# Would massless quarks still combine into protons and neutrons? **URL:** \ **Category:** Factual Questions\ **Created:** [July 6, 2013, 1:35pm UTC](https://boards.straightdope.com/t/would-massless-quarks-still-combine-into-protons-and-neutrons/662787 "2013-07-06T13:35:39Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![ZenBeam](https://avatars.discourse-cdn.com/v4/letter/z/3ab097/32.png) [@ZenBeam](https://boards.straightdope.com/u/ZenBeam)\ **Post date:** [July 6, 2013, 1:35pm UTC](https://boards.straightdope.com/t/would-massless-quarks-still-combine-into-protons-and-neutrons/662787/1 "2013-07-06T13:35:39Z")
The discussion in the _What Are Sub-Atomic paricles composed Of?_ thread reminded me of a question I’ve been pondering. **deltasigma** gave a link to a [recent article](http://www.fnal.gov/pub/today/archive/archive_2013/today13-07-05.html) with the quote > [@](#): > > Things get really interesting when we ask where the nucleons’ mass comes from. Each nucleon consists of three quarks, so the obvious answer is that each of the quarks carries about a third of the mass of a proton. However, that’s not true. The mass of the quarks is only about 1 to 2 percent the mass of the proton. So where does the mass of the proton come from? Energy. What if the quarks _were_ massless? Say only the Up and Down, or even maybe only the Up quark was massless. Would they still combine to form protons and neutrons, or would their being massless prevent them from doing so? Would they simply have a slightly lower mass, or would they have very different properties? If they’d be very different, would that difference only occur if they were truly massless, or would there be big differences if they had a tiny mass, maybe similar to neutrinos? ---
**Author:** ![OldGuy](https://avatars.discourse-cdn.com/v4/letter/o/3bc359/32.png) [@OldGuy](https://boards.straightdope.com/u/OldGuy)\ **Post date:** [July 6, 2013, 2:40pm UTC](https://boards.straightdope.com/t/would-massless-quarks-still-combine-into-protons-and-neutrons/662787/2 "2013-07-06T14:40:23Z")
If they were massless they’d have to move at the speed of light in all reference frames. If just the ups were massless and the downs weren’t, I don’t see how they could make a meaningful combination since they’d have to be separating at the speed of light. ---
**Author:** ![ZenBeam](https://avatars.discourse-cdn.com/v4/letter/z/3ab097/32.png) [@ZenBeam](https://boards.straightdope.com/u/ZenBeam)\ **Post date:** [July 6, 2013, 5:30pm UTC](https://boards.straightdope.com/t/would-massless-quarks-still-combine-into-protons-and-neutrons/662787/3 "2013-07-06T17:30:59Z")
> [@OldGuy](#): > > If they were massless they’d have to move at the speed of light in all reference frames. If just the ups were massless and the downs weren’t, I don’t see how they could make a meaningful combination since they’d have to be separating at the speed of light. They wouldn’t have to move at the speed of light _in a straight line_. They could move in circles, for example. Gluons are massless, and stay confined in the proton and neutron. But maybe they need the Up and Down as anchors. ---
**Author:** ![Half\_Man\_Half\_Wit](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/half_man_half_wit/32/21766_2.png) [@Half\_Man\_Half\_Wit](https://boards.straightdope.com/u/Half_Man_Half_Wit)\ **Post date:** [July 6, 2013, 5:44pm UTC](https://boards.straightdope.com/t/would-massless-quarks-still-combine-into-protons-and-neutrons/662787/4 "2013-07-06T17:44:51Z")
Frank Wilczek considers the case of a ‘QCD Lite’ with three massless quarks (u, d, s), and three quarks of infinite mass (c, t, b) in his article on [\*The Origins of Mass \*](http://arxiv.org/abs/1206.7114). It’s not too different from our everyday world, IIRC (and there are massive protons and neutrons). ---
**Author:** ![Pasta](https://avatars.discourse-cdn.com/v4/letter/p/ecccb3/32.png) [@Pasta](https://boards.straightdope.com/u/Pasta)\ **Post date:** [July 7, 2013, 1:51am UTC](https://boards.straightdope.com/t/would-massless-quarks-still-combine-into-protons-and-neutrons/662787/5 "2013-07-07T01:51:01Z")
> [@ZenBeam](#): > > Gluons are massless, and stay confined in the proton and neutron. But maybe they need the Up and Down as anchors. See [glueballs](http://en.wikipedia.org/wiki/Glueball).