The ocean tides mirror life itself. Their ebb and flow pay homage to the cyclic nature of the cosmos along even the most secluded seashores. But is life itself also ultimately a fluke of the tides?
If so, life may ultimately owe its origins to our serendipitously large moon. The sun and wind also drive the ocean's oscillations, but it is the moon's gravitational tug that is responsible for the lion's share of this predictable tidal flux.
Our current Earth–moon system, according to the prevailing theory of lunar formation, reflects our solar system's early game of planetary billiards, when colliding planetary embryos created entirely new versions of themselves—in the case of our own planet, a disproportionately large natural satellite in close orbit.
It all started some 4.5 billion years ago when, as theory has it, our nascent Earth was blindsided by a Mars-size planetary embryo, believed to have spun Earth into its initial fast rotation of roughly 12 hours per day. The molten mantle thrown into orbit after the catastrophic lunar-forming impact quickly coalesced into our moon. Within a few thousand years, Earth cooled to an object with a molten surface and a steam atmosphere. Life emerged some 700 million years later, or about 3.8 billion years ago.
But four billion years ago a cooling Earth already had an ocean, but remained barren. The moon was perhaps half as distant as it is now, and as a result, the ocean tides were much more extreme.
At an average distance of 235,000 miles (380,000 kilometers), the moon is currently receding from Earth at a rate of 1.5 inches (3.8 centimeters) per year. As it does, Earth's own spin rate is slowing. And, in the process, roughly 1020 joules of gravitational energy is shed into the oceans annually.*
Over the eons, all that energy has had an evolutionary impact.
"The oceans' tidal flow helps transport heat from the equator to the poles," says Bruce Bills, a geodynamicist at the NASA Jet Propulsion Laboratory in Pasadena, Calif. "Without the lunar tides, it's conceivable that climate oscillations from the ice age to the interglacial would be less extreme than they are. Such glaciations caused migrations of animal and plant species that probably helped speed up speciation."
Bills also points out that such tidal heat transfer could have also mitigated climate fluctuations. The problem in determining which "tidal forcing" scenario is correct, he says, is that climate researchers currently lack data spanning extremely long timescales. Even so, Peter Raimondi, an ecologist at the University of California, Santa Cruz, says the tools of evolution are also driven by the tides' influence on these intertidal regions.
"In a rocky intertidal area," Raimondi says, "it's very clear there are strong evolutionary pressures brought on by a changing environment over a short spatial scale. Without our moon, our marine environment would be much less rich in terms of species diversity."
But is the influence of the lunar tides actually responsible for life itself?
If life originated around deep ocean hydrothermal vents (so-called black smokers), then the lunar tides played a minor role, if any, says James Cowen, a biogeochemical oceanographer at the University of Hawaii at Manoa. If, however, life originated in tidal waters, he says, then tidal cycles could have played a major role.
*CORRECTION (4/23/09): An earlier version stated that three terawatts (3 TW) are shed into the oceans annually; 3 TW is the measure of the power dissipated continually.
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Add CommentTidal forces may also have helped break the Earth's crust into tectonic plates, and now keep them in motion. The resulting vulcanism may have been key to creating, and now maintaining Earth's atmosphere, and the 'black smokers' in the deep ocean where life may have originated.
Reply | Report Abuse | Link to thisI have never read anything suggesting that lunar tides help drive plate tectonics, but I can't imagine there isn't some relationship.
How does the recently reported increase in amplitude of the tides, as measured on the west coast, work with the theory that tides should be subsiding?
Reply | Report Abuse | Link to thisInteresting that the article, as interesting a review as it was, does not include the possibility Earth's exceptionally dynamic dynamo and tectonics may, in part, also result from proximity to our large satellite. The barycenter of the Earth-Moon system is not the center of Earth, but ~1/3 its radius, from the surface. The robust magnetic field of Earth, after all, shields the surface from solar wind and solar particle events, with the same atmosphere cited, including the oceans, absorb the energies of most of the HeV cosmic rays.
Reply | Report Abuse | Link to thisIt seems to me the effect of tidal forces upon Earth's internal magma-ocean has not been adequately explored.
This may be a silly question but is there an adjoining set of principles in place to protect the moon from an impact from a large object as I assume there are in place for earth from similar objects.
Reply | Report Abuse | Link to thisSorry to be fussy, but "roughly three terawatts of gravitational energy is shed into pushing around the oceans annually" does not make any sense. Watts are not energy but power, and power annually is meaningless. Scientists are expected to get their measures right and this is the last place I would've thought I would see mistakes like these.
Reply | Report Abuse | Link to thisThe fact that the article is still interesting highlights how speculative it is.
When the Moon formed, it was about one-sixth its present distance from the Earth. Since tidal forces vary as the third power of distance, that would mean that the tides were 216 times as strong as today. That would mean a constant tsunami speeding around the Earth with gigantic waves all of the time.
Reply | Report Abuse | Link to thisThere is nothing new here. Astrobiology books are full of the importance of the moon to the appearance survival and future of life on Earth. Comins wrote a complete book on the subject in 1993 (What if the moon didn't exist? Harper Collins, NY). There is and update in Gale's "Astrobiology of Earth" Oxford U. Press, 2009.
Reply | Report Abuse | Link to this@toddhutch:
Reply | Report Abuse | Link to thisWe could always blame the universal scapegoat: Global warming.
Global warming > Melted glaciers > more water in ocean > bigger waves.
It is very concievable that the warming of the earth is outpacing the recession of the Moon.
Gravitational torque on the moon's slightly out of round shape is believed to hold it in autorotation. The same was believed to hold Mercury in autorotation about the sun until it was discovered that its rotation period is 58.65 days which is 2/3 (0.6667) of its revolution period of 87.97 days. A year is precisely half a day on Mercury since it exposes opposite faces to the sun on each revolution. It has no tilt to its axis and no seasons. One Venus day (117 Earth days) is 2/3 (0.665) of a Mercury day (175.94 Earth days). Now the rotation period of Venus is (243.17 Earth days) which is 2/3 (0.666) of an Earth Year (365.24 days). Moreover Venus is in retrograde rotation and every time it comes directly between the Earth and the sun it exposes the same face toward the Earth, even though exactly five Venus days have elapsed between such conjunctions. Mars is outside of Earth without direct resonances with other planets, however there are 666.8 Mars solar days of 24.6587 hours in a Mars year. It is an extraordinary coincidence that resonances such as these should arise with the terrestrial planets. There is no explanation for them in classical dynamical theory or in theories of planetary formation.
Reply | Report Abuse | Link to thisCurrent theories are based on the assumption of a continuous universe and there is very strong evidence that space and time are discontinuous. For example Zenos arrow would never reach the target if space and time could be infinitely divisible. In 1888 the mathematician Richard Dedekind showed that continuous space is not consistent with irrational numbers. In a discontinuous universe atoms are synchronously projected as a succession of independent space frames linked by light that together define space and time. Universals interact with particulars is such a way that the same ratio of 2/3 crops up, just as it does in quark theory. There is a structural reason for this.
Cyclical motions of suns, planets and galaxies introduce space frame skipping at their centers with respect to the peripheries. This necessarily implicates a small family of quantum forces to compensate and maintain a preponderance of synchronicity in the universe as a whole. For example these retard the rotation of the poles of the sun to 33 days while the equator rotates in 25 days, contrary to traditional physics, and the average is close to the revolution period of the moon about the Earth. The point here is that a discontinuous universe offers a new methodology to celestial dynamics, including earth science and the relation of the moon to the evolutionary process. You can find more in various articles at www.cosmic-mindreach.com, including one entitled Cosmology & System3. That ratio of 2/3 is structurally required by System 3.
Good catch. reminds me of some show I was watching the other day where a someone was recording how much energy could be "captured" using piezoelectric sidewalk and having people walk on it. After the experiment was over, she looked at her meter and said "1500 watts" (not the actual number, but you get the idea). My next thought was, "Watts? Don't you mean joules?"
Reply | Report Abuse | Link to thisMaybe. But getting laid in high school would have been a tougher proposition. Or, is that preposition?
Reply | Report Abuse | Link to thisThough I understand the agruments for the Moon having formed via a proto-planetary collision - like the chemical and, more importantly, the isotopic simularities between Earth and Moon rocks (and vice versa, when compaired to those thought to be from Mars); I still don't buy it. Why couldn't the Moon have formed in the same general vicinity of the proto-stellar/planetary cloud; wouldn't that have also concentrated these specific isotopes in both bodies?
Reply | Report Abuse | Link to thisLook at Tornados - the multiple kind (i've seen as many as six of them orbiting a central 'mother' tornado); why do Scientist have such a hard time with the Idea that proto-planetary 'whorls' could have orbited about one another, like Tornados do?
What we need to settle this question, is a really big space based interferometer! I've written NASA to suggest that we create one by attaching Ion Drives to a half dozen telescopes, then launch them sequentially - in opposite directions! In a few years time, we could have an uber-interferometer - with a base-line of over a quarter lightyear!
This would also allow to use the parallax technoque to make measurements of the distance of Galaxies beyond the 2 MLY limit proscribed by the maximum 'one earth orbit wide' base-line that constrained Hubbles efforts.
But then I'm a True Revisionist; I don't believe in the Big Bang, the Idea that we're (still! Did Copernicus teach us nothing?) in "The Center of The Universe", or the Hubble Constant derived notion of the 'expanding universe' that these other concepts are all based on!!!
Dang Me! I'm just like my Heroes - the Burbiches (I think I'm spelling their name wrong; you know, those persnickety 'anti-hubble constant' heretics at UCSD who wrote the Nucleosynthesis Paper with Fred Hoyle)!!!
Thanks for opening my mind!
ebianchi! It's also been clear to me that tidal forces play a role in Plate Techtonics, though I don't recall reading or being taught about this effect in Oceanography I or II; which I took in High School.
Reply | Report Abuse | Link to thisAnother oft overlooked effect, is that of the Corriolis Effect. I noticed, when I was about 11 (I was born in 65, the same year the Navy released the Ocen Floor Magnetographic Surveys that 'proved' Plate Techtonics), that the Subduction Trenchs along the Eastern Edges of Continents, are always deeper - often to the tune of 20,000 ft. - than those along the Western Edges of Continents. Wittness the South America Trench, at 17,000 ft.; or the Juan de Fuca, off Oregon, at 14,000 ft., versus the Marianas or Japan Trenchs at 35,000 ft +.
This; or so I've postulated to several 'real' scientists (including Walter Alvarez); is the result of the Corriolis Force causing the eastern edges of said continents to 'rise up' over the plate that's being subducted - just like a ball being whirled about on the end of a string tries to fly off in a straight line!
Since I intend to pursue a 'post-disability' PhD, I've been scolded for 'blowing' a potential Masters Thesis Subject; but I just can't help but put this kind of thing out there - the Internet is just too much FUN!
Maybe they'll give me a MacArthur Grant!
I find it amusing how scientists get excited on the way tidal gravitational forces helped establish DNA, a massive code, coding for 20 bit information in 64 bits. And in additon how they get so excited about Europa because it has water and tides. If Life was so easily formulated, we should be able to synthesize it in a test tube-yet we cannot. Is there life on Europa? No. Is there a chance I am wrong? Sure. About a trillion trillionths of one percent chance.
Reply | Report Abuse | Link to thisA piezoelectric sidewalk would convert joules into watts.
Reply | Report Abuse | Link to thisIf we had two moons, would life have evolved quicker?
Reply | Report Abuse | Link to thisEhhh...
I don't think it could be 3 terra joules, that wouldn't be that much either. I wonder what they meant.
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