If you invented a time machine would it need to be a space ship. I ask this because if you moved in time the earth would be in a different place than it was when you started.
I would say no, on a technicality. A “spaceship” is a vessel that can survive the rigors of outer space. While a time machine would necessarily also have to be able to move physically, for the reason you describe, it wouldn’t have to actually function in space: as it travels through time, it moves with the earth, keeping it in an atmosphere at all times.
A boring answer is that if you propose magic, it can have any properties that you choose.
A more interesting answer is that any space ship is, in a sense, a time machine. The only way to really do something that’s akin to time travel is to accelerate yourself away from earth, then come back. More time will have passed for those who remained on earth, so in a sense you will return in the future.
Quick answer:
If you built it right, it doesn’t have to be.
If you build it wrong, it had better be!
Why don’t we call them Time-ships and Space-machines?
Hey! My car is a time machine. When I leave the house and come back I have returned in the future.
Most self contained time machines are unable to escape the gravity well of a planetary mass, so no, you do not need to make it capable of withstanding interplanetary space.
Doc Brown? Is that you?
You’re assuming that, first of all, the Earth is moving, and second, that the time machine is not. Neither assumption is meaningful. The simplest assumption would be that the time machine would retain the same trajectory through spacetime as it had initially, which would mean that it would stay with the Earth (though if it’s not subject to electromagnetism, it might go on a high-eccentricity orbit through the Earth-- Make sure to get out when it’s above the surface).
Alternately, even if the time machine allows travel to arbitrary spacetime coordinates, that still doesn’t necessarily imply that it’d be a spaceship. It might not even be anything describable as a “vehicle” at all. Maybe, for instance, it opens up a portal to the destination, which you can then step through. You might, then, jump straight from the surface of one planet to another, without ever being far from a planet.
If one could pass through time, as the idea of a time machine implies, it is very unlikely that the means of doing so would depend on a hard physical conveyance. If time travel took place in a physical capsule of some kind, that capsule itself would be for some other purpose than propelling the time traveler. In fact, the difficulty of time travel would be greatly magnified if the traveler had to drag a machine along.
Time travel would take place only in the perception of the observer, and his body might not even go along. It would be easier to move that perception through space than through time.
We are all time machines, traveling forward through time at roughly the same speed. And somehow, we manage to remain on earth, more or less.
Why do I hear this in Carl Sagan’s voice?
YES
Because…
Just remember that you’re standing on a planet that’s evolving
And revolving at 900 miles an hour.
It’s orbiting at 19 miles a second, so it’s reckoned,
The sun that is the source of all our power.
Now the sun, and you and me, and all the stars that we can see,
Are moving at a million miles a day,
In the outer spiral arm, at 40,000 miles an hour,
Of a galaxy we call the Milky Way.
Go back into the past just one hour and you’ll be 70,000 miles from where you were.
nitpick: Nuclear fission is a source of power we have that was not sourced in/from the sun, but in some nova/supernova. Also Geothermal, which is mostly nuclear decay and would have a similar origin.
But we go through time at the same velocity as everything else, including the erth, so we have no perception of the movement. Like moving through space in a train, where we feel motionless. The concept of a time machine is meaningless without a sense of passing through time at a different rate than the surroundings that we remaining in contact with.
I suppose you could design the “stargate” style of time machine where you can only travel between two portals connecting a wormhole. You would need to send one of the portals out in a spaceship at relativistic velocities so they become out of sync in time.
The downside is you can only travel between the two physical locations of the portals at whatever point in time they are in. i.e. you can only go back in time x number of days.
That why they say it goes through time and relative dimension in space.
Once you get them out of sync, wonder if you could sent another set of gates through the original set multiple times to get them further out of sync.
Exactly. There is no such thing as absolute vector motion, so, whilst we can say with confidence that the Earth is rotating, and that it is moving in an orbit relative to the sun, and the system is moving around the galaxy relative to galactic centre, and so on, there’s no meaningful definition of ‘staying absolutely still’.
One might hypothesise that time travel into the future (that is, faster than one second per second) might entail experiencing interaction with physical phenomena at an increased rate - for example travelling 10 days into the future in a subjective journey time of 1 day might, I dunno, subject the traveller to 10 times the normal force of gravity for the duration.
(although I guess that would have to mean that travel into the past would actually invert some phenomena).
So you’re theorizing that all I have to do to lose the weight my doctor wants is to move at 90% the speed of time? So I get healthier AND age more slowly?