From the perspective of someone on the ground, yes. But due to time dilation, it could be just a few days for the people on the ship.
Heck, you have to get better than 5 nines to even compress a year into a day, .9999963c, which would take a freakish amount of energy to accelerate a KG to (3.3 × 10^19 J).
What medical ethics board is going to approve a research project "put healthy experimental subject in coma for 5 years, observe what they are like when they wake up?"
Reminds me of https://en.wikipedia.org/wiki/Deep_sleep_therapy and https://en.wikipedia.org/wiki/Chelmsford_Royal_Commission
I think this is an example of a technology which, if it is ever developed, is most likely to be developed by some kind of totalitarian regime which has no ethical qualms about human experimentation.
Inducing torpor would have major medical uses in surgical and emergency medicine, it's not just useful for passing the time.
We do know how to inefficiently create and store antimatter, we don’t have any idea how to cause human hibernation.
To me getting two dozen of orders of magnitude better at something is clearly hard, but that still beats trying to do something we don’t have a clue how to start. For human hibernation step 1 is probably serious genetic engineering and there’s going to be other steps.
World ending doesn't begin to describe what that looks like.
Do the same thing over a year in many different devices and you’re basically dealing with a normal nuclear power plant’s output.
Hell, we can't even store hydrogen without leakage issues and with anti-hydrogen any leakage is very bad.
They've put pigs into suspended animation for an hour or two, I'm not sure what the upper bound is on that or how much further it's possible to go with it. Ditto organ deep-cooling. So while it's not feasible now, it feels like we need "only" 100x or so improvement to make it viable.
In the interstellar medium, matter is primarily in molecular form and reaches number densities of 10^12 molecules (mostly composed of) hydrogen, then helium, oxygen, nitrogen) per cubic meter (1 trillion molecules per cubic meter).[1]
So, what, about a picogram per cubic meter.
If your ship has a cross-sectional area of one square meter, and Alpha Centauri is 40,000,000,000,000 meters away [2] (and you thought it was a long way to the shop if you want a Chiko Roll), you’ll have to manage with 2.62^23 tonnes of mostly hydrogen in the way.
The interstellar medium is also about 1% dust, so about 2.6^21 tonnes of solid matter.
Someone check my mass maths.
1. https://en.m.wikipedia.org/wiki/Interstellar_medium
2. Google Search AI Overview
Dust is a concern but again the typical dust particle size would be about the power of a gun shot of a small caliber rifle. A problem to deal with but a rarer event still. Of course another challenge would be larger dust particles which while improbable are still possible which largely rules out humans in these craft. But that goes without saying since the acceleration to get to that speed would be unlikely something humans could withstand anyway.
Even interstellar/stellar wind would have enough molecules of gas to cause some crazy erosion/damage.
Impact seems to have a timelined meaning, starting with destruction, then following up with conquering, and exploration coming somewhere before constructive applications at the far end.
As apes we just can't keep holding back till we can build houses or something with it, when we also could just throw that stone at something. Especially before someone else does :)