Name: X線を使ったひも理論の勉強法｜SciShow News (How to Study String Theory Using X-Rays | SciShow News)
Uploaded: 2021-01-14T10:28:11.000Z
Duration: 4 min 42 s
Description: VoiceTubeの動画で発音を聞きながら英語表現を覚えよう！学べる英語：

astronomers tend to study the biggest stuff in the universe,

while particle physicists study the smallest.

astronomers have done more and more research

on a certain prediction made by string theory

-- one of the most popular unproved ideas in all of physics.

And let's just say their results haven't been very encouraging.

after a new study from NASA's Chandra X-Ray Observatory,

which tried to find evidence for string theory using galaxy collisions.

But so far, things aren't looking promising.

This new study was published last month in

The Astrophysical Journal, and it has three key pieces.

And there's the family of hypothesized particles

String theory is one of the major candidates

for what's called a “Theory of Everything”:

a single framework that could predict the results of any experiment we could ever do.

Our best theories currently split the universe

into the big stuff that's governed by gravity,

and small stuff that's modeled by quantum mechanics.

Both models are great in their own domains,

if you try to study gravity on the tiniest scales,

any little bit of gravity should make more gravity around it.

So gravity should make more gravity, should make more gravity --

until you end up with an infinitely dense point where math doesn't work.

String theory supposes that all particles

are actually made of tiny, vibrating strings.

since those strings have a sort of length,

their interactions can never create a single, infinitely dense point.

Different theorists find different ways to go from this stringy foundation

so there are multiple versions of string theory out there.

But many of them require certain kinds of new, unobserved particles to work.

They're known as axion-like particles, or ALPs.

ALPs would be so light that they'd hardly ever bump into any other kind of matter,

which would explain why we've never seen one in an experiment.

But a lot of researchers still think they're out there,

because ALPs seem like the perfect missing pieces

to many puzzling aspects of the universe.

they could be why the universe has more matter than antimatter,

and they might even explain why time only ticks in one direction!

The good news is, human-run experiments aren't the only places to look.

ALPs should occasionally turn into photons,

or particles of light, as they travel through a magnetic field, and vice versa.

because space is full of light and magnetic fields.

So, if you looked at light after it went through one of these fields,

you could look for distortions created by ALP interference.

well, you'd provide the evidence physicists have been looking for.

Recently, this is exactly what a team of astronomers and cosmologists tried to do

They weren't the first to look for ALPs this way,

but their observations let them look more closely than anyone had before.

They used Chandra to look at light from a galaxy called NGC 1275.

and it's a galaxy that eats other galaxies.

Collisions like that release tons of X-rays,

and we can use models to predict what those rays should look like

in an ALP-free universe as they escape the galaxies' magnetic fields.

In their study, the team compared what they saw from NGC 1275 with a range of ALP models

Some say ALPs should interact with light a lot; others say it should be pretty rare.

The light from the galaxy looked exactly like we'd expect.

The team saw no evidence of ALPs in their data.

but the fact that even a super-sensitive telescope like Chandra couldn't find them

does effectively eliminate a big range of possible models.

Maybe an even more advanced telescope could change things in the future.

But again, this Chandra study isn't the only one of its kind.

astronomical teams around the world have looked for evidence of ALPs in their data,

There are still models out there that fit everyone's observations,

making some scientists increasingly skeptical about ALPs

and some of the string theories that predict them.

So axion-like particles might still exist.