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Earth - moving the orbit


Science fiction? Apparently not. When the Sun begins to evolve from its current state it will grow in size and that could be serious for the Earth. So why not try and move the Earth further away from the Sun?


Check out this CNN news report from 2001:


"A group of astronomers has come up with a plan they claim will save life on Earth from an early death. All it takes, they say, is to move the planet into a different orbit.


Their deadline is about 3.5 billion years in the future. At that time, the scientists say, the Sun will be 40 percent brighter than it is today and the Earth will be too hot to sustain life. Even looking just a billion years down the road, the increased brightness of the Sun would cause a "moist greenhouse" effect which will have a catastrophic impact on the planet.


But what if the Earth could be moved farther away from the Sun before it gets too hot for human life?


Researchers Don Korycansky of the University of California-Santa Cruz, Gregory Laughlin of NASA, and Fred Adams of the University of Michigan say the idea of changing the Earth's orbit is almost,"alarmingly feasible."


The scientists' theory is outlined in a paper entitled"Astronomical engineering: A strategy for modifying planetary orbit." The paper has been accepted for publication in the journal "Astrophysics and Space Science."


The researchers' theory is a twist on the "gravity-assist" technique used to send spacecraft to the outer planets. The team says that by shooting a large object (such as an asteroid about 62 miles across) past the Earth, the planet could be gradually pulled away from the Sun. It would take thousands of encounters to make a difference. One million encounters would move the Earth out 41 million miles, or about 50 percent farther from the Sun than it is today.


But the researchers say that if the technique is repeated an average of every 6,000 years, the orbit could be increased to keep pace with the Sun's increasing brightness. The result, they say, would be to keep the Earth habitable for up to an extra 5 billion years.


The scientists say their plan is not without some drawbacks. In order for this method to work, the asteroid would have to pass by Earth within about 10,000 miles. If the asteroid comes too close,it might break up or conceivably even slam into Earth."


Earth - The Planet


Image of the Earth taken from Apollo 11This is a famous Apollo 11 image of Africa & Europe


We now know that there are more than just the nine planets of our Solar System. Thanks to bigger and better telescopes and observing techniques, we have been able to observe planets orbiting distant stars. However the Earth is still very special. It's our home and the only planet, we know of, to contain life. This has been made possible for advanced forms of life by just a few things:


Temperature - the Earth exists in what is known as a 'comfort zone'. If we were any closer to the Sun then we would boil, if we were any further out from the Sun then we would freeze.


Water - most living organisms on the planet require water and we have it in large quantities. Over two-thirds of the planet's surface is covered in water (H2O).


Carbon Dioxide - this has been produced by volcanic activity and the combustion of fuels. Carbon Dioxide (CO2) is vital for plants to survive. They require it to photosynthesise. Without CO2 there would be no plants and without any plants there would be no animals, including us!


Oxygen - animals need oxygen (O2) to breath. Without it they wouldn't exist. Plants produce oxygen as a waste product of photosynthesis.


Is Earth unique? Does life exist on other planets? Who knows? Here's an interesting thought though. There are one hundred thousand million stars in our galaxy (called the Milky Way) and there are probably ten thousand million galaxies in the universe. That's a lot of stars. Someone once said that for every grain of sand that exists on Earth there are a million stars out there! Surely with all of those stars there must be one similar to ours with a planet similar to Earth going around it?




Image of a total eclipseThe total or partial covering of one celestial object by the shadow cast by another object. Viewed from Earth, a solar eclipse occurs when the shadow of the Moon falls on part of the Earth (the Moon moves in front of and eclipses the Sun) and a lunar eclipse occurs when the shadow of the Earth covers the Moon (the Moon falls in the shadow of the Earth).



How many eclipses are there in a year? Because of the way the Earth orbits the Sun and the way the Moon orbits the Earth, eclipses are not just random events, they are predictable and there is a minimum and maximum number that can occur in any one year. Remember a solar eclipse does not have to be 'total' it can be partial or annular.


The maximum number of eclipses that can occur in a year is 7 - either 5 solar and 2 lunar or 4 solar and 3 lunar.


The last year with a total of seven eclipses in it was 1982. There were four partial eclipses of the Sun on January 25, June 21, July 20 & December 15. There were also three total lunar eclipses on January 9, July 6 & December 30.


The next time seven eclipses will occur in one year is 2038. There will be four penumbral lunar eclipses on January 21, June 17, July 16 & December 11. There will also be three solar eclipses on January 5 (annular), July 2 (annular) and December 25-26 (total).


BrainiacRemember, these general limits don't tell us whether any of the solar eclipses will be total or not. Total eclipses are much rarer than partial eclipses, and it's a good approximation to say there will be about one per year. Of course statistics being what they are, 'about one a year' can actually mean either 0, 1 or 2 in any particular year!


Find out more about solar eclipses




The plane of Earth's orbit around the Sun. The rotation axis of the Earth (pole to pole) is at an angle of 23 degrees to the ecliptic - that's what gives us seasons.




Extreme-ultraviolet Imaging Telescope. A telescope on board SOHO which obtains images of the Sun at four ultraviolet wavelengths. Many of the pictures featured on these web pages were taken with the EIT.




EISCAT array


European Incoherent SCATer radar. An array of radio dishes in Scandinavia which studies the ionosphere using radar. The dishes send radar signals up to the ionosphere and receive the signal which is scattered back from the electrons in the ionosphere. The signal received back on the ground can then be used to determine the temperature, density and movement of the electrons in the ionosphere.


Electromagnetic Radiation


Light we see is one kind of electromagnetic radiation - it has a special range of wavelengths that our eyes can respond to. In general, electromagnetic radiation is given different names depending on its wavelength. For instance we call very short wavelength radiation "gamma radiation" and very long wavelength electromagnetic radiation "radio waves". Electromagnetic radiation travels through the vacuum of space at the "speed of light" - approximately 300,000 km/s.



This image shows how the eye interprets changing wavelength as a change in colour. The wavelengths shown are not perfectly to scale; the wavelength of green in the diagram is magnified by about a factor of 100,000.

The name electromagnetic radiation comes from the fact that this type of radiation is a combination of varying electric and magnetic fields.



Is it just coincidence that our eyes see these wavelengths? No, our eyes have evolved to be sensitive to the most useful wavelengths in our environment and that means the wavelengths there is most of. Because the Sun's surface temperature is about 6000 oC it emits most of its radiation in the wavelengths 300 - 600 nanometres.


There is a law of physics that describes how the brightest wavelength of light emitted by an object is related to its temperature. The law is called Wien's displacement law and states that the wavelength at which material emits most radiation is inversely proportional to its temperature in kelvin (as the temperature increases, the wavelength decreases). In other words, the hotter something is, the shorter the wavelength of its peak emitted radiation. You've no doubt seen this effect in operation.


BrainiacAs a piece of metal heats up, you can first feel it (long wavelength infra-red radiation, then see it as red hot (coming into visible wavelengths) and finally white hot (which is how the eye interprets a combination of all visible colours because the blue end of the spectrum is now included). Molten steel always appears 'white' hot, where as fires glow orange-red.


Electromagnetic Spectrum


The entire range of wavelengths of electromagnetic radiation, including (from short to long wavelengths) gamma rays, X-rays, ultraviolet, optical (visible), infrared, and radio waves.




The image above shows the whole range of electromagnetic radiation.


Find out more about the Sun's spectrum in the solar fingerprints section




A negatively charged particle that normally orbits the nucleus of an atom. Electrons were discovered by J J Thompson in 1897 in Cambridge. When separated from the nucleus of an atom an electron is usually known as a beta particle. Electrons travelling in a conducting material also form an electric current. In the Sun's corona there are plenty of 'travelling electrons'. They don't have anything to travel in - except space but they still form an electric current!


Elementary particle


The name given to the fundamental building blocks of nature. The study of them would at one time have been the study of atoms but now it’s the study of the particles that make up atoms (protons, neutrons, electrons) and the things that make up them.


Emission Line


A bright section of a spectrum at a particular wavelength. Usually caused by radiation emitted by a hot gas or plasma. See absorption line for more details.




Image showing the different types of energy


Energy is the ability an object has to do work. Energy is never created or destroyed. It is just transferred from one form to another and there are many forms of energy. Energy is measured in joules.




The great circle on the surface of a body formed by the intersection of the surface of the body and the plane passing through the centre of the body at right angles to the axis of rotation. Phew! Or more simply perhaps it’s ‘the line around the middle' of a sphere!




The European Space Agency - the European equivalent to NASA.





Energetic and Relativistic Nuclei and Electron experiment. Instrument on board SOHO which analyses high energy nuclei and electrons in the solar wind.


Exa (E)


Prefix indicating 1018 or 1,000,000,000,000,000,000 of something.


Examples are that a light year is about a one hundredth of an exametre and the age of the universe is about one half of an exasecond - obviously!


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