Scientific 'things you've always wanted to know' thread
Discussion
A slightly lighthearted idea, pinched from the lounge.
I'm very much a generalist layman, and I suppose like most in my position, I know just about enough to confuse the hell out of me!
So, couple of questions for anyone to chip in answers to, and it'd be great if this thread grows with mini 'trivial' questions in the same vein.
1) Bit of biology.
I have several boy gerbils living in a massive aquarium. They're bloody great, AMD fascinating to watch. Last night one pulled the pretty bloody heavy food bowl off the shelf its on, onto its head. It fell about 2 feet (the gerbil fell too), and cracked the poor bugger on the back.
The way it hit made me think he was a gonner, it would have left a mark had it been my hand and not his back...
Yet today he's fine. Considering he's a mammal, with presumably essentially the same cells/circulatory system etc. how come he isn't half bruise?
2) Physics
In school I learnt about potential energy, including gravitational potential. Essentially, my understanding is that the gravitational potential increases with distance from the Earth's centre. This explains I believe the accelerative nature of gravity as a force.
So surely if that's the case, as the effect of gravity decreases with increasing distance from the Earth's core, the rate at which gravitational potential energy increases with distance is constantly reducing, until it stops increasing when the object is removed from the Earth's gravitational influence completely.
Yet if that is so, and by definition an object out of the Earth's gravitational influence must have zero gravitational potential energy, where does this energy go without being in violation of the Law of Conservation of Energy.
Quite certain both the above show a clear ignorance of something relatively basic - but that's the point. Having recognised my ignorance, I'd like to rectify it.
Cheers,
Sam
I'm very much a generalist layman, and I suppose like most in my position, I know just about enough to confuse the hell out of me!
So, couple of questions for anyone to chip in answers to, and it'd be great if this thread grows with mini 'trivial' questions in the same vein.
1) Bit of biology.
I have several boy gerbils living in a massive aquarium. They're bloody great, AMD fascinating to watch. Last night one pulled the pretty bloody heavy food bowl off the shelf its on, onto its head. It fell about 2 feet (the gerbil fell too), and cracked the poor bugger on the back.
The way it hit made me think he was a gonner, it would have left a mark had it been my hand and not his back...
Yet today he's fine. Considering he's a mammal, with presumably essentially the same cells/circulatory system etc. how come he isn't half bruise?
2) Physics
In school I learnt about potential energy, including gravitational potential. Essentially, my understanding is that the gravitational potential increases with distance from the Earth's centre. This explains I believe the accelerative nature of gravity as a force.
So surely if that's the case, as the effect of gravity decreases with increasing distance from the Earth's core, the rate at which gravitational potential energy increases with distance is constantly reducing, until it stops increasing when the object is removed from the Earth's gravitational influence completely.
Yet if that is so, and by definition an object out of the Earth's gravitational influence must have zero gravitational potential energy, where does this energy go without being in violation of the Law of Conservation of Energy.
Quite certain both the above show a clear ignorance of something relatively basic - but that's the point. Having recognised my ignorance, I'd like to rectify it.
Cheers,
Sam
I can do the physics one. To be totally out of the earth's gravity is impossible. It decreases as the inverse square of the distance, but it never reaches zero. Just because all the universe isn't crashing into the earth doesn't mean that it's gravitational effect isn't acting on an object, just that other effects (inertia and other gravitational effects) swamp it. Relative to the earth, it still has potential. Under conventional physics, you could put the object at the other end of the universe and, if you waited long enough, they would eventually collide.
Probably. I say that because, so far as I know, they can't quite work out whether the universe is expanding more slowly, more quickly, or what. Chances are that if you say one thing, there will be a report in 6 months time that says completely the other thing.
I blame Higgs' Bosom.
Probably. I say that because, so far as I know, they can't quite work out whether the universe is expanding more slowly, more quickly, or what. Chances are that if you say one thing, there will be a report in 6 months time that says completely the other thing.
I blame Higgs' Bosom.
I wonder was the gerbil contemplating the effects of gravity after his excitement with the bowl. After all, humans first understood gravity when Newton noticed an apple fall. Maybe gerbils will understand gravity from having bowls fall on their bonces.
Ny the way, the RSPCA might have a word to say about making gerbils stretch above their heads to get their food.
Ny the way, the RSPCA might have a word to say about making gerbils stretch above their heads to get their food.
Sway said:
the rate at which gravitational potential energy increases with distance is constantly reducing, until it stops increasing when the object is removed from the Earth's gravitational influence completely.
Don't think it ever stops completely, just becomes very very small. (very)I believe the first question is vaguely related to the first. I heard a quote once along the lines of:
Drop a mouse 100ft and it bounces
Drop a man 100ft and he breaks
Drop a horse 100ft and it splashes.
The gerbil vs dish cannot be scaled up linearly I believe that it will be to the power of two type relationship, same as when a child falls over, someone half your size falls with 1/16 of the force. Your furry bugger probably did not really feel it.
Drop a mouse 100ft and it bounces
Drop a man 100ft and he breaks
Drop a horse 100ft and it splashes.
The gerbil vs dish cannot be scaled up linearly I believe that it will be to the power of two type relationship, same as when a child falls over, someone half your size falls with 1/16 of the force. Your furry bugger probably did not really feel it.
To clarify re: gerbils great escapade:
The gerbil fell, hit the deck (8" of sawdust etc. they dig in), after pulling the food bowl into a 'Italian Job' scenario where a second later it fell and t
tted the gerbil pretty bloody hard. The bowl weighs around half a kilo (supposedly to stop them dragging it around) and fell 20", so the force of the impact was high enough I'm sure to have raised a bruise on my bony hand (the closest approximation to the size and structure of the gerbil on my body) - why not the gerbil?
It experienced the same force my hand would have, is composed of essentially the same substance, yet seems completely unaffected. The bruise on my hand would have been covered his whole tiny back. It's almost like a parallel to how strong ants would be if scaled up to human scale - would gerbils be double hard tank like furry pigs?
Cheers for the answer to the physics one - so an object in Andromeda for example would nominally have a staggering value for the gravitational potential energy relative to the Earth, however this is mitigated by all the other vectored gravitational pulls (and therefore energy) being exerted by everything else, with proximity especially playing a bit part in this mitigation?
Eric - if you watched these things for 5 minutes you'd realise there's not a chance little JK is the Newton of his species. He has no greater joy in his life than a used toilet roll core, and yet he's a cheery little chap.
As an aside, I'd recommend a small group of gerbils as quite simply the best pets going for kids and adults alike. Kept in an aquarium they're like a scaled up ant farm with social structures being played out better than Eastenders.
The gerbil fell, hit the deck (8" of sawdust etc. they dig in), after pulling the food bowl into a 'Italian Job' scenario where a second later it fell and t
tted the gerbil pretty bloody hard. The bowl weighs around half a kilo (supposedly to stop them dragging it around) and fell 20", so the force of the impact was high enough I'm sure to have raised a bruise on my bony hand (the closest approximation to the size and structure of the gerbil on my body) - why not the gerbil?It experienced the same force my hand would have, is composed of essentially the same substance, yet seems completely unaffected. The bruise on my hand would have been covered his whole tiny back. It's almost like a parallel to how strong ants would be if scaled up to human scale - would gerbils be double hard tank like furry pigs?
Cheers for the answer to the physics one - so an object in Andromeda for example would nominally have a staggering value for the gravitational potential energy relative to the Earth, however this is mitigated by all the other vectored gravitational pulls (and therefore energy) being exerted by everything else, with proximity especially playing a bit part in this mitigation?
Eric - if you watched these things for 5 minutes you'd realise there's not a chance little JK is the Newton of his species. He has no greater joy in his life than a used toilet roll core, and yet he's a cheery little chap.
As an aside, I'd recommend a small group of gerbils as quite simply the best pets going for kids and adults alike. Kept in an aquarium they're like a scaled up ant farm with social structures being played out better than Eastenders.
Sway said:
an object in Andromeda for example would nominally have a staggering value for the gravitational potential energy relative to the Earth,
Yes.Sway said:
however this is mitigated by all the other vectored gravitational pulls (and therefore energy) being exerted by everything else, with proximity especially playing a bit part in this mitigation?
What do you mean by "mitigated". The potential energy exists, but the object won't be pulled back towards earth until the end of the Universe.mrmr96 said:
What do you mean by "mitigated". The potential energy exists, but the object won't be pulled back towards earth until the end of the Universe.
I mean mitigated in the sense of why I believed the gravitational influence eventually reduced to 0 rather than just a very small amount. And why I also made the mistake of believing that the objects in the universe with the greatest level of gravitational potential were those which are most visibly influenced by the Earth's gravity.Probably a bad word to use in this context but I think I now have the workings clear enough in my mind to be happy, but perhaps not well enough yet to describe effectively!
Sway said:
mrmr96 said:
What do you mean by "mitigated". The potential energy exists, but the object won't be pulled back towards earth until the end of the Universe.
I mean mitigated in the sense of why I believed the gravitational influence eventually reduced to 0 rather than just a very small amount. And why I also made the mistake of believing that the objects in the universe with the greatest level of gravitational potential were those which are most visibly influenced by the Earth's gravity.Probably a bad word to use in this context but I think I now have the workings clear enough in my mind to be happy, but perhaps not well enough yet to describe effectively!
0000 said:
Red sky at night / in the morning.
What actually causes it?
Rayleigh scattering from particles (atoms/molecules) in the atmosphere. The 'cross section' for scattering (essentially how effective the scattering is) varies inversely with wavelength (or wavelength to the power of 4 from memory), so essentially of all the colours in the visible spectrum the shorter wavelengths are scattered more readily.What actually causes it?
The light is effectively de-blued (blue is shorter wavelength) as it passes through the atmosphere and the red light therefore becomes more visible.
A long path length through the atmosphere is required for sufficient de-bluing, hence only being seen near sunrise or sunset, as the path length through the atmosphere is greater when the sun nears the horizon.
carmonk said:
Zad said:
To be totally out of the earth's gravity is impossible.
[pedantic mode on]Actually most things are completely outside of the earth's gravity. Only that stuff that's in a 4.5bn light year radius of earth is affected by Earth's gravity[/pedantic mode off]Er, what?
Sway said:
carmonk said:
Zad said:
To be totally out of the earth's gravity is impossible.
[pedantic mode on]Actually most things are completely outside of the earth's gravity. Only that stuff that's in a 4.5bn light year radius of earth is affected by Earth's gravity[/pedantic mode off]Er, what?
Sway said:
Eric - if you watched these things for 5 minutes you'd realise there's not a chance little JK is the Newton of his species. He has no greater joy in his life than a used toilet roll core, and yet he's a cheery little chap.
I have it on good authority that Sir Isaac could have hours of fun with a tube of cardboard - especially if it had a couple of lenses in it.carmonk said:
Sway said:
carmonk said:
Zad said:
To be totally out of the earth's gravity is impossible.
[pedantic mode on]Actually most things are completely outside of the earth's gravity. Only that stuff that's in a 4.5bn light year radius of earth is affected by Earth's gravity[/pedantic mode off]Er, what?
ii) Even if it did, lets not forget that the earth wasn't created out of nothing 4.5Bn years ago - and the matter which the earth came to be made of would have had its own gravtiational field since it came into being. So why would the gravity of the earth only have an effect from the point the earth was created, rather than from the point that whatever made the earth was created?
mrmr96 said:
carmonk said:
Sway said:
carmonk said:
Zad said:
To be totally out of the earth's gravity is impossible.
[pedantic mode on]Actually most things are completely outside of the earth's gravity. Only that stuff that's in a 4.5bn light year radius of earth is affected by Earth's gravity[/pedantic mode off]Er, what?
mrmr96 said:
ii) Even if it did, lets not forget that the earth wasn't created out of nothing 4.5Bn years ago - and the matter which the earth came to be made of would have had its own gravtiational field since it came into being. So why would the gravity of the earth only have an effect from the point the earth was created, rather than from the point that whatever made the earth was created?
Before the earth was created there was no earth, so you can't say the earth's gravity was present prior to that, clearly. Before the earth there was just gas and debris vast areas.mrmr96 said:
carmonk said:
Before the earth was created there was no earth, so you can't say the earth's gravity was present prior to that, clearly. Before the earth there was just gas and debris vast areas.
Gas and debris has gravity, fool!! 
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