[0] - https://www.nasa.gov/mission_pages/station/expeditions/exped...
I just realized I have no real concept of how many stars there even are within, say, a 100 light year radius of our sun (I guess that's a more realistic thing to find out than the number of planets).
A quick search provided some estimates and they're kinda... disappointingly low, at around 20000 stars. That's a number where some "1% of 1% of 1%" kinda filter quickly ends up in a scenario where a planet fitting all our criteria might simply never be in reach. For something more "realistic" (I know, heh!) like 20 light years, there are only 150 solar systems. I've seen different numbers and have no idea how they're calculated but for the usual astronomic scales which quickly go into "billions" territory, it seems we're kinda stuck with a comparably small list of candidates.
It might cheer you up to think that's the only reason the human race happens to be the one in our neighborhood that made it into space, without being stepped on by an Old One.
It could well be the universe is filled with life, but the dominant mode is underground chemo/radiotrophic microbes on planets without stars.
The implications for the Drake equation are pretty big.
Rockets without any promise of ever being able to break orbit are good for what, war? Would you keep developing them? Would you give up dreams of the stars? Would you look for intelligent life you couldn't ever possibly meet?
Nuclear rockets don't seem to be very hard. They're somewhat dangerous if they explode, but they aren't very hard. Fairly solid prototypes were built decades ago and there's little to suggest they couldn't have been made production-grade [1]. We'd have them now if we didn't find the risk/reward to be too highly slanted to the "risk". Other species and other ecosystems may come to different conclusions, e.g., an ecosystem already more exposed to radiation and evolved to deal with much higher levels of it may judge it much less "risk" for some radionuclides to be scattered across the landscape in case of failure.
What can be more of a problem is being in a place where you have no obvious access to technology at all. However smart our cetacean buddies may be, it is not clear even at this point in the 21st century what path to technology they could possibly have from their starting point. "The literature", a.k.a. "science fiction" has hypothesized breeding programs to develop various tools, but it's still not entirely clear how they'd get from "breeding useful jellyfish" to, well, anything like technology as we know it. It's possible we're just not solving this problem because we don't have to, maybe there's some easy path with the right development path, but it's still not clear what that would be.
[1]: One of my markers for "the space age is truly here" is when we lift a nuclear rocket into space, sans fuel, and fuel it with space-sourced radionuclides. Earth-bound citizens will still complain, because "NUCLEAR BAD!", but their complaints will be ignorable at that point.
Is there any combination of tricks that can realistically push the envelope there? For example can we use a space elevator to start higher/faster (or, I don't know, balloons? a catapult or railgun or something?), laser power delivery from the ground, so we don't have to carry all the fuel, and an orbiting way-station for refueling, etc.?
From the reference article:
> Travelling from the surface of Earth to Earth orbit is one of the most energy intensive steps of going anywhere else. This first step, about 400 kilometers away from Earth, requires half of the total energy needed to go to the surface of Mars.
Which means that if we use something like a balloon/blimp in the first stage, it would be a lot more energy efficient.
Anyone knows why it's not done that way already?
Also, whatever happened with the plane+rocket Virgin Galactic project?
Realistically, but not plausibly unless its an emergency, Thermonuclear bombs:
These methods will all help with the first 1% of your problem, getting off of the earth.
But you need so many orders of magnitude more energy to reach the kinds of velocity needed to get to another star in less than a million years. It's just an unfathomable amount of energy per kg. Put simply: if you can get to another star, getting off the planet is nothing.
https://en.wikipedia.org/wiki/Interstellar_travel#Wait_calcu...
Maybe it implies that every interstellar mission is just an in-flight rescue mission.
Cosmology is so cool... too bad we do not have time for that: we cannot even cure the common cold!
[1]: https://januscosmologicalmodel.com/pdf/2014-ModPhysLettA.pdf Cosmological bimetric model with interacting positive andnegative masses and two different speeds of light,in agreement with the observed acceleration of the Universe
It sounds like you get anti-gravity for free along the way to getting superluminal travel.
Assuming chemical propulsion and no refuelling at the destination.
"If the radius of our planet were larger, there could be a point at which an Earth escaping rocket could not be built. <snip> That radius would be about 9680 kilometers (Earth is 6670 km). If our planet was 50% larger in diameter, we would not be able to venture into space, at least using rockets for transport."
So we have an "or" assumption, not "and", with an additional and assumption about refuelling. That's how I read it.
At our current max speed (692,000 km/hr, stated max speed of Parker Space Probe), it would take about 173,000 years to get to that planet.
We could instead choose to Wait and grow our tech. By picking a constant annual growth rate and then doing some calculus to find the minimum, we can calculate the shortest possible time it will take for us to arrive there.
One common recommendation for annual energy growth rate is 1.4%, and then taking the square root to get velocity growth rate since velocity has a square root relationship with energy.
By plugging that in, we can minimize our time by growing for 1020 years, and then traveling for 144 years, for a total time-from-now at 1164 years.
Another paper[2] estimated an annual velocity growth rate of 4.72%, quite a bit faster. Plugging that in, it says we should wait 195 years for a travel time of about 21 years, or 216 years overall. This is of course incorrect since it assumes being able to travel FTL. So if you instead look at how long it would take to get to light speed travel at that rate, you're looking about about 159 years, or arriving at the planet at a time-from-now of about 270 years.
Of course, if you're seeking to minimize time-from-now from the perspective of a traveler, maybe you'd take off sooner. Kind of a tradeoff - less time to wait for the traveler, more time to wait for the home planet. I haven't figured out that part of the math yet.
[1] https://ipfs.io/ipfs/QmXoypizjW3WknFiJnKLwHCnL72vedxjQkDDP1m... [2] https://arxiv.org/abs/1705.01481
Energy growth is due to end sooner or later.
First, in the real world, any long term exponential growth is actually the upward branch of an S (that plateau at some point) or of a bell curve (that falls down after a peak).
Second, with such an energy growth rate we'll boil the ocean from heat dissipation long before we reach the stars.
I always thought that was a very well thought out aspect of The Expanse: spend half the trip accelerating, then flip the ship around and spend the other half slowing down (aka accelerating in the opposite direction).
> I always thought that was a very well thought out aspect of The Expanse: spend half the trip accelerating, then flip the ship around and spend the other half slowing down (aka accelerating in the opposite direction).
With current technology you would not do this, since that means using extra fuel that weighs a lot and thus increases the force required for the same amount of acceleration as you'd get with less fuel and less burn.
Of course that changes drastically if the fuel required for more acceleration (and its container) is very light-weight. I would assume fusion or fission based thrusters would be better in this regard, however I think currently those produce very little acceleration in a vacuum compared to combustion thrusters.
Going later to optimize for time is one aspect of deciding how to spread throughout the galaxy. Another question might ask, which is the most risk reducing strategy? And the answer might be completely different.
I take your point though - hypergrowth cannot be sustained - and estimating that exponent is fairly valueless if volatility is too high. This is all just math fun that won't be valuable if we bump along for hundreds of years and then all of sudden make a massive discovery.
https://en.wikipedia.org/wiki/Kinetic_energy#Relativistic_ki...
Most scenarios I've explored - low velocity growth rate, nearby planets/stars - the Wait Calculation tells you to stop researching and start launching long before your tech gets to significant fractions of light speed.
Cosmology involves distances that are so great that it seems like it's pouring a whole bunch of smart people's efforts down the drain in an ultimately futile waste of brain power that will never amount to anything much at all. Besides, when we get faster than light travel we can just pick up exoplanet research where we left off and it will actually be practical and probably far more efficient with the computers and such we will have developed by then.
I think it depends on what one wants to get out of the research. If the goal is a commercially realizable product on a shortish time horizon (say < 50 years), then cosmology may not be the best approach. But the justification for cosmology and much of astrophysics is typically that it is a probe of fundamental science and the acquisition of knowledge for its own sake. In which case whether we can ever travel to other planets or galaxies is moot, since it's the physical understanding and knowledge that's the goal.
Many before me have used the example of relativity, which when proposed, seemed to have little practical value. But GPS wouldn't work without relativistic corrections. 100-120 years ago one could've made a similar statement about fundamental physics and work on relativity. But if we'd abandoned it because of a lack of immediate relevance then we wouldn't have workable GPS today. The benefits of fundamental research (in many areas, not just astrophysics) are often quite difficult to forecast.
FTL requires numerous things to be true about our universe, that all signs say are not.
I don't think measuring progress is tivial enough to make that assumption. It's also unfair to blame a fascination with deep space for any slower progress, things are more complicated than that.
Getting humans onto anther planet asap is one of the most important things one can pursuit for humanity. The earth is a giant single point of failure
if we get FTL, we'll be able to pick up that research before we left off ...
Well, at least they're not making people click ads ...
or observe civilizations broadcasting knowledge in a loop: motivation? perhaps the faster they can get others up to speed, the faster others might contribute knowledge back which may some day save their civilization.
Just because we build more power plants or sell more tractors doesn't imply a corresponding improvement in spacecraft technology.
The Wait Calculation seems to make even less sense than the Drake Equation - which is at least correct in theory even if the actual variables have so much uncertainty it is useless.
This is your mistake. It's an approximation that works well only at low speeds.
Where does this come from? Does it even hold water when compared to past data? Looking at some Wikipedia data for the past 20-30 years, it seems that the increase in speeds is much higher:
https://en.wikipedia.org/wiki/List_of_vehicle_speed_records#...
Given the total journey would be ~40,000 days the 230 days of acceleration probably isn't going to impact things too much. Even if you brought it back to 1g acceleration, it's still only around 700days out of 40,000.
That'd be fun to add, though. I'm not really sure what human-safe acceleration is - people here assume it's in the 1g-3g range. (That seems like a lot to me though, particularly for a long period of time - I think anything more than a fraction of g would be wildly uncomfortable.)
1. This planet probably doesn’t have a solid surface
2. Being in the “habitable zone” doesn’t mean a planet is habitable
3. The detection is of water molecules, chances are the water only exists as vapour in the atmosphere of this small gas giant.
4. If you ask 10 astronomers about this you will get 11 opinions
She said to me "Yeah sure, but who cares? What it really tells us it's that it's possible to do this in linear time at all. That might not have been true, and now we know we might find a faster linear algorithm."
(All of this is paraphrased because it's been over a decade).
The point is: we have found another planet with water. We now know this is possible! We know that it's probably not super uncommon (or else we wouldn't have found one so soon). That's what's amazing about this.
So what if it's not perfect, it's a great discovery!
Whether it's common is still unclear, given that so far there's a big bias towards detecting large exoplanets that are close to the host star.
True. Being a spooky near twin of Earth isn't necessarily enough.
The air inside popcorn factories is basically identical to the Earth's atmosphere, but breathing in diacetyl, a butter flavor you'll find in that air, will kill you a few months or years later.
Popcorn lung really undermined my naive view that we would one day be able to run a scan or a sniff test on a planet and then just breathe without assistance.
https://en.wikipedia.org/wiki/Bronchiolitis_obliterans
You have an identical twin to Earth with slightly different dust composition and it could shred our lungs. We are highly, highly tuned to our home.
Which doesn't mean we can't go anywhere. But it won't just be advances in travel speed that will get us off world. It may also require drastic modifications to the human organism.
Related question:
Does "habitable" mean "habitable for humans"? I thought it didn't, but after reading some dictionary definitions, i believe it does. On the other hand looking at the planetary habitability wikipedia page it's clear that it means "life-friendly". No wonder many people are confused.
Of course a planet with 8-9 times the mass of earth is not very friendly for humans, ignoring all the other possible issues (pressure, chemical composition, radiation, flares etc)
So, there could be "super-earths" with life similar to ours, even intelligent, and they would never be able to participate in a space-faring society.
It’s almost entirely arbitrary, but roughly based on luminosity of the star.
I'm not entirely clear on the deciding factors, but it's probably mostly density.
Mars has a leaky atmosphere - sure it's a real fixer upper. But we have a better chance of fixing it, or even correcting the orbit of our planet so that in 500 million years it's still livable.
I'm 99% sure that Earth is inhabitable right now... perhaps you meant "uninhabitable"?
Genuinely wondering how you got that number. I'm reading 111 light years in the article, wouldn't that simply be 111 years of travel time, at the speed of light? Am I missing something?
Once we solve mind uploading (assuming that it's possible), we can send a blob of grey goo on a solar sail at a very high acceleration to another solar system. It can shed half of the sail and bounce the laser back to decelerate.
The grey goo would go and convert part of asteroid or something to computronium, and then we'd upload a bunch of humans over to the other solar system.
This is all presumptive of the preferences of individual humans. It may be that the giant extrasolar Earth-type planets could be dismantled and rebuilt into smaller Earths located at various Lagrange points.
They could even clone them back on the other end and install the preexisting mind, basically teleportation.
Obviously its going to be a one way trip. And it would require a generational ship.
So could we build a ship that held 12 people initially, 6 couples, all who were allowed to have 2 children, so 24 people max, and could we load it with enough supplies to last over 100 years?
Even if the group that eventually arrived had no way to sustain life, and they just went there for a quick swim before dying... is it possible?
Spoiler: it's not
Any type of observation was only a period Of time and any type of life used to be there, but may not be there presently?
Discoveries like this improve our understanding of likelihood of extraterrestrial life, which has direct Earthly implications. It also enables better estimates and searches for planets that are closer, say ~4 to 20 lightyears away, for those super interested in the traveling & communicating possibilities.
‘A giant waterworld that is wet to its core has been spotted in orbit around a dim but not too distant star’
With oceans 9000 miles deep (15000 km). For context the Earth’s diameter is 7900 miles (12700 km).
The imagination really does boggle at the thought. I think science fiction is going to have a hard time keeping up with the incredible science fact we are observing in our lifetimes.
https://www.theguardian.com/science/2009/dec/16/waterworld-p...
They were going to the Barnard Star, but it had binary planets where one was all water.
Good book (if I recall)..
All my life I wait for the moment we will find life
I just afraid if it will really happen from everyone reactins
