# Why is "quantum gravity" such a problem?

**URL:** <https://boards.straightdope.com/t/why-is-quantum-gravity-such-a-problem/132190>\
**Category:** Factual Questions\
**Created:** [October 14, 2002, 4:32am UTC](https://boards.straightdope.com/t/why-is-quantum-gravity-such-a-problem/132190 "2002-10-14T04:32:49Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Muad\_Dib](https://avatars.discourse-cdn.com/v4/letter/m/35a633/32.png) [@Muad\_Dib](https://boards.straightdope.com/u/Muad_Dib)\
**Post date:** [October 14, 2002, 4:32am UTC](https://boards.straightdope.com/t/why-is-quantum-gravity-such-a-problem/132190/1 "2002-10-14T04:32:49Z")

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Why? Why not assume that gravity acts exactly the same “down there” as it does “up here”? Is there some direct evidence that things aren’t working the same (gravity-wise) at subatomic levels?

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**Author:** ![ultrafilter](https://avatars.discourse-cdn.com/v4/letter/u/3d9bf3/32.png) [@ultrafilter](https://boards.straightdope.com/u/ultrafilter)\
**Post date:** [October 14, 2002, 4:34am UTC](https://boards.straightdope.com/t/why-is-quantum-gravity-such-a-problem/132190/2 "2002-10-14T04:34:19Z")

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Gravity is so weak compared to the other fources (electroweak and strong) that its effects can’t be measured on anything the mass of a particle.

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**Author:** ![JS\_Princeton](https://avatars.discourse-cdn.com/v4/letter/j/57b2e6/32.png) [@JS\_Princeton](https://boards.straightdope.com/u/JS_Princeton)\
**Post date:** [October 14, 2002, 4:46am UTC](https://boards.straightdope.com/t/why-is-quantum-gravity-such-a-problem/132190/3 "2002-10-14T04:46:37Z")

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One of the hints that things are going wrong is that when we try to calculate the vacuum energy density scales from the unification of quantum mechanics and gravity we get theoretical answers that are off by dozens of orders of magnitude from the observed results.