100,000,000,000

One hundred billion.
One hundred thousand million.

That is a lot, in most contexts. Astronomical even.

Apparently, if you ask nicely, know the right people, you can have it, in cash.
US dollars. Off budget, no questions asked, no supervision, no audits.

What could you do with that?

It is both a lot, and a little.

It is a little bit less than the combined gross worth of the two richest people on the planet.
So a single charity foundation, the very richest, might have that much money, soon.

It is a bit less than the current capitalization of google; but it is more than the gross domestic product of 135 countries, only 48 produce more each year.

It is about $15 per person in the world. Not much.
About $1000 per US household (or $million per Icelandic household! - about 6-7 years of Iceland's GDP; a bit less than 1% of the US GDP).
A stack of that many dollar bills would roughly reach up to geostationary orbit (depends on exact actual thickness, and compression I suppose).

So, what could you do with that. Other than buy 3/4 share in google.

Well, it depends on whether you treat it as capital, or as income.
Heh, like you could sucker anyone into a deal like that every year?!

You could endow the ten or so richest universities in the US, roughly Harvard through Texas A&M!

Or, you could deploy an army of roughly 1-200,000 light infantry, fully equipped and supplied. For a year.

It is, approximately, a postdoc, or two, per minute (depends on your overhead). Not that you could find that many postdocs anywhere...

Conservatively, it could provide an income stream, inflation guaranteed, of 4%. Maybe more in practise.
With some aggressive investment and ramp up of expenses, we might hope for a sustained stream of $5-6 billion income each year.

That is enough to endow the National Science Foundation, in perpetuity. In the first year.
In the second year you could endow NASA's Science Mission Directorate.
In the third year, you could pick up the pieces: NIST, USGS, NOAA, etc
Fourth year we should probably do the DoE Office of Science budget. If anyone were foolish enough to provide such a stream of money for four consecutive years, that is.

After that, you could think about starting to build up an NIH endowment.

Or is that trivial? Maybe it should go to matters of national security: like working on energy independence - research, cross-subsidies for energy efficient building renovation and new construction, encouragement of marginal penetration of renewables as they become marginally cost effective (allowing for external costs of importing energy, like defence, and long term diffuse impacts).
Of course that is crazy, it would take 50-100 years to make major impacts on the US economy at that pace, and who thinks on time scales like that...

Or we could think small: A Kavli Institute could be founded every day, just from the income, not the capital.
Or, you could fund, in perpetuity, including construction and endowment of operational cost, every ground based astronomical facility currently proposed - the GMT, TMT, ELT, SKA, ALMA, LSST.
All of them. Just like that. In a year.

Inconceivable. Of course.
You need people. All the graduate students - they cost about $700million per year. Call it a billion.
Postdocs cost another billion maybe. You also want to get some faculty, but with the remaining 3 billion you would only be able to endow 500-1000 professorships per year (depending on where).
Maybe make it 500 each year, and throw in a few institutes and buildings.
Of course that is just another way of saying the above, that amount of resources could endow an entire sector of pure research in the US, in perpetuity, each and every year.

But this is all just silly, I mean who would hand over that sort of money, year after year, no questions asked?

Inconceivable.