[MUSIC] In February 2016, the final major prediction
put forth by Einstein’s theory of general relativity was confirmed, more than 100 years
after he initially proposed it, proving yet again: The greatest physicist, of ALL time,
is JOHN CE-- No. Just no.
It’s Albert Einstein [OPEN] Let’s face it, in the world of physics,
Einstein is like Beyonce, Kanye, and Taylor Swift all rolled into one, and a touch of
Lady Gaga in the hair. He's famous, but he's got the skills to back it up.
By age 26, Einstein had already completely changed physics, but who would be satisfied
with that? He still wanted to integrate gravity into
his theory of relativity. Einstein’s idol Isaac Newton had claimed
gravity was mediated by an attractive force between two bodies, and that an object that
feels no force will either remain motionless or move in one direction at a constant speed. But this way of looking at things really bugged
Einstein, so he did what bored patent clerks do and daydreamed his way into the history
books… Einstein imagined himself falling from a great
height in a sealed container. Everything inside would be weightless, floating around him, but there’s no way he’d be able to distinguish this from floating in deep space, far from a massive object like Earth. Now, suppose that sealed container is accelerating
through space at 9.8 meters per second squared, There’s no experiment we can do to distinguish
this from the feeling of standing on Earth’s surface. If we drop an apple, we can’t tell
if it is accelerating towards the ground, or if the ground is accelerating toward the
apple. This means acceleration from gravity and acceleration from any other force are
indistinguishable. Or to put it another way, gravity isn’t a force at all, but a result of our surroundings accelerating *relative* to us. Einstein’s theory of general relativity
joined these two ideas into one. Rather than gravity being a special force between two
bodies, massive things warp spacetime, like dimples in a fabric, and falling objects are
simply moving in straight lines around these curves. Of course, a beautiful theory’s just a beautiful
theory if it can’t make observable predictions. But for the past 100 years, physicists have
been putting Einstein to the test The first test was the gravitational effects of massive objects at close distances. People
had known for a long time that the long axis of Mercury’s elliptical orbit rotates around
the sun over time, called precession. But new measurements of this rotation made in
the late 19th century were off by 43 arcseconds per century from what Newton’s physics predicted.
This is just a few thousandths of a degree, but it’s still something. When Einstein
applied his spacetime curvature, the numbers lined up. Einstein’s next prediction was that massive objects should bend passing light, and scientists
were able to test this just a few years later in the form of a solar eclipse. If Einstein’s
relativity was correct, then stars visible near the edge of the eclipsed sun should appear
in different positions from when they were viewed away from the sun. Newtonian gravity
also predicts that light can be bent by a gravitational field, but it’s based on some
bad assumptions, and gives a number just half the size of Einstein’s prediction.
Astronomer Arthur Eddington sent teams to Brazil and west Africa to observe the event,
and their data confirmed Einstein’s model over Newton’s. This resulted in what might
be the greatest scientific newspaper headline of all time, and made Einstein a global celebrity. We’ve talked about the effects of Einstein’s *special* relativity on time and distance
before, but general relativity has its own effects on how clocks tick.
Let’s say two observers each have a photon clock. Instead of ticking seconds, these clocks
tick when a photon bounces between two mirrors. Without any other factors, each observer should
see the other’s clock “ticking” at the same rate as their own, but if we accelerate
one clock upward, it ticks more slowly because the top mirror is moving away from the rising
photon. Now remember, Einstein’s equivalence principle
says we can’t distinguish an accelerating frame from a gravitational field, so clocks
tick more slowly, time passes slower in stronger gravitational fields.
We don’t have to go near something like a black hole to see this at work. Clocks aboard
our GPS satellites, far away from Earth, have to correct for this effect when beaming time
information to our devices. A clock on Mount Everest, if it had been ticking
there for the entire history of Earth, would be 39 hours ahead of a clock at sea level.
A clock on your head would even tick ever so slightly faster than a clock at your feet. Perhaps the wildest prediction of general
relativity was that massive objects could create waves in spacetime itself. We’re
talking huge things –spinning pairs of neutron stars or colliding black holes. As these waves
traveled across the universe, they’d pass right through Earth, squishing and pulling
us like Jell-o. But these ripples are tiny and had remained undetectable… until now.
Last year, the LIGO Observatory detected a passing G wave using
tiny fluctuations in laser light beams, and in February 2016, scientists confirmed these
spacetime ripples had been directly observed for the first time ever.
The waves originated 1.3 billion years ago, far outside our own galaxy, from the collision
of two black holes, and were detected here a century after Einstein made his prediction.
If you want to dig deeper into how these gravitational waves are formed, and how LIGO detected them,
check out these two videos from our friends at PBS Space Time, they are really great. Gravitational waves let us see a totally new
spectrum of physics beyond electromagnetic radiation, letting us study the most massive
objects in the universe through completely new eyes. With this new discovery, and the final confirmation
of general relativity’s predictions, Einstein cements his place as THE spacetime lord. Stay Curious.
Got me
fuck you
Funniest part is its part of the video. Not an edit.
I also subscribe to /r/mealtimevideos so this was just a reflex click. Got me good.