Fun Facts: Universe
"Do there exist many worlds, or is there but a single world? This is one
of the most noble and exalted questions in the study of nature."
- St. Albertus Magnus (ca. 1193-1280)
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.
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
1/100th 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
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.
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.
In the universe, matter is so thinly dispersed that space is
as empty as a building twenty miles long, twenty miles wide, and
twenty miles high that contains 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.
There is a giant supercluster of galaxies in the direction of the
constellations Perseus and Pegasus that is over a thousand million light-years
long, and is the largest supercluster known. In 1989, astronomers
found another structure that they dubbed the "Great Wall". It is a
collection of galaxies some 500 million light-years long, 200 million
light-years wide, and 15 million light-years thick.
There are an estimated 50 thousand million galaxies in the universe,
with the typical galaxy containing 50 thousand million to 100 thousand
million stars. It is estimated that there are 1022 stars in
total in the universe.
The star Betelgeuse, a bright star in the constellation of Orion, is
estimated to have a diameter of around 700 million miles. If it were placed
at the centre of our solar system, it would extend beyond the orbit of Jupiter.
Alpha Centauri, one of the stars in the system closest to the
sun, is never visible in the sky north of about 30° Northern
Latitude. Though it is the third-brightest star in the sky, it
was not seen by the ancient Greeks nor the chief observatories of
the mediaeval Arabs at Cordoba, Baghdad, and Damascus, all located
north of the 30° line.
Information about what has fallen into a black hole is stored on the black hole's event horizon.
Recent calculations by those who study quantum gravity theory and superstrings have confirmed what Stephen Hawking and his collaborators proposed a decade or more ago. Evidently, the information contained in matter that falls into a black hole is by some curious means encoded in the pattern of frozen quantum fields at the horizon. This raises some interesting possibilities that we could resurrect clocks, humans, spacecraft, and whole planets into something like their pristine form if we could magically reverse the in-fall and collapse process. Many believe that this mathematical result means that we have reached a watershed moment in history in understanding the connection between quantum mechanics and gravitation theory. Quantum mechanics deals with statements about the information that we can extract about a quantum mechanical process involving
observation. Now this same information language can be applied to configurations of the gravitational field and space-time itself.
For black holes, distant observers will see only the outside of the event horizon, while individual observers falling into the black hole will experience
quite another "reality." General relativity predicts that for distant observers outside the horizon, they will experience the three space-like coordinates and one time-like coordinate, as they always
For someone falling into a black hole and crossing the horizon, this crossing is mathematically predicted to involve the transformation of your single time-like coordinate into a space-like coordinate, and your three space-like coordinates into three time-like coordinates. Along any of these three former space-like coordinates, they now all terminate on the singularity; you're experiencing them as time-like now. All choices always terminate on the singularity—at least in the case of a non-rotating black hole. The coordinate which used to measure external time now has a space-like character
which affords you some wiggle room, but dynamically, in terms of these new reversed space and time coordinates, you find that no stable orbits about the singularity are possible no matter what you try to do. Without any stable orbits, and the inexorable freefall into the singularity, relativists often refer to this as the collapse of space-time geometry.
There is sound in space. Sound is a pressure wave, and as long as there is some kind of gaseous medium, there is the possibility of forming pressure waves in it.
In space, the interplanetary medium is a very dilute gas at a density of about 10 atoms per cubic centimeter, and the speed of sound in this medium is about 300 kilometers per second. Typical disturbances due to solar storms and "magneto-sonic turbulence" at the Earth's magnetopause have scales of hundreds of kilometers, so the acoustic wavelengths are enormous. Human ears would never hear them, but we can technologically detect these pressure changes and play them back for our ears to hear by electronically compressing them.
Abell 2218. Two lensed images of the same galaxy, the most distant one observed, are circled.
Credit: European Space Agency, NASA, J.-P. Kneib (Observatoire Midi-Pyrénées) and R. Ellis (Caltech)
The most distant galaxy ever observed is estimated to be around 13,000,000,000 light-years away.
Discovered by the Hubble Space Telescope in 2004, it is located behind the galactic cluster Abell
2218, which bends the object's light. It is a small, energetic galaxy whose light that is seen on Earth
now would have set out when the universe was just 750 million years old.
This is the most distant object that can be observed consistently; some ephemeral gamma-ray bursts have been observed that are slightly more distant than this object.
In 1974, Stephen Hawking showed that black holes evaporate. According to quantum mechanics, pairs of virtual particles are constantly being created and then annihilating each other near black holes (as well as everywhere else in the universe). On occasion, one of the pair of particles ends up inside the black hole's event horizon, and so cannot annihilate its pair, which is forced to become a real particle. This results in a slight increase in the total mass-energy of the outside universe, and that mass-energy has to come from the black hole, whose mass-energy is slightly decreased. Eventually (after an incredibly long time for normal-sized black holes) the black hole would disappear in an explosion of particles and energy.
Most of the elements found in the human body originated in stars; we are literally made of stardust.
The Milky Way has a radius of about 50,000 light years.
The oldest galaxies we can see are right next door to us in the present universe. Looking out into space, we see images of galaxies that
become younger and younger the further out we look. We actually see images of the youngest galaxies
in the universe the farther out we look.
If space is infinite, there is nothing on the other side. If space is finite because it has been
bent around upon itself because of gravity, then again there is nothing on the other side of it because there is no seam. It looks like the surface of a smooth ball which represents a piece of flat paper bent upon itself.
Hotter stars emit blue light; cooler stars emit red light.
The closest star we know of that exploded as a supernova is the one
that left behind the Gum Nebula (named for Colin Gum, an Australian
astronomer who discovered it in 1950). The star was only around
1,500 light-years away. At its peak, that supernova may have shone
as brightly as the full moon for several weeks; however, that occurred
11,000 years ago, and the Stone Age humans of the time left no evidence
of what they saw or thought about it.