It is four times longer than the Andes, Rockies and Himalayas combined. Near the surface, Earth has an atmosphere that consists of 78 percent nitrogen, 21 percent oxygen, and 1 percent other gases such as argon, carbon dioxide, and neon. The atmosphere affects Earth's long-term climate and short-term local weather and shields us from much of the harmful radiation coming from the Sun.
It also protects us from meteoroids, most of which burn up in the atmosphere, seen as meteors in the night sky, before they can strike the surface as meteorites. Our planet's rapid rotation and molten nickel-iron core give rise to a magnetic field, which the solar wind distorts into a teardrop shape in space.
The solar wind is a stream of charged particles continuously ejected from the Sun. When charged particles from the solar wind become trapped in Earth's magnetic field, they collide with air molecules above our planet's magnetic poles. These air molecules then begin to glow and cause aurorae, or the northern and southern lights. The magnetic field is what causes compass needles to point to the North Pole regardless of which way you turn.
But the magnetic polarity of Earth can change, flipping the direction of the magnetic field. The geologic record tells scientists that a magnetic reversal takes place about every , years on average, but the timing is very irregular. As far as we know, such a magnetic reversal doesn't cause any harm to life on Earth, and a reversal is very unlikely to happen for at least another thousand years.
But when it does happen, compass needles are likely to point in many different directions for a few centuries while the switch is being made. And after the switch is completed, they will all point south instead of north.
Namesake Namesake The name Earth is at least 1, years old. Size and Distance Size and Distance With a radius of 3, miles 6, kilometers , Earth is the biggest of the terrestrial planets and the fifth largest planet overall. It takes about eight minutes for light from the Sun to reach our planet. A 3D model of Earth, our home planet. Kid-Friendly Earth Our home planet Earth is a rocky, terrestrial planet. NASA has selected a new Earth science mission that will study the behavior of tropical storms and thunderstorms.
Working together, two instruments could open the door for a more efficient, cost-effective way to gather key information for weather forecasting.
This page showcases our resources for those interested in learning more about ocean worlds. Ocean Worlds Resources. Use Chemistry. The Antarctic ozone hole reached its maximum area on Oct.
NASA is looking into whether mixed reality technology could help with repairs and upgrades on the Cold Atom Lab aboard the space station. A vivid aurora is seen over Earth from the International Space Station.
Behold an Aurora Over the Southern Skies. Full Moon Guide: October - November Satellites are producing a deluge of data, so engineers and scientists are setting up systems in the cloud to manage it. A new paper details how the hydrological cycle of the now-dry lake at Jezero Crater is more complicated than originally thought. Researchers will use Webb to observe 17 actively forming planetary systems. The lander cleared enough dust from one solar panel to keep its seismometer on through the summer, allowing scientists to study three big quakes.
As the uranium in rocks decays, it emits subatomic particles and turns into lead at a constant rate. Measuring the uranium-to-lead ratios in the oldest rocks on Earth gave scientists an estimated age of the planet of 4.
Segment from A Science Odyssey: "Origins. View in: QuickTime RealPlayer. Radiometric Dating: Geologists have calculated the age of Earth at 4. But for humans whose life span rarely reaches more than years, how can we be so sure of that ancient date? It turns out the answers are in Earth's rocks. Even the Greeks and Romans realized that layers of sediment in rock signified old age.
But it wasn't until the late s -- when Scottish geologist James Hutton, who observed sediments building up on the landscape, set out to show that rocks were time clocks -- that serious scientific interest in geological age began. Before then, the Bible had provided the only estimate for the age of the world: about 6, years, with Genesis as the history book.
Pettersson's calculation resulted in the a figure of about 15 million tons per year. In the very same paper, he indicated that he believed that value to be a "generous" over-estimate, and said that 5 million tons per year was a more likely figure. Several measurements of higher precision were available from many sources by the time Morris wrote Scientific Creationism. These measurements give the value for influx rate to the Earth of about 20, to 40, tons per year.
Multiple measurements chemical signature of ocean sediments, satellite penetration detectors, microcratering rate of objects left exposed on the lunar surface all agree on approximately the same value -- nearly three orders of magnitude lower than the value which Morris chose to use. Morris chose to pick obsolete data with known problems, and call it the "best" measurement available.
With the proper values, the expected depth of meteoritic dust on the Moon is less than one foot. For further information, see Dalrymple , pp. Some folks in talk. The lunar soil is a very thin layer usually an inch or less of loose powder present on the surface of the Moon.
However, the lunar soil is not the only meteoritic material on the lunar surface. The "soil" is merely the portion of powdery material which is kept loose by micrometeorite impacts. Below it is the regolith, which is a mixture of rock fragments and packed powdery material. The regolith averages about five meters deep on the lunar maria and ten meters on the lunar highlands. In addition, lunar rocks are broken down by various processes such as micrometeorite impacts and radiation.
Quite a bit of the powdered material even the loose portion is not meteoritic in origin. There is a recent creationist technical paper on this topic which admits that the depth of dust on the Moon is concordant with the mainstream age and history of the solar system. In the Abstract, Snelling and Rush conclude with:.
Unfortunately, attempted counter-responses by creationists have so far failed because of spurious arguments or faulty calculations. Thus, until new evidence is forthcoming, creationists should not continue to use the dust on the moon as evidence against an old age for the moon and the solar system. Snelling and Rush's paper also refutes the oft-posted creationist "myth" about the expectation of a thick dust layer during to the Apollo mission.
The Apollo mission had been preceded by several unmanned landings -- the Soviet Luna six landers , American Ranger five landers and Surveyor seven landers series. The physical properties of the lunar surface were well-known years before man set foot on it. Further, even prior to the unmanned landings mentioned above, Snelling and Rush document that there was no clear consensus in the astronomical community on the depth of dust to expect.
So those making the argument do not even have the excuse that such an consensus existed prior to the unmanned landings. Even though the creationists themselves have refuted this argument, and refutations from the mainstream community have been around for ten to twenty years longer than that , the "Moon dust" argument continues to be propagated in their "popular" literature, and continues to appear in talk. See the talkorigins.
In , Chemical Oceanography published a list of some metals' "residency times" in the ocean. This calculation was performed by dividing the amount of various metals in the oceans by the rate at which rivers bring the metals into the oceans. Several creationists have reproduced this table of numbers, claiming that these numbers gave "upper limits" for the age of the oceans therefore the Earth because the numbers represented the amount of time that it would take for the oceans to "fill up" to their present level of these various metals from zero.
First, let us examine the results of this "dating method. One might wonder why creationist authors have found it worthy of publishing. Yet, it is quite common. This argument also appears in the following creationist literature:. Obviously, these are a pretty popular set of "dating" mechanisms; they appear frequently in creationist literature from the s through the late s and can be found on many creationist web sites even today. They appear in talk. They are all built upon a distortion of the data.
A curious and unbiased observer could quite reasonably refuse to even listen to the creationists until they "clean house" and stop pushing these arguments. If I found "Piltdown Man" in a modern biology text as evidence for human evolution, I'd throw the book away.
If I applied the same standards to the fairly large collection of creationist materials that I own, none would remain. Most creationist criticisms of radiometric dating can be categorized into a few groups. These include:. This is perhaps the most common objection of all. Creationists point to instances where a given method produced a result that is clearly wrong, and then argue that therefore all such dates may be ignored. Such an argument fails on two counts:. How many creationists would see the same time on five different clocks and then feel free to ignore it?
Yet, when five radiometric dating methods agree on the age of one of the Earth's oldest rock formations Dalrymple , p. Certain requirements are involved with all radiometric dating methods. These generally include constancy of decay rate and lack of contamination gain or loss of parent or daughter isotope. Creationists often attack these requirements as "unjustified assumptions," though they are really neither "unjustified" nor "assumptions" in most cases.
Rates of radiometric decay the ones relevant to radiometric dating are thought to be based on rather fundamental properties of matter, such as the probability per unit time that a certain particle can "tunnel" out of the nucleus of the atom.
The nucleus is well-insulated and therefore is relatively immune to larger-scale effects such as pressure or temperature. Significant changes to rates of radiometric decay of isotopes relevant to geological dating have never been observed under any conditions.
Emery is a comprehensive survey of experimental results and theoretical limits on variation of decay rates. E2J ucdavis. For the case of alpha decay, [ You will find a simple explanation in any elementary quantum mechanics textbook; for example, Ohanion's Principles of Quantum Mechanics has a nice example of alpha decay on page The fact that the process is probabilistic, and the exponential dependence on time, are straightforward consequences of quantum mechanics.
The time dependence is a case of "Fermi's golden rule" see, for example, page of Ohanion. An exact computation of decay rates is, of course, much more complicated, since it requires a detailed understanding of the shape of the potential barrier.
In principle, this is computable from quantum chromodynamics, but in practice the computation is much too complex to be done in the near future. There are, however, reliable approximations available, and in addition the shape of the potential can be measured experimentally.
For beta decay, the underlying fundamental theory is different; one begins with electroweak theory for which Glashow, Weinberg and Salam won their Nobel prize rather than quantum chromodynamics.
As described above, the process of radioactive decay is predicated on rather fundamental properties of matter. In order to explain old isotopic ages on a young Earth by means of accelerated decay, an increase of six to ten orders of magnitude in rates of decay would be needed depending on whether the acceleration was spread out over the entire pre-Flood period, or accomplished entirely during the Flood. A nice technical summary is given by Sisterna and Vucetich Among the phenomena they look at are:.
While it is not obvious, each of these observations is sensitive to changes in the physical constants that control radioactive decay. For example, a change in the strength of weak interactions which govern beta decay would have different effects on the binding energy, and therefore the gravitational attraction, of different elements.
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