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# Physics/Gravity

Question
QUESTION: How gravity acts on mass particles and mass-less particles?

Whether Photons having mass or not?

ANSWER: Gravitation acts on massive particles due to their interaction with space itself (what gives them mass, currently believed to be through the Higgs boson).  Massless particles travel only in straight lines, but gravitation curves what is a straight line in space slightly (or extremely for very strong gravitation like that from black holes).  Photons have no mass.  Further detail really requires you to go take a course or at least study a book on general relativity.  It's a complex subject.

---------- FOLLOW-UP ----------

QUESTION: Then how light  rays become bend near by large massive objects gravity?

because photons having no mass.

I told you, they don't really bend.  Space bends, and a straight line through bent space (like a straight line on paper with a wrinkle or a fold in it) is bent.  So light follows a straight line through space, but space itself is bent.  So we see the light as bent, but it doesn't really bend.

Physics

Volunteer

#### Dr. Stephen O. Nelson

##### Expertise

I can answer most basic physics questions, physics questions about science fiction and everyday observations of physics, etc. I'm also usually good for science fair advice (I'm the regional science fair director). I do not answer homework problems. I will occasionally point out where a homework solution went wrong, though. I'm usually good at explaining odd observations that seem counterintuitive, energy science, nuclear physics, nuclear astrophysics, and alternative theories of physics are my specialties.

##### Experience

I was a physics professor at the University of Texas of the Permian Basin, research in nuclear technology and nuclear astrophysics. My travelling science show saw over 20,000 students of all ages. I taught physics, nuclear chemistry, radiation safety, vacuum technology, and answer tons of questions as I tour schools encouraging students to consider careers in science. I moved on to a non-academic job with more research just recently.

Education/Credentials
Ph. D. from Duke University in physics, research in nuclear astrophysics reactions, gamma-ray astronomy technology, and advanced nuclear reactors.