<story><title>Rotating Black Holes May Serve as Gentle Portals for Hyperspace Travel</title><url>https://theconversation.com/rotating-black-holes-may-serve-as-gentle-portals-for-hyperspace-travel-107062</url></story><parent_chain><item><author>imglorp</author><text>I&amp;#x27;m in a more conservative camp than speed limits: the practicality one.&lt;p&gt;Even if we ignore the ponies and rainbows of wormhole travel, if you want to travel to a plain black hole to use the magic teleporter, the nearest two are V616 Mon at 11 solar masses and 3000 LY away, and Cyg X1 at 15 SM and 6000 LY.  If you buy into the article&amp;#x27;s assertion that you won&amp;#x27;t get burned or spaghettified on your way to becoming a nucleon paste, and you want a heavier BH, the nearest is Sag A* at 4.1e6 SM and 25000 LY away.&lt;p&gt;Anyway, to travel between the teleporter and Earth, we&amp;#x27;re talking most of the resources of a planet to accelerate a mass to substantial fractions of c. Then you&amp;#x27;ve got thousands of years of collisions, radiation, and maybe (assumption?) cultural and biological challenges of living in space for aeons, plus needing another planet&amp;#x27;s worth of resources to slow down at the destination. All this makes it hard enough even to get a dozen LY to our nearest start system.&lt;p&gt;My opinion is we&amp;#x27;re in something of a Well World universe, where everyone is pretty well travel-isolated from their neighbors.</text></item><item><author>cletus</author><text>Put me firmly in the camp that believes the speed of light is a hard limit on the universe and I&amp;#x27;ll use Isaac Arthur dismissal of FTL travel as to why.&lt;p&gt;He contends that there likely isn&amp;#x27;t a sentient civilization within about a billion light years of us because the signature of Dyson spheres would be unmistabkable and unmissable. Now this isn&amp;#x27;t to say there isn&amp;#x27;t one that&amp;#x27;s say, 600 million light years away that built their first Dyson sphere 500 million years ago although, in practice, this doesn&amp;#x27;t really change the probabilities that much.&lt;p&gt;If there&amp;#x27;s FTL then that billion light year practical limit really goes out the window as you can effectively get anywhere in the universe, making the volume of absence be many, many times the size of the observable universe.&lt;p&gt;I&amp;#x27;m not sure why the author is talking about gravity ripping you apart in a black hole. It Is Known [tm] that larger black holes have pretty gentle event horizons.&lt;p&gt;I&amp;#x27;m not sure why it matters that a black hole would be spinning. You can pretty much assume every significant mass in the universe is spinning to some degree (a state of zero spin being highly unlikely over even small amounts of time).&lt;p&gt;The author talks about the inner event horizon and I guess that&amp;#x27;s the point. But all of that is highly theoretical. Nothing is known about the inner workings of a black hole. It&amp;#x27;s all highly theoretical and beyond the ability of general relativity to describe. No other theory has been able to adequately explain or describe gravity let alone extreme gravity so your view on what&amp;#x27;s within the event horizon probably depends on which unproven theory (eg string theory) you subscribe to.&lt;p&gt;So this is speculation based on speculation.</text></item></parent_chain><comment><author>tachyonbeam</author><text>I hear you, but I think colonizing the galaxy might still be feasible. If we can get to the point where we have the technology to colonize Mars, which will hopefully happen this century, then I would imagine it probably won&amp;#x27;t be long after that until we manage to have permanent space habitats that harvest materials from asteroids.&lt;p&gt;If we have fusion power, durable permanent space habitats, and the technology to harvest materials from asteroids, then traveling to the next star system doesn&amp;#x27;t seem so far-fetched anymore. If we could just reach 0.1c, we could make it to Alpha Centauri in less than 50 years. Once we make it there, if we&amp;#x27;re already comfortable living in space, we don&amp;#x27;t even need to worry about terraforming or anything lengthy and complicated like that, we can just harvest asteroids and build more space stations and ships.&lt;p&gt;Not a physicist, but I see Project Orion could have reached 0.33% of the speed of light. Would it be realistic to extend that design to accelerate to 0.1c?</text></comment>
<story><title>Rotating Black Holes May Serve as Gentle Portals for Hyperspace Travel</title><url>https://theconversation.com/rotating-black-holes-may-serve-as-gentle-portals-for-hyperspace-travel-107062</url></story><parent_chain><item><author>imglorp</author><text>I&amp;#x27;m in a more conservative camp than speed limits: the practicality one.&lt;p&gt;Even if we ignore the ponies and rainbows of wormhole travel, if you want to travel to a plain black hole to use the magic teleporter, the nearest two are V616 Mon at 11 solar masses and 3000 LY away, and Cyg X1 at 15 SM and 6000 LY.  If you buy into the article&amp;#x27;s assertion that you won&amp;#x27;t get burned or spaghettified on your way to becoming a nucleon paste, and you want a heavier BH, the nearest is Sag A* at 4.1e6 SM and 25000 LY away.&lt;p&gt;Anyway, to travel between the teleporter and Earth, we&amp;#x27;re talking most of the resources of a planet to accelerate a mass to substantial fractions of c. Then you&amp;#x27;ve got thousands of years of collisions, radiation, and maybe (assumption?) cultural and biological challenges of living in space for aeons, plus needing another planet&amp;#x27;s worth of resources to slow down at the destination. All this makes it hard enough even to get a dozen LY to our nearest start system.&lt;p&gt;My opinion is we&amp;#x27;re in something of a Well World universe, where everyone is pretty well travel-isolated from their neighbors.</text></item><item><author>cletus</author><text>Put me firmly in the camp that believes the speed of light is a hard limit on the universe and I&amp;#x27;ll use Isaac Arthur dismissal of FTL travel as to why.&lt;p&gt;He contends that there likely isn&amp;#x27;t a sentient civilization within about a billion light years of us because the signature of Dyson spheres would be unmistabkable and unmissable. Now this isn&amp;#x27;t to say there isn&amp;#x27;t one that&amp;#x27;s say, 600 million light years away that built their first Dyson sphere 500 million years ago although, in practice, this doesn&amp;#x27;t really change the probabilities that much.&lt;p&gt;If there&amp;#x27;s FTL then that billion light year practical limit really goes out the window as you can effectively get anywhere in the universe, making the volume of absence be many, many times the size of the observable universe.&lt;p&gt;I&amp;#x27;m not sure why the author is talking about gravity ripping you apart in a black hole. It Is Known [tm] that larger black holes have pretty gentle event horizons.&lt;p&gt;I&amp;#x27;m not sure why it matters that a black hole would be spinning. You can pretty much assume every significant mass in the universe is spinning to some degree (a state of zero spin being highly unlikely over even small amounts of time).&lt;p&gt;The author talks about the inner event horizon and I guess that&amp;#x27;s the point. But all of that is highly theoretical. Nothing is known about the inner workings of a black hole. It&amp;#x27;s all highly theoretical and beyond the ability of general relativity to describe. No other theory has been able to adequately explain or describe gravity let alone extreme gravity so your view on what&amp;#x27;s within the event horizon probably depends on which unproven theory (eg string theory) you subscribe to.&lt;p&gt;So this is speculation based on speculation.</text></item></parent_chain><comment><author>wallace_f</author><text>Very interesting, but this assumes life evolves to Type II civ.&lt;p&gt;I mean, looking at our own planet, it seems this might be extremely unlikely.&lt;p&gt;To the best of my knowledge, another Planet Earth could possibly be within a few hundred ly of us(0.000000001 of known universe), and we&amp;#x27;d have no idea(1)..?&lt;p&gt;1-&lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;www.centauri-dreams.org&amp;#x2F;2012&amp;#x2F;05&amp;#x2F;31&amp;#x2F;is-our-civilization-detectable&amp;#x2F;&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;www.centauri-dreams.org&amp;#x2F;2012&amp;#x2F;05&amp;#x2F;31&amp;#x2F;is-our-civilizati...&lt;/a&gt;</text></comment>