Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[Ozle]

GPS technology has a built in limit, generally around 1200mph, after which it shuts off.
This is to prevent it being used to guide balistic missiles.

[Davio]

Well, that's odd as GPS was created by the US department of Defense. You would think that guiding ballistic missiles was just the purpose they had in mind.

[soulnet]

GPS technology has a built in limit, generally around 1200mph, after which it shuts off.
This is to prevent it being used to guide balistic missiles.

Even with that power cap, I think it should cost at least $5.

[Kirian]

Ozle's "fact" of the day

[Watno]

I can't believe i actually bought this until Kirian's comment.
Then I thought about how GPS works...

[Ozle]

http://en.wikipedia.org/wiki/CoCom

http://blog.jgc.org/2010/11/gaga-1-cocom-limit-for-gps.html

[Kirian]

Let's qualify this then, thanks to one of the references on the Wiki page: US-built GPS systems that are qualified for export must follow these limits, per the FAA and FCC.  Pretty certain that doesn't apply to missiles we build.  I guess those are technically meant for "export" but I don't think that part matters.

[Ozle]

its quite interesting, because I went form the GPS page to CoCom and then found out what the CoCom countries were, and then onto the companies like Toshiba that broke the agreement

[Witherweaver]

So, is Ozle going to nuke us?

[Ozle]

So, is Ozle going to nuke us?

If I could do you not think it would have happened by now?

Im quite accident prone....

[Kirian]

its quite interesting, because I went form the GPS page to CoCom and then found out what the CoCom countries were, and then onto the companies like Toshiba that broke the agreement

I'm shocked, SHOCKED I say, to hear that companies broke this agreement.  Next you'll tell me Google is passing information on to the US government!

[Witherweaver]

So, is Ozle going to nuke us?

If I could do you not think it would have happened by now?

Im quite accident prone....

You could simply be biding your time, luring us into a false sense of security...

[Ozle]

its quite interesting, because I went form the GPS page to CoCom and then found out what the CoCom countries were, and then onto the companies like Toshiba that broke the agreement

I'm shocked, SHOCKED I say, to hear that companies broke this agreement.  Next you'll tell me Google is passing information on to the US government!

I wouldn't dream of saying that (they might be listening...)

[Ozle]

So, is Ozle going to nuke us?

If I could do you not think it would have happened by now?

Im quite accident prone....

You could simply be biding your time, luring us into a false sense of security...

This would imply a subtlety that I am not capable......plus if one has nukes, one does not need to be careful (Ancient Chinese Proverb)

[Awaclus]

So, is Ozle going to nuke us?

If I could do you not think it would have happened by now?

Im quite accident prone....

You could simply be biding your time, luring us into a false sense of security...

Why would he need to lure us into a false sense of security if he can just nuke us?

[Witherweaver]

So, is Ozle going to nuke us?

If I could do you not think it would have happened by now?

Im quite accident prone....

You could simply be biding your time, luring us into a false sense of security...

Why would he need to lure us into a false sense of security if he can just nuke us?

It's more fun that way, obviously.  Same reason why the Bond villains feel the need to divulge their evil plot instead of just killing Bond.

[theory]

Well, that's odd as GPS was created by the US department of Defense. You would think that guiding ballistic missiles was just the purpose they had in mind.

GPS, although accessible to civilians since Reagan's order following KAL-007, wasn't ubiquitously useful until 2000.  The DOD intentionally degraded the GPS signal so that (theoretically) only the U.S. military had access to accurate GPS.  Clinton ordered this policy (Selective Availability) turned off in 2000, as the DOD had developed other methods of denying GPS on a regional basis, and civilian technology was beginning to develop workarounds anyway.  (Which is why Russia / China are actively launching their own "GPS" satellites.)

In other words, it is not unprecedented to have a separate "civilian GPS" and "military GPS".  The relevant rule is that all U.S. GPS receivers for export must either a) shut off above 11km in altitude and 515 m/s; or b) be classified as a weapon requiring a State Department export license.

[Ozle]

Europe is also about to launch its own, more accurate GPS

http://en.wikipedia.org/wiki/Galileo_(satellite_navigation)

[Teproc]

About to ? It's been 10 years or so since I first heard about Galileo. I assumed it had been buried long ago.

[Ozle]

About to ? It's been 10 years or so since I first heard about Galileo. I assumed it had been buried long ago.

I hope not, my company is doing a lot of the mission critical programs...

From Wiki....
The first two Galileo In-Orbit Validation satellites were launched by Soyuz ST-B flown from Guiana Space Centre on 21 October 2011,[31] and the remaining two on 12 October 2012.[32]
All further satellites will have Full Operational Capability (FOC). 22 are now on order, with the first two due to be launched together on a Soyuz rocket from French Guiana midway through 2014.

[Kirian]

About to ? It's been 10 years or so since I first heard about Galileo. I assumed it had been buried long ago.

I hope not, my company is doing a lot of the mission critical programs...

So Ozle does work on satellites!

[Ozle]

About to ? It's been 10 years or so since I first heard about Galileo. I assumed it had been buried long ago.

I hope not, my company is doing a lot of the mission critical programs...

So Ozle does work on satellites!

I'm just the Janitor...

[Witherweaver]

So on the subject of GPS, we all know that clocks in orbit around the Earth will run faster (apparently the calculations show about 38 microseconds) compared to clocks on the surface of the earth.  This is due to relativistic gravitational effects (and from the satellites traveling quickly).  Apparently there is some disagreement on whether this time discrepancy is actually relevant and accounted for.  E.g., http://www.alternativephysics.org/book/GPSmythology.htm.  Doing random searches about GPS and relativistic effects, I ran across a number of things, including arguments with people that apparently don't believe Einstein.

Anyone know much about this?

[Ozle]

Damnit, i hate it when people hijack threads and take them off into different non-relevant directions!

[Kuildeous]

So, is Ozle going to nuke us?

If I could do you not think it would have happened by now?

Im quite accident prone....

You could simply be biding your time, luring us into a false sense of security...

That's what Ozle gets for storing his nuke codes in Goko.

[Kirian]

So on the subject of GPS, we all know that clocks in orbit around the Earth will run faster (apparently the calculations show about 38 microseconds) compared to clocks on the surface of the earth.  This is due to relativistic gravitational effects (and from the satellites traveling quickly).  Apparently there is some disagreement on whether this time discrepancy is actually relevant and accounted for.  E.g., http://www.alternativephysics.org/book/GPSmythology.htm.  Doing random searches about GPS and relativistic effects, I ran across a number of things, including arguments with people that apparently don't believe Einstein.

Anyone know much about this?

Yeah, there are actually people out there who don't believe in relativity, much as there are people who don't believe in evolution or that the Earth is an oblate spheroid.  None of these people are actual scientists.

Actual scientists understand that relativity is still an incomplete theory, much in the same way that Newton's Laws were incomplete.  Oddly though you don't see many people arguing against Newton's Laws.

TLDR version:  Those people are morons, and yes GPS engineers account for relativity.

[theory]

[initial discussion on relativity ninja'd by Kirian]

On a related but amusing note, your smartphone has two clocks inside of it: the system clock and the GPS clock.  The two are exactly and deliberately 16 seconds out of sync.

[Ozle]

[initial discussion on relativity ninja'd by Kirian]

On a related but amusing note, your smartphone has two clocks inside of it: the system clock and the GPS clock.  The two are exactly and deliberately 16 seconds out of sync.

oi! Get your own fact of the day thread!

Oh go on then, you can share.....why are they 16 seconds out on purpose?

[soulnet]

[initial discussion on relativity ninja'd by Kirian]

On a related but amusing note, your smartphone has two clocks inside of it: the system clock and the GPS clock.  The two are exactly and deliberately 16 seconds out of sync.

Is a clock really cheaper than a circuit that adds 16?

[Witherweaver]

So on the subject of GPS, we all know that clocks in orbit around the Earth will run faster (apparently the calculations show about 38 microseconds) compared to clocks on the surface of the earth.  This is due to relativistic gravitational effects (and from the satellites traveling quickly).  Apparently there is some disagreement on whether this time discrepancy is actually relevant and accounted for.  E.g., http://www.alternativephysics.org/book/GPSmythology.htm.  Doing random searches about GPS and relativistic effects, I ran across a number of things, including arguments with people that apparently don't believe Einstein.

Anyone know much about this?

Yeah, there are actually people out there who don't believe in relativity, much as there are people who don't believe in evolution or that the Earth is an oblate spheroid.  None of these people are actual scientists.

Actual scientists understand that relativity is still an incomplete theory, much in the same way that Newton's Laws were incomplete.  Oddly though you don't see many people arguing against Newton's Laws.

TLDR version:  Those people are morons, and yes GPS engineers account for relativity.

So I guess I should have looked at the actual URL and the home pages of such sites. 

[Witherweaver]

Damnit, i hate it when people hijack threads and take them off into different non-relevant directions!

This was completely a relativistic direction!  I don't know what you're complaining about!

[theory]

Most clocks use UTC time, which has leap seconds, designed to correct for the fact that the Earth is very inaccurate in its rotation.  GPS time was synchronized with UTC in 1980 but has not subsequently added leap seconds or otherwise corrected for Earth's rotation.  It is likely that the UTC and GPS will further diverge in the future.

[soulnet]

Most clocks use UTC time, which has leap seconds, designed to correct for the fact that the Earth is very inaccurate in its rotation.  GPS time was synchronized with UTC in 1980 but has not subsequently added leap seconds or otherwise corrected for Earth's rotation.  It is likely that the UTC and GPS will further diverge in the future.

Ok, so when you say 16 seconds away it actually means that they are now 16 seconds away, not forever 16 seconds away? I misinterpreted that.

[Ozle]

Most clocks use UTC time, which has leap seconds, designed to correct for the fact that the Earth is very inaccurate in its rotation.  GPS time was synchronized with UTC in 1980 but has not subsequently added leap seconds or otherwise corrected for Earth's rotation.  It is likely that the UTC and GPS will further diverge in the future.

Ok, so when you say 16 seconds away it actually means that they are now 16 seconds away, not forever 16 seconds away? I misinterpreted that.

yeah, this is what I assumed as well.

Makes much more sense now. Thanks.

Will this still be the case when I move my clock forward so I can cheat at Candy Crush though?

[SirPeebles]

...to correct for the fact that the Earth is very inaccurate in its rotation.

Indeed.  Earth had better get its act together are start accurately matching our simple models.

Also, Earth needs to work out more.  It is bulging around the waist.

[soulnet]

Also, Earth needs to work out more.  It is bulging around the waist.

Work out more? Are you out of your mind? It is already burning carbs and sweating like there is no tomorrow! If it keeps it up like this, there won't be.

[florrat]

Most clocks use UTC time, which has leap seconds, designed to correct for the fact that the Earth is very inaccurate in its rotation. 

I'm not sure if I'm correct, but what I've heard was that leap seconds have nothing to do with inaccuracy. Leap seconds happen because the Earth's rotation is slowing down (every day is a little longer than the previous one, about 60 nanoseconds shorter). This slowing down happens because the Moon causes a lot of water to move around the planet every day (known as the tides), which causes a lot of friction. This will lower the angular momentum of the earth slowly, causing days to become slightly longer.

So the days are now on average a little longer than 24*60*60 seconds, which means that we have to add a second every couple of years. Since days become longer and longer (but of course this will be in the order of milliseconds) we have to have leap seconds more frequently in the future.

[Witherweaver]

Also, Earth needs to work out more.  It is bulging around the waist.

Work out more? Are you out of your mind? It is already burning carbs and sweating like there is no tomorrow! If it keeps it up like this, there won't be.

Maybe, but it's slowing down.  Why, I remember just a few hundred years ago it was spinning a few microseconds faster.  It's been riding on its coat tails for millennia.  Plus it garbles up calories from the sun. 

[Witherweaver]

Most clocks use UTC time, which has leap seconds, designed to correct for the fact that the Earth is very inaccurate in its rotation. 

I'm not sure if I'm correct, but what I've heard was that leap seconds have nothing to do with inaccuracy. Leap seconds happen because the Earth's rotation is slowing down (every day is a little longer than the previous one, about 60 nanoseconds shorter). This slowing down happens because the Moon causes a lot of water to move around the planet every day (known as the tides), which causes a lot of friction. This will lower the angular momentum of the earth slowly, causing days to become slightly longer.

So the days are now on average a little longer than 24*60*60 seconds, which means that we have to add a second every couple of years. Since days become longer and longer (but of course this will be in the order of milliseconds) we have to have leap seconds more frequently in the future.

It's only slowing down on average.  The rotational speed actually fluctuates, and certain events (earthquakes) can make a difference.  I think that's what he meant by inaccurate in its rotation.

http://en.wikipedia.org/wiki/Earth's_rotation#Changes_in_rotation

[theory]

Most clocks use UTC time, which has leap seconds, designed to correct for the fact that the Earth is very inaccurate in its rotation. 

I'm not sure if I'm correct, but what I've heard was that leap seconds have nothing to do with inaccuracy. Leap seconds happen because the Earth's rotation is slowing down (every day is a little longer than the previous one, about 60 nanoseconds shorter). This slowing down happens because the Moon causes a lot of water to move around the planet every day (known as the tides), which causes a lot of friction. This will lower the angular momentum of the earth slowly, causing days to become slightly longer.

So the days are now on average a little longer than 24*60*60 seconds, which means that we have to add a second every couple of years. Since days become longer and longer (but of course this will be in the order of milliseconds) we have to have leap seconds more frequently in the future.

It's only slowing down on average.  The rotational speed actually fluctuates, and certain events (earthquakes) can make a difference.  I think that's what he meant by inaccurate in its rotation.

http://en.wikipedia.org/wiki/Earth's_rotation#Changes_in_rotation

Correct.  On average it is slowing down, but it is slowing down erratically, like a drunk determined to make it to the streetlamp.

[SirPeebles]

today's xkcd feels relevant.

[Ozle]

-----------------------------------------------------

FACT OF THE DAY


The world Limbo record is 8.5 inches!

[SirPeebles]

Set the bar pretty low for today's fact.

[Kuildeous]

Set the bar pretty low for today's fact.

Oh, SirPeebles. Jamaican me crazy!

[Ozle]

Ohh yes, new fact:


If you take all of the space out of all of the people in the world. The remaining atoms would all fit into the size of a sugar cube

[KingZog3]

Ohh yes, new fact:


If you take all of the space out of all of the people in the world. The remaining atoms would all fit into the size of a sugar cube

Doesn't that apply for everything on the planet, not just people? Maybe even all the matter in the universe. It's something crazy like that.

[Kirian]

Ohh yes, new fact:


If you take all of the space out of all of the people in the world. The remaining atoms would all fit into the size of a sugar cube

Can I assume you mean "all the remaining particles"?  Because the whole point of the "empty space" thing is that individual subatomic particles are incredibly small compared to atomic volumes.  But calling the remaining atomic volume "empty space" is just horribly incorrect.

But assuming that's what you meant, we're talking a factor (volume) of 10¹⁵.  At that factor, humanity scales down to about 0.3 mL... definitely smaller than a sugar cube.

[Ozle]

Hmm, yes it should have been particles.

But upon further research prompted by your comment I don't like this one.

Lets strike it form the record and i'll try again

[Kirian]

Hmm, yes it should have been particles.

But upon further research prompted by your comment I don't like this one.

Lets strike it form the record and i'll try again

Eh, it's all right.  I mean, it formed the premise of one OK movie (Honey I Shrunk the Kids) and two terrible sequels.

[Ozle]

Hmm, yes it should have been particles.

But upon further research prompted by your comment I don't like this one.

Lets strike it form the record and i'll try again

Eh, it's all right.  I mean, it formed the premise of one OK movie (Honey I Shrunk the Kids) and two terrible sequels.

And a TV show apparently!

[Kuildeous]

Hmm, yes it should have been particles.

But upon further research prompted by your comment I don't like this one.

Lets strike it form the record and i'll try again

Eh, it's all right.  I mean, it formed the premise of one OK movie (Honey I Shrunk the Kids) and two terrible sequels.

And a TV show apparently!

And a ride!

/never been

[Ozle]

#### Fact of the Day  ####

Butterflies taste through their feet

http://www.butterfliesandart.com/Butterfly_Facts/Butterfly_Facts.htm

[Witherweaver]

#### Fact of the Day  ####

Butterflies taste through their feet

http://www.butterfliesandart.com/Butterfly_Facts/Butterfly_Facts.htm

I think these should be phrased in the form of a Fun Fact Frog meme:

http://www.livememe.com/sflznlt (e.g.)