Elon Musk Has Bought Twitter...

Dales Cannon

Hump? What hump?
Staff member
Musk's response was that it isn't possible and using a law of physics to make it look like he knows something. Which he doesn't since he doesn't have any formal qualifications. Real ones. He did not say it is currently not possible with current technology which is what I suspect you are saying though I am not sure why I am bothering to respond. I know the physics without the need to look it up on google. It is a question of motive force, where that comes from is not relevant. So while it may not be currently feasible or practicable it is still possible. That is not what musk said and his trolls are trying to make him sound omiscient when he is the opposite.


Eats Squid
Musk's response was that it isn't possible and using a law of physics to make it look like he knows something. Which he doesn't since he doesn't have any formal qualifications.
he literally has a physics degree lol. a real one. Thats not even a question.

and an economics degree (though not relevant to this point)

and the law he used is 100% the relevant factor - His third law states that for every action (force) in nature there is an equal and opposite reaction. If object A exerts a force on object B, object B also exerts an equal and opposite force on object A.

heres NASAs take on it

the law doesn't state that it must always result in a movement, just that forces have an equal and opposite reaction. In the case of an electrically driven force, that force simply isn't strong enough in any currently known or developed technology to achieve moving a rocket. The force occurs, the opposite reaction occurs and nothing happens. Technically possible? sure. SO is building a space elevator, or stopping the earths rotation. The maths says it can be done. But this is the realm of dyson sphere science fiction right now, so for all intents and purposes, no, electric rockets cant be done, literally dues to newtons third law.

i love how the internet is full of people who are just like "aha, gotcha" like they're the ones putting rockets into space because some dude who is literally on the forefront of cutting edge tech, barely sleeps didn't take a more concerted effort to respond in a more technical way that accounted for all the hypotheticals on twitter (in 140 characters) to some dumbass that could have saved himself the question by thinking about it or just googling it.
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Eats Squid
I question it. Seems shady as fuck.

I missed the bit where they said electric rocket are impossible and will never happen ever because of Newton’s third law
sorry but your opinion on whether his physics degree is shady or not doesn't even matter. He has one, you don't. he send rockets into space, you don't. Like why is this even a point of contention at this point?

as to missing the bit, you must have. because the inverse is also true. if you cant generate enough force, you cant move the object. Right? The point of highlighting NASAS take is to show that newtons third law is directly applied to rocket propulsion in the traditional sense. You need to do SOME of the mental work to understand that the same concept applies to other things and other forces and how the interplay might work.

Really really big rail gun?
have we got one?
wikipedia (because this conversation really isnt worth any more than that for obvious reasons) "While explosive-powered military guns cannot readily achieve a muzzle velocity of more than ≈2 km/s (Mach 5.9), railguns can readily exceed 3 km/s (Mach 8.8). For a similar projectile, the range of railguns may exceed that of conventional guns."

So not even accounting for velocity fall off, less than half of what is required (7km/s) to get to orbit at the muzzle (only) and also on a much smaller projectile than a rocket. SO again, for all intents and purposes, no, a railgun wouldn't do, not even a really, really big one. The economics of the scenario are entirely relevant to these matters. Pretty sure there wouldn't even be enough magnets on earth to build a rail gun big enough to hurl a rocket fast enough accounting for velocity fall off from such a device.