# Fermi estimates

Pete Stephenson pete at heypete.com
Fri Nov 14 10:36:22 CET 2014

```On Fri, Nov 14, 2014 at 10:25 AM, Johan Wevers <johanw at vulcan.xs4all.nl> wrote:
> On 14-11-2014 3:15, Robert J. Hansen wrote:
>
>> 10**38 attempts at 10**6 bitflips per attempt equals 10**44 bitflips
>> total.  At carpet-scuffing power, that's about 10**15 joules of energy,
> [...]
>> But to make our brute-forcer 10**30 times faster (so it
>> can run in one year), our brute-forcer also has to release 10**30 times
>> as much heat.
>>
>> I'm not an astrophysicist, but that's the kind of energy levels one
>> normally associates with phrases like "perturb the false vacuum" and
>> "unmake the universe at the speed of light."  Look at the time, I must
>> be going.
>
> Fortunately there's no false vacuum left to perturb. :-)
>
> Anyway, compared to the Sun's output of 3.82*10**26W that's still quite
> large.
>
>> 10 billion is 10**10,
>
> PLEASE don't do that in a FAQ. The definitions of bilion, biljard etc.
> differ wether one uses imperial or SI units, and thuis makes it very
> confusing. For me, a bilion is 10**12. It wouldn't be the first estimate
> that was off by some factors 10**6 due to mixing these up. Better to
> avoid those terms completely.

Minor nitpick: the difference between the "long" and "short" scales
are a bit more involved than just "imperial" vs. "SI".

More details are at https://en.wikipedia.org/wiki/Long_and_short_scales

But yes, avoiding ambiguous words like "billion" is a good idea. Using
notation like 10^9, 10^12, etc. would make things more clear to
readers regardless of what words they use to describe those numbers.

Cheers!
-Pete

--
Pete Stephenson

```