THE EXPANDING UNIVERSE
Since ages man have wondered, what are the
dimensions of the universe and where does it end? If the universe is finite
then if one stuck at their hand at one edge where would it go? In 1929, Edwin Powell Hubble at Caltech discovered that
the universe is expanding. If the
universe has been static, then in accordance with Newton's law of motion of gravity the attractive
forces of all the objects within the universe should have caused the complete
collapse of the universe on itself. But in reality, it doesn't take place at
all, eventually keeping people with some paradox.
When Einstein discovered the speculation of gravity by the
Theory of relativity, his equations couldn't identify whether the universe was
expanding or collapsing. His original equation contained a term called the
cosmological constant which neglected the effect of gravity and the universe
was thought to be a static one. After Hubble's discovery, he realized that the
constant is actually wrong.
The theory of the expansion of the universe was developed by observing
the redshifts of celestial bodies which implied that the space between galaxies
is expanding, so they seem to recede from us at velocities that increase
with their distance. (Redshift means a rise within the wavelength of
electromagnetic radiations)
But what exactly means by the fact that the universe is
expanding?
It means every heavenly body i.e. galaxies are moving
aloof from one another. However, the galaxies don't seem to be moving through
space, they are moving in space because space is additionally moving. In other
words, the universe has no centre, everything is moving away from everything
else.
Recently, Astronomers have seen that the Hubble constant (a
value to detect how fast the cosmos is expanding with time) is 74 kilometres
(46 miles) per second per megaparsec. It means a galaxy which is 3.3 million
light-years aloof from us appears to be moving at a rate of 74 km faster
because of expansion of the universe which is 9% faster than the predicted 67
Km (41.6 miles) per second per megaparsec. It comes from Planck's observations
of the first universe, as well as our present understanding of the universe.
Several hypotheses are given to clarify this discrepancy.
Some said it will be the matter comprising 70% of the universe which will be
accountable for accelerated expansion. Another explanation is that the Universe
contains a new fundamental particle that travels close to the speed of light
(also called dark radiation) can be taken into account.
But actual explanation
remains a mystery. Adam Reiss,
laureate and lead researcher at Space Telescope Science Institute (STScI) and
Johns Hopkins University, Baltimore, Maryland said that "The Hubble
tension between the early and late universe may be the most exciting development in cosmology in
decades."
Written by
Written by
Debasmita Sharma Chaudhuri
BIOTECHNOLOGY 2ND
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