UNIVERSE FACTS

 

                          UNIVERSE FACTS

Crab Nebula.
Credit: NASA, ESA and Allison Loll/Jeff Hester (Arizona State University)

The brightest astronomical event in historic times was the supernova of 1054, which produced the Crab Nebula. The supernova was far brighter than Venus. It was bright enough to be visible in daylight and to cast a shadow at night. We know of it through the astronomical records of China, Japan, and the Middle East.
Since the invention of the telescope, no supernovae have been observed within our galaxy. Supernovae were recorded in 1572 and 1604, while Hans Lippershey invented the telescope in 1608 and Galileo was the first to turn his telescope skyward in 1609. The telescope was invented in 1608 when spectacle-maker Hans Lippershey's apprentice was playing games. The apprentice was amusing himself with lenses and found a combination that made things seem closer. When Lippershey was shown this combination, he enclosed the lenses at two ends of a tube. The philosopher Immanuel Kant (1724–1804) was the first person to propose that what we now call galaxies lay outside the Milky Way and were indeed galaxies (or "island universes", as Kant called them) in their own right.

Also found in: As late as 1820, the universe was thought by European scientists to be 6,000 years old. It is now thought to be about 13,700,000,000 years old. The Earth is rotating on its axis at a rate of 460 metres per second at the equator, and is orbiting the sun at a rate of about 30 kilometres per second. The sun is orbiting the centre of the Milky Way at a rate of about 220 kilometres per second. The Milky Way is moving at a speed of about 1000 kilometres per second towards a region of space 150 million light years away called the Great Attractor.

Globular cluster M22.
Credit: NASA, ESA, and Kailash Sahu (STScI)

It is possible that many planets in the galaxy may not orbit around stars. Recent work by Kailash Sahu found six gravitational lenses in the star cluster M22 from objects smaller than brown dwarfs, the smallest type of star. Only one gravitational lensing event by a star was found in the same work.

The Large Zenith Telescope (LZT), located near Vancouver, has a mirror made out of mercury. The telescope features 28 litres of mercury in a pan which spins, causing the mercury to assume a parabolic shape. The telescope only cost $500,000, about ¹/₁₀₀^th as much as a similarly-sized telescope with a glass mirror would cost. Its main disadvantage is that it can only look straight up - otherwise the poisonous mercury would spill.

A "light year" is a measure of distance, not time. It is defined as the distance light travels in one year. Light moves at a velocity of about 300,000 kilometres each second, so in one year, it travels about 9,500,000,000,000 kilometres.

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While astronomers used to believe that galaxies were distributed more or less evenly through space, they have now found regions where galaxies are rare or absent. The largest of these regions is located in the direction of the constellation Bootes, and measures more than 300 million light years across.

The matter in the universe is so thinly dispersed that the universe can be compared with a building twenty miles long, twenty miles wide, and twenty miles high, containing only a single grain of sand.

The term "Big Bang" started as a putdown. In the 1940's, there were many competing theories about the nature of the universe. British astrophysicist Fred Hoyle coined the term "Big Bang" as a snide putdown of his competitors, only to have the term find its way into the general consciousness as the description of the correct theory.

A massive star has a shorter lifetime than a less massive star. The more massive a star, the more tightly its gravity pulls it together, the hotter it must be to keep it from collapsing, and the more rapidly it uses up its hydrogen fuel. The reason there are so few really massive stars is that they do not live very long, as little as a million years. For comparison, our sun has an expected lifetime of about 11,000 million years.

According to string theory, the universe has not just three or four dimensions, but eleven dimensions, ten of space and one of time. We do not observe the extra spatial dimensions because they are curled tightly around each other.

It is not possible to hear in space. Because there is no atmosphere in space to conduct the sound, it would not carry. So, the object would make a noise, but it would not carry to any receiver, and no one would hear it.

About 25% of the universe consists of "dark matter", and about 70% consists of "dark energy", leaving only about 5% of the universe visible to us.

The word arctic is derived from the ancient Greek word for bear, arktos. The reason is that the constellation of Ursa Major, the Great Bear, lies in the northern sky.