### Serious alternate form of the Drake Equation, or graffiti?

• Where I live it is very common to see jackets and T-shirts with familiar yet casually garbled or modified content (example)

I recently spotted what looked a lot like the Drake equation on the back of a motorcycle, shown in the photo.

Here is the equation from Wikipedia (more here):

$$N \ = \ R_* \ f_p \ n_e \ f_l \ f_i \ f_c \ L$$

and here is what I can make out from the photo

$$N \ = \ R_* \ f_p \ n_e \ f_l \ X \ X \ L \ B_X$$

where $$X$$ represents something I can't read, and note that there is a $$B$$ at the end that doesn't appear in the Wikipedia version.

There are also unspecified callouts on the $$N, n_e, B$$ and the first "$$X$$".

The sleeve also contains text which is only partly visible:

``...CATING...TIONS...ALAXY``

Question: Does this representation seem to reflect a serious new or alternate version of the Drake equation, or is it better or more likely characterized as "art" or graffiti?

You can *barely* spot the G on the sleeve...

Don't get to concerned about the Drake Equation, from what I read in the recent past, I forget the source, but Drake never had any intentions for his equation to be the definitive equation. The story goes is he was preparing for a conference or small meeting of peers/friends & he wrote the equation as means of a discussion starter to get people thinking about the issue. It turned out to be a very good equation & no-one has bothered to develop as serious alternative.

The Drake equation isn't much serious itself, isn't?

Wow. I mean, running around in a parka that sports the Drake equation is kinda nerdy. Running around in a Parka with Randall's insightful joke/no joke on it ... that is ... so very ... cool.

@Alchimista: It depends on what you mean by "serious." It's *correct*, insofar as the mathematics and cosmological theory goes, but the main problem is that the error bars for some of the terms are absolutely massive (and others are highly speculative - they cannot be meaningfully measured until after we've already determined whether aliens exist or not). So in practical terms, all it really says is "we might or might not reasonably expect to encounter aliens," which is not particularly helpful information. OTOH, it does make an argument that "the numbers we have don't rule out aliens."

Thanks but I was more on the line of the jacket :) What I am curious now is that here or on physics I've once read a comment point to an interesting logical conclusion that I can't recreate myself. Something like "either we are alone or there is a huge number of aliens out there". Who knows / remember the logic behind this late assertion?

@Kevin it is a model, no models are correct.

"on the back of a motorcycle" I don't understand how or where is there a motorcycle. Isn't it just a person wearing that jacket?

@Džuris ...who is sitting on the back of a motorcycle, which explains why they are so close to the person in front of them and why I didn't have time to ask them nor get a better shot.

one year ago

Given the font, it's xkcd 384, The Drake Equation.

The two $$X$$'s are the other $$f$$ terms from the original Drake equation, while the $$B_S$$ is "amount of bullshit you're willing to buy from Frank Drake"

Wow, @Rob, that was a cool answer. "Given the font" :-)

bingo! even explains the text on the arm, thanks!

@B--rian I've used it one or twice but couldn't recognize it if it bit me. 1, 2

And the sleeve presumably says something like "NUMBER OF COMMUNICATING CIVILIZATIONS IN OUR GALAXY"

On xkcd it is \$B_S\$ not \$B_6\$ I've edited, hope that's okay. (although in the handwritten lettering it is hard to see) See also https://explainxkcd.com/wiki/index.php/384:_The_Drake_Equation

@uhoh , could be that item was once sold on the xkcd store : https://store.xkcd.com