What would happen if all satelites went down for a day?

[pcm81]

What would happen if all satellites went down for a day? I'd guess that bitcoin network in US and other isolated parts of the world would see a sharp drop in hash rate, but the blocks would still be generated... as the result, when communication is re-establishes itself, would we have many separate chains/networks?

Also, as we get into fpga and ASIC mining, there is a potential for concentrating the network hash power in fewer locations than the more distributed gpu network, since not as many people would have fpga/asic as there are people who mine on gpus. So, if a natural disaster cuts the power off, say in north east, wouldn't geographically centered team, say in mid US have a high probability of having over 50% compute power?

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[DeathAndTaxes]

There are very few countries which don't have land (and under sea) links to other countries.  For the US there are well over 300 independent fiber optic links to other countries and continents.  All the sats could fall out of the sky tomorrow (and forever) and for 95%+ (# pulled out of my ass) of users "the internet" will continue just fine.   Sat is being used less even for voice communication.  Since voice can be digitized and carried on packet networks all that massive build out in capacity is killed sat utility.  Really sat has been marginalized to only remote fringes of the world, at sea (ships), low bandwidth, high geography applications (like Exxon linking up 4,000 gas stations), and where artificial barriers to entry prevent free market forces (telecom monopolies in smaller emerging market countries).

[Stephen Gornick]

I'd guess that bitcoin network in US and other isolated parts of the world would see a sharp drop in hash rate, but the blocks would still be generated... as the result, when communication is re-establishes itself, would we have many separate chains/networks?

Continuous connectivity is required to mine and is required by an exchange, merchant and individuals who trade and need to protect against double spending.

As D&T explains the Internet does not have regions that get isolated from each other as you describe, but for the sake of argument let's assume that can happen.  

So region A has 10 Thash/s of capacity and the rest of the regions that are not connected to (i.e., cannot route to) A have a total of 15 Thash, but none larger than 5 Thash/s and none have any connection anywhere to each other nor to region A.

The first thing that will be noticed by all participants everywhere is that blocks are taking about 25 minutes (region A) to an hour (other regions) to solve instead of the normal 10 minutes.   Since those in any one region don't know whether their region will emerge as having the most hashing capacity, those merchants, exchanges, individuals etc. might be wise to stop accepting payment in bitcoins from untrusted parties until a better assessment can be ascertained.

What will likely happen is at least one node in each the other disconnected regions will establish connectivity with a node in region A (even if it is a dial-up connection) and there are then no more disconnected regions (as one node in a specific region can successfully relay all blocks and transactions thus joining the formerly disconnected regions with region A.)

So can wide outages disrupt the ability to transact with bitcoin? Sure.   Could bitcoins be lost due to a 51% attack during such an outage?  Well, bitcoins aren't lost unless there was fraud intentionally perpetrated by a party with 51%.   There's probably even less chance of success because there would be a heightened sense of awareness. i.e., an exchange might suspend all outgoing bank wires and withdrawals until the communications issues are resolved.

Remember, that if there's no connectivity, there's no connectivity -- so there is also no VISA, Mastercard, Bank (ATM), Gmail, Facebook, Salesforce.com, IRS.gov, Wikipedia, Netflix, etc.   There would be pretty steady progress in re-establishing connectivity is nearly every instance.

Here's a related thread on the subject of what is available for an isolated region:

Desert island economy on Bitcoin without being connected to the internet?
 - http://bitcointalk.org/index.php?topic=106302.0

[2112]

What would happen if all satellites went down for a day?

Pretty close to a complete communications blackout. Vast majority of fiber optic links are synchronous with the clocks synchronized off of the GPS (or equivalents). If you disable GPS the clocks will drift off in less than a day and the communication will cease. Obviously rich countires have access to multiple precise atomic clocks (cesium, rubidium) and will be able to restore operation of some most critical fiber-optic links. Poorer countries will have to make do with the old radio-stabilized quartz oscillators.

The quickest to fail will be all CDMA carriers (Verizon,Sprint,etc.) because of high required timing precision. GSM carriers (ATT,T-Mobile) will fare better. Various 4G and 3G schemes will fail even faster, but almost all wireless cariers have the above older systems as a backup.

The old style T1/T3 connections (E1/E3 in Europe) will last the longest because they operate plesiochronously.

Afterwards there will be a great amount of energy spent to fix this vulnerability. But the current situation is as described: GPS stabilized clocks are everywhere.

http://www.chronos.co.uk/files/pdfs/wps/Dependency_of_Comms_on_PNT_Technology.pdf