Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Our Solar System Isn't Normal

npr.org

Post reply on HN
Print view View original

71–80 of 107 posts

Re: Our Solar System Isn't Normal

#71

Post by lake99 »

mturmon wrote: post #68
lake99 wrote: post #29

Earlier quoted context omitted.

tocomment is right. Watch http://www.youtube.com/watch?v=8JTneTI82nE from 5:00 to 7:00. Yes, scientists may have been quoted in this article, but I have seen how most journalists mangle, ignore, or sensationalize things that were said.

That's a great video, and obviously she is very qualified to speak to this subject. I don't see how this shows that the GP comment is "right" in its assertion that this is just an effect of biased sampling. I only had time to look at the first few minutes, but around 6:50 she does say that our solar system is "not that common", which she quantifies as "it could only be as much as 10-20% of star systems". Maybe that m…

I agreed with tocomment that it was a biased sampling not in the sense that planetary systems happen to be this way in the region we are looking at, but in the sense that planetary systems seem to be this way when we look at things from THIS set of instrumentation and methodology.

IOW, I disagree with NPR's claim that "Our Very Normal Solar System Isn't Normal Anymore". Addendum: It may indeed be abnormal. But we don't have data to conclude that yet, or even to suspect it.

Re: Our Solar System Isn't Normal

#72

Post by mturmon »

lake99 wrote: post #69
scott_s wrote: post #59

Earlier quoted context omitted.

She also agrees with the main point of the original article, which is that our solar system is probably unusual. (From 6:47 to 7:00.)

Unusual is a subjective term. She says 10%-20% of the planetary systems are like ours. Are you saying that that was the point made in the original article too?

"Unusual is a subjective term" -- absolutely. I don't want to go back and forth on this one either.

Listen carefully to the video. She says "It could only be as common as 10-20%". Just before saying that, she pauses and looks upward, to formulate the sentence correctly. The 10-20% number is an upper bound, not a direct estimate.

You have to give her credit for communicating the idea carefully. The difficulty of doing this in real time is extreme. And if you do it wrong, you really get taken to task by your colleagues.

Re: Our Solar System Isn't Normal

#74

Post by tocomment »

ra wrote: post #3

Kepler has been revolutionary in discovering these 700 odd planetary systems, but we can't even begin to imagine what surprises await for when we point the James Webb Space Telescope at them. One of JWSTs mission objectives is to study the planetary systems discovered by Kepler, and the origins of life. http://en.wikipedia.org/wiki/James_Webb_Space_Telescope#Miss...

What specifically will the telescope tell us about this exo-planets? It surely can't image them directly, right?

Re: Our Solar System Isn't Normal

#75

Post by gwern »

IsaacL wrote: post #19
Filligree wrote: post #10

It's true that this could still turn out to be mostly observational bias, but I feel like everyone is missing the monkey wandering across the corridor. The anthropic principle, that is. Isn't it possible that, while gas planets clustered closely around the star is the normal shape of solar systems, such a configuration is not amenable to complex life?

It would also be a good candidate for the Great Filter - the hidden factor that has stopped the development of all the other intelligent civilisations that would otherwise be out there. That would mean this is good news - we'd rather the Great Filter lies in our past (because that means we've already survived it) than in our future.

I don't think it's a good candidate; certainly it pushes some amount of the Filter into our past, but even if only 1 in 700 solar systems is Sol-like, there are so many we'd still expect to see tons of aliens. For a single-step Filter or for solar systems to even be a majority of the filter, you need a step so unlikely that it can push the presence of interstellar life down from, like, trillions of star systems to ~1.

Re: Our Solar System Isn't Normal

#76

Post by sbierwagen »

3JPLW wrote: post #5
tocomment wrote: post #2

I would argue the exo-planets we have found so far are a very biased sample. We don't have great technologies for detecting solar systems like ours. And at least the first few years of planet hunting we'll tend to find a lot of large giants orbiting close to their stars since they're the easiest to find.

I was very surprised that the article made no mention of such a bias. It was my first thought, too. I'm not terribly up-to-date on how Kepler has been detecting planets, but isn't it due to the 'wobble' of the stars? Surely they'll find planets that orbit faster (and wobble their stars faster) first. It'll take many many years of very consistent observations (or one very lucky day) to see a wobble (or occlusion) from…

Most exoplanets are discovered by the radial velocity method, (tracking the doppler shifts in the spectrographic lines in the light emitted by the star) but the best data is produced by Kepler, which uses occlusion and thus can tell you how big the planet is, by how much the star dims.

Both methods are biased towards finding big planets (which produce clear, easy to detect spikes) that are close to their star. (so you get enough data points) Kepler tends to be a little more biased, simply because it hasn't been running long enough: http://en.wikipedia.org/wiki/File:Exoplanet_Period-Mass_Scat...

Kepler was launched in 2009. Realistically, you'd have to run it for another three or four centuries if you wanted to detect exoplanets that orbit as far out as Neptune. (orbital period: 165 years) No wonder we're seeing a lot of planets orbiting close in!

Re: Our Solar System Isn't Normal

#77

Post by IsaacL »

gwern wrote: post #75
IsaacL wrote: post #19

Earlier quoted context omitted.

It would also be a good candidate for the Great Filter - the hidden factor that has stopped the development of all the other intelligent civilisations that would otherwise be out there. That would mean this is good news - we'd rather the Great Filter lies in our past (because that means we've already survived it) than in our future.

I don't think it's a good candidate; certainly it pushes some amount of the Filter into our past, but even if only 1 in 700 solar systems is Sol-like, there are so many we'd still expect to see tons of aliens. For a single-step Filter or for solar systems to even be a majority of the filter, you need a step so unlikely that it can push the presence of interstellar life down from, like, trillions of star systems to ~1…

Thanks for the reply, and yes, that makes sense. What would you predict as the most likely other steps in the filter?

Looking at our own planet, I would guess that it's a combination of a) it being simply infeasible to send large animals to distant stars (we haven't yet colonised the moon or even made a serious attempt to colonise low earth orbit, and we might not do so before we run out of cheap energy) and b) technological singularities.

Re: Our Solar System Isn't Normal

#78

Post by calinet6 »

chc wrote: post #63
asr wrote: post #54

Earlier quoted context omitted.

Agreed. For anyone else who routinely reads comments without reading the article, if this is still the top comment, I'd suggest you just go skim the article. (Aside: I'd guess it's because there are people like me, who often read comments before or without reading the article, that a well-written but not on-point comment like this can get upvoted. I wonder how you'd fix that?)

Well, the obvious answer would be: Track whether a user has clicked on the link and disable the vote buttons until they have.

For pete's sake, can't someone wax poetic on a slightly related subject of interest without it having to be taken as a polarizing direct criticism of the article?

My bad, move along.

Re: Our Solar System Isn't Normal

#79

Post by schiffern »

lutorm wrote: post #57
schiffern wrote: post #6

Earlier quoted context omitted.

Kepler uses occlusion, not wobbling.

True, but occultations are also very biased towards planets with small semimajor axis, because the solid angle that produces an occultation goes roughly as 1/a.

You use "but" as though you're disputing some statement I made, when I intentionally avoided making any statement outside my knowledge. I said Kepler does use occlusion, and does not use wobbling.

I'm not trying to single you out here. I'm just curious what one has to say on HN so as not to be corrected.

Is there some "don't assume I've implicitly made a bunch of unsupported remarks" initialism that I can tack on to the end of all my posts?

/DAIIMABOUR

Re: Our Solar System Isn't Normal

#80

Post by calinet6 »

banachtarski wrote: post #52
calinet6 wrote: post #45

Earlier quoted context omitted.

In most articles investigating how our solar system or planet is different from the others, they take a pop-sci tone (which I may be reading too much into, for sure) about scientists studying why our special planet got this way. That is absolutely true to some degree—we want to find out what conditions support life, and why the Earth did end up how it did, and resulted in conditions stable enough and correct enough t…

This article definitely isn't communicating what you interpreted. Why are your comments about "most articles" relevant?

I never said I was interpreting the article. Can't I just discuss something interesting? Or does it have to be interpreted as an interpretation of the article?
Post reply on HN