Friday, November 12, 2010

Friday hodgepodge: Cats mastering physics, science cheerleaders, and a galaxy from far-far away

Okay - so in the past I may have accused Billy the Kit of being a tad unfashionable and of coming in the way of blogging. But as it turns out, he knows his physics well. Almost too well (hmm...what is he really up to??). It seems that Billy knows about gravity and inertia (tip from Don):
Writing in the Thursday issue of Science, the four engineers report that the cat’s lapping method depends on its instinctive ability to calculate the point at which gravitational force would overcome inertia and cause the water to fall.
What happens is that the cat darts its tongue, curving the upper side downward so that the tip lightly touches the surface of the water.
The tongue is then pulled upward at high speed, drawing a column of water behind it.
Just at the moment that gravity finally overcomes the rush of the water and starts to pull the column down — snap! The cat’s jaws have closed over the jet of water and swallowed it.
The cat laps four times a second — too fast for the human eye to see anything but a blur — and its tongue moves at a speed of one meter per second.
Being engineers, the cat-lapping team next tested its findings with a machine that mimicked a cat’s tongue, using a glass disk at the end of a piston to serve as the tip. After calculating things like the Froude number and the aspect ratio, they were able to figure out how fast a cat should lap to get the greatest amount of water into its mouth. The cats, it turns out, were way ahead of them — they lap at just that speed.
And this adds just one more reason for the cats to feel superior to humans. By the way, I think the engineers that figured the cat-lapping problem are different than the ones who produced An Engineer's Guide to Cats (and Advanced Cat Yodeling). But who knows?

Okay, so while we are on the subject of science, here are Science Cheerleaders performing at the USA Science & Engineering Festival from last month (tip from Ahmed):

And to conclude, here is the picture of a galaxy from 13.1 billion years ago!! The dot in the red-circle on the left is the center of attention and it goes by the sexy name of UDFy-38135539 (yes, light from this tiny smudge left when the universe was only 600 million years old. At the time there was no Earth, no solar system, and not even the Milky Way. This is how long it has taken for the light to reach us! C'mon - this is so amazingly cool! [oh and yes, almost all the smudges you see in the picture are galaxies...and most are incredibly far-away].

Read more about it here.


Atif Khan said...

Here is a very layman question.

How do we know the light coming from far far galaxy took 13 billion years? It could have been closer so how do we verify? Is it gravitational lensing or red shift that we study to calculate the distance?

Salman Hameed said...


Good question - and you are right, it is the red-shift that tells us about the distance. For nearby objects, there are many different ways of measuring distances - but when it comes down to some of the farthest objects, then redshift is our only resort. Now each chemical element has a unique structure - and that structure produces unique lines that can be identified with telescopes. Hydrogen lines are usually used to measure the redshift. This means that hydrogen lines will be seen at longer wavelengths (redder) than we know them from the laboratory. And this is due to the expansion of the universe - where the farther away a galaxy is, the faster it will be moving away from us. (some demos for expanding universe here)

As far as accuracy is concerned - yes, uncertainties increase the farther away (and fainter) we are looking at. I don't know the specific error-bars here, but it won't change the distance too dramatically.

Atif Khan said...

Thanks for the reply. One more basic question (though I read fewer websites about that but couldn't find simplest answer). What happen to blackholes in longer run when they go out of the matter/gas around. We know there is a blackhole in almost every galaxy out there. How do those blackholes end up?

Salman Hameed said...


The blackholes just become dormant. So for example the black hole at near the center of our own Milky Way is a relatively uneventful black hole. And by that I mean that, at present, it doesn't have much gas/dust around it (there is some - but this is small compared to other galaxy centers). If you completely run out of matter to swallow, black holes will just sit there - just like other dead stars like white dwarfs and neutron stars.

Now I don't want to get side-tracked here...but very small blackholes (if they exist) should evaporate after some time. This is a prediction from Stephen Hawking (these mini-black holes are supposed to give-off radiation - that we now call Hawking radiation - and this should lead to the evaporation of these mini-blackholes after a long period of time (I don't remember the scales for this).

But as far as the regular blackholes are concerned, they will just simply sit there without matter around them.

Hope this answer is in the ballpark range that you were expecting.

Atif Khan said...

Thanks again for simple yet effective explanation. Will keep bothering you with such questions. :)

Powered by Blogger.