So. I am posting this in Research Forum because I am not fully aware of the information. So, you guys can post your views below easily. Let us begin.
Everything you probably think of when you think of the universe—planets, stars, galaxies, black holes, dust—makes up just 4 percent of whatever is out there. The rest comes in two flavors of “dark,” or unknown stuff: dark matter, at 23 percent of the universe, and dark energy, at a whopping 73 percent:
Scientists have some ideas about what dark matter might be—exotic and still hypothetical particles—but they have hardly a clue about dark energy. … University of Chicago cosmologist Michael S. Turner ranks dark energy as “the most profound mystery in all of science.”
The effort to solve it has mobilized a generation of astronomers in a rethinking of physics and cosmology to rival and perhaps surpass the revolution Galileo inaugurated on an autumn evening in Padua. … Dark energy has inspired us to ask, as if for the first time: What is this cosmos we call home?
But astronomers do know that, thanks to these dark parts, the universe is expanding. And not only expanding, but expanding faster and faster. Ultimately, everything in the universe will drift farther and farther apart until the universe is uniformly cold and desolate. The world will end in a whimper.
Cosmos started from a singularity, and started expanding like a 'wave' when one throws a pebble in a pond. The expansion comes to an 'end point' and will start retracting back to the singularity. It starts all over again. No one can tell when this cycle started and when will it end!