Is Earth an Oddball? One of the Strangest Things in the Cosmos Might Be - Us
By: Pat Brennan (SciTechDaily)
Is there another Earth out in the universe, somewhere? We are expending significant resources to answer that question. And we've been told that finding another Earth-like planet will change our understanding of the universe and our place in the universe.
But what if an Earth-like planet isn't found? What if the answer is that our solar system and our Earth are very, very rare - or - even unique in the universe? Finding that the Earth is unique in the universe would be even more profound than finding other rocky planets like Earth.
Those who are searching for Earth-like planets portray lack of success in finding one as 'we don't know' so they can continue searching. The search for knowledge is, after all, never ending. And 'we don't know' always justifies a search for knowledge.
But we do know with certainty is that we have not found another planet similar to our own. At some point we need to ask an important question. Do we recognize and accept our place in the universe using what we do know or using what we don't know?
Earth is the only known planet to possess life in abundance and diversity. What we do know would seem to be far more profound than what we don't know.
S E E D E D C O N T E N T
One of the strangest things in the cosmos might be - us.
Among the thousands of planets confirmed to be in orbit around other stars, we've found nothing quite like our home planet. Other planets in Earth's size range? Sure, by the bushel. But also orbiting a star like our Sun, at a comparable distance? So far it's just one, lonely example. The one beneath our feet.
A big part of this is likely to be the technical difficulty of finding a sister planet. Our telescopes, in space and on the ground, find planets around other stars by two main methods: wobbles and shadows.
The "wobble" method, or radial velocity, traces the subtle back-and-forth motion as orbiting planets tug their star this way, then that, because of gravity. The larger the tug, the "heavier" the planet — that is, the greater its mass.
In the search for shadows, planet-hunting telescopes wait for a tiny dip in starlight as a planet crosses the face of its star — a crossing known as a "transit." The bigger the dip, the wider the planet.
In both cases, large planets are much easier to detect than small ones. And in the case of transits, small, rocky planets about the size of Earth show up much better against very small stars known as red dwarfs. In a sense, they cast a bigger shadow that blots out proportionally more of a small star's light, so instruments like NASA's TESS space telescope can more readily find them. A Sun-sized star won't dim as much when an Earth-size planet passes by, making their transits harder to detect.
And there's another troubling issue: time. A planet orbiting a star at Earth's distance from the Sun would take about 365 days to make one revolution - just like our planet's "year." But to confirm such an orbit, your telescope would have to stare at that star for, say, 365 days to catch even one transit — and to be sure it's truly a planet, you'll want to see at least two or three of these transit signals.
All of these difficulties have placed such planets largely out of reach for today's instruments. We've found plenty of small, rocky planets, but they're nearly all orbiting red dwarf stars.
In our galaxy, red dwarfs are far more common than larger yellow stars like our Sun. That still leaves room for billions of Sun-like stars and, maybe, a significant number of habitable, Earth-sized worlds circling them.
Or maybe not.
Rare or just difficult?
The apparent oddness of our home system doesn't end with Earth. Our particular arrangement - small, rocky worlds in the nearest orbits, big gas giants farther out - also is something we haven't yet detected in close parallel anywhere else. Whether this is because they are truly scarce or because they are hard to detect is unclear.
Jupiter takes one trip around the Sun every 12 years. But Jupiter-type planets in long orbits are comparatively rare around other stars, and that could be important. Theorists say Jupiter might well have cleared the way for Earth to become a habitable world, quite literally. The giant planet's intense gravity could have hoovered up small rocky bits that might otherwise have smashed into Earth, sterilizing it just as life was getting its start.
"The planetary systems we are finding do not look like our solar system," said Jessie Christiansen, a research scientist at NASA's Exoplanet Science Institute. "Is it important that our solar system is different? We don't know yet."
Christiansen, who studies exoplanet demographics, does not think "Earths" will turn out to be rare, but says scientific literature on the question "is all over the place."
Far more data are needed, scientists tell us, to determine the frequency of planets similar to Earth in both size and circumstance.
Future space telescopes could examine the atmospheres of distant, rocky worlds for signs of oxygen, methane, or carbon dioxide - in other words, an atmosphere that reminds us of home.
For now, we remain in the dark. Earth-like planets around Sun-like stars might be plentiful. Or, they could be the true oddballs of the galaxy.
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We know of only one Earth-like planet in the universe. Our Earth. The one and only rocky planet with life in abundance that has been found in the entire universe is the one under our feet.
What we do know, with certainty, should be more important to us than what we conjecture because we don't know. Finding another Earth-like planet won't change the importance of what we already know about our own Earth.
An interesting analogy of our current level of cosmic exploration was to consider the world's oceans as the known universe. Then if you dip an 8oz cup full of that water you will have the analogous amount of space that we have explored.
And even within that cup, our ability to gain deep insight into planets is very limited.
That's another way of saying 'we don't know'. And 'we don't know' always justifies efforts to know.
We make conjectures from what we know. Obviously conjecture is very, very important for acquiring and expanding knowledge. It is possible to acquire knowledge without conjecture but the ability to conjecture greatly speeds the process of acquiring knowledge.
However, we need to remind ourselves that conjecture is not a substitute for knowledge. A well founded conjecture based upon what we do know is still a guess and not knowledge. Conjecture cannot refute knowledge. Knowledge has greater authority and preeminence in decision making than conjecture. And we can't pass judgement on decisions based upon conjecture. What we do know will always be more important than what we don't know.
There isn't a need to question what we know. But conjecture will always require belief simply because we do not know. A scientific conjecture is a statement of belief. Conjecture is not knowledge so we either believe the conjecture or we don't believe the conjecture. If we allow conjecture to become a substitute for knowledge then we will be making decisions based upon belief.
Some believe there are other Earth-like planets in the universe. And some believe that Earth-like planets elsewhere in the universe means there is life elsewhere in the universe. But the only Earth-like planet with an abundance of life that we know is under our feet. Yet we are being challenged to accept what some believe rather than what we know.
You do recognize that we truly do not (yet) know, right?
Yes, Nerm, ergo the 'we do not (yet) know' position.
Who, specifically, is challenging us to accept (implied: as truth) that exolife exists in the universe?
Of course we don't know. But we're learning as we go along.
Conjecture is just a starting point from what we already know, albeit currently quite limited.
It's the start on our path towards knowledge.
Are you sure? Sometimes we discover something that challenges or even changes what we "know." Question everything, especially what we know. But especially what we don't know.
And belief does not equal fact.
See previous statement.
Who is challenging anyone to do that. Given that an Earth-like planet exists in a (presumably) infinite universe, it's possible there might be other earth-like planets. But we still do not know for sure. Yet.
That's what I said.
That's what I said.
But even being the starting point doesn't means conjecture is a substitute for knowledge.
Yep, I'm sure. Conjecture cannot overturn existing knowledge without first being empirically tested and validated. Knowledge always has primacy over conjecture.
Which is only another way of saying conjecture does not equal knowledge; which I've already said.
It's also possible that Earth is the only planet in the universe that hosts life. Just because something is possible, does not mean that it is probable (or improbable).
A possibility is conjecture and not knowledge. And possibilities require belief. The possibility is based upon 'we don't know'. And 'we don't know' always justifies attempts to know. So, we pursue knowledge by starting with a belief.
Heck, in a lot of cases we don't even know enough of what we don't know yet.
The amount of unknown seems to grow as we explore. Just imagine the impact when we discovered particles (beyond the electron). All of a sudden there was a whole new (and counterintuitive) reality below what we thought was an irreducible level.
No one said it is.
I did say we discover something that challenges or even changes what we "know." Hello?
Once again, no one is arguing that. So I'm not sure why you bring it up.
Yes, that is possible. No one said it wasn't.
Given what we already know, it's more probable that exolife exists in the universe than not. But neither are (yet) certainties.
A possibility is mathematical. It's based on what we currently know and understand. Belief is just wishful thinking.
No, we start by asking a question. Belief is for those who want an answer without pursuing knowledge.
My understanding is that rocky planets with plenty of water and vegetation in the "Goldylock Zone" of a star are relatively rare.
They appear to be based on our current knowledge. But we are only on the tip of the most distant hair on the tail of the proverbial elephant.
That is true.
At this time we are the only planet that fits that description. There are however "rocky planets with plenty of water in the "Goldylock Zone" of a star" which are rare, we've just never been able to prove any of them actually have "vegetation" other than earth.
That moon thing, though... Our giant frikkin' moon and the special stabilizing effect it has on our axis, not to mention the tides (really good stuff for the evolution of life). Considering how we think it was made, moons like ours could be rare as hell.
Factor in other stuff like plate tectonics replenishing chemical elements at the surface, and the Jupiter vacuum cleaner effect mentioned in the article, and yeah, truly Earth-like planets might be exceedingly rare indeed. We should probably take better care of this one.
Also, the universe is the wrong scale. The universe is unreachable, so we shouldn't be too concerned about the odds of another Earth in 'the universe'. The galaxy is really all that matters, and reasonably nearby in the galaxy to boot.
Why stop there. Go on to include galactic clusters or even superclusters. One thing is for certain, the universe is a wondrous place.
Not really a big deal, but you may have missed my point. Whether Earth-like planets exist farther away than our local neighborhood in the Milky Way galaxy is practically non-consequential. It won't matter one way or the other if they do, besides simply having something to note in textbooks. We'll almost certainly never be able to reach them – ever.
Excluding the small satellite galaxies orbiting the Milky Way, the next nearest galaxy is Andromeda, which is two million light years away. That's how far away the nearest edge of the rest of the universe is, and it only gets worse after that. The rest of the universe is so far away that it has zero practical relevance to our actual lived reality. It just doesn't matter if Earth-like planets are out there at that distance or not.
Note that the seeded article isn't event bothering with the rest of the universe, it's talking about the galaxy. Do a Ctrl-F search of the page for the word universe and you'll see it six times in Nerm's comment above the seeded article, but not once in the article itself.
Life on Earth appeared rather quickly, seemingly "easily", and has stubbornly persisted despite harsh conditions and several extinction events. I would venture to say that microbial life, at least, likely exists elsewhere in the universe, starting with our own galaxy. This just an opinion, since we'll never know for sure.
We might know for certain some day. All we need do is find one instance and we know.
Finding evidence of microbial life on Mars would be an excellent start. But how will we know about the existence of life beyond our Solar System?
We would need some world-class technology to port automated explorers. That is the stuff of science fiction now but in the distant future who knows what we will come up with?
The key problem is that our universe is so vast that we likely will never be able to explore but a trivial fraction of it. So exolife might exist and we might never know. But, as I noted, just one example and we know.
That would certainly be a huge event.