Name: Why Physics Can't Totally Explain the Universe's Expansion | SciShow News
Uploaded: 2020-03-30T03:41:31.000Z
Duration: 7 min 35 s
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Since the moment it began, the universe has been expanding.

It took humanity a while to figure that out,

but over the last century, astronomers have

You can either observe astrophysical objects,

or you can use the laws of physics to extrapolate

Both methods are great, but they also don't quite agree.

And according to a new set of measurements to be published

The two numbers might actually be different.

And to explain that we'd have to rethink our understanding of physics.

Right now, when we say that the universe is expanding,

the galaxies and other large objects is growing.

It's a technical thing, but strictly speaking, the universe isn't expanding everywhere.

Regardless, one of the tried and true methods

of measuring this expansion requires calculating

the distances to stars called Cepheid variables.

A Cepheid is a star whose brightness changes

And the length of that period is directly related to how bright the star is.

So as long as scientists can measure how fast

these objects change, they can figure out

Then, they can compare that number to how

bright the stars look from Earth to determine

Using sets of Cepheids at different distances,

along with data about other kinds of objects,

you can then figure out how fast the universe

There are a few other ways to measure this,

but Cepheid variables were especially important

In it, researchers used the Hubble Space Telescope

to look at 70 Cepheids in a nearby dwarf galaxy:

It's only about 162,000 light-years away, which is super duper close on a

Then, to make sure their brightness measurements

were as accurate as possible, the scientists

combined their data with results from a few

other sources, including an international

collaboration called the Araucaria Project.

This group calculated the distance to the Cloud a different way:

of binary star systems change as the stars

That movement allowed them to figure out stuff

And by combining that with data about how

fast those changes happened and what kind

of light the stars emitted, the scientists could ultimately work out how far away they

After looking at all this data, the authors of this new paper reported that the universe

is expanding at… drumroll please… about 74.03 kilometers per second per Megaparsec.

In other words, an object 1 million parsecs

away — or roughly 3.3 million light-years is

moving away from us at about 74 kilometers per second.

An object 2 million parsecs away is moving

away at about 148 kilometers per second, and

74.03 kilometers per second per Megaparsec

Now despite all the work that went into it,

that estimate isn't actually groundbreaking

at first glance, since it's basically in line with previous measurements.

And that's causing a problem, because that

estimate conflicts with other confident measurements

Like I mentioned earlier, Cepheid variables aren't the only way we can figure out how

This is the oldest light in the universe that humanity will ever see.

only about 380,000 years old, and studying it is

the main objective of the European Space Agency's

By studying temperature fluctuations in this light,

was expanding those 13-ish billion years ago.

Then, they've been able to use that to extrapolate

and figure out what the expansion rate should be today.

like, really well-tested laws of physics, so you