Is There Anybody Out There?

DrZoom writes "The Astronomy Picture of the Day for Jan 9, 2001 is an image sent into space by the Cosmic Call project. This is yet another interesting picture from APOD." Try to figure it out without reading the solution.

Comments

This is the message:

[AftanGustur]

Holy Cow,
this is almost plaintext in the Furth language, just shifted 13 places in the alphabet.

The message reads:

Greetings Furths,
The race of humans has just learnt of your existance, after polluting our own planet, strip-mined it and centuries of brutal war with machines of devastating descruction, we finally found your planet.

Please prepare for our resource probe fleet, due to land in 378 years (203 Furth years).

Looking forward to meeting you.

- The Eartlings

--
Why pay for drugs when you can get Linux for free ?

Seems poor method for "largest prime found"

[samorris]

Unless I missed something, I disagree with their method of denoting the "largest prime found so far"...

They start out by defining a series of symbols and methodology of representing base 10 numbers and equality using a set of (apparently) arbitrary symbols, by displaying the base 1 and base 2 equivalents. This seems fair, though I'm not sure I would have bothered with base 10.

They then include the first 24 prime numbers using the notation introduced above, which seems good.

Then suddenly they jump to including something that the decoded as:

3021377
2 ?1

with the "?" being a symbol that was not included anywhere else on the first page. This caused me quite a bit of confusion... especially the unknown symbol. I was beginning to think they had made a typo, or that it was one of the number symbols garbled. It looked more similar to the number symbols than the equality symbol, so I assumed that it was a number or letter, not a non-number symbol, such as a arithmetic operation or decimal point.

The number itself didn't seem to give any hints either... I was assuming that it was going to be something like pi or the natural log of 10... but the number wasn't familiar.

Turns out they intended this to mean 2**3021377 - 1, which they claim is the largest prime found at the time this was written.

This seems unnecessarily confusing for some poor alien trying to figure it out. In one step, they introduce a new symbol (without any context), indicating substraction, a method of denoting exponents (without introducing exponents), all to describe a number that provides someone trying to decode it no clue as to what the new symbol and new denotation mean.

Did anyone else figure out the "largest prime" on their own? Is there some other clue that I missed?

-- Scott