Astronomers anticipate 100 billion Earth-like planets

Apr 03, 2013

(Phys.org) —Researchers at The University of Auckland have proposed a new method for finding Earth-like planets and they anticipate that the number will be in the order of 100 billion.

The strategy uses a technique called gravitational microlensing, currently used by a Japan-New Zealand collaboration called MOA (Microlensing Observations in Astrophysics) at New Zealand's Mt John Observatory. Their work will appear in the Oxford University Press journal Monthly Notices of the Royal Astronomical Society.

Lead author Dr Phil Yock from the University of Auckland's Department of Physics explains that the work will require a combination of data from microlensing and the NASA Kepler .

"Kepler finds Earth-sized that are quite close to parent , and it estimates that there are 17 billion such planets in the Milky Way. These planets are generally hotter than Earth, although some could be of a similar temperature (and therefore habitable) if they're orbiting a cool star called a ."

"Our proposal is to measure the number of Earth-mass planets orbiting stars at distances typically twice the Sun-Earth distance. Our planets will therefore be cooler than the Earth. By interpolating between the Kepler and MOA results, we should get a good estimate of the number of Earth-like, in the Galaxy. We anticipate a number in the order of 100 billion."

"Of course, it will be a long way from measuring this number to actually finding inhabited planets, but it will be a step along the way."

The first planet orbiting a Sun-like star was not found until 1995, despite strenuous efforts by astronomers. Dr Yock explains that this reflects the difficulty of detecting from a distance a tiny non-luminous object like Earth orbiting a bright object like the Sun. The planet is lost in the glare of the star, so indirect methods of detection must be used.

Whereas Kepler measures the loss of light from a star when a planet orbits between us and the star, microlensing measures the deflection of light from a distant star that passes through a planetary system en route to Earth – an effect predicted by Einstein in 1936.

In recent years, microlensing has been used to detect several planets as large as Neptune and Jupiter. Dr Yock and colleagues have proposed a new microlensing strategy for detecting the tiny deflection caused by an Earth-sized planet. Simulations carried out by Dr Yock and his colleagues – students and former students from The University of Auckland and France – showed that Earth-sized planets could be detected more easily if a worldwide network of moderate-sized, robotic telescopes was available to monitor them.

Coincidentally, just such a network of 1m and 2m telescopes is now being deployed by Las Cumbres Observatory Global Telescope Network (LCOGT) in collaboration with SUPA/St Andrews (Scottish Universities Physics Alliance), with three telescopes in Chile, three in South Africa, three in Australia, and one each in Hawaii and Texas. This network is used to study microlensing events in conjunction with the Liverpool Telescope in the Canary Islands which is owned and operated by Liverpool John Moores University.

It is expected that the data from this suite of telescopes will be supplemented by measurements using the existing 1.8m MOA telescope at Mt John, the 1.3m Polish telescope in Chile known as OGLE, and the recently opened 1.3m Harlingten telescope in Tasmania.

Explore further: Astrophysicists offer new research, tool for identifying habitable zones

More information: The new work will appear in Monthly Notices of the Royal Astronomical Society (Oxford University Press): dx.doi.org/10.1093/mnras/stt318

Related Stories

Image: The Milky Way's 100 billion planets

Apr 26, 2012

(Phys.org) -- This artist's illustration gives an impression of how common planets are around the stars in the Milky Way. The planets, their orbits and their host stars are all vastly magnified compared to ...

Massey scientist's software finds 'orphan' planets

May 19, 2011

Software developed by a Massey University computer scientist and astrophysicist has led to the discovery of free-floating ‘orphan’ planets – once the subject of science fiction. ...

Catch a new planet

Jul 01, 2008

Is there anybody out there? Could the Universe contain lots of other planets like ours? Are there new worlds yet to be discovered?

Recommended for you

Image: Multicoloured view of supernova remnant

16 hours ago

Most celestial events unfold over thousands of years or more, making it impossible to follow their evolution on human timescales. Supernovas are notable exceptions, the powerful stellar explosions that make ...

Ultra-luminous X-ray sources in starburst galaxies

16 hours ago

Ultra-luminous X-ray sources (ULXs) are point sources in the sky that are so bright in X-rays that each emits more radiation than a million suns emit at all wavelengths. ULXs are rare. Most galaxies (including ...

When a bright light fades

16 hours ago

Astronomer Charles Telesco is primarily interested in the creation of planets and stars. So, when the University of Florida's giant telescope was pointed at a star undergoing a magnificent and explosive death, ...

Image: Horsehead nebula viewed in infrared

16 hours ago

Sometimes a horse of a different color hardly seems to be a horse at all, as, for example, in this newly released image from NASA's Spitzer Space Telescope. The famous Horsehead nebula makes a ghostly appearance ...

The Milky Way's new neighbour

17 hours ago

The Milky Way, the galaxy we live in, is part of a cluster of more than 50 galaxies that make up the 'Local Group', a collection that includes the famous Andromeda galaxy and many other far smaller objects. ...

User comments : 42

Adjust slider to filter visible comments by rank

Display comments: newest first

dogbert
1.6 / 5 (30) Apr 03, 2013
By interpolating between the Kepler and MOA results, we should get a good estimate of the number of Earth-like, habitable planets in the Galaxy. We anticipate a number in the order of 100 billion."


A planet roughly earth size and at a distance from its sun which allows liquid water does not magically become habitable. Earth like (habitable) planets must have life to become earth like. A methane/ammonia atmosphere is not earth like.

"Of course, it will be a long way from measuring this number to actually finding inhabited planets, but it will be a step along the way."


We have not found evidence of life anywhere but here. There is therefore no reason to predict that any planets found will be inhabited.

Wishful thinking is fun, but it is not as scientific assessment.
xel3241
4.5 / 5 (24) Apr 03, 2013
@dogbert, Earth once had a "methane/ammonia atmosphere." That is in fact the seed of life; Earth's current atmosphere is the PRODUCT of life.
Telekinetic
2.3 / 5 (27) Apr 03, 2013
Dogbert, your parochial view of this vast multiverse places you in the company of the unscientific, superstitious and fearful. There is already an abundance of evidence that there are advanced civilizations besides our own. Just because the bible doesn't mention them isn't enough of a reason to dismiss the possibility. From a sheer probability perspective, the odds favor life being elsewhere.
Lurker2358
1.7 / 5 (18) Apr 03, 2013
@dogbert, Earth once had a "methane/ammonia atmosphere."


Never seen any proof of that, though there is a lot of conjecture about it in any geology text.

Oh yes, that nassssty geology self-contradiction, whereby Methane is called a fossil fuel on the one hand, yet appears on Titan, a place totally inhospitable to life, in massive over-abundance far beyond any conceivable level that could have ever been made by any life on a single planet.

Lies.
dogbert
2.4 / 5 (17) Apr 03, 2013
xel3241,
Earth once had a "methane/ammonia atmosphere." That is in fact the seed of life; Earth's current atmosphere is the PRODUCT of life.


My point exactly. Without life, a planet with liquid water is not going to be earth like.

Telekinetic,
your parochial view of this vast multiverse places you in the company of the unscientific, superstitious and fearful.


I am neither unscientific, superstitious or fearful. I hope that the universe is full of life. There is just no indication that life exists anywhere but here.

Just because the bible doesn't mention them isn't enough of a reason to dismiss the possibility.


What has the bible got to do with it? Do you base your perception on whether or not the bible mentions something?

The reason I point out that there is no reason to suppose that life is abundant is that we have found no indication that life exists anywhere but here.
Telekinetic
1.9 / 5 (9) Apr 03, 2013
No, you won't find any snake-handlers on Titan.
Steven_Anderson
1.7 / 5 (12) Apr 03, 2013
I believe the universe is large enough and the number of inhabbitable planets are enough so that the probability of intelligent life is almost certain. The problem I see is that we have not yet detected any signs of that life. If it existed I would have expected to see it's technology expanding through the universe at a speed that the laws of physics would allow. As our technology for peering into the universe gets better our probability of finding it goes up, but the more time that passes that we do not detect it the greater the probability that it doesn't exist or that there is a finite end to the technological advancement hyperbolic curve. http://rawcell.com
Telekinetic
1.4 / 5 (10) Apr 03, 2013
The "we" of which you speak have decided to shut themselves off completely from credible evidence that already exists. I mentioned the bible because of previous, irritating debates with you about evolution.
Telekinetic
1.3 / 5 (14) Apr 03, 2013
"The problem I see is that we have not yet detected any signs of that life. If it existed I would have expected to see it's technology expanding through the universe at a speed that the laws of physics would allow." S.A.

Actually, the problem is that YOU haven't seen any evidence. That's not enough to base any conclusion about anything on. There are people; scientists, astronauts, military, public officials, and thousands of witnesses to events that are undeniable evidence, but deniable only by the close-minded.

philw1776
1.6 / 5 (7) Apr 03, 2013
Astronomers get this huge number of "Earthlike" planets by including the most numerous stars in the galaxy, M dwarfs. Problem being that late K and all M stars are so faint that any Earth sized or other planets close enough to unfreeze and have liquid water would be rotationally stopped by huge stellar tidal forces. Imagine worlds where the "sun" is always in the same place in the sky, never changing. Shadows thrown by hills, mountains, trees, whatever keep objects in their shadow in perpetual shade. Huge winds mediate the temperatures from the forever dayside and the ever frozen dark side.

Hardly worthy of the description Earthlike.
Lurker2358
1.3 / 5 (14) Apr 03, 2013
The Earth was believed to have been hit by a Gamma Ray Burst as one of the ancient mass extinctions.

Consider all the other planets which must have been hit by the original supernova and/or GRB, which would greatly alter the definition of "habitable" in the context of whether or not any life that did exist on those planets could continue to exist.

For example, the Crab Nebula explosion will have probably sterilized all the planets for many light years in every direction, and we know that there are closer SN remnants from other recent events

When these things blow up they give off more energy than the Sun supposedly has/will have in it's entire life time. We're talking incinerate planets in neighboring star systems is how powerful the explosions are.

Why doesn't anyone answer the radio? Maybe the answer is that if they ever existed, they are all dead.
zorro6204
2.1 / 5 (7) Apr 03, 2013
As Beavis might say, that's not very much. No, seriously, a tenth of the size of our annual deficit, it's a number you can deal with.

Let's suppose they're correct, and if you accept the Fermi "paradox" (which I do) and therefore discard the possibility of any space-faring beings in our local galactic group, that allows us to say something about the likelihood of life-bearing planets, and planets that at least had the potential of producing intelligent life. It's a manageable number, not something out there near infinity. Factor in the number of times that life nearly was wiped out here, and we may very well be alone in this universe.
eric96
1 / 5 (5) Apr 03, 2013
What we call life is a range of chemicals along an infinite range of chemicals

Our solar system has 2 candidates that can harbor life: Titan & Europa

Titan is the only satellite with an atmosphere & known ongoing chemical factory.

Europa is the only satellite suspected of having an ocean under an ice crust essentially due to its orbit and Jupiter's gravity, combined essentially exerting strong mixing forces which produce friction therefore heat therefore possibly an underground ocean.

For Europa to harbor life, a chemical factory would have to occur within this ocean. The problem is, no satellite can penetrate this ~10km ice crust, & there is no evidence that the planets composition contains significant amounts of other elements. It has no atmosphere, nothing protecting the surface. So Titan is a known chemical factory, & Europa might be.

None of them contain > trace amounts of oxygen, therefore if life exists, it certainly does not flourish.
Yetzederixx
5 / 5 (8) Apr 03, 2013
A planet roughly earth size and at a distance from its sun which allows liquid water does not magically become habitable. Earth like (habitable) planets must have life to become earth like. A methane/ammonia atmosphere is not earth like.


Take a look at what our atmosphere was like in uber ancient times and then state that again...
Yetzederixx
5 / 5 (8) Apr 03, 2013
[p]None of them contain > trace amounts of oxygen, therefore if life exists, it certainly does not flourish.[/p]

Ever hear of anerobic bacteria?

Do people that post here have even a modicum of scientific knowledge?
Shabs42
5 / 5 (5) Apr 04, 2013
We have not found evidence of life anywhere but here. There is therefore no reason to predict that any planets found will be inhabited.

Wishful thinking is fun, but it is not as scientific assessment.


It's all about perspective. You could just as easily say that every single solar system we've visited so far has life, so there's no reason to suspect any of the others don't have it.
Sinister1811
3.3 / 5 (12) Apr 04, 2013
I believe that when they find their first "Earth-like" planet, they may be in for a reality check. If there's one thing that the planets in our own solar system have shown us is that every planet seems to have its own unique qualities. So, they could be Earth-like in some ways, but completely different in others.
nowhere
5 / 5 (7) Apr 04, 2013
Earth like (habitable) planets must have life to become earth like. A methane/ammonia atmosphere is not earth like.


No, a planet is earth like if it is similar to earth at any point in earths history. So a methane ammonia atmosphere planet can be both earth like (as earth was like that) and potentialy habitable (for the same lifeforms that formed on earth during the same timeline).
Anda
3.4 / 5 (5) Apr 04, 2013
The Earth was believed to have been hit by a Gamma Ray Burst as one of the ancient mass extinctions.


Hahahahahahahahaha!!!!!!! Really????? Fuck you Lurker.

I wasn't going to comment viewing the pathetic level of the other comments.
But thank you for make me laugh so much.
alfie_null
4.4 / 5 (7) Apr 04, 2013
A planet roughly earth size and at a distance from its sun which allows liquid water does not magically become habitable. Earth like (habitable) planets must have life to become earth like. A methane/ammonia atmosphere is not earth like.

Indeed. No magic. No Magical Beings. Just a process, which, through science we'll come to understand.
nowhere
5 / 5 (6) Apr 04, 2013
We have not found evidence of life anywhere but here. There is therefore no reason to predict that any planets found will be inhabited.


The fact that we can not check for life does play a major roll in our not finding evidence for it. Even in our own solar system we haven't been able to rule out or confirm extraterrestrial microbes on titan, how do you then expect us to detect them on planets vastly further away? Rediculous.
vlaaing peerd
5 / 5 (5) Apr 04, 2013

Without life, a planet with liquid water is not going to be earth like.


so in order to support life you need life, I think you've overanalyzing the meaning of 'habitable". It's generally accepted that "habitable" is defined by having:
- roughly the temperature in which water remains liquid
- roughly the size of earth / similar gravity
and really nothing more.


..no reason to suppose that life is abundant is that we have found no indication that life exists anywhere but here.

It depends on how you look at it. Consider we haven't even looked remotely outside of our doorstep, the abundance of galaxies, stars and planets and little reason to assume our earth develops in any way differently than any of the other trillion planets, i'd say there's enough reason to assume life.

Some astronomer once said: "it's like scooping a glass of water out of the ocean and based on your sample you conclude there can be no whales in the ocean. We are just scooping up our first teaspoons.
dogbert
1.7 / 5 (12) Apr 04, 2013
Even in our own solar system we haven't been able to rule out or confirm extraterrestrial microbes on titan, how do you then expect us to detect them on planets vastly further away?


I don't. I also don't expect people claiming to be scientific to claim that a planet roughly earth size and having liquid water is "earth like".

Until/unless we find life somewhere else, we have no reason to presume that any planets anywhere but here are earth like.

The article presumes that there are at least 100 billion earth like planets in our galaxy. That is patently absurd. That would require that every planet that is earth sized with liquid water has life and has had it long enough to develop an oxygen atmosphere.

This is a site which supposedly is concerned with scientific issues.
nowhere
5 / 5 (5) Apr 04, 2013
Oh yes, that nassssty geology self-contradiction, whereby Methane is called a fossil fuel on the one hand, yet appears on Titan, a place totally inhospitable to life, in massive over-abundance far beyond any conceivable level that could have ever been made by any life on a single planet.

Lies.


What does your comment even mean? Methane is a fossil fuel, yes. Methane can be produced by other non-biological means, yes. So what? Also titan is ironically one of the few places in our solar system where we may possibly find microbial life, so I wouldn't call it totally inhospitable for life.
Torbjorn_Larsson_OM
5 / 5 (4) Apr 04, 2013
Good thinking on the project, and a fast enough method to pin these numbers.

The Fermi question is not helpful for astrobiologists interested in the frequency of inhabited worlds, since most are expected to have simple multicellular life at best (no energetic large genome eukaryotes) and we know there are plenty of false negatives (EM "silent" intelligent life for most of eukaryote existence).

@dogbert: "Earth-like" has no definition and so should be avoided. But in this case the context clarifies that they mean size (microlensing).

That life is likely frequent in the universe is predicted ("scientifically assessed") in two independent ways from the fossil record: 1) fast, so easy/andor frequent attempts 2) metabolism is phylogenetically derived from alkaline hydrothermal vents, and the energetics is doable; and independently from thermodynamics (RNA strands crystallizes replicators, due to free energy forcing).
Torbjorn_Larsson_OM
5 / 5 (4) Apr 04, 2013
[cont] 100 billion Earth radius planets is indeed the (lowest limit) of the latest estimates, see Kepler et al analyses. That is mainstream exoplanet and astrobiology research, and it is you who appear unconcerned with what it is actually doing.

@Lurker: As you say, that both gases existed early on is derivable from evidence of the early atmosphere. It is also visible in the fossil record, since methane and ammonia metabolism are early traits.

As for methane sources, you confuse that with using it as a marker of life. The project is not about any of that, the question was the atmosphere when life got started.

As for GRBs, there have been signs of them hitting Earth. But they can't be tied to extinctions (as for now), and more importantly after 4 billion years of life we know they aren't likely to wipe out whole biospheres. You are handwaving in an attempt to show that life is rare, but you are just showing how it isn't likely to be.
Torbjorn_Larsson_OM
5 / 5 (4) Apr 04, 2013
@philw: As we all know, and models now have confirmed, tidal lock is not a problem vs habitability as such or even stable habitability for large organisms. See Venus for example, a dense enough atmosphere will distribute heat without gales that flip landers over.

Tides are not "rotationally stopped", that is the whole point. Tides are helpful in most scenarios of chemical evolution and we know they helped when life evolved to live on land.

@eric96: The habitable bodies in our system are more. Mars is routinely included (whether crustal habitability now or surface habitability earlier). Large ice covered bodies like Ceres and many more moons are suspected of having habitable oceans and among them Enceladus is known to have one.
Torbjorn_Larsson_OM
5 / 5 (4) Apr 04, 2013
[cont] As for Europe you are ill informed, it is suspected to convect down oxygen from ice surface UV dissociation. And just the other week it was shown how it likely have a chlorinated ocean like our own, not the sulfurinated one that other bodies are suspected to have. Precisely by having material communicating between the surface (including incoming Io sulfur!) and the ocean.

Similarly for Titan, high atmosphere reactive products like fullerene cages are estimated to deliver a hefty supply of energetic oxygen compounds to the surface.

But oxygen is rather _a problem_ for chemical evolution, so it is good that we suspect both bodies had an initial respite before oxygen delivery to their putative habitable zones. (If you insist Titan has a liquid methane analog to water HZ.) Oxygen appears late on earth, drove a lot of anaerobic species extinct and instead ushered in the modern 3 clades (Archaea, Bacteria and Eukaryotes), and is not a proxy for flourishing biospheres.
Pkunk_
1.6 / 5 (7) Apr 04, 2013
Astronomers get this huge number of "Earthlike" planets by including the most numerous stars in the galaxy, M dwarfs. Problem being that late K and all M stars are so faint that any Earth sized or other planets close enough to unfreeze and have liquid water would be rotationally stopped by huge stellar tidal forces. Imagine worlds where the "sun" is always in the same place in the sky, never changing. Shadows thrown by hills, mountains, trees, whatever keep objects in their shadow in perpetual shade. Huge winds mediate the temperatures from the forever dayside and the ever frozen dark side.

Hardly worthy of the description Earthlike.

But such a world would still be very inhabitable by an advanced civilization. They would have everything they'd need on the sun-facing side - liquid water, constant sun for heat and possibly a functional atmosphere.
TheGhostofOtto1923
1.9 / 5 (9) Apr 04, 2013
not found evidence of life anywhere but here. There is therefore no reason to predict that any planets found will be inhabited
But we have just started looking. Why on earth would you jump to such a conclusion?
I am neither unscientific, superstitious or fearful. I hope that the universe is full of life. There is just no indication that life exists anywhere but here
Ah you've answered my question. You ARE unscientific BECAUSE you are superstitious. And you are only without fear because you have a god to tuck you in at night.

This god tells you not to dwell on unresolved issues because these would make you fearful. He tells you that he already has the answers and he has already told you all you need to know.

What, intelligent life on other planets? If something that momentous were true, your god would have told you all about it wouldn't he? But then he told you about a 6 day creation and a 40 day flood, and we know these things are nonsense.

Science requests your patience.
philw1776
2.1 / 5 (7) Apr 04, 2013
Where did I state that these misnomer "Earthlike" planets would not be habitable because of tidal locking? Although I believe the models are most likely correct that the atmospheres would not freeze out, we should be skeptical of all models that make predictions on extrasolar planets. Our extrasolar planetary system models pre discovery predicted nothing like what we've seen.

I would expect scientists and competent science writers to use the term Earth sized, especially in this context, certainly not Earthlike.
TheGhostofOtto1923
1 / 5 (7) Apr 04, 2013
The problem I see is that we have not yet detected any signs of that life. If it existed I would have expected to see it's technology expanding through the universe at a speed that the laws of physics would allow
One plausible explanation is that any technological civilization quickly evolves into something which has no need to use broadband communication. The more advanced a techno society becomes, the more skilled and judicious it would be with energy usage.

Beyond that, the transition to machine life would mean fewer individuals, less energy expenditure, and a smaller observable presence. This may inevitably result in a singularity.

The galaxy could be dotted with these entities, who are interested in conversing with each other but which have no interest in us whatsoever. They would be very familiar with all the various forms that life could take, and would know very well what our future would be.

At a certain point we could expect civilizations to disappear.
philw1776
1 / 5 (5) Apr 04, 2013
One plausible explanation is that any technological civilization quickly evolves into something which has no need to use broadband communication. The more advanced a techno society becomes, the more skilled and judicious it would be with energy usage.

The galaxy could be dotted with these entities, who are interested in conversing with each other but which have no interest in us whatsoever. They would be very familiar with all the various forms that life could take, and would know very well what our future would be.

At a certain point we could expect civilizations to disappear.


That could well be true but the Fermi quandary requires that every technical civilization does this. It only takes one civilization over the entire galaxy's history to be expansionist to populate the entire galaxy, a process that even at 0.1c would only take 10s of millions of years, less than a single galactic rotation. Any Fermi postulate or aggregation of such must prohibit all expansion scenarios
Moebius
1.5 / 5 (8) Apr 04, 2013
This is no surprise. I've always been sure that planets are common not rare and life supportable planets must be nearly as common. The question of why we haven't heard from anyone yet is baffling. My latest theory is that while life must be common, a technological intelligence, 'intelligent life', must be extremely rare.

And why not? With all the species this planet has created, billions? trillions? Only one has achieved that kind of intelligence and it was lucky to have survived long enough to achieve technology. And luckier still if we can keep it for a significant length of time.
TheGhostofOtto1923
1 / 5 (6) Apr 04, 2013
It only takes one civilization over the entire galaxy's history to be expansionist
Machines have no need to overpopulate.

Our most advanced form of govt, democracy, is based on conflict. It isnt meant to resolve differences of opinion, it THRIVES on them. Natural selection thrives on conflict. Nature proposes alternatives and the fittest wins out.

But we invented Design and there is no reason to expect that any sentience wouldnt also do this. Design doesnt require opposing opinions. Machine life would not NEED to resolve conflict.

A machine singularity would only need peripherals. It would only seek out others of its kind in order to improve its knowledge base. It would be most concerned with conservation and long-term survival, not proliferation.

The formation of such an entity would resemble that of a black hole; an explosion of radiation for a limited time and then silence.

Aristotle said the monarchy was the highest form of govt. He was referring to our Successor.
philw1776
1 / 5 (5) Apr 05, 2013
Color me skeptical about pronouncements detailing just how putative machine societies would behave, especially every single one of them with zero expansionist or other such behaviors. That said, my guess is in agreement with you that if there is/was any machine society it would not follow the same laws as biological societies.
Fleetfoot
5 / 5 (2) Apr 06, 2013
Let's suppose they're correct, and if you accept the Fermi "paradox" (which I do) and therefore discard the possibility of any space-faring beings in our local galactic group, ...


The Fermi Paradox is, as with all paradoxes, only apparent. In fact it tells you nothing more than that, if there is another technologically capable species in the galaxy, they have chosen not to make contact, nothing more. It doesn't bound the problem in any way.

Finding "Earth-like" planets, i.e. similar mass and surface temperature, is a possibility using current technology. Finding planets which can be suspected of actually having life will require techniques for examining the atmospheres of extra-solar planets spectroscopically. Even then, the indications will probably be ambiguous in most cases and open to considerable interpretation. The debate about the implication of finding methane on Mars is a good example.
Strap
5 / 5 (3) Apr 06, 2013
Absence of evidence is not evidence of absence.
Mike Smith
5 / 5 (1) Apr 08, 2013
I think a key parameter is the distance from Earth. If we find a planet that is 20 light years away, it may be habitable but not reachable.

I think anything outside of our own galaxy is just too far away.

Lets say we have 200 years before we completely wreck this planet. Also there will be wars over water so rocket technology may not advance very much.

So I think we have to accept there is simply no other reachable planet for human habitation. There is no next season. If we screw up Earth, we will have to turn out the lights for the human race.
Fleetfoot
not rated yet Apr 09, 2013
Lets say we have 200 years before we completely wreck this planet. Also there will be wars over water so rocket technology may not advance very much.


We have most of the technology we need in the lab but a lot of development is needed. The best propulsion system is the solar sail, it could achieve ~1% of the speed of light. That means a few centuries from one star to the next. The only workable method is self-replicating probes using circumstellar dust.

So I think we have to accept there is simply no other reachable planet for human habitation. There is no next season. If we screw up Earth, we will have to turn out the lights for the human race.


Right, if we're lucky there might be a habitable planet within ten thousand years, but we can access the whole galaxy in ten million.

I think anything outside of our own galaxy is just too far away.


A design capable of working for 300 million years in deep space seems unlikely.
vlaaing peerd
5 / 5 (1) Apr 10, 2013
The question of why we haven't heard from anyone yet is baffling.


Considering the speed of light, the vast amount of distances between stars and nobody in the universe could have heard of us before we started emitting radiosignals somewhere around the 1920's. Adding to it they probably can't return their message faster than C, the area in which we could receive a message is not bigger than 40 lightyears.
- if their civilasation is already capable of sending messages,
- if they really do happen to look in the right direction.
- if they do consider it to be safe to contact an alien civilisation.
- if they do happen to use the same ways of communications, language and other factors that is required for interstellar communication between species.

These are pretty big "ifs" in a small area of 40 lightyears across. So ...IMO it's not really baffling we didn't encounter anyone yet.

Fleetfoot
not rated yet Apr 10, 2013
The question of why we haven't heard from anyone yet is baffling.


Considering the speed of light, the vast amount of distances between stars and nobody in the universe could have heard of us before we started emitting radiosignals somewhere around the 1920's. Adding to it they probably can't return their message faster than C, the area in which we could receive a message is not bigger than 40 lightyears.
- if their civilasation is already capable of sending messages,
- if they really do happen to look in the right direction.
- if they do consider it to be safe to contact an alien civilisation.
- if they do happen to use the same ways of communications, language and other factors that is required for interstellar communication between species.

These are pretty big "ifs" in a small area of 40 lightyears across. So ...IMO it's not really baffling we didn't encounter anyone yet.


You are failing to consider the time between technological races arising in the galaxy ;-)

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.