What will be the biggest non-man made threat to humanity in the 21st century?

Question

What will be the biggest non-man made threat to humanity in the 21st century?
I think apathy and rampant consumerism are pretty major. What do you think?

Answer 1

Apophis belongs to a group called the "Aten asteroids", asteroids with an orbital semi-major axis less than one astronomical unit. This particular one has an orbital period about the Sun of 323 days, and its path brings it across Earth's orbit twice on each passage around the Sun.

Apophis is the Greek name of the Ancient Egyptian god Apep, "the Destroyer", who dwells in the eternal darkness of the Duat (underworld) and tries to destroy the Sun during its nightly passage.

From your question it is clear that you are concerned about the possibility of an impact and how devastating that might be.

WIKIPEDIA ASSESSES THESE AS FOLLOWS

Possible impact effects

It must be stressed that the odds of impact are now known to be very low. Hence, the possible effects of an impact are largely irrelevant.

However, the initial reports resulted in widespread discussion on many Internet forums, including armchair speculation about exactly where Apophis (then known only as 2004 MN4) would hit and what would happen when it did.

NASA initially estimated the energy that Apophis would have released if it impacted Earth as the equivalent of 1480 megatons of TNT. A more refined later NASA estimate was 880 megatons. The impacts which created the Barringer Crater or caused the Tunguska event are estimated to be in the 10-20 megaton range. The 1883 eruption of Krakatoa was the equivalent of roughly 200 megatons.

The exact effects of any impact would have varied based on the asteroid's composition, and the location and angle of impact. Any impact would have been extremely detrimental to an area of thousands of square kilometres, but would have been unlikely to have long-lasting global effects, such as the initiation of an impact winter.

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MY COMMENTS AGAIN:

The bigger threat is in 2880 and is from asteroid 1950 DA. It is 4 times the diameter and thus ~64 times the volume of Apophis. Potentially more damaging consequences, therefore. If there were to be an impact.

Radar observations at the Goldstone and Arecibo Observatory from March 3 to 7, 2001 during the asteroid's 7.8 million km approach to the Earth give a mean diameter of 1.1 – 1.4 km. Optical lightcurves by Petr Pravec show that the asteroid rotates every 2.1216 hours.

Due to its short rotation period, 1950 DA is thought to be fairly dense (more than 3.0 g/cm³).

If 1950 DA continues on its present orbit, it will approach near to the Earth on March 16, 2880. Over the intervening time, the rotation of the asteroid will cause its orbit to change. One trajectory misses the Earth by tens of millions of kilometers, while the other has an impact probability of 1⁄300. The radar observations are currently being reanalyzed, in combination with the optical lightcurves.

The energy released by a collision with an object the size of 1950 DA would cause major effects on the climate and biosphere which would be devastating to human civilization.

The discovery of the potential impact has heightened interest in asteroid deflection strategies (see my third link).

http://en.wikipedia.org/wiki/99942_apoph...
http://en.wikipedia.org/wiki/1950_da...
http://en.wikipedia.org/wiki/asteroid_de...

Worst case scenario assuming the asteroid is solid iron and hits us dead on:

Crater: 6.32 km in diameter
Blast Energy: 1940 megatons

At a range of 50 km, almost all buildings are knocked down and your clothes are set on fire. Magnitude 6.8 earthquake, which will be minimum compared to the shockwave in the air.

At 100 km, the fireball is 5 times brighter than the sun but does not set your clothes on fire. The blast will be as loud as heavy traffic, and will shatter glass windows. 6.8 on the richter scale, which scares everyone but does not damage buildings that are up to building code.

So it destroys an area larger than Rhode Island, but smaller than Conneticuit. The Earth is not significantly perturbed by this blast, although the country that gets hit will be.

Impacts like this happen once every 38000 years on average.

These numbers are based on a pessimistic interpretation of NASA's most recent figures from their website. Actual impact may be less destructive.

You can go to the two websites below and run as many doomsday scenarios as you feel like, but there is little point in worrying about things we can't prevent or predict. NASA is working very hard on ways to destroy or move asteroids right now, and they will probably have a way to do it soon.

Answer 2

Asteroids.
Apathy and rampant consumerism are man-made.

Answer 3

Man himself

Answer 4

The greatest man made threat to humanity in the 21st century will be what it has been for a long time. Liberals.

Answer 5

If we don't get AIDS in control, it will be that. If you are looking for something that would happen with or without human intervention, I think the switching of the earth's polarity would be interesting.

Answer 6

ummm, isnt apathy and consumerism man made?

man, how stupid are some of these people who asks dumbf-u-ck questions?

the greatest non-man made threat to humanity? stupid AS$ nimrods like you who has no idea what they are asking!

Answer 7

The Yellowstone caldera could erupt.

Answer 8

Natural disasters.

Answer 9

Probably a big meteor.

Answer 10

time