Credit: © ellenamani / Fotolia
Boulder, Colo. — April 2, 2014 — An international team of planetary scientists determined that the Moon formed nearly 100 million years after the start of the solar system, according to a paper to be published April 3 in Nature. This conclusion is based on measurements from the interior of the Earth combined with computer simulations of the protoplanetary disk from which the Earth and other terrestrial planets formed.
The team of researchers from France, Germany and the United States simulated the growth of the terrestrial planets (Mercury, Venus, Earth and Mars) from a disk of thousands of planetary building blocks orbiting the Sun. By analyzing the growth history of the Earth-like planets from 259 simulations, the scientists discovered a relationship between the time the Earth was impacted by a Mars-sized object to create the Moon and the amount of material added to the Earth after that impact.
Augmenting the computer simulation with details on the mass of material added to the Earth by accretion after the formation of the Moon revealed a relationship that works much like a clock to date the Moon-forming event. This is the first “geologic clock” in early solar system history that does not rely on measurements and interpretations of the radioactive decay of atomic nuclei to determine age.
“We were excited to find a ‘clock’ for the formation time of the Moon that didn’t rely on radiometric dating methods. This correlation just jumped out of the simulations and held in each set of old simulations we looked at,” says lead author of the Nature article Seth Jacobson of the Observatory de la Cote d’Azur in Nice, France.
Published literature provided the estimate for the mass accreted by Earth after the Moon-forming impact. Other scientists previously demonstrated that the abundance in the Earth’s mantle of highly siderophile elements, which are atomic elements that prefer to be chemically associated with iron, is directly proportional to the mass accreted by the Earth after the Moon-forming impact.
From these geochemical measurements, the newly established clock dates the Moon to 95 ±32 million years after the beginning of the solar system. This estimate for the Moon-formation agrees with some interpretations of radioactive dating measurements, but not others. Because the new dating method is an independent and direct measurement of the age of the Moon, it helps to guide which radioactive dating measurements are the most useful for this longstanding problem.
“This result is exciting because in the same simulations that can successfully form Mars in only 2 to 5 million years, we can also form the Moon at 100 million years. These vastly different timescales have been very hard to capture in simulations,” says author Dr. Kevin Walsh from the Southwest Research Institute (SwRI) Space Science and Engineering Division.
This research was funded by the European Research Council, as well as NASA’s Astrobiology Virtual Planetary Laboratory, Planetary Geology and Geophysics, Lunar Science Institute and Solar System Exploration Research Virtual Institute programs.
The paper, “Highly siderophile elements in Earth’s mantle as a clock for the Moon-forming impact,” by Seth Jacobson, Alessandro Morbidelli, Sean Raymond, David O’Brien, Kevin Walsh and David Rubie was published in the April 3, 2014, issue of Nature.
For more information, contact Maria Stothoff, (210) 522-3305, Communications Department, Southwest Research Institute, PO Drawer 28510, San Antonio, TX 78228-0510.
The above story is based on materials provided by Southwest Research Institute. Note: Materials may be edited for content and length.
Some of you may recall an article I wrote previously, about a theory that was proposed that said time isn’t an absolute part of the spacetime continuum, or the “fourth dimension,” which it is frequently referred to as — and that the natural world can better be described by removing that part of the equation and thinking of time as a numerical order of change instead. We received a lot of interesting responses to the article. Some of which, were very thought provoking . I wanted to follow up with another radical idea I recently read about that falls in the same category. Except this one postulates that time really is the fourth dimension and it may be disappearing from the universe entirely!
If you’ve been a follower of any number of physics related pages or websites, you’ve probably heard about dark energy — the mysterious “anti-gravitational” force that’s accelerating the expansion of the universe and driving the galaxies away from each other at an accelerated rate. Well, what if we’re looking at it backwards? What if the universe itself isn’t actually expanding an at ever increasing speed, but time is actually slowing down, where it will eventually cease to exist entirely?
Of course, the changes in our everyday life would be minuscule and unnoticeable from the human perspective, but much more visible (and easily measured) in the vastness of the cosmic arena. That’s exactly what the scientists who took part in this study are proposing, including notable names such as: Professor José Senovilla, Marc Mars and Raül Vera, who hail from the University of the Basque Country, Bilbao, and University of Salamanca in Spain. Not only is dark energy dismissed as being preposterous, but the very observation of the ‘accelerated’ expansion of the universe is nothing more than a detailed illusion. (The expansion itself isn’t the illusion, but the *accelerating* expansion part is.) The appearance of the acceleration is due to time gradually slowing, much in the same way a clock behaves when it is equipped with a dying battery.
“If time gradually slows, but we naively kept using our equations to derive the changes of the expansion with respect of ‘a standard flow of time’, then the simple models that we have constructed in our paper shows that an “effective accelerated rate of the expansion” takes place,” says those involved in publishing the paper.
Physicists have been tracking the movement of supernovae explosions seem within the confines of distant galaxies,, which are used to confirm the expansion of the universe is happening at an ever increasing speed. (Amongother things) Using the Doppler effect to see the red-shift in the wavelengths of light emitted from objects that are traveling away from us, astronomers are able to pinpoint and discern how quickly the universe is expanding. All objects shifted towards the red, longer-wavelength are steadily moving away, while objects shifted towards the bluer end of the electromagnetic spectrum are moving towards us (the Andromeda galaxy is an example of this, as it will collide with the Milky Way in an estimated 5 billion years). There’s one problem though — the accuracy of these measurements work under the assumption that time is invariable through all portions of the universe, which would have extreme implications if that were untrue.
So, what does this mean?
Basically, this theory suggests that the fourth dimension of the universe; time — is slowly degrading into a new spatial dimension. If this were the case, the distant stars we perceive as moving away from us at an ever increasing speed are merely giving off that impression that they are accelerating.
“Our calculations show that we would think that the expansion of the universe is accelerating,” says Prof Senovilla. “The theory bases it’s idea on one particular variant of superstring theory, in which our universe is confined to the surface of a membrane, or brane, floating in a higher-dimensional space, known as the “bulk”. In billions of years, time would cease to be time altogether.”
“Then everything will be frozen, like a snapshot of one instant, forever,” Senovilla told New Scientist magazine. “Our planet will be long gone by then.”
Interestingly enough, the idea isn’t entirely hogwash. According to the most accepted model of cosmology that aims to explain the inception of our universe, time itself (along with the other dimensions that comprise the entirety of space/time and all four dimensions) came into being during the big bang. Therefore, it can also disappear — which is just the reverse effect. No need to worry about it happening anytime soon though. In the event that there actually is something to this hypothesis, there is still quite a bit of time left (about five billion years) before the clock strikes midnight for the final time – leaving everything in the universe, including you and I, frozen in the vastness of space forever.
Credit: Jaime Trosper
“Is Time Slowing Down?”
“Countdown to oblivion: Why time itself could end:”
“Time likely to end within 5 billion years, physicists calculate:”
“Across the Universe: From Quarks to Quasar’s previous article about time being an illusion:”
“Model describes universe with no big bang, no beginning, and no end:”
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