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Lightning strikes giraffes,  Contrails, Cosmos future

Q: Do giraffes get struck by lightning? --Amy, Phoenix, AZ

[Corel] Lightning can strike the tallest animal

A: Yes, they do, especially in lands where frequent thunderstorms visit. A game reserve in South Africa is such a spot. Unusually high concentrations of dolomite rock draw 15 lightning strikes a month. In 1996, lightning struck and killed an 18-foot tall giraffe (5.5 m). He was standing on a hill in the Rhino and Lion Reserve in northeastern South Africa. A year later lightning electrocuted his mate. Shortly afterwards, lightning struck and injured a young giraffe in the park. Consequently, the reserve sold its last giraffe in 1998 and turned down more.

"I refused the last offer point blank, primarily because this is not giraffe country, but also because of the lightning problem. There is absolutely nothing we can do to protect giraffes," Kelly Pera, reserve manager told the South African Sunday Times.

Giraffes do nothing to protect themselves either, says Spook Skeleton, wildlife photographer.

Lightning did not strike other reserve animals, not even the 6-foot tall white rhino. However, the giraffe is much taller and the reserve has few tall trees. So, giraffes are vulnerable because of their height.

We humans know better than to stand on a hill in the middle of a thunderstorm and be the tallest thing around. But the poor giraffe probably didn't. So, behavior can increase the odds of a giraffe being hit. Probably the biggest factors, though, are geography and climate.

Wild giraffes presently range across the dry savannah and semi-desert south of Africa's Sahara--wherever trees grow. That must be a saving grace. In its natural home, the giraffe is not the tallest thing around. Trees are. What's more that region sees few lightning strikes (less than one cloud-to- ground flash per square kilometer per year), says Hugh Christian, Chief Scientist for NASA's satellite lightning detection system, which covers Earth.

Further Surfing:

GIRAFFE, Giraffa camelopardalis photography and facts

Sunday Times: The game is up thanks to lightning at reserve

Global Hydrology and Climate Center: Observing lightning from space

NOAA: Interesting facts, myths, trivia about lightning

Planet Ark: Brasilia zoo shows off latest member of giraffe family

Q: Why do jets leave white streaks in the sky? Diane, Brinson, Georgia

[NASA] Contrail, up high

A: The streaks-- aptly named "contrails", which stands for "condensation trails"-- are engine-made clouds. Water vapor from the turbulent jet-engine exhaust, or even from a high-flying piston-engine plane, condenses immediately as it leaves the plane and hits cold air. The trailing cloud is much like the one you make when you breathe out on a cold day and "see your breath".

Down lower, in warm moist air, the plane, plowing through the air, will drop the pressure behind its wings and propeller enough to condense water. Once again, a cloud forms, only, this time, behind the wing tips and propeller. The DC 10, in particular, makes such clouds on take off and landing.

Further Surfing:

USA Today: Evaporation and condensation

University of Wisconsin: Contrails

Jay Reynolds: A journey through the labyrinth

Q: What's going to happen to the Universe? Will it keep expanding forever or will it stop one day and converge back to a speck for another Big Crunch/Big Bang? --Tony D.

A: Last week, we answered a question about how preposterously the Universe began. This week we continue the answer with how the cosmos evolved and its future. Next week we will discuss recent discoveries that verify all this theory.

[NASA / A. Riess] This chart shows the composition of the cosmos--95 % is unknown! We know the basic framework of the cosmos but are sketchy on the details. Click for bigger image.

The Universe is infinite and will keep expanding forever. Matter, however, will not thin to nothing. Ours is a flat Universe, which means that two parallel light rays will stay parallel forever. (Isn't that nice? Space is not curved. The Euclidean geometry you studied in school holds for space.) Parallel rays neither converge nor diverge as they would if the density of space were larger or smaller than it is. The Universe has the critical density necessary for it to simply expand.

Now wait a minute. We've found only enough ordinary matter (stars, planets, cabbages, and kings...) to account for 5 % of the matter we need to get a flat Universe. Where's the rest come from? We know it's out there because we can detect its gravitational pull on objects and even on light. For example, five to ten times more matter exists in large clusters of galaxies than we can account for simply by counting the stars and measuring the gas we find.

We call the unknown matter dark matter since it doesn't emit enough energy (like stars do) for us to detect. Some of the matter might exist in brown dwarf stars that are too dim for us to see. (Related: definition of dark matter and brown dwarf stars. ) However, most of dark matter is truly strange, unknown stuff. We don't know what we're looking for. Yet, it makes up 30 % of the Universe.

Another thing: why is space expanding anyway? Shouldn't gravity pull it together instead? That's a puzzle, all right. Gravity did slow the expansion after the Big Bang. But then expansion gained the upper hand. The Universe behaves like a driver slowing down to stop but then hitting the gas pedal when the light turns green.

Why did the light turn green? We call the green-light phenomenon "dark energy"---a term coined by the University of Chicago astrophysicist Michael Turner. Einstein first came up with the idea of a dark energy that shoves galaxies away from each other at ever increasing speeds. He later discarded the idea, calling it his greatest blunder but it was an insight. Dark energy may come from the quantum vacuum---a netherworld whose particles blink into and out of existence. Whatever it is and where ever it comes from---it makes up 65 % of the Universe.

"While we don't know what dark energy is, we are certain that understanding it will provide crucial clues in the quest to unify the forces and particles in the universe, and that the route to this understanding involves telescopes, not accelerators," says Turner. Next week: South Pole telescopes get data that verifies the Big Bang theory.

Further Surfing:

WonderQuest: Expanding space

WonderQuest: The Big Bang

WonderQuest: Outside the space pinhead

space.com: Dark energy finding

(Answered Jan. 31, 2003)

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