[HN Gopher] "I survived the TCP transition" (2013)
___________________________________________________________________
"I survived the TCP transition" (2013)
Author : agomez314
Score : 130 points
Date : 2022-08-22 14:54 UTC (8 hours ago)
(HTM) web link (blog.google)
(TXT) w3m dump (blog.google)
| kerblang wrote:
| [Cue 32-bit IP snark] blah
| dboreham wrote:
| The transition to IPv6 basically spanned my entire career (in
| networking, I had a previous career as a hardware engineer). My
| first task was to participate in the IPNg mailing list because
| the company I had just joined had an OSI stack, and one of the
| NG proposals was to bolt TCP on top of OSI's lower layers
| (TUBA). And this morning I spent some time on the phone to my
| ISP asking when/if they will roll out IPv6 in my area. 30 year
| span.
| dsr_ wrote:
| In 1994 I was talking to my colleagues about IPv6 and they
| asked how soon we would need to start transitioning. "Not
| this year," I said. "Maybe think about it next year in the
| budgeting process."
| bombcar wrote:
| IPv6 will roll out finally in 2049 or something, and
| immediately be replaced with IPv10.
| Bluecobra wrote:
| I believe that was around the time BGP migrated from v3 to
| v4 (CIDR support). It's pretty neat that change got pushed
| through so quickly. Granted the Internet was much smaller
| then (< 1500 AS's and 20K routes). Makes you think if work
| on IPv6 started earlier everyone could have migrated over
| in one swoop.
| 082349872349872 wrote:
| Obligatory t-shirt pairing: https://www.rightontheline.com/wp-
| content/uploads/2019/03/Sc...
| googlryas wrote:
| Never thought I'd see Cerf in a t-shirt. I just assumed he was
| born and would die in a 3-piece. The man made POTUS look like a
| schlub when he accepted his Medal of Freedom.
| shagie wrote:
| (dig dig dig...)
|
| The original tweet for any who want that link is
| https://twitter.com/webfoundation/status/1105425858913816576
|
| (scroll, scroll... oh neat)
|
| The back of the shirt is
| https://twitter.com/vgcerf/status/1105467776477679616
| VictorPath wrote:
| In thanks for his decades of work getting the Internet going,
| Postel spent the months before he died getting trashed by
| anonymous government officials in the Washington Post and
| elsewhere.
| rospaya wrote:
| Why was that?
| fanf2 wrote:
| There was a huge controversy over governance of the Internet,
| in particular the DNS, because it had become clear that
| Network Solutions had been handed a licence to print money as
| the monopoly controller of the DNS, and they were providing
| very poor service (filling in forms over email, very slow
| response times, $100 fees) and inconsistent enforcement of
| decency rules.
|
| Part of the response was the IAHC which came up with the
| template for the fix: break up the monopoly by splitting
| registries and registrars, force Network Solutions to
| relinquish some of its TLDs, and create more TLDs.
|
| https://en.m.wikipedia.org/wiki/IAHC
|
| This was not immediately successful, until Postel (as IANA)
| instructed the root DNS operators (other than Network
| Solutions) to get the root zone from IANA instead of from
| NetSol. This caused an _epic_ shitfest, as a result of which
| Postel reverted the root zone change, and the US NTIA got
| moving and started the foundation of ICANN.
|
| The company now known as Verisign is the direct successor of
| NetSol, and they still control .com and .net, and feed the
| root zone to the other root server operators.
| zwieback wrote:
| I started my coding career in the early 90s and at that time
| there were a buttload of non-TCP network protocols running on
| small computers (Macs, PCs, etc.) Netware, LANtastic, AppleTalk,
| Netbios stuff... Even though they all had something going for
| them I'm glad they have been steamrollered by TCP/IP
| johngalt wrote:
| To this day I think ATM was an interesting approach. Virtual
| circuit switching with quality of service capabilities designed
| into the protocol. If nothing else, it is a great example of a
| complex and optimized protocol losing vs a ubiquitous and
| simple protocol.
| kuon wrote:
| IPX worked very well for LAN games, it required no
| configuration. Compared to how difficult it is to play together
| now (steam friends. xbox...), it was much better.
|
| Of course it had drawbacks, but for that it was great.
| Wohlf wrote:
| TCP LAN games were also easy to set up.
| EamonnMR wrote:
| The difference between then and now is less protocol and more
| pervasive authentication.
| jandrese wrote:
| That's just LAN play dying off in favor of (routeable)
| Internet play. If developers wanted to they could add IP LAN
| play to games, but there's just not enough demand.
| contravariant wrote:
| I can see why it died off. There were preciously few ways
| to have LAN play over a distance without weird connection
| issues. At some point I recall that Hamachi did work fairly
| well, but that meant you still had to rely on a third party
| in the end.
|
| Even now it's only somewhat doable to do it without relying
| on 3rd parties by using wireguard. So I can see why relying
| on a third party became the default.
| Thlom wrote:
| I remember back in the 90's and early 00's my cousin and
| his neighbors had a neighborhood LAN going. They had
| stretched I believe Ethernet cables across the street and
| from house to house. It might actually have been coax
| cables in a ring network of some sorts. Anyway. They had
| an IRC server going and shared files and played games.
| Seemed like good times.
| bombcar wrote:
| The assumption is that if you're on an IP network, you
| already have addresses, etc (because you're routable to the
| internet).
|
| IPX/SPX worked without that assumption; it was bog simple
| to find some IPX cards, shove them in the computers,
| connect them, and go, even if you knew nothing.
|
| The closest for TCP/IP would be to support gaming over
| link-local links (those 169.* addresses) but everything is
| assumed to be on the internet now.
|
| And if you have TCP/IP for the internet, rarely do you care
| or need anything else for local comms.
| jandrese wrote:
| You could also do it over multicast.
|
| The big downside is that if some people are on WiFi then
| they'll be reduced down to 802.11b speed.
|
| A better solution would be to do server/player discovery
| via multicast and then stitch up unicast links for the
| actual gameplay.
| WorldMaker wrote:
| That's all IPX/SPX was was link local multicast. I see
| all the "no configuration" required love for it in
| surrounding comments, but I suppose few remember the
| failure states when it didn't work as expected, including
| drowning an entire switch (or worse token ring) in
| multicast noise. I know I hit IPX/SPX config hell a few
| times over the years in home LAN gaming, and I can't
| believe I was that alone in it, so I'm assuming the
| nostalgia goggles are in play in some of these "it just
| worked" memories.
|
| > A better solution would be to do server/player
| discovery via multicast and then stitch up unicast links
| for the actual gameplay.
|
| That's basically what most mDNS applications do today
| (the modern standards compliant name for used to be
| called Bonjour): use .local multicast for service
| discovery and then often use that to bootstrap to unicast
| links. It's not a bad way to go, with the only caveats
| that to get good mDNS support in Windows I believe that
| you still have to dig into WinRT components rather than
| old school Win32 sockets APIs and that especially seems
| to cramp many games from even trying to use it for LAN
| discovery today despite it being a mostly reliable
| standard in 2022.
| bombcar wrote:
| Most people did the "two cards connected" setup and let
| it work - or already had an IPX/SPX network setup and
| running and used that (Doom could crash them IIRC).
|
| Few people actually _built_ IPX networks, let alone
| routed them, etc.
| jandrese wrote:
| IMHO Bonjour/mDNS adds a lot of points of failure and
| doesn't really buy you much. It's so easy to just open a
| multicast listener port on a specific address and port
| and then just send out UDP packets to communicate.
| bombcar wrote:
| Yeah, anything actually doing it today will do something
| like multicast/bonjour and then do direct links.
|
| Though I have seen games that apparently use an internet
| service to coordinate direct links ...
| eklavya wrote:
| I seem to have never had a reliable and working mDNS on
| any OS. Would not recommend.
| bluedino wrote:
| Way back when I first started working for a small networking
| outfit, we were informally split into 'Team Red' and 'Team
| Blue'. Everyone agreed that Novell was on the way out, and
| the younger guys with their MCSE's made up most of Team Blue.
| I had un-officially started 'Team Yellow' and was sticking
| Linux boxes in when I could.
|
| Anyway...one afternoon I was at a law office installing some
| legal library software (or something), and one of the younger
| lawyers asked me into his office. He had a couple copies of
| Warcraft and Command & Conquer, he had installed them on a
| couple of the office computers but couldn't get network play
| going.
|
| Not really knowing what I was doing, I opened up the
| properties dialog for the network adapter, added the IPX/SPX
| protocol, and started the game up on two computers.
|
| It worked! It was that simple. I remember the guy pulling a
| $50 out of his wallet and handing it to me. And, since they
| were within walking distance of our office, I got invited
| back over a couple times and we played a lot of games (and
| drank a lot of beer) over there.
| rjsw wrote:
| I have AppleTalk compiled into the kernel on the machine I'm
| using to type this, have also done some work on adding CHAOSNET
| to it.
| didgetmaster wrote:
| I worked at Novell in the late 80s, early 90s. In the LAN
| world, IPX/SPX worked pretty well but it was certainly
| steamrolled by TCP/IP.
|
| Since I started out in the testing department, I not only had
| to deal with a bunch of protocols (IPX, NetBios, etc.) but I
| also had to deal with a bunch of stuff at the physical layer.
| Instead of everything being Ethernet, we had Token-ring and
| ArcNet cables running everywhere.
| zwieback wrote:
| Yup, I worked on a PC-to-Mac networking server product and we
| tested with TokenRing as well. Massive hardware but good
| performance. We also had a lot of coax wire in those days. To
| this day I still look down on twisted pair and the garbage
| Ethernet connectors we use now.
| anyfoo wrote:
| Electrically, there's not much reason to look down on
| Twisted Pair. It is an ingenuous way to achieve what coax
| does as an unbalanced transmission line with, well, a
| twisted pair of wires that form a balanced (differential)
| transmission line. You might need to add some shielding in
| some situations, but that's just a piece of foil.
|
| Most importantly, the two wires that make up the pair
| really just are common single-ended wires, not elaborate
| coax or anything else.
|
| A single coax transmission line supporting 10Gbps Ethernet
| would likely be much more expensive than the little bundle
| of twisted pairs we typically use nowadays.
|
| In many ways, for its applications, twisted pair and RJ45
| connections are better than coax wiring with BNC.
| cesarb wrote:
| > Electrically, there's not much reason to look down on
| Twisted Pair.
|
| Yeah, but mechanically, the RJ45 plug with its finicky
| easily breakable plastic tab can be an annoyance. And
| it's easy to see that the pin ordering is not ideal, with
| the pair in the middle splitting another pair. AFAIK,
| there exists a more robust connector (the M12 connector),
| but it doesn't seem to be that common.
| robocat wrote:
| > finicky easily breakable plastic tab
|
| That is not really the fault of the RJ45 specifications.
| The choice is available between cheap breakable
| connectors or reliable well-designed connectors: it isn't
| the fault of the specification that cheap is often
| chosen.
|
| > the pin ordering is not ideal
|
| A very minor nitpick. And designed that way for specific
| reasons.
|
| I like that it works well, was backwards compatible, and
| the connectors, wiring, and tools are cheap, available,
| and abundant. 1000Base-T is amazing technology (even if
| we are blase about it!)
| nomel wrote:
| I've been using multi-gig [1] over short runs of cheap
| cat 5 cable just fine. Actually, I only have one span
| that links at 5G. The rest are short enough for 10G with
| cat-5e, with 100m achievable with Cat-6! Talk about
| incredible!
|
| 1. https://community.fs.com/blog/what-is-multigig-
| ethernet.html
| anyfoo wrote:
| > And designed that way for specific reasons.
|
| Do you know that reason? I was wondering in my other
| reply.
| garaetjjte wrote:
| It's some legacy from scheme used in RJ connectors used
| in telephony, where first pair was on connector center
| and it continued outwards with each pair (like this,
| where each digit is pair: 4 3 2 1 1 2 3 4). T568 only
| retains this scheme for two pairs, maybe they realized
| that splitting last pairs across entire 8 pin connector
| would be unwieldy.
|
| Nothing stops you from wiring connectors different way
| though, to the annoyance of anybody splicing that cable
| in the future :)
| anyfoo wrote:
| True, the plastic tab can be annoying, but I guess the
| sheer abundance of patch cables nowadays means the
| cheapness of the connector, while retaining pretty good
| ease of use (better than many others), makes up for that
| drawback. Maybe something slightly more resilient could
| have been designed within the same parameters, had people
| known just how ubiquitous that connector would become.
|
| Maybe M12 is that, but it looks way more expensive at
| first glance. Possibly more laborious to
| connect/disconnect, too, with its screw-locking? Seems to
| be better for applications where a secured connection is
| more important (transportation is mentioned).
|
| And yeah, the 1000base-T pin ordering seems unusual. I'm
| curious about the history there, because even 10base-T
| (where I thought Ethernet for Twisted Pair begun) had
| this really weird pinout, which does not support my
| initial theory that it was because Ethernet kept
| progressively adding more differential pairs:
| https://www.arcelect.com/10baset.htm It may well be
| because they added the original two pairs to a pinout
| that already carried something else, but the diagrams
| don't say what those other lines were for, so if anyone
| knows...
|
| According to those same diagrams, though, it seems to be
| more common to split up the pairs than not, which now
| makes me wonder if there is any benefit to that?
| tmm wrote:
| > but the diagrams don't say what those other lines were
| for, so if anyone knows...
|
| Telephones. Telephones are why. Those other two pairs
| were often used for voice communication. If you had four-
| pair station cabling, the pairs were provisioned on the
| modular jack from the inside out. So line one was the
| blue/blue-white pair on the inner pins, line two was the
| orange/orange-white pair on the next two pins, and so on.
|
| Ethernet comes along and lots of places where you'd want
| a network connection already had a phone jack with two
| pairs unused, so for signal integrity reasons those are
| moved to the outside and used for data, leaving the inner
| two pairs where they were to be used for voice.
|
| But why 4 pairs in the first place?
|
| Just about the time that Ethernet was transitioning from
| coax to twisted pair, the digital PBX was taking over
| from key systems (1A2) and reduced the number of wires
| required for a business telephone from 25 pairs (or more
| ... secretarial sets often had 100 or more pairs) per
| station down to 4 (for HORIZON[0]) and later two pairs
| (DIMENSION and eventually Merlin, Definity, etc.). So if
| you're wiring a new building, you can just run one
| CAT-3[1] cable to each desk and use the first two pairs
| for voice and the second two for data[2].
|
| [0] OK, for the pedants out there, HORIZON wasn't ever
| very popular and really pre-dated Ethernet, but the
| telecom world moves kinda slow [1] Wasn't really CAT-3
| until the early 90s [2] Not on the same jack, but by
| using pins 1, 2, 7, and 8 for data, you can plug the
| wrong cable in without risk of hurting the phone or your
| computer's network card
| anyfoo wrote:
| That makes perfect sense now, thanks.
|
| > so for signal integrity reasons those are moved to the
| outside and used for data
|
| I'm not sure about that bit, though. Would keeping the
| pair together not help with signal integrity?
| toast0 wrote:
| I think the advantage of ethernet pinout vs always having
| adjacent pairs is that it can also be used for a two-line
| phone or token ring which both use the two inner pairs
| nested.
|
| I've seen somewhere that a pair of the two outer lines
| didn't have sufficient performance, so the outer pairs
| needed to wired side by side instead, but I don't have a
| reference. Also, there's a reasonable question of why use
| one inner pair and one outer pair, and not both inners or
| both outers.
| pavon wrote:
| I'm glad IP took over everything, but I wish that TCP hadn't
| become practically mandatory. There are some other really
| useful transport layer protocols, like SCTP that are great to
| use on a LAN, but good luck getting them to work on the
| internet. The only way to do anything other than TCP is to
| layer/tunnel it over UDP, and even that has less support than
| TCP.
| rjsw wrote:
| I'm part way through adding support for SCTP to the NetBSD
| firewall. Have done the basic filtering stuff, still working
| on doing NAT for it.
| jeffparsons wrote:
| Fortunately that era is coming to an end. With QUIC (layered
| on top of UDP) being the basis for HTTP/3, very few networks
| will outright block QUIC traffic as many have done with UDP.
|
| And my experience with QUIC so far has been delightful --
| it's everything I've wanted for decades when TCP was too
| restrictive and UDP too anaemic.
| msla wrote:
| Not to mention the Real Person All Grown Up Protocol Stack,
| OSI, which of course was going to displace this ARPANET
| childishness with protocols like the X.212 data link layer
| that, like all data link layer protocols, provides checksumming
| and resending and distinguishes between connection-oriented and
| connectionless communication, plus X.400 email which,
| naturally, uses the simple, comprehensible, easy-to-implement
| X.500 directory service, for email addressing inherently tied
| to your employer and physical address.
|
| Or OSI will crash and burn and we'll all pretend it was just a
| model from day one, and insist that TCP/IP is best understood
| using precisely the kind of strict layering the IETF explicitly
| rejected in RFC 3439. Y'know, whatever reinforces the notion
| that we never lose.
|
| https://www.rfc-editor.org/rfc/rfc3439
| anyfoo wrote:
| Heh, I remember attending trade shows in a time when X.400
| and X.500 were all the rage.
|
| Always a bad sign when another protocol comes along and calls
| itself "lightweight", as in LDAP, the "lightweight directory
| access protocol" merely based on X.500.
|
| SMTP is also the "simple" mail transfer protocol, but it's
| not based on X.400 in any way and was apparently replacing...
| FTP!
| arky22 wrote:
| dn3500 wrote:
| It was almost a non-event for us. I was at a university computer
| science lab. We were already running tcp/ip before the transition
| on our Vaxes. We had a TOPS-20 system but rather than transition
| it, we just retired it. We made very little use of the relay
| services.
| elurg wrote:
| So when is everybody transitioning to QUIC?
| arky22 wrote:
| davidwihl wrote:
| thatoneguy wrote:
| Meanwhile, Windows 95 didn't install TCP/IP by default when
| setting up a new network card. It was such a problem in the late
| '90s / early '00s still that it was an interview question for my
| university dial-up support job.
| bombcar wrote:
| That was right around the time of the Internet Memo of fame. At
| the time '95 came out it was HIGHLY argued what would take off
| (and for awhile it seemed AOL/CompuServe were winning).
|
| But the writing was already on the wall.
| glonq wrote:
| Ah, fond memories
| http://www.hawaii.edu/its/micro/pc/tcpip9x.html
|
| It _sucked less_ than fooling around with Trumpet Winsock on
| Win3.1 though!
| agomez314 wrote:
| Some background: new leadership at ARPANET demanded all hosts to
| switch from the old protocol (NCP) to the new one developed by
| Cerf and Kahn (TCP). This change caught many by surprise, and the
| migration was a long and painful one for teams. "The transition
| from NCP to TCP was done in a great rush...occupying virtually
| everyone's time 100% in the year 1982. _Nobody_ was ready "
| (Janet Abbate, Inventing the Internet, MIT Press 1999)
| AdamH12113 wrote:
| Needs a (2013).
|
| The article was posted on January 1, 2013, the 30-year
| anniversary of the deadline for ARPANET nodes to switch over to
| TCP. The next New Year's Day will thus be the 40th anniversary.
| agomez314 wrote:
| added. Thanks!
| jsight wrote:
| The parenthesis in the title confused me. What transition
| happened in 2013? Oh, the article was from 2013 but was about
| something that happened in 1982.
| samstave wrote:
| "Hi, I'd like to have a TCP transition."
|
| "Hello, would you like to have a TCP transition?"
|
| "Yes, I'd like to have a TCP transition."
|
| "OK, I'll get you a TCP transition."
|
| "Ok, I will have a TCP transition."
|
| "Are you ready to have a TCP transition?"
|
| "Yes, I am ready to have a TCP transition."
|
| Network Error (tcp_Error)
| jvanderbot wrote:
| Off topic:
|
| I met Vint Cerf at a Keck Institute for Space Studies [1]
| workshop on computing infrastructure in deep space. He was
| knowledgeable, energetic, funny, and volunteered to take notes
| for an all-day working session. The goal was to lay out
| requirements and benefits of flying servers to orbit around
| distant bodies for on-site analysis. You can get a _lot_ of data
| from cameras, but you can 't send _nearly any_ of it back, so do
| interactive data reduction on site, right?
|
| He was at Google Loon at the time, working on their delay-
| tolerant networking & dynamic routing for their baloon-internet
| architecture. He's been super active in the NASA community
| working on their delay-tolerant networking architecture. The
| whole stack is really beautiful. In space, you know when nodes
| are coming over the horizon because they are in regular orbit, so
| you can plan routes for the future using "contact-graph routing",
| and use store-and-forward to massively increase throughput.
| (e.g., orbiters hold data automatically until they are in sight
| of the next hop). Nothing you can do about latency, with speed of
| light and all that though :) JPL has an open-source
| implementation maintained by Scott Burleigh, another really neat
| person, and I think JHU/APL does too. [2]
|
| Anyway. The guy is smart, sure, but he's also immediately
| influential: You can't help but agree with him when he pushes
| these simple, effective ideas naturally.
|
| 1. https://kiss.caltech.edu/
|
| 2. https://sourceforge.net/projects/ion-dtn/
| EddySchauHai wrote:
| He gave a talk at a company I used to work at on the history of
| the internet and his thoughts on its future, it was really cool
| to listen to him talk on these subjects!
| nominusllc wrote:
| I'd love to see a video of this. Unfortunately archive.org is
| drawing a blank on this name. Do you perhaps have a link you
| can share to slides or video?
| jedberg wrote:
| > Nothing you can do about latency, with speed of light and all
| that though
|
| Why do we take this for granted? I understand the laws of
| physics and all, but 120 years ago we didn't think humans could
| fly through the air, and now we have a million+ humans flying
| every day, and occasionally one goes to outer space.
|
| Why do we consider communication faster than the speed of light
| so unbreakable?
| [deleted]
| tialaramex wrote:
| "The speed of light" is probably not what you think it is.
|
| This constant, c, is actually about how time (one of our four
| dimensions, often labelled t) is related to the three spatial
| dimensions (often x, y, z).
|
| Light goes that fast (in a vacuum) because from the light's
| point of view that's how those dimensions are related, it's
| not really a "speed limit" it's up against, any more than
| you'd consider it a "time limit" that hours have sixty
| minutes in them. The light is just moving through time as
| well as space, and that's how it has to work.
|
| So, because it's about the relationship between time and
| space, what you're talking about with "faster than light" is
| actually a time machine.
|
| Now, you might notice that before the aeroplane there were
| birds (and bats, and insects, but lets focus on birds).
| Clearly flying _is_ possible, a sparrow can do it. But you
| may have noticed from the lack of time travelling visitors
| that _time travel_ does not seem to be possible.
| jedberg wrote:
| I knew that about the speed of light (but thank you for
| writing it out). My knowledge of entanglement is limited,
| but haven't we observed entangled particles seemingly
| communicate faster than light?
|
| While time travel may not be possible, maybe time traveling
| data is?
| dsr_ wrote:
| No, we have not.
|
| We have observed that we can generate a pair of particles
| and separate them, and when we look at the close one, we
| now know that the far one has the complementary property.
| You can't use that to send information. You could use it
| as a shared secret, but you still had to move the
| particle out where your recipient is for them to use it.
|
| You can take a flashlight and shine it at the moon, and
| if you sweep the beam back and forth, you can make the
| notional front of illumination move faster than the speed
| of light -- but you can't modulate the signal faster than
| the propagation velocity c.
|
| Time travel into the future is easy. Time travel into the
| past doesn't work in this universe.
| ynik wrote:
| Entanglement doesn't involve any form of communication.
|
| Only the imaginary "wave function collapse" is faster
| than light. But collapse isn't actually part of quantum
| mechanics: there's no formula that would tell you when
| collapse is triggered. The many world interpretation
| doesn't have any wave function collapse at all; and it's
| a valid interpretation of the underlying maths. Any "wave
| function collapse" is merely an interpretation trick to
| map the quantum world back to the classical world as
| experienced by humans. You can't build technology out of
| imaginary physics.
| tambourine_man wrote:
| Nope, it's a common misunderstanding. While the particles
| are entangled regardless of distance and the action is
| instantaneous (at least, that's one way of interpreting
| it) there's no way to actually transmit information.
|
| You may try to come up with clever encodings for electron
| spins, but you'll see that you end up having to know a
| priory what the other end had. It's a long topic to
| discuss on a HN thread but a quick YouTube search will
| get you interesting videos.
| nly wrote:
| If time travel isn't possible how come we're all moving
| in to the future right now?
| teddyh wrote:
| "If flying is impossible for me after I have jumped off
| this tall building, how come I am currently moving
| through the air towards the ground at high speed?"
| didgetmaster wrote:
| The lack of time travelling visitors may only indicate that
| 'backward' time travel is not possible. It could be that
| 'forward' time travel will be possible sometime in the
| future. (And by 'forward', I mean faster than the normal
| movement through time we all do every nanosecond)
| dagss wrote:
| Entering and awakening from a coma comes pretty close...
| gpderetta wrote:
| That's relatively trivial by going at relativistic speed.
| AnIrishDuck wrote:
| This is even a thing at non-relativistic speeds.
|
| Proper operation of GPS requires a time correction [1]
| because the system's satellites are moving at significant
| speed from the perspective of ground observers. Their
| onboard clocks are therefore moving relatively faster
| through space, and thus relatively slower through time.
|
| This is measurable at the nanosecond scale, and must be
| taken into account every time something uses GPS.
|
| 1. https://www.astronomy.ohio-
| state.edu/pogge.1/Ast162/Unit5/gp...
| [deleted]
| arccy wrote:
| We've been flying with hot air balloons for over 200 years,
| and we've seen birds (heavier than air) fly. It's always been
| considered possible, we just didn't know how to apply that to
| humans.
|
| We still haven't seen anything in nature that even hints to
| the possibility of faster than light
| recursive wrote:
| Considering it breakable probably doesn't get you much. Ok,
| it's breakable. Now we just have no idea what to do. If
| anyone could demonstrate a proof of concept, I'm sure we'd be
| considering it much more broadly.
| snowwrestler wrote:
| It's not so much that we take it for granted, the issue is
| there is so far no contradicting evidence. Humans could see
| other animals flying, but we don't see things going faster
| than the speed of light.
| t-3 wrote:
| > we don't see things going faster than the speed of light.
|
| That would be physically impossible to see in the first
| place, wouldn't it?
| pixl97 wrote:
| We would see some side effect of it depending on the
| exact nature of reality and time. Since we don't see
| things from the future randomly appearing now, nor do we
| have cherenkov radiation occurring in places that it
| shouldn't in open space it seems unlikely FTL is
| occurring.
| fbanon wrote:
| 120 years ago we knew that some things can fly, because we
| saw birds. We just had to figure out how to do the same with
| humans.
|
| On the other hand, we have never encountered anything in
| nature that goes faster than the speed of light. That's a
| pretty good hint that it's impossible to do so.
| Jtsummers wrote:
| People had flown before the first powered flights, so 120
| years isn't a good measure for that. You probably have to go
| back a lot further to find natural philosophers or physicists
| asserting that manned flight was totally impossible. Maybe
| claims that heavier than air vehicle couldn't fly would be
| more recent.
|
| Hot air balloons had been around since the 1700s, and gliders
| were developed in the 1800s. Those were the first "heavier
| than air" aircraft, and a manned glider was flown by the end
| of the 19th century. Powered flight was an extension of that
| model.
|
| We have no model of faster than light communication (or
| travel) that holds up to scrutiny, let alone has been
| demonstrated.
| gpderetta wrote:
| Also birds.
| mecsred wrote:
| Even if we could go back 120 years, just knowing it's
| possible to create aircraft doesn't do much without the
| domain knowledge to build one.
|
| FTL may or may not be possible via physics we don't
| understand. Until we have that physics and a system to
| exploit it FTL is a very real constraint to work around.
| Don't mistake "Nothing we can do" for "nothing we can ever
| do".
| zasdffaa wrote:
| The only reason to post this is to troll.
| jedberg wrote:
| Based on the downvotes I'm getting, it would appear a bunch
| of people agree with you, but I promise it is not. I
| genuinely want to understand why we consider this an
| unbreakable limit when we have in the past broken
| previously thought "unbreakable" limits.
| zasdffaa wrote:
| Ok I take your bona fides but why not just search? There
| are 186,283 sites covering this, so a quick <https://html
| .duckduckgo.com/html?q=why%20speed%20light%20lim...>
| would have helped avoid irritating people, I mean you now
| have more info at your fingertips than any 10,000 people
| had collectively up until say 1980 and you don't even
| type a query?
| jvanderbot wrote:
| Never mind any down-votes, this is a reasonable question, and
| many here at HN would relish the opportunity to answer.
| shagie wrote:
| As an aside, the PBS space time video The Speed of Light is
| NOT About Light : https://youtu.be/msVuCEs8Ydo
|
| As an aside to the aside - as I rewatch it I quickly notice
| how young he looks (and then note the date is 2015 on there -
| one of the early ones and the production is less refined).
|
| You may also like The Geometry of Causality
| https://youtu.be/1YFrISfN7jo
| ynik wrote:
| Because of relativity. The speed of light is also the speed
| of causality. Assuming the theory of relativity isn't totally
| wrong, then if faster-than-light communication is possible,
| then so must be time travel.
| http://www.physicsmatt.com/blog/2016/8/25/why-ftl-implies-
| ti...
| rightbyte wrote:
| Why would information of an event, e.g. light bulb lit up
| by pushing breaker, decide the causality? Can't you just
| back track from a model that the breaker is closed then the
| bulb lits up?
| moomin wrote:
| The bulb lights up _after_ you close the breaker.
| dboreham wrote:
| > Why do we consider communication faster than the speed of
| light so unbreakable?
|
| Because it's the definition of the simulator we inhabit. c
| isn't some random thing to do with light that we observe and
| find curious, it's literally the nature of the universe. The
| universe is "a place where the speed you can propagate
| information is : c". The speed of light follows from that,
| not the other way around.
|
| So if that's breakable, then we made some very big invalid
| assumptions over the past 200 years.
|
| Also, it's questionable that "we didn't think humans could
| fly through the air". Obviously some people did think that
| was possible, otherwise they wouldn't have tried to do so. We
| had birds and bats as existence proofs too. And balloons.
| NateEag wrote:
| A combination of pragmatism and hubris.
|
| pragmatism: our best current theories about the universe
| suggest that the speed of light is a constant. Until someone
| proposes a theory with more explanatory power that suggests
| otherwise, we might as well do our work with the assumption
| that it's correct.
|
| Hubris: our best theories are clearly not complete (see dark
| matter, conflicts between general relativity and quantum
| mechanics, and similar), yet we mostly treat them not as
| provisional theories subject to change, but as ironclad laws
| by which we may live our lives. Humans don't do well with
| uncertainty.
|
| (Disclaimer: not everyone lives that way. As far as I can
| tell most who do have something like this combination of
| ideas in their heads.)
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