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Comment by marcosscriven | Hacker News Reader

With time-dilation, from the point of view of those on board, it's actually possible to travel as far as Andromeda with constant 1g acceleration (decelerating at 1g half way), within a few decades. Of course, time back on earth would have gone by a few million years...

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Huh, but if light takes 2.5 million years to get to Andromeda, how does it take us a few decades? You're saying that from the point of view of the photon, it takes much less time?

Yes photons do not experience time, it's all the same instant for them

So a photon can get anywhere it wants instantly to them?

From the reference fram of the photon, yes

This is a great article (for laypeople, it's not supposed to be too technical) that explains it and makes it easy to understand: http://zidbits.com/2011/04/why-cant-anything-go-faster-than-...

I'll quote the relevant bit, "Imagine for a moment that you are a happy little photon created by a star in another galaxy some 4 billion light years away. From my perspective here on Earth, it took you exactly 4 billion years to travel from that star till you reached my retina. From your perspective, one instant you were created and then the next, you are are bouncing off or being absorbed by my eyeball. You experienced no passage of time. Your birth and death happened instantaneously.

This is because time slows for you as your get closer to light speed, and at it, it completely stops. This is also another reason why nothing can go faster than light. It would be like slowing down a car to a stop, and then trying to go slower than completely stopped."

It's super interesting that the speed of light is exactly 282,xyz (can't remember) miles per second. What're the chances? I'm just unable to comprehend the idea that a fundamental universal constant could be an exact whole number amount of an arbitrary measurement unit like that. You'd think there'd be a few decimal points or something.

You're misremembering. The speed of light in miles per second is ~186,282.396. The speed of light in meters per second is 299,792,458, but the meter is defined using the speed of light:

https://en.wikipedia.org/wiki/Speed_of_light

Not only this, but due to space compression to the photon the star and your eye are also exactly the same place!

Yes, that's how relativity works.

Plus, as in Egan's Diaspora, virtual entities can hibernate, or live at far lower clock frequency.

I've not read Diaspora (yet!), but this sounds more like Permutation City

I haven't read Permutation City yet, but virtualization in Diaspora is far more advanced. The default, as I recall, is ~800 times meatspace. I recommend reading Stephenson's Anathem first, however.

Edit: The Planck Dive is a follow-on.[0]

[0] http://gregegan.customer.netspace.net.au/PLANCK/Complete/Pla...

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