Radrook

Astronomy has always fascinated me. In fact, I have been a regular participant in various astronmy forums answering questions, teaching and learning from others. So if indeed there are those of kindred minds here, well, let's discuss whatever you wish. If not, then I'll just post interesting news and data now and then just to keep the thread alive and useful. That I promise : )

Radrook

Erosion on Titan and appearance of its surface.

Erosion contributes significantly to Titan's topography. That's what makes it's surface young. The term "young" in geology simply means that the surface has been subjected to "recent erosion" via impact cratering, wind, rain, volcanic flows, etcetera.








Y
young
When used to describe a planetary surface, "young" means that the visible features are of relatively recent origin, i.e. that older features have been destroyed by erosion or lava flows. Young surfaces exhibit few impact craters and are typically varied and complex; in contrast, an "old" surface is one that has changed relatively little over geologic time. The surfaces of Earth and Io are young; the surfaces of Mercury and Callisto are old.
http://www.solarviews.com/eng/terms.htm

Here are some suggested reasons for fewer visible signs of crater-impacts on Titan.

1. Erosion via liquid methane rain and the flows.
2. Wind, and wind-driven sand [BTW: Titan's dunes are made of solid hydrocarbons that that turn to grains after raining down from the atmosphere..]
3. Cryovolcanism? [as yet unconfirmed]
4. Coverage of craters by wind-driven sand dunes.
5. Thick atmosphere shielding the surface from larger impacts.


Scientists Puzzled by Titan's Missing Craters
http://www.bibliotecapleyades.net/lu...ar_titan02.htm

A New Crater for Titan
August 29, 2011
.... Titan's dense atmosphere burns up the smaller impacting bodies before they can reach the surface. The craters that do form are often hard to recognize or disappear entirely as they are eroded over time by geological processes such as the wind-driven motion of sand and, possibly, icy volcanism....
Credit: NASA/JPL-Caltech

http://saturn.jpl.nasa.gov/photos/im...m?imageId=4354

Far too few
http://www.bibliotecapleyades.net/lu...ar_titan02.htm


Also, because the surface was detected by the Cassini Orbiter as shifting nineteen miles in three years, Titan's crust is thought to be resting on liquid. The swift shifting is said to be aided by the wind-pressure against Titan's mountains much as a sail on a ship.







The Moon's Entire Crust May Slide Over Subsurface Ocean
Titan's surface was shifting by 0.36 degrees per year. For there to be this rapid of a shift in the position of Titan's surface requires the surface to be able to move freely about the rest of the moon, sliding around atop a liquid interior ocean.

http://planetary.org/news/2008/0320_...Mountains.html









Signs of Hidden Ocean Underneath Titan's Crust
Slippage in Titan's rotation suggests water between its surface and core—and a higher likelihood of ancient life on Saturn's biggest moon


Last year, researchers reported that radar mapping of Titan by the Cassini spacecraft had found a peculiar shift in landmarks on the moon's surface of up to 19 miles (30 kilometers) between October 2004 and May 2007.


http://www.scientificamerican.com/ar...r-titans-crust

Radrook

Developing a nose bleed? Tilt head backward and apply cold compresses.

Radrook

Re: Is it true that the earth's rotation is slowing down? How it is happening? #7


We can compare the situation between earth and our moon to a merry go round and a rider on a horse circling it in the same direction on a track.

Let's say that the merry go round is earth and the horse and rider are the moon.

The rider has a lasso = gravity

If he lassoes one of the merry go round's horses he will gain speed.
Conversely the merry go round will experience drag and will lose velocity.

Another way that earth rotation is slowed is via the friction of currents on the ocean floor which have a braking effect..

Radrook

Re: Real pictures of black hole eating a star?
Last edited by Radrook; Feb11-12 at 01:07 AM.. #18



Radrook


Posts: 272


It isn't inherently always impossible to see a star being ripped apart in visible light since there is nothing that prevents such visible light from reaching us during that process. That is unless distance makes the event too dim or dust intervenes. But otherwise a person nearby would see the whole thing unraveling in all its glory in VS as well.





First time ever: scientists see jets as black hole swallows a star

They suggest that the lack of signal in the visible spectrum is probably a product of some dust sitting between us and Sw 1644+57, which absorbed the event's output in that area of the spectrum....
http://arstechnica.com/science/news/...ows-a-star.ars

Please note that it is essential to separate accretion disk radiation and the star itself as it is being cannibalized. They are two totally temporally different and qualitatively separate phenomenon. One involves radiation produced by the star's material accelerated around the BH and producing GR and X-Ray radiation .The other observable phenomenon involves the star itself as it gradually loses material and luminosity until it final disappears and is no longer visible in any LS.

As long as the star itself hasn't gone beyond the BHEH its light will reach us. If it doesn't reach us or reaches us too faintly during the process it isn't because of BH gravity prevents it or because the visible light spectrum is being nullified during the event. It is because of extreme distance or intervening dust as the article below points out .

Here are images in visible light after the X-rays were detected.




On the left is his observation on April 1, and on the right on April 4. The position of GRB 110328A is circled. As you can see, it was pretty faint. It has apparently faded somewhat over the three day interval — which is expected; the initial event (a star getting torn apart! I can’t get over that!) released a huge flash of energy which faded over time. It’s hard to see in the two images because the burst looks about the same brightness, but the second observation had a longer exposure time (you can see fainter stars in it), so the source did fade.
http://blogs.discovermagazine.com/ba...-a-black-hole/





Electromagnetic Spectrum
Radio waves, visible light, X-rays, and all the other parts of the electromagnetic spectrum are fundamentally the same thing. They are all electromagnetic radiation.
http://imagine.gsfc.nasa.gov/docs/sc...mspectrum.html

.

Radrook

Re: How do I find the age of a star?
Last edited by Radrook; Feb17-12 at 04:34 AM.. #10



Radrook


Posts: 272


This method [a new one presently limited to certain types of stars] is based on how fast the star is spinning.

Gyrochronology
http://www.google.com/search?sourcei...W_enUS378US378

A new method is helping scientists assess the ages of isolated stars, including all stars known to have planets....A star's rotation slows with time, research shows, giving scientists a clock to understand its age.


The research is published in May 20 issue of The Astrophysical Journal Letters.

http://news.discovery.com/space/star...et-110523.html

Radrook

Re: Hypothetical way to travel faster than light, but not technically exceed lightspe
Last edited by Radrook; Feb6-12 at 06:52 PM.. #3



Radrook


Posts: 273








Question:

Would it be possible to create a controlled expansion of space behind a vehicle along a single path, like a corridor, that would change your position in space technically faster than light?

Answer:

I gather you mean the warp drive or Alcubierre drive involving space itself transporting the ship along with it at FTL speed to a predetermined destination. Well, it would be nice if it were as easy as the Star Trek episodes make it seem. Unfortunately the obstacles that such a method of travel would have to overcome are so daunting as to make it seem totally impossible not only with current technology but with any technology we can presently realistically envision.

For example one method requires preparing the trajectory for the ship beforehand. Obviously such preparation demands FTL capabilities. Other problems involve the inability of the crew to control the ship. Still others involve the application of mind-boggling impossible energies required to manipulate the fabric of space that way. The article below discusses these and others.


Alcubierre drive
http://en.wikipedia.org/wiki/Alcubierre_drive


The Glen research center site has an article about what it claims to be the general scientifically-derived consensus on the FTL idea based on warp drive.

Glen Research Center

Status of "Warp Drive"

"Warp Drives", "Hyperspace Drives", or any other term for Faster-than-light travel is at the level of speculation, with some facets edging into the realm of science. We are at the point where we know what we do know and know what we don’t, but do not know for sure if faster than light travel is possible.

The bad news is that the bulk of scientific knowledge that we have accumulated to date concludes that faster than light travel is impossible.
http://www.nasa.gov/centers/glenn/te.../warpstat.html

Radrook

Re: What is the expansion of the universe
Last edited by Radrook; Feb11-12 at 08:15 AM.. #3



Radrook


Posts: 273
A teacher told us that it is just the space between the galaxies that is expanding,


Reply:


Your teacher should have qualified her statement. It's the voids that separate galactic superclusters which are arranged as filaments and walls surrounding these voids that is expanding. The space within supereclusters themeselves or regular clusters, or solar systems or anywhere else where gravity predominates isn't expanding. The effect is that the supercluster fillaments are becoming more distant from one another regardless of their individual proper motions. The effect does not appear to be a crushing one.

Supervoids and superclusters point to dark energy
BY DR EMILY BALDWIN

The nature of dark energy is one of the biggest puzzles of modern science, but it is thought to work against the tendency of gravity to pull galaxies together, causing the Universe’s expansion to speed up. Impressively, astronomers from the University of Hawaii Institute for Astronomy were able to catch this elusive dark energy in action as it stretches out the largest known structures in the Universe: supervoids and superclusters, vast regions of space half a billion light years across, containing either a deficit or surplus of galaxies, brought about by density fluctuations in the early Universe.


http://www.astronomynow.com/080730Su...arkenergy.html

About the expansion itself generating a logical paradox, you are right, it does. Especially if we dogmatically insist that the universe is infinitely large which means it is boundless. Which creates the paradox can something which is boundless or infinite in size actually increase? If it indeed increases then it wasn't infinite to begin with because to increase means to exceed former boundaries. If the universe is finite then that leaves room for an increase into something and permits such theories as the multiunivers and the brane theories to be viable.


Nonsense?
To assume that whatever is mathematically representable provides indisputable proof of its existence in nature constitutes a conclusion based on a false premise. There are presently many theories involving dimensions as part of the String Theory expressed mathematically and their existence via the scientific method is as yet improvable and might well turn out to be just as bogus as other once-popular mathematically viable ideas have.

The problem arises when we confuse potential infnity, as in a number line, with boundless tansfinite spatial infinity. Potential infinity allows for the addition of more space just as a number line allows it. However, transfinite infinity does not. http://en.wikipedia.org/wiki/Actual_infinity

Here are some links in agreememt with this conclusion:

Aristotle also distinguished between actual and potential infinities. An actual infinity is something which is completed and definite and consists of infinitely many elements, and according to Aristotle, a paradoxical idea, both in theory and in nature.
http://en.wikipedia.org/wiki/Actual_infinity

Can anything 'real' be infinite?
http://www.thekeyboard.org.uk/What%20is%20infinity.htm

Radrook

Bunch of oversensitive undereducated post menapausal territorial old farts like sandm and her moronic followers is what screws up ths whle place.