neutron monitor
... that a neutron monitor can only directly detect neutrons, but is used to indirectly detect cosmic rays, high-energy charged subatomic particles impacting the Earth's atmosphere from outer space?
... that a <b id="mwBv0"><a href="./Neutron_monitor" id="mwBv4" rel="mw:WikiLink" title="Neutron monitor">neutron monitor</a></b> can only directly <a href="./Particle_detector" id="mwBv8" rel="mw:WikiLink" title="Particle detector">detect</a> <a class="mw-redirect" href="./Neutrons" id="mwBwA" rel="mw:WikiLink" title="Neutrons">neutrons</a>, but is used to indirectly detect <a href="./Cosmic_ray" id="mwBwE" rel="mw:WikiLink" title="Cosmic ray">cosmic rays</a>, high-energy <a href="./Charged_particle" id="mwBwI" rel="mw:WikiLink" title="Charged particle">charged</a> <a href="./Subatomic_particle" id="mwBwM" rel="mw:WikiLink" title="Subatomic particle">subatomic particles</a> impacting the <a class="mw-redirect" href="./Earth's_atmosphere" id="mwBwQ" rel="mw:WikiLink" title="Earth's atmosphere">Earth's atmosphere</a> from <a href="./Outer_space" id="mwBwU" rel="mw:WikiLink" title="Outer space">outer space</a>?