Something is seriously wrong with gravity, and nobody's quite sure why.
The problem is that gravity is too weak. Out of the four fundamental physical forces in the universe—gravity, electromagnetism, the strong force, and the weak force—gravity is by far the weakest. It's so weak that, for instance, a pair of tiny magnets can easily overcome the gravitational pull of the entire Earth.
There's no particular reason why gravity should be so much weaker than the other forces. Physicists have attempted to explain this discrepancy in a number of ways, from complex theories like string theory to philosophical ideas like the anthropic principle, which answers the question of why gravity isn't stronger by arguing that no one would be around to ask the question if it were.
But that's not enough for a group of physicists who have developed an alternative theory to explain gravity. Their theory involves decaying particles and the Higgs boson. The Higgs boson, discovered in 2012, is thought to be directly correlated to the strength of gravity. The more mass in the Higgs boson, the stronger gravity would be for all matter in the universe. So essentially, the question "Why is gravity so weak?" is the same as, "Why doesn't the Higgs boson have more mass?"
The new theory attempts to answer that question by arguing that after the Big Bang, a bunch of different Higgs bosons were created, each with a different mass. The Higgs bosons with large masses were unstable, so they decayed and broke apart into smaller Higgs bosons.
Over time, all the heavier Higgs bosons decayed into lighter and lighter versions, until only the lightest possible kind of Higgs boson was left. That extremely light Higgs boson is the one the LHC discovered in 2012.
The Cosmic Microwave Background as imaged by the WMAP mission. The image shows temperature differences in the early universe.
It's a pretty outlandish theory, but it's one that can actually be tested by studying the Cosmic Microwave Background. The CMB is a remnant of the Big Bang, light that is finally reaching us from some 13.8 billion years ago. By studying the CMB closely, scientists can discover clues about what happened in the early years of the universe and possibly determine whether this new theory about gravity is right.
Unfortunately, we will need to wait a few years for the next generation of telescopes—like the James Webb Space Telescope—to be launched before we find the answer. But until then, we can only wait and enjoy the very weak gravity that we've got.