While it's possible for conditions for life to emerge or sustain itself to be present beyond the habitable zone (e.g. there's likely a subsurface ocean orbiting the farthest plant from the Sun on Triton), afawk it is more probable that life forms in the habitable zone. That is the only one we have a data point for.
For many reasons.
1 - it might be very unique itself
2 - it might be very close to us
3 - it might be orbiting a very interesting star, a star type we didn't expect to have that planet type or so many planets, or so close, or so far, etc
4 - the more exoplanets we discover the more we learn how star systems come to be. the more we know how rare ours is, how it might have formed, etc. It helps us answer age old questions.
Next year there is a plan to send a space telescope to L2 with the main objective being to search for Earth-like planets around Sun-like stars in the habitable zone.
Like Kepler and TESS telescopes it will use the transit method to find new exoplanets, but unlike any mission before, it's going to look at the same spot in the sky for over a year. Super excited to see what data it brings back to us.
L2 as related to space telescopes was a new term to me, and turned out to be utterly fascinating. The Webb orbits the sun and periodically boosts velocity using Earth's gravity:
> The James Webb Space Telescope is not in orbit around the Earth, like the Hubble Space Telescope is – it actually orbits the Sun, 1.5 million kilometers (1 million miles) away from the Earth at what is called the second Lagrange point or L2.
Lagrange points are fascinating to me and I feel they are underrepresented in science fiction, compared to how the space age ahead of us may play out.
The events of human history on earth have revolved in great part around settling at or controlling strategically advantaged locations, for example any coastline, or a geographic bottleneck for trade and travel (think of Singapore and the Strait of Malacca).
A Lagrange point is the simplest space-based analog to this that I know of, if you want to put something in a fixed location relative to other bodies, the Lagrange points are places where you can do it with the highest fuel economy. Then when operating from that position you will have more energy available to do other things, granting you advantage over competitors who are not at the Lagrange point.
So whether it's science, research, trade, defense etc. there is a compelling reason to locate things at a Lagrange point, and it seems this is already happening as we have science satellites at L1 and L2 and I believe L3 has been talked about. The Lagrange points are not all created equal in terms of distance to their respective bodies, size, energy required to maintain a position etc. All two body systems have them, so for example the Earth and Moon have a set of Lagrange points that are significant to us.
The LPs are what a lot of our space politics and problems may eventually revolve around (quite literally!).
> events of human history on earth have revolved in great part around settling at or controlling strategically advantaged locations, for example any coastline, or a geographic bottleneck for trade and travel
Not only that, it's easier to send mass between Lagrange points than it is to send it to them from either of the orbital bodies.
Getting from Earth to L1 or L2, each 1.5mm km away, takes 15 km/s, escape + 12 km/s. (You have to fight both the Sun and the Earth's gravity.) Getting from L1 to L2 takes less than 100 m/s. (L1 to L3, L4 or L5 about 1 to 2 km/s.)
This confers strong defensive first-mover advantages; it's energy-wise easier to hold five than take one from the Earth. (Obviously, it's mass-wise easier from the Earth.)
Relays at L4 and L5 (also described in the linked Wikipedia) would be useful. If both are built it's reasonable for relay stations or satellites stay in contact continuously, if over different paths at different times of the day. The second relay station would also be useful if other objects naturally collected within the regions of stability disrupt communication.
Lagrange points are a key plot device in Iain M. Banks’s The Algebraist. I did figure out the location of the Dweller wormhole pretty quickly, thanks to thinking about how Lagrange points worked, but it is a great work of science fiction.
Regarding sci-fi; Joshua "Lagrange" Calvert did a fancy maneuver in Peter F. Hamilton's Reality Dysfunction involving a lagrange point that gave him that nickname.
I always wondered what kind of fun treasure might be hiding in the L4 and L5 points. And what kind of secret missions were already sent there by various countries to look for stuff. There could be whole precious metal asteroids sitting around!
To what extent (if any) will this program be impacted if all U.S. federal grant funding is permanently cut? Are there U.S. funded components/researchers involved?
As far as I know it won't be affected at all, the project is almost fully funded from the European Space Agency. And it will most likely be launched with the European Ariane rocket.
I wonder, is there any human endeavor other than space exploration (and maybe an occasional particle accelerator) that works like this? Sure, a big factor in the history of scientific progress is its structural resilience against localized political and economical kerfuffles, but that's more of an accident of how discovery and innovation are done - in small increments, achieved near-simultaneously by independent people or groups around the world (only one gets to take the credit, though). Meanwhile, it seems to me that space exploration needs to be organized into a competition to survive and thrive. To make things weirder, it's not about regular market competition - it's about staying in public consciousness, through continuously one-upping each other by Doing Something Impressive, which ends up attracting funding to all agencies each time (and conversely, when things get slow on the impressive achievements front, funding starts to dry out).
(We had one dry spell after Space Shuttles were retired, and IMHO this one could've been fatal to the entire field. Thank $deity for NASA's funding of commercial launch services, and SpaceX surviving 2008 and taking advantage of it to get the Falcon 9 to work and effectively re-light the public interest again.)
I imagine this is a transitional period; we're past the times of Cold War - times when everyone poured ~infinite money into weapons programs and space exploration got to leech some of it off - and we're not yet seeing the bootstrapping of cislunar economy on the horizon. I wonder if there's a more sustainable way of getting through to the other end, because relying on public interest feels rather risky. And, again, I can't think of any other field that is in this weird position.
Yes. In the past long-range sea voyages worked exactly in the same way.
They were seen as little more than expensive intellectual curiosities and eccentricities. In fact even once we discovered the New World had Columbus not come back and lied his arse off about riches that existed there only by coincidence (as he'd seen nothing of what he claimed), it's entirely possible that would have been the last journey to the New World for decades if not centuries. And over those decades you'd probably have had more and more of the population believing we never even landed on a New World to begin with.
And it'll be the same in the future. Eventually humanity will become a multiplanetary species and more value will be generated off Earth than on it. And I think we're probably not that far away from such point, but we live at a time when we will happily dump trillions of dollars to fund pointless chaos halfway around the world (that invariably just makes the world less safe for everybody), yet every penny that could take us closer to these species defining events is scrutinized like we're down to our last pennies.
And again - this isn't new. It's been the case for centuries and probably will be the case for the foreseeable future of humanity. It's easy to explain with a tautology - positions of power are held by those attracted to power, and those attracted to power are attracted to power. Once the New World became a means to power, that's when the 'trillions' started pouring in. The same will happen with space.
Yeah I was really looking forward to that alt history where the Aztec Empire reached technological parity with the rest of the world. All hail Huitzilopochtli!
Technology wasn't the primary cause in the genocide of the Native Americans. The initial factor was the introduction of plagues to the Americas from the numerous intraspecies transmission that occurred in the old world as a result of the millennia of large animal domestication alongside high population density that had no analog in the new world (since there weren't the same variety of large domesticate-able fauna, apart form like alpacas or something). This is also why there was no American plague that spread in the other direction.
Western Europe was certainly not so far ahead technologically relative to the rest of the world as people so frequently give them credit for. Not until they had free reign over a new continent and purchased slaves to generate free money (*) and eventually total dominance with the advent of the industrial revolution.
(*) This also led to an arms race between rival empires and kingdoms in Africa and the stagnation of local craft and the eventual the economic collapse and political fragmentation of the wealthy empires that existed throughout antiquity and the middle ages - that have since been written out of history books. When the industrial revolution began spinning up out of the ashes and rubble of Christendom post-reformation, many other regions like the Middle East (for example the palace intrigue and power struggles within the Ottoman dynasties) and China (With the collapse of the Ming and ascendancy of the great Qing from the North) were similarly in crises - in part from indirect economic interaction with the growing powers in the west. It was then the nascent imperial powers found the world ripe for their exploitation and eventual hegemony.
The Aztecs, a millions large extremely militant civilization, were conquered by Cortez and his "army" of 500. Even if 95% of the Aztecs were sick, which they weren't, they would have outnumbered him by many orders of magnitude. The fundamental problem is that the Aztecs were armed with basic bows, and primitive melee weapons like wooden clubs. The Spaniards had rifles, plate armor, and longswords. This is what enabled a group of 500 people who didn't even speak the language to gather "allies" and single handedly destroy an entire empire with centuries of military experience.
There were also plagues that spread in the other direction - the obvious one is syphilis. And the claim that slavery is what caused Europe's success is similarly not well supported. Most of every great empire in the world had massive numbers of slaves. In fact the word "slave" itself derives from "Slav" [2] owing to their enslavement in many empires across the world. Yet these empires, for the most part, failed. While Europe thrived.
Or even take the Americas. Less than 10% of slaves taken from Africa ended up in North America, yet North America would become the dominant power in the world, extremely rapidly. Or even within America, the colonies (come states) that were most averse to slavery would be the ones that would thrive the most. I mean the idea that slavery played some key role just doesn't make any logical sense. It's just the neohistorical self loathing nonsense.
History's full of awful stuff, so is the present, and so too will be the future. Be happy it went as well as it did. There are timelines a plenty, probably the overwhelming majority, that make the terribly flawed society we have today look like a utopia.
Along with the other subjugated groups who turned on their imperial suzerain, as you briefly alluded to.
>The fundamental problem is that the Aztecs were armed with basic bows, and primitive melee weapons like wooden clubs. The Spaniards had rifles, plate armor, and longswords.
Yes that was certainly an important factor, though obviously entirely insufficient to explain how an entire continent of various empires confederations and cities fell over decades and centuries, and the vast majority of the population wiped out.
>This is what enabled a group of 500 people who didn't even speak the language to gather "allies" and single handedly destroy an entire empire with centuries of military experience
Sure in the isolated and specific context Cortez's victory over the Aztecs probably was largely influenced by their technological advantages along with their deception, ambushes, and the "suprise" of their foreign origin etc. (but not totally determined, since by their own account there was like a hundred different times they could have been slaughtered en-masse if their hosts weren't as initially hospitable).
You're gonna have to provide a bit more justification for how the rest of the continent's eventual collapse and depopulation follows immediately from that though. It takes a lot more to justify asserting that a single factor should be solely recognized as the determining historical cause for an outcome. There were many factors and any one of them must be considered carefully and in relation to all others, and my point was to show how neglected the others are in favor of "europeans conquered everything just cause they were better". There's a lot more to be learnt by recognizing and studying details over broad oversimplifications that require no more insight or nuance.
>There were also plagues that spread in the other direction - the obvious one is syphilis.
It seems likely but not entirely uncontroversial though I personally can't speak on it.
In any case would you like to count plague for plague? There is an clear asymmetry in the scale of transmission as well as in the immunological defenses of the respective populations in the old world and new, it would seem reasonable the discrepancy could be due to the asymmetry of scale in large fauna to human proximity - which is responsible for intra-species transmission and by extension the major illness and plagues - but clearly none of these biological-historical conclusions are certain.
>Most of every great empire in the world had massive numbers of slaves.
Yes and none of them had the industrial system of slavery extraction and use on a massively depopulated continent in order to extract massive amounts of natural resources on a scale that was hitherto unparalleled historically. Note that I didn't want to talk about the unique social and economic system then emerging in western europe after the reformation since my comment was already meandering and oversimplified enough. I also agree that American slavery wasn't the sole money printing machine that led to European dominance, but a crucial factor in generating capital and material resources as well as a symptom of the more influential underlying mechanism - namely the emergence of the system of trade and economic relations that would later be recognized as capitalism, which proved far more effective in generating wealth and political power than whatever bastard form feudalism you could generally argue it superseded.
>colonies (come states) that were most averse to slavery would be the ones that would thrive the most.
Wow its almost as though financial hubs (especially ones based around centers of commerce linking a region of production with external trade) can generate profit from economic activities not in the immediate locality. Did you at least try to use your brain before you decided to insult me?
>It's just the neohistorical self loathing nonsense
Also self-loathing might be a bit of projection since I personally have no familial connection to the trans-atlantic slave trade or any nation that benefited from it. I'm sorry you suffer from such conflicted feelings on your own heritage but I'd recommend not lashing out at strangers in unrelated conversation.
>History's full of awful stuff, so is the present, and so too will be the future. Be happy it went as well as it did.
Again I'm not too sure why you've decided to read some kind of moral argument into my sweeping over-generalization of history? It's really not relevant to what was being discussed and even if it was I'm not sure that the takeaway is that we should just "happy it went as well as it did" or whatever? I'm not really sure what you think there is for people to be "happy" about or specifically what I've failed to be "happy" about since as far as I can tell I've provided a critical analysis of a historical period independent from any given moral framework. Unless of course you object to any such analysis that doesn't affirm your particular moral perspective.
>Be happy it went as well as it did.
lol for who? Wasn't too swell for the native americans... (nor my own people for that matter, if this is really the discussion you'd rather have). It might surprise you to learn that there are other people in the world with a different background to yourself.
But to be honest I couldn't be more disinterested in that useless conversation, trying to analyze history in a discrete set of "right" or "wrongs" that we must urgently assign condemnation or affirmation to at each point. History has happened and is happening, one should seek to analyze it's material basis either for its own sake or to apply it critically to the present, not paint hagiographies or interpretations to justify whatever belief systems or identities they've constructed.
You know, I'm verbose but I generally try to speak holistically and have some clear point(s) ideally with falsifiable arguments. We all want to ramble stream of consciousness style unloading all of of our own biases (which are, obviously, the right ones), but have some respect of the fact that you're expecting somebody else to read what you're writing, and clean things up.
The only sort of falsifiable content I can find in your post is a claim to justify the alleged exceptional impact of slavery in North America, in spite of the relatively small number of slaves, is that it was used to extract natural resources on a massive scale, yet that is again inaccurate. Its primary usage was in localized agriculture. Things like industrial mining were still relatively limited.
In that case it would be similarly be helpful if you focused your initial response on a key point of contention rather effusively and ineffectively allude to several. I will keep my reply as focused as possible.
You initially claimed that it was purely technological superiority that allowed Europeans to conquer America. This is not an understanding reflected in the literature. If it were the case, then why was it only much after the colonization of America, which began in the 16th century, that Asia and Africa were able to be colonized, in the middle of the 19th century? The difference between the technologies in the 16th century was not a huge jump, though its obviously true there was a discrepancy. Native Americans acquired horses after contact and incorporated them into their culture and by the 1700s some of the tribes in the great plains had fully transformed into a nomadic horse based life-style. Firearms are a similar story. One can imagine the difficulty 16th century europeans would have faced if they were to colonize an entire continent, without it being conveniently depopulated beforehand by plague.
You appear to recount that my claim was that American (US) slavery was a unique factor in the exceptional rise of Europe in the early modern period. This was a claim made by no-one. You'll recall that slavery in america refers to an entire continent - as I repeatedly pointed out - not an isolated group of states. My claim is that the depopulation and subsequent colonization of the entirety of the continent was a significant factor, along with the shift in political and economic structure that accompanied it.
Up to the 16th century you will find a wealth of european accounts of contacts with kingdoms in the Congo to East Asia, whereby they are described as equals in sophistication and size - most famously with Marco Polo's accounts though there exist many others. The change in perception of relative technological prowess in historical accounts occur much later, but certainly by the 1700s with the advent of the industrial revolution in the early modern period. This is well documented.
Why did the industrial revolution occur? It is a very large and open topic, though I lean towards the explanation that it was due in part to both the change in social structure during the reformation, as well as the colonization of america (the continent) and the development of economic networks with the extraction of resources (mercantilism, chartered trading companies etc.). This system was aided by and intensified by the trans-atlantic slave trade.
I'm sorry about the lack of "falsifiable content", or the lack of brevity. Unfortunately we are discussing history through the most sweeping lens possible, not science.
>unloading all of of our own biases
Again, what are you vaguely trying to allude to. Just say it.
The reason colonization spread to other places late is that there was real no demand for what it could offer. The Industrial Revolution changed that. It led to dramatic increase in the need of various supplies, not only from industrial processes, but also from urbanization and the rapid growth of richer middle and upper classes and their increasing consumption. The "Scramble for Africa" only really began in the 1880s, long after slavery had been banned in most places.
My description of the technological differences in the Americas was not off the cuff. Cortes' group was armed, literally, with guns (including handguns), cannons, longswords, and more. They were wearing steel cuirass for defense. And they were facing people wielding wooden clubs, primitive bows, and defending with wooden shields and basic padded armor, if that.
And the entire world, let alone the Americas, started out depopulated. In many ways it still is. Today if we spread out each person there'd be enough area for ~4 football fields per person. But back to the Americas nobody knows what the population was so there range estimates from 8 million to 53 million [1] (excluding one loony toon outlier), with an average estimate of just about 30 million. So if every person was spread out evenly, this would be an average of 273 football fields per person. But of course people, even back then, were packed into relatively densely packed settlements. So you're talking about seeing thousands of football fields of area, on average, without ever seeing a person. Clearly no major depopulation events were necessary.
And the reason the industrial revolution occurred is quite simply because technology reached a threshold enabling it. People had been trying to automate various processes for millennia, but lacked the prerequisites to succeed. It followed the development of a large number of technological breakthroughs - the steam engine, coke over coal, and so on.
I'm happy to. But then, like most people, I'm impatient, so I'll draw a second plan that ensures I get to see at least some of the cool stuff before I die, and then I'll get annoyed when this plan isn't followed.
Galactic timescales are large. Human lifespans are tiny.
What's the typical time scale for a transit?
Also, why use transits instead of the Doppler method? Has this patch of sky been selected based on previous Doppler method star studies?
Thanks!
Generally measured in hours, or minutes. For example, if we were observing our system with perfect alignment, Earth's transit would be about 12 hours, Jupiter's transit around 29 hours.
> Also, why use transits instead of the Doppler method?
Quantity. PLATO can observe a sizeable portion of the sky at once, 100k+ of stars. With Doppler method the quantities are smaller + afaik there is a trade-off between number of stars being observed and the velocity we can measure. So to find Earth-like planets around Sun-like stars, we would likely have to go one or a few stars at a time.
> Has this patch of sky been selected based on previous Doppler method star studies?
I am not actively involved anymore. So I am not sure if they have already picked what part of the sky they PLATO is going to be observing. The previous Doppler method (aka as radial-velocity or rv method) star studies play a role, not only because if there's one planet, there might be more, but also because rv gave information about the star. However, keep in mind that this is to find new exoplanets, less to find out more data about existing ones. Rv will definitely be used along side PLATO, to confirm and gather more information about exoplanets that PLATO finds.
> Earth's transit would be about 12 hours, Jupiter's transit around 29 hours
…per year, for Earth; per ~12 years for Jupiter is I think what the GP was asking.
This is extremely dependent on the radii of the inner and outer limits of the the habitable zone for any given star, though, as well as the star’s mass.
You can find much less massive planets with the transit method.
The Doppler method relies on the planet pulling on the star to change the star's line-of-sight velocity periodically. Because planets are much less massive than stars, the star doesn't move much. You can only find massive or close-in planets with this method.
The transit method is much more sensitive to small planets like the Earth. It's true that the smaller the planet, the less of the star's light it blocks, so it's still easier to detect large planets than small planets using the transit method. However, it's much easier to detect small changes in a star's apparent brightness than it is to detect small shifts in the star's velocity.
There are a few different viable methods of detecting planets. Each has its strengths and weaknesses, and astronomers use all of them.
Radial velocity surveys require so damn much light, and such a complex precision spectrometer that they're only used on the very largest 8m-10m class telescopes on the ground, shooting in near infrared through the most advanced adaptive optics (or even interferometric modes) in great weather, pointed at a single target for a long period of time (this is a big deal), with a focus on super-Jupiter to Jupiter class objects in tight orbits.
The next generation of 30m class telescopes will be an order of magnitude more capable for the RV method, but even then you're not really going to be able to get fast locks on Earth analogs.
The RV method is vastly superior for detecting the planets we really care about - high confidence nearby Earth analogs. The odds of a transit being in the right plane for us to observe are tiny. But if we want to run a survey like that like it really matters (let's say a Solar system catastrophe hits a thousand years from now and humanity wants interstellar diaspora), we'll be studying the nearest thousand stars with the RV method using significant numbers of 100 meter class telescopes, or perhaps big space based interferometers produced in mass quantities, for decades.
What transit studies like Kepler do is study a small patch of crowded sky (most of the stars being very distant) with the sensitivity for very rare in-plane Earth analogs, in order to get a representative sample. When I was born we couldn't say with any confidence that planets around other stars existed, post Kepler we know that they're common. We can perform these surveys even with the shoestring budgets current governments afford astronomy because even if the odds of successfully detecting a planet that does orbit a distant star are very low, we can watch a million stars at a time.
Hi, thanks for answering the questions in this thread, it feels like something out of a sci-fi novel. Do you know of any similar projects that a software engineer could contribute to in their free time? Could be of much smaller scale of course.
The transit method requires observing a dip in the brightness of a star. Actually - three dips. The first dip indicates - but does not prove - the existence of a planet transiting in front of the star. The change in intensity, rate of change of intensity, and duration of the dip all give us information.
The second dip, if roughly identical to the first dip in parameters, gives us the orbital period of the star. So now we wait a second period in order to observe the expected... Third dip, which confirms the planet if it occurs with the same parameters at the expected time.
Though I think that such observations would require at least two years, and up to possibly four years, for stars with orbits of periods similar to our own. I don't believe that a single year is long enough.
> Though I think that such observations would require at least two years
It is at least two years at least if I'm understanding this⁰ correctly:
Observational concept
Ultra-high precision, long (at least two years), uninterrupted photometric monitoring in the
visible band of very large samples of bright (V ≤11-13) stars.
I should have been more clear in my original post. AFAIK there are two options on the table - looking at two fields, both 2 years OR looking at one field for 3 years and then doing "step and stare" for the rest of the mission. Step and stare being that they "step" into a new field, "stare" at it for some time, and repeat.
> Is it to get a more exhaustive survey single star or can full of stars?
PLATO will look at 100k+ stars at once. And for most we will be unlucky to see a transit between PLATO and the star. Geometrically it won't align - imagine the star systems being in different angles from us. To bring an analogue - Take a pack of cards and throw them in the air, and take a quick picture while they are sitll in the air - how many cards will be facing the camera exactly with their edge. For us to spot a transit, the planet has to pass between us and the star. If the orbital plane is not parallel to us, we will miss the transit. So that's one of the reasons why it helps to look at bunch of stars with transit method. We expect that about 1% of the orbital planes will be aligned so that we can get meaningful data.
> Or does that help it find smaller/further/different planets?
Imagine you are trying to find Earth from another solar system. The longer you look at our Sun the higher the likelihood that Earth will pass between you and the Sun. And once you get lucky, and the Earth transits between you and the Sun, the brightness of the Sun only dips about 0.01%, so that means that in order to find small planets we have to have sensitive instruments and little noise, so that the dip in brightness can be measured. Furthermore, as the planet passes the transit and continues on its orbit, the perceived brightness of the star will increase, due to the planet reflecting some extra light. Measuring that can gives us some rudimentary information about the atmosphere - e.g. if a small planet reflects a lot of light back, maybe it's covered in clouds or snow.
> And how do they pick where to point at?
There's a whole complicated process to find consensus on where to point. Basically they look at spots that have lots of stars, and they look what type of stars they are. Here the objective is to find planets around Sun-like stars, so they would prioritize fields that have more Sun-like stars.
> Is there a way of guessing the likelihood of finding a planet?
It seems that some stars are more likely to have planets than others.
Since I have your attention - I figure this is still the best condensed ELI5 explainer of the history and methods used in search for exoplanets, and I keep sending this to anyone remotely interested in the topic:
(I also consider it to be the only true, original, canonical rendition of the Alladin song.)
It gets into the transit method around halfway through (at 3:43), and makes it glaringly obvious why this is the way to go, over tracking Doppler shifts. Still, this video is almost 8 years old (and neatly coincided with discovery of additional planets around TRAPPIST-1) - I wonder if there are new methods at play that are not covered here, and of course if the middle part still corresponds to how things are done?
You said:
> We expect that about 1% of the orbital planes will be aligned so that we
> can get meaningful data
Somewhere below, someone used the figure of 0.01%. I assume they were mistaken, and your 1% number is about right for some "average" star sizes and orbits.
At any rate, that figure depends on the size of the star, and the distance from the star that the planet orbits--the further away, the smaller the chance that their orbital plane would be aligned with our solar system. For a Sun-class star, and a planet inside the habitable zone, what is the %? Am I correct in thinking it would be approximately 0.5/180, where 0.5 degrees is the apparent size of our Sun in the sky, and 180 degrees is of course half a circle (since it doesn't matter whether we're on one side or the opposite side of their star, hence 360/2). Which works out to about 0.14%, right?
How does the 0.01% look in comparison to the natural variability of star brightness, due to cycles, spots etc? Would that be a concern in terms of false positives? And also, given the specific line-up needed for us to see the pass, how likely it is for us to be able to observe the same planet in front of the star in the following years?
Stars do change their brightness in various other ways, but the light curve of planetary transit has a very characteristic shape. It causes the brightness to dim by a small but constant amount, with a (comparatively) very short and sharp start and end. A transit causes this pattern to occur at precisely regular intervals, and I don't think we know of any phenomena related to a star itself that would imitate the same effect.
Stars' relative positions generally don't change fast enough for the angle from which we observe a transit to change significantly. A transit of HD 20794 d is visible anywhere within a roughly 0.7-degree wide band. But our angular rate of motion with respect to the star HD 20794 is the same as its rate of motion in our sky, about 0.001 degrees per year. So the transit will most likely continue to be observable for decades or centuries to come, depending on exactly how the planet's orbit is aligned.
Would it be feasible to place telescopes at other orbital inclinations with respect to the sun in order to spot transits in stars that aren't within Earth's orbital plane ?
The orbital inclination relative to our sun doesn't really have anything to do with it. In fact, stars that are aligned with Earth's orbit are harder to observe, because they go behind the sun once a year.
Detecting an extrasolar planetary transit requires us to be aligned with the planet's orbit around its star. And since those stars are so far away, you would have to travel an immense distance away from our solar system to appreciably change the relative angle.
HD 20794 is about 20 light-years away from us, so changing our observation angle relative to it by 1 degree would require traveling about 0.35 lightyears. Our fastest-ever interstellar probe, Voyager 1, would take 5000 years to travel that distance.
Thanks for the clarification. You are absolutely right, in my post above I accidentally used the word "parallel" that caused the confusion. It wouldn't even be practically possible to use PLATO to observe them.
Probably not the best choice of words from me there. However, there is a positive correlation between a star's metallicity and the number of planets a star has.
Your words are fine from my point of view,
I am just tickled at the though of how hard it is to prove a star has no planets.
Even with all stars having planets, it is worthwhile to carefully choose
the field to maximize the chance of detection. Best would be if planetary disks aligned themselves in any predictable manner, but not much hope there.
Light collection. You want to observe one point for a really long time so you get a really good understanding of where the light is coming from, the properties of that light, and its behavioural patterns.
A lot of the detection is statistics around signals, so the better (read more thorough and coherent) your data (observations of changes in light), the more confidence you can have in your conclusions around what's causing the changes (planets with different atmospheres, different positions, different sizes and compositions etc...).
Very cool. Got a silly sci-fi question for you. IIUC, with current technology it would take on the order of tens of thousands of years for a vessel to physically travel to the closest known Earth-like planet (correct me if I'm wrong).
So any thoughts on what kinds of hypothetical breakthroughs would be needed to make the trip doable in (say) less than a human lifetime?
A different stab at this is to ask what it would take to build a telescope that could image some of these Earth-like planets, a project that turns out to be easier (in a very loose sense of that word) than sending cameras there.
The idea is you send a camera very, very far out in the Solar System (hundreds of AU) and then use the Sun's gravity well as your lens. Neat stuff and, unlike the interstellar probes, potentially doable in our lifetime.
Normally, diffraction and the effective aperture are what limit optical resolution. How does that work with gravitational lensing? Does the effective aperture become the diameter of the sun?
I'm too ignorant to answer that, but the technical paper here [https://arxiv.org/pdf/2002.11871] goes into a wealth of detail, and includes an image of Earth as it would appear to such a telescope (before and after post-processing) from 30 parsecs away. The optical properties of the solar gravitational lens are pretty astonishing.
Self replicating automata as described by Von Neumann able to repair and duplicate themselves, and other things like electronic components. ICs keep getting faster (so far) but use smaller and smaller features of silicon and could wear out from metal migration and all components will be under much more cosmic radiation than on earth. This makes a large shield of heavy material on front of vehicle to minimize this effect but that increases the energy/fuel needed. The space shuttle only took maybe week long trips but it had four computers for flight control , three extra in case of failure in different parts of the shuttle along with IIRC a separate backup backup computer in for use as last resort.
* Research faster interstellar travel, especially using something like a Buzzard engine to utilize interstellar hydrogen as resection mass. Required nuclear fusion power plants / engines and ridiculously strong magnetic fields; both seem attainable.
* Slow down human body metabolism and allow humans to stay asleep at near-freezing temperatures for a long time. If bears and chipmunks can do it, chances are humans could learn it, too.
* Invent sets of machines that can reliably self-replicate, given most basic inputs like minerals, water, and sunlight. Advanced semiconductors are going to be the tricky part.
* Study psychology, sociology, history, game theory, etc, so that the early society that will form on the new planet, isolated from Earth, would avoid at least some of the pitfalls that plagued human history on its home planet.
Also, it won't work unless scaled up to the sort of thing only a Kardashev type II could do — 4000 km diameter — and at that level you've got other options that mean they probably won't:
>Slow down human body metabolism and allow humans to stay asleep at near-freezing temperatures for a long time. If bears and chipmunks can do it, chances are humans could learn it, too.
The thing is - our current bodies can't live in space for long. So either we will have to build new bodies for us somehow or build a ship that can have gravity inside and protection from space outside (and we are talking about very heavy protection here)
In any other case there is no point in slowing down metabolism or whatever. You will die rather soon.
Time dilation means that the closer you get to the speed of light the less time you experience passing. So even a 12000 year long journey as seen from earth, if moving fast enough, could feel to the travelers like a much shorter amount of time.
Yes, but practically with todays technology there is no feasible way of getting to a speed where time dilation matters over that distance, we run out of fuel so we need some external power source like a laser or solar wind that have other issues, iirc one only gets to 2x time dilation at 0.9 c. That’s a lot of acceleration.
We need to think about where we want the knowledge and what knows it. We could use humanoid AIs. We could hatch humans "just in time". Run them in a sim to 18 then release them on their mission. Ethics would need to accept this. Maybe we would be happy slowly expanding across the universe and an decendant talking to 'the aliens'.
I am not totally serious. But you wanna meet aliens? Gotta do something a bit radical.
If you haven't, you should read Accelerando, it's a collection of short stories IIRC that were put into a novel by the author. I didn't want to start with that, but that is in there. :)
If I may suggest another read: Perfect Imperfection by Polish author Jacek Dukaj. It's definitely weirder, than Accelerando, as the book drops you straight into the last parts of evolution curve, but definitely worth reading if you have liked Accelerando.
The story is super weird, but what I found out is that piecing together a picture of a far-future society from this story was very exciting.
Figuring out the optimal placement of CCDs on Plato's 24(+2) cameras. Due to the way CCDs are fabricated, their properties vary a bit, they are not identical. For example, they can vary how much light they can hold before they become saturated. Given the high cost of fabricating these CCDs, and the fact that for each camera 4 CCDs are used, and all these 4 have to share front-end electronics, it was prudent to optimize their grouping to we maximise the dynamic range we get. More dynamic range means that we can tell more about the planets we find with higher confidence.
Yes. In telescopes they use high-end CCDs with really big pixels for better light sensitivity and zero dead pixels.
This is a picture of the CCD array for the Gaia space observatory that used parallax to measure precise distances and slightly less precise angular velocities of billions of objects
Good question.
No, these will essentially be black-white "photos". The amount of light is measured. The reason for so many CCDs is so that the field of view would be as large as possible. A larger field of view enables to look at more stars at once. Given that we will be locked into looking at one spot for a whole year, it ups our chances of spotting something cool if we maximise the number of stars we are looking at.
However they won't be photos of planets really. It will be countless photos of the same stars over and over again, it's just that sometimes they will be slightly less bright than other times. Directly imaging exoplanets is incredibly difficult, but humans have managed it: https://en.wikipedia.org/wiki/List_of_directly_imaged_exopla...
Do they move the telescope over the year to account for movement? How is that calculated? Does this change with being closer to planets and their gravitational pull?
Yes, it's something that's referred to as pointing stability. The telescope will have star trackers to precisely know it's relative position - basically you make sure that you see the correct stars from where it is placed on the spacecraft. It will use reaction wheels to make tiny correction's to its position. Imagine you are in a computer chair and trying to spin yourself without feet or hands touching anything, just by twisting your body. Reaction wheels work on the same principle. As Earth completes a year around the Sun, the gravitational pull from other solar system bodies is very minor on PLATO. That said, keeping a spacecraft in L2 is not easy - there is nothing to "orbit".
The orbital corrections are minimized at L2, because of the relative distance of the moon and other planets vs size. But that is what is accounted for in the corrections.
How far away PLATO will be from the James Webb Space Telescope? How big is the L2 Lagrange point? (i.e., how closely do you need to be for an orbit around L2 to be practical?)
> How big is the L2 Lagrange point? (i.e., how closely do you need to be for an orbit around L2 to be practical?)
The L2 point doesn't really have size, and even its location isn't stable. It's a mathematical point, and when we say "orbit around L2" then that is not fully true either. The spacecraft are on what's called "halo orbit" - maybe imagine balancing a steel ball (like from a bearing) on a bottle that's sideways, it's probably easier to roll and balance the ball lenghtways of the bottle, than on rolling it sideways. The best analogy I could come up with. You don't want to be too close to the L2 point, as then the orbit would be very short and less stable, think of it as having a smaller bottle - probably harder to balance the steel ball on a smaller bottle than a big one.
> How far away PLATO will be from the James Webb Space Telescope?
Probably on the magnitude of hundreds of thousands of kms on average. Interesting question though, hopefully they won't get too close :D
Cheaper than rental costs (in Australia), additionally Australia has excellent "Grey Nomad" facilities as a very big country relative to a small population (same land area as 48 state mainland US, ~ 25 million pop.).
It's always been a country of swaggies, less so now, but working on the move and camping are in the DNA of many.
There are manufacturing processes that benefit from microgravity (e.g. growing protein crystals for the pharma industry, producing semiconductors, etc).
Beyond that it would be a significant boon for science.
Seems like the primary benefit comes to silicon wafer manufacturing. Growing pure silicon crystal is much easier to do in a microgravity, vacuum environment:
> The study reported that for semiconductor crystals processed in LEO compared to terrestrial samples, more than 80 percent improved in either one or a combination of structure, uniformity, reduction of defects, and/or electrical and optical properties–and some by orders of magnitude
For actual device manufacturing, there are potential benefits as well, but this is less well researched area (possibly as a result of the difficulty of getting advanced IC manufacturing equipment into earth orbit).
I do somewhat doubt that the economics would work out. Silicon wafers are expensive, but I'm not sure if the price is currently higher than that of launching a bunch of sand to low earth orbit.
What fraction of machine time is currently spent pumping wafers down to molecular-beam vacuum? What fraction of machine mass is dedicated to holding that vacuum? Vibration isolation would also be much easier. Not sure if these are enough to matter, let alone enough to justify a rocket, but maybe the math can be made to work.
Well... It's not like it can get any slower, can it? Waymo is the industry lead and yet it offers rides to only a small closed group of beta testers. They only deploy it in geofenced areas. It seems that they deploy the driverless variant, but every Waymo I ever see has a driver behind the wheel, driving it manually, night time or daytime. This rollout is glacial.
It's been 16 years since the DARPA Urban Challenge. I'm happy to be wrong, but I really don't think robotaxis will penetrate the market to mass adoption like many predict, and if it does, it will be in 50 years or more. In 20 years robotaxis will still be a problem of legislation and struggling with adoption, not a technological problem. American car culture is too ingrained.
At most, driverless robotaxis will be symbols of tech companies along the coastlines. They won't transform transportation for the working class because in 20 years, 95% of drivers will still want to drive themselves.
You say "along the coastlines" like that's supposed to represent a tiny sliver of the population.
In fact, depending on how exactly you define coastline (does the gulf of Mexico count?), probably the majority of the population lives "along the coastline".
As for the definitely landlocked populations, they have already been enjoying the benefits of self driving vehicles for many years in the form of autosteer on their tractors.
This looks amazing, but installing the Firefox extension I am worried about all the permissions it asks. I am surprised how comfortable people are signing off on these permissions. How do people at HN put these security worries to rest?
This (your fear) is a result of bad policy by Firefox. This is why a lot of useful add-ons or plugins died, and, overall, Firefox became a shittier browser.
Neither Vimium nor SurfingKeys don't hold a candle to KeySnail because back in the days add-ons worked you could control the browser's chrome as well as a bunch of other non-HTML elements.
Today, you cannot even use browser extensions to close a browser window if the page didn't load in it.
These tools were intended for "power users", who could establish for themselves if the piece of code they want to use is doing something malicious or not. Also being an easy way to extend the browser without a need to recompile it and a need to understand a huge project with a ton of infrastructure... flushed down the drain.
This reminds me about how Alan Key said in one of his interviews that if a motorcycle was invented today, it would've been outlawed right away due to safety concerns.
Auditing each tool by ourselves would cost a lot of time. Not to mention that it would not be a one-time thing. At each update, another check would be required for "peace of mind".
Curious to discuss if there is a way to trust these extensions without establishing ourselves that the code is not harmful.
But you don't audit it entirely by yourself. Nor were you expected to before. It's the same idea as with other programs or add-ons you use. Don't you use some add-ons in the code editor you use not authored by the authors of the editor itself? And why would you believe the authors of the editor in the first place?
Of course you need to do some due diligence, but it isn't anywhere near as taxing as you seem to think.
Security is worthless if it prevents you from doing useful things. Given a choice between a chance of security breach and not being able to do the useful thing at all, in the circumstances like using a Web browser, I'd definitely choose to have the useful thing w/o security.
It seems it would depend on the persons risk tolerance.
And assessing risk of freely available open source software is still difficult, you either rely on all the authors being standup citizens, or on the bulk of the reviewers to be truthful and knowledgeable.
It's open-source, about 10K lines of good quality self-contained JS code with no obfuscation so it's not that hard to go through it yourself. It moves fairly slowly these days so once you have done this once it's easy to stay on top of the changes.
Work and personal, but also as dedicated offline password managers. If I don’t need camera functionality or wifi, then can simply pop those out. The options are endless.
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