- 4228 - UNIVERSE - expanding but how fast? One of the great unsolved mysteries of cosmology is “Universe Expansion Rate”, known as the “Hubble tension”. It stems from our inability to pin down the precise rate of cosmic expansion.
--------------------- 4228 - UNIVERSE - expanding but how fast?
- There are several
ways to calculate this rate of expansion, from observing distant supernovae to
measuring the Doppler shift of maser light near supermassive black holes. They all give slightly different
results. Why?
-
- Maybe we don’t
fully understand the structure of the Universe, or maybe our view of the
heavens is biased given that we are located deep within a galactic
supercluster.
-
- If we were
floating deep in space, far away from any galaxies, then our view of cosmic
expansion would be free of gravitational influences and we could better see how
distant galaxies move away from us. Since we are part of a local cluster of
galaxies, we have a bit of bias in our data. This is why many local galaxies
are blue-shifted and not red-shifted?
-
- The Universe isn’t
contracting near us, we’re just in a galactic gravitational well. We can easily
account for this bias, so it isn’t a problem. However, given the Hubble
tension, we need to look for gravitational biases beyond the local group,
hoping it would solve the issue.
-
- Astronomers looked
at the largest gravitational structure we’re a part of, known as the “Laniakea
Supercluster.” It is a massive cluster
of galaxies more than 520 million light-years across, containing more than
100,000 galaxies, including the Milky Way. Our local group is being pulled
toward the heart of Laniakea, and thus
our motion through the Universe could skew our observations of cosmic
expansion.
-
- These observations
show a statistical bias in the data.
When the team measured the gravitational influence of the supercluster
as a whole, they found it does bias our observations by about 2% – 3%. But it’s
biased in the wrong direction.
-
- In other words,
by not taking the effect of Laniakea into account, the Hubble tension seemed
smaller than it actually is. These new results show that the tension is 2% – 3%
greater than we thought. Even some of the more recent Hubble constant
measurements that seemed encouraging aren’t enough to account for the “Laniakea
bias”.
-
- Removing subtle
biases from our cosmological data is challenging, so it is possible that
further observations may swing the results back in the right direction. But we
can’t rely on bias alone to solve this mystery. Clearly, something subtle and
strange is going on, and the solution isn’t obvious. It will take a great deal
more study to understand Hubble’s tension.
-
- It stems from our
inability to pin down the precise rate of cosmic expansion. There are several
ways to calculate this expansion, from observing distant supernovae to
measuring the Doppler shift of maser light near supermassive black holes, and
they all give slightly different results.
-
- Maybe we don’t
fully understand the structure of the Universe, or maybe our view of the
heavens is biased given that we are located deep within a galactic
supercluster.
-
- If we were
floating deep in space, far away from any galaxies, then our view of cosmic
expansion would be free of gravitational influences and we could better see how
distant galaxies move away from us. Since we are part of a local cluster of
galaxies, we have a bit of bias in our data.
-
- This is why many
local galaxies are blue-shifted. The Universe isn’t contracting near us, we’re
just in a galactic gravitational well. We can easily account for this bias, so
it isn’t a problem. However, given the Hubble tension, a team recently looked
for gravitational biases beyond the local group, hoping it would solve the
issue.
-
- Removing subtle
biases from our cosmological data is challenging, so it is possible that
further observations may swing the results back in the right direction. But we
can’t rely on bias alone to solve this mystery. Clearly, something subtle and
strange is going on, and the solution isn’t obvious. It will take a great deal
more study to understand Hubble’s tension.
-
-
November 19, 2023
UNIVERSE - expanding but how fast? 4228
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Sunday, November 19, 2023 ---------------------------------
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