Indeed - that’s it. I remember reading a comment from someone who attended the lecture (an academic) to the effect that the assembled audience of some of the countries best and brightest were embarrassed for him.
Newton's laws refer to the motion of particles. To correctly explain Laithwaite's gyroscope demonstrations requires a summation over all the particles which make up the whole body of the gyroscope. This shows that Newton's Second Law of motion holds, provided it is applied to the centre of mass of the gyroscope.
Newton 2 for a particle states: Force = rate of change of momentum
Newton 2 for a gyroscope states: Total moment of the external forces = Rate of change of total moment of momentum
Poor old Eric Laithwaite! However, he did go on to develop the linear induction motor and gain the title 'Father of Maglev'. YouTube
Newton 2 for a particle states: Force = rate of change of momentum
Newton 2 for a gyroscope states: Total moment of the external forces = Rate of change of total moment of momentum
Poor old Eric Laithwaite! However, he did go on to develop the linear induction motor and gain the title 'Father of Maglev'. YouTube
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I remember struggling with all that stuff in class back in the day.
Looking at it afresh by courtesy of the internet, I can almost understand it now! 🙂
Looking at it afresh by courtesy of the internet, I can almost understand it now! 🙂
Slippery when there's ice on the roads, so quite a bit of that stuff quickly "sets in your bones". Inertia, momentum, direction, weight etc.
"Can we make it?"
"Nah, better brace in a few seconds."
"Can we make it?"
"Nah, better brace in a few seconds."
High intensity laser experiments have recently verified that a new phase of water, which was theoretically predicted to exist over 30 years ago, does actually exist.
Unlike the ice on your roads, this 'superionic ice' is black and hot. A cube of it would weigh four times as much as a cube of normal ice. Scientists think it might be among the most abundant forms of water in the universe.
It is now thought that superionic ice (aka superionic water) fills the interiors of giant gas planets like Uranus and Neptune.
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I was doing a bit of rooting around last night, and found out the Earth is just on the right side of the inner boundary of the habitable zone. Some scientists have posited that if we were just 5 million miles closer to the sun, the planet would have looked totally different wrt life forms. 10 million miles closer to the Sun and in all likely hood runaway greenhouse effect would have taken place and we'd look something like Venus.
The Suns output is increasing at a about 1% every 100 million years (quite normal for a main sequence star of the sun's mass).
To say things are finely balanced for us would be an understatement.
Something else to ponder as we sit Coronavirus out.
The Suns output is increasing at a about 1% every 100 million years (quite normal for a main sequence star of the sun's mass).
To say things are finely balanced for us would be an understatement.
Something else to ponder as we sit Coronavirus out.
Ah! The Goldilocks zone! Also called the habitable zone or the life zone.
Early in the Earth's history, the Sun's output was only about 70% of what it is now. The 'faint early Sun' paradox asks why the Earth's oceans did not freeze in these early days, thus preventing the establishment of life.
One possible answer to this question is that CO2 was present at high concentration in those early times.
Faint young Sun paradox - Wikipedia
Early in the Earth's history, the Sun's output was only about 70% of what it is now. The 'faint early Sun' paradox asks why the Earth's oceans did not freeze in these early days, thus preventing the establishment of life.
One possible answer to this question is that CO2 was present at high concentration in those early times.
Faint young Sun paradox - Wikipedia
A tempting but verging on the 'insane' solution for an increasingly hotter sun is to move the the planet further away from its host star. Assuming the existence of an engine that could produce such a thrust, there is still the problem caused by Jupiter and Mars staying in the way.
I cannot remember where, but somewhere, I read that two PhD students wrote a thesis about moving the Earth away from the sun using asteroid catapults over a period of 100 million years. They postulated that it is enough to use one asteroid per 10000 years. But this is a slow process and the Earth's orbit is changed very slowly with the danger of a planery collision between either Mars or Jupiter.
Using Newton's Law of Gravitation, the force of attraction between our planet and its host star is: 3.56x10^22N. This is huge, and no imaginable machine can produce such a thrust. If my estimate is correct, a steel cable with a cross section of 100 square kilometers will break with such a tensile force!
I cannot remember where, but somewhere, I read that two PhD students wrote a thesis about moving the Earth away from the sun using asteroid catapults over a period of 100 million years. They postulated that it is enough to use one asteroid per 10000 years. But this is a slow process and the Earth's orbit is changed very slowly with the danger of a planery collision between either Mars or Jupiter.
Using Newton's Law of Gravitation, the force of attraction between our planet and its host star is: 3.56x10^22N. This is huge, and no imaginable machine can produce such a thrust. If my estimate is correct, a steel cable with a cross section of 100 square kilometers will break with such a tensile force!
No chance of that happening edbarx!
The kind of solution I envisage in the far future is for some sort of self assembling shield to be built. You would fire these little robots into orbit and they would self organize into a shield. You’ll need 50-100 billion of them mind you. Manufactured on the moon by robots and launched from there due to lower gravity.
Galu, yes I’ve read about the faint sun paradox as well. Quite incredible.
The kind of solution I envisage in the far future is for some sort of self assembling shield to be built. You would fire these little robots into orbit and they would self organize into a shield. You’ll need 50-100 billion of them mind you. Manufactured on the moon by robots and launched from there due to lower gravity.
Galu, yes I’ve read about the faint sun paradox as well. Quite incredible.
If you read James Lovelock, one of the things he talks about is the fact that although the Sun is only about halfway through its life (‘middle aged’), the earth is actually in its very old age. He cites the Suns increasing output as a factor a s points the Earth can only support life for another 200-300 million years before greenhouse runaway takes effect - nothing like the 1-2 billion years quoted in some quarters.
Mars, here we come.
Mars, here we come.
I don’t think the best way to shift the Earths orbit away from the Sun is to simply try to ‘thrust’ it away. The momentum of something weighting 6.6x20^23 metric tons is just too great.
A better way is to have a sufficiently massive body like the moon and to alter its orbit and use that to shift the Earths orbit outwards. It’s a 100 million yr project and would have to be ‘bootstrapped’ up. So you start with a small body like an asteroid, use that to leverage a bigger asteroid, repeat for 10 or 20 steps and then the moon and finally the Earth.
When I was a kid, my Dad had a book out of the local library about terraforming and geo-engineering on a massive scale. There was one plan in the book to wind a few coils of wire around Jupiter and spin it up until it started to disintegrate so humans could tap into the energy resources from the gases etc. Another one was to sew the upper atmosphere of Venus with bacteria to alter the atmosphere (Carl Sagan IIRC) to make it fit for human habitation ( bit of a long shot given what we know now about the place!!)
Fun stuff!
A better way is to have a sufficiently massive body like the moon and to alter its orbit and use that to shift the Earths orbit outwards. It’s a 100 million yr project and would have to be ‘bootstrapped’ up. So you start with a small body like an asteroid, use that to leverage a bigger asteroid, repeat for 10 or 20 steps and then the moon and finally the Earth.
When I was a kid, my Dad had a book out of the local library about terraforming and geo-engineering on a massive scale. There was one plan in the book to wind a few coils of wire around Jupiter and spin it up until it started to disintegrate so humans could tap into the energy resources from the gases etc. Another one was to sew the upper atmosphere of Venus with bacteria to alter the atmosphere (Carl Sagan IIRC) to make it fit for human habitation ( bit of a long shot given what we know now about the place!!)
Fun stuff!
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Terraforming, or Earth-shaping, is ripe picking for sci-fi writers.
As far back as 1898, in H.G. Wells' The War of the Worlds, the invading Martians aimed to reverse-terraform Earth for their own uses.
So is our Solar system's make up a virtual collection of materials on a mega scale organized randomly or dictated like in a centrifuge where separation occurs by density? Is it ordered? Or could the planets have taken any random position?
There appears to be no accepted law which governs the orbital positions of the planets. Bode's law suggests that each planet should be approximately twice as far from the Sun as the one before. However, Bode's law correctly predicts the orbit of Uranus while failing to predict the orbit of Neptune.
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