in German…

Just a reminder that there is a Team SFN on the BOINC network, which you can join if you are running programs such as Seti@home. Blike set it up a while ago but I don't think it was ever advertised http://setiathome.berkeley.edu/team_display.php?teamid=134923

Ever since I was a young boy, I have wrestled with trying to understand space. In particular, I have never really understood how space is supposed to never end. I really don't see how that's possible. Everything ends somewhere. Where one thing ends the next begins. Can people please provide thoughts on this?

This seems like a new find that the universe is not expanding at the same speed depending on direction. https://www.nasa.gov/mission_pages/chandra/news/universe-s-expansion-may-not-be-the-same-in-all-directions.html how does this affect what we currently know with the age of the universe, the end of the universe and anything else we know or we thought we knew. i have included the actual paper if anyone is interested https://arxiv.org/pdf/2004.03305.pdf

Terraforming planets will take a back seat to building spacecraft that can be "all the comforts of home." Why make the effort to terraform Mars when you could much easier build a giant spacecraft that can travel for decades without needing anything, except to stop occasionally at an asteroid to collect water-ice for water, air and fuel, and some useful minerals.

Hi there. I'm writing a sci-fi story for a video game. At some point in time an advanced civilization from the future, say 4010, creates a wormhole for a not so advanced civilization spacecraft in the past, say 2050, to travel through. The idea is for the not so advanced civilization spacecraft to meet the advanced one in its own time, 4010. The question is (theoretically and sci-fi speaking): how many years would have passed for the advanced civilization in 4010 until the not so advanced civilization spacecraft arrived? Its possible that I'm missing some pseudo-scientific data so feel free to complement my reasoning. I hope I made it clear. …

I know it sounds like freaky, but I haven't found such evidence. I know that Galileo proved the possibility that when the earth moves as an inertial system, this movement may be imperceptible, but the possibility is not proof that this is the case. Similarly, with the reasoning of Copernicus and so on. Meanwhile, the ancient concepts of spheres are very close to what is actually observed, for example, distant stars are almost motionless, and so on. And besides, if we (purely hypothetically) admit the existence of the ether, then the immobility of the earth explains the absence of the etheric wind By the way, were there any attempts to detect the etheric wind…

All stars rise from the east except at the poles. However, it is hard to determine whether the moon comes from the south-east or the north-east even when the relative positions of the earth and the moon is given. Is there anybody who has a clever method to determine the direction in which the moon rises?

I keep hearing gravity waves described as ripples in space time. Does this suggest that space time is a substance like the discredited notion of the aether? It seems to me that if space time can be said to ripple then a preferred reference frame is suggested by this "ripple" I know I must be off base here but how am I mistaken?

Two cosmological models involving the universe as never having had a beginning and never having an end (eternal), and having no boundaries (infinite) are really interesting me: The Cyclic universe in which the universe has always been (for an infinite amount of time into the past) and always will (for an infinite time into the future) go through cycles of massive expansion and then contraction. Our Big Bang being the last bounce back from the previous contraction and the cosmic microwave background radiation (CMBR) the result of the rapid expansion from the last epoch. The universe of dynamical equilibrium. The universe is not expanding. Redshift has been misund…

A UCSB site says, " However, the Earth is actually moving sideways compared to the center of the Sun at 3 km/second...." Normally "sideways" refers to the forward orbital direction, which is at 29.79 km/s, so I am assuming this is the velocity towards the center of the Sun due to gravity, that is offset by the acceleration in a stable orbit. Is that correct? And how does one calculate that sideways velocity for any planet? Thanks.

Its my contention that the Universe has always been here.

The observatory of Lisbon has published a video of Comet ISON, causing panic. The comet will be visible DURING THE DAY on all the planet on November 29 2013. See the shocking video here: http://third-secret.pro-forum.co.uk/h51-comet-ison ps :enable java-script if you have problems to load the video The 10 km wide core of comet will practically touch the surface of the sun, if the comet survives its orbit will be changed irreversibly, and it will be a Russian roulette for earth. If we believe their calculations ISON WILL BE ON COLLISION COURSE WITH EARTH, WITH IMPACT IN DECEMBER.

Is the Universe infinite or just really, really big?

wouldn't we have to see stars from everywhere during night? Shouldn't the space be so full of light that there is no darkness? Isn't that what they mean by no end to space? Infinite numbers of stars as well? OR do they mean space has no end but there are limited number of stars?

Is folding space (or wormholes) a good method of space travel; that is if it actually exists or is a theory that people except? I remember on a history channel show about space travel, that there was something called "rosen bridges" or wormholes that were everywhere in einstein's theories. Apparently they're tunnels of folded space making the distance very short. Is this even possible? If so wouldnt it take a long time to actually fold the space anyways because in order to fold it, the two points would still have to travel the same long distance just to get to the position where they are now folded? I know this question probably seems too general of a qu…

Stop thinking UFO, I'm looking for more plausible, or perhaps credible answers. I am a boater and am currently practicing using a sextant. I've been observing the night sky far more often over the last two months. On several occasions I see points of light move across the sky slowly. They do not exhibit parallax, the relationship between the apparent altitude, distance and velocity. (for example, The difference between the moon's apparent altitude in the early evening and early morning is appears greater than from an observer located on the surface of the earth because the observer's location moved.) Remember, I'm practicing the use of my sextant. So I can se…

Does anyone think we could discover an asteroid that has a very large quantity of precious metals? Maybe we could find an asteroid that has more gold than the earth has? If we found an asteroid that is so valuable, maybe it could be towed into Earth orbit and the metals could be extracted in nearly zero g and then send to Earth by parachute. What about "rare earth" metals?

Our best scientist claimed that a long time ago. Is this still true?

A star exploded 2 millions years ago. This star is at a distance of 1 million Light Years from us. Can we see the explosion?

SPACE ENDS Space ends, space does not go on forever and ever it ends. The difference between space ending or not ending is if space does not end then space does not have a shape but once you understand that space ends then space can take a shape and that shape can move from one shape to another shape. Yes space ends and moves.

Normal matter clumps under the influence of gravity, but this is only because of other interactions: normal matter particles collide, loose energy and so get closer to each other. And because of the conservation of angular momentum, structures made of normal matter tend to concentrate in more or less disk-like structures (planetary systems, galaxies). Now we learn that most galaxies are supposed to be embedded in a sphere of dark matter. These are spheres, not disks, because dark matter particles, interacting through gravity only, cannot average out their angular momentum, and so do not form a disk-like structure. So far so good. But if we suppose that dark matt…

Do you think that SpaceX and Elon Musk can get us to Mars by 2024?