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[wierd]

Push off earth's magnetic field?

Not enough to overcome surface gravity, and if you pumped enough feild strength out to actually do so, you would have every iron/steel/nickel/permanent magnet for miles around trying to reverse their orientation (physically), and then trying to pull on your field/stick to your ship.

[LordBaal]

I advice you to send that question to What If of Randall Munroe. It would be interesting.

[MaximumZero]

Or ask Monkeyhead, who is our resident mad physicist, iirc.

[MonkeyHead]

You called?

Short answer - not much, without using several metric shit tons of electricity which you would be better off using to run some more efficient mechanism. Like lasers. Or motors. Or an ion engine.

Longer answer - the mean magnetic field strength of the Earth at its surface is about 4.5*10^-5 Tesla - several orders of magnitude weaker than a fridge magnet. This means to generate even a modest thrust you need a few hundred thousand million coulombs of charge moving around (via good old F = Bqv or F = BIL). That sort of current will do bad things, like ionize the air around you, melt your vehicle and so on. Sounds a good idea for a weapon though, or defensive system - literally melting ferrous projectiles via inducing huge currents, or some such. Interestingly, while doing some reading for this answer, I discovered that it takes 16 Tesla to levitate a frog.... We could use the strongest magnets we have ever made (33ish Tesla, superconducting cryo electromagnets used in the LHC) to lift 2 frogs.

[PTTG??]

Since you're here, what do you think about the Em-drive concept?

[MonkeyHead]

Since you're here, what do you think about the Em-drive concept?

I am sceptical of the proposed mechanism of force production claimed in EMDrive proposals. I am also sceptical of the claimed results - such forces as claimed are so small as to be well within the bounds of errors or other propulsive effects of EM radiation. Though this is a form of scepticism that I hope is wrong, as I often do with "revolutionary" physics.

[WillowLuman]

You called?

Short answer - not much, without using several metric shit tons of electricity which you would be better off using to run some more efficient mechanism. Like lasers. Or motors. Or an ion engine.

Longer answer - the mean magnetic field strength of the Earth at its surface is about 4.5*10^-5 Tesla - several orders of magnitude weaker than a fridge magnet. This means to generate even a modest thrust you need a few hundred thousand million coulombs of charge moving around (via good old F = Bqv or F = BIL). That sort of current will do bad things, like ionize the air around you, melt your vehicle and so on. Sounds a good idea for a weapon though, or defensive system - literally melting ferrous projectiles via inducing huge currents, or some such. Interestingly, while doing some reading for this answer, I discovered that it takes 16 Tesla to levitate a frog.... We could use the strongest magnets we have ever made (33ish Tesla, superconducting cryo electromagnets used in the LHC) to lift 2 frogs.

https://www.youtube.com/watch?v=DjpeCGaV4qw

They also did other things, like a spider and random bits of plastic, but I can't find footage/pictures.

[BFEL]

I discovered that it takes 16 Tesla to levitate a frog....

Every single one of those is hilarious in their own special way.

[Il Palazzo]

I discovered that it takes 16 Tesla to levitate a frog... We could use the strongest magnets we have ever made (33ish Tesla, superconducting cryo electromagnets used in the LHC) to lift 2 frogs.

What, you need twice as dense a flux to lift twice the mass against constant force? Shouldn't 33T propel as many frogs as you like at ~1g upwards?

[MrWiggles]

Since you're here, what do you think about the Em-drive concept?

I am sceptical of the proposed mechanism of force production claimed in EMDrive proposals. I am also sceptical of the claimed results - such forces as claimed are so small as to be well within the bounds of errors or other propulsive effects of EM radiation. Though this is a form of scepticism that I hope is wrong, as I often do with "revolutionary" physics.

It seems to be passing muster though. Though at the same time, it also seems to be violating the conversation of energy.

[10ebbor10]

Thought it only violated conservation of momentum, not energy.

[wierd]

Momentum is a measure of kinetic energy, and can also be expressed as a mass term.

The second law of motion is that for every action, there is an equal and opposite reaction. The device SHOULD be pushing particles with the same energy that those particles push back against the device with, which should then be colliding with the back of the device, negating the forward push they initially imparted. However, the particles stop existing before they reach the back end of the device, so they never interact again, and thus never confer that countering momentum, resulting in a violation. The energy simply vanishes along with the particles carrying it-- for all intents and purposes.

This may just be an APPARENT violation, however. The measured laser interferometry data suggests that the fabric of spacetime itself is reacting to this energy disequilibrium, and may in fact be where the energy is "Going."  "Empty space" is not a null value for energy state, and fluctuates wildly. The added energy on those virtual particles may be, for instance, kicking the local energy state of the local space to the device into a slightly more energetic condition, which then dissipates over distance as increased vacuum fluctuations, which being completely random, are unable to meaningfully negate the initially imparted momentum, allowing the "reactionless" drive to work, while still conserving the energy conservation law. (Just bending it into some gnarly shapes.)

Spacetime with a slightly different energy density would have slightly different vacuum properties, which would affect how other kinds of forces propogate through it, which may explain the interferometer data. (Some interpretations of feild propogation use models of virtual particle interaction to carry the field. "Anomalies" in the virtual particle density of one bit of spacetime right next to another would create anomalies in field propogation between those regions, which is what the laser interferometer is detecting.)

Being able to exert pressure on the prevalence/rate of vacuum fluctuations would be a radical new development.

[Il Palazzo]

Momentum is a measure of kinetic energy

Mind telling us more about it? Because it looks like some new physics to me.

[wierd]

No, that's ancient newtonian stuff.

The kinetic energy of an object is related to its momentum by the equation:

Ek = (P^2/2M)

where:

Ek is kinetic energy
 P is momentum
 M is mass of the body

The relationship is why accelerating protons in a particle collider gives them effective mass, by increasing thier energy, and is also partially responsible for why a mass bearing object cannot accelerate to light speed. (requires more and more energy to accellerate, because it gains effective mass as the momentum changes from the addition of that energy, due to relativity between energy and mass.)


Combined with the famous E=MC^2, we can convert the mass term into an energy term (and vice-versa),  and thus define momentum as a relationship between moving and resting energy, (and thus as an energy term), relative to velocity. (or as a relationship between two masses, real and effective, and a velocity)

Momentum is just a relational property of the interaction between mass and kinetic energy, expressed via the change in velocity.

[MonkeyHead]

I discovered that it takes 16 Tesla to levitate a frog... We could use the strongest magnets we have ever made (33ish Tesla, superconducting cryo electromagnets used in the LHC) to lift 2 frogs.

What, you need twice as dense a flux to lift twice the mass against constant force? Shouldn't 33T propel as many frogs as you like at ~1g upwards?

Ohyeah. Derp. Forget that Tesla is a field strength, not a force. Now I want a cryomagnet powered frog blaster. Thanks.