3805
- FUNDAMENTAL CONSTANTS
- how many are there? Through a variety of tests on Earth and
throughout the universe, physicists have measured no changes in “time” or
“space” for any of the fundamental constants of nature.
--------- 3805
- FUNDAMENTAL CONSTANTS
- how many are there?
- How
fast the universe expands over time is a value called the Hubble constant. All
the steps involve building a strong "cosmic distance ladder," by
starting with measuring accurate distances to nearby galaxies and then moving
to galaxies farther and farther away. This ladder is a series of measurements
of different kinds of astronomical objects with an intrinsic brightness that
researchers can use to calculate distances.
-
- All of modern physics rests on two main
pillars:
-
-------------- One is Einstein's “theory of general
relativity”, which we use to explain the “force of gravity”.
-
-------------- The other is the “Standard Model”, which we
use to describe the other three forces of nature: electromagnetism, the strong
nuclear force and the weak nuclear force.
-
- But those theories do not fully explain
themselves. Appearing within the equations are fundamental constants, which are
numbers that we must measure independently and plug in by hand. Only with these
numbers in place can we use the theories to make new predictions.
-
- General relativity depends on only two
constants: the strength of gravity (G) and the cosmological constant. which
measures the amount of energy in the vacuum of space-time.
-
- The Standard Model requires 19 constants to
plug into the equations. These include parameters such as the masses of nine
fermions (like the electron and the up quark), the strengths of the nuclear forces,
and constants that control how the Higgs boson interacts with other particles.
Because the Standard Model does not automatically predict the masses of the
neutrinos, to include all their dynamics we have to add seven more constants.
-
- That's 28 numbers that completely determine
all the physics of the known universe.
Many physicists argue that having all these constants seems a little
artificial.
-
- Scientists are trying to explain as many
varied phenomena as possible with as few starting assumptions as we can get
away with. Physicists believe that general relativity and the Standard Model
are not the end of the story, however, especially since these two theories are
not compatible with each other. They suspect that there is some deeper, more
fundamental theory that unites these two branches.
-
- That more fundamental theory could have any
number of fundamental constants associated with it. It could have the same set
of 28 we see today. It could have its own, independent constants, with the 28
appearing as dynamic expressions of some underlying physics. It could even have
no constants at all, with the fundamental theory able to explain itself in its
entirety with nothing having to be added.
-
- No matter what, if our fundamental constants
aren't really constant, if they happen to vary across time or space, then that
would be a sign of physics beyond what we currently know. And by measuring
those variations, we could get some clues as to a more fundamental theory.
-
- One test involves ultraprecise atomic
clocks. The operation of an atomic clock depends on the strength of the
electromagnetic interaction, the mass of the electron, and the spin of the
proton. Comparing clocks at different locations or observing the same clock for
long periods of time can reveal if any of those constants change.
-
- Another ingenious test involves the Oklo
uranium mine in Gabon. Two billion years ago, the site acted as a natural
nuclear reactor that operated for a few million years. If any of the fundamental
constants were different back then, the products of that radioactive process,
which survive to the present day, would be different than expected.
-
- Looking at larger scales, astronomers have
studied the light emitted by quasars, which are ultraluminous objects powered
by black holes sitting billions of light-years away from us. The light from
those quasars had to travel those enormous distances to reach us, and they
passed through innumerable gas clouds that absorbed some of that light. If
fundamental constants were different throughout the universe, then that
absorption would be altered and quasars in one direction would look subtly
different from quasars in other directions.
-
- At the very largest scales, physicists can
use the Big Bang itself as a laboratory. They can use our knowledge of nuclear
physics to predict the abundance of hydrogen and helium produced in the first
dozen minutes of the Big Bang.
-
- And,
they can use plasma physics to predict the properties of the light emitted
when our universe cooled from a plasma to a neutral gas when it was 380,000
years old. If the fundamental constants were different long ago, then it would
show up as a mismatch between theory and observation.
-
- In these experiments and more, nobody has
ever observed any variation in these fundamental constants. We can't completely
rule it out, but we can place incredibly stringent limits on their possible
changes. For example, we know that the fine structure constant, which measures
the strength of the electromagnetic interaction, is the same throughout the
universe to 1 part per billion.
-
- While physicists continue to search for a
new theory to replace the Standard Model and general relativity, it appears
that the constants we know and love are here to stay.
-
January 1,
2022 FUNDAMENTAL CONSTANTS
- how many? 3804
----------------------------------------------------------------------------------------
----- Comments appreciated and Pass it on to
whomever is interested. ---
--- Some reviews are at: -------------- http://jdetrick.blogspot.com -----
-- email feedback, corrections, request for
copies or Index of all reviews
--- to:
------
jamesdetrick@comcast.net
------ “Jim Detrick” -----------
---------------------
--- Monday, January 2, 2023
---------------------------
-
No comments:
Post a Comment