this to test general relativity?”

Hi everyone, Julian here for DNews. I know we've been doing it for a while now, but

launching stuff into space is still pretty tricky. You've got to get a giant rocket

on a launchpad without it exploding. You've got to start it up without it exploding. You've

got to send it into space. Without it exploding.

But assuming the payload still stays intact, sometimes the rocket puts it in the wrong

place. that's what happened in August of 2014 with a Russian Soyuz-Fregat rocket carrying

two of the European Space Agency's Galileo satellites. The rocket worked flawlessly most

of the way up there, and then in the last stage it pointed in the wrong direction and

shot them off at an orbit that made them useless for their intended purpose. Ah, so close.

Of course we're talking close by space standards. Which is just another way of saying the orbits

were really far off. They were supposed to be in circular orbits a constant 23,222 km

(14429 miles) away from the earth. Instead they were set on elliptical orbits, twice

a day they were 2,000 km (1242 miles) too high, and twice a day they were 10,000 km

(6213 miles) too low.

The Galileo program is going to be fine. The plan is to launch 30 satellites to use them

for global positioning, and really 24 of them are needed for the system to be fully operational,

while the remaining 6 are there for backup. So two of them whizzing about in the wrong

place is a minor setback, rather than a dealbreaker.

But, heck, while they're up there, we may as well do something with them. They've

still got fully functioning atomic clocks onboard, so what experiments could you do

with a spacecraft traveling in an elliptical orbit around a massive object while carrying

a super-accurate clock?

If you said test time dilation, you must watch this show a lot. Hi mom!

Yes as you're probably aware, according to Albert Einstein's theory of general relativity,

near massive objects, time moves slower. GPS satellites already have to constantly adjust

their atomic clocks back slightly because of their distance from the Earth. And yes,

according to special relativity their speed also means that their clocks should run a

little slower, but the overall effect is the super accurate clocks in space are a little

fast on the order of microseconds.

The wayward Galileo satellites have had some course corrections because they have thrusters

and a bit of hydrazine fuel. Now their orbits change by 8,500 km (5,281 miles) twice a day

instead of 12,000, but that's still a difference greater than the radius of the Earth (6,371

km) and then some. So what that means is compared to our atomic clocks down here, the misplaced

Galileo clocks with run a little faster, then a lot faster, then a little faster, then a

lot faster as they gets closer and farther away from this massive hunk. I mean the earth,

not me.

Using those differences, we'll be able to check Einstein's math. Sure we did it once

before with an atomic clock in 1976 that hitched a ride 10,000 km into space, but that experiment

only lasted a few hours. We can pull data from these satellites for over a year and

be four times more accurate than before. We'll be able to test the math vs the measurements

to an accuracy of 0.004%. And we'll be able to do it thanks to a mistake that we turned

into a happy little accident.

And I've got more good news, everybody!

TestTube now has a newsletter!

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So I glossed over how GPS satellites work, and though I'd love to ramble all about

them, Trace's clock was a little faster than mine and he beat me to it. Check out

the amazing science behind knowing where on Earth you are right here.

Have you

ever turned an almost fail into an epic win?

Sure you have, so let us know in the comments, subscribe for more, and I'll see you next

time on DNews.