3804
- DARK ENERGY
- where dose it come from? DarkEnergy is the energy causing the
universe to expand at an ever increasing rate.
What could explain the crisis in cosmology?
--------- 3804 - DARK ENERGY - where dose it come from
- In 1916, Einstein finished his Theory of
General Relativity, which describes how gravitational forces alter the
curvature of spacetime. Among other things, this theory predicted that the
Universe is expanding, which was confirmed by the observations of Edwin Hubble
in 1929.
-
- Since then, astronomers have looked farther
into space and, back in time, to measure
how fast the Universe is expanding,
called the Hubble Constant rate of universe expansion. The rate is measured at 49,306 miles per hour
for every million lightyears of distsnce. The more space betwewen the faster
the rate of expansion of their separation.
-
- These measurements have become increasingly
accurate thanks to the discovery of the Cosmic Microwave Background (CMB) and
observatories like the Hubble Space Telescope.
-
- Astronomers have traditionally done this
measurement in two ways: directly measuring it locally (using variable stars
and supernovae) and indirectly based on redshift measurements of the CMB and
cosmological models.
-
- Unfortunately, these two methods have
produced different values over the past decade. As a result, astronomers have
been looking for a possible solution to this problem, known as the “Hubble
Tension.” The existence of “Early Dark
Energy” may be the solution cosmologists have been looking for.
-
- The direct method involves using supernovae
as “standard candles” (distance markers) to conduct measurements on the local
scale. The indirect method involves comparing measurements of the CMB with
cosmological models – like the Lambda Cold Dark Matter (LCMD) model, which
includes the presence of Dark Matter and Dark Energy.
-
- Unfortunately, these two methods produce
different results, the former yielding a value of 73 km/s per megaparsec (Mpc)
and the latter yielding 67 km/s Mpc. Mpc is a Megaparsec and it is a distance
of 3,262,000 lightyeasrs.
-
- The “Hubble constant” is the present rate
at which the Universe expands. The “Hubble tension” is a discrepancy in the
value you find for the Hubble constant when you either measure the expansion
rate as best you can at present or you predict the value it should have based
on the way the Universe looked after the Big Bang coupled with a model of how
the Universe should evolve. Its a problem because if these two ways do not
agree, it makes us think we are misunderstanding something about the Universe.
-
- The mystery of the Hubble Tension is not as
much of a problem as it is an opportunity for new discovery. So far, many
candidates have been offered to explain the discrepancy, ranging from the
existence of extra radiation, modified General Relativity (GR), Modified
Newtonian Dynamics (MOND), primordial magnetic fields, or the existence of Dark
Matter and Dark Energy during the early Universe that behaved in different
ways. These can generally be divided into two categories: early-time (shortly
after the Big Bang) and late-time solutions (more recently in cosmic history).
-
- What makes EDE preferable to late-time
solutions is how the latter implies the existence of a fluid that effectively
creates energy out of nothing – which violates the strong energy condition
predicted by GR. What’s more, such models are difficult to reconcile with the
Cosmic Distance Ladder measurements of Cepheid variables and Type Ia supernovae
in nearby galaxies (low-redshift targets) and Type Ia supernovae in distant
galaxies (high-redshift).
-
January 1,
2022 DARK ENERGY
- where dose it come from? 3804
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--- Sunday, January 1, 2023
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