Sure, there are plenty of practical problems that would make the trip impossible. The fuel mass alone that would have to be shot out the back to make that trip would be something on the order of 800 million times the mass of the payload (you). So a 100kg person sitting in a 100kg spaceship would require something like 160 billion kg of fuel, assuming zero energy loss in burning the fuel. Relativistic rocket calculators are fun!
Fun fact: if you got 250 MPG in a space car loaded up with as much gasoline as there is water in the ocean, you could could drive to the edge of the observable universe.
Momentum but no mass, if I recall my physics correctly (low certainty).
Wait, hang on, we have access to an appreciable-chunk of the world's knowledge at our fingertips...
https://en.wikipedia.org/wiki/Photon - "Photons are massless[...]In empty space, the photon moves at c (the speed of light) and its energy and momentum are related by E = pc, where p is the magnitude of the momentum vector p[...]Current commonly accepted physical theories imply or assume the photon to be strictly massless"
Typically momentum is thought as mass times velocity, and since photons do have momentum, there was a desire to give them some kind of "relativistic mass".
In more recent times, it has been seen as easier to use just one concept of mass, and to redefine momentum entirely. So, photons have a mass of 0, and we don't need to specify "rest mass". But they do have momentum.
no, the earth is actually big. 47 trillion times heavier than that mass. At 90% c that 160 billion kg would still be a small fraction of the planets (moving 10,000x slower, at 30 km/s) kinetic energy. 500,000x less.
Of course that .06 m/s velocity change would be near instant, so bad things would happen. Probably a humanity-ending but not life-ending disaster. Global tsunamis and incredibly large tectonic changes, for sure. Imagine the entire water column of the marianas trench jumping up in the air and slamming into the ground below.
If the energy was transferred at a single point, it'll be the worst extinction event ever (4000x worse than chicxulub) but I'd bet single-celled and maybe even some multicellular life would survive. Anything bigger than a mouse is fucked, though.
Yes because ions are... ions. You don't see photons knocking the planet out of orbit, do you? They can exert force but they don't exert that much force.
But if you're trying to avoid self-propulsion and want to launch from Earth, say, even a 200kg craft, anywhere "close to the speed of light", then that will most probably require a significant enough amount of force to knock the planet out of orbit.
If you can apply small force over a long time, that will get you up to speed, too.
Someone did the math in the thread, and suggested that a constant 1g of acceleration would get you to the centre of the galaxy in 20 years (as measured by the clocks traveling on your spaceships). 1g of acceleration for 200kg is about 1962 Newton.
(This back of the envelope calculation assumes you have eg someone fire a laser at your ship to give you the energy you need. If you need to bring your own fuel, the rocket equation increases the total mass needed. But the same principle still applies: something like an ion drive has very little force, even if the top speed it can reach can be enormous.)
I think everyone is collectively ignoring that I'm specifically talking about accelerating the craft from earth, not using an ion drive or similar form of propulsion on-board. As that's what is implied by the comment that I responded to: "If you could shoot it out at close to speed of light"
Just need to build a parabolic reflector on one side of it and point it towards the opposite direction where we want to go. When the reflector shoots to far from the same, tilt the reflectors, drop down closer to the Sun by gravity, tilt them back, do it again.
Yes. And that's not the only way to make this work.
Btw, the sun is also an extremely inefficient engine. With a bit of extra engineering we could probably scoop up hydrogen from the sun, and 'burn' it much more efficiently.
Fun thought, we’re kind of all on one right now! Regardless of how you choose to define “human,” we’ve been around for much less time than a single revolution around the Milky Way. We get no say in the route, and our star is feeding us rather than fueling our travel, but still a wild thought.
