Did the military top-brass behind the GPS system really doubt relativistic effects ?

The cite for that comment is from:
Proper time experiments in gravitational fields with atomic clocks, aircraft, and laser light pulses
From Volume 94 of NATO advanced science institutes series: Physics
By Carroll O. Alley

I guess to actually answer this Q you’d have have access to this undoubtedly fascinating very readable tome :slight_smile:

Handheld was a long time coming. In 1985 I interviewed at TI in McKinney, TX and was shown the current state of the art GPS receiver, which was about the size of a footlocker. They were working on the next generation, which was to be a bit smaller, but mostly lower power consumption. They were hoping that in another generation or two, they could get them small and light enough to put on fighter aircraft. Handheld wasn’t even in the realm of reality. Yes, I marvel that a GPS is just a small subsystem of today’s phones.

Hm, OK. I saw an early prototype GPS some time around the early 90s, and it was about the size of a very large brick. I wasn’t aware that there was an earlier generation than that.

Oh, and from the link Francis Vaughan posted:

That uncertainty would be from people taking into account the special relativistic effect from the speed, but leaving off the gravitational effect (which is larger and in the opposite direction). I’ve seen textbooks, even, that consider the SR-only effect to be the “right” answer.

I remember some publicity shots of a soldier carrying a backpack sized GPS sometime in the 80s. It was called a breakthrough in making GPS portable.

This story is horseshit from beginning to end. The theory of relativity is over a century old at this point re relativistic effects on objects orbiting the earth. Pretending US military staff handing the implementation of cutting edge systems weapons are scientific buffoons may make for a good story, but it’s bad history.

Handheld GPS units certainly existed in the early 90’s. My father bought a Sony Pyxis 360 in about 1991 and it was very much a handheld. The antenna was larger than the base unit (and you could separate them to install the base unit inside a car with the antenna outside.) It ate batteries. We bought it from the store at the local aero club, and they were already quite popualr with pilots of light aircraft, although they were not rated for nav use.
Pic here includes other early 90’s handhelds.

Gotta share this story I heard at a lecture by Adm Grace Hooper, one of the creators of COBOL. She demonstrated it to the “top brass” and explained that it allowed programs to be written in a manner similar to natural English language. They were very impressed. Then she went on to say that it could just as easily be programmed to understand French words. At that point they stopped her and said that they could see how they could teach a computer how to understand English, but there was no way a computer could understand French.

She was a brilliant woman and a great story teller, and I suspect that she was taking a bit of license with the actual truth.

I can readily imagine a perfectly intelligent, well-educated non-specialist wanting to be sure that correcting for relativistic effects is not over-engineering for the sake of it - creating delay or spending a potentially large sum of money to make a correction that might be so small as to be lost in noise.* A foritiori *if there was uncertainty as to magnitude and even sign (as suggested above).

That doesn’t mean such a person doesn’t believe in relativity, but I can also easily imagine a story like that as the root of an urban legend that loves to assume all military officers are Col Hap Hapablap. These stories always press the “truthiness” button because it is fun to believe them, but the temptation really should be resisted.

In 1994 I was working for a company that was making GPS car navigation systems. Very primitive, compared to what are out there today, but still, they existed.

Based on the cite quoted above, I am wondering if there is more truth to this than I initially though, it definitely seems like some people “doubted that relativistic effects were truths that would need to be incorporated”. Who exactly those people were however is not clear.

An awful lot of WAGging for GQ. :mad: Since I have some actual information, perhaps I can add it. A number of years ago I heard a lecture by Clifford M. Will “Was Einstein right”. He has also written a book on the subject, see the third item of the bibliography on http://en.wikipedia.org/wiki/Clifford_Martin_Will. Here’s a summary from memory of what he said. I don’t recall that he said anything about high brass, but he was on a committee to review the calculations involved in the GPS and the committee discovered that the engineers who designed it made no provision to account for general relativity, believing it to be a minor effect that did not need to be taken into account. So the committee evaluated that (along with other parts of the calculation) and discovered that even though the rest of it was right, failure to take relativity into effect would cause the readings to drift by something like 13 km per day! So relativity was built-in and the readings have been remarkably stable. He considered the latter to be important evidence that GR was correct.

As for when GPS became generally available, there were receivers by 1990. In fact, the army, I have read, had so few that they bought civilian models during Gulf War I. Originally the civilian models were accurate only to about 100 meters because there were secret built-in variations in the readings to prevent the enemy from using them with the same accuracy. This meant, among other things, that the civilian models the army bought were inaccurate. Eventually, some clever mathematicians tracked the inaccuracies over a long time and were able to learn the secret variations and design around them. Then Clinton ordered the no-longer secret variations to be published and that ended that. They are now accurate to about 10 meters, maybe a bit better.

I’m responding to the original OP scenario quoted below. Your scenario is entirely plausible and utterly dissimilar.The OP had the college educated brass with fairly high levels of technical acumen and experience in dealing with engineers, scientists and complex systems, effectively doubting that relativistic time effects even existed which is complete horseshit.

Did you read the cite above? That was from a professor of General Relativity who was extensively involved in the physics of GPS satellites:

Also according to someone in the QI thread on this, Prof Cox was also told this story by a member of the US military at the GPS facility in Colorado (this exchange is from an episode of BBC Horizon entitled “Do you know what time it is?”, which isn’t available online. So I can’t verify or give any details.)

There is huge world of difference between debating if an effect will have an operational impact vs whether the effect exists at all. The cite by the OP claims the debate was on the very existence of a relativistic effect, not it’s impact.

They didn’t just doubt the impact they’d have, they doubted whether they were “truths” that is exactly what Prof Cox claimed.

Now that I think about it, is there any other consumer product outside of GPS that needs to take into account the General Theory of Relativity? Or the Special Theory of Relativity, for that matter?

Good point, lots depend on the weirder affects of quantum physics. One of the cooler ones is the way modern airbag components are so small their design has to take into account Casimir force which is generated by virtual particles appearing out of nothing in the quantum gravity.

I can’t think of any that take into account relativity (except presumably other satellite communication devices).

The venerable “plugger” perhaps?

But the link apparently isn’t specific as to who “they” are in this case.

Hey, Colonial, what’s with the carriage returns? You’re wasting my screen space.