still, they could be detectable, radio signals and stuff like that, afaik we have sent radio signals (not just inadvertently) from the ground
So.. Dark Forest strike? paint them?
I watched it, interesting video and accessible approach to the topic.
I couldn’t help but walk away from the video thinking about how many kids enter STEM/non-social science degrees at college and get to fully fledged adulthood before the realisation that social science is pretty fucking important and touches every aspect of our lives.
I probably have a chip on my shoulder because of how much everyone shits on social science as a low paid/dead end career but it’s upsetting an astrophysicists opinions about social science seems to be taken more seriously than an actual social scientist (this is more based on her previous video about gravity being a social construct but a lot of social science constructs are weaved into the Fermi paradox video as well).
The tallest people on that planet
If the planet is massive enough, getting to orbit becomes a real challenge because fuel consumption scales roughly exponentially with the mass of a planet (delta-v formula, rocket equation).
This leads to an almost sharp cut-off for the maximum mass that a planet can have so that a rocket which utilizes chemical fuel (e.g. methane+oxygen) can still reach orbit successfully. This maximum mass is roughly 10^26 kg.
For reference: Earth's mass is around 6*10^24 kg.
While other propulsion types exist, such as nuclear + ion drive, these propulsion types are significantly more complicated.
Interestingly, if a planet is too small, it cannot hold an atmosphere. There is a surprisingly sharp cut-off minimum mass for this as well, at roughly 10^21 kg.
I propose going to the south pole and just letting go??
We really are in the Goldilocks Zone, aren't we?
Well, yes. In the middle of the goldilocks zone that is based on the environment we are adapted to is where you would expect to find us :p
Anthropic principle ftw
Haha fair point.
If anything, it'd be a bias towards spaceplane designs over straight up rockets. As long as the atmospheric density relative to the gravity supports it, offloading some of the acceleration to high atmospheric flight using ram/scramjets can massively reduce the launch vehicle mass (don't need to carry oxidisers for the flight stage).
That being said, it also would be a bias against high orbits and space exploration in general; safe re-entry is tricky enough on earth.
Imagine all the room for activities! (Trench warfare)
Imagine a terrestrial planet that is Earthlike in all respects, but it simply has more persistent cloud cover, such that seeing an open cloudless sky is miraculously unlikely, as unlikely as humans directly witnessing an asteroid impact.
No ground based astronomy.
No technological discoveries or culture that derives from ground based astronomy.
No celestial navigation on the ground.
Very different / stunted / more difficult cartography.
Technological civilization is capable of emerging, but it would not be able to well understand anything beyond the terra firma, not untill it generated aircraft capable of breaching the cloud cover layer, and then developed airborne observatories.
"Nightfall", by Arthur C. Clarke is a short story based on this premise.
Except in the story it's a complex multiple-star solar system that makes it very rare for all suns to set at once.
Edit: It's actually Isaac Asimov.
Well, the church threw us back about a millenia, so what's a few centuries.
According to Wikipedia this planet has an estimated surface gravity of 12.43 m/s^2 with a margin of error of about 2 m/s^2. That's only up to 50% higher than Earth's 9.8 m/s^2 (on the high end of the error margin) so it probably would be possible to get into orbit.
That said we don't actually know much about it for sure. We don't know if it's a terrestrial planet for example. It could be composed mostly of gases and liquids like Neptune.
(Not a rocket scientist or mathematician, but I spent 100s of hours playing KSP RP-1)
Just doing some estimates using data from the wikipedia page:
The dV (delta-V) needed to get into low Earth orbit is around 9.4km/s.
The dV for K2-18b might be around 19km/s, more than double that of Earth's.
It's practically impossible I think, you would need such a massive launch vehicle. For double the dV, you would need exponentially more fuel assuming current rocketry tech (fuel+oxidizer tanks and engines). There wouldn't be any single-stage or two-stage rockets that could do this. With a 3 or 4 stage rocket maybe? But you would be sending nearly 100% fuel off the launchpad with virtually zero payload.
Check out the "tyranny of the rocket equation". The more propellant you need to lift heavier rockets, the more propellant you need to lift that extra propellant and so on and so on.
I tried to factor in:
spoiler
The density of K2-18b is about 2.67+0.52/−0.47 g/cm3—intermediate between that of Earth and Neptune—implying that the planet has a hydrogen-rich envelope. [...] Atmosphere makes up at most 6.2% of the planet's mass
Since the atmosphere is so thick and takes up a lot of mass, I've picked 500km as the low orbit altitude (comparing to Earth's ~100km Karman line, it makes you appreciate how thin our atmosphere is ).
Rotational assist - I'm assuming it's tidally locked since it orbits so closely to its star (33 day years), and so you wouldn't get the assist from rotation like you do on Earth:
The planet is most likely tidally locked to the star, although considering its orbital eccentricity, a spin-orbit resonance like Mercury is also possible.
Kerbal Space Program is such an amazing game that secretly teaches you physics.
I'm stealing this
Nice. It's from XKCD if you want the source.
game that secretly teaches you physics.
those are the best!
We make a mistake by assuming that life forms would likely be at the same scale as us. Larger planets would likely develop life forms appropriate for those planets instead of appropriate for ours.
Uh... being smaller or larger does not really change the laws of physics... if the gravity is too high, no fuel has enough energy density to escape the gravity of the celestial body.
If you need 150kg of fuel to get 100kg worth of matter to escape velocity it does not matter how much fuel you have. It will not ever be enough to leave.
Most of the life we see on Earth isn't even our size!
Life on earth scales from microscopic bacteria all the way up funguses that have an underground network covering thousands of acres.
The chances of us finding life on another planet is pretty slim, the chance of that life looking like us is astronomically miniscule.
Also, of all the millions of species that have evolved on Earth, only one has developed civilisation. We're an anomaly, not an inevitability. Other planets could be teeming with life, but it's happy to just chill in the forest/ocean/wherever.
Jokes on us: Because of the gravity issue, alien life on such planets jumps right to stargate technology.
"They spent almost a thousand years fooling around with rockets!"
I wonder at what point it is worth building a ~~space elevator~~ space pyramid.
Just keep stacking rocks until you're a few dozen miles away from the edge of space.
yeah this idea actually exists, i think it's called a mass driver, which is essentially a very high-speed rail gun, that shoots objects directly into orbit without the object having to have much of a propulsion system itself.
This obviously only works if the object isn't slowed down by atmosphere, which means you'll have to launch it from high enough up.
This is where the pyramid comes in. You can, of course, also utilize naturally occurring mountains, if your planet has any. These mountains would have to be rather high, though. Like on earth, maybe 100 km. The highest we have are 8 km.
A place for majestic STEMLORD peacocking, as well as memes about the realities of working in a lab.
Rules
This is a science community. We use the Dawkins definition of meme.
