Hmm, "Our Milky Way galaxy contains a minimum of 100 billion planets according to a detailed statistical study based on the detection of three extrasolar planets by an observational technique called microlensing."
So we looked in 3 places, found 3 planets and are extrapolating to 100 billion? Surely I would wait for a few more examples?
Edit: Reading the full story, "Of the approximately 40 microlensing events closely monitored, three showed evidence for exoplanets. Using a statistical analysis, the team found that one in six stars hosts a Jupiter-mass planet. What's more, half of the stars have Neptune-mass planets, and two-thirds of the stars have Earth-mass planets. Therefore, low-mass planets are more abundant than their massive counterparts."
The reason it's OK to extrapolate in this way would appear to be in this fact (from TFA):
"Unlike other prominent planet-detection techniques, which measure the shadows of planets passing in front of their stars (transit) or measure the wobble of a star due to the gravitational tug of a planet (radial velocity and astrometry), the gravitational-lensing technique is unbiased in the selection of the host star."
To know more, we have to read the story in Nature, which is here:
Look at the error bars on their percentages. Super-earths (planets of 5-10x earth mass) are present on "62 +35 -37"% of systems. So, your intuition that the extrapolation was shaky is correct.
Assuming the title and your numbers are correct they basically said. 'We estimate that there is a 95% chance that there are 250Billion stars +/- 60% which means there is a 97.5% chance that there are at least 100billion planets.'
However, the actual study costs US$32 so I am not buying it so somewhere in the game of telephone that we just played information could have mutated.
Sounds a little more lonely when you read "it's likely there are a minimum of 1,500 planets within just 50 light-years of Earth." 1,500 isn't that many, and 50 light-years is a really long distance.
We don’t really know how many 1,500 is, because we’re missing a lot of the variables we need to have even an order-of-magnitude estimate of how common intelligent life is. It could be practically inevitable on planets with liquid water; it could be one in a million even given “animal” life. Qualified experts disagree.
And 50 light years is a long distance to travel even at a tremendous speed like 0.01c, but it isn’t that long to send postcards. If we’d sent out a bunch of reasonably good questions in 1912, we would still be interested in the answers today. (More interesting, I think, is what they would ask us.)
In retrospect, I’m assuming we’re taking a finding-intelligent-life perspective here. But if you’re thinking in terms of human expansion – terraforming and so on – then I agree.
More interesting again is what they could tell us. I think with the time scales involved, chances are that anyone communicating with us would be significantly more advanced.
The actual reason is that we have invented radio technology only very recently. Because we are so new to the technology, odds are that our communication partner has had radio for much longer than we have (millions of years probably, given the age of the universe), and thus is far more advanced.
This logical step requires a few assumptions. First is that societies don't destroy themselves soon after the advent of nuclear weapons, which would limit them to a very short window of radio capability (measured in hundreds or thousands of years).
The second assumption is that other forms of intelligence progress their technology at a similar rate to that at which we progress ours.
If the former assumption is wrong, it's extremely unlikely that we will ever talk to any intelligence, even with relatively plentiful life in the universe, because it will kill itself too fast. The latter assumption could still be wrong though, particularly if the method used for interstellar radio communication was in any way evolutionarily derived.
This falls exactly into the scenarios I talked about...
Given how much randomness was involved in our creation as a species, let alone our technological ascendance, it is highly unlikely that other intelligence would develop in exactly the same amount of time elsewhere. It's astronomically unlikely. If they didn't develop at the same time as us, they're either still incapable of radio or have had radio for a long time. A long time in the life of the universe certainly doesn't mean 100 years, it means much longer. Even if it's only 1000 years, if they progress at anything like the rate we do, they'll be massively more advanced than we are.
If a species only has radio for a short period of time (like 200 years) and then disappears or loses it, the odds of overlapping with them are virtually nil (if they die out after getting this far, it says we're much more likely to die out soon too).
And I don't know if they would talk to us before we'd talk to them. Stephen Hawking has a lot to say about why trying to communicate with other civilizations is a bad idea, and they might be smart enough not to try.
If we are significantly more advanced than them, I don't think they'll be contacting us - get me? Thus, if we're being contacted, chances are it's from something ahead of us in development.
The initial poster was talking about a hypothetical question we sent in 1912, meaning we contacted them, and they are communicating with us (they replied). You replied without changing the order of who contacted who.
Globular clusters, or GC, are roughly spherical groupings of from 10,000 to several million stars packed into regions of from 10 to 30 light years across.
"However, they are not thought to be favorable locations for the survival of planetary systems. Planetary orbits are dynamically unstable within the cores of dense clusters because of the perturbations of passing stars."
Some have theorized that the reason we are even talking about this is because we are _not_ in a cluster. We are pretty isolated, life ending events are pretty rare, every 60 million years?
This is unfortunately no joke. Only a fairly primitive technological culture will waste energy and S/N ratio by using coherent signals for communications. Modern radio and TV signals look more or less exactly like static to a receiver that doesn't know what it's listening to, for the same reason that a .jpg or .zip file looks like random data to a program that doesn't know how to decompress it.
So it seems clear that SETI-like efforts will be unlikely to detect any transmissions from civilizations who aren't deliberately trying to talk to us. Only civilizations that occupy the narrow time slice caught between the invention of radio and the widespread adoption of digital computers would be detectable, otherwise.
I keep hearing this argument. But physically traveling there is pretty stupid if you think about it. It's much simpler to set up a communication channel.
Sure it'll have a 50 year latency, but we could easily stream all of youtube (or the entire internet really) to them, and so could they. Assuming they're more advanced and their cameras capture the environment in spherical 3D, we could recreate what it's like to stand on their soil pretty accurately from home.
Besides just browsing their extranet would be amazing in itself.
> Sure it'll have a 50 year latency, but we could easily stream all of youtube (or the entire internet really) to them
Well Eric Schmidt who's probably in a better position to estimate than most, said that Google estimates the internet is made up of 5 million terabytes.
5 million terabytes / 10gbps = 126.8 years
and I very much doubt 10gbps is even remotely achievable over interstellar distances. I don't what kind of data rates are achievable but I would expect it to be extremely slow relative to Gigabit speeds.
I imagine by the time we find extra terrestrial intelligence, 10gbps will be childs play. I HOPE we find some way to use entanglement as a communications mechanism by then, although I don't know if that's even possible.
I wonder if the singularity happens like they say, and we can upload our minds into the computer, if we can send a slow probe to another star with a receiving dish and by the time it gets there, we can just beam our consciousnesses there, with maybe enough know-how to roll up an entirely new world with minimal resources.
On a related note, the number put forth by the study (at least one planet per star, on average) is roughly consistent with Drake's 1961 estimate that half of all stars will have planets, and stars with planets will have 2 planets capable of developing life.
Except, of course, that Drake estimated an average of >=1 habitable planets per star. Still, it's good to see one of his estimates being corroborated.
Drake did no such thing. The Drake equation was not designed to give us an answer as to the number of civilisations out there, but to show us which questions needed to be answered to help us identify candidate search locations.
As an example, the Kepler mission is a direct result of the Drake equation, designed to resolve the first two parameters - fp and ne.
The "Galaxy Song" only specifies that there are a 100 billion stars :-)
For some serious geeky pedantry, it's hard to beat the Wikipedia entry for the song (especially the section entitled "Accuracy of figures quoted in the lyrics"):
It's straightforward math, the hardest part is coming up with a width for China (I ended up using an approximation of 5,000 km), all of the other figures are on wikipedia (radius of Saturn's orbit, size of the milky way). Also, if you want to be super lazy you can get google to convert units for you:
So we looked in 3 places, found 3 planets and are extrapolating to 100 billion? Surely I would wait for a few more examples?
Edit: Reading the full story, "Of the approximately 40 microlensing events closely monitored, three showed evidence for exoplanets. Using a statistical analysis, the team found that one in six stars hosts a Jupiter-mass planet. What's more, half of the stars have Neptune-mass planets, and two-thirds of the stars have Earth-mass planets. Therefore, low-mass planets are more abundant than their massive counterparts."
I dont get it. Any explanation?