You'd have to get very close to the speed of light, before you'd see any really significant relativistic effects.

That just isn't practically doable with any technology within humanity's reach, probably for centuries. If it ever will be at all.

The amount of energy needed to propel anything at that speed is enormous.

Unless my math is very wrong, at 0.9c the passenger perceived time is more or less half the perceived time from the departure point. That's already quite significant, although not something I could do over a vacation ;-)

In order to spend a leisurely "cruise-ship" week to Proxima you'd need to go very close to c. At that speed, even friction with a non-ideal vacuum is a problem :-D.

> a trip to the next star can be a week-long affair from your point of view

You’d need to travel at around 233x the speed of light to make getting to the nearest star be a week trip, no?

The effect is called time dilation. The section of interest here is „Time dilation caused by a relative velocity“:

https://en.m.wikipedia.org/wiki/Time_dilation

I’m aware of time dilation, my point was that a “week vacation” to something “over 4 light years” away is just hyperbolic.

Nope! If you obtain the full speed of light then a) you're not made of baryons anymore so congratulations on that and b) no time passes whatsoever between your being emitted in some tight laser beam on planet A, and being transcribed on planet B, from your perspective.

None. Photons don't experience time, they are time.

Not exactly. For you to think you are traveling 20x faster than light, your friends that stayed at home would have to see you traveling at 0.99995c. For 233x faster than light, that's a lot of 9's in that number.

I get 0.999c for 20x and 0.99999c for 220+

I'll trust your numbers more than mine.

But, for all intents and purposes, this is impossibly fast ;-)

Unless you are on the Bistromath, that is.

There is no faster than light, I can't parse this statement.

Distance divided by [time experienced by traveler]. GP is not saying that traveler went faster than light.

From the passenger's point of view, yes. For everyone else you'd be veeeery close to c, but not quite there.

My point was it’s hyperbolic. You’d have to be going so close[0] to C that it’d be impossible.

[0] about 0.99999c if what someone else in this thread said is correct