Universe Today

A glitch in the Kepler spacecraft's electronics means the space telescope will not have the ability to spot an Earth-sized planet until 2011, according to principal investigator William Borucki. Noisy amplifiers are creating noise that compromises Kepler's view, and the team will have to generate and upload a software fix for the spacecraft. "We're not going to be able to find Earth-size planets in the habitable zone — or it's going to be very difficult — until that work gets done," said Borucki, who revealed the problem last week to the NASA Advisory Council.
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"The square of the orbital period of a planet is proportional to the cube of the semi-major axis of its orbit" That's Kepler's third law. In other words, if you square the 'year' of each planet, and divide it by the cube of its distance to the Sun, you get the same number, for all planets.

(The other two are "the orbit of each planet is an ellipse with the Sun at a focus", and "a line between a planet and the Sun sweeps out equal areas in equal times".)

Copernicus, Kepler, and Newton dealt a one-two-three knockout blow to the idea – thousands of years old – that the Sun (and planets) moved around the Earth. Copernicus put the Sun at the center, Kepler modified Copernicus' circular motions (and provided a simple, quantitative description of the actual motion), and Newton explained how it all worked (gravity).

Kepler worked out his three laws from detailed records of observations of the positions of the planets (known at the time, Mercury, Venus, Mars, Jupiter, and Saturn) – especially Mars – painstakingly compiled by Tycho Brahe.

Kepler's third law (in fact, all three) works not only for the planets in our solar system, but also for the moons of all planets, dwarf planets and asteroids, satellites going round the Earth, etc. Well, not quite; if the secondary body – a planet, say – has a mass that's a significant fraction of the primary one (the Sun, say), then the law needs a small tweak.

By showing how Kepler's laws could be derived from his universal law of gravitation, Newton united heaven and earth, perhaps the greatest revolution in science (OK, Darwin's revolution may be greater). Before Newton, the heavens were thought to work according to rules quite different from the ones which governed things on Earth.

NASA's Imagine the Universe! has a neat demonstration of Kepler's laws, and this PDF file (from the University of Tennessee Knoxville's Maths Department) gives a simple derivation of Kepler's laws, from Newton's universal law of gravitation.

Universe Today articles with more information: Kepler's Laws, Let's Study Law: Kepler Would Be So Proud, and Happy Birthday Johannes Kepler.

Gravity, an Astronomy Cast episode, also discusses Kepler's third law, as does Where is the Center of the Universe?.

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Isaac Newton is arguably one of the most influential scientists in history. Though he lived in the late 1600s, many of his discoveries still affect us in the present. His various theories still hold true even centuries after his death and countless experiments. The scientists able to improve upon his work became famous themselves. Some would say that he was the greatest product of the Enlightenment, the explosion of intellectual knowledge that occurred in his century. So what did Isaac Newton discover?

Sir Isaac Newton’s largest contributions were in the areas of science and mathematics. Newton discovered many of the laws and theories that not only furthered our understanding of the universe, but also gave future scientists the tools to discover how to enter space. He discovered gravitational force and established the three Universal Laws of Motion. By tying these discoveries to the work Johannes Kepler and his Laws of Planetary motion, he established classic mechanics the beginning of modern Physics. This was huge in many ways as he proved definitively the heliocentric model first proposed by Copernicus. He also was the first to propose a set of laws that described the motion of all things in the universe. This served as the basis for our understanding how the universe functions and why it is the way it is. For his time and even now this was a major breakthrough.

His discoveries in mathematics were just as important. He came up with the Binomial Theorem and was one of the two creators of calculus. These discoveries represented a quantum leap in the fields of math and science allowing for calculations that more accurately modeled the behavior of the universe than ever before. Without these advances in math, scientists could not design vehicles to carry us and other machines into space and also plot the best and safest course. Calculus gave scientist the tools to set up a theoretical model of a situation and still account for varying factors. This basic knowledge would help scientist such as Einstein to be able make even greater discoveries such as the Theory of Relativity and Nuclear Fission.

In the end, when we look at Newton's discoveries we must realize that we are looking at one of the core foundations of the modern sciences. Newton opened humanity's eyes to new possibilities and even though his work is over three hundred years old it still helps to guide the advance of technology and our scientific understanding of the earth and the universe around us.

If you enjoyed this article there are others on Universe Today that you will enjoy. There is an interesting article on the Gravitational Constant. There is also a great article on "What is the Universe?"

There are other resources on the internet if you want to learn more about Isaac Newton. This UK site has some great info on his discoveries. You can also check out the PBS website.

You can also check out Astronomy Cast. Episode 44 Einstein's Theory of Relativity is particularly interesting.

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Hollywood never seems to have a shortage of films that harbor the possibility of extraterrestrial life in the Universe. You've got elite blockbusters like E.T., Independence Day, Star Wars, Superman, and more recently – Transformers. And still, we have yet to find stories outside those just borne out of the human mind that show other life forms outside ours do exist.

Drake Equation – The math that says E.T. is out there

In 1961, astrophysicist Dr. Frank Drake came up with an equation showing the astoundingly high probability of finding extraterrestrial life in the Universe. He factored in parameters like the rate of formation of suitable stars, fraction of stars containing planets, number of Earth-like worlds per planetary system, and few others. If the Drake Equation holds, there should be 10,000 planets containing life with the capability of eventually communicating with us.

Fermi Paradox – Why then can't we find them?

There is however a big difference between what the Drake Equation predicts and what we're observing despite all our efforts to communicate with other intelligent lifeforms. This is summarized in what is known as the Fermi Paradox. Some theories have sprouted out of the paradox; among them, that no other civilizations exist or if they did, they just chose not to communicate with us.

Astrobiology – the science that E.T. can call home

Partly due to the overwhelming probability buoyed by the Drake Equation, a new interdisciplinary field has emerged. Astrobiology combines physics, chemistry, and biology plus many other disciplines with the objective of obtaining a better understanding of the origin, evolution, distribution, and even future of life in the Universe.

Kepler – NASA's mission dedicated to finding other Earths

NASA has a number of missions having very specific objectives. One of them is Kepler, a space telescope designed to find planets very similar to our own. Launched just very recently (March 2009), among Kepler's objectives is to scan habitable zones of certain stars for Earth-sized planets and to determine the properties of stars that support orbiting planets.

Terrestrial planet finder (TPF)

Back in 2002, a couple of projects were proposed with the goal of finding certain terrestrial planets. These were the Infrared Astronomical Interferometer (TPF-I) and the Visible Light Choronograph (TPF-C). Budget constraints have put these projects on hold. There are however some inexpensive projects that might just hit the jackpot. One of them is SETI@home

SETI at home

You don't have to be some hot shot astrobiologist to contribute to efforts in finding extraterrestrial life in the Universe. A project called SETI@home allows you to participate by downloading a program into your Internet-connected PC. Once the program is installed, your home PC will form part of a vast network of computers that help in analyzing radio telescope data designed to find other lifeforms.

Here are some related articles from Universe Today that may interest you:

• A New Drake Equation? Other Life Not Likely to be Intelligent
• The Odds of Intelligent Life in the Universe

We have two more related articles from SETI@home and NASA:

• SETI@home
• Kepler Mission: A search for habitable planets

Here are two episodes at Astronomy Cast that you might want to check out as well:

• The Search for Extraterrestrial Intelligence
• The Life of Other Stars

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For the longest time astronomers thought the Universe existed as a perfect sphere; each planet and star following a perfect spherical path. During the early times of the church, the accepted belief was the Earth was the center of the Universe. This would later be disproved by astronomers.

Johan Kepler discovered the elliptical orbit. Kepler was the first person to theorize that the planets actually move in ovaloid orbits. The equation he used to prove this would later become known as the Planetary Laws of Motion and was further supported by Sir Issac Newton's Theory of Gravity. According to Newton, gravity is the reason planets and stars and other celestial objects orbit around each other. The bigger the celestial body, the more mass it can exert on smaller objects around it. One massive body, acting alone would create a circular orbit. If there's more than one massive celestial body, the orbiting object will have have an eccentric or elliptical orbit.

This has many consequences, not on how we observe space but also how navigate it. Other than the threat of running into random objects, gravity is one of the greatest concerns for spaceflight. Normally a planet or some other celestial object has enough mass and speed to avoid being completely pulled into a star's center. But in the case of man made space the difference of size is so great that this danger can't be discounted. To cope with this threat from gravitational fields Aeronautics has come up with two solutions. One is speed. Thanks to advances in rocketry we now have craft that can match the orbit speeds of larger more massive objects in space this helps to reduce the pull of gravity on the craft. We can actually harvest gravity's power. This is known as a gravity assist or gravity slingshot. Due to the elliptical nature of most orbits, There is are two extreme points in the orbit called the apsis. One point is closest to one of foci and the other is farthest away from that same focus. This causes a change in the speed of an object's orbit. The closer it gets the faster it moves the farther it gets the slower it moves. A spacecraft can take advantage of this to boost its speed and escape orbit which also has the added benefit of saving fuel.

If you enjoyed this article there are several others on Universe Today you might enjoy. There is an article on geostationary orbit that you will find very informative. Another article is about the Earth's orbit.

There also other great articles and resources on the web that you can check out. Such as this University of Michigan website. It also has some interesting animation that illustrate elliptical orbits. The University of Indiana website has an interesting orbit calculator you should also check out.

Astronomy cast also has an episode that is pertinent to this article. Be sure to check out the Question Episode on Planetary Orbits

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