A satellite in a high-altitude, geostationary orbit circles the earth once every 24 hours, the same amount of time it takes for the Earth to spin on its axis. The satellite turns anti-clockwise (like our Earth). It stays above the same point on Earth all the time. To maintain the same rotational speed as the Earth, a satellite in geostationary orbit must be 22,237 miles above the Earth. At this distance, the satellite can view a huge portion of the Earth's surface. Because the high-altitude satellite appears to remain fixed in one position (it's really orbiting at the same rate as the Earth turns), it requires no tracking to receive its signal.
Gravity
Gravity is the force that exists between all bodies of mass in the entire universe. It is a pulling force that attracts bodies together. Gravity is the force that keeps us on the earth and stops us floating away into space. The larger an object is, the stronger the force of gravity is. The only exception to this rule is the scientific phenomena, a black hole; in this case an incredibly small point in space has enough gravity to even pull in light. Gravity is the force that causes orbits. A planet or satellite stays in orbit by combining a steady speed with the distance at which it is orbiting. Scientist Isaac Newton first discovered gravity when he noticed how an apple fell to the floor. He then developed theories about the solar system many of which we still use today.
Galaxies
A galaxy is a grouping of millions of stars. There are millions of galaxies in the universe are constantly drifting. Galaxies can be in many different formations from swirls to spherical formations. Most galaxies appear to revolve around a central point; this may be linked with the theory of a black hole at the centre of every galaxy.
Astronomy Project
Ian Burgess
11 1a
Ms Gough
Big Bang Theory
One of the most persistently asked questions has been: How was the universe created? Many once believed that the universe had no beginning or end and was truly infinite. Through the start of the Big Bang theory, however, no longer could the universe be considered infinite. The universe was forced to take on the properties of a finite phenomenon, having both a history and a beginning.
About 15 billion years ago an incredible explosion started the expansion of the universe. This explosion is known as the Big Bang. At the point of this event all of the matter and energy of space was contained at one point. What existed prior to this event is completely unknown and is a matter of pure guesswork. This incident was not a conventional explosion but rather an event filling all of space with all of the particles of the developing universe rushing away from each other. The Big Bang actually consisted of an explosion of space within itself unlike an explosion of a bomb were fragments are thrown outward. The galaxies were not all clumped together, but rather the Big Bang laid the foundations for the universe.
The origin of the Big Bang theory can be credited to Edwin Hubble. Hubble made the observation that the universe is continuously expanding. He discovered that a galaxies velocity is proportional to its distance. Galaxies that are twice as far from us move twice as fast. Another effect is that the universe is expanding in every direction. This observation means that it has taken every galaxy the same amount of time to move from a common starting position to its current position. Just as the Big Bang provided for the foundation of the universe, Hubble’s observations provided for the foundation of the Big Bang theory.
Since the Big Bang, the universe has been continuously expanding and, therefore, there has been more and more distance between clusters of galaxies. This phenomenon of galaxies moving farther away from each other is known as the red shift or The Doppler Effect. As light from distant galaxies approach earth there is an increase of space between earth and the galaxy, which leads to wavelengths being stretched.
In addition to the understanding of the velocity of galaxies emanating from a single point, there is further evidence for the Big Bang. In 1964, two astronomers, Arno Penzias and Robert Wilson, in an attempt to detect microwaves from outer space, accidentally discovered a noise from an extraterrestrial source. The noise did not seem to come from one location but instead; it came from all directions at once. It became obvious that what they heard was radiation from the farthest reaches of the universe, which had been left over from the Big Bang. This discovery of the radioactive aftermath of the initial explosion lent much confidence in the Big Bang theory.
In astronomy, the Doppler effect was originally studied in the visible part of the electromagnetic spectrum. Today, the Doppler shift, as it is also known, applies to electromagnetic waves in all portions of the spectrum. Also, because of the inverse relationship between frequency and wavelength, we can describe the Doppler shift in terms of wavelength. Radiation is red shifted when its wavelength increases, and is blue shifted when its wavelength decreases.
Astronomers use Doppler shifts to calculate precisely how fast stars and other astronomical objects move toward or away from Earth. For example the spectral lines emitted by hydrogen gas in distant galaxies is often observed to be considerably red shifted. The spectral line emission, normally found at a wavelength of 21 centimetres on Earth, might be observed at 21.1 centimetres instead. This 0.1-centimeter red shift would indicate that the gas is moving away from Earth at over 1,400 kilometres per second (over 880 miles per second).
Shifts in frequency do not only result from relative motion. Two other phenomena can substantially the frequency of electromagnetic radiation, as observed. One is associated with very strong gravitational fields and is therefore known as Gravitational Red shift. The other, called the Cosmological Red shift, results not from motion through space, but rather from the expansion of space following the Big Bang, the fireball of creation in which most scientists believe the universe was born.
