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YOU ARE HERE!
FOR STAR TREK
FANS
YOU ARE HERE
THE DISTANCES IN SPACE ARE
AMAZING.
EARTH IS 93,000,000 MILES FROM THE
SUN.
AT THE SPEED LIGHT TRAVELS (186,000
MILES/SECOND OR 6.7 X 108
MILES/HOUR)
SO, IT TAKES 8.3 MINUTES FOR LIGHT
FROM THE SUN TO REACH EARTH.
THE NEAREST STAR TO THE SUN IS 4.2
LIGHT YEARS AWAY. THAT’S
2.5 X 1013 MILES AWAY
OUR GALAXY IS 100,000 LIGHT YEARS
ACROSS.
THAT’S 5.9 X 1017 MILES.
DISTANCES ARE SO GREAT THAT IF THERE
IS INTELLIGENT LIFE ON OTHER WORLDS,
IT WOULD BE HIGHLY UNLIKELY THAT WE
WOULD EVER KNOW.
THEN, IF THERE IS INTELLIGENT LIFE ON
OTHER WORLDS, WHY WOULD IT WANT TO
CONTACT US?
LET’S CONSIDER THE PROBABILITIES.
IN OUR GALAXY, THERE ARE
200,000,000,000 STARS.
SCIENTISTS EXTIMATE THAT THERE ARE
200,000,000,000 GALAXIES.
SO, THAT MAKES 4 X 1022 STARS.
WITH THAT NUMBER, ONE WOULD EXPECT
THAT THERE MUST BE OTHER WORLDS
WITH LIFE.
THEN, ONE MIGHT ASK THE QUESTION,
WOULD IT BE JUST LIKE OUR LIFE?
LIFE EXISTS ON EARTH AS IT IS IN THIS
MOMENT BECAUSE OF A SERIES OF EVENTS.
FIRST, LET’S CONSIDER THE FORMATION OF
THE SOLAR SYSTEM.
“SCIENTISTS ESTIMATE THAT THE DUST
CLOUD THAT OUR SOLAR SYSTEM FORMED IN
WAS AT LEAST 24 BILLION KILOMETERS
ACROSS AND CONTAINED MATERIALS FROM
AT LEAST TWO PREVIOUS GENERATIONS OF
STARS.”
“You Are Here, A Portable History of the
Universe,” Christopher Potter
ONCE THE SUN STARTED TO CONDENSE,
EVENTS HAPPENED RAPIDLY.
IN APPROXIMATELY 100,000 YEARS, THE SUN
CONDENSED AND IGNITED.
99.9% OF THE MATERIAL IN THE DUST
CLOUD WENT TO FORM THE SUN.
THE REMAINING MATERIAL WAS IN A DISC
AROUND THE SUN AND WENT TO FORM THE
OTHER OBJECTS IN THE SOLAR SYSTEM.
AFTER ABOUT 1,000,000 YEARS, THE
REMAINING DUST WAS CONDENSING INTO
PLANETS, MOONS, AND ASTEROIDS.
THE DUST DISK AROUND THE SUN
ROTATED IN THE SAME DIRECTION AND
CONTINUES TO DO SO AFTER IT IS
FORMED INTO PLANETS.
AFTER ABOUT 10 MILLION YEARS AFTER
REACHING FINAL MASS, EARTH IS
STRUCK BY A MARS SIZED OBJECT.
THE TWO IRON CORES MERGE, AND A
LARGE AMOUNT OF THE ROCKY CRUST IS
THROWN INTO SPACE AROUND THE
EARTH.
THIS MATERIAL FORMS THE MOON.
Formation of the moon
THE MOON STABILIZES THE EARTH AND
KEEPS IT FROM WOBBLING ON ITS AXIS.
IF THE MOON DID NOT EXIST, EARTH WOULD
WOBBLE MORE ON ITS AXIS, AND SEASONS
WOULD CHANGE MORE OFTEN AND LESS
PREDICTABILLY.
AFTER ABOUT 500,000,000 YEARS,
BOMBARDMENT WAS ALMOST OVER.
CURRENTLY, THE PROBABILITY OF EARTH
BEING HIT BY A MAJOR OBJECT IS ABOUT
ONCE EVERY 30 MILLION YEARS.
THE PROBABILITY OF BEING HIT BY A SMALL
ONE IS ONCE EVERY 1000 YEARS.
CURRENT NEAR MISSES
From www.spaceweather.com
Asteroid
Date(UT)
Miss Distance
Size
2006 RO36
Jun 18
70.9 LD
1.2 km
2001 PJ9
Jul 17
29.2 LD
1.1 km
2006 BL8
Jul 26
9.3 LD
48 m
2003 DZ15
Jul 29
7.6 LD
153 m
2005 WK4
Aug 9
8.1 LD
420 m
1999 CF9
Aug 23
24.7 LD
1.1 km
2002 JR9
Aug 31
63.5 LD
1.4 km
JUPITER PROTECTS EARTH FROM
BOMBARDMENT, AS WELL.
THE MOON HAS BEEN MOVING AWAY FROM
THE EARTH AT ABOUT 38 MILLIMETERS PER
YEAR, AND, IN TURN, SLOWING DOWN THE
EARTH’S ROTATION.
THEN, THERE IS WATER.
A HUGE AMOUNT OF WATER ARRIVED ON
EARTH EARLY IN EARTH’S HISTORY.
POSSIBILITIES INCLUDE
1) WATER FROM VOLCANOES
2) WATER FROM SMALL COMETS AND
ASTEROIDS
EARTH RECEIVES ABOUT 30,000 TONS OF
WATER EACH YEAR FROM COMET DUST.
“WITHOUT WATER, IT’S ALL JUST
CHEMISTRY, BUT ADD WATER AND YOU GET
BIOLOGY.”
- Felix Franks, Univ. of Cambridge -
LET’S TAKE A LOOK AT HOW CONDITIONS
ON EARTH HAVE SHAPED LIFE ON EARTH.
1) TO GET THE ELEMENTS WE HAVE ON
EARTH, THE MATERIAL THAT FORMED OUR
SOLAR SYSTEM WAS INVOLVED IN TWO
PREVIOUS GENERATIONS OF STARS.
2) COLLISION WITH A MARS SIZED BODY
CONTRIBUTED TO EARTH’S METALLIC
CORE.
3) EARTH’S MOLTEN METALLIC CORE GIVES
EARTH A MAGNETIC FIELD, WHICH
PROTECTS EARTH FROM BOMBARDMENT BY
PARTICLES FROM THE SUN.
4) EARTH’S CORE IS STILL MOLTEN
BECAUSE OF THE HEAT GENERATED IN THE
FORMATION OF THE EARTH AND THE
PRESENCE OF RADIOACTIVE ELEMENTS.
5) THE COLLISION WITH A MARS SIZED
BODY GAVE EARTH A LARGE MOON.
6) THE MOON STABILIZES EARTH AND
KEEPS IT FROM WOBBLING ON ITS AXIS.
THIS GIVES EARTH REGULAR SEASONS.
7) ABOUT 2 BILLION YEARS AGO, BLUE
GREEN ALGAE DEVELOPED IN EARTH’S
OCEANS. THEY PRODUCED OXYGEN AS A
WASTE PRODUCT. THIS LED TO OXYGEN
IN THE STRATOSPHERE, AND, IN TURN,
OZONE.
8) OZONE IN THE STRATOSPHERE BLOCKS
UV RADIATION AND ALLOWED LIFE TO
DEVELOP ON LAND.
9) HAVING JUPITER OUTSIDE OF EARTH’S
ORBIT MEANS THAT EARTH RECEIVES
FEWER COLLISIONS WITH DEBRIES FROM
OUTER SPACE.
10) WE HAVE LOTS OF WATER.
11) OUR CURRENT ATMOSPHERE
REPRESENTS AN EQUILIBRIUM BETWEEN
GREEN PLANTS AND ANIMALS.
WHAT ELSE MIGHT HAVE CONTRIBUTED
TO LIFE AS WE KNOW IT ON EARTH?
ONE BIG FACTOR HAS BEEN THE MAJOR
EXTINCTIONS THAT HAVE OCCURRED.
WE HAVE HAD 5 MAJOR EXTINCTIONS
THAT SCIENTISTS KNOW ABOUT.
EACH TIME AN EXTINCTION OCCURS,
EVOLUTION KICKS INTO HIGH GEAR TO
FILL THE NICHES LEFT VACANT.
EXTINCTION IS THE RULE OF EVOLUTION
AND SURVIVAL THE EXCEPTION.
THE AVERAGE AGE OF A SPECIES IS
ABOUT 4 MILLION YEARS.
WOULD LIFE ON EARTH AS WE KNOW IT BE
AS IT IS IF ALL OF THESE EVENTS HAD
NOT HAPPENED?
DO MODERN HUMANS REPRESENT THE PEAK
OF EVOLUTION?
ASTRONOMERS FINALLY HAVE TECHNIQUES
TO SEARCH FOR PLANETS AROUND OTHER
SUNS, AND THEY ARE FINDING A NUMBER
OF THEM – SOME EARTH SIZED.
IF THERE IS LIFE ON OTHER WORLDS,
WOULD YOU EXPECT IT TO BE SIMILAR TO
WHAT WE HAVE?