9/11, the sheer scale of the collapse...

[JamesW]

"I have heard (it might be an urban myth though) that cats can survive the fall from very tall buildings, because by spreading themselves out and increasing drag they reach their terminal velocity rather quickly."


http://en.wikipedia.org/wiki/Cat_righting_reflex

[Sam Slater]

Don't worry, Max, I didn't take it as a threat. Don't think you're that type of guy.

Cheers.

[JamesW]

Sorry I didn't make my link clickable:

http://en.wikipedia.org/wiki/Cat_righting_reflex

As mentioned here, cats do indeed spread themselves out during a fall to achieve a parachute effect.

[max_tranmere]

I'm not being flippant here, but could a falling human fall in a certain way to slow down the fall?

[beutelwolf]

max_tranmere wrote:

> I'm not being flippant here, but could a falling human fall in
> a certain way to slow down the fall?

A Radio Yerevan answer: in principle yes, but it would not help much.
According to that Wikipedia article falling cats reach a terminal velocity of 100km/h which they apparently can survive due to their build. I don't think humans would survive that speed anyway, but their terminal velocity (same article) is 210km/h.

With a lot of exercise (we do not have that reflex) a human could surely reduce that speed a little, but to not much avail.

P.S.
As an intermediate step between falling cats and falling humans we could try throwing cats of human size (i.e. lions) out of the 9th floor of a high-rise. Don't think they would stand a chance. Perhaps a mountain leopard would, but I doubt it.

P.P.S.
Just wondering: have Radio Yerevan jokes ever made it to the UK?

[JamesW]

"With a lot of exercise (we do not have that reflex) a human could surely reduce that speed a little, but to not much avail."

Yes, agreed.

However, a human can do something to INCREASE the speed of a fall. Skydivers sometimes deliberately make a fall faster by tucking in their arms, legs and head as much as possible. This increases their terminal velocity from 210km/h to about 330km/h.

Competition speed skydivers opt to fall head down as that position gives even greater speed.

[Gusset Sniffer]

NASA 6.5-ton Upper Atmosphere Research Satellite, or UARS, was carried into orbit during a space shuttle mission in 1991.

UARS has been slowly losing altitude, tugged by Earth's gravity. On Friday, the 35-foot-long, 15-foot diameter satellite is expected to plunge into the atmosphere.

While most of the spacecraft will be incinerated, scientists expect up to 26 pieces, with a combined mass of about 1,100 pounds (500kg) to survive the fiery re-entry and fall down somewhere on Earth.

NASA said the chance a piece of UARS debris will strike a person is about one in 3,200. The debris will mostly likely fall into an ocean or land in an uninhabited region of Earth.


I'm no rocket scientist but 3200 to 1 of being hit? !shrug! I don't think so. The odds must be millions to one !confused! Anyone a bookie?

If a coin will smash a paving slab thrown from the twin towers what will a satellite do from 100 miles high !whistle!

[JamesW]

"If a coin will smash a paving slab thrown from the twin towers what will a satellite do from 100 miles high."

The satellite itself will never reach the Earth. Only 26 pieces of debris are expected to survive, as you in fact already mentioned.

Here's the list:

(1) HGA gimbal and reten. (Titanium) 59 pounds impacting at 99 miles per hour

(4) Forward bulkhead fitting (Titanium) 55 pounds impacting at 177 miles per hour

(1) SSPP gimball (Titanium) 134 pounds impacting at 130 miles per hour

(1) SSPP structure (AL-2024-T8) 348 pounds impacting at 99 miles per hour

(4) MMS fuel tanks (Titanium) 11 pounds impacting at 59 miles per hour

(3) MMS MPS batteries (SSteel 304L) 101 pounds impacting at 146 miles per hour

(4) Reaction wheel rims (SSteel 304L) 4 pounds impacting at 240 miles per hour

(1) FSS housing (Beryllium) 7 pounds impacting at 175 miles per hour

(2) FHST bracket (Beryllium) 2 pounds impacting at 40 miles per hour

(2) G.F. abutment plate (Titanium) 4 pounds impacting at 30 miles per hour

(2) G.F. base plate (Titanium) 11 pounds impacting at 81 miles per hour

(1) G.F. extension (Titanium) 1 pound impacting at 47 miles per hour

[rgb]

That 348 pound bit coming down at 99mph might give you a bad headache...!stars!

[beutelwolf]

Gusset Sniffer wrote:

> NASA said the chance a piece of UARS debris will strike a
> person is about one in 3,200. The debris will mostly likely
> fall into an ocean or land in an uninhabited region of Earth.
>
>
> I'm no rocket scientist but 3200 to 1 of being hit? !shrug! I
> don't think so. The odds must be millions to one !confused!
> Anyone a bookie?

It's a rather odd number for a wild guess, so I gather the boffins at NASA did the numbers properly, taking into consideration that the thing breaks up and that the pieces landing on land might bounce around a bit before hitting someone.

In real life we humans tend to be quite bad at estimating low probabilities, in the sense that there is a threshold below which an event is judged as "this is not going to happen". This was fine for judging risks to our lives when we were roaming the African savanna, but a lot less fine for managing stock market risks, as we all have found out now.

3200 to 1 is the kind of odds bookies would give to Saudi Arabia winning the Soccer World Cup. Not a team likely to make it even onto a dark horses list prior to the competition.

Note that if 3200 skylabs were falling the down that way, each with this probability of hitting someone, then the overall probability of one person being hit by any of them would jump not to 1 but roughly to 1-(1/e) which is about 63%.