If half the Earth dissappeared what would our orbit be like?

I wholly agree the KE is a function of mass as well as velocity, exempting quantum effects and speeds approaching that of light let's say linear, but you did not say that KE would be reduced as a proportion of the mass, nor would that be a logical assumption, given your impossible disappearing mass scenario.

Given that mass cannot just disappear with no effect (as you suggested) and given you did not originally say anything about the KE's relation to this disappearing mass, it was fully reasonable (if reasonable can be applied to your impossible scenario!) for me to assume the KE was ambiguous.

Thanks ever so much for the cool link, and if you wish to chime in on a new thread here about countersteering and gyroscopic procession you would be most welcome! http://www.able2know.com/forums/viewtopic.php?t=89715&highlight=

Gonna be some pretty dramatic topological changes on the surface of the earth, too....

You sure those theoretical physicists are gonna be around to ponder the problem?

He's suspended conservation of energy... belike he's suspended conservation of momentum as well.... So I guess we're not gonna start spinning like an ice skater.



I suppose, you could posit another system of bodies, a star with identical mass to our sun, a planet in the same position as earth, with the same orbital speed, but with half of Earth's mass, and ask what would happen....

Too bad might be fun!
Should I assume this new model has a steady state condition, or if not what variables have been changed compared to our home earth model, and what suspensions of disbelief should I be prepared to make?

Thinking a bit more deeply about this I realised if you lost half your mass, you'd loose more. It's the Earth's mass that keeps our atomsphere, more specifically atomic hydrogen. Loss that much mass and you'd loose atomic hydrogen, loose that and you eventually loose water, as water vapour from the oceans would be ionised by ultraviolet light and the hydrogen would escape into space.

Also if the loose was not simply every second atom, but split the Earth in two - then you'd get very different effect if you lost the bright side of the Earth vs the Dark Side facing away from the sun, due to the centrifugal force of our motion on the oceans.

PS

Heisenberg's uncertainty principle shows any law of physics can be broken for a finite time in a finite location with a set probability. Combine this with quantum mechanics allowing a particle to be in more than one place at a time, or be created or pop out of existance within our frame of reality and you have a nifty framework for this unlikely occurence to happen!

Me thinks it's not so much "Earth's mass that keeps our atmosphere" as it is a balance between the Earth's mass due to gravitational forces, versus centrifugal forces and natural losses to space etc.

"Every second atom"

Not to mention some pretty interesting chemical reactions....

"Split the Earth in half"
You'd expose a circle (or oval, depending on where you chose to place the knife) to vacuum. Nasty for those near the face. Nastier, perhaps, for those that endure, for however brief a period, the Earth slumping back into a (near) sphere.

This is a gross oversimplification of Heisenberg's uncertainty principle, stretched to the point of wrongness. Any law of physics?

It does sound poetic though.

If an Electron Can Be in Two Places at Once, Why Can't You?

http://www.discover.com/issues/jun-05/cover/?page=3

Yes I'll try and find the link for you. Most school students only know of Heinsenberg's initial work on measuring the position or momentum of an atom with a limited level of precision. By second year Uni you start studying Schrodinger's wave equation and see it can't work on some standing waves, unless the wave penetrates into the wall, relfects and comes back. The way you pull off this trick is the first more subtle use of Heinsenberg's insights. Quantum Mechanics as then developed by Heinsenberg, Schrodinger and Dirac takes this alot further. http://en.wikipedia.org/wiki/Introduction_to_quantum_mechanics

The old saying was

Schrodinger rules the waves, but Heinsenberg waives the rules!

Surprised you hadn't heard of this one. From memory Hawking's the Universe in a Nutshell spent some time on Heinsenberg's insight on uncertainity bending rules.

A slight overview can be gained here http://www.dallasces.org/talks/greeson.apr.2006.pdf

excert:

Heisenberg (1926):Measuring the location of a particle requires a minimumof one quantum, but this quantum will disturb the particle and change its velocity in a way that cannot be predicted.The more accurately you try to measure the position of the particle, the less accurately you can measure its speed, and vice versa. Led Heisenberg, Shrodinger, and Dirac in the 1920s to reformulate mechanics into a new theory called quantum mechanics, based on the uncertainly principle. At best, a particle has a quantum state, which is a combination of position and velocity that can never be predicted, but would fall within a range of different possible outcomes, each with a probability attached to it. Quantum mechanics therefore introduces an unavoidable element of unpredictability and randomness into science.

This randomness or probability function for determining events allows rules to be voided due to both the uncertainity inherent in waves and partilces (and how they affect spacetime) for very small durations in very small locations with a finite probability.

So my "bad science" one of our leading, but least fully understood sciences, QM. Put simply uncertainty is built into everything and non deterministic is guaranteed. Hawking used this to model what would happen to information falling into a black hole. In fact QM has wierder, but viable postulates according to Hawking, like not only is the future of the uncertain, but elements of the past are too! So we might have more than one past.

Time is a strange beast.