Totally Random Science Facts

[AV1611VET]

The fastest animal in existence is the lightning bug.

 

[MorkandMindy]

The fastest animal in existence is the lightning bug.

OK then, the shortest man mentioned in the Bible was Job's friend Bildad the Shoe height

 

[lesliedellow]

The mass of the earth is 5970 million million million tonnes.

A bit too heavy to pick up.

 

[MorkandMindy]

If the Earth didn't have a magnetic field the solar wind would have scraped the atmosphere away by now

 

[kharisym]

Acquired Sociopathy has been linked with brain damage (lesions) in the prefrontal cortex.

Damage to the prefrontal cortex has been well established to also cause moral impairment and personality changes.

http://www-bcf.usc.edu/~raine/commentary neural basis for sociopathy.pdf

 

[AV1611VET]

The Titanic was considered 'unsinkable'.

 

[rockaction]

The Titanic was considered 'unsinkable'.

The Bible says you can cure leprosy with seances and animal blood. Doctors suggest rifampicin and dapsone instead.

 

[Blayz]

The emu and kangaroo are on the Australian coat of arms because neither can walk backwards

Elephants cannot jump

No idea about millipedes.

 

[Naraoia]

My thought experiment is to stick half an acre (or so) of fleas together side by side and get them all to jump at once. The total mass of fleas is 100kg, then when they all jump at once they are producing the same energy as on 100kg human doing the same thing.

The scaling has to be done in parallel, not series.

That most humans can jump higher than this shows the jumping mechanism is better, or we are less affected by air resistance (any opinions on which?)

cheers M of M&M

Higher than what? It's probably true that we are less affected by the air, but your whole scenario is a hypothetical without an actual measurement of how high half an acre of fleas can jump...

it is downright pointless to scale that to a 7 foot human jumping over the Eiffel Tower or a Blue whale leaping out of the sea and hitting a jetliner.

What is happening is chemical energy in the flea is being converted into potential gravitational energy.

Really? I thought it was a fairly mechanical spring mechanism The only remotely "chemical" reference I can find in here is the mention of the elastic protein resilin (which apparently forms part of the "spring").

The same ratio of conversion of chemical energy into potential energy would allow a human athelete to jump, 13 inches.

And where do you get that?

 

[KhlulHloo]

Cephalopods are awesome

That's not an opinion, it's a fact

YouTube - Octopus Predicts World Cup Winners

YouTube - octopus open a jar

YouTube - Shapeshifting Octopus, amazing camouflage

 

[rockaction]

I just watched the 2005 Call of Cthuhlu film last night. Amazing!

 

[lesliedellow]

The nearest star to the sun is Proxima Centauri, 4.2 light years away. Somebody traveling close to the speed of light would be gone for 8.5 years, earth time, so we won't be paying our nearest neighbours a visit anytime soon - assuming that there is a life supporting planet orbiting Proxima Centauri; which seems doubtful.

 

[kharisym]

The nearest star to the sun is Proxima Centauri, 4.2 light years away. Somebody traveling close to the speed of light would be gone for 8.5 years, earth time, so we won't be paying our nearest neighbours a visit anytime soon - assuming that there is a life supporting planet orbiting Proxima Centauri; which seems doubtful.

That's slightly less than the speed of light, about 49.4% of it to be exact.

 

[Wiccan_Child]

The nearest star to the sun is Proxima Centauri, 4.2 light years away. Somebody traveling close to the speed of light would be gone for 8.5 years, earth time, so we won't be paying our nearest neighbours a visit anytime soon - assuming that there is a life supporting planet orbiting Proxima Centauri; which seems doubtful.

The next nearest system is Alpha Centauri, a binary star system. Weirdly, it's only 0.21 lightyears away from Proxima Centauri - I wonder what they would look like to each other?

 

[Wiccan_Child]

That's slightly less than the speed of light, about 49.4% of it to be exact.

I think he means on a roundtrip, so, with rounding errors, it could be more or less exactly c.

 

[lesliedellow]

That's slightly less than the speed of light, about 49.4% of it to be exact.

You're not forgetting that it's 8.4 light years, there and back, are you?

 

[Naraoia]

Cephalopods are awesome

That's not an opinion, it's a fact

I concur

The nearest star to the sun is Proxima Centauri, 4.2 light years away. Somebody traveling close to the speed of light would be gone for 8.5 years, earth time, so we won't be paying our nearest neighbours a visit anytime soon - assuming that there is a life supporting planet orbiting Proxima Centauri; which seems doubtful.

The next nearest system is Alpha Centauri, a binary star system. Weirdly, it's only 0.21 lightyears away from Proxima Centauri - I wonder what they would look like to each other?

Wait, isn't Proxima Centauri part of the Alpha Centauri system?

 

[MorkandMindy]

My thought experiment is to stick half an acre (or so) of fleas together side by side and get them all to jump at once. The total mass of fleas is 100kg, then when they all jump at once they are producing the same energy as on 100kg human doing the same thing.

The scaling has to be done in parallel, not series.

That most humans can jump higher than this shows the jumping mechanism is better, or we are less affected by air resistance (any opinions on which?)

cheers M of M&M

Higher than what? It's probably true that we are less affected by the air, but your whole scenario is a hypothetical without an actual measurement of how high half an acre of fleas can jump...

It was a thought experiment, I took one flea and multiplied it up into enough fleas side by side or in whatever arrangement to have the same weight as a human and then with equal body masses compared the jumping abilities. With them now like for like, if the human could jump higher than the fleas it must be due to humans being better at jumping or the higher air resistance affecting the flea.

I'd like to comment that the means of attaching the fleas together doesn't come into it because if the fleas didn't all jump at once it wouldn't work however they were joined up, and if they did all jump at once then they wouldn't need to be joined up.

Take the thought experiment a bit further and the fleas don't even have to be together, could be all over the World, and well really the other fleas don't even have to exist, the ratio of converting chemical energy into potential energy is the same if both animals (flea and human) reach the same height.

it is downright pointless to scale that to a 7 foot human jumping over the Eiffel Tower or a Blue whale leaping out of the sea and hitting a jetliner.

What is happening is chemical energy in the flea is being converted into potential gravitational energy.

Really? I thought it was a fairly mechanical spring mechanism

The only remotely "chemical" reference I can find in here is the mention of the elastic protein resilin (which apparently forms part of the "spring").

The mechanical spring allows the energy to be stored up and then released suddenly, which with the short legs the flea has is essential, but this is a mechanism that allows it to convert so much chemical energy into potential energy. The human manages the same feat by having longer legs and is therefore able to have more time for the conversion of chemical energy into potential energy and thereby converts about the same ratio.

The same ratio of conversion of chemical energy into potential energy would allow a human athlete to jump, 13 inches.

And where do you get that?

Well suppose the flea weighs a millionth as much as a human. When it jumps 13 inches it moves it's centre of gravity up by the same amount as the human that jumps 13 inches, and the flea then has a millionth as much potential energy as the human gains by jumping 13 inches.

The flea only had to put in a millionth as much work to get that high because it only weighs a millionth as much, so it only had to convert a millionth as much food into work which is handy because it only has about a millionth as much.


So comparing fleas to humans jumping 900 feet or so is pretty silly, it is a far better comparison to compare fleas jumping 13 inches with humans jumping 13 inches, but it doesn't give that 'gee whiz' effect that is so essential to bad science.

.

 

[kharisym]

I think he means on a roundtrip, so, with rounding errors, it could be more or less exactly c.

You're not forgetting that it's 8.4 light years, there and back, are you?

Woops, assumed a one-way trip. It does raise an interesting question though:

Wiccan child, you're the token physicist, if I were to use an ion drive accelerating xenon atoms to close to the speed of light, could I ever actually exceed 0.5 c?

I seem to recall that in a vacuum, we can only extract about half the kinetic energy we put into the exhaust as thrust.

 

[Wiccan_Child]

Wait, isn't Proxima Centauri part of the Alpha Centauri system?

Alpha Centauri has two stars: Alpha Centauri A and Alpha Centauri B. Proxima Centauri is near Alpha Centauri, but it's not part of it. It's a mere 0.21 light years, so it's bloody close.

Woops, assumed a one-way trip. It does raise an interesting question though:

Wiccan child, you're the token physicist,

All I need now is a cape and some spandex pants

If I were to use an ion drive accelerating xenon atoms to close to the speed of light, could I ever actually exceed 0.5 c?

I seem to recall that in a vacuum, we can only extract about half the kinetic energy we put into the exhaust as thrust.

According to the Tsiolkovski (sp?) equation, depending on your initial and final mass during a burn period, you can accelerate to any arbitrary speed. You can, if you burn enough fuel, accelerate to (say) five times the exhaust speed. I'm dredging this from the depths of my brain, so don't sue me if I'm out by an order of magnitude or two