History has shown that the Space Race in the 20th century between US and Soviets has been high enough to motivate US to increase federal NASA budget to [about 4%] of the federal budget 2, compared to below 1% recent decades. Still, in 2018 this 1% of federal budget brings up $20b, nearly 4 times more than ESA has got.
So let's explore which events could lead governments to boost funding for space exploration (US seems to me to be a good example but feel free to substitute any other country of your preference).
Now if I exclude scenario descriptions for emergency cases known to me where:
- there is just not enough time for long-term projects like in Seveneves
- or enough time combined with obvious invasion danger like in Rememberance of Earth's Past,
then this narrows the scenario to something like in Blind Lake, where people of Earth are enabled to observe alien life in great detail.
Surprisingly enough, this is not technically impossible even today, so in some not very far future (but at least some decades, I guess) we might indeed have some observations of what happens on the surface of (Earth-like) exoplanets.
Nevertheless, we have seen that Earthlings might need some monetary motivation and tangible results for things they do (no information about other sapient species regarding this question is currently avaialble).
So the following reality check: how high and under what conditions (i.e. what is to observe on an exoplanet's surface) could (say U.S.) federal budget for space exploration become in face of new knowledge about aliens and what they actually do beyond just existing? (possibly, we can't consider too low tech aliens but who knows).
To simplify - when would they say, again 4%, or 10%, or 25%? (to compare, federal spendings in US on military were 54% in 2015; imagine people of Earth would at least partly unite after knowing that we are not alone, so you could cut these new spendings from military)
More details on referenced books:
- Seveneves: Moon scatters into pieces which will extinct humanity in 2 years timeframe
- Rememberance of Earth's Past (trilogy, first book is "The Three Body Problem") - an alien civilization declares humanity war, their spaceships are to arrive in 400 years
- Blind Lake - advanced technology allows for TV-like format observation of alien life
- Road not taken - a short story where alien invaders appear to have no superior technology over Earhtlings than hyperdrive (which appears to be trivial to copy)