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Astronomy

Martin Ratcliffe

2005-04-01 10:50:00

: Over the last several months I have fallen in love with the space and stars. Now I'm looking for a guide, or a map, I don't know which, in order to recognize the stars and constellations. I figure there are some maps on the Internet but I can't find them. If you can help, I'll be very grateful.

ANSWER: There are many ways to begin to find your way around the night sky. Some of the best are monthly charts available in a magazine such as "Astronomy" magazine (found in large city bookstores and large Dillon's stores). I prepare the monthly night sky column and an artist does a wonderful double page map of the night sky for each month. Alternatively you could buy a large planisphere. This device allows you to dial up the current date and time to show a representation of the night sky. Like most star charts they all represent the entire dome of the sky on a flat circular map. The horizon is representing by the outer circle and the point directly overhead lies in the center of the circle. Such displays take some getting used to.One of the finest web-based maps is at http://www.skymaps.com/. Their download section is updated each month with a star map and guide to the more familiar observer of what objects are visible each month, including double stars, nebulas and planets. The best way to begin learning your way around the sky using one of these charts is to identify some of the brighter groups first, like the Big Dipper or Orion. Both are visible in the winter time. Each makes excellent starting points. Start by looking at the brighter stars in each constellation, and then follow the star chart and "star hop" to each star in the group. The first time you do this it will be challenging, but very quickly the sky will become familiar to you in much the same way that the roads in a city you are vacationing in become familiar. Good sky watching.

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Astronomy

Martin Ratcliffe

2003-10-01 11:56:00

: With the beautiful fall evenings, I want to get out and stargaze.  Is there anything special happening in the skies over the next couple of months?

ANSWER: There is a lot happening in the skies over Wichita in the next couple of months. Regular sky watchers keep track of what's happening each month by, for example, reading my column in the widely available magazine, "Astronomy", where I review each month's happenings along with beautifully illustrated star charts. Below I describe two events, Mars, and a total eclipse of the Moon on November 8.    Mars, of course, remains visible throughout the rest of this year, though it will become dimmer as Earth pulls away from the red planet. As nearly everyone knows by now, Mars was at its closest point to Earth on August 27. On that date, it stood 34.6 million miles from Earth, the closest since the Stone Age, some 60,000 years ago. Mars and Earth come fairly close every two years in what is called "opposition". "Opposite to what?", you may ask. It's opposite the Sun in our skies, which places the planet due south at local midnight and at its highest above the horizon, the best time to view any planet. Following the date of "opposition", on August 27 in the case of Mars, the planet moves into the evening sky and is visible after dusk. All planets, stars, moon and Sun rise in the east, so in the early evening during September that is where you found Mars. During October, the planet will be high in the southeast or south. The later in the evening you view, the farther Earth has turned, thus placing the planet farther west (earth turns from west to east causing the sky to move east to west).   Some people may be surprised that Mars is still around, considering the headlines in August like Mars closest TONIGHT!". The impression this headline seems to convey to is that the following day, Mars would zoom off under some previously unknown force never to be seen for a few years. In fact it is us, our planet Earth, that is doing the zooming. We move around the Sun faster than Mars, rather like two cars on a racetrack. The inner one moves faster. Gravity works the same way, and causes the Earth to move faster, and every two years we overtake Mars. We are closest to Mars for a brief moment, then gradually move away, slowly at first, then as we round our orbit, the departure speed appears to increase.    The next big event is the Total Eclipse of the Moon on November 8. This is the second total eclipse of the moon this year, quite an unusual event. However, the first one, on May 15, was clouded out for local Kansans. So let's keep our fingers crossed for November 8. The Moon will rise already eclipsed shortly after 5:30 p.m. Central Standard Time.    As the sky darkens, the Moon crawls into the Earth's shadow. You can see the geometry in action - the Sun has just set exactly opposite where the Moon is rising, and you, on Earth, are in the way, blocking sunlight from falling on the Moon. The Moon will be immersed fully in the shadow at 7:06 p.m. During this total stage, the Moon typically turns a bright orange, comparable to the bright orange color of Mars that will be visible high in the south on the same night. The total stage ends at 7:30 p.m. as the Moon slides away from Earth's shadow. This eclipse is quite short because the Moon is passing through the lower edge of the Earth's shadow.   Look also for the Pleiades (Seven Sisters) star cluster to the left of the eclipsed Moon, and below, the bright star Aldebaran, a red giant star that marks the eye of the Bull in the traditional constellation of Taurus.   You can try to photograph the eclipse using a digital or film camera. Just make sure the camera is firmly mounted on a small tripod for stability. More details about the eclipse can be found on a web site at http://www.mreclipse.com/.   For activities in 2004, I have just completed the annual edition of Astronomy magazine called "Explore the Universe". This special issue reviews the entire year of events next year, and is in its tenth year of publication. Try a local bookstore for a copy, and it can be your guide for the full year. Not mentioned here are meteors showers, Jupiter and Saturn. For those and more, go to Astronomy.com.

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Astronomy

Martin Ratcliffe

2003-04-01 05:59:00

Why is it that something can never actually travel at the speed of light?

Let's begin by explaining what light actually is, and then discuss why we can't travel at the speed of light. It was Scotsman James Clerk Maxwell who, in the 1860's, came up with a set of equations that described electricity and magnetism in one coherent theory. Out of his mathematical theory came a fixed number that was the speed of electromagnetic waves, or light, and thus he managed to explain light as an electromagnetic wave. Light travels at about 670,000,000 miles per hour, or 186,000 miles per second (in a vacuum). 
Maxwell's electromagnetism theory predicted the existence of other electromagnetic waves that all travel at the same speed. It was not until some years later, in the 1880's, that radio waves were discovered. Since then, of course, x-rays, ultraviolet, infra-red and the ubiquitous microwaves have been recognized as different varieties of light and have been put to every day use.  We have much to thank Maxwell for in today's modern society. Such is the power of a real scientific theory in that it predicts what you might discover in the future that has previously been unseen.
One attribute of his theory is that light always travels at the same speed in a vacuum, irrespective of the speed of the object emitting it. While this seems counterintuitive in our unique Earth-bound experience, numerous experiments have shown that the theory accurately describes how light behaves.
Consider a baseball pitcher who fires a baseball at 90 mph from the front seat of a car speeding along at 60 mph. The resulting speed of the baseball would be 150 mph. But, if you are on a spaceship traveling at half the speed of light and you shine a light out front, the light would still travel at the speed of light and not, as you may expect, at one-and-a-half times the speed of light.
Testing this prediction led to one of the most famous experiments of all time, the Michelson-Morley experiment.  At the end of the 19th century, Albert Michelson and Edward Morley set out to find if the Earth's speed along its orbital path around the Sun had any effect on the speed of light. A single beam of light was split and bounced back and forth between mirrors. One set of mirrors was at right angles to a second set, so that one light path was along the same direction as Earth's motion and the other perpendicular to it. If the speed of light varied, the experiment would detect the change, but none was seen.
Enter Albert Einstein. His theory of relativity used Maxwell's idea of a constant speed of light to turn our common sense view of the universe on its head and explain the appearance of the world in a whole new way. Einstein's theory of general relativity (essentially a theory of gravity) shows that light is the one universal constant in the universe.
His theories made many predictions, one of which was that as you approach the speed of light, your mass increases (and your length shrinks). Since it takes energy to accelerate a mass, more and more energy is required to accelerate faster. As you approach the speed of light, your mass increases toward infinity, consequently requiring an infinite amount of energy to accelerate any faster. So the speed of light represents a physical limit in today's universe. But what is more amazing is that Einstein's theory of Gravity (relativity) of nearly one hundred years ago have stood the test of time and have passed every test. Application of his theory has a place in our lives today as our reliance on space-based technology increases.

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Astronomy

Martin Ratcliffe

2002-06-01 17:41:00

Question:  What is 'solar wind'?  How does it work?  How does it interfere with happenings on Earth?

Answer:  Our Sun generates a gale force, supersonic, breeze of particles that travel outward through the solar system at a breathtaking 250 miles per second. Strong storms in this "space weather" from the sun can affect satellites, communications and electrical systems on Earth. Understanding how and why this happens is as important as understanding our earthly weather.The scale of this outflow is staggering, measured at one million tons per second. But don't panic. There is enough material in the Sun to sustain this rate for billions of years. This continuous out-flowing wind comes from the extremely hot outer atmosphere of the Sun that is only visible during a total solar eclipse - called the corona. The wind is packed with charged particles called electrons and protons, the basic building blocks of atoms.Thankfully, due to our planet's magnetic field, this electrically-charged wind flows around us and we remain relatively unaffected, unless, however, there is a solar storm. Solar storms can erupt at anytime, typically from regions of sunspots on the Sun. These blasts from the Sun can affect the Earth directly, pumping energy into our near environment, triggering the northern lights (aurora), inducing electrical bursts in power lines and tripping circuit breakers.Comet tails act as windsocks for the solar wind. Comet tails are formed by the solar wind catching gas flowing from the nucleus of the comet, pushing it farther downstream. Many people experienced this effect first hand in 1997 when they viewed Comet Hale-Bopp. A comet's tail always points directly away from the Sun. Changes in the wind can significantly affect the appearance of a comet tail.You can follow space weather at http://www.spaceweather.com/. Most dramatic are hourly time-lapse pictures of the Sun showing regular outbursts in the solar wind, sometimes targeted at Earth. Following an outburst, the northern lights may be visible about two days later, the normal travel time from the Sun to the Earth for these particles. Normally the northern lights are restricted to the northern latitudes, but occasionally, as in November last year, they are visible from Wichita.  Every Sunday Exploration Place has free public viewing of the Sun through special telescopes that show dramatic arches of gas leaping off the Sun. This summer, on July 28 at 2 p.m., a visiting solar astronomer will speak at Exploration Place about Solar Storms. See http://www.exploration.org/ for further details.