1) Why is gravity so weird?
No force is more familiar than gravity — it’s what keeps our feet on the ground, after all. And Einstein’s theory of general relativity gives a mathematical formulation for gravity, describing it as a “warping” of space. But gravity is a trillion trillion trillion times weaker than the other three known forces (electromagnetism and the two kinds of nuclear forces that operate over tiny distances).
One possibility — speculative at this point — is that in addition to the three dimensions of space that we notice every day, there are hidden extra dimensions, perhaps “curled up” in a way that makes them impossible to detect. If these extra dimensions exist — and if gravity is able to “leak” into them — it could explain why gravity seems so weak to us.
“It could be that gravity is as strong as these other forces but that it gets rapidly diluted by spilling out into these other invisible dimensions,” says Whiteson. Some physicists hoped that experiments at the LHC would give a hint of these extra dimensions — but so far, no luck.
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Answer:
Why is gravity so weird?
No force is more familiar than gravity — it's what keeps our feet on the ground, after all. And Einstein's theory of general relativity gives a mathematical formulation for gravity, describing it as a “warping” of space
Answer:
If Isaac Newton suddenly popped out of a time machine, he’d be delighted to see how far physics had come. Things that were deeply mysterious a few centuries ago are now taught in freshman physics classes (the composition of stars is one good example).
Newton would be stunned to see enormous experiments like the Large Hadron Collider (LHC) in Switzerland — and possibly perturbed to learn that his theory of gravity had been superseded by one dreamed up by some fellow named Einstein. Quantum mechanics would probably strike him as bizarre, though today’s scientists feel the same way.But once he was up to speed, Newton would no doubt applaud what modern physics has achieved — from the discovery of the nature of light in the 19th Century to determining the structure of the atom in the 20th Century to last year’s discovery of gravitational waves. And yet physicists today are the first to admit they don’t have all the answers. “There are basic facts about the universe that we’re ignorant of,” says Dr. Daniel Whiteson, a University of California physicist and the co-author of the new book "We Have No Idea: A Guide to the Unknown Universe."
What follows is a brief tour through seven of the biggest unsolved problems in physics. (If you’re wondering why head-scratchers like dark matter and dark energy aren’t on the list, it’s because they were in our earlier story on the Five Biggest Questions about the Universe.)