Saturday, August 13, 2011

Will comet Elenin block the sun on 9/11/11?

No, it won't. (But Ibn Caspi had a nice peshat in whether Elohim was kodesh or chol in last week's parasha.)

Why should we think that it will block the sun? Well, this joker's video, for one:


This based on NASA trajectories. But, does he have it right? This is what they say at NASA:
I've heard about three days of darkness because of Comet Elenin. Will Elenin block out the sun for three days?
“As seen from the Earth, comet Elenin will not cross the sun’s face,” says Yeomans.

But even if it could cross the sun, which it can’t, astrobiologist David Morrison notes that comet Elenin is about 2-3 miles (3-5 km) wide, while the sun is roughly 865,000 miles (1,392,082 km) across.

How could such a small object block the sun which is such a large object? 
Let's think about an eclipse of the sun, which happens when the moon appears between the Earth and the sun. The moon is about 2,500 miles (4,000 km) in diameter, and has the same apparent size as the sun when it is about 250,000 miles (400,000 km) away -- roughly 100 times its own diameter. For a comet with a diameter of about 2-3 miles (3-5 km) to cover the sun it would have to be within 250 miles (400 km), roughly the orbital altitude of the International Space Station. However, as stated above, this comet will come no closer to Earth than 22 million miles. 
In other words, more hyperventilating about something which is simply wrong, by people who don't understand the science.

8 comments:

Navi said...

"Will comet Elenin block the sun on 9/11/11?

No, it won't. (But Ibn Caspi had a nice peshat in whether Elohim was kodesh or chol in last week's parasha.)"

Was that joke for me!?! ;).

Devorah said...

NASA's assertion that Elenin's diameter is 2-3 miles is contrary to all other estimations. If the diameter was only 2-3 miles, there would be nothing to see.... and as we can all see from the pictures taken by the NASA Stereo camera, it's much bigger than that (and that's an understatement).
I remain unconvinced about any of it.

joshwaxman said...

Navi:

wouldn't you have predicted this?

;)

Devorah:
Recall the difference between the coma and the nucleus. To cite Leonid Elenin, "Leonid says nucleus is still probably 3-4 km". And 3 miles = 4.828032 kilometers, and 2 miles = 3.218688 kilometers.

See here in Wikipedia as well.

So Leonid Elenin and NASA are in agreement as to the size of this comet.

Devorah said...

re: the nucleus size of Elenin.


spaceobs comment

"You are right, we can only estimate it."

from Spaceobs.org via Google

joshwaxman said...

precisely.

the exchange was:
"Guilhermecruz: But where are the "estimates of the nucleus size"?

Jadran:
Nobody knows the nucleus size!

spaceobs:
You are right, we can only estimate it."


In other words, it is apparently not possible to directly measure this, unlike, say, other phenomena. However, based on other things which ARE measurable, and what scientists know by studying comets, they can make extremely educated guesses as to what the comet size is. This is not an excuse to then justify ANY comet size one wants, in order to convince people and ourselves that the sky is falling. I would also suppose that certain sizes are ridiculous, and outside the realm of non-ridiculous estimates.

There is a jar of jelly beans. You cannot see all of the beans, but you want to guess how many. You can make a guess based on the volume of the jar, and the average size of the bean. And then 500 jellybeans might be a good estimate. And maybe there are another 100 or 300 more jellybeans, or maybe less. But that does not mean that a BILLION jellybeans is a normal guess that anyone should take seriously.

Navi said...

I don't get so much navu'ah during Bein Hazamanim. Too much time in the sun maybe...I'm waiting for the time when it'll get blocked by this coment!! ;)

Oh by the way, I do have prediction that this blog is getting back on track...Just be careful with the con-artists post...However for $500 I could probably fix the problem!

joshwaxman said...

this reminds me of Heaven's Gate. they also were convinced the (Hale-Bopp) comet was a spaceship,

if elenin is an apple strudel, then it can even taste delicious. but why would you assume elenin is an apple strudel?

Devorah said...

I would like to think it's Kochav Yaakov.

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