When the universe turns
April 8, 2009
Commentary: Earth in danger!
When the universe turns bad
by Neil deGrasse Tyson
- - -
In the face of disaster, optimists tend to be grateful
because they easily imagine how much worse things
could have been. Count astrophysicists among them.
When we hear about earthly problems, many of us
think to ourselves, "You have no idea ..."
Worried about something falling on your head as you
walk down the street? We've got something better.
Thousands of asteroids the size of baseball stadiums
- and larger - orbit the sun with trajectories that inter-
sect Earth's path. Eventually, Earth will collide with
every one of them - at impact speeds of at least seven
miles per second.
The smallest of that set are large enough to cause deadly
tsunamis and trillions of dollars of property damage.
[see the link/story following this one for details
on the near-term threat posed by Apophis]
A medium-size asteroid will devastate our culture as it
disrupts food chains, transportation systems, the elec-
trical grid, and the overall stability of what we call civili-
The largest among them - the size of mountains - will
launch an assault on the tree of life that will extinguish
more than half of all land and oceanic species.
Worried about a hole in the ozone layer cased by pollu-
tants? How about no ozone layer at all? Not too far away,
in a neighboring galaxy, lies a prodigious stellar nursery,
birthing stars of all sizes - small ones and large ones.
At the top end of this range are stars that die spectacular
deaths - exploding their guts at staggering speeds across
A particularly deadly subset of these will focus nearly
all their explosive energy into a narrow beam that's bright
enough to be seen across the entire universe. The beam
is so intense with life-hostile UV and X-rays that if it
happens to aim at Earth, the leading edge of this radia-
tion will deplete our protective ozone layer entirely. With-
out this line of atmospheric defense, the radiation that fol-
lows will pass straight through the atmosphere, sterilizing
Worried about falling into a hole in the ground? How about
a black hole in space? If you fell into one of these, you'd
never come out. The very fabric of space and time closes
back on itself, preventing all escape. And as you fell - feet
-first, let's say - the gravity at your feet would rapidly be-
come much greater than the gravity at your head, forcing
your body to stretch beyond comfort - beyond your body's
capacity to remain whole.
Your body would snap, as your lower half separated from
your torso. Each of those two body segments then would
snap into two more pieces, and so forth. But it gets worse.
During your fall, the fabric of space and time gets narrower,
effectively extruding your body parts like toothpaste from
a tube. We call this form of death "spaghettification."
Worried about a fender bender on the highway? Consider
the impending collision between our beloved 100-billion-
star Milky Way galaxy and our nearby cousin, the Andro-
meda Galaxy. These are two beautiful spiral galaxies cur-
rently minding their own business, yet they are hurtling
toward each other through the vacuum of intergalactic
space, with a closing speed of about 400 miles per sec-
We collide in about 6 billion or 7 billion years. Stars will
not likely hit each other directly - space is too empty for
that - but a gravitational free-for-all will ensue, with stars,
and whatever planets orbit them, cast hither and yon in the
cosmic equivalent of a train wreck.
Worried about global warming redrawing Earth's coast-
lines? How about no coastlines at all? In about 5 billion
years, the sun will exhaust its stable supply of hydrogen
fuel. In response, its inner regions will collapse, raise the
core temperature, and ignite helium as the next fuel source.
In the meantime the sun's outer layers will expand prodi-
giously, engulfing the entire orbits of Mercury and Venus.
As the sun continues to grow - as the sun's luminous
surface gets closer and closer - Earth will get hotter and
hotter. The oceans will come to a rolling boil, evaporate
into the atmosphere, and lay bare the ocean floor. Our
heated atmosphere will escape into space, as Earth's
surface becomes a scorched wasteland.
Worried about Earth running out of fuel? The cosmos
shares a similar problem. As the universe expands, the
concentration of energy within it gets weaker and weaker.
Eventually all gas clouds that make stars will have made
all the stars they can. All stars, beginning with the most
luminous ones, run out of fuel entirely. With nothing to
replace them, the stars you see at night begin to blink off
- one by one - as the universe becomes cold and dark
and desolate. The cosmos will indeed end. Not with a
bang, but with a whimper.
Have a nice day.
ABOUT THE WRITER
Neil deGrasse Tyson is an astrophysicist with the Amer-
ican Museum of Natural History. He is author of "Death
by Black Hole," and most recently, "The Pluto Files: The
Rise and Fall of America's Favorite Planet."
- - - end of article - - -
- - -
(originally posted 040109)
- - -
Fortunately, in the present day, humans are
capable of detecting asteroids, and may, if
the need arises, and the asteroid is detected
soon enough, be able to protect the planet
and inhabitants from a devastating impact.
Such is the case with Apophis.
Note -- in a couple of locations in the follow-
ing article, references to myths are included,
but since humankind doesn't believe in myths
any more (well, many humans don't, but in
the case of the surviving myths, like God,
Allah, Satan, jinns, devils, demons, angels,
Shiva, Vishnu, Jesus, Christmas, Easter,
Mohammad, and the rest of the Jewish/
Christian/Islamic/Hindu pantheon of super-
natural beings, many still do), like the god
Apep, the uncreator, or the sun god Ra, or
the number 666 being the mark of the beast,
or biblical end time prophecies, or Friday
the 13th being unlucky, certainly humans
will be delighted when/if it is confirmed that
Apophis has no chance of striking Earth.
On the other hand, if it's determined that
Apophis will pass through the gravitational
keyhole and does have a chance of striking
Earth, I suppose that myth-believers will
view that as reason to believe in whatever
myths they can prop up with that threat.
Neil DeGrasse Tyson - Death By Giant Meteor
Present forecast? -2- excerpts highlight
"In 2029 [Friday, April 13, 2009] , it will
pass within about 18,000 miles of Earth ...
If Apophis passes at 18,893 miles above
Earth, it will pass through a gravitational
"keyhole" about half a mile wide, which
would nudge it just enough to send it on
a course for collision with Earth seven
years later, on April 13, 2036 [Easter Sun-
Date information based on information
in the following article -and- at the fol-
- - -
Flying Up to Meet Asteroids
A proposed NASA mission to intercept an
ill-omened rock in the sky
- - -
Excerpt [with inserts, not part of original
article, in brackets]:
[myths and facts regarding the risk Earth
and its inhabitants face regarding Apophis
on Friday the 13th of April in 2029, and
on Easter Sunday, April 13, 2036]
Partly to help explain solar eclipses, the
ancient Egyptians had a story about the ser-
pent god Apep, the Uncreator, who tried to
swallow the sun god Ra as he crossed the
Apep -- the Greeks called him Apophis --
personified death, destruction and chaos.
His opponent was the goddess Ma'at, who
represented all that was light and truth.
Now, a group of NASA scientists is hoping
Ma'at will once again help humans ward off
the harbinger of destruction.
The MAAT satellite -- Measurement and Anal-
ysis of Apophis Trajectory, a conveniently
descriptive acronym -- is still just an idea.
But if it's built, the modestly priced probe
could help illuminate one of the solar sys-
tem's most famous and most misunderstood
A few months after its discovery in June 2004,
asteroid 99942 Apophis was briefly thought to
pose a serious threat to Earth in either 2029
or 2036. But further calculations showed it
is unlikely to hit the planet, unless it passes
through a gravitational "keyhole" that might
send it swinging Earthward seven years after
its initial visit.
This would be bad, explained David Morrison,
director of the Lunar Science Institute at NASA's
Ames Research Center at Moffett Field, Calif.
Apophis is about 1,000 feet across and roughly
the size of a 25-story building. The 1908 Tun-
guska meteoroid, which caused a massive fire-
ball and flattened a forest in Siberia, was about
10 times smaller and about 1,000 times weaker
in terms of energy. "Where Tunguska would
have destroyed a city, something like Apophis
is rather worse.
It would ruin your whole day," Morrison said.
"That's big enough to destroy a state in the
U.S., or a small country. It's not something
that you would want to sit back and (ignore)."
- - -
[insert -- unmentioned, the fact that if it struck
a large body of water, the resulting tsunamis
would unleash hell on Earth to an area vastly
surpassing the areas flooded in the 2004 post-
Christmas tsunami disaster]
- - -
Thankfully, Apophis is not likely to hit Earth,
but it's worth studying because it comes so
close and there are many other asteroids like
it, Morrison said.
It does seem like a good starting point for
missions to understand these sub-kilometer
asteroids," he said.
As of Saturday, March 21, there were 6,163
known near-Earth asteroids, about 770 of
which are a dangerous half-mile in diameter
or wider, according to the Near Earth Object
Office at NASA's Jet Propulsion Laboratory.
Their paths around the sun occasionally bring
them across Earth's orbit. With enough warn-
ing -- and so long as we know about the aster-
oid's existence, we'd have some warning --
humans could send a spacecraft to a threaten-
ing rock and kick it away by slightly altering
The MAAT probe would be designed to match
Apophis' orbit and tell us if we need to move it.
More cost studies are needed before NASA
has a price tag, but Morrison said the mission
is intended to be relatively inexpensive, around
$100 million. It will piggyback onto a satellite
going up to a geosynchronous orbit, about
18,000 to 22,000 miles above Earth, and con-
tinue until it hooks up with the asteroid.
It won't land or crash, unlike previous asteroid
missions such as Deep Impact, but it will shed
some light on the space rock by flying in forma-
tion with it.
It would carry several cameras, a radio system
and a laser range system to measure the dis-
tance between MAAT and Apophis so scien-
tists can determine the asteroid's mass and
"If we ever face one that will hit us, the first
question they are going to ask is its trajectory.
It's only in Hollywood that asteroids change
orbit. Once you determine the orbit carefully,
then you can predict where it will be in the
future," Morrison said.
Scientists hope a refined understanding of
Apophis' path around the sun will erase linger-
ing worries about its odds of striking Earth.
"It would be nice to have a press conference
and tell you for sure it's not going to happen,"
Scientists' level of certainty has varied wildly
since the asteroid was discovered in June 2004.
That December, observations from some ama-
teur astronomers set off alarms at JPL's Sentry
Around Christmas 2004 -- when most of the
world was reacting to an Earth-based disaster,
the Sumatra tsunami -- the odds of Apophis
hitting Earth in 2029 peaked at 2.7 percent, a
frightening statistical possibility.
The number was soon revised down after a flurry
of observations; as of now, the chances of Apo-
phis hitting Earth in 2029 are about 1 in 45,000.
In 2029, it will pass within about 18,000 miles of
Earth, well within the range of geosynchronous
satellites, but scientists at JPL say its trajectory
won't endanger the satellites.
That's where it gets interesting, however. Earth's
gravity will dramatically affect Apophis' orbit,
leaving scientists to estimate where it will end
If Apophis passes at 18,893 miles above Earth, it
will pass through a gravitational "keyhole" about
half a mile wide, which would nudge it just enough
to send it on a course for collision with Earth
seven years later, on April 13, 2036. MAAT will
provide more data to check these estimates and
tell us whether we should do something to move
Apophis from that keyhole using a solar sail, some
added weight or a space tugboat of sorts. It's also
a way to test a type of asteroid-tracker that might
be really important someday.
We don't know exactly where Apophis is going
to go, but it's very unlikely that it will end up on
an impact trajectory," Morrison said. "But it is a
prototype of the type of object that we might have
to deal with."
Scientists at JPL are confident further observation
will show Apophis will pass about 49 million miles
from Earth on April 13, 2036, which happens to be
That date is one of many numerological coinci-
dences that have helped make the asteroid famous:
For one thing, Apophis is Near Earth Object 99942
-- 999 upside down is 666, the "number of the
beast," a number associated with the end-times
prophecy in the New Testament chapter Revela-
tion. It is expected to pass Earth the first time on
April 13, 2029 -- a Friday the 13th. What's more,
2 + 0 + 2 + 9 = 13.
Feeling unlucky yet? Maybe the probe named for
goodness and light will be able to help illuminate
this dark nomad of the sky.
- - - end excerpt - - -
- - -
Astrophysicist warns of asteroid hitting earth
Story By: Susan Davies
Published Thu Apr 02, 2009, 03:22 PM MDT
Updated Thu Apr 02, 2009, 08:54 PM MDT
- - -
What if space experts determined that an asteroid
was likely to strike the earth. Turns out it's not a
question of "if" but "when."
Astrophysicist Neil deGrasse Tyson is not only
a meteor and planetary expert, he's a host of the
PBS science favorite "Nova."
He says one of the thousands of asteroids orbiting
between Mars and Jupiter is on a course to come
alarmingly close to earth.
Apophis is about the size of the Rose Bowl. It's
predicted to pass between the earth and its com-
munication satellites on Friday, April 13th - 2029.
It will be the biggest thing we've ever seen come
close to earth. Dr. Tyson says it won't hit us, but
if it orbits around on a particular trajectory
- "Threading the keyhole" he calls it, Apophis
will come around and "smack" us seven years
later [on Easter Sunday, April 13, 2036] - if
nothing is done to prevent it.
He says it'll plunge into the Pacific Ocean, create
a huge temporary hole and cause monster wave
after monster wave that will devastate the west
[I wasn't aware that an actual location was even
possible at this point, if the asteroid passes through
the gravitational "keyhole", so I'm unclear what Dr.
Tyson's statement is based on]
Tyson says we can't let that happen. "I don't want
to be the laughing stock of the galaxy and go extinct
as a species because we didn't do something about
Tyson attended the 25th National Space Symposium
in Colorado Springs this week to accept the Douglas
S. Morrow Public Outreach Award.
He says it will take the cooperation of private and
public space agencies and companies, and it will take
funding to solve this challenge. But - he adds - we
- - - end of article - - -