True but we can't go bottom of the ocean because it will crush us and in space, it doesn't right so there is a difference but yes we don't know for a different galaxy it might crush us but we need to go at least 8,000,000,000 kilometers pr hour right.
You are talking two different planes of universe . . . probably. Probably two very different universe environments. You shouldn't, and we probably one day won't, measure interstellar, intergalactic, and even inter-universe, speeds by the same measures and instruments of measurement we use for Earth surface ground speeds. We will not deal in any absolutes of
space out there just as we do not deal in absolutes of time.
You may not realize you were dealing in a strict absolute of
space's portion of
space-time with your 8,000,000,000 kilometers per hour, when in fact the two,
space and
time, are actually as equivalent as mass and energy are equivalents (as mass-energy isn't anything more nor less than two sides of one inseparable (indivisible) coin). Elastically contract the time, elastically contract the space. Elastically expand the time, elastically expand the space. If you don't believe me, think about the look itself of the universe. That [
non-elastic space -
elastic time] mistake will continue to be made until we've been out there for decades to centuries moving among planets and stars, and galaxies and even universes (which means any effective loss and gain of relativities (which in turn means we, as 4-d travelers in 4-d conveyances, will be moving among -- in an environment of -- countless more or less discrete 4-d space-times (not a single one observable before arrival in and to it))) in continuously powered conveyances . . . we hopefully will acquire as we go out.
What I'm trying to say is you should try to stop thinking 2-dimensionally. You should try to stop thinking flat universe "flatland" when it comes to 4-dimensional space-times (4-dimensional universes). Or rather you should think in more dimensionalities than one or two. You manage it, you manage true elasticity as far as space-time and relativity are concerned. You manage space-times within space-times: universes within universes (think the physical reality we already know, and deal in, of QM within QM (of micro-verses within, alongside, intermingled and intermingling with, micro-verses . . . discrete . . . discrete . . . big time(!) (as some say, including me, the stuff of
Alice in Wonderland / Through the Looking Glass existing in reality). A real territory and map down and in that effectively maps a real territory up and out . . . a "Great Unknown" frontier, eventually to be realized).
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It's a Multiverse Universe.