In thermodynamic terms, she explains, the Universe will approach a state of minimum temperature and maximum entropy. The third demise that Mack discusses is the Big Rip. This is in store if dark energy accelerates expansion even more than is currently expected.
The remaining stars and planets will explode. Finally, the last atoms will be ripped apart. The final doomsday scenario that Mack describes is extremely unlikely: vacuum decay. That might happen if, say, a black hole evaporates in just the wrong way. Such a bubble would expand at the speed of light, destroying everything, until it cancels the universe.
Vacuum decay might already have begun in some distant place. Not to worry, though. News 09 NOV Research Highlight 05 NOV News 04 NOV To understand this horrifying scenario, we first have to go through two of the fundamental principles of the Universe, the first being energy levels. Basically, everything in existence has an energy level. Wood, for example, has a relatively high energy level, and this allows it to be burned to release a lot of heat energy. Space on the whole gets darker, emptier, and colder, and the lack of interactions starves galaxies of their supply of fuel for new stars.
Stars die, matter decays, and eventually the cosmos is devoid of all structure, with only trace amounts of radiation wandering aimlessly through the void. The standard explanation of dark energy is a cosmological constant — an idea Einstein first proposed in as an added term in his equations of gravity to explain why the universe appeared to be static instead of collapsing upon itself.
When expansion was discovered soon after, the cosmological constant term was thrown out, only to be dragged out again decades later as a possible culprit for accelerated expansion. It represents vacuum energy — a kind of minimum energy inherent to empty space, one whose density stays constant no matter how much the universe expands — but its magnitude is all wrong.
Read more: Cosmological constant may not be constant. The best theoretical calculations we can do from particle physics theories suggest vacuum energy should be at least orders of magnitude stronger. But if cosmological constant were strong enough to make the whole theoretical story fit together, it would do more than slowly isolate galaxies over time.
It would violently rip apart all structure in the universe. Similarly, Andreassen said, it's possible that a bubble has already formed and is hurtling toward us at the speed of light right now.
There's comfort in knowing how everything ends, but Vincenzo Branchina, a physics professor and researcher at the University of Catania in Italy who was not involved in the study, said not to start crying over sour milk just yet. Branchina said the Harvard team only accounted for the standard model of physics and not all the new and confusing branches, like quantum gravity and dark matter, that are still completely mysterious. In order for the universe to be consumed in an expanding ball of chaos, dark matter , a mysterious form of matter that exerts a gravitational pull but emits no light, cannot interfere.
Which is unlikely, since it might comprise 80 percent of our universe.
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