Tag Archives: Einstein

It’s time for Einstein’s General Theory of Relativity!

It seems Time and Space aren’t two separate things after all. They’re 2 parts of one thing: TimeSpace. They’re what’s called a continuum.
(kon-TIN-you-uhm)
1 : a coherent whole characterized as a collection, sequence, or progression of values or elements varying by minute degrees
https://www.merriam-webster.com/dictionary/continuum

The Sweet-Salty continuum

I suppose a piano keyboard could be considered a continuum: lowest note on one end and highest note on the other, with the keys in between playing both low and high. You could draw up a continuum of food—from, say, the sweetest food you ever ate to the saltiest food you ever ate. Where is barbecue—both sweet and salty—on your continuum?

The continuum of TimeSpace has extreme ends, too—one end nothing but time and the other end nothing but space. This is really hard to think about. Time passes on one end but nothing physical is there. There’s physical stuff on the other end but nothing moves because it’s outside the medium of time. We live in the middle. We’re physical beings in a physical world who walk around and grow older and have kids and live our lives while plants sprout, bloom and die and the planets and stars whirl around in space.

(Does any of this remind you of Sunday-school? I mean how the Bible starts: “In the beginning…” and then God creates the universe, the Earth and the heavens, separates day from night. It’s how the Bible explains time and space. Which means God exists outside the TimeSpace continuum, which is too much for my brain to handle.)

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Physicists disagree

physicists

Getting back to our satellites—traveling around Earth at 17,000 miles per hour, a satellite’s time slows down, according to Einstein. Also according to Einstein, since gravity is weaker up where the satellites are, time moves a little faster. If that’s the case, wouldn’t a satellite’s GPS signal be inaccurate?

As I researched this question online, I got 2 answers to it: yes and no.

Yes. The satellites’ times slow down, but those amazing scientists who put the satellites up there in the first place cleverly adjusted their signals to compensate for it. Each satellite carries an atomic clock and sends a time & location signal at the speed of light, slightly adjusted (through programmed computer chips) for Einstein’s Special Theory. The clock takes into consideration both the slowing down because of speed and the speeding up because of weak gravity.
https://www.physicscentral.com/explore/writers/will.cfm

https://physicstoday.scitation.org/doi/abs/10.1063/1.1485583?journalCode=pto

No. The satellites’ times slow down, but since they’re all zooming along at 17,000 miles per hour, all their times will be slowed down by the same ratio. So, it doesn’t matter. If all the satellites’ times agree with each other, the GPS system will be accurate. Or, the slowing down is cancelled out by the speeding up caused by weak gravity, so it’s what they call a ‘wash.’ Or, Einstein’s theories are a bunch of baloney so we shouldn’t pay any attention to them.
http://www.alternativephysics.org/book/GPSmythology.htm
View at Medium.com

Um. I don’t know what to say here, gang. As you must be aware, I’m just some shmo who is learning as I write this. If you put me on the spot for which is the right answer, I’m going with the bloggers who have better proofreading/grammar skills and citations. If any of my loyal readers want to chime in, please do!

UPDATE: Regarding a satellite’s time difference because of relativity, our indefatigable physics consultant, Ms Physics, says:

Infinitesimal difference, yet a difference. You need to approach the speed of light 3.0 x 10^8 m/s (670,616,629 mph) to have a significant difference. Any way John you remember the precision of the Cesium clock, these differences would really become significant in GPSA calculation using General Relativity predicts that the clocks in each GPS satellite should get ahead of ground-based clocks by 45 microseconds per day.

A microsecond is one-millionth of a second. https://www.simetric.co.uk/si_time.htm

This is why I stick to drawing pictures and let others do the heavy brain-work.

I borrowed parts of this composition for my sketch. I removed the horses and put everybody in lab coats.

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Einstein’s Special Theory of Relativity


As you move faster, time slows down for you. Even though that’s true when you’re riding in a car, the slowdown is so teeny-tiny that it’s not worth measuring. But, if you were to travel to another galaxy at almost the speed of light, time would slow down—for you—to the point where you would age more slowly than your pals back on Earth.

When you got back from your trip, your friends would be old and wrinkly but you’d be ready to graduate from high school.

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Classical Relativity

Believe it or not, we’re coming to the end of The Western Civ User’s Guide to Time & Space. I would be cheating you customers if I didn’t spend a little time talking about TimeSpace.

The name Einstein has come to be shorthand for genius. It’s still difficult to imagine the abstract way he trained his brain to think about time and space. Back in 1905, Albert Einstein published his theories about Relativity. He had 2 theories, a Special and a General Theory. But first, let’s talk about Classical Relativity.

Classical Relativity: everything moves relative to everything else.

If you’re riding in a train going 45 miles per hour and throw a ball from the back of the car to the front, the ball seems to you to travel at 10 mph. To a cow standing in a field watching you throw the ball, the ball is traveling at 55 mph: 45 mph for the train plus 10 mph for the ball.

A speedometer can say we’re driving an automobile at 45 miles per hour, but that 45 mph is the car’s speed relative to the surface of good ol’ Planet Earth. Earth is also spinning around and circling the Sun. The Sun also circles around in the Milky Way, taking us along with him. The Milky Way circles around in the Universe. Even the Universe is moving—it’s expanding. How fast something is moving can only truly be measured as it relates to something else. That’s Classical Relativity.

I once tried talking my way out of a speeding ticket using this concept but the trooper wasn’t buying it. Just kidding! Actually, I started sobbing uncontrollably and he walked away in disgust.

UPDATE: My pal Ross sent this interesting article about how a fighter jet ran into its own bullets (the jet landed safely). It seems air-friction slowed the bullets but the jet’s engines allowed it to speed up. At any rate, probably I should redraw the above cartoon with the kid inside a box car, instead of standing on a flat car. https://arstechnica.com/tech-policy/2019/04/dutch-f-16-takes-cannon-fire-from-itself/?fbclid=IwAR1aIR4z2buoa-58GgXSQGUIlqAji6qFpE0MsXSAqC2gYGi6kUBg4UBYYLg

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Einstein

So atomic clocks saved the day—yay! Satellites are synchronized with each other to nanosecond accuracy. Their signals let our GPSs figure out where we are because even though those satellites are hurtling through space at 17,000 miles per hour, their atomic clocks will always show the correct time, right? Nothing’s gonna interfere with each satellite’s time, nothing! No sir! Not one thing!

Okay, maybe one thing: Einstein.

I can see you loyal-yet-exasperated readers flinging your half-eaten peanut-butter-and-jelly sandwiches across the room and yelling, “Oh, come off it, Manders! Have you finally gone around the bend? Should we have you fitted for a straight-jacket and a drool-cup? What’s Einstein got to do with my global positioning system?”

Listen, and I will tell you all about it.