Oh hello!
I’m just popping by with some of the most recent exciting cosmological news: LIGO, already
a scientific superstar for being the first facility to successfully detect gravitational
waves...is getting a quantum upgrade!
That’s right--the facility that is already considered one of the most advanced pieces
of equipment on the planet is getting a roughly $35 million upgrade.
Projected to go into use around 2024, the enhancements to LIGO could double its already
impressive detection power.
We went into more detail about how LIGO works in another video of mine that we’ll link
at the end of this video, but basically: there are two LIGO facilities in two different states
in the US.
Each facility has two 4-kilometer-long arms, down which scientists bounce a laser, towards
a mirror at the other end.
Then when the light bounces back and the beams cross one another, the light waves should
cancel each other out.
But, if there’s an extremely subtle shift in the universe—and we’re talking EXTREMELY
subtle--like a gravitational wave—the two waves won’t cancel each other out.
The mirrors will have shifted enough that the light waves are out of sync in a way that
we can measure.
Based on the results that are recorded by the detector, scientists can then interpret
the data to see if the facility has detected a gravitational wave: a ripple in space time
caused by a huge astrophysical event like the collision of cosmological objects like
neutron stars and black holes.
Obviously a problem here is making sure the readings you’re detecting are really gravitational
waves, not just something like the natural vibration of the earth.
And while LIGO already has lots of successful measures in place to prevent the measurements
from being interfered with by things that are NOT gravitational waves, it could always
get better.
Additionally, some of the LIGO improvements are an effort to address the Heisenberg uncertainty
principle, or the idea that it’s impossible to exactly measure more than one aspect of
a phenomenon.
For example, any attempt to precisely measure the velocity of an electron will, according
to Heisenberg, disrupt its trajectory.
You couldn’t also measure the electron’s position and have it be unaffected by your
measurement of the velocity.
Basically, you can’t measure two things at once and have them both be accurate.
The principle, in principle, applies to everything, from your car to your molecules, but it’s
only really significant for things on microscopic or more often, subatomic scales.
This is relevant because the light beams that LIGO’s calculations rely on have two different
important aspects that both need to be measured in order to get a good reading.
Its phase, which is the light’s position at a given point in time, and its amplitude,
which can be defined as its intensity.
And because we’re trying to measure more than one aspect of these light beams, the
Heisenberg uncertainty principle can cause some additional murkiness around detections—making
it even more difficult to pick out gravitational waves from other, non-gravitational wave noise.
To solve this problem?
In the upgraded facility, LIGO will start using quantum ‘squeezed’ light.
This ‘frequency-dependent squeezing’ technique will hopefully minimize fluctuations in the
light’s phase, making the measurements of the light’s amplitude more accurate—minimizing
the effect of the Heisenberg uncertainty principle.
The upgrade also includes new mirrors with advanced coatings, specially designed to even
further reduce any extra noise caused by heat.
These improvements are what will take this history-making facility from LIGO to ALIGO+—the
Advanced Laser Interferometer Gravitational-Wave Observatory Plus.
The changes not only mean that scientists could catch a gravitational wave every day,
but could also be able to detect smaller events, events happening farther away in space, and
know way more about what the events were like!
Were the black holes spinning when they crashed into each other?
Burning questions we may soon actually get to know the answer to.
Ultimately, this means more concrete evidence in our search to uncover the mysteries of
extreme physics in space, which gives us more insight into the universe both as it is now,
and as it came to be.
Like we mentioned before, check out this video here on some drama on LIGO’s measuring techniques,
and make sure you come back to Seeker for all your gravitational wave updates--like
the LIGO facility in India that’s planned for 2025!
As always, thanks for watching and we’ll see you for the next one.