Saturday, July 7, 2007

You`re as cold as ice but............less dense.

Yes,you want to click that picture
Hyperion is a moon of Saturn, and it’s freaky. It’s one of the largest irregular moons in the solar system at 300 km across, and the surface is simply weird. I speculated about it before, and it looks like some of my thoughts have panned out. When the Cassini spacecraft passed by Hyperion, the gravity from the tiny moon deflected the probe just a hair, and from that scientists have been able to find that the density of Hyperion is an astonishing 0.5 times that of water! For comparison, rock is about 2 - 3 times as dense as water, and even ice is 0.9 times water’s density. I think this makes Hyperion the lowest density object yet found in the solar system. So why is it such a puffball? Probably it’s suffered multiple low speed impacts with other bodies. This ruptured the moon, creating cracks and fissures all through it. If it got whacked by something of just the right size and speed, it could have actually broken apart and recoalesced; forming what astronomers call a "rubble pile". It would have so many holes in it that this would account for the extremely low density. Note– I’m still speculating, but it’s hard to imagine what else could have caused this moon to be so lightweight. It’s covered in craters, too. The surface is so porous that when an impact occurs, it actually compresses the surface rather than blowing out material. The moon can absorb the impact better without disturbing the neighboring terrain (and any material ejected tends to escape the feeble gravity of the moon, so that it won’t blanket nearby craters either). On normal moons, an impact is likely to erase several craters as the material is disturbed, but on Hyperion the impactor goes crunch, like punching a piece of Styrofoam. I wonder… when you walk on certain kinds of snow, you can feel it crunch as it compresses underfoot. Would an astronaut on Hyperion feel the same thing?


Friday, July 6, 2007

What is The Universe made of....Dark Matter And Dark Energy??

In the 1920s, Edwin Hubble showed that our universe is constantly expanding and evolving, a finding that eventually shattered the idea that the universe is unchanging and eternal. And in the past few decades, cosmologists have discovered that the ordinary matter that makes up stars and galaxies and people is less than 5% of everything there is. Grappling with this new understanding of the cosmos, scientists face one overriding question: What is the universe made of?
This question arises from years of progressively stranger observations. In the 1960s, astronomers discovered that galaxies spun around too fast for the collective pull of the stars' gravity to keep them from flying apart. Something unseen appears to be keeping the stars from flinging themselves away from the center: unilluminated matter that exerts extra gravitational force. This is dark matter.
Over the years, scientists have spotted some of this dark matter in space; they have seen ghostly clouds of gas with x-ray telescopes, watched the twinkle of distant stars as invisible clumps of matter pass in front of them, and measured the distortion of space and time caused by invisible mass in galaxies. And thanks to observations of the abundances of elements in primordial gas clouds, physicists have concluded that only 10% of ordinary matter is visible to telescopes.
But even multiplying all the visible "ordinary" matter by 10 doesn't come close to accounting for how the universe is structured. When astronomers look up in the heavens with powerful telescopes, they see a lumpy cosmos. Galaxies don't dot the skies uniformly; they cluster together in thin tendrils and filaments that twine among vast voids. Just as there isn't enough visible matter to keep galaxies spinning at the right speed, there isn't enough ordinary matter to account for this lumpiness. Cosmologists now conclude that the gravitational forces exerted by another form of dark matter, made of an as-yet-undiscovered type of particle, must be sculpting these vast cosmic structures. They estimate that this exotic dark matter makes up about 25% of the stuff in the universe--five times as much as ordinary matter.But even this mysterious entity pales by comparison to another mystery: dark energy. In the late 1990s, scientists examining distant supernovae discovered that the universe is expanding faster and faster, instead of slowing down as the laws of physics would imply. Is there some sort of antigravity force blowing the universe up? All signs point to yes. Independent measurements of a variety of phenomena--cosmic background radiation, element abundances, galaxy clustering, gravitational lensing, gas cloud properties--all converge on a consistent, but bizarre, picture of the cosmos. Ordinary matter and exotic, unknown particles together make up only about 30% of the stuff in the universe; the rest is this mysterious anti-gravity force known as dark energy. What is exotic dark matter? Scientists have some ideas, and with luck, a dark-matter trap buried deep underground or a high-energy atom smasher will discover a new type of particle within the next decade. And finally, what is dark energy? This question, which wouldn't even have been asked a decade ago, seems to transcend known physics more than any other phenomenon yet observed. Ever-better measurements of supernovae and cosmic background radiation as well as planned observations of gravitational lensing will yield information about dark energy's "equation of state"--essentially a measure of how squishy the substance is. But at the moment, the nature of dark energy is arguably the murkiest question in physics--and the one that, when answered, may shed the most light.



Tuesday, July 3, 2007

Thats Me


Thats me... ABHINAV DUGGAL. The mind behind this blog. I am an 18 yr old from a small town called jalandhar and hv always been fascinated by the way science clicks which inspired me for this creation. I ll be really obliged to recieve ur suggestions.